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Sample records for 4v eli alloy

  1. Notch effects on high-cycle fatigue properties of Ti 6Al 4V ELI alloy at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Yuri, T.; Ono, Y.; Ogata, T.

    2006-01-01

    Notch effects on the high-cycle fatigue properties of the forged Ti-6Al-4V ELI alloy at cryogenic temperatures were investigated. Also, the high-cycle fatigue data were compared with the rolled Ti-5Al-2.5Sn ELI alloy. The one million cycles fatigue strength (FS) of the smooth specimen for the forged Ti-6Al-4V ELI alloy increased with a decrease of test temperature. However, the FS of each notched specimen at 4 K were lower than those at 77 K. On the other hand, the FS of the smooth and the notched specimens for the forged Ti-6Al-4V ELI alloy at 4 K were lower than those for the rolled Ti-5Al-2.5Sn ELI alloy. This is considered to be the early initiation of the fatigue crack in the forged Ti-6Al-4V ELI alloy compares with the forged Ti-5Al-2.5Sn ELI.

  2. Tensile properties of cast titanium alloys: Titanium-6Al-4V ELI and Titanium-5Al-2.5Sn ELI

    NASA Technical Reports Server (NTRS)

    Billinghurst, E. E., Jr.

    1992-01-01

    This work was performed to determine the tensile properties of cast, hot isostatic pressed (HIP'ed), and annealed titanium alloys, Ti-6Al-4V ELI and Ti-5Al-2.5Sn ELI, that are candidate materials for the space transportation main engine (STME) liquid hydrogen turbopump impeller. Samples of the cast alloys were HIP'ed, annealed, and machined into tensile specimens. The specimens were tested in air at ambient temperature (70 F) and also at -423 F in liquid hydrogen. The Ti-6Al-4V alloy had an average ultimate strength of 129.1 ksi at 70 F and 212.2 ksi at -423 F. The Ti-5Al-2.5Sn alloy had an average ultimate strength of 108.4 ksi at 70 degrees F and 185.0 ksi at -423 F. The ductility, as measured by reduction of area, for the Ti-6Al-4V averaged 15.2 percent at 70 F and 8.7 percent at -423 F, whereas for the Ti-5Al-2.5Sn alloy average reduction of area was 24.6 percent at 70 F and 11.7 percent at -423 F.

  3. Fatigue testing of electron beam-melted Ti-6Al-4V ELI alloy for dental implants.

    PubMed

    Joshi, Gaurav V; Duan, Yuanyuan; Neidigh, John; Koike, Mari; Chahine, Gilbert; Kovacevic, Radovan; Okabe, Toru; Griggs, Jason A

    2013-01-01

    Customized one-component dental implants have been fabricated using Electron Beam Melting(®) (EBM(®)), which is a rapid prototyping and manufacturing technique. The goal of our study was to determine the effect of electron beam orientation on the fatigue resistance of EBM Ti-6Al-4V ELI alloy. EBM technique was used to fabricate Ti-6Al-4V ELI alloy blocks, which were cut into rectangular beam specimens with dimensions of 25 × 4 × 3 mm, such that electron beam orientation was either parallel (group A) or perpendicular (group B) to the long axis of the specimens. The specimens were subjected to cyclic fatigue (R = 0.1) in four-point flexure under ambient conditions using various stress amplitudes below the yield stress. The fatigue lifetime data were fit to an inverse power law-Weibull model to predict the peak stress corresponding to failure probabilities of 5 and 63% at 2M cycles (σ(max, 5%) and σ(max, 63%)). Groups A and B did not have significantly different Weibull modulus, m (p > 0.05). The specimens with parallel orientation showed significantly higher σ(max, 63%) (p ≤ 0.05), but there was no significant difference in the σ(max, 5%) (p > 0.05). Thus, it can be concluded that the fatigue resistance of the material was greatest when the electron beam orientation was perpendicular to the direction of crack propagation.

  4. Effect of Test Frequency on Fatigue Crack Growth Rates of Ti-6Al-4V ELI Alloy at Cryogenic Temperature

    SciTech Connect

    Yuri, T.; Ono, Y.; Ogata, T.

    2006-03-31

    In order to clarify the effect of test frequency on the fatigue crack growth rates (da/dN) of Ti-6Al-4V ELI alloy have been investigated at cryogenic temperature. The fatigue crack growth tests were conducted using the test frequencies of 5 and 20 Hz, respectively. At 4 K, the effects of the test frequencies on the fatigue crack growth rates of Ti-6Al-4V ELI alloy were not clear or significant. The fatigue crack growth rates in the low propagation rate region at 4 K were smaller than those at 293 K. On the other hand, those in the high propagation rate region at 4 K were bigger than those at 293 K. The former is considered that the crack closure level was higher as compared to that at 293 K and the latter is due to the difference values of the fracture toughness at 4 and 293 K, respectively. The fracture surfaces of compact tension (CT) specimens in the high propagation rate regions at each test temperature revealed the striations, and furthermore accompanied with the flute fracture surface at 4 K. On the other hand, those of CT specimens in the low propagation rate region at 4 K were found facet-like fracture surfaces corresponding with almost the {alpha}-grain size.

  5. Effect of stress ratio on high-cycle fatigue properties of Ti-6Al-4V ELI alloy forging at low temperature

    NASA Astrophysics Data System (ADS)

    Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio; Matsuoka, Saburo; Sunakawa, Hideo

    2014-01-01

    The effect of the stress ratio R (the ratio of minimum stress to maximum stress) on the high-cycle fatigue properties of Ti-6Al-4V extra-low interstitial (ELI) alloy forging was investigated at 293 and 77 K. At 293 K, the fatigue strength at 107 cycles exhibited deviations below the modified Goodman line in the R=0.01 and 0.5 tests. Moreover, at 77 K, larger deviations of the fatigue strength at 107 cycles below the modified Goodman line were confirmed in the same stress ratio conditions. The high-cycle fatigue strength of the present alloy forging exhibit an anomalous mean stress dependency at both temperatures and this dependency becomes remarkable at low temperature.

  6. Evaluation of the stiffness and friction of Ti6Al4V ELI treated by glow discharge nitriding

    NASA Astrophysics Data System (ADS)

    Tavera, J. R.; Peña Ballesteros, D. Y.; Estupiñán Duran, H. A.

    2016-02-01

    In this study, an evaluation of the elastic-plastic surface hardening on Ti6Al4V ELI titanium nitride films obtained by glow discharge method was carried out by nanoindentation tests according to the standard ISO 14577. The nanotribological properties (metal-metal) were also evaluated using the pin-on-disc system Ti6Al4V surface deposition ELI with nitrogen, obtaining a correlation between the coefficient of friction of Ti6Al4V ELI treated by PVD and the Young's modulus of the respective substrate modified by PVD. To characterize the substrate for the characterization tests, scanning electron microscopy, atomic force microscopy and X-ray diffraction and contact angle were carried out. The results demonstrated that the substrates nitrided improved mechanical and tribological properties, hardness, Young's modulus and coefficient of friction, making the alloy Ti6Al4V ELI support axial loads in tension and compression.

  7. Effects of the microstructure and porosity on properties of Ti-6Al-4V ELI alloy fabricated by electron beam melting (EBM)

    SciTech Connect

    Galarraga, Haize; Lados, Diana A.; Dehoff, Ryan R.; Kirka, Michael M.; Nandwana, Peeyush

    2016-01-01

    Electron Beam Melting (EBM) is a metal powder bed-based Additive Manufacturing (AM) technology that makes possible the fabrication of three dimensional near-net-shaped parts directly from computer models. EBM technology has been in continuously updating, obtaining optimized properties of the processed alloys. Ti-6Al-4V titanium alloy is the most widely used and studied alloy for this technology and is the focus of this work. Several research works have been completed to study the mechanisms of microstructure formation as well as its influence on mechanical properties. However, the relationship is not completely understood, and more systematic research work is necessary in order to attain a better understanding of these features. In this work, samples fabricated at different locations, orientations, and distances from the build platform have been characterized, studying the relationship of these variables with the resulting material intrinsic characteristics and properties (surface topography, microstructure, porosity, micro-hardness and static mechanical properties). This study has revealed that porosity is the main factor controlling mechanical properties relative to the other studied variables. Therefore, in future process developments, decreasing of the porosity should be considered as the primary goal in order to improve mechanical properties.

  8. Effects of the microstructure and porosity on properties of Ti-6Al-4V ELI alloy fabricated by electron beam melting (EBM)

    DOE PAGES

    Galarraga, Haize; Lados, Diana A.; Dehoff, Ryan R.; Kirka, Michael M.; Nandwana, Peeyush

    2016-01-01

    Electron Beam Melting (EBM) is a metal powder bed-based Additive Manufacturing (AM) technology that makes possible the fabrication of three dimensional near-net-shaped parts directly from computer models. EBM technology has been in continuously updating, obtaining optimized properties of the processed alloys. Ti-6Al-4V titanium alloy is the most widely used and studied alloy for this technology and is the focus of this work. Several research works have been completed to study the mechanisms of microstructure formation as well as its influence on mechanical properties. However, the relationship is not completely understood, and more systematic research work is necessary in order tomore » attain a better understanding of these features. In this work, samples fabricated at different locations, orientations, and distances from the build platform have been characterized, studying the relationship of these variables with the resulting material intrinsic characteristics and properties (surface topography, microstructure, porosity, micro-hardness and static mechanical properties). This study has revealed that porosity is the main factor controlling mechanical properties relative to the other studied variables. Therefore, in future process developments, decreasing of the porosity should be considered as the primary goal in order to improve mechanical properties.« less

  9. The design and production of Ti-6Al-4V ELI customized dental implants

    NASA Astrophysics Data System (ADS)

    Chahine, Gilbert; Koike, Mari; Okabe, Toru; Smith, Pauline; Kovacevic, Radovan

    2008-11-01

    This paper addresses the production of customized Ti-6Al-4V ELI dental implants via electron beam melting (EBM). The melting of Ti-6Al-4V ELI powder produces implants with great biocompatibility, fi ne mechanical performance, and a high bone ingrowth potential. The EBM technology is used to produce one-component dental implants that mimic the exact shape of the patient’s tooth, replacing the traditional, three-component, “screw-like” standardized dental implants currently used. The new generation of implants provides the possibility of simplifying pre-insertion procedures leading to faster healing time, and the potential of better and stronger osseointegration, specifi cally through incorporating lattice structure design.

  10. Surface Quality of Ti-6%Al-4%V ELI When Machined Using CVD-Carbide Tools at High Cutting Speed

    SciTech Connect

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.; Yasir, A.; Zaid, Y.; Yanuar, B.

    2011-01-17

    Machining of Ti-6Al-4V ELI becomes more interested topic due to extremely weight-to-strength ratio and resistance to corrosion at elevated temperature. Quality of machined surface is presented by surface roughness, surface texture and damages of microstructure of titanium alloys. The turning parameters evaluated are cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev, depth of cut of 0.10-0.20 mm and tool grade of CVD carbide tools. The results show the trend lines of surface roughness value are higher at the initial machining and the surface texture profile has a strong correlation with the feed rate. At the machining condition of cutting speed of 95 m/min, feed rate of 0.35 mm/rev and depth of cut of 0.10 mm produced the with layer with thickness of 2.0 {mu}m.

  11. Strain-based fatigue data for Ti-6Al-4V ELI under fully-reversed and mean strain loads.

    PubMed

    Carrion, Patricio E; Shamsaei, Nima

    2016-06-01

    This article presents the experimental data supporting the study to obtain the mean strain/stress effects on the fatigue behavior of Ti-6Al-4V ELI. A series of strain-controlled fatigue experiments on Ti-6Al-4V ELI were performed at four strain ratios (-1, -0.5, 0, and 0.5). Two types of data are included for each specimen. These are the hysteresis stress-strain responses for the cycle in a log10 increment, and the maximum and minimum stress-strain responses for each cycle. Fatigue lives are also reported for all the experiments.

  12. Strain-based fatigue data for Ti–6Al–4V ELI under fully-reversed and mean strain loads

    PubMed Central

    Carrion, Patricio E.; Shamsaei, Nima

    2016-01-01

    This article presents the experimental data supporting the study to obtain the mean strain/stress effects on the fatigue behavior of Ti–6Al–4V ELI. A series of strain-controlled fatigue experiments on Ti–6Al–4V ELI were performed at four strain ratios (−1, −0.5, 0, and 0.5). Two types of data are included for each specimen. These are the hysteresis stress–strain responses for the cycle in a log10 increment, and the maximum and minimum stress–strain responses for each cycle. Fatigue lives are also reported for all the experiments. PMID:26952022

  13. Gene expression of human osteoblasts cells on chemically treated surfaces of Ti-6Al-4V-ELI.

    PubMed

    Oliveira, D P; Palmieri, A; Carinci, F; Bolfarini, C

    2015-06-01

    Surface modifications of titanium alloys are useful methods to enhance the biological stability of intraosseous implants and to promote a well succeeded osseointegration in the early stages of implantation. This work aims to investigate the influence of chemically modified surfaces of Ti-6Al-4V-ELI (extra-low interstitial) on the gene expression of human osteoblastic (HOb) cells. The surface treatments by acid etching or acid etching plus alkaline treatment were carried out to modify the topography, effective area, contact angle and chemical composition of the samples. The surface morphology was investigated using: scanning electron microscopy (SEM) and confocal laser-scanning microscope (CLSM). Roughness measurements and effective surface area were obtained using the CLSM. Surface composition was analysed by energy dispersive X-ray spectroscopy (EDX) and by X-Ray Diffraction (XRD). The expression levels of some bone related genes (ALPL, COL1A1, COL3A1, SPP1, RUNX2, and SPARC) were analysed using real-time Reverse Transcription Polymerase Chain Reaction (real-time RT-PCR). The results showed that all the chemical modifications studied in this work influenced the surface morphology, wettability, roughness, effective area and gene expression of human osteoblasts. Acid phosphoric combined to alkaline treatment presented a more accelerated gene expression after 7days while the only phosphoric etching or chloride etching combined to alkaline treatment presented more effective responses after 15days.

  14. Gene expression of human osteoblasts cells on chemically treated surfaces of Ti-6Al-4V-ELI.

    PubMed

    Oliveira, D P; Palmieri, A; Carinci, F; Bolfarini, C

    2015-06-01

    Surface modifications of titanium alloys are useful methods to enhance the biological stability of intraosseous implants and to promote a well succeeded osseointegration in the early stages of implantation. This work aims to investigate the influence of chemically modified surfaces of Ti-6Al-4V-ELI (extra-low interstitial) on the gene expression of human osteoblastic (HOb) cells. The surface treatments by acid etching or acid etching plus alkaline treatment were carried out to modify the topography, effective area, contact angle and chemical composition of the samples. The surface morphology was investigated using: scanning electron microscopy (SEM) and confocal laser-scanning microscope (CLSM). Roughness measurements and effective surface area were obtained using the CLSM. Surface composition was analysed by energy dispersive X-ray spectroscopy (EDX) and by X-Ray Diffraction (XRD). The expression levels of some bone related genes (ALPL, COL1A1, COL3A1, SPP1, RUNX2, and SPARC) were analysed using real-time Reverse Transcription Polymerase Chain Reaction (real-time RT-PCR). The results showed that all the chemical modifications studied in this work influenced the surface morphology, wettability, roughness, effective area and gene expression of human osteoblasts. Acid phosphoric combined to alkaline treatment presented a more accelerated gene expression after 7days while the only phosphoric etching or chloride etching combined to alkaline treatment presented more effective responses after 15days. PMID:25842132

  15. Laser Assisted Milling of Ti-6Al-4V ELI with the Analysis of Surface Integrity and its Economics

    NASA Astrophysics Data System (ADS)

    Hedberg, Gary K.; Shin, Yung C.

    2015-09-01

    This study presents the experimental evaluation of laser assisted milling (LAML) of Ti-6AL-4V ELI (Ti-64), which is used in the orthopedic industry, by using localized preheating of the workpiece via laser irradiation. Improvements to the machinability of this material with LAML are assessed while considering the surface integrity. Suitable laser heating conditions as well as machining conditions are determined based on temperature prediction modeling. Machinability improvements are shown in terms of tool wear, material removal rates and cutting force reduction. Systematic characterization of samples is shown to demonstrate that the machined sub-surfaces are not adversely affected during LAML by precisely controlling laser heating, via hardness measurements, scanning electron microscopy (SEM) for microstructure analysis, and X-ray diffraction (XRD) for residual stresses. An economic analysis shows that LAML provides the cost reduction over conventional machining.

  16. Mechanochemical processing of nanocrystalline Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Pirzada, M. D. S.; (Sam) Froes, F. H.; Patankar, S. N.

    2004-06-01

    Synthesis of nanocrystalline Ti-6Al-4V was explored using mechanochemical processing. The reaction mixture was comprised of CaH2, Mg powder, anhydrous AlCl3, anhydrous VCl3, and TiCl4. The milled powder (reaction product) primarily consisted of nanocrystalline alloy hydride having a composition (Ti-6Al-4V)H1.942, along with MgCl2 and CaCl2 as by-products. Aqueous solutions of nitric acid, sulfuric acid, and 1 pct sodium sulfite were found to be very effective in leaching of the chlorides from the milled powder. The (Ti-6Al-4V)H1.942 on dehydrogenation at 375°C resulted in nanocrystalline Ti-6Al-4V alloy powder.

  17. Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

    NASA Astrophysics Data System (ADS)

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

    2011-01-01

    The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

  18. Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

    SciTech Connect

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

    2011-01-17

    The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

  19. Surface integrity after pickling and anodization of Ti-6Al-4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Vermesse, Eric; Mabru, Catherine; Arurault, Laurent

    2013-11-01

    The surface integrity of Ti-6Al-4V titanium alloy was studied at different stages of surface treatments, especially pickling and compact anodization, through surface characteristics potentially worsening fatigue resistance.

  20. Osteoblastic behavior to zirconium coating on Ti-6Al-4V alloy

    PubMed Central

    Lee, Bo-Ah; Kim, Hae-Jin; Xuan, Yun-Ze; Park, Yeong-Joon; Chung, Hyun-Ju

    2014-01-01

    PURPOSE The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method. MATERIALS AND METHODS The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured. RESULTS SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group. CONCLUSION These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants. PMID:25551012

  1. Porous Ti6Al4V alloys with enhanced normalized fatigue strength for biomedical applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Zhou, Lian

    2016-03-01

    In this paper, porous Ti6Al4V alloys for biomedical applications were fabricated by diffusion bonding of alloy meshes. The compression-compression fatigue behavior was studied. It results that porous Ti6Al4V alloys show enhanced normalized fatigue strength which is in the range of 0.5-0.55 at 10(6)cycles. The porosity has some effect on the absolute S-N curves but minor effect on the normalized S-N curves. The relationship between strain per cycle and number of cycles shows three distinct stages and the value of strain per cycle is constant in stage II. The reasons for the higher normalized fatigue strength of porous Ti6Al4V alloys are discussed based on the fatigue crack initiation and propagation.

  2. Corrosion behavior of cast Ti-6Al-4V alloyed with Cu.

    PubMed

    Koike, Marie; Cai, Zhuo; Oda, Yutaka; Hattori, Masayuki; Fujii, Hiroyuki; Okabe, Toru

    2005-05-01

    It has recently been found that alloying with copper improved the inherently poor grindability and wear resistance of titanium. This study characterized the corrosion behavior of cast Ti-6Al-4V alloyed with copper. Alloys (0.9 or 3.5 mass % Cu) were cast with the use of a magnesia-based investment in a centrifugal casting machine. Three specimen surfaces were tested: ground, sandblasted, and as cast. Commercially pure titanium and Ti-6Al-4V served as controls. Open-circuit potential measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air + 10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was conducted in the same medium deaerated by N(2) + 10% CO(2). Polarization resistance (R(p)), Tafel slopes, and corrosion current density (I(corr)) were determined. A passive region occurred for the alloy specimens with ground and sandblasted surfaces, as for CP Ti. However, no passivation was observed on the as-cast alloys or on CP Ti. There were significant differences among all metals tested for R(p) and I(corr) and significantly higher R(p) and lower I(corr) values for CP Ti compared to Ti-6Al-4V or the alloys with Cu. Alloying up to 3.5 mass % Cu to Ti-6Al-4V did not change the corrosion behavior. Specimens with ground or sandblasted surfaces were superior to specimens with as-cast surfaces. PMID:15744719

  3. New Powder Metallurgical Approach to Achieve High Fatigue Strength in Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.; Kumar, Pankaj; Sun, Pei; Zak Fang, Z.; Koopman, Mark

    2016-05-01

    Recently, manufacturing of titanium by sintering and dehydrogenation of hydride powders has generated a great deal of interest. An overarching concern regarding powder metallurgy (PM) titanium is that critical mechanical properties, especially the high-cycle fatigue strength, are lower than those of wrought titanium alloys. It is demonstrated here that PM Ti-6Al-4V alloy with mechanical properties comparable (in fatigue strength) and exceeding (in tensile properties) those of wrought Ti-6Al-4V can be produced from titanium hydride powder, through the hydrogen sintering and phase transformation process. Tensile and fatigue behavior, as well as fatigue fracture mechanisms, have been investigated under three processing conditions. It is shown that a reduction in the size of extreme-sized pores by changing the hydride particle size distribution can lead to improved fatigue strength. Further densification by pneumatic isostatic forging leads to a fatigue strength of ~550 MPa, comparable to the best of PM Ti-6Al-4V alloys prepared by other methods and approaching the fatigue strengths of wrought Ti-6Al-4V alloys. The microstructural factors that limit fatigue strength in PM titanium have been investigated, and pathways to achieve greater fatigue strengths in PM Ti-6Al-4V alloys have been identified.

  4. Lattice variations of Ti-6Al-4V alloy with hydrogen content

    SciTech Connect

    Zhu Tangkui Li, Miaoquan

    2011-07-15

    Effect of hydrogen content on the lattice parameter of Ti-6Al-4V alloy has been investigated by X-ray diffraction. The experimental results show that the solution of hydrogen in the Ti-6Al-4V alloy affects significantly on the lattice parameters of {alpha}, {beta} and {delta} phases, especially the {beta} phase. Furthermore, the critical hydrogen content of {delta} hydride formation for Ti-6Al-4V alloy is 0.385 wt.%. When the hydrogen content is lower than the critical hydrogen content, the {delta} hydride cannot precipitate and the lattice parameter ({alpha}) of {beta} phase linearly increases with the increasing of hydrogen content. When the hydrogen content is higher than the critical hydrogen content, the {delta} hydride precipitates and the lattice parameter ({alpha}) of {beta} phase varies inconspicuously with hydrogen content. In addition, the effects of lattice variations and {delta} hydride formation on microstructure are discussed. The {alpha}/{beta} interfaces of lamellar transformed {beta} phase become fuzzy with the increasing of hydrogen content because of the lattice expansion of {beta} phase. Compared with that of the Ti-6Al-4V alloy at low hydrogen content ({<=} 0.385 wt.%), the contrasts of primary {alpha} phase and transformed {beta} phase of Ti-6Al-4V alloy at high hydrogen content ({>=} 0.385 wt.%) were completely reversed due to the formation of {delta} hydride. - Research Highlights: {yields} A novel method for determining {delta} hydride in Ti-6Al-4V alloy is presented. {yields} The critical hydrogen content of {delta} hydride formation is 0.385 wt.%. {yields} The lattice parameter of {beta} phase can be expressed as follows: a=0.323(1+9.9x10{sup -2}C{sub H}) . {yields} Precipitation of {delta} hydride has a significant influence on the microstructure. {yields} The {alpha}/{beta} interfaces of transformed {beta} phase became fuzzy in the hydrogenated alloy.

  5. Study on improved tribological properties by alloying copper to CP-Ti and Ti-6Al-4V alloy.

    PubMed

    Wang, Song; Ma, Zheng; Liao, Zhenhua; Song, Jian; Yang, Ke; Liu, Weiqiang

    2015-12-01

    Copper alloying to titanium and its alloys is believed to show an antibacterial performance. However, the tribological properties of Cu alloyed titanium alloys were seldom studied. Ti-5Cu and Ti-6Al-4V-5Cu alloys were fabricated in the present study in order to further study the friction and wear properties of titanium alloys with Cu additive. The microstructure, composition and hardness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and hardness tester. The tribological behaviors were tested with ZrO2 counterface in 25% bovine serum using a ball-on-disc tribo-tester. The results revealed that precipitations of Ti2Cu intermetallic compounds appeared in both Ti-5Cu and Ti-6Al-4V-5Cu alloys. The tribological results showed an improvement in friction and wear resistance for both Ti-5Cu and Ti-6Al-4V-5Cu alloys due to the precipitation of Ti2Cu. The results also indicated that both CP-Ti and Ti-5Cu behaved better wear resistance than Ti-6Al-4V and Ti-6Al-4V-5Cu due to different wear mechanisms when articulated with hard zirconia. Both CP-Ti and Ti-5Cu revealed dominant adhesive wear with secondary abrasive wear mechanism while both Ti-6Al-4V and Ti-6Al-4V-5Cu showed severe abrasive wear and cracks with secondary adhesive wear mechanism due to different surface hardness integrated by their microstructures and material types.

  6. High performance Ti-6Al-4V alloy by creation of harmonic structure design

    NASA Astrophysics Data System (ADS)

    Vajpai, Sanjay Kumar; Ameyama, Kei; Ota, Mie; Watanabe, Tomoyuki; Maeda, Ryo; Sekiguchi, Tatsuya; Dirras, Guy; Tingaud, David

    2014-08-01

    Ti-6Al-4V alloy is an advanced structural material having applications in a wide range of areas spanning from biomedical to aerospace sectors due to the excellent combination of mechanical and chemical properties. In the present work, a new tailored heterogeneous microstructural design with a specific topological distribution of fine and coarse grained areas, called "harmonic structure", has been proposed for the strengthening of Ti-6Al-4V alloy to achieve improved performance of the components in service. It has been demonstrated that Ti-6Al-4V alloy with harmonic structure can be successfully prepared via a powder metallurgy route consisting of controlled severe plastic deformation of pre-alloyed powders via mechanical milling followed by their consolidation. The Ti-6Al-4V compacts with harmonic structure design exhibited significantly better strength and ductility, under quasi-static as well as rapid loading conditions, as compared to their homogeneous fine and coarse grained counterparts. It was found that the harmonic structure design has the ability to promote the uniform distribution of strain during plastic deformation, leading to improved mechanical properties by avoiding localized plastic instability.

  7. Quasi-static Torsional Deformation Behavior of Porous Ti6Al4V alloy.

    PubMed

    Balla, Vamsi Krishna; Martinez, Shantel; Rogoza, Ben Tunberg; Livingston, Chase; Venkateswaran, Deepak; Bose, Susmita; Bandyopadhyay, Amit

    2011-07-20

    Laser processed Ti6Al4V alloy samples with total porosities of 0%, 10% and 20% have been subjected to torsional loading to determine mechanical properties and to understand the deformation behavior. The torsional yield strength and modulus of porous Ti alloy samples was found to be in the range of 185-332 MPa and 5.7-11 GPa, respectively. With an increase in the porosity both the strength and the modulus decreased, and at 20% porosity the torsional modulus of Ti6Al4V alloy was found to be very close to that of human cortical bone. Further, the experiments revealed clear strain hardening and ductile deformation in all the samples, which suggests that the inherent brittleness associated solid-state sintered porous materials can be completely eliminated via laser processing for load bearing metal implant applications.

  8. Shot peening for Ti-6Al-4V alloy compressor blades

    NASA Technical Reports Server (NTRS)

    Carek, Gerald A.

    1987-01-01

    A text program was conducted to determine the effects of certain shot-peening parameters on the fatigue life of the Ti-6Al-4V alloys as well as the effect of a demarcation line on a test specimen. This demarcation line, caused by an abrupt change from untreated surface to shot-peened surface, was thought to have caused the failure of several blades in a multistage compressor at the NASA Lewis Research Center. The demarcation line had no detrimental effect upon bending fatigue specimens tested at room temperature. Procedures for shot peening Ti-6Al-4V compressor blades are recommended for future applications.

  9. Microstructural Influence on Mechanical Properties in Plasma Microwelding of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Baruah, M.; Bag, S.

    2016-09-01

    The complexity of joining Ti6Al4V alloy enhances with reduction in sheet thickness. The present work puts emphasis on microplasma arc welding (MPAW) of 500-μm-thick Ti6Al4V alloy in butt joint configuration. Using controlled and regulated arc current, the MPAW process is specifically designed to use in joining of thin sheet components over a wide range of process parameters. The weld quality is assessed by carefully controlling the process parameters and by reducing the formation of oxides. The combined effect of welding speed and current on the weld joint properties is evaluated for joining of Ti6Al4V alloy. The macro- and microstructural characterizations of the weldment by optical microscopy as well as the analysis of mechanical properties by microtensile and microhardness test have been performed. The weld joint quality is affected by specifically designed fixture that controls the oxidation of the joint and introduces high cooling rate. Hence, the solidified microstructure of welded specimen influences the mechanical properties of the joint. The butt joint of titanium alloy by MPAW at optimal process parameters is of very high quality, without any internal defects and with minimum residual distortion.

  10. Effect of Thermodiffusion Nitriding on Cytocompatibility of Ti-6Al-4V Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Pohrelyuk, I. M.; Tkachuk, O. V.; Proskurnyak, R. V.; Boiko, N. M.; Kluchivska, O. Yu.; Stoika, R. S.

    2016-04-01

    The nitrided layer was formed on the surface of Ti-6Al-4V titanium alloy by the thermodiffusion saturation in nitrogen at the atmospheric pressure. The study of the vitality of pseudonormal human embryo kidney cells of the HEK293T line showed that their cultivation in the presence of the untreated alloy sample is accompanied by a statistically significant reduction in the number of living cells compared with the control sample (untreated cells), whereas their cultivation in the presence of the nitrided alloy sample does not change the cell number considerably. In addition, it was shown that cell behavior in the presence of the nitrided sample differs only slightly from the control sample, whereas the growth of cells in the presence of the untreated alloy differed significantly from that in the control sample, demonstrating small groups of cells instead of their big clusters.

  11. Microstructure evolution and grain refinement of Ti-6Al-4V alloy by laser shock processing

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Zhou, W. F.; Liu, F. F.; Ren, Y. P.; Yuan, S. Q.; Ren, N. F.; Xu, S. D.; Yang, T.

    2016-02-01

    Microstructure evolution and grain refinement of Ti-6Al-4V alloy after laser shock processing (LSP) are systematically investigated in this paper. Laser shock waves were induced by a Q-switched Nd:YAG laser system operated with a wave-length of 1064 nm and 10 ns pulse width. The microstructures of LSP samples were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Present results indicate that the surface hardness of samples subjected to LSP impacts has significantly improved. Multidirectional twin intersections and dislocation movements lead to grain subdivision in α phase with ultra-high plastic deformation. High-density dislocations are found in β phase. Multidirectional twin intersections and division of sub-grain boundaries play an important role in the grain refinement of Ti-6Al-4V alloy under LSP loading conditions.

  12. Microstructure-Tensile Properties Correlation for the Ti-6Al-4V Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Shi, Xiaohui; Zeng, Weidong; Sun, Yu; Han, Yuanfei; Zhao, Yongqing; Guo, Ping

    2015-04-01

    Finding the quantitative microstructure-tensile properties correlations is the key to achieve performance optimization for various materials. However, it is extremely difficult due to their non-linear and highly interactive interrelations. In the present investigation, the lamellar microstructure features-tensile properties correlations of the Ti-6Al-4V alloy are studied using an error back-propagation artificial neural network (ANN-BP) model. Forty-eight thermomechanical treatments were conducted to prepare the Ti-6Al-4V alloy with different lamellar microstructure features. In the proposed model, the input variables are microstructure features including the α platelet thickness, colony size, and β grain size, which were extracted using Image Pro Plus software. The output variables are the tensile properties, including ultimate tensile strength, yield strength, elongation, and reduction of area. Fourteen hidden-layer neurons which can make ANN-BP model present the most excellent performance were applied. The training results show that all the relative errors between the predicted and experimental values are within 6%, which means that the trained ANN-BP model is capable of providing precise prediction of the tensile properties for Ti-6Al-4V alloy. Based on the corresponding relations between the tensile properties predicted by ANN-BP model and the lamellar microstructure features, it can be found that the yield strength decreases with increasing α platelet thickness continuously. However, the α platelet thickness exerts influence on the elongation in a more complicated way. In addition, for a given α platelet thickness, the yield strength and the elongation both increase with decreasing β grain size and colony size. In general, the β grain size and colony size play a more important role in affecting the tensile properties of Ti-6Al-4V alloy than the α platelet thickness.

  13. Microstructure, mechanical and wear properties of laser surface melted Ti6Al4V alloy.

    PubMed

    Balla, Vamsi Krishna; Soderlind, Julie; Bose, Susmita; Bandyopadhyay, Amit

    2014-04-01

    Laser surface melting (LSM) of Ti6Al4V alloy was carried out with an aim to improve properties such as microstructure and wear for implant applications. The alloy substrate was melted at 250W and 400W at a scan velocity of 5mm/s, with input energy of 42J/mm(2) and 68J/mm(2), respectively. The results showed that equiaxed α+β microstructure of the substrate changes to mixture of acicular α in β matrix after LSM due to high cooling rates in the range of 2.25×10(-3)K/s and 1.41×10(-3)K/s during LSM. Increasing the energy input increased the thickness of remelted region from 779 to 802µm and 1173 to 1199µm. Similarly, as a result of slow cooling rates under present experimental conditions, the grain size of the alloy increased from 4.8μm to 154-199μm. However, the hardness of the Ti6Al4V alloy increased due to LSM melting and resulted in lowest in vitro wear rate of 3.38×10(-4)mm(3)/Nm compared to untreated substrate with a wear rate of 6.82×10(-4)mm(3)/Nm.

  14. Feasibility study of the production of biomedical Ti-6Al-4V alloy by powder metallurgy.

    PubMed

    Bolzoni, L; Ruiz-Navas, E M; Gordo, E

    2015-04-01

    Titanium and its alloys are characterized by an exceptional combination of properties like high strength, good corrosion resistance and biocompatibility which makes them suitable materials for biomedical prosthesis and devices. The wrought Ti-6Al-4V alloy is generally favored in comparison to other metallic biomaterials due to its relatively low elastic modulus and it has been long used to obtain products for biomedical applications. In this work an alternative route to fabricate biomedical implants made out of the Ti-6Al-4V alloy is investigated. Specifically, the feasibility of the conventional powder metallurgy route of cold uniaxial pressing and sintering is addressed by considering two types of powders (i.e. blended elemental and prealloyed). The characterization of physical properties, chemical analysis, mechanical behavior and microstructural analysis is carried out in-depth and the properties are correlated among them. On the base of the results found, the produced alloys are promising materials for biomedical applications as well as cheaper surgical devices and tools.

  15. In vitro assessment of Staphylococcus epidermidis and Staphylococcus aureus adhesion on TiO₂ nanotubes on Ti-6Al-4V alloy.

    PubMed

    Pérez-Jorge, Concepción; Conde, Ana; Arenas, Maria A; Pérez-Tanoira, Ramón; Matykina, Endhze; de Damborenea, Juan J; Gómez-Barrena, Enrique; Esteban, Jaime

    2012-07-01

    The aim of this study was to evaluate Staphylococcus sp. adhesion to modified surfaces of titanium alloy (Ti-6Al-4V). Specimens of Ti-6Al-4V alloy 6-4 ELI-grade 23 that meets the requirements of ASTM F136 2002A (AMS 2631B class A1) were anodized in a mixture of sulfuric/hydrofluoric acid at 20 V for 5 and 60 min to form nanoporous (NP) and nanotubular (NT) oxide layers with pore diameter of 20 and 100 nm, respectively. The amount of fluorine incorporated in the oxide films from the electrolyte was 6 and 4 wt %, respectively. Bacterial adherence was studied using laboratory strains and six clinical strains each of Staphylococcus aureus and Staphylococcus epidermidis. Lower adherence of laboratory strains was demonstrated on fluoride nanostructured surfaces in comparison with the fluoride-free surfaces. Significant differences between clinical strains and laboratory strains were also found (p < 0.0001, Kruskal-Wallis test) when NP and NT specimens were compared with chemically polished (CP) surfaces. The results of the tests using multiple clinical strains confirmed a decrease in bacterial adherence on F-containing titanium oxide surfaces, suggesting a potential applicability of this surface, with a confirmed added value of decreasing clinical staphylococci adherence, for medical prosthetic devices.

  16. Effect of plasma welding parameters on the flexural strength of Ti-6Al-4V alloy.

    PubMed

    Lyra e Silva, João Paulo; Fernandes Neto, Alfredo Júlio; Raposo, Luís Henrique Araújo; Novais, Veridiana Resende; de Araujo, Cleudmar Amaral; Cavalcante, Luisa de Andrade Lima; Simamoto Júnior, Paulo Cezar

    2012-01-01

    The aim of this study was to assess the effect of different plasma arc welding parameters on the flexural strength of titanium alloy beams (Ti-6Al-4V). Forty Ti-6Al-4V and 10 NiCr alloy beam specimens (40 mm long and 3.18 mm diameter) were prepared and divided into 5 groups (n=10). The titanium alloy beams for the control group were not sectioned or subjected to welding. Groups PL10, PL12, and PL14 contained titanium beams sectioned and welded at current 3 A for 10, 12 or 14 ms, respectively. Group NCB consisted of NiCr alloy beams welded using conventional torch brazing. After, the beams were subjected to a three-point bending test and the values obtained were analyzed to assess the flexural strength (MPa). Statistical analysis was carried out by one-way ANOVA and Tukey's HSD test at 0.05 confidence level. Significant difference was verified among the evaluated groups (p<0.001), with higher flexural strength for the control group (p<0.05). No significant differences was observed among the plasma welded groups (p>0.05). The NCB group showed the lowest flexural strength, although it was statistically similar to the PL 14 group (p>0.05). The weld depth penetration was not significantly different among the plasma welded groups (p=0.05). Three representative specimens were randomly selected to be evaluated under scanning electron microcopy. The composition of the welded regions was analyzed by energy dispersive X-ray spectroscopy. This study provides an initial set of parameters supporting the use of plasma welding during fabrication of titanium alloy dental frameworks. PMID:23338261

  17. A study of cumulative fatigue damage in titanium 6Al-4V alloy

    NASA Technical Reports Server (NTRS)

    Jeelani, S.; Ghebremedhin, S.; Musial, M.

    1986-01-01

    Experimental data were obtained using titanium 6Al-4V alloy under stress ratios of -1, 0, and negative infinity. A study of cumulative fatigue damage using Miner's (1945) and Kramer's (1974) equations for stress ratios of -1 and 0 for low-high, low-high mixed, high-low, and high-low mixed stress sequences has revealed close agreement between the theoretical and experimental values of fatigue damage and fatigue life. Kramer's equation predicts less conservative and more realistic cumulative fatigue damage than does the popularly used Miner's rule.

  18. Modification of surface morphology of Ti6Al4V alloy manufactured by Laser Sintering

    NASA Astrophysics Data System (ADS)

    Draganovská, Dagmar; Ižariková, Gabriela; Guzanová, Anna; Brezinová, Janette; Koncz, Juraj

    2016-06-01

    The paper deals with the evaluation of relation between roughness parameters of Ti6Al4V alloy produced by DMLS and modified by abrasive blasting. There were two types of blasting abrasives that were used - white corundum and Zirblast at three levels of air pressure. The effect of pressure on the value of individual roughness parameters and an influence of blasting media on the parameters for samples blasted by white corundum and Zirblast were evaluated by ANOVA. Based on the measured values, the correlation matrix was set and the standard of correlation statistic importance between the monitored parameters was determined from it. The correlation coefficient was also set.

  19. Gas nitriding and subsequent oxidation of Ti-6Al-4V alloys

    PubMed Central

    2012-01-01

    Ti-6Al-4V alloys consisting of α-Ti grains and intergranular β-Ti islands were nitrided at 850°C for 1 to 12 h under a nitrogen pressure of 1 Pa. With increasing nitriding time, the Ti-N compound layer became thicker, and the α-Ti diffusion zone containing dissolved nitrogen became wider. In the Ti-N compound layer, the initially formed Ti2N became TiN as the nitriding progressed. The nitride layers were oxidized to rutile-TiO2 after oxidation at 700°C for 10 h in air. PMID:22221679

  20. Determination of the thermophysical properties of liquid and solid Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Zhou, K.; Wei, B.

    2016-03-01

    The surface tension and specific heat for liquid ternary Ti-6Al-4V alloy were measured by the oscillating drop method and drop calorimetry, respectively, under containerless condition over broad temperature ranges. The solidification microstructures at different undercoolings appeared as the basket-weave morphology. The relationship between dendritic growth velocity of β phase and undercooling was determined as a power function, and the growth velocity attained 22.21 ms-1 at the maximum undercooling of 252 K (0.13 T L). The mechanical property of this alloy solidified at different undercoolings was determined through compression tests, while its thermal diffusivity in the solid state was measured by the laser flash method.

  1. Effect of Tricalcium Magnesium Silicate Coating on the Electrochemical and Biological Behavior of Ti-6Al-4V Alloys

    PubMed Central

    Hadipour, Mohammadreza; Nadernezhad, Ali; Aghaie, Ermia; Behnamian, Yashar; Abu Osman, Noor Azuan

    2015-01-01

    In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm2 to 0.31 μA/cm2. Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints. PMID:26383641

  2. Effect of Tricalcium Magnesium Silicate Coating on the Electrochemical and Biological Behavior of Ti-6Al-4V Alloys.

    PubMed

    Maleki-Ghaleh, Hossein; Hafezi, Masoud; Hadipour, Mohammadreza; Nadernezhad, Ali; Aghaie, Ermia; Behnamian, Yashar; Abu Osman, Noor Azuan

    2015-01-01

    In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm2 to 0.31 μA/cm2. Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints.

  3. Transient Liquid Phase Diffusion Bonding of Magnesium Alloy (Mg-AZ31) to Titanium Alloy (Ti-6Al-4V)

    NASA Astrophysics Data System (ADS)

    Atieh, Anas Mahmoud

    The magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al-4V have physical characteristics and mechanical properties that makes it attractive for a wide range of engineering applications in the aerospace and automotive industries. However, the differences in melting temperature and coefficient of thermal expansion hinder the use of traditional fusion welding techniques. Transient liquid phase (TLP) bonding of magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al- 4V was performed and different interlayer types and configurations were used to facilitate joint formation. The joining of these alloys using Ni foils was successful at a bonding temperature of 515°C, bonding pressure 0.2 MPa, for bonding time of 5 minutes. At the Ni/Mg-AZ31 bond interface, the formation of a eutectic liquid between Mg and Ni was observed. The formation of Mg2Ni and Mg3AlNi2 were identified along the bond interface resulting in an isothermally solidified joint. At the Ni/Ti-6Al-4V interface, the solid-state diffusion process results in joint formation. The use of double Ni-Cu sandwich joint resulted in further enhancement in joint formation and this produced joints with greater shear strength values. The configuration of Mg-AZ31/Cu- Ni/Ti-6Al-4V or Mg-AZ31/Ni-Cu/Ti-6Al-4V influence the mechanism of bonding and the type of intermetallics formed within the joint. The application of thin Ni electrodeposited coatings resulted in further enhancements of joint quality due to better surface-to-surface contact and a reduction in the formation of intermetallics at the joint. The effect of Cu nano-particles in the coatings was found to decrease the eutectic zone width and this resulted in an increase the shear strength of the joints. The highest shear strength of 69 MPa was possible with bonds made using coatings containing Cu nano-particle dispersion.

  4. Cell interaction with modified nanotubes formed on titanium alloy Ti-6Al-4V.

    PubMed

    Moravec, Hynek; Vandrovcova, Marta; Chotova, Katerina; Fojt, Jaroslav; Pruchova, Eva; Joska, Ludek; Bacakova, Lucie

    2016-08-01

    Nanotubes with diameters ranging from 40 to 60nm were prepared by electrochemical oxidation of the Ti-6Al-4V alloy in electrolyte containing ammonium sulphate and ammonium fluoride. The nanotubes were further modified with calcium and phosphate ions or were heat treated. Polished Ti-6Al-4V alloy served as a reference sample. The spreading of human osteoblast-like cells was similar on all nanotube samples but lower than on polished samples. The number of initially adhered cells was higher on non-modified nanotubes, but the final cell number was the highest on Ca-enriched nanotubes and the lowest on heat-treated nanotubes. However, these differences were relatively small and less pronounced than the differences in the concentration of specific molecular markers of cell adhesion and differentiation, estimated by their intensity of immunofluorescence staining. The concentration of vinculin, i.e. a protein of focal adhesion plaques, was the lowest on nanotubes modified with calcium. Collagen I, an early marker of osteogenic cell differentiation, was also the lowest on samples modified with calcium and was highest on polished samples. Alkaline phosphatase, a middle marker of osteogenic differentiation, was observed in lowest concentration on nanotubes modified with phosphorus and the highest on heat-treated samples. Osteocalcin concentrations, a late marker of osteogenic cell differentiation, were similar on all tested samples, although they tended to be the highest on heat-treated samples. Thus, osteogenic differentiation can be modulated by various additional treatments of nanotube coatings on Ti-6Al-4V implants. PMID:27157757

  5. Grain Refinement of Freeform Fabricated Ti-6Al-4V Alloy Using Beam/Arc Modulation

    NASA Technical Reports Server (NTRS)

    Mitzner, Scott; Liu, Stephen; Domack, Marcia S.; Hafley, Robert A.

    2012-01-01

    Grain refinement can significantly improve the mechanical properties of freeform-fabricated Ti-6Al-4V alloy, promoting increased strength and enhanced isotropy compared with coarser grained material. Large beta-grains can lead to a segregated microstructure, in regard to both alpha-phase morphology and alpha-lath orientation. Beam modulation, which has been used in conventional fusion welding to promote grain refinement, is explored in this study for use in additive manufacturing processes including electron beam freeform fabrication (EBF(sup 3)) and gas-tungsten arc (GTA) deposition to alter solidification behavior and produce a refined microstructure. The dynamic molten pool size induced by beam modulation causes rapid heat flow variance and results in a more competitive grain growth environment, reducing grain size. Consequently, improved isotropy and strength can be achieved with relatively small adjustments to deposition parameters.

  6. Influence of artificial saliva compositions on tribological characteristics of Ti-6Al-4V implant alloy.

    PubMed

    Andrysewicz, Edyta; Mystkowska, Joanna; Kolmas, Joanna; Jałbrzykowski, Marek; Olchowik, Rafał; Dąbrowski, Jan R

    2012-01-01

    The present paper describes the results of tests on the influence of human saliva and its substitutes on tribological characteristics of implant materials on the example of the Ti-6Al-4V (a-Ti) titanium alloy. The saliva substitutes were prepared on the basis of pyrophosphates and mucins dissolved in saline buffer. The results of the presented tribological tests show that the values of the parameters under research varied from each other, while much similarity was observed between the evaluated level of wear characteristics after the friction process in the human saliva environment and that in the environment of one of the mucins tested. The microscopic observations of surfaces of the a-Ti samples after friction revealed varied forms of tribological wear. Infrared microspectroscopy studies of surfaces of the a-Ti samples after friction revealed the presence of secondary lubricating films based on mucin found in the artificial saliva solutions.

  7. Problems Associated with Attaching Strain Gages to Titanium Alloy Ti-61-4V

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.; Lemcoe, M. M.

    1977-01-01

    Weldable strain gages have shown excellent high temperature characteristics for supersonic cruise aircraft application. The spotwelding attachment method, however, has resulted in serious reductions in the fatigue life of titanium alloy (Ti-6Al-4V) fatigue specimens. The reduction is so severe that the use of weldable strain gages on operational aircraft must be prohibited. The cause of the fatigue problem is thought to be a combination of the microstructure changes in the material caused by spotwelding and the presence of the flange of the stain gage. Brazing, plating, and plasma spraying were investigated as substitutes for spotwelding. The attachment of a flangeless gage by plasma spraying provided the most improvement in the fatigue life of the titanium.

  8. Viscoelastoplastic Deformation and Damage Response of Titanium Alloy, Ti-6Al-4V, at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Lerch, Bradley A.; Saleeb, Atef F.; Kasemer, Matthew P.

    2013-01-01

    Time-dependent deformation and damage behavior can significantly affect the life of aerospace propulsion components. Consequently, one needs an accurate constitutive model that can represent both reversible and irreversible behavior under multiaxial loading conditions. This paper details the characterization and utilization of a multi-mechanism constitutive model of the GVIPS class (Generalized Viscoplastic with Potential Structure) that has been extended to describe the viscoelastoplastic deformation and damage of the titanium alloy Ti-6Al-4V. Associated material constants were characterized at five elevated temperatures where viscoelastoplastic behavior was observed, and at three elevated temperatures where damage (of both the stiffness reduction and strength reduction type) was incurred. Experimental data from a wide variety of uniaxial load cases were used to correlate and validate the proposed GVIPS model. Presented are the optimized material parameters, and the viscoelastoplastic deformation and damage responses at the various temperatures.

  9. Influence of Grain Size on Electrically Assisted Tensile Behavior of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Li, Xifeng; Ji, Boyu; Zhou, Qiang; Chen, Jun; Gao, Peng

    2016-10-01

    The effect of grain size and current density on deformation behavior during electrically assisted tension of Ti-6Al-4V alloy was investigated. The microstructural variations under different conditions were observed by optical microscope, SEM and TEM. The dislocation density was quantified by x-ray diffraction technique. The decrease in grain size could increase the elongation growth and stress reduction during electrically assisted tension. Fine grain size specimens can reach higher temperature than coarse grain specimens. With increasing current density, wider and deeper dimples on the fracture surfaces were observed, and less dislocation density and pileups were found in comparison with room-temperature tension without current. The dislocation density has a 62.1% reduction at 10.48 A/mm2 compared with room-temperature tension for 9.2 μm grain size specimens.

  10. Fatigue performance of medical Ti6Al4V alloy after mechanical surface treatments.

    PubMed

    Sonntag, Robert; Reinders, Jörn; Gibmeier, Jens; Kretzer, J Philippe

    2015-01-01

    Mechanical surface treatments have a long history in traditional engineering disciplines, such as the automotive or aerospace industries. Today, they are widely applied to metal components to increase the mechanical performance of these. However, their application in the medical field is rather rare. The present study aims to compare the potential of relevant mechanical surface treatments on the high cycle fatigue (R = 0.1 for a maximum of 10 million cycles) performance of a Ti6Al4V standard alloy for orthopedic, spinal, dental and trauma surgical implants: shot peening, deep rolling, ultrasonic shot peening and laser shock peening. Hour-glass shaped Ti6Al4V specimens were treated and analyzed with regard to the material's microstructure, microhardness, residual stress depth profiles and the mechanical behavior during fatigue testing. All treatments introduced substantial compressive residual stresses and exhibited considerable potential for increasing fatigue performance from 10% to 17.2% after laser shock peening compared to non-treated samples. It is assumed that final mechanical surface treatments may also increase fretting wear resistance in the modular connection of total hip and knee replacements.

  11. Fatigue performance of medical Ti6Al4V alloy after mechanical surface treatments.

    PubMed

    Sonntag, Robert; Reinders, Jörn; Gibmeier, Jens; Kretzer, J Philippe

    2015-01-01

    Mechanical surface treatments have a long history in traditional engineering disciplines, such as the automotive or aerospace industries. Today, they are widely applied to metal components to increase the mechanical performance of these. However, their application in the medical field is rather rare. The present study aims to compare the potential of relevant mechanical surface treatments on the high cycle fatigue (R = 0.1 for a maximum of 10 million cycles) performance of a Ti6Al4V standard alloy for orthopedic, spinal, dental and trauma surgical implants: shot peening, deep rolling, ultrasonic shot peening and laser shock peening. Hour-glass shaped Ti6Al4V specimens were treated and analyzed with regard to the material's microstructure, microhardness, residual stress depth profiles and the mechanical behavior during fatigue testing. All treatments introduced substantial compressive residual stresses and exhibited considerable potential for increasing fatigue performance from 10% to 17.2% after laser shock peening compared to non-treated samples. It is assumed that final mechanical surface treatments may also increase fretting wear resistance in the modular connection of total hip and knee replacements. PMID:25823001

  12. Fatigue Performance of Medical Ti6Al4V Alloy after Mechanical Surface Treatments

    PubMed Central

    Sonntag, Robert; Reinders, Jörn; Gibmeier, Jens; Kretzer, J. Philippe

    2015-01-01

    Mechanical surface treatments have a long history in traditional engineering disciplines, such as the automotive or aerospace industries. Today, they are widely applied to metal components to increase the mechanical performance of these. However, their application in the medical field is rather rare. The present study aims to compare the potential of relevant mechanical surface treatments on the high cycle fatigue (R = 0.1 for a maximum of 10 million cycles) performance of a Ti6Al4V standard alloy for orthopedic, spinal, dental and trauma surgical implants: shot peening, deep rolling, ultrasonic shot peening and laser shock peening. Hour-glass shaped Ti6Al4V specimens were treated and analyzed with regard to the material’s microstructure, microhardness, residual stress depth profiles and the mechanical behavior during fatigue testing. All treatments introduced substantial compressive residual stresses and exhibited considerable potential for increasing fatigue performance from 10% to 17.2% after laser shock peening compared to non-treated samples. It is assumed that final mechanical surface treatments may also increase fretting wear resistance in the modular connection of total hip and knee replacements. PMID:25823001

  13. Effect of cryogenic treatment on the plastic property of Ti-6Al-4V titanium alloy

    SciTech Connect

    Gu, K. X.; Wang, J. J.; Yuan, Z.; Zhang, H.; Li, Z. Q.; Zhao, B.

    2014-01-27

    The effect of cryogenic treatment on the plastic property of Ti-6Al-4V plate was studied in the present work. After cryogenic treatment, the low temperature temper at 180 ▭ was conducted in one of the groups and the results were compared with that of the untreated and cryotreated ones. The SLX series program controlled cryogenic equipment was used for the cryogenic treatment. The tensile tests were conducted by universal tensile testing machine and parameters of elongation and area reduction were used to evaluate plastic property. The scanning electron microscope was used to study the morphology of microstructure and fracture surface. The results show that after cryogenic treatment alone the elongation increased 10.6% and the area reduction increased 13.5% while the strength reduced to a small extent. Cryogenic treatment followed with low temperature temper increased the elongation and area reduction just by the extent of 4.7% and 9.5%. It means that the additional low temperature temper after cryogenic is not beneficial to the tensile properties of Ti-6Al-4V alloy. The examination of microstructure by scanning electron microscopy revealed that cryogenic treatment reduced the content of β phase particles which is the main reason for the improvement in plasticity.

  14. Wear Resistance of AZ91D Magnesium Alloy with and Without Microarc Oxidation Coating and Ti6Al4V Alloy in Artificial Saliva

    NASA Astrophysics Data System (ADS)

    Zhang, X. P.; Zou, Y. S.; Wu, F. M.; Zhao, Z. P.; You, L.; Gu, C. F.; Liao, Y. Z.

    The wear resistances of AZ91D magnesium alloy with and without microarc oxidation (MAO) coating and Ti6Al4V alloy in artificial saliva were investigated at room temperature. The wear resistance of AZ91D magnesium alloy in artificial saliva was significantly improved after microarc oxidation treatment. The volume loss of untreated AZ91D magnesium alloy sample was 20.95 times of that of AZ91D magnesium alloy with MAO coating, and that of Ti6Al4V was 5.42 times of that of MAO. Furthermore, the wear resistance of AZ91D magnesium alloy was lower than that of Ti6Al4V alloy in artificial saliva. The wear mechanisms of AZ91D magnesium and Ti6Al4V were discussed. It was found that the wear mechanism of the MAO was associated with abrasion and microfracture. There were two dominative wear mechanisms for AZ91D alloy and Ti6Al4V alloy under the loading conditions used in the experiment, namely, micro-machining wear and deformation-induced wear.

  15. Permanent mold casting of titanium alloy Ti-6Al-4V

    SciTech Connect

    Sadayappan, M.; Sahoo, M.; Lavender, C.; paul.jablonski, P.D.

    2008-01-01

    A literature review indicated that data on the effect of various casting defects, such as inclusions and porosity, on the properties of titanium alloy castings were not readily available. This information is required to reduce the cost of fabricating titanium castings for potential automotive applications. To this end, a research project was initiated to develop data on the as-cast properties of titanium alloy Ti-6Al-4V (Ti64). Step plate castings with 3.2, 6.3, 13, and 25 mm thick steps were produced in a high-density graphite mold following melting in an induction furnace with water-cooled copper hearth. The mechanical properties were determined in the as-cast condition and were found to be close to the values reported in standards. Few casting defects such as inclusions and porosity were observed, and the loss of strength due to these defects is not significant. It is shown that titanium castings with good mechanical properties can be produced in high-density graphite molds.

  16. Surface Integrity of Titanium Alloy Ti-6Al-4 V in Ball end Milling

    NASA Astrophysics Data System (ADS)

    Mhamdi, M.-B.; Boujelbene, M.; Bayraktar, E.; Zghal, A.

    With the evolution of machine tools and the emergence of new cutting tools such as cermet, CBN; and in framework of the production of parts with complex geometry, the manufacturers were able to realize more and more parts of complex shape. The multi-axis machining is the main technique for achieving the free form; in fact the multi-axis milling with ball end tools attracts the interest of the aerospace industry and the mussel industry which continues to seek ways to improve the surface quality of finished parts. The titanium alloy is widely used in aerospace industry is the subject of this study in fact, the integrity of the surfaces of parts produced by multi-axis milling is an issue more relevant than ever for the aerospace industry. This paper aims to study the influence of the tool position and the parameters cutting precisely the speed feed Vf, the engagement of the tool on the roughness 3 D, micro-hardness and microstructure alteration created in sub-surface during the milling of concave surface of titanium alloy type Ti-6Al-4 V.

  17. Numerical Simulation and Superplastic Forming of Ti-6Al-4V Alloy for a Dental Prosthesis

    NASA Astrophysics Data System (ADS)

    Li, Xiaomei; Soo, Steven

    2011-04-01

    This article investigates superplastic forming (SPF) technique in conjunction with finite element (FE) simulation applied to dental repair. The superplasticity of Ti-6Al-4V alloys has been studied using a uniquely designed five-hole test with the aim of obtaining the modeled grain size and the flow stress parameters. The data from the five-hole test are subsequently put into the FE program for the simulation of a partial upper denture dental prosthesis (PUD4). The FE simulation of the PUD4 is carried out to set up appropriate input parameters for pressing due to the SPF process being fully automatic controlled. A variety of strain rates ranging from 2.4 × 10-5 to 1 × 10-3 s-1 are selected for the characterization of superplastic properties of the alloy. The Superflag FE program is used to generate an appropriate pressure-time profile and provide information on thickness, grain size, and grain growth rate distribution. Both membrane elements and solid elements have been adopted in the simulation and the results from both types of elements are compared. An evaluation of predicted parameters for the SPF of the prosthesis is presented.

  18. Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy

    SciTech Connect

    Kang, Guozheng; Dong, Yawei; Liu, Yujie; Jiang, Han

    2014-06-01

    The uniaxial ratchetting of Ti–6Al–4V alloy with two phases (i.e., primary hexagonal close packed (HCP) α and secondary body-centered cubic (BCC) β phases) was investigated by macroscopic and microscopic experiments at room temperature. Firstly, the effects of cyclic softening/hardening feature, applied mean stress and stress amplitude on the uniaxial ratchetting of the alloy were discussed. The macroscopic investigation of Ti–6Al–4V alloy presents obvious strain-amplitude-dependent cyclic softening, as well as a three-staged evolution curve with regard to the ratchetting strain rate. The ratchetting depends greatly on the applied mean stress and stress amplitude while the ratchetting strain increases with the increasing applied mean stress and stress amplitude. Then, the evolution of dislocation patterns and deformation twinning during the uniaxial ratchetting of two-phase Ti–6Al–4V alloy were observed using transmission electron microscopy (TEM). The microscopic observation shows that deformation twinning occurs in the primary α phase and its amount increases gradually during the uniaxial ratchetting. Simultaneously, the planar dislocation evolves from discrete lines to some dislocation nets and parallel lines with the increasing number of cycles. The deformation twinning in the primary α phase is one of main contributions to the uniaxial ratchetting of Ti–6Al–4V alloy, and should be considered in the construction of corresponding constitutive model. - Highlights: • A three-staged ratchetting occurs in the stress-controlled cyclic tests of Ti–6Al–4V alloy. • Dislocation patterns change from discrete lines to nets and parallel lines. • Deformation twinning occurs during the uniaxial ratchetting. • Both dislocation slipping and twinning are the causes of ratchetting.

  19. High-cycle fatigue behavior of Ti-5Al-2.5Sn ELI alloy forging at low temperatures

    NASA Astrophysics Data System (ADS)

    Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio; Demura, Masahiko; Matsuoka, Saburo; Sunakawa, Hideo

    2014-01-01

    High-cycle fatigue properties of Ti-5Al-2.5Sn Extra Low Interstitial (ELI) alloy forging were investigated at low temperatures. The high-cycle fatigue strength at low temperatures of this alloy was relatively low compared with that at ambient temperature. The crystallographic orientation of a facet formed at a fatigue crack initiation site was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to understand the fatigue crack initiation mechanism and discuss on the low fatigue strength at low temperature. Furthermore, in terms of the practical use of this alloy, the effect of the stress ratio (or mean stress) on the high-cycle fatigue properties was evaluated using the modified Goodman diagram.

  20. High-cycle fatigue behavior of Ti-5Al-2.5Sn ELI alloy forging at low temperatures

    SciTech Connect

    Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio; Demura, Masahiko; Matsuoka, Saburo; Sunakawa, Hideo

    2014-01-27

    High-cycle fatigue properties of Ti-5Al-2.5Sn Extra Low Interstitial (ELI) alloy forging were investigated at low temperatures. The high-cycle fatigue strength at low temperatures of this alloy was relatively low compared with that at ambient temperature. The crystallographic orientation of a facet formed at a fatigue crack initiation site was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to understand the fatigue crack initiation mechanism and discuss on the low fatigue strength at low temperature. Furthermore, in terms of the practical use of this alloy, the effect of the stress ratio (or mean stress) on the high-cycle fatigue properties was evaluated using the modified Goodman diagram.

  1. Study for Corrosion and Hydrogen Evolution Behavior of Ti-6Al-4V Alloy in Simulated Acid Rain Water

    NASA Astrophysics Data System (ADS)

    Tammam, R. H.; Fekry, A. M.

    2014-03-01

    The electrochemical behavior of Ti-6Al-4V alloy was investigated using electrochemical impedance spectroscopy (EIS) measurements at the open circuit potentials and potentiodynamic polarization measurements in a simulated acid rain containing inorganic additives. The ac circuit model for Ti-6Al-4V alloy at corrosion interface in simulated acid rain containing inorganic additives was proposed, which was based on two time constants equivalent circuit. Ti-6Al-4V alloy in a simulated acid rain of pH 1.5 containing inorganic additives showed a characteristic of a capacitive behavior. The effect of different concentrations of the inorganic additives (iodate, dichromate, phosphate, and nitrate) on the corrosion of the alloy in acid rain water (ARW) was also studied. It was found that the corrosion rate decreases drastically in the solution containing iodate, dichromate, and phosphate anions; however, nitrate anions increase the corrosion rate of the alloy. The investigated inorganic additives had inhibiting effect on the corrosion of the alloy in ARW, and their efficiency decreases according to the order: iodate > dichromate > phosphate > blank > nitrate. Polarization data results are in good agreement with EIS.

  2. Effect of SiC interlayer between Ti6Al4V alloy and hydroxyapatite films.

    PubMed

    Azem, Funda Ak; Birlik, Isil; Braic, Viorel; Toparli, Mustafa; Celik, Erdal; Parau, Anca; Kiss, Adrian; Titorencu, Irina; Vladescu, Alina

    2015-04-01

    Bioactive coatings are frequently used to improve the osseointegration of the metallic implants used in dentistry or orthopaedics. Among different types of bioactive coatings, hydroxyapatite (Ca10(PO4)6(OH)2) is one of the most extensively used due to its chemical similarities to the components of bones and teeth. In this article, production and characterization of hydroxyapatite films deposited on Ti6Al4V alloy prepared by magnetron sputtering were reported. Besides, SiC was deposited on substrate surface to study the interlayer effect. Obtained coatings were annealed at 600 °C for 30 and 120 min in a mixed atmosphere of N2 + H2O vapours with the heating rate of 12 °C min(-1). The effects of SiC interlayer and heat treatment parameters on the structural, mechanical and corrosion properties were investigated. After heat treatment process, the crystalline hydroxyapatite was obtained. Additionally, cell viability tests were performed. The results show that the presence of the SiC interlayer contributes a decrease in surface roughness and improves the mechanical properties and corrosion performance of the hydroxyapatite coatings. Biological properties were not affected by the presence of the SiC interlayer. PMID:25934259

  3. Surface Characteristics and Electrochemical Impedance Investigation of Spark-Anodized Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Garsivaz jazi, M. R.; Golozar, M. A.; Raeissi, K.; Fazel, M.

    2014-04-01

    In this study, the surface characteristic of oxide films on Ti-6Al-4V alloy formed by an anodic oxidation treatment in H2SO4/H3PO4 electrolyte at potentials higher than the breakdown voltage was evaluated. Morphology of the surface layers was studied by scanning electron microscope. The results indicated that the diameter of pores and porosity of oxide layer increase by increasing the anodizing voltage. The thickness measurement of the oxide layers showed a linear increase of thickness with increasing the anodizing voltage. The EDS analysis of oxide films formed in H2SO4/H3PO4 at potentials higher than breakdown voltage demonstrated precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. X-ray diffraction was employed to exhibit the effect of anodizing voltage on the oxide layer structure. Roughness measurements of oxide layer showed that in spark anodizing, the Ra and Rz parameters would increase by increasing the anodizing voltage. The structure and Corrosion properties of oxide layers were studied using electrochemical impedance spectroscopy (EIS) techniques, in 0.9 wt.% NaCl solution. The obtained EIS spectra and their interpretation in terms of an equivalent circuit with the circuit elements indicated that the detailed impedance behavior is affected by three regions of the interface: the space charge region, the inner compact layer, and outer porous layer.

  4. Laser ablative surface treatment for enhanced bonding of Ti-6Al-4V alloy.

    PubMed

    Palmieri, Frank L; Watson, Kent A; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J; Hopkins, John W; Connell, John W

    2013-02-01

    Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable adhesive bonds. Surface preparation by laser ablation provides an alternative to the expensive, hazardous, polluting, and less precise practices used currently such as chemical-dip, manual abrasion and grit blast. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Surface roughness and surface chemical composition were characterized using interference microscopy and X-ray photoelectron spectroscopy, respectively. A technique for fluorescence visualization was developed which allowed for quantitative failure mode analysis. Wedge crack extension testing in a hot, humid environment indicated the relative effectiveness of various surface treatments. Increasing ablation duty cycle reduced crack propagation and adhesive failure. Single lap shear testing showed an increase in strength and durability as laser ablation duty cycle and power were increased. Chemical analyses showed trends for surface chemical species, which correlated with improved bond strength and durability.

  5. Friction Stir-Welded Titanium Alloy Ti-6Al-4V: Microstructure, Mechanical and Fracture Properties

    NASA Astrophysics Data System (ADS)

    Sanders, D. G.; Edwards, P.; Cantrell, A. M.; Gangwar, K.; Ramulu, M.

    2015-05-01

    Friction stir welding (FSW) has been refined to create butt welds from two sheets of Ti-6Al-4V alloy to have an ultra-fine grain size. Weld specimen testing was completed for three different FSW process conditions: As welded, stress relieved, stress relieved and machined, and for the un-welded base material. The investigation includes macrostructure, microstructure, microhardness, tensile property testing, notched bar impact testing, and fracture toughness evaluations. All experiments were conducted in accordance with industry standard testing specifications. The microstructure in the weld nugget was found to consist of refined and distorted grains of alpha in a matrix of transformed beta containing acicular alpha. The enhanced fracture toughness of the welds is a result of increased hardness, which is attributed to an increase in alpha phase, increase in transformed beta in acicular alpha, and grain refinement during the weld process. The noted general trend in mechanical properties from as welded, to stress relieved, to stress relieved and machined conditions exhibited a decrease in ultimate tensile strength, and yield strength with a small increase in ductility and a significant increase in fracture toughness.

  6. Are new TiNbZr alloys potential substitutes of the Ti6Al4V alloy for dental applications? An electrochemical corrosion study.

    PubMed

    Ribeiro, Ana Lúcia Roselino; Hammer, Peter; Vaz, Luís Geraldo; Rocha, Luís Augusto

    2013-12-01

    The main aim of this work was to assess the electrochemical behavior of new Ti35Nb5Zr and Ti35Nb10Zr alloys in artificial saliva at 37 °C to verify if they are indicated to be used as biomaterials in dentistry as alternatives to Ti6Al4V alloys in terms of corrosion protection efficiency of the material. Electrochemical impedance spectroscopy (EIS) experiments were carried out for different periods of time (0.5-216 h) in a three-electrode cell, where the working electrode (Ti alloys) was exposed to artificial saliva at 37 °C. The near-surface region of the alloys was investigated using x-ray photoelectron spectroscopy (XPS). All alloys exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive film. Ti35Nb5Zr and Ti6Al4V alloys had their EIS results interpreted by a double-layer circuit, while the Ti35Nb10Zr alloy was modeled by a one-layer circuit. In general, the new TiNbZr alloys showed similar behavior to that observed for the Ti6Al4V. XPS results suggest, in the case of the TiNbZr alloys, the presence of a thicker passive layer containing a lower fraction of TiO2 phase than that of Ti6Al4V. After long-term immersion, all alloys develop a calcium phosphate phase on the surface. The new TiNbZr alloys appear as potential candidates to be used as a substitute to Ti6Al4V in the manufacturing of dental implant-abutment sets.

  7. Effect of creep in titanium alloy Ti-6Al-4V at elevated temperature on aircraft design and flight test

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1984-01-01

    Short-term compressive creep tests were conducted on three titanium alloy Ti-6Al-4V coupons at three different stress levels at a temperature of 714 K (825 F). The test data were compared to several creep laws developed from tensile creep tests of available literature. The short-term creep test data did not correlate well with any of the creep laws obtained from available literature. The creep laws themselves did not correlate well with each other. Short-term creep does not appear to be very predictable for titanium alloy Ti-6Al-4V. Aircraft events that result in extreme, but short-term temperature and stress excursions for this alloy should be approached cautiously. Extrapolations of test data and creep laws suggest a convergence toward predictability in the longer-term situation.

  8. Kinetic Study of the Solid-State Transformation of Vacuum-Plasma-Sprayed Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Salimijazi, H. R.; Mousavi, Z. A.; Golozar, M. A.; Mostaghimi, J.; Coyle, T.

    2014-01-01

    Because of the nature of the plasma spraying process, the physical and mechanical properties of vacuum-plasma-sprayed structures of Ti-6Al-4V alloy are completely different from those of conventionally manufactured alloys such as bulk materials from casting and forging. To obtain desired mechanical and physical properties, vacancy and internal defects must be reduced, splat boundaries must be eliminated, and optimal phase compositions should be obtained through postdeposition heat treatments. To determine appropriate heat treatment processes, one needs to study the kinetic behavior of the as-sprayed microstructure at elevated temperatures. In the current study, the kinetics of the solid transformations found in Ti-6Al-4V alloys produced during the vacuum plasma spraying process was studied based on the Johnson-Mehl-Avrami theory. For the kinetic behavior of this alloy, the nonconstant temperature dependence of the transformation rate constant exhibits an irregularity at 900 °C, marking a change in the transformation mechanism. For the lower-temperature (<900 °C) curves, the constant gradient indicates a lack of change in the transformation mechanism, including homogeneous nucleation, with growth of α phase. For higher temperatures (>900 °C), a gradient change indicates a change in the transformation mechanism. The first mechanism was the formation of α-phase grain boundary, and the second mechanism was α-plate nucleation and growth from grain boundaries. The value of the transformation rate constant in the kinetics study of as-sprayed Ti-6Al-4V alloy was much higher than for material produced by the casting method. Using the results obtained from the kinetics of the phase transformation at different constant temperatures, a time-temperature-transformation (TTT) diagram for as-sprayed Ti-6Al-4V alloy was developed.

  9. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys.

    PubMed

    Pylypchuk, Ie V; Petranovskaya, A L; Gorbyk, P P; Korduban, A M; Markovsky, P E; Ivasishin, O M

    2015-12-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)-synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  10. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie V.; Petranovskaya, A. L.; Gorbyk, P. P.; Korduban, A. M.; Markovsky, P. E.; Ivasishin, O. M.

    2015-08-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)—synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  11. In vitro biocorrosion of Ti-6Al-4V implant alloy by a mouse macrophage cell line.

    PubMed

    Lin, Hsin-Yi; Bumgardner, Joel D

    2004-03-15

    Corrosion of implant alloys releasing metal ions has the potential to cause adverse tissue reactions and implant failure. We hypothesized that macrophage cells and their released reactive chemical species (RCS) affect the alloy's corrosion properties. A custom cell culture corrosion box was used to evaluate how cell culture medium, macrophage cells and RCS altered the Ti-6Al-4V corrosion behaviors in 72 h and how corrosion products affected the cells. There was no difference in the charge transfer in the presence (75.2 +/- 17.7 mC) and absence (62.3 +/- 18.8 mC) of cells. The alloy had the lowest charge transfer (28.2 +/- 4.1 mC) and metal ion release (Ti < 10 ppb, V < 2 ppb) with activated cells (releasing RCS) compared with the other two conditions. This was attributed to an enhancement of the surface oxides by RCS. Metal ion release was very low (Ti < 20 ppb, V < 10 ppb) with nonactivated cells and did not change cell morphology, viability, and NO and ATP release compared with controls. However, IL-1beta released from the activated cells and the proliferation of nonactivated cells were greater on the alloy than the controls. In summary, macrophage cells and RCS reduced the corrosion of Ti-6Al-4V alloys as hypothesized. These data are important in understanding host tissue-material interactions.

  12. Sustained load crack growth design data for Ti-6Al-4V titanium alloy tanks containing hydrazine

    NASA Technical Reports Server (NTRS)

    Lewis, J. C.; Kenny, J. T.

    1976-01-01

    Sustained load crack growth data for Ti-6Al-4V titanium alloy in hydrazine per MIL-P-26536 and refined hydrazine are presented. Fracture mechanics data on crack growth thresholds for heat-treated forgings, aged and unaged welds, and aged and unaged heat-affected zones are reported. Fracture mechanics design curves of crack growth threshold stress intensity versus temperature are generated from 40 to 71 C.

  13. Study on the Hot Processing Parameters-Impact Toughness Correlation of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Shi, Xiaohui; Zeng, Weidong; Sun, Yu; Han, Yuanfei; Zhao, Yongqing

    2016-05-01

    In this research, the hot processing parameters-impact toughness correlation of Ti-6Al-4V titanium alloy is studied. Fifty-four groups of hot processing treatments with different forging temperatures (930, 950, 970 °C), deformation degrees (20, 50, 80%), annealing temperatures (600, 700, 800 °C), and annealing time (1 and 5 h) were conducted. The orthogonal design was used to find the primary hot processing parameters influencing the impact toughness of Ti-6Al-4V alloy. The results show that the annealing temperature can exert the biggest influence on impact toughness. Low annealing temperature is essential to achieve high impact toughness value. In addition, the BP neural network was used to describe the quantitative correlation between hot processing parameters and impact toughness. The results show that the BP neural network exhibits good performance in predicting the impact toughness of Ti-6Al-4V alloy. The prediction error is within 5%. The BP neural network and the orthogonal design method are mutually confirmed in the present work. Finally, based on the microstructure analysis, the reasons responsible for above experimental results are explained.

  14. Effects of cutting parameters on tool insert wear in end milling of titanium alloy Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Luo, Ming; Wang, Jing; Wu, Baohai; Zhang, Dinghua

    2016-06-01

    Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6Al4V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6Al4V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as: feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6Al4V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.

  15. Electrochemical characterization of albumin protein on Ti-6AL-4V alloy immersed in a simulated plasma solution.

    PubMed

    Padilla, Norma; Bronson, Arturo

    2007-06-01

    The effect of oxygen and albumin on the electrochemical behavior of a Ti-6Al-4V alloy immersed in a simulated inorganic plasma (SIP) solution was studied with a rotating-cylindrical electrode configuration to focus on the surface/electrolyte reactions. Potentiokinetic scans and electrochemical impedance spectroscopy have been used to characterize the interface by determining the passive current density and capacitance. For the polarization scans, an albumin addition of 37.7 mg/cm(3) to the SIP solution (oxygenated and unoxygenated) decreased the passive current density, indicating a lowering of the corrosive rate. The surface capacitance for the Ti-6Al-4V alloy immersed in a SIP solution averaged 13 microF/cm(2), which transformed after albumin addition (37.7 mg/cm(3)) from a potential independent behavior to the capacitance ranging from 23 to 6 microF/cm(2) with increasing potentials from -800 to 1500 mV(SCE), respectively, indicative of albumin adsorption. Within the same potential range and albumin addition to oxygenated solutions, the capacitances expanded slightly with a similar decreasing trend from 31 to 6 microF/cm(2), although the capacitance depicts an interaction between the hydrated passive film and the adsorbed albumin from -550 to 500 mV(SCE) in which the capacitance plateaued at 15 microF/cm(2). The hydrated porous oxide film results from the porous rutile layer reacting with H(2)O(2) formed as an intermediary component of oxygen reduction at the Ti-6Al-4V surface. The passive film-albumin interaction would affect the processing of titanium alloys in their surface preparation for biocompatibility, as well as determining the reactivity of titanium alloys to proteins.

  16. Surface modification of additive manufactured Ti6Al4V alloy with Ag nanoparticles: wettability and surface morphology study

    NASA Astrophysics Data System (ADS)

    Chudinova, E.; Surmeneva, M.; Koptioug, A.; Sharonova, A.; Loza, K.; Surmenev, R.

    2016-02-01

    In this work, the use of electrophoretic deposition to modify the surface of Ti6Al4V alloy fabricated via additive manufacturing technology is reported. Poly(vinylpyrrolidone) (PVP)-stabilized silver nanoparticles (AgNPs) had a spherical shape with a diameter of the metallic core of 100±20 nm and ζ -potential -15 mV. The AgNPs- coated Ti6Al4V alloy was studied in respect with its chemical composition and surface morphology, water contact angle, hysteresis, and surface free energy. The results of SEM microphotography analysis showed that the AgNPs were homogeneously distributed over the surface. Hysteresis and water contact angle measurements revealed the effect of the deposited AgNPs layer, namely an increased water contact angle and decreased contact angle hysteresis. However, the average water contact angle was 125° for PVP-stabilized-AgNPs-coated surface, whereas ethylene glycol gave the average contact angle of 17°. A higher surface energy is observed for AgNPs-coated Ti6Al4V surface (70.17 mN/m) compared with the uncoated surface (49.07 mN/m).

  17. Corrosion fatigue of steam turbine-blading alloys in operational environments. Final report. [Ti-6Al-4V

    SciTech Connect

    Cunningham, J.W.; Dowling, N.E.; Heymann, F.J.; Jonas, O.; Kunsman, L.D.; Pebler, A.R.; Swaminathan, V.P.; Willertz, L.E.; Rust, T.M.

    1984-09-01

    The corrosion fatigue strengths of Type 403 and 17-4 PH stainless steel and several processing variations of Ti-6Al-4V were determined in various steam turbine environments. Steam and turbine deposits were analyzed to establish test environments. Pure 80/sup 0/C water base line data was determined and compared to saturated aqueous solutions of NaCl, Na/sub 2/SO/sub 4/, Na/sub 3/PO/sub 4/, Na/sub 2/SiO/sub 3/ and some mixtures of these. The pH and oxygen content were also varied. Fatigue strengths at 20 kHz and 100 Hz were established for 10/sup 9/ and 10/sup 7/ cycles, respectively. The corrosion fatigue effect of notches, shot peening and mean stress were measured. Acidic, high oxygen 22% NaCl solutions were found to be extremely aggressive, causing Type 403 to lose 87% of its pure water fatigue strength; more basic solutions and other chemical species were less severe. The Ti-6Al-4V alloys were only mildly affected in most environments although NaOH plus SiO/sub 2/ was found to dissolve this alloy. The effect of the environments on 17-4 PH was intermediate between Type 403 and Ti-6Al-4V.

  18. Dissimilar-alloy laser welding of titanium: Ti6Al-4V to Beta-C{trademark}

    SciTech Connect

    Liu, P.S.; Baeslack, W.A. III; Hurley, J.

    1994-12-31

    Beta-C{sup TM} is a metastable-beta titanium alloy (nominal composition: Ti-3wt%Al-8wt%V-6wtTCr-4wt%Mo-4wt%Zr) which can be thermomechanically processed and heat treated to provide excellent combinations of strength, ductility, and fracture toughness. Recently, the increased application of metastable-beta titanium alloys in aerospace and commercial applications has resulted in the necessity to join these alloys to conventional alpha-beta titanium alloys. Based on this previous work, two approaches were considered for improving the ductility of dissimilar-alloy welds between Ti-6Al-4V and Beta-C{sup TM} in the present study: (1) application of a low heat input welding process to minimize the fusion zone and heat-affected zone (HAZ) beta grain size and (2) modification of the fusion zone chemical composition to allow greater microstructural optimization through postweld aging. CO{sub 2} laser welds were produced between Ti-6Al-4V and Beta-C{sup TM} sheet. Three different nominal fusion zone chemical compositions were obtained by varying the laser beam locations relative to the joint centerline and thereby melting different quantities of each base metal. For comparable postweld aging conditions, the laser welds exhibited ductilities superior to those of coarse-grained gas tungsten arc welds. Fracture analysis of the weld zone revealed a transition from a predominantly transgranular fracture in the low-temperature aged conditions to increasingly intergranular fracture following aging at higher temperature. This transition was promoted by an increase in the thickness and continuity of alpha phase at beta grain boundaries.

  19. Influence of Surface Pre-treatments on Laser Welding of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Sánchez-Amaya, J. M.; Amaya-Vázquez, M. R.; González-Rovira, L.; Botana-Galvin, M.; Botana, F. J.

    2014-05-01

    In the present study, Ti6Al4V samples have been welded under conduction regime by means of a high power diode laser. The main objective of the work has been to determine the actual influence of the surface pre-treatments on the laser welding process. Thus, six different pre-treatments were applied to Ti6Al4V samples before performing bead-on-plate and butt welding treatments. The depth, width, microstructure, and microhardness of the different weld zones were deeply analyzed. Grinding, sandblasting, and chemical cleaning pre-treatments lead to welds with the highest depth values, presenting high joint strengths. Treatments based on the application of dark coatings generate welds with lower penetration and worse mechanical properties, specially the graphite-based coating.

  20. Tribocorrosion mechanisms of Ti6Al4V biomedical alloys in artificial saliva with different pHs

    NASA Astrophysics Data System (ADS)

    Licausi, M. P.; Igual Muñoz, A.; Amigó Borrás, V.

    2013-10-01

    Titanium and its alloys has been widely used for the design of dental implants because of its biocompatibility, mechanical properties and corrosion resistance. The powder-metallurgy process is a promising alternative to the casting fabrication process of titanium alloys for bone implants design as the porous structure mimics the natural bone structures, allowing the bone to grow into the pores which results in a better fixation of the artificial implant. However, under in vivo conditions the implants are subjected to tribocorrosion phenomenon, which consists in the degradation mechanisms due to the combined effect of wear and corrosion. The aim of this study is to evaluate the tribocorrosion behaviour of cast and sintered Ti6Al4V biomedical alloy for dental applications using the cast material as reference. Titanium samples were tested in artificial human saliva solution with three different pHs (3, 6, 9) and in an acidic saliva with 1000 ppm fluorides (AS-3-1000F-) by different electrochemical techniques (potentiodynamic curves, potentiostatic tests and tribo-electrochemical tests). Cast and sintered titanium alloys exhibit the same tribocorrosion mechanisms in AS independently of the pH which consists in plastic deformation with passive dissolution, but the addition of fluorides to the acidified solution changes the degradation mechanism towards active dissolution of the titanium alloys.

  1. Observation of Etch-Pits and LAGB Configurations During Ambient Creep of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, Jalaj; Singh, A. K.; Raman, S. Ganesh Sundara; Kumar, Vikas

    2016-06-01

    The present work describes the microstructural features of alloy Ti-6Al-4V during constant stress creep at ambient temperature. Samples tested at 800 and 900 MPa stress levels exhibit the presence of etch-pits and/or voids. The ambient creep strain increases with an increase in applied stress due to higher strain rate sensitivity at higher stresses. A high density of low-angle grain boundaries is noticed in and around etch-pits in the creep-tested specimens due to occurrence of slip. The inverse pole figure obtained by EBSD indicates prismatic texture as the main deformation component in the creep-tested specimens.

  2. Crack-closure and crack-growth measurements in surface-flawed titanium alloy Ti6Al-4V

    NASA Technical Reports Server (NTRS)

    Elber, W.

    1975-01-01

    The crack-closure and crack-growth characteristics of the titanium alloy Ti-6Al-4V were determined experimentally on surface-flawed plate specimens. Under cyclic loading from zero to tension, cracks deeper than 1 mm opened at approximately 50 percent of the maximum load. Cracks shallower than 1 mm opened at higher loads. The correlation between crack-growth rate and the total stress-intensity range showed a lower threshold behavior. This behavior was attributed to the high crack-opening loads at short cracks because the lower threshold was much less evident in correlations between the crack-growth rates and the effective stress-intensity range.

  3. The influence of temperature on fatigue-crack growth in a mill-annealed Ti-6Al-4V alloy

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Ritter, D. L.

    1971-01-01

    To understand the influence of temperature on the rate of fatigue crack growth in high strength metal alloys, constant load amplitude fatigue crack growth experiments were carried out using a 1/4 inch thick (6.35 mm) mill-annealed Ti-6Al-4V alloy plate as a model material. The rates of fatigue crack growth were determined as a function of temperature, ranging from room temperature to about 290 C and as a function of the crack tip, stress intensity factor K, in dehumidified high purity argon environment. The dependence of the rate of fatigue crack growth on K appears to be separable into two regions. The transition correlates with changes in both the microscopic and macroscopic appearances of the fracture surfaces, and suggests a change in the mechanism and the influence of microstructure on fatigue crack growth.

  4. Effect of Interlayer Thickness on Joint Formation Between Ti-6Al-4V and Mg-AZ31 Alloys

    NASA Astrophysics Data System (ADS)

    Atieh, Anas M.; Khan, Tahir I.

    2014-11-01

    The joining of a Ti-6Al-4V alloy to a Mg-AZ31 alloy was performed using Ni electroplated coatings during the TLP bonding process. In this work, different coating thicknesses were used ranging from 1 to 20 μm. The effect of the coat thickness on microstructural developments and mechanical properties was studied. The bonded specimens were examined by metallographic examination, scanning electron microscopy, and X-ray diffraction analysis. It was observed that as the coat thickness increased from 1 to 12 μm, the joint shear strength increased from 9 to 47 MPa. A further increase in coat thickness had a detrimental effect on the bond strength, and a lower value of 11 MPa was recorded. The mechanism of joint formation includes three stages: solid-state diffusion, eutectic formation, and isothermal solidification.

  5. Compressive mechanical compatibility of anisotropic porous Ti6Al4V alloys in the range of physiological strain rate for cortical bone implant applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Huang, Tingting; Zhou, Lian

    2015-09-01

    Porous titanium and its alloys are believed to be promising materials for bone implant applications, since they can reduce the "stress shielding" effect by tailoring porosity and improve fixation of implant through bone ingrowth. In the present work, porous Ti6Al4V alloys for biomedical application were fabricated by diffusion bonding of alloy meshes. Compressive mechanical behavior and compatibility in the range of physiological strain rate were studied under quasi-static and dynamic conditions. The results show that porous Ti6Al4V alloys possess anisotropic structure with elongated pores in the out-of-plane direction. For porous Ti6Al4V alloys with 60-70 % porosity, more than 40 % pores are in the range of 200-500 μm which is the optimum pore size suited for bone ingrowth. Quasi-static Young's modulus and yield stress of porous Ti6Al4V alloys with 30-70 % relative density are in the range of 6-40 GPa and 100-500 MPa, respectively. Quasi-static compressive properties can be quantitatively tailored by porosity to match those of cortical bone. Strain rate sensitivity of porous Ti6Al4V alloys is related to porosity. Porous Ti6Al4V alloys with porosity higher than 50 % show enhanced strain rate sensitivity, which is originated from that of base materials and micro-inertia effect. Porous Ti6Al4V alloys with 60-70 % porosity show superior compressive mechanical compatibility in the range of physiological strain rate for cortical bone implant applications.

  6. Improved wear resistance of functional diamond like carbon coated Ti-6Al-4V alloys in an edge loading conditions.

    PubMed

    Choudhury, Dipankar; Lackner, Jürgen M; Major, Lukasz; Morita, Takehiro; Sawae, Yoshinori; Bin Mamat, Azuddin; Stavness, Ian; Roy, Chanchal K; Krupka, Ivan

    2016-06-01

    This study investigates the durability of functional diamond-like carbon (DLC) coated titanium alloy (Ti-6Al-4V) under edge loading conditions for application in artificial hip joints. The multilayered (ML) functional DLC coatings consist of three key layers, each of these layers were designed for specific functions such as increasing fracture strength, adapting stress generation and enhancing wear resistance. A 'ball-on-disk' multi-directional wear tester was used in the durability test. Prior to the wear testing, surface hardness, modulus elasticity and Raman intensity were measured. The results revealed a significant wear reduction to the DLC coated Ti-6Al-4V disks compared to that of non-coated Ti-6Al-4V disks. Remarkably, the counterpart Silicon Nitride (Si3N4) balls also yielded lowered specific wear rate while rubbed against the coated disks. Hence, the pairing of a functional multilayered DLC and Si3N4 could be a potential candidate to orthopedics implants, which would perform a longer life-cycle against wear caused by edge loading. PMID:27085502

  7. FEM Simulation and Experimental Validation of LBW Under Conduction Regime of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Churiaque, C.; Amaya-Vazquez, M. R.; Botana, F. J.; Sánchez-Amaya, J. M.

    2016-08-01

    Laser Beam Welding (LBW) is an advanced process to join materials with a laser beam of high energy density. LBW is especially suitable to join titanium alloys, as it allows high localization and low size of the melting pool, reducing considerably the energy of the process, in comparison with other welding technologies. Among the two widely known welding regimes, conduction and keyhole, the former is claimed to be a viable alternative to keyhole, mainly because it is a very stable process, provides high-quality welds free of defects, and involves lower laser cost. In the present work, a Finite Element Method (FEM) has been developed to simulate the LBW of Ti6Al4V alloy under conduction regime. The "Goldak double ellipsoid model" has been taken for the first time to simulate this LBW conduction process. In order to refine and validate the model, experimental conduction welding tests were performed on Ti6Al4V pieces with a high-power diode laser. Microstructural analyses and hardness measurements were also performed on the laser weld beads to identify the generated phases. Distortion and residual stresses were also obtained from the FEM simulations. An excellent agreement between the simulation and experimental results was found regarding the bead morphology and phase transformations.

  8. Enhanced Erosion Protection of TWAS Coated Ti6Al4V Alloy Using Boride Bond Coat and Subsequent Laser Treatment

    NASA Astrophysics Data System (ADS)

    Mann, B. S.; Arya, Vivek; Pant, B. K.

    2011-08-01

    The material commonly used in low-pressure high-rating super critical/ultra super critical steam turbines as well as guide and moving blades of high speed aero compressors is Ti6Al4V alloy. These blades are severely affected owing to erosion which leads to drop in efficiency and increase in maintenance cost. This article deals with SHS 7170 coating on Ti6Al4V alloy using twin wire arc spraying (TWAS), enhancing its bonding by providing a thin bond coat and then treating with high-power diode laser (HPDL). Significant improvement in erosion resistance of this multilayer coating has been achieved because of the formation of fine-grained micro structure due to rapid heating and cooling rates associated with the laser surface treatment. After laser surface treatment, the fracture toughness of this multilayer has improved manifold. The water droplet and particulate erosion test results along with the damage mechanism are reported and discussed in this article.

  9. Sustained load crack growth design data for Ti-6Al-4V titanium alloy tanks containing hydrazine

    NASA Technical Reports Server (NTRS)

    Lewis, J. C.; Kenny, J. T.

    1976-01-01

    Results are presented for an experimental study intended to provide sustained load crack growth (SLCG) data for Ti-6Al-4V titanium alloy tanks containing MIL-P-26536 hydrazine and refined hydrazine. Fracture mechanics data on crack growth threshold for heat-treated forgings, aged and unaged welds, and aged and unaged heat-affected zones (HAZ) are presented. All tests were made on uniaxially loaded fracture mechanics specimens involving part-through cracks, and an electrical discharge machined notch was used to start the crack. Fracture mechanics design curves of crack growth threshold stress intensity versus temperature are obtained for the temperature range 40-71 C. Major conclusions are that extreme susceptibility to SLCG in hydrazine is a universal property of unaged weld metal in Ti-6Al-4V titanium alloy of normal interstitial content, and that aging both weld metal and HAZ at 510 C for 4 hr after welding completely removes all susceptibility to SLCG induced by hydrazine, with less susceptibility to SLCG in refined hydrazine.

  10. Strain localization during tensile Hopkinson bar testing of commercially pure titanium and Ti6Al4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Moćko, Wojciech; Kruszka, Leopold; Brodecki, Adam

    2015-09-01

    The goal of the analysis was to determine the strain localization for various specimen shapes (type A and type B according to PN-EN ISO 26203-1 standard) and different loading conditions, i.e. quasi- static and dynamic. Commercially pure titanium (Grade 2) and titanium alloy Ti6Al4V (Grade 5) were selected for the tests. Tensile loadings were applied out using servo-hydraulic testing machine and tensile Hopkinson bar with pre-tension. The results were recorded using ARAMIS system cameras and fast camera Phantom V1210, respectively at quasi-static and dynamic loading conditions. Further, specimens outline was determined on the basis of video data using TEMA MOTION software. The strain distribution on the specimen surface was estimated using digital image correlation method. The larger radius present in the specimen of type B in comparison to specimen of type A, results in slight increase of the elongation for commercially pure titanium at both quasi-static and dynamic loading conditions. However this effect disappears for Ti6Al4V alloy. The increase of the elongation corresponds to the stronger necking effect. Material softening due to increase of temperature induced by plastic work was observed at dynamic loading conditions. Moreover lower elongation at fracture point was found at high strain rates for both materials.

  11. FEM Simulation and Experimental Validation of LBW Under Conduction Regime of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Churiaque, C.; Amaya-Vazquez, M. R.; Botana, F. J.; Sánchez-Amaya, J. M.

    2016-07-01

    Laser Beam Welding (LBW) is an advanced process to join materials with a laser beam of high energy density. LBW is especially suitable to join titanium alloys, as it allows high localization and low size of the melting pool, reducing considerably the energy of the process, in comparison with other welding technologies. Among the two widely known welding regimes, conduction and keyhole, the former is claimed to be a viable alternative to keyhole, mainly because it is a very stable process, provides high-quality welds free of defects, and involves lower laser cost. In the present work, a Finite Element Method (FEM) has been developed to simulate the LBW of Ti6Al4V alloy under conduction regime. The "Goldak double ellipsoid model" has been taken for the first time to simulate this LBW conduction process. In order to refine and validate the model, experimental conduction welding tests were performed on Ti6Al4V pieces with a high-power diode laser. Microstructural analyses and hardness measurements were also performed on the laser weld beads to identify the generated phases. Distortion and residual stresses were also obtained from the FEM simulations. An excellent agreement between the simulation and experimental results was found regarding the bead morphology and phase transformations.

  12. Further Investigation Into the Use of Laser Surface Preparation of Ti-6Al-4V Alloy for Adhesive Bonding

    NASA Technical Reports Server (NTRS)

    Palmieri, Frank L.; Crow, Allison; Zetterberg, Anna; Hopkins, John; Wohl, Christopher J.; Connell, John W.; Belcher, Tony; Blohowiak, Kay Y.

    2014-01-01

    Adhesive bonding offers many advantages over mechanical fastening, but requires robust materials and processing methodologies before it can be incorporated in primary structures for aerospace applications. Surface preparation is widely recognized as one of the key steps to producing robust and predictable bonds. This report documents an ongoing investigation of a surface preparation technique based on Nd:YAG laser ablation as a replacement for the chemical etch and/or abrasive processes currently applied to Ti-6Al-4V alloys. Laser ablation imparts both topographical and chemical changes to a surface that can lead to increased bond durability. A laser based process provides an alternative to chemical-immersion, manual abrasion, and grit blast process steps which are expensive, hazardous, environmentally unfriendly, and less precise. In addition, laser ablation is amenable to process automation, which can improve reproducibility to meet quality standards for surface preparation. An update on work involving adhesive property testing, surface characterization, surface stability, and the effect of laser surface treatment on fatigue behavior is presented. Based on the tests conducted, laser surface treatment is a viable replacement for the immersion chemical surface treatment processes. Testing also showed that the fatigue behavior of the Ti-6Al-4V alloy is comparable for surfaces treated with either laser ablation or chemical surface treatment.

  13. A novel constitutive model for hot deformation behaviors of Ti-6Al-4V alloy based on probabilistic method

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Zhao, Chun-Yang; Chen, Ming-Song; Chen, Dong-Dong

    2016-08-01

    The flow behaviors of Ti-6Al-4V alloy are studied by isothermal compressive experiments at the deformation temperature from 850 to 950 °C and strain rate from 0.001 to 1 s-1. To analyze the uncertainties induced by material itself and testing procedure, repetitive compressive tests are conducted under each experimental condition. It is found that the uncertainties of flow behaviors are too great to be ignored. The innovation of the study is that the probability theory is introduced to model flow behaviors. 312 (=531,441) sets of flow curves are created by the resampling method, in which 10,000 sets are used to determine the material parameters of constitutive equations. Therefore, the probability densities of material parameters can be easily obtained. It is found that the probability density functions of the most material parameters are similar to the normal distribution. The values of material parameters with the maximum probability density are selected for the established constitutive model. The advantage of the established constitutive model is that it can describe the most probable flow characteristics of Ti-6Al-4V alloy.

  14. The comparison of phosphate-titanate-silicate layers on the titanium and Ti6Al4V alloy base

    NASA Astrophysics Data System (ADS)

    Rokita, M.

    2011-08-01

    The studied layers were composed of two parts: titanate-silicate underlayer for better adhesion and titanate-phosphate-silicate layers for potential bioparameters. The layers with different amounts of hydroxyapatite were deposited on titanium and Ti6Al4V alloy substrates using dipping sol-gel method and electrophoresis. The selection of sol/suspension composition, deposition time and heat treatment conditions have the decisive influence on the layers parameters. The obtained layers should be very thin and almost amorphous. The specific nature of ceramic layers on the metal substrates excludes the use of some measurements methods or makes it difficult to interpret the measurement results. All the obtained samples were compared using XRD analysis data (GID technique), SEM with EDX measurements and FTIR spectroscopy (transmission and reflection techniques) before and after soaking in simulated body fluid. FTIR spectroscopy with mathematical treatment of the spectra (BIO-RAD Win-IR program, Arithmetic-subtract function) was used to detect the increase or decrease of any phosphate phases during SBF soaking. Based on the FTIR results the processes of hydroxyapatite (HAp) growth or layer dissolution were estimated. The layers deposited on titanium substrate are more crystalline then the ones deposited on Ti6Al4V. During SBF soaking process the growth of small amount of microcrystalline carbonate hydroxyapatite was observed on titanium substrate. The layer on Ti6Al4V base contained amorphous carbonate apatite. During heating treatment above about 870-920 K this apatite transforms into carbonate hydroxyapatite. The Ti6Al4V substrate seems to be more advantageous in context of potentially bioactive materials obtaining.

  15. Electrochemical behavior of 45S5 bioactive ceramic coating on Ti6Al4V alloy for dental applications

    NASA Astrophysics Data System (ADS)

    Machado López, M. M.; Espitia Cabrera, M. I.; Faure, J.; Contreras García, M. E.

    2016-04-01

    Titanium and its alloys are widely used as implant materials because of their mechanical properties and non-toxic behavior. Unfortunately, they are not bioinert, which means that they can release ions and can only fix the bone by mechanical anchorage, this can lead to the encapsulation of dense fibrous tissue in the body. The bone fixation is required in clinical conditions treated by orthopedic and dental medicine. The proposal is to coat metallic implants with bioactive materials to establish good interfacial bonds between the metal substrate and bone by increasing bioactivity. Bioactive glasses, ceramics specifically 45 S5 Bioglass, have drawn attention as a serious functional biomaterial because osseointegration capacity. The EPD method of bioglass gel precursor was proposed in the present work as a new method to obtain 45S5/Ti6A14V for dental applications. The coatings, were thermally treated at 700 and 800°C and presented the 45 S5 bioglass characteristic phases showing morphology and uniformity with no defects, quantification percentages by EDS of Si, Ca, Na, P and O elements in the coating scratched powders, showed a good proportional relationship demonstrating the obtention of the 45S5 bioglass. The corrosion tests were carried out in Hank's solution. By Tafel extrapolation, Ti6Al4V alloy showed good corrosion resistance in Hank's solution media, by the formation of a passivation layer on the metal surface, however, in the system 45S5/Ti6Al4V there was an increase in the corrosion resistance; icon-, Ecorr and corrosion rate decreased, the mass loss and the rate of release of ions, were lower in this system than in the titanium alloy without coating.

  16. Finite Element Simulation of Machining of Ti6Al4V Alloy

    SciTech Connect

    Rizzuti, S.; Umbrello, D.

    2011-05-04

    Titanium and its alloys are an important class of materials, especially for aerospace applications, due to their excellent combination of strength and fracture toughness as well as low density. However, these materials are generally regarded as difficult to machine because of their low thermal conductivity and high chemical reactivity with cutting tool materials. Moreover, the low thermal conductivity of Titanium inhibits dissipation of heat within the workpiece causing an higher temperature at the cutting edge and generating for higher cutting speed a rapid chipping at the cutting edge which leads to catastrophic failure. In addition, chip morphology significantly influences the thermo-mechanical behaviour at the workpiece/tool interface, which also affects the tool life.In this paper a finite element analysis of machining of TiAl6V4 is presented. In particular, cutting force, chip morphology and segmentation are taken into account due to their predominant roles to determine machinability and tool wear during the machining of these alloys. Results in terms of residual stresses are also presented. Moreover, the numerical results are compared with experimental ones.

  17. Electrochemical Evaluation of Nanocrystalline Diamond Thin Films on Ti-6Al-4V Implant Alloy

    NASA Astrophysics Data System (ADS)

    Fries, Marc; Venugopalan, Ramakrishna; Vohra, Yogesh

    2002-03-01

    Some 186,000 hip replacement surgeries are peformed every year in the United States alone. About 10surgeries are revision operations to replace an implant that has most likely failed through mechanical-electrochemical interactions resulting in implant wear. The ability to enhance the resistance to such mechanical-electrochemical interaction and thereby reduce wear could result in significantly increased device lifespan. Nanocrystalline diamond (NCD) thin films were deposited on Ti-6Al-4V disk samples (processed per ASTM F86 standard for medical implant surface conditions) using microwave plasma chemical vapor deposition (MPCVD). As a first step, these samples (n=3/test per group) were subjected to electrochemical evaluation in inorganic neutral salt solution at 37 C. The electrochemical evaluation involved both impedence spectroscopy (per ASTM G106) and polarization testing (per ASTM G5). The impedence spectroscopy data indicated a significantly higher charge transfer resistance at the interface due to the protective NCD as compared to the bare or uncoated substrate. The polarization test data confirmed that this increased charge transfer resistance resulted in a decreased current density measurement. This decreased current density measurement resulted in an order of magnitude lower calculated static corrosion rate from the NCD coated samples as opposed to the uncoated controls. Future studies will focus on investigations that will facilitate transfer of these static electrochemical resistance results to a more relevant mechanical-electrochemical interaction milieu.

  18. Effects of hydrogen on ELI titanium alloy Ti-5Al-2.5Sn

    NASA Technical Reports Server (NTRS)

    Chandler, W. T.; Hensley, W. E.

    1970-01-01

    Tensile tests on titanium alloy, following abrasion under hydrogen and temperature cycling, reveal lowered tensile strength, increased ductility, and no embrittlement. Fretting the metal on itself in flowing hydrogen or abrading with an iron file in flowing hydrogen produces titanium hydride.

  19. Mechanical Properties and High Temperature Oxidation Behavior of Ti-Al Coating Reinforced by Nitrides on Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Dai, Jingjie; Yu, Huijun; Zhu, Jiyun; Weng, Fei; Chen, Chuanzhong

    2016-05-01

    Ti-Al alloyed coating reinforced by nitrides was fabricated by laser surface alloying technique to improve mechanical properties and high temperature oxidation resistance of Ti-6Al-4V titanium alloy. Microstructures, mechanical properties and high temperature oxidation behavior of the alloyed coating were analyzed. The results show that the alloyed coating consisted of Ti3Al, TiAl2, TiN and Ti2AlN phases. Nitrides with different morphologies were dispersed in the alloyed coating. The maximum microhardness of the alloyed coating was 906HV. The friction coefficients of the alloyed coating at room temperature and high temperature were both one-fourth of the substrate. Mass gain of the alloyed coating oxidized at 800∘C for 1000h in static air was 5.16×10-3mg/mm2, which was 1/35th of the substrate. No obvious spallation was observed for the alloyed coating after oxidation. The alloyed coating exhibited excellent mechanical properties and long-term high temperature oxidation resistance, which improved surface properties of Ti-6Al-4V titanium alloy significantly.

  20. Effect of PostNitride Annealing on Wear and Corrosion Behavior of Titanium Alloy Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Anandan, C.; Mohan, L.

    2016-10-01

    Titanium alloy, Ti-6Al-4V, was plasma nitrided using RF plasma with 100% N at 800 °C and annealed at 850 °C in vacuum. XRD and XPS studies show the formation of titanium nitrides after nitriding and redistribution of nitrogen after annealing. Potentiodynamic polarization and electrochemical impedance spectroscopy studies in Hank's solution show that nitriding decreases the corrosion resistance of the substrate and postnitride annealing improves the corrosion resistance of the nitrided samples. After nitriding, wear rate has decreased by an order of magnitude in reciprocating wear experiments and decreased further in annealed samples in comparison with that of substrate. Thus, postnitride annealing improves both corrosion and wear resistance of the nitrided sample. These improvements are attributed to redistribution of nitrogen and formation of a thin oxide layer on the sample due to annealing.

  1. Effect of n-implantation on the corrosive-wear properties of surgical Ti-6Al-4V alloy

    SciTech Connect

    Williams, J.M.; Beardsley, G.M.; Buchanan, R.A.; Bacon, R.K.

    1984-01-01

    The effects of N-ion implantation on the corrosive-wear properties of Ti-6Al-4V, an alloy used for construction of the femoral component of artificial hip joints in humans, were tested. In corrosive-wear tests designed to simulate pertinent hip-joint parameters, electrochemical corrosion currents were measured for cylindrical samples in saline electrolyte in an arrangement which allowed the samples to be rotated between loaded polyethylene pads simultaneously with the current measurement. To further quantify material removal, Zr markers were ion-implanted into some samples so that, by use of Rutherford backscattering, material removal could be detected by changes in position of the marker relative to the surface. Corrosion currents were greatly reduced by implantation of approximately 20 at. % N, but even implantation of the Zr markers also reduced corrosion currents. The marker experiments confirmed the low rate of material removal for the implanted samples. 10 references, 5 figures, 1 table.

  2. Effects of laser peening on residual stresses and fatigue crack growth properties of Ti-6Al-4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Zhou, J. Z.; Huang, S.; Zuo, L. D.; Meng, X. K.; Sheng, J.; Tian, Q.; Han, Y. H.; Zhu, W. L.

    2014-01-01

    The effects of laser peening (LP) with different laser peening coverage rates on residual stresses and fatigue crack growth (FCG) properties of Ti-6Al-4V titanium alloy were investigated. Residual stresses after LP and micro-structure with different fatigue striation patterns on fracture cross-sections were analyzed. Compressive residual stresses and dense dislocation arrangements can be obtained in the superficial layer after LP. The influence of compressive residual stresses induced under different LP coverage rates on FCG properties was revealed. LP coverage rate had an apparent influence on FCG properties as confirmed by the fatigue striation spacing on fracture cross-sections. Moreover, FCG rate decreased with the increase of compressive residual stresses perpendicular to the crack growth direction, which indicated that LP had an obvious inhibitory effects on FCG.

  3. Constitutive Model Modification of Titanium Alloy Ti-6Al-4V Based on Dislocation Pile-up Theory

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-Chuan; Zhou, Tian-Feng; Che, Jiang-Tao; Liang, Zhi-Qiang; Wang, Xi-Bin

    2016-05-01

    Through the Split Hopkinson Pressure Bar (SHPB) test and the quasi-static tensile test on non-standard specimen of titanium alloy Ti-6Al-4V, the rules of the mechanical property changing with the specimen size under different temperatures are summarized, and the parameters of the classical constitutive Johnson-Cook (JC) model are determined. Based on the dislocation pile-up theory, the classical constitutive JC model is modified by considering the influence of grain size, and the modified JC model is established by adding a functional term Δσ into the classical constitutive model to describe the influence of the grain. The tensile testis analyzed by the finite element method (FEM) simulation. Comparing with the experimental results, the simulation results based on the modified JC model show much better accuracy than that by the classical JC model.

  4. Formation mechanism of linear friction welded Ti-6Al-4V alloy joint based on microstructure observation

    SciTech Connect

    Ma Tiejun; Chen Tao Li Wenya; Wang Shiwei; Yang Siqian

    2011-01-15

    The microstructure of the linear friction welded Ti-6Al-4V titanium alloy joint was investigated by optical microscope, scanning electronic microscope and transmission electron microscope. Results show that the dynamic recovery and recrystallization resulting from the intensive plastic deformation and fast heating and cooling processes during linear friction welding account for the superfine {alpha} + {beta} grains in the weld center. Fine {alpha} grains distribute in the {beta} matrix or at the boundaries of {beta} grains. A mass of dislocations networks and metastructures present within the {alpha} and {beta} grains. - Research Highlights: {yields} TEM is employed in the analysis. {yields} The dynamic recovery is the main mechanism in thermal deformation of TC4. {yields} Superfine grains in the weld result from dynamic recovery and dynamic recrystallizaion, but the recrystallization is inadequate.

  5. Effect of PostNitride Annealing on Wear and Corrosion Behavior of Titanium Alloy Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Anandan, C.; Mohan, L.

    2016-08-01

    Titanium alloy, Ti-6Al-4V, was plasma nitrided using RF plasma with 100% N at 800 °C and annealed at 850 °C in vacuum. XRD and XPS studies show the formation of titanium nitrides after nitriding and redistribution of nitrogen after annealing. Potentiodynamic polarization and electrochemical impedance spectroscopy studies in Hank's solution show that nitriding decreases the corrosion resistance of the substrate and postnitride annealing improves the corrosion resistance of the nitrided samples. After nitriding, wear rate has decreased by an order of magnitude in reciprocating wear experiments and decreased further in annealed samples in comparison with that of substrate. Thus, postnitride annealing improves both corrosion and wear resistance of the nitrided sample. These improvements are attributed to redistribution of nitrogen and formation of a thin oxide layer on the sample due to annealing.

  6. Surface treatment by electric discharge machining of Ti-6Al-4V alloy for potential application in orthopaedics.

    PubMed

    Harcuba, Petr; Bačáková, Lucie; Stráský, Josef; Bačáková, Markéta; Novotná, Katarína; Janeček, Miloš

    2012-03-01

    This study investigated the properties of Ti-6Al-4V alloy after surface treatment by the electric discharge machining (EDM) process. The EDM process with high peak currents proved to induce surface macro-roughness and to cause chemical changes to the surface. Evaluations were made of the mechanical properties by means of tensile tests, and of surface roughness for different peak currents of the EDM process. The EDM process with peak current of 29 A was found to induce sufficient surface roughness, and to have a low adverse effect on tensile properties. The chemical changes were studied by scanning electron microscopy equipped with an energy dispersive X-ray analyser (EDX). The surface of the benchmark samples was obtained by plasma-spraying a titanium dioxide coating. An investigation of the biocompatibility of the surface-treated Ti-6Al-4V samples in cultures of human osteoblast-like MG 63 cells revealed that the samples modified by EDM provided better substrates for the adhesion, growth and viability of MG 63 cells than the TiO2 coated surface. Thus, EDM treatment can be considered as a promising surface modification to orthopaedic implants, in which good integration with the surrounding bone tissue is required.

  7. Surface modification of Ti-6Al-4V alloy for biomineralization and specific biological response: Part I, inorganic modification.

    PubMed

    Ferraris, S; Spriano, S; Pan, G; Venturello, A; Bianchi, C L; Chiesa, R; Faga, M G; Maina, G; Vernè, E

    2011-03-01

    Titanium and its alloys represent the gold standard for orthopaedic and dental prosthetic devices, because of their good mechanical properties and biocompatibility. Recent research has been focused on surface treatments designed to promote their rapid osteointegration also in case of poor bone quality. A new surface treatment has been investigated in this research work, in order to improve tissue integration of titanium based implants. The surface treatment is able to induce a bioactive behaviour, without the introduction of a coating, and preserving mechanical properties of Ti6Al4V substrates (fatigue resistance). The application of the proposed technique results in a complex surface topography, characterized by the combination of a micro-roughness and a nanotexture, which can be coupled with the conventional macro-roughness induced by blasting. Modified metallic surfaces are rich in hydroxyls groups: this feature is extremely important for inorganic bioactivity (in vitro and in vivo apatite precipitation) and also for further functionalization procedures (grafting of biomolecules). Modified Ti6Al4V induced hydroxyapatite precipitation after 15 days soaking in simulated body fluid (SBF). The process was optimised in order to not induce cracks or damages on the surface. The surface oxide layer presents high scratch resistance.

  8. Preparation, corrosion resistance and hemocompatibility of the superhydrophobic TiO2 coatings on biomedical Ti-6Al-4V alloys

    NASA Astrophysics Data System (ADS)

    Jiang, J. Y.; Xu, J. L.; Liu, Z. H.; Deng, L.; Sun, B.; Liu, S. D.; Wang, L.; Liu, H. Y.

    2015-08-01

    In this paper the micro-arc oxidation (MAO) technique and subsequent superhydrophobic treatment were applied to fabricate the superhydrophobic TiO2 coatings on biomedical Ti-6Al-4V alloys. The surface morphology, surface roughness, water contact angle, corrosion resistance and hemocompatibility of the MAO and superhydrophobic samples were investigated. The results showed that the single anatase TiO2 coating was formed on the surface Ti-6Al-4V alloy with rough and porous micrometer-scale structure. The low surface energy film was grafted on the surface of the TiO2 coating by self-assembling reaction during the hydrophobic treatment process, which resulted in the formation of superhydrophobic surfaces with the water contact angle of 153.39°. It was found that the corrosion resistance of the superhydrophobic samples increased by one order of magnitude compared to those of the uncoated Ti-6Al-4V alloys. The hemolysis ratio and platelets adhesion characteristics of the Ti-6Al-4V alloys were also improved greatly through the MAO treatment and subsequent superhydrophobic treatment. Especially, no platelet could be observed on the surface of the superhydrophobic samples. Therefore, the superhydrophobic TiO2 coatings of Ti-6Al-4V alloys with higher hemocompatibility would show great promise in their potential blood-contacting applications.

  9. Effect of heat treatment on microstructures and mechanical properties of a Ti-6Al-4V alloy rod prepared by powder compact extrusion

    NASA Astrophysics Data System (ADS)

    Yang, Fei; Gabbitas, Brian

    2015-03-01

    In this paper, Ti-6Al-4V alloy rods were manufactured by the powder compact extrusion of a powder mixture of hydride-dehydride (HDH) titanium powder, elemental aluminum powder and master alloy powder. Extrusions were carried out at 1300°C and with a holding time of 5 min in an argon atmosphere. The effects of different heat treatments (HT1: 960°C/1 h, water quenching, HT2: 960°C/1 h, water quenching + 500°C/6 h, air cooling, HT3: 850°C/2 h, furnace cooling to 540°C, then air cooling) on the microstructure and mechanical properties of as-extruded Ti-6Al-4V alloy rods were investigated. The results showed that a homogeneous microstructure, composed of a lamellar structure with a grain size range of 40-60 μm, was produced by powder compact extrusion of a powder mixture. The mechanical properties achieved were an ultimate tensile strength (UTS) of 1254 MPa, a yield strength (YS) of 1216 MPa and 8% ductility. After quenching at 960°C and with a holding time of 1 h, the UTS and YS of the heat treated Ti-6Al-4V alloy rod were increased to 1324 MPa and 1290 MPa, and the ductility was increased to 12%. After HT2, the UTS and YS of the heat treated Ti-6Al-4V alloy rod were significantly increased to 1436 MPa and 1400 MPa, but the ductility decreased to 4%. After HT3, the mechanical properties of the heat treated Ti-6Al-4V alloy rod were slightly decreased to give a UTS of 1213 MPa and a YS of 1180 MPa, with an increase in ductility to 11%. The microstructural changes of as-extruded Ti-6Al-4V alloy rods were also investigated for the different heat treatments.

  10. Preparation of conversion coating on Ti-6Al-4V alloy in mixed solution of phytic acid and ammonium fluoride through chemical modification

    NASA Astrophysics Data System (ADS)

    Li, Lanlan; He, Jian; Yang, Xu

    2016-05-01

    Conversion coatings on Ti-6Al-4V alloy was prepared through chemical modification in phytic acid and ammonium fluoride mixed solution. The influences of pH, time and the composition of solution on the microstructure of alloy surface were investigated. Scanning electron microscopy was used to observe the microstructure. The chemical composition of alloy surface before and after modification was investigated by energy dispersive X-ray spectroscopy. The results indicated that a conversion coating could be formed on the Ti-6Al-4V alloy in a mixed solution of phytic acid and ammonium fluoride, the growth and microstructure of the conversion coatings were critically dependent on the pH, time and concentration of phytic acid and ammonium fluoride. In 100 mg/ml phytic acid containing 125 mg/ml ammonium fluoride solution with a pH of 6, a compact conversion coating with the thickness of about 4.7 μm formed after 30 min immersion on Ti-6Al-4V alloy surface. The preliminary evaluation of bioactivity of conversion coating was performed by in vitro cell experiments. The results showed that this chemical modification method is a promising surface modification technique for Ti-6Al-4V alloy inplants.

  11. Evaluation of cast titanium alloy compressor components. Volume I. Final report May 76-Aug 78. [Ti-6Al-4V

    SciTech Connect

    Hammer, A.N.

    1981-11-01

    The objective of this program was to characterize the properties of cast titanium alloy compressor impellers to provide a background for design, processing, and qualification for service in the Solar T62T-40 Titan auxiliary power unit and similar small radial gas turbine engines. Four titanium alloy investment casting foundries participated in the production of straight vane test wheels, a low-cost representation of the compressor impellers. As-cast and hot isostatic pressed (HIPed) Ti-6A1-4V was seen to have less than half the high cycle fatigue strength (20 to 30 ksi versus 60 ksi) of equvalent sections from forged and machined impellers. A modified solution heat treatment and aging cycle was developed which restored the fatigue strength to approximately 50 ksi, and which provided adequate tensile strength and ductility. High cycle fatigue strength of weld repaired vanes was significantly lower than that of unwelded, however. Cast and machined wheels offer substantial cost savings over wheels conventionally machined from forgings. These savings may be as much as 50%, or about $900 per wheel.

  12. Formation of bioactive functionally graded structure on Ti-6Al-4V alloy by chemical surface treatment.

    PubMed

    Kim, H M; Takadama, H; Miyaji, F; Kokubo, T; Nishiguchi, S; Nakamura, T

    2000-09-01

    An Al- and V-free sodium titanate hydrogel layer with a graded structure where the sodium titanate gradually decreases toward the interior, was formed on the surface of Ti-6Al-4V alloy, when the alloy was exposed to 5M NaOH solution at 60 degrees C for 24 h. This gel layer was transformed into an amorphous sodium titanate layer without giving considerable change in the graded structure, except a little increase in the depth of the oxygen distribution by a heat treatment at 600 degrees C for 1 h. The sodium titanate layer formed Ti-OH groups on its surface by exchanging its Na+ ion with H3O+ ion in simulated body fluid when soaked in the fluid, and thus formed Ti-OH groups induced the apatite nucleation. The apatite layer also formed a graded structure toward the substrate. The strong bond of the apatite layer to the substrate was attributed to this graded structure.

  13. The effect of annealing on the Knoop microhardness of nitrogen implanted Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Nath, V. C.; Sood, D. K.; Manory, R. R.

    1991-07-01

    The implantation of the Ti6Al4V alloy with nitrogen has been previously studied, and the treatment has been shown to improve the microhardness significantly [R.G. Vardiman, Defect and Diffusion Forum 57/58 (1988) 135, and references therein]. The effects of post-implantation annealing on the properties has not been studied systematically, and this is the principal aim of the RMIT work. Initial results of this study are presented and discussed. It was found that N + implantation of this alloy at 80 keV with fluences varying in the range (0.5-1.5) × 10 17ions/cm 2 caused an improvement in Knoop hardness up to 100%. Rutherford backscattering results show a buried layer containing up to 25% nitrogen in the as-implanted specimens at a depth of 130 nm. After annealing the sample implanted with 1.5 × 10 17 at 705°C, both the nitrogen concentration and the depth of the layer decrease to approximately half of their as-implanted values. The observed reduction in hardness can be attributed to the decrease in the nitrogen concentration of the buried layer, as well as to repair of the lattice. These results may indicate that only a limited amount of TiN forms directly during implantation.

  14. Study on Variants of Solution Treatment and Aging Cycle of Titanium Alloy Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Gupta, R. K.; Kumar, V. Anil; Chhangani, Sumit

    2016-04-01

    Ti6Al4V with two different chemical compositions, one rich and the other lean in α-stabilizer oxygen were selected to study the effect of quench severity during solution treatment and their aging response. These two coupons were taken from two differently processed wrought products viz. rolled ring and closed die forging. The coupons were then subjected to solution treatment followed by employing different cooling rates to vary the quench severity and different aging treatments by changing the aging temperature and time. The microstructure and mechanical properties thus obtained are correlated with respect to the heat treatment conditions. It is noted that there is a significant increase in strength of the alloy retaining the ductility when it is aged in the aging temperature regime of 550-650 °C and time of 8 h. Role of higher oxygen content is noted, which is more pronounced with higher severity of quench (by water quenching). Specimens representative of different heat treatment conditions were characterized using optical microscope, electron back-scattered diffraction, and electron microscope. The presence of martensitic (α') structure along with uniform distribution of fine primary α, secondary α precipitates and refined β-grains, twins in the microstructure helps in improving the strength of the material. Also, during high temperature aging of 700 °C, which incidentally falls in the range of annealing temperature of the alloy, overaging occurs which is similar to effect of annealing and hence retains the ductility as well.

  15. Bioactivity of Ti-6Al-4V alloy implants treated with ibandronate after the formation of the nanotube TiO2 layer.

    PubMed

    Moon, So-Hee; Lee, Seung-Jae; Park, Il-Song; Lee, Min-Ho; Soh, Yun-Jo; Bae, Tae-Sung; Kim, Hyung-Seop

    2012-11-01

    Nanostructure surface of titanium implants treated with anodic oxidation, heat, and bisphosphonates, has been introduced to improve osseointegration of the implants. However, no information could be found about the efficiency of these approaches on Ti-6Al-4V alloy surfaces. This study examined the drug loading capacity of anodized nanotubular Ti-6Al-4V alloy surfaces in vitro as well as the bone response to surface immobilized bisphosphonates (BPs) on anodized nanotubular Ti-6Al-4V alloy surface in tibiae of rats. Ti-6Al-4V alloy titanium was divided into two groups: (1) control group (nontreated); (2) test group (anodized, heat-, and bisphosphonate-treated group). In vitro, amount of the drug released from the both groups' specimens was examined; all samples were 1 × 2 cm in size. In vivo, the 10 implants were placed inside of tibias of five rats. After 4 weeks, the bone response of the implants was evaluated using a removal torque test, and measuring bone contact and bone area. In addition, the surfaces of the extracted implants were observed by FE-SEM and EDS. In vitro, the drug loading capacity of the Ti-6Al-4V alloy surfaces was enhanced by anodizing surface modification. The values of the removal torque, bone contact, and bone area were significantly higher in the test group (p < 0.05). Furthermore, according to the EDS analysis, the amounts of Ca and P on the surface of the extracted implants were higher in the test group. Within the limits of this experiment, results of this research demonstrated that bisphosphonate-treated Ti-6Al-4V alloy implants with nanotubular surfaces have positive effects in bone-to-implant contact.

  16. Microstructure and wear properties of WC particle reinforced composite coating on Ti6Al4V alloy produced by the plasma transferred arc method

    NASA Astrophysics Data System (ADS)

    Çelik, Osman Nuri

    2013-06-01

    The microstructure and wear properties of a WC particle reinforced composite coating produced by the plasma transferred arc (PTA) method on Ti6Al4V alloy were investigated in this study. PTA processing was carried out using argon as the plasma gas at arc current values of 70 A, 80 A and 90 A. Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to characterize the microstructure of the composite layer formed on the surface of a Ti6Al4V substrate. The results indicate that the WC, TiC and W2C carbide phases formed in the composite layers produced by PTA on the surface of the Ti6Al4V alloy. The distributions and volume fractions of these phases were found to vary with the arc current values. Wear tests were performed under dry sliding conditions using a linear ball-on-disc geometry. The microhardness and wear resistances of all of the composite layers produced by the PTA process were enhanced relative to those of the Ti6Al4V substrate. The homogeneity and volume fractions of the carbide phases in the composite layers were responsible for the improvement in the wear resistance of the alloy. The wear test results indicate that the alloy modified at 70 A shows better wear resistance than the alloys modified at 80 A and 90 A.

  17. Effect of laser power on the microstructural behaviour and strength of modified laser deposited Ti6Al4V+Cu alloy for medical application

    NASA Astrophysics Data System (ADS)

    Erinosho, Mutiu F.; Akinlabi, Esther T.

    2016-03-01

    The excellent biocompatibility property of Grade 5 titanium alloy has made its desirability largely increasing in the field of biomedical. The titanium alloy (Ti6Al4V) was modified with the addition of 3 weight percent (wt %) copper via a laser deposition process using the Ytterbium fiber laser with a wavelength of 1.047 μm. Therefore, this paper presents the effect of laser power on the microstructural behaviour and strength of the modified Ti6Al4V+Cu alloy. The laser powers were varied between 600 W and 1600 W respectively while all other parameters such as the scanning speed, powder flow rates and gas flow rates were kept constant. The melt pool and width of the deposited alloy increases as the laser power was increased. The α-lamella was observed to be finer at low laser power, and towards the fusion zone, Widmanstettan structures were fused and become smaller; and showing an evidence of α-martensite phases. The strength of the modified alloy was derived from the hardness values. The strength was observed to increase initially to a point as the laser power increases and afterwards decreased as the laser power was further increased. The improved Ti6Al4V+Cu alloy can be anticipated for biomedical application.

  18. A Modified Johnson-Cook Constitutive Equation to Predict Hot Deformation Behavior of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cai, Jun; Wang, Kuaishe; Zhai, Peng; Li, Fuguo; Yang, Jie

    2014-09-01

    A modified Johnson-Cook constitutive equation of Ti-6Al-4V alloy is proposed based on hot compression tests performed in the temperature range of 1073-1323 K and strain rate 0.001-1 s-1. The experimental stress-strain data were employed to develop the modified Johnson-Cook constitutive equation of different phase regimes (α + β and β phase). The predicted flow stresses using the developed equation were compared with experimental data. Correlation coefficient (R) and average absolute relative error (AARE) were introduced to verify the validity of the constitutive equation. The values of R and AARE for α + β phase were 0.990 and 7.81%, respectively. And in β phase region, the values of R and AARE were 0.985 and 10.36%, respectively. Meanwhile, the accuracy, the number of material constants involved, and the computational time required of the constitutive equation were evaluated by comparing with a strain-compensated Arrhenius-type constitutive equation. The results indicate that accuracy of modified Johnson-Cook constitutive equation is higher than that of compensated Arrhenius-type model at α + β phase, while lower at single β phase region. Meanwhile, the time required for evaluating the material constants of modified Johnson-Cook constitutive equation is much shorter than that of the strain-compensated Arrhenius type ones.

  19. Microstructural characterization of Ti-6Al-4V alloy subjected to the duplex SMAT/plasma nitriding.

    PubMed

    Pi, Y; Faure, J; Agoda-Tandjawa, G; Andreazza, C; Potiron, S; Levesque, A; Demangel, C; Retraint, D; Benhayoune, H

    2013-09-01

    In this study, microstructural characterization of Ti-6Al-4V alloy, subjected to the duplex surface mechanical attrition treatment (SMAT)/nitriding treatment, leading to improve its mechanical properties, was carried out through novel and original samples preparation methods. Instead of acid etching which is limited for morphological characterization by scanning electron microscopy (SEM), an original ion polishing method was developed. Moreover, for structural characterization by transmission electron microscopy (TEM), an ion milling method based with the use of two ions guns was also carried out for cross-section preparation. To demonstrate the efficiency of the two developed methods, morphological investigations were done by traditional SEM and field emission gun SEM. This was followed by structural investigations through selected area electron diffraction (SAED) coupled with TEM and X-ray diffraction techniques. The results demonstrated that ionic polishing allowed to reveal a variation of the microstructure according to the surface treatment that could not be observed by acid etching preparation. TEM associated to SAED and X-ray diffraction provided information regarding the nanostructure compositional changes induced by the duplex SMAT/nitriding process.

  20. Effects of Recrystallization on Microstructure and Texture Evolution of Cold-Rolled Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Jiang, Haitao; Dong, Peng; Zeng, Shangwu; Wu, Bo

    2016-05-01

    The effects of recrystallization during annealing process on microstructure and texture evolution of cold-rolled Ti-6Al-4V alloy plates were investigated. The plates after cold rolling with a thickness reduction of 5, 10, and 15% were annealed under different conditions of 750 °C for 1 h, 800 °C for 1 h, and 800 °C for 1.5 h, respectively. It was found out that the recrystallization temperature decreased with increasing rolling reduction due to higher storage energy, while the extension of annealing time caused grain growth. For the cold-rolled plate with a reduction of 10%, the resulting microstructure showed more equal-axis grains after annealing at 800 °C for 1 h, among different conditions. Moreover, the XRD results showed that the cold-rolled plate composed mainly of {0001} <10-10> basal texture, {10-11} <1-210> and {01-12} <10-10> pyramidal textures, and {01-10} <10-10> prismatic texture, and that the weak {10-11} <1-210> texture was transformed to components {01-12} <10-10> and {01-10} <10-10>, which were expected to improve formability. Electron back-scattered diffraction results ascertained that two mechanisms, i.e., recrystallization sites of preferred orientations and favorable grain growth both played important roles in static recrystallization.

  1. Effect of Variants of Thermomechanical Working and Annealing Treatment on Titanium Alloy Ti6Al4V Closed Die Forgings

    NASA Astrophysics Data System (ADS)

    Gupta, R. K.; Kumar, V. Anil; Kumar, P. Ram

    2016-06-01

    Performance of titanium alloy Ti6Al4V pressure vessels made of closed die forged domes of route `B' (multiple step forged and mill annealed) is reported to be better than route `A' (single/two step forged and mill annealed). Analysis revealed that forgings processed through route `B' have uniformity in microstructure and yield strength at various locations within the forging, as compared to that of route `A.' It is attributed to in-process recrystallization (dynamic as well as static) of route `B' forgings as compared to limited recrystallization of route `A' forgings. Further, post-forging recrystallization annealing (RA) effect is found to be more significant for route `A' forgings in achieving uniform microstructure and mechanical properties, since route `B' forgings have already undergone similar phenomenon during the thermomechanical working process itself. Considering prime importance of yield strength, statistical scatter in yield strength values within the forgings have been evaluated for forgings of both the routes. Standard deviation in the yield strength of route `B' forgings was lower (<10 MPa) as compared to route `A' (>15 MPa), which later became lower (~10 MPa) after RA with a minor decrease in yield strength. The present work discusses these variants of thermomechanical processing along with annealing to achieve better uniformity in properties and microstructure.

  2. Study on load relaxation based on hot bending and sizing of Ti6Al4V alloy sheet

    NASA Astrophysics Data System (ADS)

    Po, Liu; Yingying, Zong; Debin, Shan; Bin, Guo

    2013-05-01

    The mechanism of hot sizing following sheet thermal forming of titanium alloy is considered as stress relaxation based on creep flow. A certain amount of internal stress in sheet metal parts can be relaxed during hot-sizing stage and hence the springback can be markedly reduced. Hot v-bending of Ti6Al4V sheet were carried out to study the behavior of load relaxation and springback in specimens after hot sizing, also known as shape retention. Experimental results reveal that load relaxation occurs during hot sizing following sheet v-bending. Reduction of springback angle obtained using hot sizing is obviously larger than that obtained without hot sizing under the same thermal environment. During hot sizing, springback angle decreases with increase in temperature and time, respectively. Load relaxation behavior is affected by loading method, namely constant velocity and two step loading. The linear relation between creep rate and load relaxation rate was deduced in hot-sizing stage. The calculated ratio shows good agreement with experimental data obtained by two-step loading. V-bending and sizing together with appropriate loading method are demonstrated as a good approach for stress relaxation analysis.

  3. Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells

    NASA Astrophysics Data System (ADS)

    Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J.; Deb, Sanjukta

    2016-07-01

    Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation.

  4. Surface modification of Ti6Al4V alloy by PIII at high temperatures: Effects of plasma potential

    NASA Astrophysics Data System (ADS)

    Silva, M. M.; Ueda, M.; Pichon, L.; Reuther, H.; Lepienski, C. M.

    2007-04-01

    The present work is aimed to analyzing the influence of the plasma potential in the efficiency of plasma immersion ion implantation (PIII) process with nitrogen, at high temperatures (550 °C and 800 °C), applied to the Ti6Al4V alloy to increase its wear resistance. Treatments with plasma potentials (PP) at 420 V and 90 V were carried out. In the first case, in accordance with AES (Auger Electron Spectroscopy) analysis, nitrogen rich layers of 100 nm and 150 nm of thickness had been obtained, for total treatment times of 60 min and 120 min, respectively. For the treatments with lower PP of 90 V, the treated layers thicknesses have been measured by GDOS (Glow Discharge Optical Spectroscopy) and their values are 1 μm and 1.5 μm for treatments of 120 min and 240 min, respectively. The hardness values were determined for the samples treated with high PP by nanoindentation technique and a significant increase was observed for this treatment, reaching 11 GPa (60 min) and 19 GPa (120 min), which can be compared to 3.5-4.0 GPa obtained for the untreated samples. Pin-on-disk wear tests show that wear resistance increases after all these treatments. The friction coefficient as well as the wear rates are measured with a tribometer.

  5. Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells

    PubMed Central

    Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J.; Deb, Sanjukta

    2016-01-01

    Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation. PMID:27468811

  6. Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells.

    PubMed

    Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J; Deb, Sanjukta

    2016-01-01

    Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation. PMID:27468811

  7. Structure and tribological performance by nitrogen and oxygen plasma based ion implantation on Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Feng, Xingguo; Sun, Mingren; Ma, Xinxin; Tang, Guangze

    2011-09-01

    Ti6Al4V alloy was implanted with nitrogen-oxygen mixture by using plasma based ion implantation (PBII) at pulsed voltage -10, -30 and -50 kV. The implantation was up to 6 × 1017 ions/cm2 fluence. The changes in chemical composition, structure and hardness of the modified surfaces were studied by XPS and nanoindentation measurements. According to XPS, it was found that the modified layer was predominantly TiO2, but contained small amounts of TiO, Ti2O3, TiN and Al2O3 between the outmost layer and metallic substrate. Surface hardness and wear resistance of the samples increased significantly after PBII treatment, the wear rate of the sample implanted N2-O2 mixture at -50 kV decreased eight times than the untreated one. The sample implanted N2-O2 mixture showed better wear resistance than that of the sample only implanted oxygen at - 50 kV. The wear mechanism of untreated sample was abrasive-dominated and adhesive, and the wear scar of the sample implanted at -50 kV was characterized by abrasive wear-type ploughing.

  8. Behavior of surface and corner cracks subjected to tensile and bending loads in Ti-6Al-4V alloy

    NASA Technical Reports Server (NTRS)

    Forman, Royce G.; Mettu, Sambi R.

    1990-01-01

    The behavior of part-through flaws with regard to failure under monotonic loading and their growth under fatigue loading was studied experimentally and analytically. Comparisons are made of experimental values of toughness obtained using surface and corner cracked specimens with those obtained using standard test specimens, and also experimental growth cycles were compared with numerical predictions using the NASA/FLAGRO computer program. Tests were conducted on various types of surface and corner cracks under tensile and bending loads. Room temperature lab air provided the test environment. The material used in this study was the Ti-6Al-4V alloy in the solution treated and aged (STA) and stress relieved condition. Detailed tabulation of the fracture toughness data and results of life prediction using the NASA/FLAGRO program are presented. Fatigue crack growth rates for the part-through cracked specimens are compared with a base curve fitted from the data obtained using standard specimens. The fatigue loading used in the crack growth testing was constant-amplitude sinusoidal type.

  9. Effect of Wire-EDM cutting parameters on material removal rate of titanium alloy (Ti6Al4V)

    NASA Astrophysics Data System (ADS)

    Azam, N.; Afendi, M.

    2016-07-01

    In this study, titanium alloy (Ti6Al4V) which is also known as difficult to cut material is used as workpiece. Seven main parameters namely pulse duration (A), pulse interval (B), servo voltage (C), ignition pulse current (D), wire tension (E), wire speed (F) and dielectric pressure (G) have been experimentally studied by using Taguchi method as well as the determination of optimum parameters for material removal rate (MRR). Analysis of variance (ANOVA) has been used for recognizing the level of significant of WEDM cutting parameter for optimizing MRR and the result found that pulse duration and servo voltage give significant effect on MRR. While according to Signal to Noise (S/N) ratio response table for MRR, the parameters combination of A3B3C3D3E1F3G3 give the optimum value for MRR. It is also observed that the predicted results agree with the experimental values within an error of 4.6 %.

  10. Characterization of laser peening-induced effects on a biomedical Ti6Al4V alloy by thermoelectric means

    NASA Astrophysics Data System (ADS)

    Carreón, Hector; Barriuso, Sandra; Porro, Juan Antonio; González-Carrasco, Jose Luis; Ocaña, José Luis

    2014-12-01

    Laser peening has recently emerged as a useful technique to overcome detrimental effects associated with other well-known surface modification processes such as shot peening or grit blasting used in the biomedical field. It is worthwhile to notice that besides the primary residual stress effect, thermally induced effects might also cause subtle surface and subsurface microstructural changes that might influence corrosion resistance and fatigue strength of structural components. In this work, plates of Ti-6Al-4V alloy of 7 mm in thickness were modified by laser peening without using a sacrificial outer layer. Irradiation by a Q-switched Nd-YAG laser (9.4-ns pulse length) working at the fundamental 1064-nm wavelength at 2.8 J/pulse and with water as a confining medium was used. Laser pulses with a 1.5-mm diameter at an equivalent overlapping density of 5000 cm-2 were applied. Attempts to analyze the global-induced effects after laser peening were addressed by using the contacting and noncontacting thermoelectric power techniques.

  11. A Modified Johnson-Cook Constitutive Equation to Predict Hot Deformation Behavior of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cai, Jun; Wang, Kuaishe; Zhai, Peng; Li, Fuguo; Yang, Jie

    2015-01-01

    A modified Johnson-Cook constitutive equation of Ti-6Al-4V alloy is proposed based on hot compression tests performed in the temperature range of 1073-1323 K and strain rate 0.001-1 s-1. The experimental stress-strain data were employed to develop the modified Johnson-Cook constitutive equation of different phase regimes (α + β and β phase). The predicted flow stresses using the developed equation were compared with experimental data. Correlation coefficient ( R) and average absolute relative error (AARE) were introduced to verify the validity of the constitutive equation. The values of R and AARE for α + β phase were 0.990 and 7.81%, respectively. And in β phase region, the values of R and AARE were 0.985 and 10.36%, respectively. Meanwhile, the accuracy, the number of material constants involved, and the computational time required of the constitutive equation were evaluated by comparing with a strain-compensated Arrhenius-type constitutive equation. The results indicate that accuracy of modified Johnson-Cook constitutive equation is higher than that of compensated Arrhenius-type model at α + β phase, while lower at single β phase region. Meanwhile, the time required for evaluating the material constants of modified Johnson-Cook constitutive equation is much shorter than that of the strain-compensated Arrhenius type ones.

  12. Adhesion study of thermoplastic polyimides with Ti-6Al-4V alloy and PEEK-graphite composites

    SciTech Connect

    Yoon Taeho.

    1991-01-01

    High glass transition (e.g. 360C) melt processable thermoplastic polyimide homopolymers and poly(imide-siloxane) segmented copolymers were prepared from a number of diamines and dianhydrides via solution imidization, polydimethylsilxane segment incorporation and molecular weight control with non-reactive phthalimide end-groups. The adhesive bond performance of these polyimides was investigated as a function of molecular weight, siloxane incorporation, residual solvent, test temperature, and polyimide structure via single-lap shear samples prepared from treated Ti-6Al-4V alloy adherends and compression-molded film adhesives of scrim-cloth adhesives. The adhesive bond strengths increased greatly with siloxane-segment incorporation at 10, 20 and 30 wt% and decreased slightly with total polymer molecular weight. As the test temperature was increased, adhesive bond strength increased, decreased or showed a maximum at some temperatures depending on the polyimide structure and siloxane content. The poly(imide-30% siloxane) segmented copolymer and a miscible poly(ether-imide) also demonstrated excellent adhesive bond strength with poly(arylene ether ketone) PEEK{reg sign}-graphite composites.

  13. Void shrinking process and mechanisms of the diffusion bonded Ti-6Al-4V alloy with different surface roughness

    NASA Astrophysics Data System (ADS)

    Li, H.; Li, M. Q.; Kang, P. J.

    2016-01-01

    The diffusion bonding of Ti-6Al-4V alloy with different surface roughness was performed at 5 and 10 MPa. The influence of surface roughness on the void shrinking process and mechanisms was investigated. The average void size increases as the R a increases from 0.33 to 0.44 μm, while it decreases as the R a increases to 0.46 μm because of the decreasing of R λq. The void shrinking mechanisms were analyzed by using the dynamic model of void shrinking. Power-law creep is a dominant mechanism on void shrinking, of which the contribution decreases as the R a increases from 0.33 to 0.44 μm, while it increases as the R a increases to 0.46 μm. The influence of surface roughness on the contribution of plastic deformation and surface source mechanism on void shrinking is not significant while that on the contribution of interface source mechanism is dependent on the imposing pressure. The optimizing surface roughness is with a R a of 0.33 μm and R λq of 5.38 μm in this study.

  14. Study of aging effects in a Ti-6AL-4V alloy with Widmanstätten and equiaxed microstructures by non-destructive means

    SciTech Connect

    Carreon, Hector; Ruiz, Alberto; Santoveña, Bayron

    2014-02-18

    When the Ti-6Al-4V alloy is over-aged at 500-600°C, nanometer-sized α{sub 2} (Ti{sub 3}Al) phases can be homogeneously precipitated inside α phases, thereby leading to the additional improvement of mechanical properties. The present study was concerned with the effects of over-aging on thermoelectric power (TEP) measurements in a Ti-6Al-4V alloy. Widmanstätten and equiaxed microstructures containing fine and agr{sub 2} (Ti{sub 3}Al) particles were obtaining by over-aging a Ti-6Al-4V alloy. Over-aging heat treatments were conducted at 515°C, 545°C and 575°C for different aging times. In order to find out the factors affecting the variation in the TEP, the over-aging samples were examined by optical microscopy (OM) and (SEM) scanning electron microscopy. In particular, we studied the behavior of the physical material property hardness, an important parameter of the Ti-6Al-4V alloy mechanical properties, with respect to the variation in the aging time and temperature. It was found that the TEP measurements reveal an increase in the magnitude of the absolute TEP value of the over-aged Widmanstätten and equiaxed microstructures with regards to the unaged condition for different aging times, with a somewhat higher value at 515°C.

  15. Fatigue Performance of Powder Metallurgy (PM) Ti-6Al-4V Alloy: A Critical Analysis of Current Fatigue Data and Metallurgical Approaches for Improving Fatigue Strength

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.

    2016-03-01

    A comprehensive assessment of fatigue performance of powder metallurgy (PM) Ti-6Al-4V alloy, manufactured using various powder-based processing approaches to-date, is performed in this work. The focus is on PM processes that use either blended element (BE) or pre-alloyed (PA) powder as feedstock. Porosity and the microstructure condition have been found to be the two most dominant material variables that control the fatigue strength. The evaluation reveals that the fatigue performance of PM Ti-6Al-4V, in the as-sintered state, is far lower than that in the wrought condition. This is largely caused by residual porosity, even if it is present in small amounts, or, by the coarse lamellar colony microstructure. The fatigue strength is significantly improved by the closure of pores, and it approaches the levels of wrought Ti-6Al-4V alloys, after hot-isostatic-pressing (HIPing). Further thermo-mechanical and heat treatments lead to additional increases in fatigue strength-in one case, a high fatigue strength level, exceeding that of the mill-annealed condition, was achieved. The work identifies the powder, process and microstructure improvements that are necessary for achieving high fatigue strength in powder metallurgical Ti-6Al-4V alloys in order for them to effectively compete with wrought forms. The present findings, gathered from the traditional titanium powder metallurgy, are also directly applicable to additively manufactured titanium, because of the similarities in pores, defects, and microstructures between the two manufacturing processes.

  16. Commercially pure titanium (cp-Ti) versus titanium alloy (Ti6Al4V) materials as bone anchored implants - Is one truly better than the other?

    PubMed

    Shah, Furqan A; Trobos, Margarita; Thomsen, Peter; Palmquist, Anders

    2016-05-01

    Commercially pure titanium (cp-Ti) and titanium alloys (typically Ti6Al4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally, influenced material selection for different clinical applications: predominantly Ti6Al4V in orthopaedics while cp-Ti in dentistry. This paper attempts to address three important questions: (i) To what extent do the surface properties differ when cp-Ti and Ti6Al4V materials are manufactured with the same processing technique?, (ii) Does bone tissue respond differently to the two materials, and (iii) Do bacteria responsible for causing biomaterial-associated infections respond differently to the two materials? It is concluded that: (i) Machined cp-Ti and Ti6Al4V exhibit similar surface morphology, topography, phase composition and chemistry, (ii) Under experimental conditions, cp-Ti and Ti6Al4V demonstrate similar osseointegration and biomechanical anchorage, and (iii) Experiments in vitro fail to disclose differences between cp-Ti and Ti6Al4V to harbour Staphylococcus epidermidis growth. No clinical comparative studies exist which could determine if long-term, clinical differences exist between the two types of bulk materials. It is debatable whether cp-Ti or Ti6Al4V exhibit superiority over the other, and further comparative studies, particularly in a clinical setting, are required. PMID:26952502

  17. Commercially pure titanium (cp-Ti) versus titanium alloy (Ti6Al4V) materials as bone anchored implants - Is one truly better than the other?

    PubMed

    Shah, Furqan A; Trobos, Margarita; Thomsen, Peter; Palmquist, Anders

    2016-05-01

    Commercially pure titanium (cp-Ti) and titanium alloys (typically Ti6Al4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally, influenced material selection for different clinical applications: predominantly Ti6Al4V in orthopaedics while cp-Ti in dentistry. This paper attempts to address three important questions: (i) To what extent do the surface properties differ when cp-Ti and Ti6Al4V materials are manufactured with the same processing technique?, (ii) Does bone tissue respond differently to the two materials, and (iii) Do bacteria responsible for causing biomaterial-associated infections respond differently to the two materials? It is concluded that: (i) Machined cp-Ti and Ti6Al4V exhibit similar surface morphology, topography, phase composition and chemistry, (ii) Under experimental conditions, cp-Ti and Ti6Al4V demonstrate similar osseointegration and biomechanical anchorage, and (iii) Experiments in vitro fail to disclose differences between cp-Ti and Ti6Al4V to harbour Staphylococcus epidermidis growth. No clinical comparative studies exist which could determine if long-term, clinical differences exist between the two types of bulk materials. It is debatable whether cp-Ti or Ti6Al4V exhibit superiority over the other, and further comparative studies, particularly in a clinical setting, are required.

  18. Adhesion, activation, and aggregation of blood platelets and biofilm formation on the surfaces of titanium alloys Ti6Al4V and Ti6Al7Nb.

    PubMed

    Walkowiak-Przybyło, M; Klimek, L; Okrój, W; Jakubowski, W; Chwiłka, M; Czajka, A; Walkowiak, B

    2012-03-01

    Titanium alloys are still on the top list of fundamental materials intended for dental, orthopedics, neurological, and cardiovascular implantations. Recently, a special attention has been paid to vanadium-free titanium alloy, Ti6Al7Nb, that seems to represent higher biocompatibility than traditional Ti6Al4V alloy. Surprisingly, these data are not thoroughly elaborated in the literature; particularly there is a lack of comparative experiments conducted simultaneously and at the same conditions. Our study fills these shortcomings in the field of blood contact and microbiological colonization. To observe platelets adhesion and biofilm formation on the surfaces of compared titanium alloys, fluorescence microscope Olympus GX71 and scanning electron microscope HITACHI S-3000N were used. Additionally, flow cytometry analysis of platelets aggregation and activation in the whole blood after contact with sample surface, as an essential tool for biomaterial thrombocompatibility assessment, was proposed. As a result of our study it was demonstrated that polished surfaces of Ti6Al7Nb and Ti6Al4V alloys after contact with whole citrated blood and E. coli bacterial cells exhibit a considerable difference. Overall, it was established that Ti6Al4V has distinct tendency to higher thrombogenicity, more excessive bacterial biofilm formation and notable cytotoxic properties in comparison to Ti6Al7Nb. However, we suggest these studies should be extended for other types of cells and biological objects.

  19. Investigation of the Workability and Response of Ti-6Al-4V Titanium alloys at Lower Elevated Temperature and Higher Strain Rate

    SciTech Connect

    Huang, Cindy Xiaohui; Lim, Chao Voon; Castagne, Sylvie

    2011-05-04

    Titanium and its alloys have a wide range of applications in various industries such as aerospace, medical, automotive and even commercial products. However, formability of titanium alloys has always been an issue. This study presents the results of an investigation on the workability and response of Ti-6Al-4V deformed at different strain rates and lower elevated temperatures with different initial microstructures. Compression tests of cylindrical specimens were performed at various temperatures (300 deg. C, 400 deg. C, 450 deg. C, 500 deg. C) and at different strain rates (0.001 s{sup -1}, 0.02 s{sup -1} and 0.1 s{sup -1}). The effects of strain rate, temperature and initial microstructure on the workability of the Ti alloy were investigated. Based on these experimental results, workability maps for the respective initial microstructures were developed. Results showed that temperature played an important role in the formability of Ti-6Al-4V titanium alloys unlike strain rate. In addition, feasibility study on Multi-Directional Forging (MDF) was performed and positive results were obtained. It was demonstrated that Ti-6Al-4V titanium alloys can undergo severe plastic deformation at lower elevated temperature (400-500 deg. C) and at a higher strain rate of 0.1 s{sup -1}.

  20. Data Sheet Program and Mechanical Properties of Ti-5Al-2.5Sn ELI and Alloy 718 at Cryogenic Temperatures

    NASA Astrophysics Data System (ADS)

    Ogata, T.; Yuri, T.; Sumiyoshi, H.; Ono, Y.; Matsuoka, S.; Okita, K.

    2004-06-01

    In the development of Japan's self-developed H-IIA launch vehicle, it is important to sufficiently comprehend the properties of materials under conditions in which the materials are used in the system for its design and the improvement of its reliability. Through the process of failure analysis of the LE-7 engine of H-II No. 8 in 1999, detailed materials data and photographs of the fracture surface were required as reference data to determine in terms of fracture morphology and to analyze the fracture stress. A series of mechanical properties tests, such as tensile tests, impact tests, fracture toughness tests, and fatigue tests, on Ti-5Al-2.5Sn ELI and Alloy 718 at room temperature to 4K were mainly conducted by NIMS and NASDA. The obtained tensile and fracture toughness properties were a little bit smaller than those reported by NASA and NRIM, however, the fatigue properties were relatively lower than the data reported so far. Data resulting from the tests were reviewed in detail and published in the form of data sheets. This paper will introduce the data sheet program on space use materials and discuss an effect of microstructure of Ti-5Al-2.5Sn ELI and Alloy 718 on their mechanical properties at cryogenic temperatures.

  1. Development of Ti-6Al-4V and Ti-1Al-8V-5Fe Alloys Using Low-Cost TiH2 Powder Feedstock

    SciTech Connect

    Joshi, Vineet V.; Lavender, Curt; Moxon, Vladimir; Duz, Vlad; Nyberg, Eric; Weil, K. Scott

    2012-09-25

    Thermo-mechanical processing was performed on two titanium alloy billets, a beta-titanium alloy (Ti1Al8V5Fe) and an alpha-beta titanium alloy (Ti6Al4V), which had been produced using a novel low-cost powder metallurgy process that relies on the use of TiH2 powder as a feedstock material. The thermomechanical processing was performed in the beta region of the respective alloys to form 16-mm diameter bars. The hot working followed by the heat treatment processes not only eliminated the porosity within the materials but also developed the preferred microstructures. Tensile testing and rotating beam fatigue tests were conducted on the as-rolled and heat-treated materials to evaluate their mechanical properties. The mechanical properties of these alloys matched well with those produced by the conventional ingot processing route.

  2. Constitutive Equations and ANN Approach to Predict the Flow Stress of Ti-6Al-4V Alloy Based on ABI Tests

    NASA Astrophysics Data System (ADS)

    Wang, Fuzeng; Zhao, Jun; Zhu, Ningbo

    2016-09-01

    The flow behavior of Ti-6Al-4V alloy was studied by automated ball indentation (ABI) tests in a wide range of temperatures (293, 493, 693, and 873 K) and strain rates (10-6, 10-5, and 10-4 s-1). Based on the experimental true stress-plastic strain data derived from the ABI tests, the Johnson-Cook (JC), Khan-Huang-Liang (KHL) and modified Zerilli-Armstrong (ZA) constitutive models, as well as artificial neural network (ANN) methods, were employed to predict the flow behavior of Ti-6Al-4V. A comparative study was made on the reliability of the four models, and their predictability was evaluated in terms of correlation coefficient (R) and mean absolute percentage error. It is found that the flow stresses of Ti-6Al-4V alloy are more sensitive to temperature than strain rate under current experimental conditions. The predicted flow stresses obtained from JC model and KHL model show much better agreement with the experimental results than modified ZA model. Moreover, the ANN model is much more efficient and shows a higher accuracy in predicting the flow behavior of Ti-6Al-4V alloy than the constitutive equations.

  3. Constitutive modeling for Ti-6Al-4V alloy machining based on the SHPB tests and simulation

    NASA Astrophysics Data System (ADS)

    Chen, Guang; Ke, Zhihong; Ren, Chengzu; Li, Jun

    2016-06-01

    A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 104-106 s-1. Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar (SHPB) technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10-4-104s-1. The Johnson Cook (JC) model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate(approximately 3×104 s-1) conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests (10-4-104 s-1) and simulation (up to 3×104 s-1). The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation.

  4. The Nature of Tensile Ductility as Controlled by Extreme-Sized Pores in Powder Metallurgy Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Ravi Chandran, K. S.; Cao, F.; Koopman, M.; Fang, Z. Zak

    2016-05-01

    Tensile properties of Ti-6Al-4V titanium alloy, sintered by a new process (sintering, phase transformation, and dehydrogenation of titanium hydride compacts, termed HSPT process), were investigated to determine how the sintering pores influence the tensile strength and ductility. It was found that the ductility in the sintered alloy is severely affected by the size of the largest pore, referred here as extreme-sized pore, even when the average volume fraction of porosity is nearly constant between a large number of samples. It is shown that the rapid decrease in ductility, with an increase in the extreme pore size, is caused by strain localization around the extreme-sized pore and early crack initiation. This crack initiation leads to fracture of the plane containing the pore thereby limiting the extent of uniform plastic strain that can be attained before fracture. Interestingly, the strength properties are, however, found to be independent of the size of the extreme-sized pore. The results are explained on the basis of stress concentration and strain localization around the extreme-sized pores. The work also reveals that if the extreme-sized pores are eliminated, PM Ti-6Al-4V alloy with high strength (~1100 MPa) and good ductility (~12 pct), which is easily comparable to a wrought Ti-6Al-4V alloy, can be achieved even at oxygen levels up to 0.4 wt pct.

  5. Effects of Dextrose and Lipopolysaccharide on the Corrosion Behavior of a Ti-6Al-4V Alloy with a Smooth Surface or Treated with Double-Acid-Etching

    PubMed Central

    Faverani, Leonardo P.; Assunção, Wirley G.; de Carvalho, Paulo Sérgio P.; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T.; Barao, Valentim A.

    2014-01-01

    Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (α = 0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2 = 0.726, p<0.0001 for the smooth surface; R2 = 0.405, p = 0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no

  6. Effects of dextrose and lipopolysaccharide on the corrosion behavior of a Ti-6Al-4V alloy with a smooth surface or treated with double-acid-etching.

    PubMed

    Faverani, Leonardo P; Assunção, Wirley G; de Carvalho, Paulo Sérgio P; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T; Barao, Valentim A

    2014-01-01

    Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (α = 0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2 = 0.726, p<0.0001 for the smooth surface; R2 = 0.405, p = 0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no

  7. Electrodeposition of HAp coatings on Ti6Al4V alloy and its electrochemical behavior in simulated body fluid solution

    NASA Astrophysics Data System (ADS)

    Thanh Dinh, Thi Mai; Thom Nguyen, Thi; Pham, Thi Nam; Phuong Nguyen, Thu; Thu Trang Nguyen, Thi; Hoang, Thai; Grossin, David; Bertrand, Ghislaine; Drouet, Christophe

    2016-06-01

    Hydroxyapatite (HAp) coatings were prepared on Ti6Al4V substrate by electrodeposition method from electrolyte solution containing Ca(NO3)2, NH4H2PO4 and NaNO3. The results show that the HAp coatings were single phase crystals of HAp. Scanning electron microscope (SEM) images present that HAp/Ti6Al4V have flake shapes which arrange to form like-coral agglomerates. In vitro test of the Ti6Al4V and HAp/Ti6Al4V in simulated body fluid (SBF) solution was investigated with different immersion times. pH of SBF solution decreased and the mass of materials increased. SEM images prove the formation of apatite on the surface of Ti6Al4V and HAp/Ti6Al4V. The corrosion current density during immersion time of substrate is always higher than the one of HAp/Ti6Al4V because the deposited HAp can protect well for the substrate.

  8. Cavitation Erosion Behavior of HPDL-Treated TWAS-Coated Ti6Al4V Alloy and Its Similarity with Water Droplet Erosion

    NASA Astrophysics Data System (ADS)

    Mann, B. S.; Arya, Vivek; Pant, B. K.

    2012-06-01

    Twin wire arc-sprayed (TWAS) coating of commercially available SHS 7170-cored wire was obtained on Ti6AL4V alloy, and to improve its properties, it was further surface treated with high-power diode laser (HPDL). The cavitation erosion (CE) resistance of TWAS-coated samples was evaluated as per ASTM G-32-2003 and it was compared with laser-treated and untreated Ti6Al4V alloys. The CE resistance of TWAS-coated SHS 7170 samples after HPDL treatment has improved significantly. The main reasons for its improvement are elimination of pores, increased fracture toughness, reduced hardness, and brittleness. The CE resistance of HPDL-treated TWAS coating is compared with water droplet erosion resistance. It is observed that there is a similarity in the both the phenomenon.

  9. Stress-corrosion crack-growth study of titanium alloy Ti-6Al-4V exposed to freon PCA and nitrogen tetroxide MON-1

    NASA Technical Reports Server (NTRS)

    Bjorklund, R. A.

    1983-01-01

    An experimental fracture mechanics program was performed to determine the stress corrosion crack growth sensitivity of the propellant tank material, titanium alloy Ti-6Al-4V, for aerospace satellite applications involving long term exposure to Freon PCA and nitrogen tetroxide MON-1. Sustained load tests were made at a 49 C (120 F) constant temperature using thin gauge tensile test specimens containing semielliptical surface flaws. Test specimen types included parent metal, center of weld, and weld heat affected zone. It was concluded that Ti-6Al-4V alloy is not adversely affected in a stress environment when exposed to Freon PCA for 1000 hours followed by exposure to nitrogen tetroxide MON-1 for 2000 hours at stress levels up to 80% of the experimental critical plane strain stress intensity factor.

  10. A SEM and EDS based Study of the Microstructural Modifications of Turning Inserts in the Dry Machining of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Gerez, J. M.; Sanchez-Carrilero, M.; Salguero, J.; Batista, M.; Marcos, M.

    2009-11-01

    Titanium and its alloys are considered as low machinability materials because of its low thermal conductivity, which provokes a high temperature in the tool-chip interface. However, thanks to its excellent relationship weight/mechanical properties, this material is widely used in the aerospace industrial sector. This paper reports on the results of an analysis of the surface changes of hard metal (WC-Co) turning inserts employed in the dry turning of alloy UNS 56400 (Ti-6Al-4V), widely used in aerospace industry. The analysis has been developed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques.

  11. Thermal Modeling and Simulation of Electron Beam Melting for Rapid Prototyping on Ti6Al4V Alloys

    NASA Astrophysics Data System (ADS)

    Neira Arce, Alderson

    To be a viable solution for contemporary engineering challenges, the use of titanium alloys in a wider range of applications requires the development of new techniques and processes that are able to decrease production cost and delivery times. As a result, the use of material consolidation in a near-net-shape fashion, using dynamic techniques like additive manufacturing by electron beam selective melting EBSM represents a promising method for part manufacturing. However, a new product material development can be cost prohibitive, requiring the use of computer modeling and simulation as a way to decrease turnaround time. To ensure a proper representation of the EBSM process, a thermophysical material characterization and comparison was first performed on two Ti6Al4V powder feedstock materials prepared by plasma (PREP) and gas atomized (GA) processes. This evaluation comprises an evaluation on particle size distribution, density and powder surface area, collectively with the temperature dependence on properties such as heat capacity, thermal diffusivity, thermal conductivity and surface emissivity. Multiple techniques were employed in this evaluation, including high temperature differential scanning calorimetry (HT-DSC), laser flash analysis (LFA), infrared remote temperature analysis (IR-Thermography), laser diffraction, liquid and gas pycnometry using mercury and krypton adsorption respectively. This study was followed by the review of complementary strategies to simulate the temperature evolution during the EBSM process, using a finite element analysis package called COMSOL Multiphysics. Two alternatives dedicated to representing a moving heat source (electron beam) and the powder bed were developed using a step-by-step approximation initiative. The first method consisted of the depiction of a powder bed discretized on an array of domains, each one representing a static melt pool, where the moving heat source was illustrated by a series of time dependant selective

  12. Electrochemical characterization of MC3T3-E1 cells cultured on γTiAl and Ti-6Al-4V alloys.

    PubMed

    Bueno-Vera, J A; Torres-Zapata, I; Sundaram, P A; Diffoot-Carlo, N; Vega-Olivencia, C A

    2015-12-01

    Electrochemical impedance spectroscopy (EIS) was used to study the behavior of MC3T3-E1 cells cultured in an αMEM+FBS solution on two Ti-based alloys (Ti-6Al-4V and γTiAl) for 4, 7 and 14 days. EIS measurements were carried out at an open-circuit potential in a 1 mHz to 100 kHz frequency range. Results indicate a general increase in impedance on the Ti alloy surfaces with cells as a function of time. Bode plots indicate changes corresponding to the passive oxide film, adsorption of proteins and cell tissue on surfaces with the passage of time. Normal cellular activity based on the polygonal morphology, with long and fine cytoplasmic prolongations of the cells on Ti-6Al-4V and γTiAl was observed from SEM images. Similarly, mineralization nodules corresponding to cell differentiation associated with the osseogenetic process were observed confirmed by Alizarin Red S staining. Immunofluorescence analysis to detect the presence of collagen Type I showed an increase in the segregation of collagen as a function of time. The impedance values obtained from EIS testing are indicative of the corrosion protection offered to the Ti alloy substrates by the cell layer. This study shows that γTiAl has better corrosion resistance than that of Ti-6Al-4V in the αMEM+FBS environment in the presence of MC3T3-E1 cells.

  13. Influence of the fabrication process and fluoride content on the tribocorrosion behaviour of Ti6Al4V biomedical alloy in artificial saliva.

    PubMed

    Licausi, M P; Igual Muñoz, A; Amigó Borrás, V

    2013-04-01

    Titanium and its alloys are widely used as dental implants due to their low density, excellent biocompatibility, mechanical properties and corrosion resistance. However, during their lifetime Ti6Al4V biomedical alloys are subjected to different mechanical actions (i.e., sliding or fretting), thus resulting in a tribocorrosion system, which is an irreversible material degradation process due to the combined effect of corrosion and wear. In this study, the tribo-electrochemical behavior of cast and sintered (by powder metallurgy) Ti6Al4V alloy in artificial human saliva solution without and with fluoride additions of 100ppm and 1000ppm and in an average industrial mouth wash solution with a 112ppm fluoride content have been investigated by different electrochemical techniques. The same tribocorrosion mechanisms were found in the cast and sintered titanium alloys, although slightly different wear debris behavior was observed. At low applied passive potentials, wear rates are similar to those obtained under equilibrium conditions (Open Circuit Potential). There exists a critical fluoride concentration above which corrosion and tribocorrosion rates increase.

  14. Surface analysis and biocorrosion properties of nanostructured surface sol-gel coatings on Ti6Al4V titanium alloy implants.

    PubMed

    Advincula, Maria C; Petersen, Don; Rahemtulla, Firoz; Advincula, Rigoberto; Lemons, Jack E

    2007-01-01

    Surfaces of biocompatible alloys used as implants play a significant role in their osseointegration. Surface sol-gel processing (SSP), a variant of the bulk sol-gel technique, is a relatively new process to prepare bioreactive nanostructured titanium oxide for thin film coatings. The surface topography, roughness, and composition of sol-gel processed Ti6Al4V titanium alloy coatings was investigated by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS). This was correlated with corrosion properties, adhesive strength, and bioreactivity in simulated body fluids (SBF). Electroimpedance spectroscopy (EIS) and polarization studies indicated similar advantageous corrosion properties between sol-gel coated and uncoated Ti6Al4V, which was attributed to the stable TiO2 composition, topography, and adhesive strength of the sol-gel coating. In addition, inductive coupled plasma (ICP) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) analysis of substrates immersed in SBF revealed higher deposition of calcium and phosphate and low release rates of alloying elements from the sol-gel modified alloys. The equivalent corrosion behavior and the definite increase in nucleation of calcium apatite indicate the potential of the sol-gel coating for enhanced bioimplant applications.

  15. Novel artificial hip joint: A layer of alumina on Ti-6Al-4V alloy formed by micro-arc oxidation.

    PubMed

    Khanna, Rohit; Kokubo, Tadashi; Matsushita, Tomiharu; Nomura, Yuuji; Nose, Norihiro; Oomori, Yoshiyuki; Yoshida, Takuya; Wakita, Koichi; Takadama, Hiroaki

    2015-10-01

    In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640 °C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of γ-alumina and inner-most dense layer of α-alumina. The α-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint. PMID:26117770

  16. Heat transfer and fluid flow during electron beam welding of 21Cr-6Ni-9Mn steel and Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Rai, R.; Burgardt, P.; Milewski, J. O.; Lienert, T. J.; Roy, T. Deb

    2009-01-01

    Electron beam welding (EBW) of two important engineering alloys, Ti-6Al-4V and 21Cr-6Ni-9Mn, was studied experimentally and theoretically. The temperatures at several monitoring locations in the specimens were measured as a function of time during welding and the cross-sections of the welds were examined by optical microscopy. The theoretical research involved numerical simulation of heat transfer and fluid flow during EBW. The model output included temperature and velocity fields, fusion zone geometry and temperature versus time results. The numerically computed fusion zone geometry and the temperature versus time plots were compared with the corresponding experimentally determined values for each weld. Both the experimental and the modelling results were compared with the corresponding results for the keyhole mode laser beam welding (LBW). Both experimental and modelling results demonstrate that the fusion zone size in Ti-6Al-4V alloy was larger than that of the 21Cr-6Ni-9Mn stainless steel during both the electron beam and laser welding. Higher boiling point and lower solid state thermal conductivity of Ti-6Al-4V contributed to higher peak temperatures in Ti-6Al-4V welds compared with 21Cr-6Ni-9Mn stainless steel welds. In the EBW of both the alloys, there were significant velocities of liquid metal along the keyhole wall driven by the Marangoni convection. In contrast, during LBW, the velocities along the keyhole wall were negligible. Convective heat transfer was important in the transport of heat in the weld pool during both the laser and the EBW. The computed keyhole wall temperatures during EBW at low pressures were lower than those during the LBW at atmospheric pressure for identical heat input.

  17. Increasing Ti-6Al-4V brazed joint strength equal to the base metal by Ti and Zr amorphous filler alloys

    SciTech Connect

    Ganjeh, E.; Sarkhosh, H.; Bajgholi, M.E.; Khorsand, H.; Ghaffari, M.

    2012-09-15

    Microstructural features developed along with mechanical properties in furnace brazing of Ti-6Al-4V alloy using STEMET 1228 (Ti-26.8Zr-13Ni-13.9Cu, wt.%) and STEMET 1406 (Zr-9.7Ti-12.4Ni-11.2Cu, wt.%) amorphous filler alloys. Brazing temperatures employed were 900-950 Degree-Sign C for the titanium-based filler and 900-990 Degree-Sign C for the zirconium-based filler alloys, respectively. The brazing time durations were 600, 1200 and 1800 s. The brazed joints were evaluated by ultrasonic test, and their microstructures and phase constitutions analyzed by metallography, scanning electron microscopy and X-ray diffraction analysis. Since microstructural evolution across the furnace brazed joints primarily depends on their alloying elements such as Cu, Ni and Zr along the joint. Accordingly, existence of Zr{sub 2}Cu, Ti{sub 2}Cu and (Ti,Zr){sub 2}Ni intermetallic compounds was identified in the brazed joints. The chemical composition of segregation region in the center of brazed joints was identical to virgin filler alloy content which greatly deteriorated the shear strength of the joints. Adequate brazing time (1800 s) and/or temperature (950 Degree-Sign C for Ti-based and 990 Degree-Sign C for Zr-based) resulted in an acicular Widmanstaetten microstructure throughout the entire joint section due to eutectoid reaction. This microstructure increased the shear strength of the brazed joints up to the Ti-6Al-4V tensile strength level. Consequently, Ti-6Al-4V can be furnace brazed by Ti and Zr base foils produced excellent joint strengths. - Highlights: Black-Right-Pointing-Pointer Temperature or time was the main factors of controlling braze joint strength. Black-Right-Pointing-Pointer Developing a Widmanstaetten microstructure generates equal strength to base metal. Black-Right-Pointing-Pointer Brittle intermetallic compounds like (Ti,Zr){sub 2}Ni/Cu deteriorate shear strength. Black-Right-Pointing-Pointer Ti and Zr base filler alloys were the best choice for brazing Ti

  18. In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

    PubMed

    Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

    2014-01-01

    Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants.

  19. Effect of argon purity on mechanical properties, microstructure and fracture mode of commercially pure (cp) Ti and Ti-6Al-4V alloys for ceramometal dental prostheses.

    PubMed

    Bauer, José; Cella, Suelen; Pinto, Marcelo M; Filho, Leonardo E Rodrigues; Reis, Alessandra; Loguercio, Alessandro D

    2009-12-01

    Provision of an inert gas atmosphere with high-purity argon gas is recommended for preventing titanium castings from contamination although the effects of the level of argon purity on the mechanical properties and the clinical performance of Ti castings have not yet been investigated. The purpose of this study was to evaluate the effect of argon purity on the mechanical properties and microstructure of commercially pure (cp) Ti and Ti-6Al-4V alloys. The castings were made using either high-purity and/or industrial argon gas. The ultimate tensile strength (UTS), proportional limit (PL), elongation (EL) and microhardness (VHN) at different depths were evaluated. The microstructure of the alloys was also revealed and the fracture mode was analyzed by scanning electron microscopy. The data from the mechanical tests and hardness were subjected to a two-and three-way ANOVA and Tukey's test (alpha = 0.05). The mean values of mechanical properties were not affected by the argon gas purity. Higher UTS, PL and VHN, and lower EL were observed for Ti-6Al-4V. The microhardness was not influenced by the argon gas purity. The industrial argon gas can be used to cast cp Ti and Ti-6Al-4V.

  20. Enhanced wear and fatigue properties of Ti-6Al-4V alloy modified by plasma carburizing/CrN coating.

    PubMed

    Park, Y G; Wey, M Y; Hong, S I

    2007-05-01

    In this study, a newly developed duplex coating method incorporating plasma carburization and CrN coating was applied to Ti-6Al-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150 microm in depth and CrN coating film with 7.5 microm in thickness were formed after duplex coating. Hard carbide particles such as TiC And V(4)C(3) were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to about 1,960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex-coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex-coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.

  1. A comparison of corrosion, tribocorrosion and electrochemical impedance properties of pure Ti and Ti6Al4V alloy treated by micro-arc oxidation process

    NASA Astrophysics Data System (ADS)

    Fazel, M.; Salimijazi, H. R.; Golozar, M. A.; Garsivaz jazi, M. R.

    2015-01-01

    In this paper, the micro-arc oxidation (MAO) coatings were performed on pure Ti and Ti6Al4V samples at 180 V. The results indicated that unlike the volcanic morphology of oxide layer on pure Ti, a cortex-like morphology with irregular vermiform slots was seen on MAO/Ti6Al4V sample. According to polarization curves, the corrosion resistance of untreated samples was significantly increased by MAO process. The electrochemical impedance spectroscopy analysis showed a lower capacitance of barrier layer (led to higher resistance) for MAO/Ti specimens. This indicates that corrosive ions diffusion throughout the oxide film would be more difficult resulted in a higher corrosion resistance. Tribocorrosion results illustrated that the potential of untreated samples was dropped sharply to very low negative values. However, the lower wear volume loss was achieved for Ti6Al4V alloy. SEM images of worn surfaces demonstrated the local detachment of oxide layer within the wear track of MAO/Ti sample. Conversely, no delamination was detected in MAO/Ti6Al4V and a mild abrasive wear was the dominant mechanism.

  2. A comparison in mechanical properties of cermets of calcium silicate with Ti-55Ni and Ti-6Al-4V alloys for hard tissues replacement.

    PubMed

    Ataollahi Oshkour, Azim; Pramanik, Sumit; Shirazi, Seyed Farid Seyed; Mehrali, Mehdi; Yau, Yat-Huang; Abu Osman, Noor Azuan

    2014-01-01

    This study investigated the impact of calcium silicate (CS) content on composition, compressive mechanical properties, and hardness of CS cermets with Ti-55Ni and Ti-6Al-4V alloys sintered at 1200°C. The powder metallurgy route was exploited to prepare the cermets. New phases of materials of Ni16Ti6Si7, CaTiO3, and Ni31Si12 appeared in cermet of Ti-55Ni with CS and in cermet of Ti-6Al-4V with CS, the new phases Ti5Si3, Ti2O, and CaTiO3, which were emerged during sintering at different CS content (wt%). The minimum shrinkage and density were observed in both groups of cermets for the 50 and 100 wt% CS content, respectively. The cermets with 40 wt% of CS had minimum compressive Young's modulus. The minimum of compressive strength and strain percentage at maximum load were revealed in cermets with 50 and 40 wt% of CS with Ti-55Ni and Ti-6Al-4V cermets, respectively. The cermets with 80 and 90 wt% of CS showed more plasticity than the pure CS. It concluded that the composition and mechanical properties of sintered cermets of Ti-55Ni and Ti-6Al-4V with CS significantly depend on the CS content in raw cermet materials. Thus, the different mechanical properties of the cermets can be used as potential materials for different hard tissues replacements. PMID:25538954

  3. A new theoretical model for high power laser clad TiC/NiCrBSiC composite coatings on Ti6Al4V alloys

    NASA Astrophysics Data System (ADS)

    Lei, Yiwen; Sun, Ronglu; Lei, Jianbo; Tang, Ying; Niu, Wei

    2010-09-01

    A new three-dimensional model was proposed to simulate the high power laser clad TiC/NiCrBSiC composite coatings on Ti6Al4V alloys using commercial finite element analysis software. Powders of TiC, NiCrBSiC alloy and cuboid of Ti6Al4V alloys were taken as sample materials. The dilution rate, the melt pool, and the heat affected zone (HAZ) of the substrate under different incident laser power were obtained from the calculation and compared with the microstructure of the coatings. The simulated results show that a good quality laser clad TiC/NiCrBSiC composite coating with low dilution rate and excellent metallurgical bond can be prepared under the processing parameters as follows: scanning velocity 5 mm/s, laser beam diameter 4.5 mm and incident laser power 2500 W. There exhibits an excellent agreement between the simulated results and experimental data. It indicates that the new model is helpful to optimize the processing parameters to form a good quality coating.

  4. Fatigue properties of cast and heat treated Ti-6Al-4V alloy for anatomic hip prostheses.

    PubMed

    Ducheyne, P; Kohn, D; Smith, T S

    1987-05-01

    The intricate shape of Ti-6Al-4V anatomic hip prostheses necessitates the use of casting as a fabrication method, since neither machining, nor forging or powder metallurgial processing are reasonably acceptable. Cast and hot isostatically pressed Ti-6Al-4V, however, has a relatively low ductility and reduced fatigue properties. Appropriate thermal treatments can improve these properties. Specifically, treatments comprising a beta-solutionizing and an aging step yield ductilities similar to the forged and annealed condition, and fatigue properties 11.5% above the non-treated condition. Such treatments produce small alpha-beta platelet colonies with a ragged, tortuous morphology. The reduction of scatter in fatigue strength is the result of the formation of this well controlled microstructure.

  5. Microstructures and Properties of Plasma Electrolytic Oxidized Ti Alloy (Ti-6Al-4V) for Bio-implant Application

    NASA Astrophysics Data System (ADS)

    Kumari, Renu; Blawert, Carsten; Majumdar, J. Dutta

    2016-02-01

    In the present study, plasma electrolytic oxidation (PEO) of Ti6Al4V has been performed in an electrolyte containing 20 g/L of Na2SiO3, 10 g/L of Na3PO4, 2 g/L of KOH, and 5 g/L of hydroxyapatite at an optimum constant potential of 430 V for 10 minutes. Followed by PEO treatment, surface roughness was measured using non-contact optical profilometer. A detailed characterization of microstructure, composition and phase analysis was carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopic analysis, Fourier-transform infrared, and X-ray diffraction study. The mechanical properties of the surface have been evaluated by measuring nano-hardness and wear resistance. The effect of surface modification on corrosion resistance property has also been evaluated in Hank's solution. Finally, wettability and bioactivity test have been also performed. PEO developed a thick (150 μm) porous (35 pct) oxide film on the surface of Ti-6Al-4V consisting of anatase, rutile, and SiO2. The nano-hardness of the PEO-treated surface is increased to 8 ± 0.5 GPa as compared to 2 ± 0.4 GPa of the as-received Ti-6Al-4V. Wear and corrosion resistance were improved following oxidation. There is an improvement in wettability in terms of decrease in contact angle from 60 ± 1.5 to 45 ± 1 deg. Total surface energy and its polar component were also increased significantly on PEO-treated surface as compared to the as-received Ti6Al4V.

  6. Oxygen depth profiling by resonant backscattering and glow discharge optical emission spectroscopy of Ti-6Al-4V alloy oxidized by ion implantation and plasma based treatment

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, S.; Topic, M.; Pichon, L.; Comrie, C. M.; Mtshali, C.

    2016-10-01

    Oxygen depth profiling by means of 16O(α,α)16O backscattering and glow discharge optical emission spectroscopy (GDOES) was investigated in two different sets of Ti-6Al-4V samples. The first set was made of Ti-6Al-4V samples implanted at room temperature and 550 °C with 50 and 150 keV O+ ions at fluences ranging from 1.5 × 1017 to 6.0 × 1017 ions/cm2. The second set consisted of Ti-6Al-4V samples treated at 550 °C for 7 h and 24 h under low pressure (8 Pa) oxygen, eventually with RF plasma activation. These results are part of a wider investigation on Ti-6Al-4V motivated by recent publications which have shown that an oxide layer can enhance hydrogen absorption and can then promote Ti-6Al-4V alloys as efficient hydrogen storage materials. The results obtained by the two characterization techniques were compared and discussed, enabling to adjust the dependence to the oxygen concentration of the sputtering rates to be used in the time-to-depth transformation required in GDOES analysis. Considering the low thickness of oxidized alloy, usual procedures employed in GDOES depth calculation were indeed not adapted. Once calibrated thanks to the resonant RBS, GDOES can then be easily employed as fast characterization of oxidized and/or hydrogenated surface of Ti-6Al-4V. The obtained results show that the oxygen content into the surface oxidized layer slightly increases in samples implanted at higher fluence and higher temperature. However the overall oxidized layer thickness (<200 nm) remains within the projected ion depth range and is not significantly increased by thermal diffusion at 550 °C. Taken into account the initial oxide layer, the incorporated oxygen quantity mainly corresponds to the implanted fluence but it can be slightly higher with 550 °C implantation, indicating a slight additional oxidation by residual oxygen or surface contamination. The oxygen penetrations and contents in samples oxidized by thermally activated diffusion treatments were more

  7. Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications

    SciTech Connect

    Wierzchon, T.; Ossowski, M.; Borowski, T.; Morgiel, J.; Czarnowska, E.

    2011-01-17

    In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low-temperature glow discharge assisted oxynitriding.The paper describes the surface layer of TiO{sub 2}+TiN+Ti{sub 2}N+{alpha}Ti(N) type produced at temperature 680 deg. C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi-phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed.Properties of produced surface layers are discussed with reference to titanium alloy. The obtained data show that produced surface layers improves titanium alloy properties both frictional wear and biological. Preliminary in vitro examinations show good biocompatibility and antithrombogenic properties.

  8. High-Cycle Fatigue Properties and Fatigue Crack Initiation Behavior of Ti-5%Al-2.5%Sn Eli Alloy at Cryogenic Temperatures

    NASA Astrophysics Data System (ADS)

    Ono, Y.; Demura, M.; Yuri, T.; Ogata, T.; Matsuoka, S.; Hori, S.

    2008-03-01

    Tensile tests and uni-axial loading fatigue tests were performed at 4 K, 77 K and 293 K for Ti-5%Al-2.5%Sn extra low interstitial (ELI) forged alloy. The 0.2% proof stress and the tensile strength of this alloy increased with a decrease of temperature. However, high-cycle fatigue strength at cryogenic temperatures was relatively low compared to that at 293 K. In the specimens fatigue-tested at cryogenic temperatures, facets formed at the crack initiation site. On the other hand, there was not a distinct facet at the crack initiation site in the specimens tested at 293 K. The crystallographic orientation of the facet was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to clarify the fatigue crack initiation mechanism at cryogenic temperatures. The SEM-EBSD analyses revealed that the facet plane was {112¯1} twin plane and the {112¯1} twins developed during high-cycle fatigue tests at cryogenic temperatures, leading to the fatigue crack initiation at {112¯1} twin/matrix interface. Based on these results, the fatigue crack initiation related with twin deformation is supposed to degrade high-cycle fatigue strength at cryogenic temperatures.

  9. Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application.

    PubMed

    Ganapathy, Perumal; Manivasagam, Geetha; Rajamanickam, Asokamani; Natarajan, Alagumurthi

    2015-01-01

    This paper presents the wear characteristics of the composite ceramic coating made with Al2O3-40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma parameters was performed using response surface methodology to obtain dense coating. The tribological behaviors of the coated and uncoated substrates were evaluated using a ball-on-plate sliding wear tester at 37°C in simulated body-fluid conditions. The microstructure of both the titanium alloy and coated specimen were examined using an optical microscope and scanning electron microscope. The hardness of the plasma-sprayed alumina-zirconia composite coatings was 2.5 times higher than that of the Ti-6Al-4V alloy, while the wear rate of Ti-6Al-4V alloy was 253 times higher than that of the composite-coated Ti-6Al-4V alloy. The superior wear resistance of the alumina-zirconia coated alloy is attributed to its enhanced hardness and intersplat bonding strength. Wear-track examination showed that the predominant wear mechanism of Ti-6Al-4V alloy was abrasive and adhesive wear, whereas, in the case of alumina-zirconia composite coated alloy, the wear was dominated by microchipping and microcracking.

  10. Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application.

    PubMed

    Ganapathy, Perumal; Manivasagam, Geetha; Rajamanickam, Asokamani; Natarajan, Alagumurthi

    2015-01-01

    This paper presents the wear characteristics of the composite ceramic coating made with Al2O3-40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma parameters was performed using response surface methodology to obtain dense coating. The tribological behaviors of the coated and uncoated substrates were evaluated using a ball-on-plate sliding wear tester at 37°C in simulated body-fluid conditions. The microstructure of both the titanium alloy and coated specimen were examined using an optical microscope and scanning electron microscope. The hardness of the plasma-sprayed alumina-zirconia composite coatings was 2.5 times higher than that of the Ti-6Al-4V alloy, while the wear rate of Ti-6Al-4V alloy was 253 times higher than that of the composite-coated Ti-6Al-4V alloy. The superior wear resistance of the alumina-zirconia coated alloy is attributed to its enhanced hardness and intersplat bonding strength. Wear-track examination showed that the predominant wear mechanism of Ti-6Al-4V alloy was abrasive and adhesive wear, whereas, in the case of alumina-zirconia composite coated alloy, the wear was dominated by microchipping and microcracking. PMID:26491323

  11. Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application

    PubMed Central

    Ganapathy, Perumal; Manivasagam, Geetha; Rajamanickam, Asokamani; Natarajan, Alagumurthi

    2015-01-01

    This paper presents the wear characteristics of the composite ceramic coating made with Al2O3-40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma parameters was performed using response surface methodology to obtain dense coating. The tribological behaviors of the coated and uncoated substrates were evaluated using a ball-on-plate sliding wear tester at 37°C in simulated body-fluid conditions. The microstructure of both the titanium alloy and coated specimen were examined using an optical microscope and scanning electron microscope. The hardness of the plasma-sprayed alumina–zirconia composite coatings was 2.5 times higher than that of the Ti-6Al-4V alloy, while the wear rate of Ti-6Al-4V alloy was 253 times higher than that of the composite-coated Ti-6Al-4V alloy. The superior wear resistance of the alumina–zirconia coated alloy is attributed to its enhanced hardness and intersplat bonding strength. Wear-track examination showed that the predominant wear mechanism of Ti-6Al-4V alloy was abrasive and adhesive wear, whereas, in the case of alumina–zirconia composite coated alloy, the wear was dominated by microchipping and microcracking. PMID:26491323

  12. Theoretical Assessment on the Phase Transformation Kinetic Pathways of Multi-component Ti Alloys: Application to Ti-6Al-4V

    DOE PAGES

    Ji, Yanzhou; Heo, Tae Wook; Zhang, Fan; Chen, Long-Qing

    2015-12-21

    Here we present our theoretical assessment of the kinetic pathways during phase transformations of multi-component Ti alloys. Employing the graphical thermodynamic approach and an integrated free energy function based on the realistic thermodynamic database and assuming that a displacive structural transformation occurs much faster than long-range diffusional processes, we analyze the phase stabilities of Ti-6Al-4V (Ti-6wt.%Al-4wt.%V). Our systematic analyses predict a variety of possible kinetic pathways for β to (α + β) transformations leading to different types of microstructures under various heat treatment conditions. In addition, the possibility of unconventional kinetic pathways is discussed. Lastly, we also briefly discuss themore » application of our approach to general multicomponent/multiphase alloy systems.« less

  13. The effect of nitric acid exposure on Galileo spacecraft titanium alloy Ti-6Al-4V propellant tanks

    NASA Technical Reports Server (NTRS)

    Hsieh, Cheng; O'Donnell, Tim; Yavrouian, Andre

    1990-01-01

    The Ti-6Al-4V-constructed retropropulsion-module tanks of the Galileo spacecraft were purged with nitrogen tetroxide in order to wait out a major launch rescheduling; nitric acid is among the residual products of such an operation. A test program was conducted on representative samples to ascertain the fracture toughness and stress corrosion threshold of the tanks' material, in view of Space Shuttle safety and mission-reliability requirements. It was found that the tanks' structural integrity was not degraded by nitric acid exposure.

  14. Brazing ZrO{sub 2} ceramic to Ti–6Al–4V alloy using NiCrSiB amorphous filler foil: Interfacial microstructure and joint properties

    SciTech Connect

    Cao, J.; Song, X.G.; Li, C.; Zhao, L.Y.; Feng, J.C.

    2013-07-15

    Reliable brazing of ZrO{sub 2} ceramic and Ti–6Al–4V alloy was achieved using NiCrSiB amorphous filler foil. The interfacial microstructure of ZrO{sub 2}/Ti–6Al–4V joints was characterized by scanning electron microscope, energy dispersive spectrometer and micro-focused X-ray diffractometer. The effects of brazing temperature on the interfacial microstructure and joining properties of brazed joints were investigated in detail. Active Ti of Ti–6Al–4V alloy dissolved into molten filler metal and reacted with ZrO{sub 2} ceramic to form a continuous TiO reaction layer, which played an important role in brazing. Various reaction phases including Ti{sub 2}Ni, Ti{sub 5}Si{sub 3} and β-Ti were formed in brazed joints. With an increasing of brazing temperature, the TiO layer thickened gradually while the Ti{sub 2}Ni amount reduced. Shear test indicated that brazed joints tend to fracture at the interface between ZrO{sub 2} ceramic and brazing seam or Ti{sub 2}Ni intermetallic layer. The maximum average shear strength reached 284.6 MPa when brazed at 1025 °C for 10 min. - Graphical Abstract: Interfacial microstructure of ZrO{sub 2}/TC4 joint brazed using NiCrSiB amorphous filler foil was: ZrO{sub 2}/TiO/Ti{sub 2}Ni + β-Ti + Ti{sub 5}Si{sub 3}/β-Ti/Widmanstätten structure/TC4. - Highlights: • Brazing of ZrO{sub 2} ceramic and Ti-6Al-4V alloy was achieved. • Interfacial microstructure was TiO/Ti{sub 2}Ni + β + Ti{sub 5}Si{sub 3}/β/Widmanstätten structure. • The formation of TiO produced the darkening effect of ZrO{sub 2} ceramic. • The highest joining strength of 284.6MPa was obtained.

  15. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti-6Al-4V alloy.

    PubMed

    Ye, Xiaoxin; Wang, Lingsheng; Tse, Zion T H; Tang, Guoyi; Song, Guolin

    2015-04-01

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti-6Al-4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO2 film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects. PMID:25687017

  16. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti-6Al-4V alloy.

    PubMed

    Ye, Xiaoxin; Wang, Lingsheng; Tse, Zion T H; Tang, Guoyi; Song, Guolin

    2015-04-01

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti-6Al-4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO2 film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects.

  17. Effect of micro shot peening on the mechanical properties and corrosion behavior of two microstructure Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Ahmed, Aymen A.; Mhaede, Mansour; Wollmann, Manfred; Wagner, Lothar

    2016-02-01

    Titanium alloys continue to be used extensively for the fabrication of surgical implants due to their excellent mechanical, physical and biological performance. The surface modification is the main technique to maintain a relatively good mechanical properties and biocompatibility. In this study, a surface modification through micro shot peening (SP) using different ceramic shot (850, 450 and 125-250 μm) at 0.22 mmA have been done on two microstructures Ti-6Al-4V alloy. The effect of this treatment on the corrosion behavior, surface roughness, microhardness profiles, and residual stresses were investigated. In addition, the corrosion behavior of the ultra-fine grain of Ti-6Al-4V materials produced by rotary swaging (RS) deformation has been investigated and compared with the duplex (DU) and globular (GL) microstructures. The corrosion behavior was studied using potentiodynamic polarization and electro impedance spectroscopy techniques. The electrochemical tests were performed in Ringer's solution at 37 °C. The results show that shot peening resulted in near-surface maximum hardness and residual stresses values. Increasing the shot size led to a lower surface roughness and an improved corrosion resistance. However, SP reduces the corrosion resistance compared with the untreated materials. The globular microstructure shows high corrosion rate compared with the duplex and nanostructured materials.

  18. Accurate Descriptions of Hot Flow Behaviors Across β Transus of Ti-6Al-4V Alloy by Intelligence Algorithm GA-SVR

    NASA Astrophysics Data System (ADS)

    Wang, Li-yong; Li, Le; Zhang, Zhi-hua

    2016-09-01

    Hot compression tests of Ti-6Al-4V alloy in a wide temperature range of 1023-1323 K and strain rate range of 0.01-10 s-1 were conducted by a servo-hydraulic and computer-controlled Gleeble-3500 machine. In order to accurately and effectively characterize the highly nonlinear flow behaviors, support vector regression (SVR) which is a machine learning method was combined with genetic algorithm (GA) for characterizing the flow behaviors, namely, the GA-SVR. The prominent character of GA-SVR is that it with identical training parameters will keep training accuracy and prediction accuracy at a stable level in different attempts for a certain dataset. The learning abilities, generalization abilities, and modeling efficiencies of the mathematical regression model, ANN, and GA-SVR for Ti-6Al-4V alloy were detailedly compared. Comparison results show that the learning ability of the GA-SVR is stronger than the mathematical regression model. The generalization abilities and modeling efficiencies of these models were shown as follows in ascending order: the mathematical regression model < ANN < GA-SVR. The stress-strain data outside experimental conditions were predicted by the well-trained GA-SVR, which improved simulation accuracy of the load-stroke curve and can further improve the related research fields where stress-strain data play important roles, such as speculating work hardening and dynamic recovery, characterizing dynamic recrystallization evolution, and improving processing maps.

  19. Accurate Descriptions of Hot Flow Behaviors Across β Transus of Ti-6Al-4V Alloy by Intelligence Algorithm GA-SVR

    NASA Astrophysics Data System (ADS)

    Wang, Li-yong; Li, Le; Zhang, Zhi-hua

    2016-07-01

    Hot compression tests of Ti-6Al-4V alloy in a wide temperature range of 1023-1323 K and strain rate range of 0.01-10 s-1 were conducted by a servo-hydraulic and computer-controlled Gleeble-3500 machine. In order to accurately and effectively characterize the highly nonlinear flow behaviors, support vector regression (SVR) which is a machine learning method was combined with genetic algorithm (GA) for characterizing the flow behaviors, namely, the GA-SVR. The prominent character of GA-SVR is that it with identical training parameters will keep training accuracy and prediction accuracy at a stable level in different attempts for a certain dataset. The learning abilities, generalization abilities, and modeling efficiencies of the mathematical regression model, ANN, and GA-SVR for Ti-6Al-4V alloy were detailedly compared. Comparison results show that the learning ability of the GA-SVR is stronger than the mathematical regression model. The generalization abilities and modeling efficiencies of these models were shown as follows in ascending order: the mathematical regression model < ANN < GA-SVR. The stress-strain data outside experimental conditions were predicted by the well-trained GA-SVR, which improved simulation accuracy of the load-stroke curve and can further improve the related research fields where stress-strain data play important roles, such as speculating work hardening and dynamic recovery, characterizing dynamic recrystallization evolution, and improving processing maps.

  20. The effect of large-area pulsed electron beam melting on the corrosion and microstructure of a Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Walker, J. C.; Murray, J. W.; Nie, M.; Cook, R. B.; Clare, A. T.

    2014-08-01

    The use of titanium alloys in biomedical applications continues to increase due to the excellent stiffness to weight ratio and high corrosion resistance. In order to improve the surface wettability and corrosion properties of a Ti-6Al-4V alloy, the surface treatment method, large area electron beam melting technique was investigated. Polished samples were subject to pulsed treatments of 1, 15 and 25 at 1.38 J/cm2 beam energy. Surface roughness and contact wetting angles were reduced as a result of the treatment. Microstructural analysis of the surface by XRD and FIB-TEM revealed a martensitic alpha prime phase formed as a result of the high cooling rates induced by the treatment. The presence of this homogenous martensite layer was shown to facilitate a compact passive oxide layer formation during corrosion, thus improving corrosion rates by several orders of magnitude compared to an untreated sample. Large area electron beam melting of Ti-6Al-4V induced a number of changes to the near surface microstructure of the samples, all of which could be used to tailor mechanical and corrosion properties to that of a desired application, without compromising the bulk material properties. These are explored in detail in this work.

  1. Characteristics of Ti(C, N)/TiB composite layer on Ti-6Al-4V alloy produced by laser surface melting

    NASA Astrophysics Data System (ADS)

    Zeng, Xian; Yamaguchi, Tomiko; Nishio, Kazumasa

    2016-06-01

    A Ti(C, N)/TiB reinforced titanium matrix composite layer was successfully in-situ synthesized by laser melting on Ti-6Al-4V alloy surface with Ti-BN-C mixed powder, aiming at improving the wear resistance. The microstructure, chemical composition, hardness and wear behavior were analyzed. The results showed that, the cross sectional microstructure can be clearly divided into three parts, which were the laser melted layer, heat affected zone and non-affected zone. The reinforcements in laser melted layer consisted of dendritic TiC0.3N0.7 phases and fine-structure TiB phases. The matrix in laser melted layer was in a two-phase structure, being composed of platelet α titanium and intergranular β titanium. The hardness was increased from 320 HV in the substrate to 450-550 HV in the modified layer. The wear resistance was improved that, the wear volume loss of the laser treated sample was approximately half of the as received Ti-6Al-4V alloy after 8 h wear test.

  2. Enhanced compatibility and initial stability of Ti6Al4V alloy orthodontic miniscrews subjected to anodization, cyclic precalcification, and heat treatment

    PubMed Central

    Oh, Eun-Ju; Nguyen, Thuy-Duong T.; Lee, Seung-Youp; Jeon, Young-Mi; Bae, Tae-Sung

    2014-01-01

    Objective To evaluate the bioactivity, and the biomechanical and bone-regenerative properties of Ti6Al4V miniscrews subjected to anodization, cyclic precalcification, and heat treatment (APH treatment) and their potential clinical use. Methods The surfaces of Ti6Al4V alloys were modified by APH treatment. Bioactivity was assessed after immersion in simulated body fluid for 3 days. The hydrophilicity and the roughness of APH-treated surfaces were compared with those of untreated (UT) and anodized and heat-treated (AH) samples. For in vivo tests, 32 miniscrews (16 UT and 16 APH) were inserted into 16 Wistar rats, one UT and one APH-treated miniscrew in either tibia. The miniscrews were extracted after 3 and 6 weeks and their osseointegration (n = 8 for each time point and group) was investigated by surface and histological analyses and removal torque measurements. Results APH treatment formed a dense surface array of nanotubular TiO2 layer covered with a compact apatite-like film. APH-treated samples showed better bioactivity and biocompatibility compared with UT and AH samples. In vivo, APH-treated miniscrews showed higher removal torque and bone-to-implant contact than did UT miniscrews, after both 3 and 6 weeks (p < 0.05). Also, early deposition of densely mineralized bone around APH-treated miniscrews was observed, implying good bonding to the treated surface. Conclusions APH treatment enhanced the bioactivity, and the biomechanical and bone regenerative properties of the Ti6Al4V alloy miniscrews. The enhanced initial stability afforded should be valuable in orthodontic applications. PMID:25309864

  3. A Comparison in Mechanical Properties of Cermets of Calcium Silicate with Ti-55Ni and Ti-6Al-4V Alloys for Hard Tissues Replacement

    PubMed Central

    Pramanik, Sumit; Shirazi, Seyed Farid Seyed; Mehrali, Mehdi; Yau, Yat-Huang; Abu Osman, Noor Azuan

    2014-01-01

    This study investigated the impact of calcium silicate (CS) content on composition, compressive mechanical properties, and hardness of CS cermets with Ti-55Ni and Ti-6Al-4V alloys sintered at 1200°C. The powder metallurgy route was exploited to prepare the cermets. New phases of materials of Ni16Ti6Si7, CaTiO3, and Ni31Si12 appeared in cermet of Ti-55Ni with CS and in cermet of Ti-6Al-4V with CS, the new phases Ti5Si3, Ti2O, and CaTiO3, which were emerged during sintering at different CS content (wt%). The minimum shrinkage and density were observed in both groups of cermets for the 50 and 100 wt% CS content, respectively. The cermets with 40 wt% of CS had minimum compressive Young's modulus. The minimum of compressive strength and strain percentage at maximum load were revealed in cermets with 50 and 40 wt% of CS with Ti-55Ni and Ti-6Al-4V cermets, respectively. The cermets with 80 and 90 wt% of CS showed more plasticity than the pure CS. It concluded that the composition and mechanical properties of sintered cermets of Ti-55Ni and Ti-6Al-4V with CS significantly depend on the CS content in raw cermet materials. Thus, the different mechanical properties of the cermets can be used as potential materials for different hard tissues replacements. PMID:25538954

  4. Effects of the Heterogeneity in the Electron Beam Welded Joint on Mechanical Properties of Ti6Al4V Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Gao, Xiao-Long; Zhang, Lin-Jie; Zhang, Jian-Xun

    2015-01-01

    The aim of this investigation was to evaluate the effect of microstructure heterogeneity on the tensile and low cycle fatigue properties of electron beam welded (EBW) Ti6Al4V sheets. To achieve this goal, the tensile and low cycle fatigue property in the EBW joints and base metal (BM) specimens is compared. During the tensile testing, digital image correlation technology was used to measure the plastic strain field evolution within the specimens. The experimental results showed that the tensile ductility and low cycle fatigue strength of EBW joints are lower than that of BM specimens, mainly because of the effect of microstructure heterogeneity of the welded joint. Moreover, the EBW joints exhibit the cyclic hardening behavior during low fatigue process, while BM specimens exhibit the cyclic softening behavior. Compared with the BM specimens with uniform microstructure, the heterogeneity of microstructure in the EBW joint is found to decrease the mechanical properties of welded joint.

  5. Preparation of biomedical Ag incorporated hydroxyapatite/titania coatings on Ti6Al4V alloy by plasma electrolytic oxidation

    NASA Astrophysics Data System (ADS)

    Zhou, Lan; Lü, Guo-Hua; Mao, Fei-Fei; Yang, Si-Ze

    2014-03-01

    Nano-Ag incorporated hydroxyapatite/titania (HA/TiO2) coatings were deposited on Ti6Al4V substrates by the plasma electrolytic oxidation process. Compared with the substrate, the deposited coatings display attractive mechanical and biomedical properties. First, the coatings have stronger wear resistance and corrosion resistance. Second, they show a strong antibacterial ability. The mean vitality of the P. gingivalis on the coating surfaces is reduced to about 21%. Third, the coatings have good biocompatibility. The mean viability of the fibroblast cells on the coating surface is increased to about 130%. With these attractive properties, Ag incorporated HA/TiO2 coatings may be useful in the biomedical field.

  6. Fabrication of highly ordered TiO2 nanotube arrays via anodization of Ti-6Al-4V alloy sheet.

    PubMed

    Wang, Lei; Zhao, Ting-ting; Zhang, Zhao; Li, Gang

    2010-12-01

    Uniform and highly ordered TiO2 nanotube arrays were fabricated by the electrochemical anodic oxidation on Ti-6Al-4V surface, using graphite plate as cathode and ethylene glycol (EG) with addition of a certain amount of H2O and NH4F as electrolyte, and the anodization voltage went up to a presetting voltage by stepwise increment. The morphology, structure and composition of TiO2 nanotube arrays were characterized by SEM, EDS, XRD and XPS. The formation process of TiO2 nanotubes was introduced in brief. The experiments were arranged by an orthogonal experiment method and the experimental results showed that the formation of TiO2 nanotube arrays was influenced by not only each factor (F- content, H2O content, external voltage and duration), but also cross correlation among the four factors. The optimal condition was F- content 0.2 wt%, H2O content 4 vol%, external voltage 40 V and duration 1 h in the studied electrochemical system, and the length of obtained nanotubes was 1.5 microm, the outer diameter was approximately 100 nm and the aspect ratio was 15. As-formed nanotube arrays were amorphous and changed to anatase TiO2 after annealed at 500 degrees C for 2 h in air ambience. XPS survey spectra revealed the surface of as-formed nanotube arrays containing Ti, O, C, F and N. The nanotube arrays on Ti-6Al-4V surface with better thermo-stability and crystallinity would have great potential in biomaterials. PMID:21121333

  7. Determination of Specific Forces and Tool Deflections in Micro-milling of Ti-6Al-4V alloy using Finite Element Simulations and Analysis

    SciTech Connect

    Farina, Simone; Ceretti, Elisabetta; Thepsonti, Thanongsak; Oezel, Tugrul

    2011-05-04

    Titanium alloys offer superb properties in strength, corrosion resistance and biocompatibility and are commonly utilized in medical devices and implants. Micro-end milling process is a direct and rapid fabrication method for manufacturing medical devices and implants in titanium alloys. Process performance and quality depend upon an understanding of the relationship between cutting parameters and forces and resultant tool deflections to avoid tool breakage. For this purpose, FE simulations of chip formation during micro-end milling of Ti-6Al-4V alloy with an ultra-fine grain solid carbide two-flute micro-end mill are investigated using DEFORM software.At first, specific forces in tangential and radial directions of cutting during micro-end milling for varying feed advance and rotational speeds have been determined using designed FE simulations for chip formation process. Later, these forces are applied to the micro-end mill geometry along the axial depth of cut in 3D analysis of ABAQUS. Consequently, 3D distributions for tool deflections and von Misses stress are determined. These analyses will yield in establishing integrated multi-physics process models for high performance micro-end milling and a leap-forward to process improvements.

  8. Fabrication of dense α-alumina layer on Ti-6Al-4V alloy hybrid for bearing surfaces of artificial hip joint.

    PubMed

    Khanna, Rohit; Kokubo, Tadashi; Matsushita, Tomiharu; Takadama, Hiroaki

    2016-12-01

    Recent advances in hip replacements are focused towards producing reliable bearing surfaces to enhance their longevity. In this perspective, progressive attempts have been made to improve the wear resistance of polyethylene to eliminate osteolysis and mechanical reliability of brittle alumina ceramics, but in vain. It is proposed that both high wear resistance and mechanical reliability can be retained if a thin layer of dense alumina is formed onto high toughness Ti-6Al-4V alloy. For this purpose, we devised a unique methodology in which a layer of Al metal was deposited onto the Ti alloy substrate by cold spraying (CS), followed by a heat treatment to form Al3Ti reaction layer at their interface to improve adhesion and subsequent micro-arc oxidation (MAO) treatment to transform Al to alumina layer. An optimal MAO treatment of cold sprayed Al formed an adherent and dense α-alumina layer with high Vickers hardness matching with that of sintered alumina used as a femoral head. Structure-phase-property relationships in dense α-alumina layer have been revealed and discussed in the light of our research findings. The designed alumina/Ti alloy hybrid might be a potential candidate for reliable bearing surfaces of artificial hip joint. PMID:27612821

  9. The effect of microstructure on fatigue performance of Ti-6Al-4V alloy after EDM surface treatment for application in orthopaedics.

    PubMed

    Stráský, Josef; Janeček, Miloš; Harcuba, Petr; Bukovina, Michal; Wagner, Lothar

    2011-11-01

    Three different microstructures--equiaxed, bi-modal and coarse lamellar--are prepared from Ti-6Al-4V alloy. Electric discharge machining (EDM) with a high peak current (29 A) is performed in order to impose surface roughness and modify the chemical composition of the surface. Detailed scanning electron microscopy (SEM) investigation revealed a martensitic surface layer and subsurface heat affected zone (HAZ). EDX measurements showed carbon enriched remnants of the EDM process on the material surface. Rotating bending fatigue tests are undertaken for EDM processed samples for all three microstructures and also for electropolished-benchmark-samples. The fatigue performance is found to be rather poor and not particularly dependent on microstructure. The bi-modal microstructure shows a slightly superior high cycle fatigue performance. This performance can be further improved by a suitable heat treatment to an endurance limit of 200 MPa.

  10. Effect of electropulsing treatment and ultrasonic striking treatment on the mechanical properties and microstructure of biomedical ti-6Al-4V alloy.

    PubMed

    Ye, Xiaoxin; Ye, Yongda; Tang, Guoyi

    2014-12-01

    The effect of coupling process of high-energy electropulsing treatment and high-frequency ultrasonic striking treatment on the mechanical properties and microstructure evolution of biomedical Ti-6Al-4V alloy is investigated. Results show that the materials ductility under electropulsing treatment is noticeably improved while sacrificing the strength slightly. In this process, refined microstructure is obtained, accompanying by recrystallization process and weakened basal texture. Rapid improvement of microstructure and ductility in low temperature is attributed to accelerated atoms diffusion in recrystallization process with the coupling of thermal and athermal effects. Materials surface microhardness is dramatically enhanced by ultrasonic striking treatment and grain size reaches more than twice of original state. Plastic strain and phase change in the surface layer is contributed in ultrasonic surface strengthening effect.

  11. A study of calcium carbonate/multiwalled-carbon nanotubes/chitosan composite coatings on Ti-6Al-4V alloy for orthopedic implants

    NASA Astrophysics Data System (ADS)

    Ahmed, Rasha A.; Fekry, Amany M.; Farghali, R. A.

    2013-11-01

    In an attempt to increase the stability, bioactivity and corrosion resistance of Ti-6Al-4V alloy, chitosan (CS) biocomposite coatings reinforced with multiwalled-carbon nanotubes (MWCNTs), and calcium carbonate (CaCO3) for surface modification were utilized by electroless deposition. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) reveals the formation of a compact and highly crosslinked coatings. Electrochemical techniques were used to investigate the coats stability and resistivity for orthopedic implants in simulated body fluid (SBF). The results show that Est value is more positive in the following order: CaCO3/MWCNTs/CS > CS/MWCNTs > CS > MWCNTs. The calculated icorr was 0.02 nA cm-2 for CaCO3/MWCNTs/CS which suggested a high corrosion resistance.

  12. Faster methods for estimating arc centre position during VAR and results from Ti-6Al-4V and INCONEL 718 alloys

    NASA Astrophysics Data System (ADS)

    Nair, B. G.; Winter, N.; Daniel, B.; Ward, R. M.

    2016-07-01

    Direct measurement of the flow of electric current during VAR is extremely difficult due to the aggressive environment as the arc process itself controls the distribution of current. In previous studies the technique of “magnetic source tomography” was presented; this was shown to be effective but it used a computationally intensive iterative method to analyse the distribution of arc centre position. In this paper we present faster computational methods requiring less numerical optimisation to determine the centre position of a single distributed arc both numerically and experimentally. Numerical validation of the algorithms were done on models and experimental validation on measurements based on titanium and nickel alloys (Ti6Al4V and INCONEL 718). The results are used to comment on the effects of process parameters on arc behaviour during VAR.

  13. Low-melting-point titanium-base brazing alloys. Part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4V substrate

    SciTech Connect

    Chang, E.; Chen, C.H.

    1997-12-01

    Filler metal of a low-melting-point (917 C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 C for 2, 4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed {alpha} plus intergranular {beta} structure of Ti-6Al-4V substrate causes the lamellar Widmanstaetten structure to form. The intermetallic Ti{sub 2}Ni phase existing in the prior filler metal diminishes, while the Ti{sub 2}Cu phase can be identified for the metal brazed at 960 C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the {beta} phase to the substrate. In deaerated Hank`s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank`s solution, show similar corrosion behavior, irrespective of the brazing time.

  14. Identification of Stable Processing Parameters in Ti-6Al-4V Alloy from a Wide Temperature Range Across β Transus and a Large Strain Rate Range

    NASA Astrophysics Data System (ADS)

    Quan, Guo-Zheng; Wen, Hai-Rong; Pu, Shi-Ao; Zou, Zhen-Yu; Wu, Dong-Sen

    2015-11-01

    The hot workability of Ti-6Al-4V alloy was investigated according to the measured stress-strain data and their derived forms from a series of hot compressions at the temperatures of 1,023-1,323 K and strain rates of 0.01-10 s-1 with a height reduction of 60%. As the true strain was 0.3, 0.5, 0.7 and 0.9, respectively, the response maps of strain rate sensitivity (m-value), power dissipation efficiency (η-value) and instability parameter (ξ-value) to temperature and strain rate were developed on the basis of dynamic material model (DMM). Then the processing map was obtained by superimposition of the power dissipation and the instability maps. According to the processing map, the stable regions (η > 0 and ξ > 0) and unstable regions (η < 0 or ξ < 0) were clarified clearly. Further, the stable regions (temperatures of 1,198-1,248 K and strain rates of 0.01-0.1 s-1) with higher η value (> 0.3) corresponding to the ideal deformation mechanisms involving globularization and superplasticity were identified and recommended. The microstructures of the deformed samples were then observed by microscopy. And homogeneous microstructures with refined grains were found in the recommended parameter domains. The optimal working parameter domains identified by processing map and validated by microstructure observations contribute to the design in reasonable hot forming process of Ti-6Al-4V alloy without resorting to expensive and time-consuming trial-and-error methods.

  15. Influence of damping coefficient from permanent magnets on chatter formation during end milling of titanium alloy (Ti-6Al-4V)

    NASA Astrophysics Data System (ADS)

    Sulaiman, S. A.; Amin, A. N.

    2015-12-01

    In machining operations, chatter is undesirable due to its adverse effects on the product quality, operation cost, machining accuracy and machine tool life. It is also responsible for reducing output. Chatter is a self-excitation phenomenon occurring in machine tools, in which the cutting process tends to lower the damping capacity of the machine structural components ending in an unstable behavior of the system. Chatter arises due to resonance when the vibrations of the instability of chip formation and the natural vibration modes of the machine-system components coincide. This paper focuses on the influence of damping coefficient from permanent magnets on chip serration frequency as an approach of minimizing chatter in end milling of Titanium alloy (Ti6Al4V). The method consists of two ferrite permanent magnet bars (dimensions: 1" × 6" × 3"), mounted 5mm from the cutting tool using a specially designed fixture which provided a uniform magnetic field of 2500-2700 Gausses. A titanium alloy Ti6Al4V block was then end milled using uncoated WC-Co inserts. A sequence of 15 experimental runs was conducted based on a small Central Composite Design (CCD) model in Response Surface Methodology (RSM). The primary (independent) parameters were: cutting speed, feed, and depth of cut. The data acquisition system comprised a vibration sensor (accelerometer) and a signal conditioning unit was used to measure the vibration data. The resultant vibrations were then analyzed using the DASYLab 5.6 software. Machining tests were conducted for two different conditions - with and without the application of magnets. Scanning Electron Microscope (SEM) was used to measure the chip segmentations. The SEM analysis of chip serrations demonstrated that the chip serration frequency were more stable while cutting under the presence of permanent magnets due to lower intensity of chatter.

  16. Innovative surface modification of Ti-6Al-4V alloy with a positive effect on osteoblast proliferation and fatigue performance.

    PubMed

    Havlikova, Jana; Strasky, Josef; Vandrovcova, Marta; Harcuba, Petr; Mhaede, Mansour; Janecek, Milos; Bacakova, Lucie

    2014-06-01

    A novel approach of surface treatment of orthopaedic implants combining electric discharge machining (EDM), chemical milling (etching) and shot peening is presented in this study. Each of the three techniques have been used or proposed to be used as a favourable surface treatment of biomedical titanium alloys. But to our knowledge, the three techniques have not yet been used in combination. Surface morphology and chemistry were studied by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Fatigue life of the material was determined and finally several in-vitro biocompatibility tests have been performed. EDM and subsequent chemical milling leads to a significant improvement of osteoblast proliferation and viability thanks to favourable surface morphology and increased oxygen content on the surface. Subsequent shot-peening significantly improves the fatigue endurance of the material. Material after proposed combined surface treatment possesses favourable mechanical properties and enhanced osteoblast proliferation. EDM treatment and EDM with shot peening also supported early osteogenic cell differentiation, manifested by a higher expression of collagen type I. The combined surface treatment is therefore promising for a range of applications in orthopaedics.

  17. Osseointegration of loaded dental implant with KrF laser hydroxylapatite films on Ti6Al4V alloy by minipigs

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Himmlova, Lucia; Jelinek, Miroslav; Grivas, Christos

    2001-04-01

    This study was performed with the objective of evaluating osseointegration of titanium alloy Ti6Al4V dental implants coated with hydroxylapatite (HA) deposited by a KrF laser. For this a KrF excimer laser and stainless-steel deposition chamber were used. The thickness of the HA films was approximately 1 micrometers . IN this investigation experimental animals minipigs were used; the implants were placed vertically into the lower jaw. After 14 weeks of unloaded osseointegration, metal-ceramic crowns were inserted and, at the same time, fluorescent solution was injected into the experimental animals. Six months after insertion of crowns the animals were sacrificed. The vertical position of the implants was checked by a radiograph. Microscopic sections were cut and ground, and the sections were examined under polarized and fluorescent light using a microscope with a charge coupled device camera. The six month long osseointegration in the lower jaw has confirmed the presence of newly formed bone around all the implants. In the experimental group, which had a laser-deposited coating, the layer of fibrous connective tissue was seen only randomly. In the control group (titanium implant without a cover) the fibrous connective tissue between the implant and the newly formed bone was observed more frequently, but this difference was not significant.

  18. Fatigue Life and Short Crack Behavior in Ti-6Al-4V Alloy; Interactions of Foreign Object Damage, Stress, and Temperature

    NASA Astrophysics Data System (ADS)

    Majidi, Behzad

    2008-04-01

    High-cycle fatigue (HCF) failures associated with foreign object damage (FOD) in turbine engines of military aircrafts have been of major concern for the aeronautic industry in recent years. The present work is focused on characterizing the effects of FOD on crack initiation and small crack growth of a Ti-6Al-4V alloy at ambient and also elevated temperatures. Results show that the preferred crack initiation site depends on applied stress and temperature as maximum fractions of cracks emanating from the simulated damage site, and naturally initiated cracks are observed at 25 °C under the maximum stress of 700 MPa and at 300 °C under the maximum stress of 300 MPa. The fatigue crack growth rate is influenced by increasing temperature, and the FCG rate at 300 °C is higher than that at room temperature under the same Δ K, whereas this effect for FOD-site initiated cracks is not so remarkable. This observation seems to be due to the effect of stress relaxation at 300 °C. Results also indicate that fatigue crack initiation life ( N i ) and fatigue life ( N f ) are expressed by three-parameter Weibull distribution function.

  19. Evaluation of physicochemical properties of surface modified Ti6Al4V and Ti6Al7Nb alloys used for orthopedic implants.

    PubMed

    Basiaga, Marcin; Kajzer, Wojciech; Walke, Witold; Kajzer, Anita; Kaczmarek, Marcin

    2016-11-01

    The paper presents the results of selected functional properties of TiO2 layers deposited by ALD method on the surface of Ti6Al4V and Ti6Al7Nb alloys intended for implants in bone surgery. TiO2 layer was applied at the constant temperature of the ALD process at T=200°C at a variable number of cycles, which resulted in a different layer thickness. Different process cycles of 500, 1250, and 2500 were analyzed. The application of experimental methods (AFM, SEM, wettability, potentiodynamic test, EIS, scratch test, nanohardness and layer thickness) enabled to select the optimal number of cycles, and thus the thickness of the TiO2 layer of the most favorable functional properties. The obtained results clearly showed that regardless of the type of titanium substrate, the TiO2 layer applied in a 2500cycle ALD process has the best physicochemical and electrochemical properties. These properties have major impact on biocompatibility, and therefore the quality of the final product. The information obtained can be useful for manufacturers of medical devices involved in the production of implants used in reconstructive surgery of skeletal system. PMID:27524088

  20. Pore Geometry Optimization of Titanium (Ti6Al4V) Alloy, for Its Application in the Fabrication of Customized Hip Implants

    PubMed Central

    Roy, Sandipan; Panda, Debojyoti; Khutia, Niloy; Chowdhury, Amit Roy

    2014-01-01

    The present study investigates the mechanical response of representative volume elements of porous Ti-6Al-4V alloy, to arrive at a desired range of pore geometries that would optimize the reduction in stiffness necessary for biocompatibility with the stress concentration arising around the pore periphery, under physiological loading conditions with respect to orthopedic hip implants. A comparative study of the two is performed with the aid of a newly defined optimizing parameter called pore efficiency that takes into consideration both the stiffness quantity and the stress localization around pores. To perform a detailed analysis of the response of the porous structure over the entire spectrum of loading conditions that a hip implant is subjected to in vivo, the mechanical responses of 3D finite element models of cubic and rectangular parallelepiped geometries, with porosities varying over a range of 10% to 60%, are simulated under representative compressive, flexural as well as combined loading conditions. The results that are obtained are used to suggest a range of pore diameters that lower the effective stiffness and modulus of the implant to around 60% of the stiffness and modulus of dense solid implants while keeping the stress levels within permissible limits. PMID:25400663

  1. Charge injection properties of iridium oxide films produced on Ti-6Al-4V alloy substrates by ion-beam mixing techniques

    SciTech Connect

    Williams, J.M. ); Lee, I-S.; Buchanan, R.A. )

    1991-10-01

    The charge injection capabilities of iridium oxide films, as produced on Ti6Al-4V alloy substrates by ion beam mixing techniques, have been investigated. Iridium oxide is a valence change oxide, and therefore has high values of charge injection density upon voltage cycling in electrolytes. Because of this property, iridium oxide films are useful as working elements in neural prostheses. Iridium films of three thicknesses, produced by sputter deposition followed by ion beam mixing, were tested in cyclic voltammetry out to 1000 cycles or more. Two surface preparations, mechanical polishing and an acid passivation treatment, were also used as controls. Surface analysis was primarily by Rutherford backscattering spectrometry. Both the ion- beam mixing and the acid pretreatment increased the lifetimes of films, in comparison with the mechanically polished standards. Reductions in charge injection capability, when they occurred, were attributed to loss of Ir from the films, and there was a close correlation between the charge injection density and the Ir inventory. 13 refs., 5 figs.

  2. Effects of surface-treated cpTi and Ti6Al4V alloy on the initial attachment of human osteoblast cells.

    PubMed

    Oji, M O; Wood, J V; Downes, S

    1999-12-01

    This study concerns the effect of simple surface treatments on the nature of the oxide layer, of commercially pure titanium (cpTi) and Ti6Al4V alloy substrates and their effect on human osteoblast cells (HOBS). After treatment the surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) in order to identify the surface groups responsible for the cell attachment process. The assessment of cell attachment was monitored by the Alamar blue assay (AB), measuring cell activity, in three types of media: phosphate-buffered saline (PBS), serum containing and serum-free Dulbecco's modified Eagle's cell culture medium (SER+ and SERF respectively). XPS analysis of the treated surfaces revealed consistent peaks representative of TiO2 on all surfaces and Ti(0) and Ti2O3 on the non-heat-treated surfaces. The cell activity assays indicated that there were no significant differences in cellular activity caused by surface treatments, but the cellular activity compared between the three types of medium was greatest in the PBS over the initial stages of attachment. PMID:15347967

  3. Effects of surface-treated cpTi and Ti6Al4V alloy on the initial attachment of human osteoblast cells.

    PubMed

    Oji, M O; Wood, J V; Downes, S

    1999-12-01

    This study concerns the effect of simple surface treatments on the nature of the oxide layer, of commercially pure titanium (cpTi) and Ti6Al4V alloy substrates and their effect on human osteoblast cells (HOBS). After treatment the surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) in order to identify the surface groups responsible for the cell attachment process. The assessment of cell attachment was monitored by the Alamar blue assay (AB), measuring cell activity, in three types of media: phosphate-buffered saline (PBS), serum containing and serum-free Dulbecco's modified Eagle's cell culture medium (SER+ and SERF respectively). XPS analysis of the treated surfaces revealed consistent peaks representative of TiO2 on all surfaces and Ti(0) and Ti2O3 on the non-heat-treated surfaces. The cell activity assays indicated that there were no significant differences in cellular activity caused by surface treatments, but the cellular activity compared between the three types of medium was greatest in the PBS over the initial stages of attachment.

  4. Microvascular response of striated muscle to common arthroplasty-alloys: A comparative in vivo study with CoCrMo, Ti-6Al-4V, and Ti-6Al-7Nb.

    PubMed

    Kraft, Clayton N; Burian, Björn; Diedrich, Oliver; Gessmann, Jan; Wimmer, Markus A; Pennekamp, Peter H

    2005-10-01

    The impairment of skeletal muscle microcirculation by a biomaterial may have profound consequences. Due to excellent physical and corrosion characteristics, CoCrMo-, Ti-6Al-4V-, and Ti-6Al-7Nb-alloys are commonly used in orthopedic surgery. Yet concern has been raised with regard to the implications of inevitable corrosion product of these metals on the surrounding biologic environment, particularly in the case of CoCrMo. We, therefore, studied in vivo nutritive perfusion and leukocytic response of striated muscle to these alloys, thereby drawing conclusions on their inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we could demonstrate that the implant material CoCrMo has a marked impact on local microvascular parameters. While the Ti-alloys Ti-6Al-4V and Ti-6Al-7Nb induced only a transient and moderate inflammatory response, the implantation of a CoCrMo sample led to a distinct and persistent activation of leukocytes combined with disruption of the microvascular endothelial integrity and marked leukocyte extravasation. Animals with Ti-alloys showed a clear tendency of recuperation, while in all but one CoCrMo-treated animals, a breakdown of microcirculation prior to the scheduled end of the experiment was observed. Overall, the alloy Ti-6Al-7Nb was tolerated slightly better than Ti-6Al-4V under the chosen test conditions, though this discrepancy was not statistically significant. Conclusively, the commonly used biomaterials Ti-6Al-7Nb and Ti-6Al-4V induce a considerably lower inflammatory response in the skeletal muscle microvascular system, compared to a CoCrMo-alloy. With a minimum of adverse host reaction, our results indicate that for this particular model Ti-alloys are better tolerated than CoCrMo implant materials.

  5. A Comparative Study on Johnson Cook, Modified Zerilli-Armstrong and Arrhenius-Type Constitutive Models to Predict High-Temperature Flow Behavior of Ti-6Al-4V Alloy in α + β Phase

    NASA Astrophysics Data System (ADS)

    Cai, Jun; Wang, Kuaishe; Han, Yingying

    2016-03-01

    True stress and true strain values obtained from isothermal compression tests over a wide temperature range from 1,073 to 1,323 K and a strain rate range from 0.001 to 1 s-1 were employed to establish the constitutive equations based on Johnson Cook, modified Zerilli-Armstrong (ZA) and strain-compensated Arrhenius-type models, respectively, to predict the high-temperature flow behavior of Ti-6Al-4V alloy in α + β phase. Furthermore, a comparative study has been made on the capability of the three models to represent the elevated temperature flow behavior of Ti-6Al-4V alloy. Suitability of the three models was evaluated by comparing both the correlation coefficient R and the average absolute relative error (AARE). The results showed that the Johnson Cook model is inadequate to provide good description of flow behavior of Ti-6Al-4V alloy in α + β phase domain, while the predicted values of modified ZA model and the strain-compensated Arrhenius-type model could agree well with the experimental values except under some deformation conditions. Meanwhile, the modified ZA model could track the deformation behavior more accurately than other model throughout the entire temperature and strain rate range.

  6. Novel production method and in-vitro cell compatibility of porous Ti-6Al-4V alloy disk for hard tissue engineering.

    PubMed

    Bhattarai, Shanta Raj; Khalil, Khalil Abdel-Razek; Dewidar, Montasser; Hwang, Pyoung Han; Yi, Ho Keun; Kim, Hak Yong

    2008-08-01

    Porous metals are attractive due to its unique physical, mechanical, and new bone tissue ingrowth properties. In the present study, the production of highly porous Ti-6Al-4V parts by powder metallurgical technology and subsequently it's uses in in vitro bone tissue engineering is described. A space-holder method using carbamide with different particle size to produce parts with porosities between 35 and 70% were applied. The compressive strength and Young's modulus of porous Ti-6Al-4V were determined. Results indicated that stress and Young's modulus decrease with increasing porosity and pore size. The porous parts are characterized by scanning electron microscopy. Furthermore, study was to investigate the effects of three different porosities of porous Ti-6Al-4V (35, 50, and 70%) on proliferation, differentiation, and cell-matrix interaction of mouse osteoblast-like cells, MC-3T3. Results showed that the cell proliferation was significantly (p < 0.05) higher on 70% porous Ti-6Al-4V. However, synthesis of different types of extra cellular matrix proteins was also more abundant on 70% porous Ti-6Al-4V than 35 and 50% porous Ti-6Al-4V disk except some specific proteins. An increase in alkaline phosphate activity was significantly (p < 0.05) higher on 70 and 50% porous Ti-6Al-4V disk after 12 days of MC-3T3 cells incubation. Above all, results indicated that porosity (nearly 70%) of porous Ti-6Al-4V topography affects proliferation and differentiation of osteoblast-like MC-3T3 cells. The results showed that this novel process is a promise to fabricate porous biomaterials for bone implants.

  7. Characterization of titanium alloys for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Reytier, M.; Kircher, F.; Levesy, B.

    2002-05-01

    Titanium alloys are employed in the design of superconducting magnet support systems for their high mechanical strength associated with their low thermal conductivity. But their use requires a careful attention to their crack tolerance at cryogenic temperature. Measurements have been performed on two extra low interstitial materials (Ti-5Al-2.5Sn ELI and Ti-6Al-4V ELI) with different thickness and manufacturing process. The investigation includes the tensile properties at room and liquid helium temperatures using smooth and notched samples. Moreover, the fracture toughness has been determined at 4.2 K using Compact Tension specimens. The microstructure of the different alloys and the various fracture surfaces have also been studied. After a detailed description of the experimental procedures, practical engineering characteristics are given and a comparison of the different titanium alloys is proposed for cryogenic applications.

  8. The diameter of nanotubes formed on Ti-6Al-4V alloy controls the adhesion and differentiation of Saos-2 cells.

    PubMed

    Filova, Elena; Fojt, Jaroslav; Kryslova, Marketa; Moravec, Hynek; Joska, Ludek; Bacakova, Lucie

    2015-01-01

    Ti-6Al-4V-based nanotubes were prepared on a Ti-6Al-4V surface by anodic oxidation on 10 V, 20 V, and 30 V samples. The 10 V, 20 V, and 30 V samples and a control smooth Ti-6Al-4V sample were evaluated in terms of their chemical composition, diameter distribution, and cellular response. The surfaces of the 10 V, 20 V, and 30 V samples consisted of nanotubes of a relatively wide range of diameters that increased with the voltage. Saos-2 cells had a similar initial adhesion on all nanotube samples to the control Ti-6Al-4V sample, but it was lower than on glass. On day 3, the highest concentrations of both vinculin and talin measured by enzyme-linked immunosorbent assay and intensity of immunofluorescence staining were on 30 V nanotubes. On the other hand, the highest concentrations of ALP, type I collagen, and osteopontin were found on 10 V and 20 V samples. The final cellular densities on 10 V, 20 V, and 30 V samples were higher than on glass. Therefore, the controlled anodization of Ti-6Al-4V seems to be a useful tool for preparing nanostructured materials with desirable biological properties.

  9. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    PubMed

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase.

  10. The diameter of nanotubes formed on Ti-6Al-4V alloy controls the adhesion and differentiation of Saos-2 cells

    PubMed Central

    Filova, Elena; Fojt, Jaroslav; Kryslova, Marketa; Moravec, Hynek; Joska, Ludek; Bacakova, Lucie

    2015-01-01

    Ti-6Al-4V-based nanotubes were prepared on a Ti-6Al-4V surface by anodic oxidation on 10 V, 20 V, and 30 V samples. The 10 V, 20 V, and 30 V samples and a control smooth Ti-6Al-4V sample were evaluated in terms of their chemical composition, diameter distribution, and cellular response. The surfaces of the 10 V, 20 V, and 30 V samples consisted of nanotubes of a relatively wide range of diameters that increased with the voltage. Saos-2 cells had a similar initial adhesion on all nanotube samples to the control Ti-6Al-4V sample, but it was lower than on glass. On day 3, the highest concentrations of both vinculin and talin measured by enzyme-linked immunosorbent assay and intensity of immunofluorescence staining were on 30 V nanotubes. On the other hand, the highest concentrations of ALP, type I collagen, and osteopontin were found on 10 V and 20 V samples. The final cellular densities on 10 V, 20 V, and 30 V samples were higher than on glass. Therefore, the controlled anodization of Ti-6Al-4V seems to be a useful tool for preparing nanostructured materials with desirable biological properties. PMID:26648719

  11. Development of Laser Fabricated Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III

    2006-01-01

    Laser Engineered Net Shaping (LENS) depositions with Ti-6Al-4V gas-atomized powder were accomplished at five different temperatures, ranging from 30 to 400 C, imposed on the base plate. These base plate temperatures were employed in an effort to relieve stresses which develop during the deposition. Warpage of the base plate was monitored. Only a slight decline in warpage was observed as the base plate temperature was increased. Results indicate that substrate temperatures closer to the stress relief minimum of 480 C would relieve deposition stresses, though process parameters would likely need to be modified to compensate for the higher base plate temperature. The compositions of the as-received powder and the LENS deposited material were chemically analyzed. The oxygen content of the LENS material was 0.154 wt.% which is less than the maximum impurity limit of 0.2 percent for commercial Ti-6Al-4V alloys, but is over the limit allowed in ELI grade (0.13 percent). The level of oxygen in the commercial base plate used was only 0.0635 percent. Tensile specimens were machined from the LENS deposited material and tested in tension at room temperature. The ultimate and yield tensile stresses of the LENS material were about 1200 and 1150 MPa respectively, which is about 20 percent higher than the strengths of wrought Ti-6Al-4V. The higher strength of the LENS material was due to its fine structure and high oxygen content. The LENS deposits were not fully dense; voids were frequent at the interfaces between deposited layers. These dispersed sheets of voids were parallel to the longitudinal axis of the resulting tensile specimens. Apparently there was sufficient continuous, fully dense material longitudinally to enable the high strengths. Ductility was low in the LENS material. Percent elongation at failure in the LENS material was near 4 percent, which is less than half of what is usually expected from Ti-6Al-4V. The low ductility was caused by high oxygen levels, and the

  12. Dissimilar alloy laser beam welding of titanium: Ti-6Al-4V to Beta-C[trademark]. [Ti-3Al-8V-6Cr-4Mo-4Zr

    SciTech Connect

    Liu, P.S.; Baeslack, W.A. III . Dept. of Welding Engineering); Hurley, J. )

    1994-07-01

    CO[sub 2] laser beam welds were produced between Ti-6Al-4V and Beta-C[trademark] sheet. Three different nominal fusion zone chemical compositions were obtained by varying the laser beam location relative to the joint centerline and thereby melting different quantities of each base metal. Fusion zone microstructures exhibited fine, columnar-shaped beta grains comprised of retained-beta phase and martensite, with the proportion of martensite increasing with an increase in the quantity of Ti-6Al-4V nominally in the fusion zone. The location of these phases within the fusion zone was influenced by macrosegregation, which originated from incomplete mixing of the melted base metals and the occurrence of transverse-solute banding during solidification. Postweld aging heat treatment at 482 C/20 h and 538 C/8 h resulted in extremely fine alpha precipitation within the retained-beta phase regions and tempering of the martensite. These fusion zone microstructures exhibited high hardnesses and strengths superior to those of the Ti-6Al-4V and Beta-C base metals, but low ductility (<2.5%). An increase in the aging temperature to 593 C promoted fusion zone transformation to a coarser intragranular and grain-boundary alpha + beta microstructure, which exhibited a strength superior to those of the base metals and acceptable ductility. Variations in the proportions of Ti-6Al-4V and Beta C within the weld fusion zone generally had a minimal effect on the average hardness and ductility.

  13. Surface modification by alkali and heat treatments in titanium alloys.

    PubMed

    Lee, Baek-Hee; Do Kim, Young; Shin, Ji Hoon; Hwan Lee, Kyu

    2002-09-01

    Pure titanium and titanium alloys are normally used for orthopedic and dental prostheses. Nevertheless, their chemical, biological, and mechanical properties still can be improved by the development of new preparation technologies. This has been the limiting factor for these metals to show low affinity to living bone. The purpose of this study is to improve the bone-bonding ability between titanium alloys and living bone through a chemically activated process and a thermally activated one. Two kinds of titanium alloys, a newly designed Ti-In-Nb-Ta alloy and a commercially available Ti-6Al-4V ELI alloy, were used in this study. In this study, surface modification of the titanium alloys by alkali and heat treatments (AHT), alkali treated in 5.0M NaOH solution, and heat treated in vacuum furnace at 600 degrees C, is reported. After AHT, the effects of the AHT on the bone integration property were evaluated in vitro. Surface morphologies of AHT were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Chemical compositional surface changes were investigated by X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS), and auger electron spectroscopy (AES). Titanium alloys with surface modification by AHT showed improved bioactive behavior, and the Ti-In-Nb-Ta alloy had better bioactivity than the Ti-6Al-4V ELI alloy in vitro.

  14. Determination of structural, mechanical and corrosion properties of Nb2O5 and (NbyCu 1-y)Ox thin films deposited on Ti6Al4V alloy substrates for dental implant applications.

    PubMed

    Mazur, M; Kalisz, M; Wojcieszak, D; Grobelny, M; Mazur, P; Kaczmarek, D; Domaradzki, J

    2015-02-01

    In this paper comparative studies on the structural, mechanical and corrosion properties of Nb2O5/Ti and (NbyCu1-y)Ox/Ti alloy systems have been investigated. Pure layers of niobia and niobia with a copper addition were deposited on a Ti6Al4V titanium alloy surface using the magnetron sputtering method. The physicochemical properties of the prepared thin films were examined with the aid of XRD, XPS SEM and AFM measurements. The mechanical properties (i.e., nanohardness, Young's modulus and abrasion resistance) were performed using nanoindentation and a steel wool test. The corrosion properties of the coatings were determined by analysis of the voltammetric curves. The deposited coatings were crack free, exhibited good adherence to the substrate, no discontinuity of the thin film was observed and the surface morphology was homogeneous. The hardness of pure niobium pentoxide was ca. 8.64GPa. The obtained results showed that the addition of copper into pure niobia resulted in the preparation of a layer with a lower hardness of ca. 7.79 GPa (for niobia with 17 at.% Cu) and 7.75 GPa (for niobia with 25 at.% Cu). The corrosion properties of the tested thin films deposited on the surface of titanium alloy depended on the composition of the thin layer. The addition of copper (i.e. a noble metal) to Nb2O5 film increased the corrosion resistance followed by a significant decrease in the value of corrosion currents and, in case of the highest Cu content, the shift of corrosion potential towards the noble direction. The best corrosion properties were obtained from a sample of Ti6Al4V coated with (Nb0.75Cu0.25)Ox thin film. It seems that the tested materials could be used in the future as protection coatings for Ti alloys in biomedical applications such as implants.

  15. Mechanical properties of Ti(C 0.7N 0.3) film produced by plasma electrolytic carbonitriding of Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Li, Xin-Mei; Han, Yong

    2008-08-01

    Porous nanocrystalline Ti(C 0.7N 0.3) film on Ti6Al4V substrate was prepared by plasma electrolytic carbonitriding (PECN). The film was characterized and analyzed by using a variety of analytical techniques, such as XRD, SEM, EDX, TEM, FESEM, Rockwell C indenter, scratch tester, Vickers microhardness tester and ring-on-block tribometer. The results showed that the film was about 15 μm thick and its hardness was Hv 2369 at a load of 0.2 N. The adhesion of the film was characterized by Lc and Pc value, and was found to be about 42 N and more than 800 N, respectively. The friction coefficients and wear volume loss of the PECN-treated samples sliding against a steel counterpart were much less than those of the untreated Ti6Al4V. The film possessed a good wear-resistance and antifriction under oil-lubricated condition due to its high hardness, adhesion and fracture toughness. Also, the porous surface morphology of the Ti(C 0.7N 0.3) film contributed to the enhanced tribological resistance by promoting the formation of lubricant film and entrapping wear debris.

  16. Growth of aluminum-free porous oxide layers on titanium and its alloys Ti-6Al-4V and Ti-6Al-7Nb by micro-arc oxidation.

    PubMed

    Duarte, Laís T; Bolfarini, Claudemiro; Biaggio, Sonia R; Rocha-Filho, Romeu C; Nascente, Pedro A P

    2014-08-01

    The growth of oxides on the surfaces of pure Ti and two of its ternary alloys, Ti-6Al-4V and Ti-6Al-7Nb, by micro-arc oxidation (MAO) in a pH 5 phosphate buffer was investigated. The primary aim was to form thick, porous, and aluminum-free oxide layers, because these characteristics favor bonding between bone and metal when the latter is implanted in the human body. On Ti, Ti-6Al-4 V, and Ti-6Al-7Nb, the oxides exhibited breakdown potentials of about 200 V, 130 V, and 140 V, respectively, indicating that the oxide formed on the pure metal is the most stable. The use of the MAO procedure led to the formation of highly porous oxides, with a uniform distribution of pores; the pores varied in size, depending on the anodizing applied voltage and time. Irrespective of the material being anodized, Raman analyses allowed us to determine that the oxide films consisted mainly of the anatase phase of TiO2, and XPS results indicated that this oxide is free of Al and any other alloying element.

  17. Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants

    NASA Astrophysics Data System (ADS)

    Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru

    2013-02-01

    Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.

  18. Effect of Surface Modifications of Ti40Zr10Cu38Pd12 Bulk Metallic Glass and Ti-6Al-4V Alloy on Human Osteoblasts In Vitro Biocompatibility

    PubMed Central

    Blanquer, Andreu; Hynowska, Anna; Nogués, Carme; Ibáñez, Elena; Sort, Jordi; Baró, Maria Dolors; Özkale, Berna; Pané, Salvador; Pellicer, Eva

    2016-01-01

    The use of biocompatible materials, including bulk metallic glasses (BMGs), for tissue regeneration and transplantation is increasing. The good mechanical and corrosion properties of Ti40Zr10Cu38Pd12 BMG and its previously described biocompatibility makes it a potential candidate for medical applications. However, it is known that surface properties like topography might play an important role in regulating cell adhesion, proliferation and differentiation. Thus, in the present study, Ti40Zr10Cu38Pd12 BMG and Ti6-Al-4V alloy were surface-modified electrochemically (nanomesh) or physically (microscratched) to investigate the effect of material topography on human osteoblasts cells (Saos-2) adhesion, proliferation and differentiation. For comparative purposes, the effect of mirror-like polished surfaces was also studied. Electrochemical treatments led to a highly interconnected hierarchical porous structure rich in oxides, which have been described to improve corrosion resistance, whereas microscratched surfaces showed a groove pattern with parallel trenches. Cell viability was higher than 96% for the three topographies tested and for both alloy compositions. In all cases, cells were able to adhere, proliferate and differentiate on the alloys, hence indicating that surface topography plays a minor role on these processes, although a clear cell orientation was observed on microscratched surfaces. Overall, our results provide further evidence that Ti40Zr10Cu38Pd12 BMG is an excellent candidate, in the present two topographies, for bone repair purposes. PMID:27243628

  19. Characterization of Ti-6%Al-4%V and VascoMax C-350

    SciTech Connect

    Sunwoo, A J

    2005-02-07

    The {alpha}-{beta} Ti-6% Al-4% V (Ti64) alloy can be heat treated to meet the specified requirements of the applications. The as-received material from SLAC was given a solution heat treatment (SHT) to have a good strength and ductility combination. The SHT was done at 200 C below the Beta transus of 990 C for 15 min and air-cooled to 20 C. The designed microstructure consists of {beta} phase precipitates within the {alpha} phase matrix. The characterization of the as-received Ti64 alloy sheet microstructure reveals equiaxed, 10 {micro}m-sized grains on the flat surface and finer, 8 {micro}m-sized grains in the through thickness. Figures 1 and 2 show the microstructure of the alloy. The typical Ti64 microstructure is lamellar structure, consisting of alternating {alpha} and {beta} phases. In order for the alloy to have the micron sized, equiaxed grains, it had to undergo extensive wrought processing. The Vicker's microhardness numbers (VHN) showed that the slightly larger grained flat surface had a higher averaged value than the through thickness; 33 kg/mm{sup 2} vs. 30 kg/mm{sup 2}. The residual effect of wrought processing is still present even after the SHT to cause the small difference in the hardness values. The results of tensile tests conducted at LLNL and at BNL are given in Tables 2 and 1 in Appendices 1 and 2, respectively. The effects of the irradiation dosage damage on the tensile properties of the Ti64 are presented in Appendix 2. The as-received tensile specimens are not the standard specimens for testing. As shown in Attachment, Figure 1, only the 6 mm length is used in the reduced gage section of the specimens. As a result, a small change in the gage length will translate to a higher percentage change in elongation, giving higher elongation values than using the 30 mm length of the specimen. Since most of the deformation is concentrated in the reduced gage section, the present results are more accurate measurement of ductility. The Ti64 specimens

  20. Characterization and friction behavior of LST/PEO duplex-treated Ti6Al4V alloy with burnished MoS2 film

    NASA Astrophysics Data System (ADS)

    Qin, Yongkun; Xiong, Dangsheng; Li, Jianliang

    2015-08-01

    Laser surface-textured Ti6Al4V substrate was treated by plasma electrolytic oxidation process to prepare an oxide ceramic coating and then burnished with a thin MoS2 film. The area densities of textured dimples and the surface roughness of oxide ceramic underlay which affected the longevity of MoS2 films were thoroughly investigated. The results showed that a mixed surface pattern combining large textured dimples (diameter 150 μm) with small discharged dimples (diameter 5-17 μm) was fabricated by the LST/PEO duplex treatment and it contributed to prolonging the lubricating life of MoS2 film in comparison to the LST or PEO treatment. Wherein, the mixed dimples acted as lubricant reservoirs and the hard oxide coatings provided high load supports for the lubricating films. A much longer life of low friction was provided by the LST/PEO/MoS2 coatings with higher density of textured dimples (S = 55%) and lower roughness of LST/PEO surface (Ra = 1.0 μm).

  1. In situ strain profiling of elastoplastic bending in Ti-6Al-4V alloy by synchrotron energy dispersive x-ray diffraction

    SciTech Connect

    Croft, M.; Shukla, V.; Akdogan, E. K.; Sadangi, R.; Ignatov, A.; Balarinni, L.; Tsakalakos, T.; Jisrawi, N.; Zhong, Z.; Horvath, K.

    2009-05-01

    Elastic and plastic strain evolution under four-point bending has been studied by synchrotron energy dispersive x-ray diffraction. Measured strain profiles across the specimen thickness showed an increasing linear elastic strain gradient under increasing four-point bending load up to approx2 kN. The bulk elastic modulus of Ti-6Al-4V was determined as 118 GPa. The onset of plastic deformation was found to set in at a total in-plane strain of approx0.008, both under tension and compression. Plastic deformation under bending is initiated in the vicinity of the surface and at a stress of 1100 MPa, and propagates inward, while a finite core region remains elastically deformed up to 3.67 kN loading. The onset of the plastic regime and the plastic regime itself has been verified by monitoring the line broadening of the (100) peak of alpha-Ti. The effective compression/tension stress-strain curve has been obtained from the scaling collapse of strain profile data taken at seven external load levels. A similar multiple load scaling collapse of the plastic strain variation has also been obtained. The level of precision in strain measurement reported herein was evaluated and found to be 1.5x10{sup -5} or better.

  2. Mechanical characterization of Ti-6Al-4V titanium alloy at multiple length scales using spherical indentation stress-strain measurements

    DOE PAGES

    Weaver, Jordan S.; Kalidindi, Surya R.

    2016-09-05

    Recent advances in spherical indentation stress-strain protocols and analyses have demonstrated the capability for measuring reliably the local mechanical responses in polycrystalline metal samples at different length scales, ranging from sub-micron (regions within individual grains) to several hundreds of microns (regions covering several grains). These recent advances have now made it possible to study systematically the mechanical behavior of a single material system at different length scales, with tremendous potential to obtain new insights into the role of individual phases, interfaces, and other microscale constituents on the macroscale mechanical response of the material. In this paper, we report spherical indentationmore » stress-strain measurements with different indenter sizes (microns to millimeters) on Ti-6Al-4V (Ti-64) which capture the mechanical response of single phase alpha-Ti-64, single colony (alpha-beta), few colonies, and many colonies of Ti-64. The results show that the average mechanical response (indentation modulus and yield strength) from multiple indentations remains relatively unchanged from single phase alpha to many colonies of Ti-64, while the variance in the response decreases with indenter size. In conclusion, the work-hardening response in indentation tests follows a similar behavior up to indentation zones of many colonies, which shows significantly higher work hardening rates.« less

  3. 78 FR 49723 - Humboldt-Toiyabe National Forests; Ely Ranger District; Ely Westside Rangeland Project

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-15

    ... Forest Service Humboldt-Toiyabe National Forests; Ely Ranger District; Ely Westside Rangeland Project... of the Ely Westside Rangeland Project began in 2006 with the original Notice of Intent published in... and conditions) on the allotments in the Ely Westside Rangeland Project area. The objection...

  4. Materials data handbook. Titanium 6Al-4V

    NASA Technical Reports Server (NTRS)

    Muraca, R. F.; Whittick, J. S.

    1972-01-01

    A summary of the materials property information for Titanium 6Al-4V alloy is presented. The scope of the information includes physical and mechanical properties at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy of the alloy, corrosion, environmental effects, fabrication, and bonding is developed.

  5. Effect of the surface oxidization and nitridation on the normal spectral emissivity of titanium alloys Ti-6Al-4V at 800-1100 K at a wavelength of 1.5 μm

    NASA Astrophysics Data System (ADS)

    Zhu, Wenjie; Shi, Deheng; Zhu, Zunlue; Sun, Jinfeng

    2016-05-01

    This work strived to model the effect of surface oxidization and nitridation on the normal spectral emissivity of Ti-6Al-4V alloys at a temperature range of 800-1100 K and a wavelength of 1.5 μm. In experiments, the detector was as close to perpendicular to the surface of the specimens as possible so that only the normal spectral emissivity was measured. Two thermocouples were symmetrically welded near the measuring area for accurate measuring and monitoring of the temperature at the surface of the specimen. The specimens were heated for 6 h at a certain temperature. During this period, the normal spectral emissivity values were measured once every 1 min during the initial 180 min, and once every 2 min thereafter. The measurements were made at certain temperatures from 800 to 1100 K in intervals of 20 K. One strong oscillation in the normal spectral emissivity was observed at each temperature. The oscillations were formed by the interference between the radiation stemming from the oxidization and nitridation layer on the specimen surface and radiation from the substrate. The uncertainty in the normal spectral emissivity caused only by the surface oxidization and nitridation was found to be approximately 9.5-22.8%, and the corresponding uncertainty in the temperature generated only by the surface oxidization and nitridation was approximately 6.9-15.5 K. The model can reproduce well the normal spectral emissivity, including the strong oscillation that occurred during the initial heating period.

  6. Effect of outdoor exposure at ambient and elevated temperatures on fatigue life of Ti-6Al-4V titanium alloy sheet in the annealed and the solution treated and aged condition

    NASA Technical Reports Server (NTRS)

    Phillips, E. P.

    1974-01-01

    Specimens of Ti-6Al-4V titanium alloy sheet in the annealed and the solution-treated and aged heat-treatment condition were exposed outdoors at ambient and 560 K (550 F) temperatures to determine the effect of outdoor exposure on fatigue life. Effects of exposure were determined by comparing fatigue lives of exposed specimens to those of unexpected specimens. Two procedures for fatigue testing the exposed specimens were evaluated: (1) fatigue tests conducted outdoors by applying 1200 load cycles per week until failure occurred and (2) conventional fatigue tests (continuous cycling until failure occurred) conducted indoors after outdoor exposure under static load. The exposure period ranged from 9 to 28 months for the outdoor fatigue-test group and was 24 months for the static-load group. All fatigue tests were constant-amplitude bending of specimens containing a drilled hole (stress concentration factor of 1.6). The results of the tests indicate that the fatigue lives of solution-treated and aged specimens were significantly reduced by the outdoor exposure at 560 K but not by the exposure at ambient temperature. Fatigue lives of the annealed specimens were essentially unaffected by the outdoor exposure at either temperature. The two test procedures - outdoor fatigue test and indoor fatigue test after outdoor exposure - led to the same conclusions about exposure effects.

  7. Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy.

    PubMed

    Zhang, Wei; Chen, Xianchun; Liao, Xiaoming; Huang, Zhongbing; Dan, Xiuli; Yin, Guangfu

    2011-10-01

    The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved.

  8. Deformation Behavior and Microstructure of Ti6Al4V Manufactured by SLM

    NASA Astrophysics Data System (ADS)

    Krakhmalev, P.; Fredriksson, G.; Yadroitsava, I.; Kazantseva, N.; Plessis, A. du; Yadroitsev, I.

    Mechanical properties, porosity, and microstructure of Ti6Al4V (ELI) material produced by Selective Laser Melting (SLM) under controlled oxygen content were analyzed. Fully martensitic α'structure with high dislocation density and stacking faults was observed in both as-built and stress relieved samples by means of XRD and TEM. Tensile {101 ̅2} twinning was identified by TEM and electron diffraction. Accommodation of thermal stresses during manufacturing was suggested as a possible reason for twinning. Computed tomography of pores was carried out. Pores in the specimens were evenly distributed and mostly had an elongated shape. Defect analysis by micro CT scans in pre-strained samples confirmed that the pore coalescence was the main crack formation mechanism in the final fracture with typical cup-and-cone fracture morphology. Additionally, typical dimples and quasi-cleavage were revealed. Mechanical properties of the samples after stress relieving heat treatment at 650°C for 3 h are complied with the international standard for Ti alloys for biomedical applications.

  9. Local zone wise elastic and plastic properties of electron beam welded Ti-6Al-4V alloy using digital image correlation technique: A comparative study between uniform stress and virtual fields method

    NASA Astrophysics Data System (ADS)

    Saranath, K. M.; Ramji, M.

    2015-05-01

    Joining of materials using welding results in the formation of material zones with varying microstructure across the weld. Extraction of the mechanical properties of those individual heterogeneous zones are important in designing components and structures comprised of welds. In this study, the zone wise local extraction of the elastic and plastic properties of an electron beam welded Ti-6Al-4V titanium alloy has been carried out using both the uniform stress method (USM) and the virtual fields method (VFM) involving digital image correlation (DIC) technique. The surface strain field obtained using DIC technique from a transverse weld specimen tensile testing is used for extracting the zone wise strain evolution. Initially, using uniform stress assumption, zone wise full range stress-strain curves are extracted. In USM methodology, the elastic and plastic material models are fitted to the zone wise stress-strain curves and required parameters are extracted from it. But inherent disadvantage is lot of images need to be processed for the parameter extraction. Recently, VFM is gaining lot of popularity in characterization domain as it is robust, accurate and faster. VFM is based on the principle of virtual work where, the weak form of local equilibrium equations and kinematically admissible virtual displacement fields are utilized for parameter extraction. Hollomon's power law is used here as the hardening rule. Young's modulus, Poisson's ratio, yield stress, strength coefficient and strain hardening exponent are the parameters extracted zone wise using both USM and VFM. A Vicker's microhardness measurement is also conducted across the weld zone towards mapping the strength behavior. Fusion zone has reported higher yield strength, strength coefficient and Poisson's ratio. Young's modulus value is found decreasing from base metal towards the fusion zone. The trend observed in parameter variation across the weld zone obtained by both USM and VFM compares very well. Due

  10. Investigation on Tool Life and Surface Integrity when Drilling Ti-6Al-4V and Ti-5Al-4V-Mo/Fe

    NASA Astrophysics Data System (ADS)

    Rahim, Erween Abd.; Sharif, Safian

    Machinability study on the drilling of two alpha beta titanium alloy series, Ti-6Al-4V and Ti-5Al-4V-0.6Mo-0.4Fe were conducted using an uncoated carbide drill. The effect of cutting speed on tool life, tool failure mode, cutting force and surface integrity of the drilled surface were discussed. Results showed that Ti-6Al-4V exhibited a more superior machinability property when compared to the Ti-5Al-4V-Mo/Fe alloy system. The tool wear progression when drilling Ti-6Al-4V was lower than that of Ti-5Al-4V-Mo/Fe. The tool experienced similar failure mechanisms which were non uniform wear and chipping when drilling both alloys. At high cutting speed and after prolonged machining, excessive plastic deformation was observed on the subsurface layer of the drilled surface which resulted in increase in the hardness value.

  11. Behavior of Ni-Cr-Si coating alloys in Na/sub 2/SO/sub 4/, V/sub 2/O/sub 5/, and mixed salt hot corrosion. Final report

    SciTech Connect

    Corey, R.G.; Khan, A.S.; Barkalow, R.H.; Hecht, R.J.

    1983-10-01

    This report describes the results of a program to select coating alloys that are resistant to vanadium- and sulfate-induced hot corrosion and solid particle erosion in the 700 to 900/sup 0/C temperature range. Test materials, methods, and results are discussed. The principal alloy coatings that were tested were high-chromium, nickel-base alloys with additions of silicon, aluminum, and tantalum.

  12. On the fatigue behavior of medical Ti6Al4V roughened by grit blasting and abrasiveless waterjet peening.

    PubMed

    Lieblich, M; Barriuso, S; Ibáñez, J; Ruiz-de-Lara, L; Díaz, M; Ocaña, J L; Alberdi, A; González-Carrasco, J L

    2016-10-01

    Flat fatigue specimens of biomedical Ti6Al4V ELI alloy were surface-processed by high pressure waterjet peening (WJP) without abrasive particles using moderate to severe conditions that yield roughness values in the range of those obtained by commercial grit blasting (BL) with alumina particles. Fatigue behavior of WJP and BL specimens was characterized under cyclical uniaxial tension tests (R=0.1). The emphasis was put on a comparative analysis of the surface and subsurface induced effects and in their relevance on fatigue behavior. Within the experimental setup of this investigation it resulted that blasting with alumina particles was less harmful for fatigue resistance than abrasiveless WJP. BL specimens resulted in higher subsurface hardening and compressive residual stresses. Specimens treated with more severe WJP parameters presented much higher mass loss and lower compressive residual stresses. From the analysis performed in this work, it follows that, in addition to roughness, waviness emerges as another important topographic parameter to be taken into account to try to predict fatigue behavior. It is envisaged that optimization of WJP parameters with the aim of reducing waviness and mass loss should lead to an improvement of fatigue resistance.

  13. On the fatigue behavior of medical Ti6Al4V roughened by grit blasting and abrasiveless waterjet peening.

    PubMed

    Lieblich, M; Barriuso, S; Ibáñez, J; Ruiz-de-Lara, L; Díaz, M; Ocaña, J L; Alberdi, A; González-Carrasco, J L

    2016-10-01

    Flat fatigue specimens of biomedical Ti6Al4V ELI alloy were surface-processed by high pressure waterjet peening (WJP) without abrasive particles using moderate to severe conditions that yield roughness values in the range of those obtained by commercial grit blasting (BL) with alumina particles. Fatigue behavior of WJP and BL specimens was characterized under cyclical uniaxial tension tests (R=0.1). The emphasis was put on a comparative analysis of the surface and subsurface induced effects and in their relevance on fatigue behavior. Within the experimental setup of this investigation it resulted that blasting with alumina particles was less harmful for fatigue resistance than abrasiveless WJP. BL specimens resulted in higher subsurface hardening and compressive residual stresses. Specimens treated with more severe WJP parameters presented much higher mass loss and lower compressive residual stresses. From the analysis performed in this work, it follows that, in addition to roughness, waviness emerges as another important topographic parameter to be taken into account to try to predict fatigue behavior. It is envisaged that optimization of WJP parameters with the aim of reducing waviness and mass loss should lead to an improvement of fatigue resistance. PMID:27454525

  14. [Study on biocompatibility of titanium alloys].

    PubMed

    Kodama, T

    1989-06-01

    The biocompatibility of two different titanium alloys, Ti-6Al-4V ELI and Ti-5Al-2, 5Fe, and pure titanium were evaluated. The results were as follows: 1) Titanium alloys were implanted into the dorsal subcutaneous tissues of the Hartley guinea-pig for 12 weeks, immersed in calf serum or in Ringer's solution for 8 weeks. The surface changes of the titanium alloys were observed by SEM and the chemical composition was analyzed by XMA. No evident surface changes were found. 2) Three hundred mg, 200 mg and 100 mg of the powders of the tested materials were immersed in 2ml of Eagle's MEM, incubated for 1-7 days, 8-21 days and 22-70 days at 37 C degrees. The amount of metallic elements dissolved in the solutions was measured by ICP and AAS. The detected corrosion rates of V and Al contained in the solution, in which Ti-6Al-4V ELI 100 mg was immersed for 1-7 days, were 194.3 +/- 17.6 and 73.0 +/- 28, 1 pg/mg alloy/day, respectively. V was released more than Al. The amount of Ti was below the detectable limit. The solution Ti-5Al-2.5 Fe 100 mg immersed for 1-7 days contained 31.9 +/- 34.4 pg/mg alloy/day Fe and 25.7 +/- 6.3 pg/mg alloy/day Al. Only in the solution 300 mg immersed for 1-7 days was Ti detected at 1.4 pg/mg alloy/day. 3) By the bacterial mutation assay of Salmonella typhimurium TA 98, Salmonella typhimurium TA 100 and Escherichia coli WP2 uvrA, the solutions, in which the tested materials were immersed, were not found to be mutagenic. 4) By the UDS assay, the grain counts on autoradiography with the solutions, in which the tested materials were immersed, were not greater than the negative control. The results suggest an excellent corrosion resistance of the titanium alloys. Mutagenicity was negative by these mutation assays, indicating that the tested alloys and pure titanium are safe for humans and animals.

  15. "ELI"--The Educational Futures Game.

    ERIC Educational Resources Information Center

    Mahoney, V. L. Mike; Grantham, Lex

    This report describes ELI, a computer-based educational game that gives participants, as citizens of fictitious cities, the opportunity to examine a variety of typical community issues relating to education within the context of broader city and regional problems. After a brief introduction, the game structure is described, including the setting…

  16. Fatigue performance and cyto-toxicity of low rigidity titanium alloy, Ti-29Nb-13Ta-4.6Zr.

    PubMed

    Niinomi, Mitsuo

    2003-07-01

    A beta type titanium alloy, Ti-29Nb-13Ta-4.6Zr, was newly designed and developed for biomedical applications. The new alloy contains non-toxic elements such as Nb, Ta, and Zr. In the present study, phases that appeared in the new alloy through various aging treatments were characterized by hardness tests and microstructural observations in order to identify the phase transformation. Fatigue properties of the new alloy were investigated. Young's modulus and cyto-toxicity of the new alloy were also evaluated. Precipitated phases distribute homogeneously over the whole specimen, and they are alpha phase, a small amount of omega phase, and beta phase when the new alloys are subjected to aging treatment at 673K for 259.2ks after solution treatment at 1063K for 3.6ks. The fatigue strength of the new alloy subjected to aging at 673K for 259.2ks after solution treatment at 1063K for 3.6ks is much better than when subjected to other aging treatments. In this case, the fatigue limit is around 700MPa. Young's modulus of the new alloy is much smaller than that of Ti-6Al-4V ELI. The cyto-toxicity of the new alloy is equivalent to that of pure Ti. Therefore, it is proposed that the new alloy, Ti-29Nb-13Ta-4.6Zr, will be of considerable use in biomedical applications.

  17. Gamma beam system at ELI-NP

    SciTech Connect

    Ur, Calin Alexandru

    2015-02-24

    The Gamma Beam System of ELI-NP will produce brilliant, quasi-monochromatic gamma-ray beams via Inverse Compton Scattering of short laser pulses on relativistic electron beam pulses. The scattered radiation is Doppler upshifted by more than 1,000,000 times and is forward focused in a narrow, polarized, tunable, laser-like beam. The gamma-ray beam at ELI-NP will be characterized by large spectral density of about 10{sup 4} photons/s/eV, narrow bandwidth (< 0.5%) and tunable energy from 200 keV up to about 20 MeV. The Gamma Beam System is a state-of-the-art equipment employing techniques and technologies at the limits of the present-day's knowledge.

  18. Fatigue properties of a metastable beta-type titanium alloy with reversible phase transformation.

    PubMed

    Li, S J; Cui, T C; Hao, Y L; Yang, R

    2008-03-01

    Due to recent concern about allergic and toxic effects of Ni ions released from TiNi alloy into human body, much attention has been focused on the development of new Ni-free, metastable beta-type biomedical titanium alloys with a reversible phase transformation between the beta phase and the alpha'' martensite. This study investigates the effect of the stress-induced alpha'' martensite on the mechanical and fatigue properties of Ti-24Nb-4Zr-7.6Sn (wt.%) alloy. The results show that the as-forged alloy has a low dynamic Young's modulus of 55GPa and a recoverable tensile strain of approximately 3%. Compared with Ti-6Al-4V ELI, the studied alloy has quite a high low-cycle fatigue strength because of the effective suppression of microplastic deformation by the reversible martensitic transformation. Due to the low critical stress required to induce the martensitic transformation, it has low fatigue endurance comparable to that of Ti-6Al-4V ELI. Cold rolling produces a beta+alpha'' two-phase microstructure that is characterized by regions of nano-size beta grains interspersed with coarse grains containing alpha'' martensite plates. Cold rolling increases fatigue endurance by approximately 50% while decreasing the Young's modulus to 49GPa along the rolling direction but increasing it to 68GPa along the transverse direction. Due to the effective suppression of the brittle isothermal omega phase, balanced properties of high strength, low Young's modulus and good ductility can be achieved through ageing treatment at intermediate temperature.

  19. Laser remelting of Ti6AL4V using high power diode laser

    NASA Astrophysics Data System (ADS)

    Amaya-Vázquez, M. R.; Sánchez-Amaya, J. M.; Boukha, Z.; El Amrani, K.; Botana, F. J.

    2012-04-01

    Titanium alloys present excellent mechanical and corrosion properties, being widely employed in different industries such as medical, aerospace, automotive, petrochemical, nuclear and power generation, etc. Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with convectional heat treatments and/or with laser processing. Laser remelting (LR) is a technology applied to Ti6Al4V by other authors with excimer and Nd-Yag laser with pure argon shielding gas to prevent risk of oxidation. In the present contribution, laser remelting has been applied for the first time to Ti6Al4V with a high power diode laser (with pure argon as shielding gas). Results showed that remelted samples (with medium energy densities) have higher microhardness and better corrosion resistance than Ti6Al4V base metal.

  20. Water droplet erosion mechanisms of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Kamkar Zahmatkesh, Niloofar

    Water impingement erosion of materials can be a life-limiting phenomenon for the components in many erosive environments. For example, aircraft body exposed to rain, steam turbine blade, and recently in gas turbine coupled with inlet fogging system. The last is the focus of this study. Inlet fogging system is the most common method used to augment gas turbine output during hot days; high ambient temperature causes strong deterioration of the engine performance. Micro-scaled droplets introduced into the inlet airflow allow the cooling of entering air as well as intercooling the compressor (overspray) and thus optimizes the output power. However, erosion damage of the compressor blades in overspray stage is one of the major concerns associated with the inlet fogging system. The main objective of this research work (CRIAQ MANU419 project) is to understand the erosion induced by water droplets on Titanium alloy to eventually optimize the erosion resistance of the Ti-based compressor blade. Therefore, characterization of the water droplet erosion damage on Ti-6Al-4V receives the major importance. The influence of base material microstructure and impact parameters were considered in erosion evaluation in present study. This work covers the characterization of the erosion damage on Ti-6Al-4V alloy in two parts: - The water droplet erosion damage through a novel experimental approach. The collected data were processed both qualitatively and quantitatively for multi-aspects damage study. - The influence of impact velocity on erosion in an attempt to represent the in-service conditions.

  1. Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques

    NASA Astrophysics Data System (ADS)

    Chan, Kwai S.

    2015-12-01

    Rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti-6Al-4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%-75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.

  2. Influence of surface modification on corrosion and biocompatibility of titanium alloys

    NASA Astrophysics Data System (ADS)

    Rahman, Zia Ur

    Titanium alloys are playing a vital role in the field of biomaterials due to their excellent corrosion resistance and biocompatibility. These alloys enhance the quality and longevity of human life by replacing or treating various parts of the body. However, as these materials are in constant contact with the aggressive body fluids, corrosion leads to metal ions dissolution. These ions leach to the adjacent tissues and causes adverse reactions. Surface modifications are used to improve corrosion resistance and biological activity without changing their bulk properties. In this investigation, electropolishing, magnetoelectropolishing, titanium coating and hydroxiapatitecoating were carried out on commercially pure titanium (CPTi), Ti6Al4V and Ti6Al4V-ELI (Extra Low Interstitials). These surface modifications are known to effect surface charge, chemistry, morphology; wettability, corrosion resistance and biocompatibility of these materials. In vitro cyclic potentiodynamic polarization tests were conducted in phosphate buffer saline in compliance with ASTM standard. The surface morphology, roughness and wettability of these alloys were studied using scanning electron microscope, atomic force microscope and contact angle meter, respectively. Moreover, biocompatibility of titanium alloys was assessed by growing MC3T3 pre-osteoblast cells on their surfaces

  3. 55. TOP OF STEEL TOWER WITH ELI WINDMILL LOCATED ABOUT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    55. TOP OF STEEL TOWER WITH ELI WINDMILL LOCATED ABOUT 6-8 MILES SOUTH OF NEBRASKA CITY AT EAST SIDE OF NEBRASKA HIGHWAY 75. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  4. 58. DETAIL OF HEAD OF ELI WINDMILL ON THE GROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    58. DETAIL OF HEAD OF ELI WINDMILL ON THE GROUND AT THE STOLL RESIDENCE, ABOUT 1-1/2 MILES WEST OF NEBRASKA CITY ON STEAM WAGON ROAD. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  5. 53. GENERAL VIEW OF ELI WINDMILL ON STEEL TOWER AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    53. GENERAL VIEW OF ELI WINDMILL ON STEEL TOWER AT GEORGE STUCKENOLZ FARM ABOUT 6 MILES SOUTH OF NEBRASKA CITY WEST OF NEBRASKA HIGHWAY 75. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  6. Surface characterization and biocompatibility of titanium alloys implanted with nitrogen by Hardion+ technology.

    PubMed

    Gordin, D M; Gloriant, T; Chane-Pane, V; Busardo, D; Mitran, V; Höche, D; Vasilescu, C; Drob, S I; Cimpean, A

    2012-12-01

    In this study, the new Hardion+ micro-implanter technology was used to modify surface properties of biomedical pure titanium (CP-Ti) and Ti-6Al-4V ELI alloy by implantation of nitrogen ions. This process is based on the use of an electron cyclotron resonance ion source to produce a multienergetic ion beam from multicharged ions. After implantation, surface analysis methods revealed the formation of titanium nitride (TiN) on the substrate surfaces. An increase in superficial hardness and a significant reduction of friction coefficient were observed for both materials when compared to non-implanted samples. Better corrosion resistance and a significant decrease in ion release rates were observed for N-implanted biomaterials due to the formation of the protective TiN layer on their surfaces. In vitro tests performed on human fetal osteoblasts indicated that the cytocompatibility of N-implanted CP-Ti and Ti-6Al-4V alloy was enhanced in comparison to that of the corresponding non treated samples. Consequently, Hardion+ implantation technique can provide titanium alloys with better qualities in terms of corrosion resistance, cell proliferation, adhesion and viability.

  7. Treating orthopedic prosthesis with diamond-like carbon: minimizing debris in Ti6Al4V.

    PubMed

    Oliveira, Luciane Y S; Kuromoto, Neide K; Siqueira, Carlos J M

    2014-10-01

    Prostheses are subject to various forms of failing mechanisms, including wear from ordinary patient motion. Superficial treatments can improve tribological properties of the contact pair, minimizing wear and increasing prostheses lifetime. One possibility is the diamond-like carbon (DLC) coating, where Carbon is deposited with variable ratio of sp(2)/sp(3) structures, leading to an increase in surface hardness. So in this research Ti6Al4V samples were coated with DLC using sputtering process to evaluate the debris release. The Ti6Al4V and Ti6Al4V plus DLC coating surfaces were analyzed using Raman spectroscopy and instrumented indentation (hardness). The wear behavior was tested using a reciprocating linear tribometer. The wear rate was smaller in the coated samples, producing less debris than the untreated Ti6Al4V alloy. Debris morphology was also evaluated, using scanning electronic microscopy, and it was observed that debris size from the coated samples were bigger than those observed from the uncoated Ti6Al4V alloy, above the size that generally triggers biological response from the host. PMID:24948374

  8. Laser processed TiN reinforced Ti6Al4V composite coatings.

    PubMed

    Balla, Vamsi Krishna; Bhat, Abhimanyu; Bose, Susmita; Bandyopadhyay, Amit

    2012-02-01

    The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-material interactions and tribological performance of TiN particle reinforced Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-material interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10 N normal load. The results show that the composite coatings contain distinct TiN particles embedded in α+β phase matrix. The average top surface hardness of Ti6Al4V alloy increased from 394±8 HV to 1138±61 HV with 40 wt% TiN reinforcement. Among the composite coatings, the coatings reinforced with 40 wt% TiN exhibited the highest wear resistance of 3.74×10(-6) mm(3)/Nm, which is lower than the wear rate, 1.04×10(-5) mm(3)/Nm, of laser processed CoCrMo alloy tested under identical experimental conditions. In vitro biocompatibility study showed that these composite coatings were non-toxic and provides superior cell-material interactions compared to Ti6Al4V control, as a result of their high surface energy. In summary, excellent in vitro wear resistance and biocompatibility of present laser processed TiN reinforced Ti6Al4V alloy composite coatings clearly show their potential as wear resistant contact surfaces for load bearing implant applications.

  9. Laser Processed TiN Reinforced Ti6Al4V Composite Coatings

    PubMed Central

    Balla, Vamsi Krishna; Bhat, Abhimanyu; Bose, Susmita; Bandyopadhyay, Amit

    2011-01-01

    The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-materials interactions and tribological performance of TiN particle reinforced Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-materials interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10N normal load. The results show that the composite coatings contain distinct TiN particles embedded in α + β phase matrix. The average top surface hardness of Ti6Al4V alloy increased from 394 ± 8 HV to 1138 ± 61 HV with 40 wt.% TiN reinforcement. Among the composite coatings, the coatings reinforced with 40 wt. % TiN exhibited the highest wear resistance of 3.74 × 10-6 mm3/Nm, which is lower than the wear rate, 1.04 × 10-5 mm3/Nm, of laser processed CoCrMo alloy tested under identical experimental conditions. In vitro biocompatibility study showed that these composite coatings were non-toxic and provides superior cell-material interactions compared to Ti6Al4V control, as a result of their high surface energy. In summary, excellent in vitro wear resistance and biocompatibility of present laser processed TiN reinforced Ti6Al4V alloy composite coatings clearly show their potential as wear resistant contact surfaces for load bearing implant applications. PMID:22301169

  10. Bacterial adherence to anodized titanium alloy

    NASA Astrophysics Data System (ADS)

    Pérez-Jorge Peremarch, C.; Pérez Tanoira, R.; Arenas, M. A.; Matykina, E.; Conde, A.; De Damborenea, J. J.; Gómez Barrena, E.; Esteban, J.

    2010-11-01

    The aim of this study was to evaluate Staphylococcus sp adhesion to modified surfaces of anodized titanium alloy (Ti-6Al-4V). Surface modification involved generation of fluoride-containing titanium oxide nanotube films. Specimens of Ti-6Al-4V alloy 6-4 ELI-grade 23- meets the requirements of ASTM F136 2002A (AMS 2631B class A1) were anodized in a mixture of sulphuric/hydrofluoric acid at 20 V for 5 and 60 min to form a 100 nm-thick porous film of 20 nm pore diameter and 230 nm-thick nanotube films of 100 nm in diameter. The amount of fluorine in the oxide films was of 6% and of 4%, respectively. Collection strains and six clinical strains each of Staphylococcus aureus and Staphylococcus epidermidis were studied. The adherence study was performed using a previously published protocol by Kinnari et al. The experiments were performed in triplicates. As a result, lower adherence was detected for collection strains in modified materials than in unmodified controls. Differences between clinical strains were detected for both species (p<0.0001, Kruskal-Wallis test), although global data showed similar results to that of collection strains (p<0.0001, Kruskal-Wallis test). Adherence of bacteria to modified surfaces was decreased for both species. The results also reflect a difference in the adherence between S. aureus and S. epidermidis to the modified material. As a conclusion, not only we were able to confirm the decrease of adherence in the modified surface, but also the need to test multiple clinical strains to obtain more realistic microbiological results due to intraspecies differences.

  11. Investigation of Ti6Al4V Orthogonal Cutting Numerical Simulations using Different Material Models

    SciTech Connect

    Alvarez, Roberto

    2010-06-15

    Titanium alloys are materials considered as extremely difficult to cut and titanium alloy Ti6Al4V is a reference in machining of titanium. The segmented (saw toothed) chip morphology has attracted great interest in researchers because the understanding of the saw-toothed chip morphology helps to understand the chip formation mechanisms. In this study, the effect of different constitutive models on the saw-toothed chip morphology is examined in machining Ti6Al4V. The paper presents the influence of eight material constitutive modelling in the simulation of segmented chip formation. A critical comparison of outstanding process outputs as cutting force, temperature and measurable parameters for segmented chips is carried out to compare and discuss the performance of the eight different material models to each other and with experimental data.

  12. Electrochemical & osteoblast adhesion study of engineered TiO2 nanotubular surfaces on titanium alloys.

    PubMed

    Rahman, Zia Ur; Haider, Waseem; Pompa, Luis; Deen, K M

    2016-01-01

    TiO2 nanotubes were grafted on the surface of cpTi, Ti6Al4V and Ti6Al4V-ELI with the aim to provide a new podium for human pre-osteoblast cell (MC3T3) adhesion and proliferation. The surface morphology and chemistry of these alloys were examined with scanning electron microscopy and energy dispersive x-ray spectroscopy. TiO2 nanotubes were further characterized by cyclic potentiodynamic polarization tests and electrochemical impedance spectroscopy. The vertically aligned nanotubes were subjected to pre-osteoblast cell proliferation in order to better understand cell-material interaction. The study demonstrated that these cells interact differently with nanotubes of different titanium alloys. The significant acceleration in the growth rate of pre-osteoblast cell adhesion and proliferation is also witnessed. Additionally, the cytotoxicity of the leached metal ions was evaluated by using a tetrazolium-based bio-assay, MTS. Each group of data was operated for p<0.05, concluded one way ANOVA to investigate the significance difference.

  13. Alloy

    NASA Astrophysics Data System (ADS)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  14. Assessing Eli Broad's Assault on Public School System Leadership

    ERIC Educational Resources Information Center

    English, Fenwick W.; Crowder, Zan

    2012-01-01

    Eli Broad's approach to reforming urban public education does not recognize his own self-interest in promoting changes within such educational systems, a classic problem of misrecognition. The Broad agenda is an assault on the notion of the mission of public education as a service instead of a for-profit enterprise concerned with making money for…

  15. 52. GENERAL VIEW OF ELI WINDMILL ON STEEL TOWER IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. GENERAL VIEW OF ELI WINDMILL ON STEEL TOWER IN PASTURE LOCATED ABOUT 6-8 MILES SOUTH OF NEBRASKA CITY ABOUT ONE 1 MILE WEST OF NEBRASKA HIGHWAY 75. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  16. 57. DETAIL OF HEAD AND WHEEL OF ELI WINDMILL ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    57. DETAIL OF HEAD AND WHEEL OF ELI WINDMILL ON THE GROUND AT THE STOLL RESIDENCE, ABOUT 1-1/2 MILES WEST OF NEBRASKA CITY ON STEAM WAGON ROAD. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  17. 62. GENERAL VIEW OF ELI WINDMILL AND STEEL TOWER ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. GENERAL VIEW OF ELI WINDMILL AND STEEL TOWER ON THE GROUND AT THE STOLL RESIDENCE ABOUT 1-1/2 MILES WEST OF NEBRASKA CITY ON STEAM WAGON ROAD. - Kregel Windmill Company Factory, 1416 Central Avenue, Nebraska City, Otoe County, NE

  18. Gamma beam industrial applications at ELI-NP

    NASA Astrophysics Data System (ADS)

    Suliman, Gabriel; Iancu, Violeta; Ur, Calin A.; Iovea, Mihai; Daito, Izuru; Ohgaki, Hideaki

    2016-09-01

    The Nuclear Physics oriented pillar of the pan-European Extreme Light Infrastructure (ELI-NP) will host an ultra-bright, energy tunable, and quasi-monochromatic gamma-ray beam system in the range of 0.2-19.5 MeV produced by laser Compton backscattering. This gamma beam satisfies the criteria for large-size product investigations with added capabilities like isotope detection through the use of nuclear resonance fluorescence (NRF) and is ideal for non-destructive testing applications. Two major applications of gamma beams are being envisaged at ELI-NP: industrial applications based on NRF and industrial radiography and tomography. Both applications exploit the unique characteristics of the gamma beam to deliver new opportunities for the industry. Here, we present the experimental setups proposed at ELI-NP and discuss their performance based on analytical calculations and GEANT4 numerical simulations. One of the main advantages of using the gamma beam at ELI-NP for applications based on NRF is the availability of an advanced detector array, which can enhance the advantages already provided by the high quality of the gamma beam.

  19. Improving the osteointegration of Ti6Al4V by zeolite MFI coating.

    PubMed

    Li, Yong; Jiao, Yilai; Li, Xiaokang; Guo, Zheng

    2015-05-01

    Osteointegration is crucial for success in orthopedic implantation. In recent decades, there have been numerous studies aiming to modify titanium alloys, which are the most widely used materials in orthopedics. Zeolites are solid aluminosilicates whose application in the biomedical field has recently been explored. To this end, MFI zeolites have been developed as titanium alloy coatings and tested in vitro. Nevertheless, the effect of the MFI coating of biomaterials in vivo has not yet been addressed. The aim of the present work is to evaluate the effects of MFI-coated Ti6Al4V implants in vitro and in vivo. After surface modification, the surface was investigated using field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). No difference was observed regarding the proliferation of MC3T3-E1 cells on the Ti6Al4V (Ti) and MFI-coated Ti6Al4V (M-Ti) (p > 0.05). However, the attachment of MC3T3-E1 cells was found to be better in the M-Ti group. Additionally, ALP staining and activity assays and quantitative real-time RT-PCR indicated that MC3T3-E1 cells grown on the M-Ti displayed high levels of osteogenic differentiation markers. Moreover, Van-Gieson staining of histological sections demonstrated that the MFI coating on Ti6Al4V scaffolds significantly enhanced osteointegration and promoted bone regeneration after implantation in rabbit femoral condylar defects at 4 and 12 weeks. Therefore, this study provides a method for modifying Ti6Al4V to achieve improved osteointegration and osteogenesis.

  20. Development of a versatile procedure for the biofunctionalization of Ti-6Al-4V implants

    NASA Astrophysics Data System (ADS)

    Rezvanian, Parsa; Arroyo-Hernández, María; Ramos, Milagros; Daza, Rafael; Elices, Manuel; Guinea, Gustavo V.; Pérez-Rigueiro, José

    2016-11-01

    Titanium (Ti) and titanium alloys are among the most-commonly used metallic materials for implantation in the human body for the purpose of replacing hard tissue. Although Ti and its alloys are widely used for such an aim, in implants of a long duration they exhibit some shortcomings due to the loosening of the very implant. This phenomenon is highly dependent on the interaction between the organic tissues and the surface of the implant. In this study, the authors introduce a surface treatment technique for functionalization of the surface of Ti-6Al-4V alloy with amino groups that could help to control this interaction. The functionalized layer was deposited by activated vapor silanization (AVS), which has been proven as a reliable and robust technique with other materials. The resulting biofunctional layers were characterized by atomic force microscopy and fluorescence microscopy, with the optimal conditions for the deposition of a homogeneous film with a high density of amino groups being determined. Additionally, the non-toxic nature and stability of the biofunctional layer were confirmed by cell culturing. The results show the formation of a homogeneous biofunctional amine layer on Ti-6Al-4V alloy that may be used as a platform for the subsequent covalent immobilization of proteins or other biomolecules.

  1. Nitric acid passivation of Ti6Al4V reduces thickness of surface oxide layer and increases trace element release.

    PubMed

    Callen, B W; Lowenberg, B F; Lugowski, S; Sodhi, R N; Davies, J E

    1995-03-01

    Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices. PMID:7615579

  2. Microstructure and Properties of the Ti6Al4V/Inconel 625 Bimetal Obtained by Explosive Joining

    NASA Astrophysics Data System (ADS)

    Topolski, Krzysztof; Szulc, Zygmunt; Garbacz, Halina

    2016-08-01

    The study is concerned with the bimetallic plate composed of the Ti6Al4V and Inconel 625 alloys. The alloys were joined together using the explosive method with the aim to produce a bimetallic joint. The structure and the mechanical properties of the as-received raw Ti6Al4V and Inconel 625 alloys, the Ti6Al4V/Inconel 625 joint, and the joint after annealing (600 °C for 1 h) were examined. The samples observations were performed using a light microscope and a scanning electron microscope. The mechanical properties were estimated by microhardness measurements, tensile tests, and three-point bending tests. Moreover, the deformation strengthening of the metals and the strength of the joint were analyzed. The explosive process resulted in a good quality bimetallic joint. Both sheets were deformed plastically and the joint surface between the alloys had a wavy shape. In the area of the joint surface, the hardness was increased. For example, the annealing at 600 °C for 1 h resulted in changes of the microhardness in the entire volume of the samples and in changes of the morphology of the joint surface. In three-point bending tests, the samples were examined in two opposite positions (Ti6Al4V on the top or Inconel 625 on the top). The results indicated to depend on the position in which the sample was tested.

  3. Microstructure and Properties of the Ti6Al4V/Inconel 625 Bimetal Obtained by Explosive Joining

    NASA Astrophysics Data System (ADS)

    Topolski, Krzysztof; Szulc, Zygmunt; Garbacz, Halina

    2016-04-01

    The study is concerned with the bimetallic plate composed of the Ti6Al4V and Inconel 625 alloys. The alloys were joined together using the explosive method with the aim to produce a bimetallic joint. The structure and the mechanical properties of the as-received raw Ti6Al4V and Inconel 625 alloys, the Ti6Al4V/Inconel 625 joint, and the joint after annealing (600 °C for 1 h) were examined. The samples observations were performed using a light microscope and a scanning electron microscope. The mechanical properties were estimated by microhardness measurements, tensile tests, and three-point bending tests. Moreover, the deformation strengthening of the metals and the strength of the joint were analyzed. The explosive process resulted in a good quality bimetallic joint. Both sheets were deformed plastically and the joint surface between the alloys had a wavy shape. In the area of the joint surface, the hardness was increased. For example, the annealing at 600 °C for 1 h resulted in changes of the microhardness in the entire volume of the samples and in changes of the morphology of the joint surface. In three-point bending tests, the samples were examined in two opposite positions (Ti6Al4V on the top or Inconel 625 on the top). The results indicated to depend on the position in which the sample was tested.

  4. Influence of Porosity on Mechanical Properties and In vivo Response of Ti6Al4V Implants

    PubMed Central

    Bandyopadhyay, Amit; Espana, Felix; Balla, Vamsi Krishna; Bose, Susmita; Ohgami, Yusuke; Davies, Neal M

    2009-01-01

    Metallic biomaterials are widely used to restore the lost structure and functions of human bone. Due to the large number of joint replacements, there is a growing demand for new and improved orthopedic implants. More specifically, there is a need for novel load bearing metallic implants with low effective modulus matching to that of bone in order to reduce stress shielding and consequent increase in the in vivo life-span of the implant. In this study, we have fabricated porous Ti6Al4V alloy structures, using Laser Engineered Net Shaping (LENS™) to demonstrate that advanced manufacturing techniques such as LENS™ can be used to fabricate low-modulus, tailored porosity implants with a wide variety of metals/alloys, where the porosity can be designed in areas based on the patient's need to enhance biological fixation and achieve long-term in vivo stability. The effective modulus of Ti6Al4V alloy structures has been tailored between 7 and 60 GPa and porous Ti alloy structures containing 23 to 32 vol. % porosity showed modulus equivalent to human cortical bone. In vivo behavior of porous Ti6Al4V alloy samples in male Sprague-Dawley rats for 16 weeks demonstrated significant increase in calcium within the implants indicating excellent biological tissue ingrowth through interconnected porosity. In vivo results also showed that total amount of porosity plays an important role in tissue ingrowth. PMID:19913643

  5. Structural, mechanical and in vitro characterization of individually structured Ti-6Al-4V produced by direct laser forming.

    PubMed

    Hollander, Dirk A; von Walter, Matthias; Wirtz, Tobias; Sellei, Richard; Schmidt-Rohlfing, Bernhard; Paar, Othmar; Erli, Hans-Josef

    2006-03-01

    Direct laser forming (DLF) is a rapid prototyping technique which enables prompt modelling of metal parts with high bulk density on the base of individual three-dimensional data, including computer tomography models of anatomical structures. In our project, we tested DLF-produced material on the basis of the titanium alloy Ti-6Al-4V for its applicability as hard tissue biomaterial. To this end, we investigated mechanical and structural properties of DLF-Ti-6Al-4V. While the tensile and yield strengths of untreated DLF alloy ranged beyond 1000 MPa, a breaking elongation of 6.5+/-0.6% was determined for this material. After an additional post-DLF annealing treatment, this parameter was increased two-fold to 13.0+/-0.6%, while tensile and yield strengths were reduced by approx. 8%. A Young's modulus of 118.000+/-2.300 MPa was determined for post-DLF annealed Ti-6Al-4V. All data gained from tensile testing of post-DLF annealed Ti-6Al-4V matched American Society of Testing and Materials (ASTM) specifications for the usage of this alloy as medical material. Rotating bending tests revealed that the fatigue profile of post-DLF annealed Ti-6Al-4V was comparable to casted/hot isostatic pressed alloy. We characterized the structure of non-finished DLF-Ti-6Al-4V by scanning electron microscopy and observed a surface-associated layer of particles, which was removable by sandblasting as a finishing step. We manufactured porous specimens with nominal pore diameters of 500, 700 and 1000 microm. The diameters were reduced by the used DLF processing by approx. 300 microm. In an in vitro investigation, we cultured human osteoblasts on non-porous and porous blasted DLF-Ti-6Al-4V specimens to study morphology, vitality, proliferation and differentiation of the cells. The cells spreaded and proliferated on DLF-Ti-6Al-4V over a culture time of 14 days. On porous specimens, osteoblasts grew along the rims of the pores and formed circle-shaped structures, as visualized by live

  6. Comparison of bio-mineralization behavior of Ti-6Al-4V-1Nb and Zr-1Nb nano-tubes formed by anodization

    NASA Astrophysics Data System (ADS)

    Choi, Yong; Hong, Sun I.

    2014-12-01

    Nano-tubes of titanium and zirconium alloys like Ti-6Al-4V-1Nb and Zr-1Nb were prepared by anodization followed by coating with hydroxylapatite (HA) and their bio-mineralization behaviors were compared to develop a bio-compatible material for implants in orthopedics, dentistry and cardiology. Ti-6Al-4V-1Nb weight gain in a simulated body solution increased gradually. The bigger tube diameter was, the heavier HA was deposited. Surface roughness of both alloys increased highly with the increasing diameter of nano-tube. Their surface roughness decreased by HA deposition due to the removal of the empty space of the nano-tubes. Zr-1Nb alloy had faster growth of nano-tubes layers more than Ti-6Al-4V-1Nb alloy.

  7. Patients' satisfaction evaluation with the health center of elis province.

    PubMed

    Karavida, Angeliki; Stamouli, Maria-Aggeliki; Balis, Charalampos

    2014-01-01

    Patient satisfaction related to the provided health services is a key indicator of the quality of the health sector. The SERVQUAL model was employed as a way of measuring the level of patient satisfaction with the services of the Health Center of Elis Province. Although certain aspects such as "Assurance" and "Empathy" meet the users' needs, improvements like a detailed medical record and an overhaul of the equipment need to be introduced. PMID:25000072

  8. Patients' satisfaction evaluation with the health center of elis province.

    PubMed

    Karavida, Angeliki; Stamouli, Maria-Aggeliki; Balis, Charalampos

    2014-01-01

    Patient satisfaction related to the provided health services is a key indicator of the quality of the health sector. The SERVQUAL model was employed as a way of measuring the level of patient satisfaction with the services of the Health Center of Elis Province. Although certain aspects such as "Assurance" and "Empathy" meet the users' needs, improvements like a detailed medical record and an overhaul of the equipment need to be introduced.

  9. Extreme Light Infrastructure - Nuclear Physics Eli-Np Project

    NASA Astrophysics Data System (ADS)

    Gales, S.

    2015-06-01

    The development of high power lasers and the combination of such novel devices with accelerator technology has enlarged the science reach of many research fields, in particular High energy, Nuclear and Astrophysics as well as societal applications in Material Science, Nuclear Energy and Medicine. The European Strategic Forum for Research Infrastructures (ESFRI) has selected a proposal based on these new premises called "ELI" for Extreme Light Infrastructure. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW class lasers and a Back Compton Scattering High Brilliance and Intense Low Energy Gamma Beam , a marriage of Laser and Accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

  10. Subcritical crack growth of Ti-6Al-4V at room temperature under high stress-ratio loading

    SciTech Connect

    Thomas, J.P.

    1998-11-13

    Ti-6Al-4V is a two phase {alpha}-{beta} titanium alloy commonly used for turbine fan and compressor components. The crack growth behavior of Ti-6Al-4V and the role played by various material, mechanical, and environmental factors has been thoroughly investigated. This alloy is also susceptible to crack growth under sustained loading in air (SLC), and both hydrogen assisted cracking and low temperature creep mechanisms have been used to explain this susceptibility. Very little information is available on high R-ratio fatigue crack growth of Ti-6Al-4V and the role played by SLC on the fatigue process. In order to gain better understanding of the cracking behavior of this alloy under ripple loading conditions, room temperature, high stress-ratio (R {ge} 0.9) fatigue and SLC experiments have been conducted on a Ti-6Al-4V plate forging material in the duplex-annealed (DA) condition. The results of this investigation,namely, fatigue crack growth rates (CGR) as a function of stress intensity; SLC data; and scanning electron microscopy of the fatigue and SLC fracture surfaces are reported below.

  11. Improving the osteointegration of Ti6Al4V by zeolite MFI coating

    SciTech Connect

    Li, Yong; Jiao, Yilai; Li, Xiaokang; Guo, Zheng

    2015-05-01

    Osteointegration is crucial for success in orthopedic implantation. In recent decades, there have been numerous studies aiming to modify titanium alloys, which are the most widely used materials in orthopedics. Zeolites are solid aluminosilicates whose application in the biomedical field has recently been explored. To this end, MFI zeolites have been developed as titanium alloy coatings and tested in vitro. Nevertheless, the effect of the MFI coating of biomaterials in vivo has not yet been addressed. The aim of the present work is to evaluate the effects of MFI-coated Ti6Al4V implants in vitro and in vivo. After surface modification, the surface was investigated using field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). No difference was observed regarding the proliferation of MC3T3-E1 cells on the Ti6Al4V (Ti) and MFI-coated Ti6Al4V (M−Ti) (p > 0.05). However, the attachment of MC3T3-E1 cells was found to be better in the M−Ti group. Additionally, ALP staining and activity assays and quantitative real-time RT-PCR indicated that MC3T3-E1 cells grown on the M−Ti displayed high levels of osteogenic differentiation markers. Moreover, Van-Gieson staining of histological sections demonstrated that the MFI coating on Ti6Al4V scaffolds significantly enhanced osteointegration and promoted bone regeneration after implantation in rabbit femoral condylar defects at 4 and 12 weeks. Therefore, this study provides a method for modifying Ti6Al4V to achieve improved osteointegration and osteogenesis. - Highlights: • Osteointegration is a crucial factor for orthopedic implants. • We coated MFI zeolite on Ti6Al4V substrates and investigated the effects in vitro and in vivo. • The MFI coating displayed good biocompatibility and promoted osteogenic differentiation in vitro. • The MFI coating promoted osteointegration and osteogenesis peri-implant in vivo.

  12. High-Temperature Galling Characteristics of Ti-6Al-4V with and without Surface Treatments

    SciTech Connect

    Blau, Peter Julian; ERDMAN III, DONALD L; Ohriner, Evan Keith; Jolly, Brian C

    2011-01-01

    Galling is a severe form of surface damage in metals and alloys that typically arises under relatively high normal force, low-sliding speed, and in the absence of effective lubrication. It can lead to macroscopic surface roughening and seizure. The occurrence of galling can be especially problematic in high-temperature applications like diesel engine exhaust gas recirculation system components and adjustable turbocharger vanes, because suitable lubricants may not be available, moisture desorption promotes increased adhesion, and the yield strength of metals decreases with temperature. Oxidation can counteract these effects to some extent by forming lubricative oxide films. Two methods to improve the galling resistance of titanium alloy Ti-6Al-4V were investigated: (a) applying an oxygen diffusion treatment, and (b) creating a metal-matrix composite with TiB2 using a high-intensity infrared heating source. A new, oscillating three-pin-on-flat, high-temperature test method was developed and used to characterize galling behavior relative to a cobalt-based alloy (Stellite 6B ). The magnitude of the oscillating torque, the surface roughness, and observations of surface damage were used as measures of galling resistance. Owing to the formation of lubricative oxide films, the galling resistance of the Ti-alloy at 485o C, even non-treated, was considerably better than it was at room temperature. The IR-formed composite displayed reduced surface damage and lower torque than the substrate titanium alloy.

  13. Procedures for determining MATMOD-4V material constants

    SciTech Connect

    Lowe, T.C.

    1993-11-01

    The MATMOD-4V constitutive relations were developed from the original MATMOD model to extend the range of nonelastic deformation behaviors represented to include transient phenomena such as strain softening. Improvements in MATMOD-4V increased the number of independent material constants and the difficulty in determining their values. Though the constitutive relations are conceptually simple, their form and procedures for obtaining their constants can be complex. This paper reviews in detail the experiments, numerical procedures, and assumptions that have been used to determine a complete set of MATMOD-4V constants for high purity aluminum.

  14. Producing Ti-6Al-4V plate from single-melt EBCHM ingot

    NASA Astrophysics Data System (ADS)

    Wood, J. R.

    2002-02-01

    The study reviewed in this paper was initiated to produce low-cost, aerospace-quality Ti-6Al-4V alloy plate directly from single melt, electron beam cold hearth melted slab ingots. This study is one of the programs of the Metals Affordability Initiative Consortium under the direction of the U.S. Air Force Research Laboratory’s Materials and Manufacturing Directorate. The main objective of this program is to achieve significant cost savings for titanium plate production while accelerating the implementation time. This article discusses the progress to date in this multi-year program.

  15. An Experimental and Theoretical Study of Ti-6Al-4V to Multi-mbar Pressures

    SciTech Connect

    MacLeod, S G; Tegner, B E; Cynn, H; Evans, W J; Proctor, J; McMahon, M I; Ackland, G J

    2012-03-14

    We report results from an experimental and theoretical study of the ternary alloy Ti-6Al-4V to 221 GPa. We observe a phase transition to the hexagonal {omega}-phase at approximately 30 GPa, and then a further transition to the cubic {beta}-phase starting at 94-99 GPa. We do not observe the orthorhombic {gamma} and {delta} phases reported previously in pure Ti. Computational studies show that this sequence is possible only if there is significant local atomic ordering during the compression process, yet insufficient atomic diffusion to reach the phase separated thermodynamic equilibrium state.

  16. Combination of laser keyhole and conduction welding: Dissimilar laser welding of niobium and Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Torkamany, M. J.; Malek Ghaini, F.; Poursalehi, R.; Kaplan, A. F. H.

    2016-04-01

    Pulsed Nd:YAG laser welding of pure niobium plate to titanium alloy Ti-6Al-4V sheet in butt joint is studied regarding the laser/metal interaction modes. To obtain the optimized process parameters in dissimilar welding of Ti-6Al-4V/Nb, the melting ratio of laser beam energy for each weld counterpart is evaluated experimentally. Different laser welding modes of keyhole and conduction are predicted regarding the absorbed energy from the similar laser pulses on each weld counterpart. Laser keyhole and conduction welding were observed simultaneously through direct visualization of laser interaction with dissimilar metals using High Speed Imaging (HSI) system.

  17. Microwave-assisted fabrication of strontium doped apatite coating on Ti6Al4V.

    PubMed

    Zhou, Huan; Kong, Shiqin; Pan, Yan; Zhang, Zhiguo; Deng, Linhong

    2015-11-01

    Strontium has been shown to be a beneficial dopant to calcium phosphates when incorporated at nontoxic level. In the present work we studied the possibility of solution derived doping strontium into calcium phosphate coatings on titanium alloy Ti6Al4V based implants by a recently reported microwave-assisted method. By using this method strontium doped calcium phosphate nuclei were deposited to pretreated titanium alloy surface dot by dot to compose a crack-free coating layer. The presence of strontium in solution led to reduced roughness of the coating and finer nucleus size formed. In vitro study found that proliferation and differentiation of osteoblast cells seeded on the coating were influenced by strontium content in coatings, showing an increasing followed by a decreasing behavior with increasing substitution of calcium by strontium. It is suggested that this new microwave-assisted strontium doped calcium phosphate coatings may have great potential in implant modification.

  18. Spallation in Ti-6Al-4V: Stress Measurements and Recovery

    SciTech Connect

    Tyler, C.; Bourne, N. K.; Millett, J. C. F.

    2006-07-28

    Previous work by a number of authors has shown that the spall strength of the engineering alloy, Ti 6Al - 4V increases markedly with pulse duration. In this paper, we have reproduced those results in a low oxygen variant of the alloy, over a range of impact stresses. The microstructure consisted of a mixture of primary {alpha} grains in a matrix of transformed {beta}. Samples have also been shock loaded and recovered under conditions of one-dimensional strain, to compliment the results of the stress gauge experiments. In all the recovered samples, complete spallation occurred, but examination of damage at secondary sites showed that this occurred via nucleation and growth of pores. Ductile failure appears to be a mixture of void formation and coalescence within primary {alpha} grains and along primary {alpha} / transformed {beta} boundaries.

  19. Specific heat treatment of selective laser melted Ti-6Al-4V for biomedical applications

    NASA Astrophysics Data System (ADS)

    Huang, Qianli; Liu, Xujie; Yang, Xing; Zhang, Ranran; Shen, Zhijian; Feng, Qingling

    2015-12-01

    The ductility of as-fabricated Ti-6Al-4V falls far short of the requirements for biomedical titanium alloy implants and the heat treatment remains the only applicable option for improvement of their mechanical properties. In the present study, the decomposition of as-fabricated martensite was investigated to provide a general understanding on the kinetics of its phase transformation. The decomposition of asfabricated martensite was found to be slower than that of water-quenched martensite. It indicates that specific heat treatment strategy is needed to be explored for as-fabricated Ti-6Al-4V. Three strategies of heat treatment were proposed based on different phase transformation mechanisms and classified as subtransus treatment, supersolvus treatment and mixed treatment. These specific heat treatments were conducted on selective laser melted samples to investigate the evolutions of microstructure and mechanical properties. The subtransus treatment leaded to a basket-weave structure without changing the morphology of columnar prior β grains. The supersolvus treatment resulted in a lamellar structure and equiaxed β grains. The mixed treatment yielded a microstructure that combines both features of the subtransus treatment and supersolvus treatment. The subtransus treatment is found to be the best choice among these three strategies for as-fabricated Ti-6Al-4V to be used as biomedical implants.

  20. ELIMED, MEDical and multidisciplinary applications at ELI-Beamlines

    NASA Astrophysics Data System (ADS)

    Schillaci, F.; Anzalone, A.; Cirrone, G. A. P.; Carpinelli, M.; Cuttone, G.; Cutroneo, M.; De Martinis, C.; Giove, D.; Korn, G.; Maggiore, M.; Manti, L.; Margarone, D.; Musumarra, A.; Perozziello, F. M.; Petrovic, I.; Pisciotta, P.; Renis, M.; Ristic-Fira, A.; Romano, F.; Romano, F. P.; Schettino, G.; Scuderi, V.; Torrisi, L.; Tramontana, A.; Tudisco, S.

    2014-04-01

    ELI-Beamlines is one of the pillars of the pan-European project ELI (Extreme Light Infrastructure). It will be an ultra high-intensity, high repetition-rate, femtosecond laser facility whose main goal is generation and applications of high-brightness X-ray sources and accelerated charged particles in different fields. Particular care will be devoted to the potential applicability of laser-driven ion beams for medical treatments of tumors. Indeed, such kind of beams show very interesting peculiarities and, moreover, laser-driven based accelerators can really represent a competitive alternative to conventional machines since they are expected to be more compact in size and less expensive. The ELIMED project was launched thanks to a collaboration established between FZU-ASCR (ELI-Beamlines) and INFN-LNS researchers. Several European institutes have already shown a great interest in the project aiming to explore the possibility to use laser-driven ion (mostly proton) beams for several applications with a particular regard for medical ones. To reach the project goal several tasks need to be fulfilled, starting from the optimization of laser-target interaction to dosimetric studies at the irradiation point at the end of a proper designed transport beam-line. Researchers from LNS have already developed and successfully tested a high-dispersive power Thomson Parabola Spectrometer, which is the first prototype of a more performing device to be used within the ELIMED project. Also a Magnetic Selection System able to produce a small pencil beam out of a wide energy distribution of ions produced in laser-target interaction has been realized and some preliminary work for its testing and characterization is in progress. In this contribution the status of the project will be reported together with a short description of the of the features of device recently developed.

  1. Collagen type I-coating of Ti6Al4V promotes adhesion of osteoblasts.

    PubMed

    Geissler, U; Hempel, U; Wolf, C; Scharnweber, D; Worch, H; Wenzel, K

    2000-09-15

    The initial contact of osteoblasts with implant surfaces is an important event for osseointegration of implants. Osseointegration of Ti6Al4V may be improved by precoating of its surface with collagen type I. In this study, the adhesion of rat calvarial osteoblasts to uncoated and collagen type I-coated titanium alloy was investigated over a period of 24 h. Collagen type I-coating accelerates initial adhesion of osteoblasts in the presence of fetal calf serum. One hour after plating, no differences in the percentage of adherent cells between the surfaces investigated were found. Adhesion of osteoblasts to uncoated surfaces was reduced by the GRGDSP peptide by about 70%, whereas adhesion to collagen type I-coated surfaces remained unaffected by treatment of the cells with the peptide. Cell adhesion to coated materials was reduced by about 80% by anti-integrin beta1 antibody. The integrin beta1 antibody did not influence the adhesion to uncoated titanium alloy. The results suggest that osteoblasts adhere to collagen type I-coated materials via integrin beta1 but not by interacting with RGD peptides, whereas adhesion to uncoated titanium alloy is mediated by RGD sequences but not via integrin beta1. Fibronectin does not seem to be involved in the adhesion of osteoblasts to either coated or uncoated titanium alloy. PMID:10880125

  2. Corrosion Resistance and Color Properties of Anodized Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Karambakhsh, Ali; Afshar, Abdollah; Malekinejad, Pejman

    2012-01-01

    In this research, color anodizing of Ti-6Al-4V alloy was performed in phosphoric acid solution of 0.4 M concentration and within 30 s in different voltages (10-120 V) of a DC power supply. The effect of anodizing voltages on the color and thickness of anodized layers on Ti-6Al-4V alloy surface was surveyed. Thickness and refractive index of layers were measured by spectrophotometery and reflectance curves. According to the results, thickness of layers increased with increasing anodizing voltage and was in the range of 38-167 nm. Also the refractive index of anodic film was approximately constant at about 2 and increased inconsiderably with increasing anodizing voltage. Corrosion resistance of the anodized samples in 20 and 50 V was surveyed in physiological solutions of Ringer's solution, Artificial Saliva solution, and Ringer's + 150 mM H2O2 solution at the temperature of 37 °C by potentiodynamic polarization method. The anodized sample in 50 V indicated lower corrosion rate than the non-anodized sample as well as the sample which was anodized in 20 V in all solutions. The non-anodized sample indicated the highest corrosion rate of about 0.25 μA cm-2.

  3. Effect of hydroxyapatite thickness on metal ion release from Ti6Al4V substrates.

    PubMed

    Sousa, S R; Barbosa, M A

    1996-02-01

    The electrochemical dissolution behaviour of Ti6Al4V alloy coated with hydroxyapatite (HA) by plasma spraying was studied in Hank's balanced salt solution (HBSS) and compared with that of polished and grit-blasted passivated surfaces. Two different nominal thicknesses of HA (50 and 200 micro m) were used. Taking a polished passivated surface as reference, grit blasting of the substrate increased the electrical charge used in the oxidation of Ti6Al4V alloy at constant potential, as a result of increased surface area. However, only HA coatings with a thickness of 200 micro m were capable of reducing the charge to values lower than those measured for polished surfaces. Electrochemical impedance spectroscopy has also shown that only 200 micro m thick coatings are effective in reducing the oxidation rate of the substrate. Furthermore, in potentiostatic experiments the 50 micro m thick coating detached from the substrate, which did not occur with the 200 micro m thick coating. However, after 6 months immersion in HBSS, detachment occurred in some regions of both coatings. No titanium, aluminium or vanadium were detected in solution by electrothermal atomic absorption spectroscopy. These data indicate that HA is an effective barrier to metal ion release, even for the thinner coatings, due to formation of metal phosphates or to incorporation of metal ions in the HA structure. PMID:8938233

  4. Simulation of photofission experiments at the ELI-NP facility

    NASA Astrophysics Data System (ADS)

    Constantin, P.; Balabanski, D. L.; Cuong, P. V.

    2016-04-01

    An extensive experimental program for the study of photofission will take place at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility, where different actinide targets will be exposed to a brilliant gamma beam to produce fission fragments. We report on the implementation within the Geant4 simulation toolkit of the photofission process, of related background processes, and of extended ionic charge parameterization. These developments are used to evaluate the production rates of photofission fragments and their release efficiency from the actinide targets.

  5. An experimental study of the (Ti-6Al-4V)-xH phase diagram using in situ synchrotron XRD and TGA/DSC techniques.

    SciTech Connect

    Sun, Pei; Fang, Z. Zak; Koopman, Mark; Paramore, James D.; Chandran, K. S. Ravi; Ren, Yang; Lu, Jun

    2015-02-01

    Hydrogen has been investigated for decades as a temporary alloying element to refine the microstructure of Ti-6Al-4V, and is now being used in a novel powder metallurgy method known as "hydrogen sintering and phase transformation". Pseudo-binary phase diagrams of (Ti-6Al-4V)-xH have been studied and developed, but are not well established due to methodological limitations. In this paper, in situ studies of phase transformations during hydrogenation and dehydrogenation of (Ti-6Al-4V)-xH alloys were conducted using high-energy synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The eutectoid phase transformation of β ↔ α + δ was observed in the (Ti-6Al-4V)-xH alloy via in situ synchrotron XRD at 211 °C with a hydrogen concentration of 37.5 at.% (measured using TGA-DSC). The relationships of hydrogen composition to partial pressure and temperature were investigated in the temperature range 450-900°C. Based on these results, a partial pseudo-binary phase diagram of (Ti-6Al-4V)-xH is proposed for hydrogen compositions up to 60 at.% in the temperature range 100-900°C. Using the data collected in real time under controlled parameters of temperature, composition and hydrogen partial pressure, this work characterizes relevant phase transformations and microstructural evolution for practical titanium-hydrogen technologies of Ti-6Al-4V.

  6. Influence of the processing route of porcelain/Ti-6Al-4V interfaces on shear bond strength.

    PubMed

    Toptan, Fatih; Alves, Alexandra C; Henriques, Bruno; Souza, Júlio C M; Coelho, Rui; Silva, Filipe S; Rocha, Luís A; Ariza, Edith

    2013-04-01

    This study aims at evaluating the two-fold effect of initial surface conditions and dental porcelain-to-Ti-6Al-4V alloy joining processing route on the shear bond strength. Porcelain-to-Ti-6Al-4V samples were processed by conventional furnace firing (porcelain-fused-to-metal) and hot pressing. Prior to the processing, Ti-6Al-4V cylinders were prepared by three different surface treatments: polishing, alumina or silica blasting. Within the firing process, polished and alumina blasted samples were subjected to two different cooling rates: air cooling and a slower cooling rate (65°C/min). Metal/porcelain bond strength was evaluated by shear bond test. The data were analyzed using one-way ANOVA followed by Tuckey's test (p<0.05). Before and after shear bond tests, metallic surfaces and metal/ceramic interfaces were examined by Field Emission Gun Scanning Electron Microscope (FEG-SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS). Shear bond strength values of the porcelain-to-Ti-6Al-4V alloy interfaces ranged from 27.1±8.9MPa for porcelain fused to polished samples up to 134.0±43.4MPa for porcelain fused to alumina blasted samples. According to the statistical analysis, no significant difference were found on the shear bond strength values for different cooling rates. Processing method was statistically significant only for the polished samples, and airborne particle abrasion was statistically significant only for the fired samples. The type of the blasting material did not cause a statistically significant difference on the shear bond strength values. Shear bond strength of dental porcelain to Ti-6Al-4V alloys can be significantly improved from controlled conditions of surface treatments and processing methods.

  7. Interaction behaviors at the interface between liquid Al-Si and solid Ti-6Al-4V in ultrasonic-assisted brazing in air.

    PubMed

    Chen, Xiaoguang; Yan, Jiuchun; Gao, Fei; Wei, Jinghui; Xu, Zhiwu; Fan, Guohua

    2013-01-01

    Power ultrasonic vibration (20 kHz, 6 μm) was applied to assist the interaction between a liquid Al-Si alloy and solid Ti-6Al-4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti-6Al-4V surface, chemical dissolution of solid Ti-6Al-4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2-20 μm diameter-sized pits formed on the Ti-6Al-4V surface. Propagation of ultrasonic waves in the liquid Al-Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti-6Al-4V substrate, excessive chemical dissolution of solid Ti-6Al-4V into liquid Al-Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al-Si and Ti-6Al-4V can be produced by ultrasonic-assisted brazing in air.

  8. Structural characterization of the metal/glass interface in bioactive glass coatings on Ti-6Al-4V

    SciTech Connect

    Oku, T.; Suganuma, K.; Wallemberg, L.R.; Tomsia, A.P.; Gomez-Vega, J.M.; Saiz, E.

    1999-12-01

    Coating Ti-based implants with bioactive materials promotes joining between the prostheses and the bone as well as increasing long-term implant stability. In the present work, the interface between Ti-6Al-4V and bioactive silicate glass coatings, prepared using a simple enameling technique, is analyzed. High-resolution transmission electron microscopy of the glass/alloy interface shows the formation of a reaction layer ({approx}150 nm thick) composed of Ti5Si3 nanoparticles with a size of {approx}20 nm. This nanostructured interface facilitates the formation of a stable joint between the glass coating and the alloy.

  9. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    PubMed Central

    Mahdipoor, M.S.; Kirols, H.S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-01-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7–9 for Ti6Al4V and 11–13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

  10. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V.

    PubMed

    Mahdipoor, M S; Kirols, H S; Kevorkov, D; Jedrzejowski, P; Medraj, M

    2015-09-22

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ V(n), where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

  11. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V.

    PubMed

    Mahdipoor, M S; Kirols, H S; Kevorkov, D; Jedrzejowski, P; Medraj, M

    2015-01-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ V(n), where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

  12. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Mahdipoor, M. S.; Kirols, H. S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-09-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

  13. The ELI-NP facility for nuclear physics

    NASA Astrophysics Data System (ADS)

    Ur, C. A.; Balabanski, D.; Cata-Danil, G.; Gales, S.; Morjan, I.; Tesileanu, O.; Ursescu, D.; Ursu, I.; Zamfir, N. V.

    2015-07-01

    Extreme Light Infrastructure-Nuclear Physics (ELI-NP) is aiming to use extreme electromagnetic fields for nuclear physics research. The facility, currently under construction at Magurele-Bucharest, will comprise a high power laser system and a very brilliant gamma beam system. The technology involved in the construction of both systems is at the limits of the present-day's technological capabilities. The high power laser system will consist of two 10 PW lasers and it will produce intensities of up to 1023-1024 W/cm2. The gamma beam, produced via Compton backscattering of a laser beam on a relativistic electron beam, will be characterized by a narrow bandwidth (<0.5%) and tunable energy of up to almost 20 MeV. The research program of the facility covers a broad range of key topics in frontier fundamental physics and new nuclear physics. A particular attention is given to the development of innovative applications. In the present paper an overview of the project status and the overall performance characteristics of the main research equipment will be given. The main fundamental physics and applied research topics proposed to be studied at ELI-NP will also be briefly reviewed.

  14. Sodium hydroxide anodization of Ti-Al-4V adherends

    NASA Technical Reports Server (NTRS)

    Filbey, Jennifer A.; Wightman, J. P.; Progar, D. J.

    1987-01-01

    The use of sodium hydroxide anodization (SHA) for Ti-6Al-4V adherends is examined. The SHA surface is evaluated using SEM, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The SHA procedures of Kennedy et al. (1983) were employed in this experiment. The photomicrographs of the SHA (sandblasted) and PSHA (sandblasted and pickled) oxide surface reveal that the two surfaces differ. The PSHA is patchy and similar to a chromic acid anodization surface and the porosity of the PSHA is more uniform than the SHA surface. The compositions of the surfaces are studied. It is noted that SHA is an effective pretreatment for Ti-6Al-4V adherends.

  15. Biocorrosion of TiO2 nanoparticle coating of Ti-6Al-4V in DMEM under specific in vitro conditions

    NASA Astrophysics Data System (ADS)

    Höhn, Sarah; Virtanen, Sannakaisa

    2015-02-01

    A TiO2 nanoparticle coating was prepared on a biomedical Ti-6Al-4V alloy using "spin-coating" technique with a colloidal suspension of TiO2 nanopowders with the aim to optimize the surface morphology (e.g., roughness) for improved biocompatibility. The influence of a TiO2 nanoparticle (NP) coating on the corrosion behavior, metal ion release, and biomimetic apatite formation was studied in DMEM, at 37.5 °C with a continuous supply of 5% CO2. Electrochemical impedance spectroscopy measurements indicate a formation of a new layer on the surface of the NP-coated sample upon 28 days immersion in DMEM. Scanning electron microscopy (SEM) and X-ray spectroscopy confirm that the surface of the NP-coated Ti-6Al-4V shows a complete coverage by a Ca-phosphate layer in contrast to the non-coated Ti-6Al-4V alloy. Hence, the TiO2-NP coating strongly enhances biomimetic apatite formation on the alloy surface. In addition, the TiO2-NP coating can efficiently reduce Al-release from the alloy, for which the bare Ti-6Al-4V alloy is significant for at least 28 days of immersion in DMEM.

  16. Microstructure and mechanical properties of plasma sprayed HA/YSZ/Ti-6Al-4V composite coatings.

    PubMed

    Khor, K A; Gu, Y W; Pan, D; Cheang, P

    2004-08-01

    Plasma sprayed hydroxyapatite (HA) coatings on titanium alloy substrate have been used extensively due to their excellent biocompatibility and osteoconductivity. However, the erratic bond strength between HA and Ti alloy has raised concern over the long-term reliability of the implant. In this paper, HA/yttria stabilized zirconia (YSZ)/Ti-6Al-4V composite coatings that possess superior mechanical properties to conventional plasma sprayed HA coatings were developed. Ti-6Al-4V powders coated with fine YSZ and HA particles were prepared through a unique ceramic slurry mixing method. The so-formed composite powder was employed as feedstock for plasma spraying of the HA/YSZ/Ti-6Al-4V coatings. The influence of net plasma energy, plasma spray standoff distance, and post-spray heat treatment on microstructure, phase composition and mechanical properties were investigated. Results showed that coatings prepared with the optimum plasma sprayed condition showed a well-defined splat structure. HA/YSZ/Ti-6Al-4V solid solution was formed during plasma spraying which was beneficial for the improvement of mechanical properties. There was no evidence of Ti oxidation from the successful processing of YSZ and HA coated Ti-6Al-4V composite powders. Small amount of CaO apart from HA, ZrO(2) and Ti was present in the composite coatings. The microhardness, Young's modulus, fracture toughness, and bond strength increased significantly with the addition of YSZ. Post-spray heat treatment at 600 degrees C and 700 degrees C for up to 12h was found to further improve the mechanical properties of coatings. After the post-spray heat treatment, 17.6% increment in Young's modulus (E) and 16.3% increment in Vicker's hardness were achieved. The strengthening mechanisms of HA/YSZ/Ti-6Al-4V composite coatings were related to the dispersion strengthening by homogeneous distribution of YSZ particles in the matrix, the good mechanical properties of Ti-6Al-4V and the formation of solid solution among HA

  17. Dilatometric Analysis and Microstructural Investigation of the Sintering Mechanisms of Blended Elemental Ti-6Al-4V Powders

    NASA Astrophysics Data System (ADS)

    Kim, Youngmoo; Lee, Junho; Lee, Bin; Ryu, Ho Jin; Hong, Soon Hyung

    2016-09-01

    The densification behavior of mixed Ti and Al/V master alloy powders for Ti-6Al-4V was investigated by a series of dilatometry tests to measure the shrinkage of the samples with the sintering temperature. The corresponding microstructural changes were examined under various sintering conditions with optical microscopy, energy-dispersive spectroscopy, and X-ray diffraction analyses. From these results, the consolidation of the mixed powders was divided into two domains: (i) sintering densification and solute homogenization of Ti and Al/V master alloy particles below 1293 K (1020 °C), and (ii) densification of Ti alloy phases above 1293 K (1020 °C). In the lower temperature region, the inter-diffusion between Ti and Al/V master alloy particles dominated the sintering of the mixed powders because the chemical gradient between two types of particles outweighed the surface energy reduction. Following chemical homogenization, the densification induced the shrinkage of the Ti alloy phases to reduce their surface energies. These tendencies are also supported by the density and grain size variations of the sintered specimens with temperature. The apparent activation energies of the sintering and grain growth for Ti alloy particles are 85.91 ± 6.93 and 37.33 kJ/mol, respectively, similar to or slightly lower than those of pure Ti particles. The difference was attributed to the slower self-diffusion of Ti resulting from the alloying of Al and V into in the Ti matrix.

  18. An integrated experimental and computational approach to laser surface nitriding of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Dahotre, Sanket N.; Vora, Hitesh D.; Pavani, K.; Banerjee, Rajarshi

    2013-04-01

    Titanium and its alloys have been commonly used in many biological and industrial applications owing to their excellent mechanical and physical properties. However, they have been specifically inadequate for biomedical implants due to their inferior tribological properties (low wear resistance, higher coefficient of friction, and lower hardness). As a remedy, the process of laser nitriding has emerged from the past few decades as a unique method for tailoring the surface microstructures and/or composition of titanium for enhanced tribological characteristics of titanium and its alloys. In the present study, a multiphysics computational model was developed to predict the nitrogen diffusion length into the Ti-6Al-4V alloy under various laser processing conditions (laser power and scanning speed). XRD, SEM and EDS analyses were also conducted for phase identification, microstructural investigation, and estimating the nitrogen concentration, respectively. Both computational and experimental results indicated that the depth of nitrogen diffusion increased with decrease in scanning speed, and subsequent increase in laser interaction time and increase in input laser energy density.

  19. Joining of zirconium boride based refractory ceramics to Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Muolo, Maria Luigia; Ferrera, Elena; Morbelli, Luisa; Zanotti, Claudio; Passerone, Alberto

    2003-09-01

    The exploitation of the peculiar characteristics of ceramic refractory materials in extreme conditions (as for Thermal Protection Systems - TPS) often depends to a great extent on the ability to join different ceramics one to the other and to special metallic alloys. Joints may be achieved in a number of ways, but principally are made by either solid phase or liquid phase transformations (brazing). Brazed joints are difficult to realise in the presence of ceramic materials, due to the fact that they are not wet, in general, by liquid metals. This paper presents experimental results on the wettability characteristics of zirconium boride based materials (with Si3N4, Ni etc.) by an AgZr alloy, the microstructures and thermal tests of brazed joints with the special alloy Ti6Al4V. The wetting data will be examined in terms of interfacial characteristics and in terms of the kinetics of spreading. Thermal tests and models will be devoted to evaluate and measure the thermal insulation capacity of the ceramic layers in order to determine the optimal thickness as a function of the foreseen outer surface temperature.

  20. Thermal oxidation of medical Ti6Al4V blasted with ceramic particles: Effects on the microstructure, residual stresses and mechanical properties.

    PubMed

    Lieblich, M; Barriuso, S; Multigner, M; González-Doncel, G; González-Carrasco, J L

    2016-02-01

    Roughening of Ti6Al4V by blasting with alumina or zirconia particles improves the mechanical fixation of implants by increasing the surface area available for bone/implant apposition. Additional thermal oxidation treatments of the blasted alloy have already shown to be a complementary low-cost solution to enhancing the in vitro biocompatibility and corrosion resistance of the alloy. In this work, the effects of oxidation treatment on a grit blasted Ti6Al4V biomedical alloy have been analysed in order to understand the net effect of the combined treatments on the alloy fatigue properties. Synchrotron radiation diffraction experiments have been performed to measure residual stresses before and after the treatments and microstructural and hardness changes have been determined. Although blasting of Ti6Al4V with small spherical zirconia particles increases the alloy fatigue resistance with respect to unblasted specimens, fatigue strength after oxidation decreases below the unblasted value, irrespective of the type of particle used for blasting. Moreover, at 700°C the as-blasted compressive residual stresses (700MPa) are not only fully relaxed but even moderate tensile residual stresses, of about 120MPa, are found beneath the blasted surfaces. Contrary to expectations, a moderate increase in hardness occurs towards the blasted surface after oxidation treatments. This can be attributed to the fact that grit blasting modifies the crystallographic texture of the Ti6Al4V shifting it to a random texture, which affects the hardness values as shown by additional experiments on cold rolled samples. The results indicate that the oxidation treatment performed to improve biocompatibility and corrosion resistance of grit blasted Ti6Al4V should be carried out with caution since the alloy fatigue strength can be critically diminished below the value required for high load-bearing components. PMID:26458115

  1. Thermal oxidation of medical Ti6Al4V blasted with ceramic particles: Effects on the microstructure, residual stresses and mechanical properties.

    PubMed

    Lieblich, M; Barriuso, S; Multigner, M; González-Doncel, G; González-Carrasco, J L

    2016-02-01

    Roughening of Ti6Al4V by blasting with alumina or zirconia particles improves the mechanical fixation of implants by increasing the surface area available for bone/implant apposition. Additional thermal oxidation treatments of the blasted alloy have already shown to be a complementary low-cost solution to enhancing the in vitro biocompatibility and corrosion resistance of the alloy. In this work, the effects of oxidation treatment on a grit blasted Ti6Al4V biomedical alloy have been analysed in order to understand the net effect of the combined treatments on the alloy fatigue properties. Synchrotron radiation diffraction experiments have been performed to measure residual stresses before and after the treatments and microstructural and hardness changes have been determined. Although blasting of Ti6Al4V with small spherical zirconia particles increases the alloy fatigue resistance with respect to unblasted specimens, fatigue strength after oxidation decreases below the unblasted value, irrespective of the type of particle used for blasting. Moreover, at 700°C the as-blasted compressive residual stresses (700MPa) are not only fully relaxed but even moderate tensile residual stresses, of about 120MPa, are found beneath the blasted surfaces. Contrary to expectations, a moderate increase in hardness occurs towards the blasted surface after oxidation treatments. This can be attributed to the fact that grit blasting modifies the crystallographic texture of the Ti6Al4V shifting it to a random texture, which affects the hardness values as shown by additional experiments on cold rolled samples. The results indicate that the oxidation treatment performed to improve biocompatibility and corrosion resistance of grit blasted Ti6Al4V should be carried out with caution since the alloy fatigue strength can be critically diminished below the value required for high load-bearing components.

  2. A Study of Electrochemical Machining of Ti-6Al-4V in NaNO3 solution

    NASA Astrophysics Data System (ADS)

    Li, Hansong; Gao, Chuanping; Wang, Guoqian; Qu, Ningsong; Zhu, Di

    2016-10-01

    The titanium alloy Ti-6Al-4V is used in many industries including aviation, automobile manufacturing, and medical equipment, because of its low density, extraordinary corrosion resistance and high specific strength. Electrochemical machining (ECM) is a non-traditional machining method that allows applications to all kinds of metallic materials in regardless of their mechanical properties. It is widely applied to the machining of Ti-6Al-4V components, which usually takes place in a multicomponent electrolyte solution. In this study, a 10% NaNO3 solution was used to make multiple holes in Ti-6Al-4V sheets by through-mask electrochemical machining (TMECM). The polarization curve and current efficiency curve of this alloy were measured to understand the electrical properties of Ti-6Al-4V in a 10% NaNO3 solution. The measurements show that in a 10% NaNO3 solution, when the current density was above 6.56 A·cm‑2, the current efficiency exceeded 100%. According to polarization curve and current efficiency curve, an orthogonal TMECM experiment was conducted on Ti-6Al-4V. The experimental results suggest that with appropriate process parameters, high-quality holes can be obtained in a 10% NaNO3 solution. Using the optimized process parameters, an array of micro-holes with an aperture of 2.52 mm to 2.57 mm and maximum roundness of 9 μm were produced using TMECM.

  3. A Study of Electrochemical Machining of Ti-6Al-4V in NaNO3 solution

    PubMed Central

    Li, Hansong; Gao, Chuanping; Wang, Guoqian; Qu, Ningsong; Zhu, Di

    2016-01-01

    The titanium alloy Ti-6Al-4V is used in many industries including aviation, automobile manufacturing, and medical equipment, because of its low density, extraordinary corrosion resistance and high specific strength. Electrochemical machining (ECM) is a non-traditional machining method that allows applications to all kinds of metallic materials in regardless of their mechanical properties. It is widely applied to the machining of Ti-6Al-4V components, which usually takes place in a multicomponent electrolyte solution. In this study, a 10% NaNO3 solution was used to make multiple holes in Ti-6Al-4V sheets by through-mask electrochemical machining (TMECM). The polarization curve and current efficiency curve of this alloy were measured to understand the electrical properties of Ti-6Al-4V in a 10% NaNO3 solution. The measurements show that in a 10% NaNO3 solution, when the current density was above 6.56 A·cm−2, the current efficiency exceeded 100%. According to polarization curve and current efficiency curve, an orthogonal TMECM experiment was conducted on Ti-6Al-4V. The experimental results suggest that with appropriate process parameters, high-quality holes can be obtained in a 10% NaNO3 solution. Using the optimized process parameters, an array of micro-holes with an aperture of 2.52 mm to 2.57 mm and maximum roundness of 9 μm were produced using TMECM. PMID:27734951

  4. KD4v: Comprehensible Knowledge Discovery System for Missense Variant.

    PubMed

    Luu, Tien-Dao; Rusu, Alin; Walter, Vincent; Linard, Benjamin; Poidevin, Laetitia; Ripp, Raymond; Moulinier, Luc; Muller, Jean; Raffelsberger, Wolfgang; Wicker, Nicolas; Lecompte, Odile; Thompson, Julie D; Poch, Olivier; Nguyen, Hoan

    2012-07-01

    A major challenge in the post-genomic era is a better understanding of how human genetic alterations involved in disease affect the gene products. The KD4v (Comprehensible Knowledge Discovery System for Missense Variant) server allows to characterize and predict the phenotypic effects (deleterious/neutral) of missense variants. The server provides a set of rules learned by Induction Logic Programming (ILP) on a set of missense variants described by conservation, physico-chemical, functional and 3D structure predicates. These rules are interpretable by non-expert humans and are used to accurately predict the deleterious/neutral status of an unknown mutation. The web server is available at http://decrypthon.igbmc.fr/kd4v.

  5. KD4v: comprehensible knowledge discovery system for missense variant

    PubMed Central

    Luu, Tien-Dao; Rusu, Alin; Walter, Vincent; Linard, Benjamin; Poidevin, Laetitia; Ripp, Raymond; Moulinier, Luc; Muller, Jean; Raffelsberger, Wolfgang; Wicker, Nicolas; Lecompte, Odile; Thompson, Julie D.; Poch, Olivier; Nguyen, Hoan

    2012-01-01

    A major challenge in the post-genomic era is a better understanding of how human genetic alterations involved in disease affect the gene products. The KD4v (Comprehensible Knowledge Discovery System for Missense Variant) server allows to characterize and predict the phenotypic effects (deleterious/neutral) of missense variants. The server provides a set of rules learned by Induction Logic Programming (ILP) on a set of missense variants described by conservation, physico-chemical, functional and 3D structure predicates. These rules are interpretable by non-expert humans and are used to accurately predict the deleterious/neutral status of an unknown mutation. The web server is available at http://decrypthon.igbmc.fr/kd4v. PMID:22641855

  6. Effect of the overlapping factor on the microstructure and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V sheets

    SciTech Connect

    Gao, Xiao-Long; Liu, Jing; Zhang, Lin-Jie Zhang, Jian-Xun

    2014-07-01

    The effect of the overlapping factor on the microstructures and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V alloy sheets was investigated by microstructural observations, microhardness tests, tensile tests and fatigue tests. A microstructural examination shows that by increasing the overlapping factor, the grains in the fusion zone become coarser, and the width of the heat affected zone increases. As overlapping factor increases, the width of region composed completely of martensite α′ and the secondary α phase in the heat affected zone increases, consequently the gradient of microstructure along the direction from the fusion zone to base metal decreases, so does the gradient of microhardness. The results of tensile and fatigue tests reveal that the joints made using medium overlapping factor exhibit better mechanical properties than those welded with low and high overlapping factors. Based on the experimental results, it can be stated that a sound weld of Ti6Al4V alloy can be obtained if an appropriate overlapping factor is used. - Highlights: • The weld quality of Ti6Al4V alloy under various overlapping factors was assessed. • Tensile and fatigue tests were conducted with as-welded specimen. • Localized strain across the weld was measured using DIC photogrammetry system. • A sound weld of Ti6Al4V alloy is obtained by using right overlapping factor.

  7. Gas nitriding of Ti-6Al-4V by induction heating

    SciTech Connect

    Grosch, J.; Saglitz, M.

    1995-12-31

    The usually poor wear behavior of titanium materials can be improved by thermochemical surface heat treatment. In contrast to conventional procedures, which necessitate prolonged treatment, it is possible to reduce the heat treatment period considerably by means of HF induction. Serving as an example in this context is a Ti-6Al-4V titanium alloy that is to demonstrate the possibilities of induction gas nitriding. Temperature variations between 900 C and 1,600 C have resulted in homogeneous surface structures whose microstructures can basically be explained by the titanium-nitrogen diagram. In particular with the 1,600 C variant, the wear resistance has been improved, compared with the untreated titanium material there is a seventyfold increase in wear resistance.

  8. Yield Behavior of Solution Treated and Aged Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Ring, Andrew J.; Baker, Eric H.; Salem, Jonathan A.; Thesken, John C.

    2014-01-01

    Post yield uniaxial tension-compression tests were run on a solution treated and aged (STA), titanium 6-percent aluminum 4-percent vanadium (Ti-6Al-4V) alloy to determine the yield behavior on load reversal. The material exhibits plastic behavior almost immediately on load reversal implying a strong Bauschinger effect. The resultant stress-strain data was compared to a 1D mechanics model and a finite element model used to design a composite overwrapped pressure vessel (COPV). Although the models and experimental data compare well for the initial loading and unloading in the tensile regime, agreement is lost in the compressive regime due to the Bauschinger effect and the assumption of perfect plasticity. The test data presented here are being used to develop more accurate cyclic hardening constitutive models for future finite element design analysis of COPVs.

  9. Microstructure and inclusion of Ti-6Al-4V fabricated by selective laser melting

    NASA Astrophysics Data System (ADS)

    Huang, Qianli; Hu, Ningmin; Yang, Xing; Zhang, Ranran; Feng, Qingling

    2016-09-01

    Selective laser melting (SLM) was used in fabricating the dense part from pre-alloyed Ti-6Al-4V powder. The microstructural evolution and inclusion formation of as-fabricated part were characterized in depth. The microstructure was characterized by features of columnar prior β grains and acicular martensite α'. High density defects such as dislocations and twins can be produced in SLM process. Investigations on the inclusions find out that hard alpha inclusion, amorphous CaO and microcrystalline Al2O3 are three main inclusions formed in SLM. The inclusions formed at some specific sites on melt pool surface. The microstructural evolution and inclusion formation of as-fabricated material are closely related to the SLM process.

  10. Fracture Growth Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, Jeffrey W.; Martinez, Jonathan; McLean, Christopher

    2015-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant in orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent flaws will not cause failure during the design life. Material property inputs for this analysis require testing to determine the stress intensity factor for environmentally-assisted cracking (K (sub EAC)) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched specimens SE(B) representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to the monopropellant at 50 degrees Centigrade for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor of the Ti 6Al-4V forged tank material when exposed to AF-M315E monopropellant was found to be at least 22.0 kilopounds per square inch. The stress intensity factor of the weld material was at least 31.3 kilopounds per square inch.

  11. Fracture Mechanics Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, J. W.; Martinez, J.; McLean, C.

    2016-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant on orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent processing flaws will not cause failure during the design life of the tank. Material property inputs for this analysis require testing to determine the stress intensity factor for environment-assisted cracking (KEAC) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched, or SE(B), specimens representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to AF-M315E at 50 C for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor for environment-assisted cracking of the Ti 6Al-4V forged tank material was found to be at least 22 ksivin and at least 31 ksivin for the weld material when exposed to AF-M315E monopropellant.

  12. Fatigue behavior of Ti6Al4V and 316 LVM blasted with ceramic particles of interest for medical devices.

    PubMed

    Barriuso, S; Chao, J; Jiménez, J A; García, S; González-Carrasco, J L

    2014-02-01

    Grit blasting is used as a cost-effective method to increase the surface roughness of metallic biomaterials, as Ti6Al4V and 316 LVM, to enhance the osteointegration, fixation and stability of implants. Samples of these two alloys were blasted by using alumina and zirconia particles, yielding rough (up to Ra~8μm) and nearly smooth (up to Ra~1μm) surfaces, respectively. In this work, we investigate the sub-surface induced microstructural effects and its correlation with the mechanical properties, with special emphasis in the fatigue behavior. Blasting with zirconia particles increases the fatigue resistance whereas the opposite effect is observed using alumina ones. As in a conventional shot penning process, the use of rounded zirconia particles for blasting led to the development of residual compressive stresses at the surface layer, without zones of stress concentrators. Alumina particles are harder and have an angular shape, which confers a higher capability to abrade the surface, but also a high rate of breaking down on impact. The higher roughness and the presence of a high amount of embedded alumina particles make the blasted alloy prone to crack nucleation. Interestingly, the beneficial or detrimental role of blasting is more intense for the Ti6Al4V alloy than for the 316 steel. It is proposed that this behavior is related to their different strain hardening exponents and the higher mass fraction of particles contaminating the surface. The low value of this exponent for the Ti6Al4V alloy justifies the expected low sub-surface hardening during the severe plastic deformation, enhancing its capability to soft during cyclic loading. PMID:24216310

  13. Fatigue crack growth rate of Ti-6Al-4V considering the effects of fracture toughness and crack closure

    NASA Astrophysics Data System (ADS)

    Zhang, Junhong; Yang, Shuo; Lin, Jiewei

    2015-03-01

    Fatigue fracture is one of the main failure modes of Ti-6Al-4V alloy, fracture toughness and crack closure have strong effects on the fatigue crack growth(FCG) rate of Ti-6Al-4V alloy. The FCG rate of Ti-6Al-4V is investigated by using experimental and analytical methods. The effects of stress ratio, crack closure and fracture toughness on the FCG rate are studied and discussed. A modified prediction model of the FCG rate is proposed, and the relationship between the fracture toughness and the stress intensity factor(SIF) range is redefined by introducing a correcting coefficient. Notched plate fatigue tests (including the fracture toughness test and the FCG rate test) are conducted to investigate the influence of affecting factors on the FCG rate. Comparisons between the predicted results of the proposed model, the Paris model, the Walker model, the Sadananda model, and the experimental data show that the proposed model gives the best agreement with the test data particularly in the near-threshold region and the Paris region, and the corresponding calculated fatigue life is also accurate in the same regions. By considering the effects of fracture toughness and crack closure, the novel FCG rate prediction model not only improves the estimating accuracy, but also extends the adaptability of the FCG rate prediction model in engineering.

  14. Tribology and hydrophobicity of a biocompatible GPTMS/PFPE coating on Ti6Al4V surfaces.

    PubMed

    Panjwani, Bharat; Sinha, Sujeet K

    2012-11-01

    Tribological properties of perfluoropolyether (PFPE) coated 3-glycidoxypropyltrimethoxy silane (GPTMS) SAMs (self-assembled monolayers) onto Ti6Al4V alloy substrate were studied using ball-on-disk experiments. GPTMS SAMs deposition onto a Ti6Al4V alloy surface was carried out using solution phase method. Ultra-thin layer of PFPE was dip-coated onto SAMs modified specimens. Tribological tests were carried out at 0.2 N normal load and rotational speed of 200 rpm using track radius of 2 mm. Wear track and counterface surface conditions were investigated using optical microscopy. PFPE modified specimens were baked at 150 °C for 1h to investigate the effect of thermal treatment on tribological properties. Surface characterization tests such as contact angle measurement, AFM morphology and X-ray photoelectron spectroscopy were carried out for differently modified specimens. PFPE overcoat meets the requirements of cytotoxicity test using the ISO 10993-5 elution method. PFPE top layer lowered the coefficient of friction and increased wear durability for different specimens (with and without GPTMS intermediate layer). PFPE overcoat onto GPTMS showed significant increase in the wear resistance compared with overcoat onto bare Ti6Al4V specimens. The observed improvement in the tribological properties can be attributed to the change in the interaction of PFPE molecules with the substrate surface due to the GPTMS intermediate layer.

  15. Mechanical and chemical analyses across dental porcelain fused to CP titanium or Ti6Al4V.

    PubMed

    Souza, Júlio C M; Henriques, Bruno; Ariza, Edith; Martinelli, Antonio E; Nascimento, Rubens M; Silva, Filipe S; Rocha, Luís A; Celis, Jean-Pierre

    2014-04-01

    The aim of this study was to evaluate the evolution of mechanical properties and chemical variation across veneering dental porcelain fused to different titanium-based substrates. Test samples were synthesized by fusing dental feldspar-based porcelain onto commercially pure titanium grade II or Ti6Al4V alloy. Samples were cross-sectioned at angles of 10 and 90° to the interface plane. Afterwards, nanoindentation tests and Scanning Electron Microscopy (SEM) imaging coupled to an Energy Dispersive Spectroscopy (EDS) system were carried out across interfaces extending from the metal towards the porcelain area. Elemental diffusion profiles across the porcelain-to-metal interfaces were also obtained by EDS analysis. The mismatch in mechanical properties found in porcelain-to-Ti6Al4V interfaces was lower than that of porcelain-to-CP titanium. Cracking was noticed at low-thickness veneering dental porcelain regions after the nanoindentation tests of samples cross-sectioned at low angles to the interface plane. A wide reaction zone between titanium and porcelain as well as higher incidence of defects was noticed at the porcelain-to-CP titanium interfaces. This study confirmed Ti6Al4V as an improved alternative to CP-titanium as it showed to establish a better interface with the veneering dental porcelain considering the slight chemical interaction and the lower mechanical properties mismatch. The elastic modulus of porcelain-to-Ti6Al4V samples showed to be less sensitive to porcelain thickness variations.

  16. Properties of a porous Ti-6Al-4V implant with a low stiffness for biomedical application.

    PubMed

    Li, X; Wang, C-T; Zhang, W-G; Li, Y-C

    2009-02-01

    Porous Ti-6Al-4V alloy was fabricated using the electron beam melting (EBM) process. The phases of the as-received powder and fabricated samples were characterized using X-ray diffraction (XRD) analysis. The XRD peaks of both diffraction patterns agree well, which indicated that the EBM process has not changed the composition of Ti-6Al-4V. The fabricated samples exhibited a Vickers microhardness value of around 428 HV. The compression and three-point bending tests were performed to evaluate the mechanical properties of the porous Ti-6Al-4V implant with a porosity of around 60 per cent. The compressive yield strength, Young's modulus, and ultimate compressive strength were 194.6 MPa, 4.25 GPa, and 222.6 MPa respectively. The bending stiffness and bending strength were 3.7 GPa and 126.3 MPa respectively. These results demonstrated that the porous Ti-6Al-4V implant with a low stiffness and high porosity could be a promising biomaterial for biomedical applications.

  17. A review article: The mechanical properties and the microstructural behaviour of laser metal deposited Ti-6Al-4V and TiC composite

    NASA Astrophysics Data System (ADS)

    Erinosho, Mutiu F.; Akinlabi, Esther T.

    2016-03-01

    Titanium alloy (Ti-6Al-4V) Grade 5 has been regarded as the most useful alloy for the aerospace applications, due to their light weight properties. Today, laser technology is an energetic process in which the beam ejected can travel a longer distance and spot on the focused surface. The combination of metallic powder and laser beam has been used concurrently to form a solid figure. However, this combination has generated a permanently solidified metallurgical bonding between the laser-deposited metallic powders. Several research works have been conducted to improve the mechanical properties of the primary alloy, Ti-6Al-4V. This article conversely highlights the series of work that have been conducted on improving the mechanical properties and microstructures of the primary alloy with the addition of titanium carbide (TiC). The Ti-6Al-4V alloy has been widely selected in most critical part of a component. Their reinforcement with TiC composite particle has been achieved successfully through the optimal usage of laser technology. The characteristics of the reinforced component have vehemently improved the mechanical properties such as the tensile strength, wear resistance, fracture toughness and hardness; as well as the morphologies and phases of the microstructures.

  18. Chaos in the Showalter-Noyes-Bar-Eli model of the Belousov-Zhabotinskii reaction

    NASA Astrophysics Data System (ADS)

    Lindberg, David; Turner, Jack S.; Barkley, Dwight

    1990-03-01

    The observation of robust, large-scale chaos in the Showalter-Noyes-Bar-Eli model of the Belousov-Zhabotinskii reaction is reported. The chaos observed is comparable to that found in CSTR experiments at low flow rates.

  19. Spall fracture in additive manufactured Ti-6Al-4V

    DOE PAGES

    Jones, David Robert; Fensin, Saryu Jindal; Dippo, Olivia; Beal, Roberta Ann; Livescu, Verpnica; Martinez, Daniel Tito; Trujillo, Carl Patrick; Florando, J. N.; Kumar, M.; Gray, III, George Thompson

    2016-10-04

    Here, we present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on amore » plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.« less

  20. Spall fracture in additive manufactured Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Jones, D. R.; Fensin, S. J.; Dippo, O.; Beal, R. A.; Livescu, V.; Martinez, D. T.; Trujillo, C. P.; Florando, J. N.; Kumar, M.; Gray, G. T.

    2016-10-01

    We present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on a plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.

  1. On the interactions of human bone cells with Ti6Al4V thermally oxidized by means of laser shock processing.

    PubMed

    Crespo, Lara; Hierro-Oliva, Margarita; Barriuso, Sandra; Vadillo-Rodríguez, Virginia; Montealegre, M Ángeles; Saldaña, Laura; Gomez-Barrena, Enrique; González-Carrasco, José Luis; González-Martín, María Luisa; Vilaboa, Nuria

    2016-02-01

    We investigated a Ti6Al4V alloy modified by means of laser peening in the absence of sacrificial coatings. As a consequence of the temperature rise during laser focusing, melting and ablation generated an undulated surface that exhibits an important increase in the content of titanium oxides and OH- ions. Human mesenchymal stem cells and osteoblasts cultured on the oxidized alloy develop noticeable filopodia and lamellipodia. Their paxillin-stained focal adhesions are smaller than in cells attached to the untreated alloy and exhibit a marked loss of colocalization with the ends of actin stress fibers. An important imbalance of phosphorylation and/or dephosphorylation of the focal adhesion kinase is detected in cells grown on the oxidized alloy. Although these mechanisms of adhesion are deeply altered, the surface treatment does not affect cell attachment or proliferation rates on the alloy. Human mesenchymal stem cells cultured on the treated alloy in media containing osteogenic inducers differentiate towards the osteoblastic phenotype to a higher extent than those on the untreated surface. Also, the specific functions of human osteoblasts cultured on these media are enhanced on the treated alloy. In summary, laser peening tailors the Ti6Al4V surface to yield an oxidized layer with increased roughness that allows the colonization and activities of bone-lineage cells. PMID:26835650

  2. On the interactions of human bone cells with Ti6Al4V thermally oxidized by means of laser shock processing.

    PubMed

    Crespo, Lara; Hierro-Oliva, Margarita; Barriuso, Sandra; Vadillo-Rodríguez, Virginia; Montealegre, M Ángeles; Saldaña, Laura; Gomez-Barrena, Enrique; González-Carrasco, José Luis; González-Martín, María Luisa; Vilaboa, Nuria

    2016-02-02

    We investigated a Ti6Al4V alloy modified by means of laser peening in the absence of sacrificial coatings. As a consequence of the temperature rise during laser focusing, melting and ablation generated an undulated surface that exhibits an important increase in the content of titanium oxides and OH- ions. Human mesenchymal stem cells and osteoblasts cultured on the oxidized alloy develop noticeable filopodia and lamellipodia. Their paxillin-stained focal adhesions are smaller than in cells attached to the untreated alloy and exhibit a marked loss of colocalization with the ends of actin stress fibers. An important imbalance of phosphorylation and/or dephosphorylation of the focal adhesion kinase is detected in cells grown on the oxidized alloy. Although these mechanisms of adhesion are deeply altered, the surface treatment does not affect cell attachment or proliferation rates on the alloy. Human mesenchymal stem cells cultured on the treated alloy in media containing osteogenic inducers differentiate towards the osteoblastic phenotype to a higher extent than those on the untreated surface. Also, the specific functions of human osteoblasts cultured on these media are enhanced on the treated alloy. In summary, laser peening tailors the Ti6Al4V surface to yield an oxidized layer with increased roughness that allows the colonization and activities of bone-lineage cells.

  3. Straight talk with...Daniel Levy. Interviewed by Elie Dolgin.

    PubMed

    Levy, Daniel

    2013-10-01

    The Framingham Heart Study (FHS) has long been a beacon of biomedical research, yielding landmark findings on everything from the links between elevated blood pressure and stroke to the genetic risk factors underlying cardiac arrhythmias. Now, the fabled 65-year-long study of cardiovascular disease is the beacon of a more modern trend in science: tight budgets. Thanks to the automatic cuts in US government spending known as sequestration, the approximately $9-million-per-year contract the FHS receives from the US National Heart, Lung, and Blood Institute (NHLBI) was reduced by $4 million on 1 August. The renewal of the contract, scheduled for 2015, is expected to run for only two or three years, instead of the usual seven as it has been in the past. And next month, the most visible effects of the cuts will take hold, when 19 layoffs (out of a total of 90 total staff members) go into effect. Overseeing the budget-related turbulence is Daniel Levy, a medical officer at the NHLBI who joined the FHS nearly 30 years ago and has served as the study's director since 1994. Elie Dolgin met with Levy in Framingham, on the outskirts of Boston, to discuss how he's taking the new funding realities to heart.

  4. Evaluation of ARCAM Deposited Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Slattery, Kevin; Slaughter, Blake; Speorl, Emily; Good, James; Gilley, Scott; McLemore, Carole

    2008-01-01

    A wide range of Metal Additive Manufacturing (MAM) technologies are becoming available. One of the challenges in using new technologies for aerospace systems is demonstrating that the process and system has the ability to manufacture components that meet the high quality requirements on a statistically significant basis. The widest-used system for small to medium sized components is the ARCAM system manufactured in Gothenburg, Sweden. This system features a 4kW electron-beam gun, and has a chamber volume of 250mm long x 250mm wide x 250mm to 400mm tall. This paper will describe the basis for the quality and consistency requirements, the experimental and evaluation procedures used for the evaluation, and an analysis of the results for Ti-6Al-4V.

  5. Eli Lilly and Company's bioethics framework for human biomedical research.

    PubMed

    Van Campen, Luann E; Therasse, Donald G; Klopfenstein, Mitchell; Levine, Robert J

    2015-11-01

    Current ethics and good clinical practice guidelines address various aspects of pharmaceutical research and development, but do not comprehensively address the bioethical responsibilities of sponsors. To fill this void, in 2010 Eli Lilly and Company developed and implemented a Bioethics Framework for Human Biomedical Research to guide ethical decisions. (See our companion article that describes how the framework was developed and implemented and provides a critique of its usefulness and limitations.) This paper presents the actual framework that serves as a company resource for employee education and bioethics deliberations. The framework consists of four basic ethical principles and 13 essential elements for ethical human biomedical research and resides within the context of our company's mission, vision and values. For each component of the framework, we provide a high-level overview followed by a detailed description with cross-references to relevant well regarded guidance documents. The principles and guidance described should be familiar to those acquainted with research ethics. Therefore the novelty of the framework lies not in the foundational concepts presented as much as the attempt to specify and compile a sponsor's bioethical responsibilities to multiple stakeholders into one resource. When such a framework is employed, it can serve as a bioethical foundation to inform decisions and actions throughout clinical planning, trial design, study implementation and closeout, as well as to inform company positions on bioethical issues. The framework is, therefore, a useful tool for translating ethical aspirations into action - to help ensure pharmaceutical human biomedical research is conducted in a manner that aligns with consensus ethics principles, as well as a sponsor's core values.

  6. Friction Stir Processing of Investment-Cast Ti-6Al-4V: Microstructure and Properties

    NASA Astrophysics Data System (ADS)

    Pilchak, A. L.; Norfleet, D. M.; Juhas, M. C.; Williams, J. C.

    2008-07-01

    Investment-cast titanium components are becoming increasingly common in the aerospace industry due to the ability to produce large, complex, one-piece components that were previously fabricated by mechanically fastening multiple pieces together. The fabricated components are labor-intensive and the fastener holes are stress concentrators and prime sites for fatigue crack initiation. The castings are typically hot-isostatically-pressed (HIP) to close internal porosity, but have a coarse, fully lamellar structure that has low resistance to fatigue crack initiation. The as-cast + HIP material exhibited 1- to 1.5-mm prior β grains containing a fully lamellar α + β microstructure consistent with slow cooling from above the β transus. Friction stir processing (FSP) was used to locally modify the microstructure on the surface of an investment-cast Ti-6Al-4V plate. Friction stir processing converted the as-cast microstructure to fine (1- to 2-μm) equiaxed α grains. Using micropillars created with a dual-beam focused ion beam device, it was found that the fine-grained equiaxed structure has about a 12 pct higher compressive yield stress. In wrought products, higher strength conditions are more resistant to fatigue crack initiation, while the coarse lamellar microstructure in the base material has better fatigue crack growth resistance. In combination, these two microstructures can increase the fatigue life of titanium alloy castings by increasing the number of cycles prior to crack initiation while retaining the same low-crack growth rates of the colony microstructure in the remainder of the component. In the current study, high-cycle fatigue testing of investment-cast Ti-6Al-4V was performed on four-point bend specimens. Early results show that FSP can increase fatigue strength dramatically.

  7. Characterization and mechanical properties investigation of TiN-Ag films onto Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Du, Dongxing; Liu, Daoxin; Zhang, Xiaohua; Tang, Jingang; Xiang, Dinggen

    2016-03-01

    To investigate their effect on fretting fatigue (FF) resistance of a Ti-6Al-4V alloy, hard solid lubricating composite films of TiN with varying silver contents (TiN-Ag) were deposited on a Ti-6Al-4V alloy using ion-assisted magnetron sputtering. The surface morphology and structure were analyzed by atomic force microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. The hardness, bonding strength, and toughness of films were tested using a micro-hardness tester, scratch tester, and a repeated press-press test system that was manufactured in-house, respectively. The FF resistance of TiN-Ag composite films was studied using self-developed devices. The results show that the FF resistance of a titanium alloy can be improved by TiN-Ag composite films, which were fabricated using hard TiN coating doped with soft Ag. The FF life of Ag0.5, Ag2, Ag5, Ag10 and Ag20 composite films is 2.41, 3.18, 3.20, 2.94 and 2.87 times as great as that of the titanium alloy, respectively. This is because the composite films have the better toughness, friction lubrication, and high bonding strength. When the atomic fraction of Ag changes from 2% to 5%, the FF resistance of the composite films shows the best performance. This is attributed to the surface integrity of the composite film is sufficiently fine to prevent the initiation and early propagation of FF cracks.

  8. High power laser beam melting of Ti6Al4V on formed sheet metal to achieve hybrid structures

    NASA Astrophysics Data System (ADS)

    Ahuja, Bhrigu; Schaub, Adam; Karg, Michael; Schmidt, Roman; Merklein, Marion; Schmidt, Michael

    2015-03-01

    Motivated by the desire to combine the advantages of two manufacturing concepts, namely Additive Manufacturing and sheet metal forming, the concept of hybrid processes emerged. Laser Beam Melting process with its characteristic layer by layer fabrication methodology has already been proved to be successful in fabricating fully dense 3D structures with micro sized Ti6Al4V powder. The presented research focuses on direct fabrication of Ti6 Al4V Additive Structures on a thin pre-formed Ti6 Al4V sheet metal substrate. In the state of the art Laser Beam Melting process, fabrication of solid structures is done on a support structure attached to a thick conventionally manufactured base plate. The state of the art process also uses a 200°C pre-heating of the fabrication platform in order to reduce the effect of heat induced stresses on the fabricated structures. Within the hybrid fabrication concept, 3D structures are directly fabricated on a thin sheet metal and the thermodynamic conditions are significantly different in comparison to the conventional process. The research aims at understanding the fundamental aspects of the interaction between the formed sheet metal and additive structure determines the corresponding mechanical characteristics. The interaction process during the fabrication exposes the alloy locally to non-optimum thermal cycles and the research therefore aims to understand the various influencing factors involved during the fabrication process. The system technology modifications required to achieve the aimed fabrication are also discussed in the presented research.

  9. In vitro fibroblast and pre-osteoblastic cellular responses on laser surface modified Ti-6Al-4V.

    PubMed

    Chikarakara, Evans; Fitzpatrick, Patricia; Moore, Eric; Levingstone, Tanya; Grehan, Laura; Higginbotham, Clement; Vázquez, Mercedes; Bagga, Komal; Naher, Sumsun; Brabazon, Dermot

    2014-12-29

    The success of any implant, dental or orthopaedic, is driven by the interaction of implant material with the surrounding tissue. In this context, the nature of the implant surface plays a direct role in determining the long term stability as physico-chemical properties of the surface affect cellular attachment, expression of proteins, and finally osseointegration. Thus to enhance the degree of integration of the implant into the host tissue, various surface modification techniques are employed. In this work, laser surface melting of titanium alloy Ti-6Al-4V was carried out using a CO2 laser with an argon gas atmosphere. Investigations were carried out to study the influence of laser surface modification on the biocompatibility of Ti-6Al-4V alloy implant material. Surface roughness, microhardness, and phase development were recorded. Initial knowledge of these effects on biocompatibility was gained from examination of the response of fibroblast cell lines, which was followed by examination of the response of osteoblast cell lines which is relevant to the applications of this material in bone repair. Biocompatibility with these cell lines was analysed via Resazurin cell viability assay, DNA cell attachment assay, and alamarBlue metabolic activity assay. Laser treated surfaces were found to preferentially promote cell attachment, higher levels of proliferation, and enhanced bioactivity when compared to untreated control samples. These results demonstrate the tremendous potential of this laser surface melting treatment to significantly improve the biocompatibility of titanium implants in vivo.

  10. A nano-scale mirror-like surface of Ti–6Al–4V attained by chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Chenliang, Liang; Weili, Liu; Shasha, Li; Hui, Kong; Zefang, Zhang; Zhitang, Song

    2016-05-01

    Metal Ti and its alloys have been widely utilized in the fields of aviation, medical science, and micro-electro-mechanical systems, for its excellent specific strength, resistance to corrosion, and biological compatibility. As the application of Ti moves to the micro or nano scale, however, traditional methods of planarization have shown their short slabs. Thus, we introduce the method of chemical mechanical polishing (CMP) to provide a new way for the nano-scale planarization method of Ti alloys. We obtain a mirror-like surface, whose flatness is of nano-scale, via the CMP method. We test the basic mechanical behavior of Ti–6Al–4V (Ti64) in the CMP process, and optimize the composition of CMP slurry. Furthermore, the possible reactions that may take place in the CMP process have been studied by electrochemical methods combined with x-ray photoelectron spectroscopy (XPS). An equivalent circuit has been built to interpret the dynamic of oxidation. Finally, a model has been established to explain the synergy of chemical and mechanical effects in the CMP of Ti–6Al–4V. Project supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period of China (Grant No. 2009ZX02030-1), the National Natural Science Foundation of China (Grant No. 51205387), the Support by Science and Technology Commission of Shanghai City, China (Grant No. 11nm0500300), and the Science and Technology Commission of Shanghai City, China (Grant No. 14XD1425300).

  11. A nano-scale mirror-like surface of Ti-6Al-4V attained by chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Chenliang, Liang; Weili, Liu; Shasha, Li; Hui, Kong; Zefang, Zhang; Zhitang, Song

    2016-05-01

    Metal Ti and its alloys have been widely utilized in the fields of aviation, medical science, and micro-electro-mechanical systems, for its excellent specific strength, resistance to corrosion, and biological compatibility. As the application of Ti moves to the micro or nano scale, however, traditional methods of planarization have shown their short slabs. Thus, we introduce the method of chemical mechanical polishing (CMP) to provide a new way for the nano-scale planarization method of Ti alloys. We obtain a mirror-like surface, whose flatness is of nano-scale, via the CMP method. We test the basic mechanical behavior of Ti-6Al-4V (Ti64) in the CMP process, and optimize the composition of CMP slurry. Furthermore, the possible reactions that may take place in the CMP process have been studied by electrochemical methods combined with x-ray photoelectron spectroscopy (XPS). An equivalent circuit has been built to interpret the dynamic of oxidation. Finally, a model has been established to explain the synergy of chemical and mechanical effects in the CMP of Ti-6Al-4V. Project supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period of China (Grant No. 2009ZX02030-1), the National Natural Science Foundation of China (Grant No. 51205387), the Support by Science and Technology Commission of Shanghai City, China (Grant No. 11nm0500300), and the Science and Technology Commission of Shanghai City, China (Grant No. 14XD1425300).

  12. The elicitin-like glycoprotein, ELI025, is secreted by the pathogenic oomycete Pythium insidiosum and evades host antibody responses.

    PubMed

    Lerksuthirat, Tassanee; Lohnoo, Tassanee; Inkomlue, Ruchuros; Rujirawat, Thidarat; Yingyong, Wanta; Khositnithikul, Rommanee; Phaonakrop, Narumon; Roytrakul, Sittiruk; Sullivan, Thomas D; Krajaejun, Theerapong

    2015-01-01

    Pythium insidiosum is a unique oomycete that can infect humans and animals. Patients with a P. insidiosum infection (pythiosis) have high rates of morbidity and mortality. The pathogen resists conventional antifungal drugs. Information on the biology and pathogenesis of P. insidiosum is limited. Many pathogens secrete proteins, known as effectors, which can affect the host response and promote the infection process. Elicitins are secretory proteins and are found only in the oomycetes, primarily in Phytophthora and Pythium species. In plant-pathogenic oomycetes, elicitins function as pathogen-associated molecular pattern molecules, sterol carriers, and plant defense stimulators. Recently, we reported a number of elicitin-encoding genes from the P. insidiosum transcriptome. The function of elicitins during human infections is unknown. One of the P. insidiosum elicitin-encoding genes, ELI025, is highly expressed and up-regulated at body temperature. This study aims to characterize the biochemical, immunological, and genetic properties of the elicitin protein, ELI025. A 12.4-kDa recombinant ELI025 protein (rELI025) was expressed in Escherichia coli. Rabbit anti-rELI025 antibodies reacted strongly with the native ELI025 in P. insidiosum's culture medium. The detected ELI025 had two isoforms: glycosylated and non-glycosylated. ELI025 was not immunoreactive with sera from pythiosis patients. The region near the transcriptional start site of ELI025 contained conserved oomycete core promoter elements. In conclusion, ELI025 is a small, abundant, secreted glycoprotein that evades host antibody responses. ELI025 is a promising candidate for development of diagnostic and therapeutic targets for pythiosis. PMID:25793767

  13. The Elicitin-Like Glycoprotein, ELI025, Is Secreted by the Pathogenic Oomycete Pythium insidiosum and Evades Host Antibody Responses

    PubMed Central

    Lerksuthirat, Tassanee; Lohnoo, Tassanee; Inkomlue, Ruchuros; Rujirawat, Thidarat; Yingyong, Wanta; Khositnithikul, Rommanee; Phaonakrop, Narumon; Roytrakul, Sittiruk; Sullivan, Thomas D.; Krajaejun, Theerapong

    2015-01-01

    Pythium insidiosum is a unique oomycete that can infect humans and animals. Patients with a P. insidiosum infection (pythiosis) have high rates of morbidity and mortality. The pathogen resists conventional antifungal drugs. Information on the biology and pathogenesis of P. insidiosum is limited. Many pathogens secrete proteins, known as effectors, which can affect the host response and promote the infection process. Elicitins are secretory proteins and are found only in the oomycetes, primarily in Phytophthora and Pythium species. In plant-pathogenic oomycetes, elicitins function as pathogen-associated molecular pattern molecules, sterol carriers, and plant defense stimulators. Recently, we reported a number of elicitin-encoding genes from the P. insidiosum transcriptome. The function of elicitins during human infections is unknown. One of the P. insidiosum elicitin-encoding genes, ELI025, is highly expressed and up-regulated at body temperature. This study aims to characterize the biochemical, immunological, and genetic properties of the elicitin protein, ELI025. A 12.4-kDa recombinant ELI025 protein (rELI025) was expressed in Escherichia coli. Rabbit anti-rELI025 antibodies reacted strongly with the native ELI025 in P. insidiosum’s culture medium. The detected ELI025 had two isoforms: glycosylated and non-glycosylated. ELI025 was not immunoreactive with sera from pythiosis patients. The region near the transcriptional start site of ELI025 contained conserved oomycete core promoter elements. In conclusion, ELI025 is a small, abundant, secreted glycoprotein that evades host antibody responses. ELI025 is a promising candidate for development of diagnostic and therapeutic targets for pythiosis. PMID:25793767

  14. Wear of Steel and Ti6Al4V Rollers in Vacuum

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.; Shareef, Iqbal

    2012-01-01

    This investigation was prompted by results of a qualification test of a mechanism to be used for the James Webb Space Telescope. Post-test inspections of the qualification test article revealed some loose wear debris and wear of the steel rollers and the mating Ti6Al4V surfaces. An engineering assessment of the design and observations from the tested qualification unit suggested that roller misalignment was a controlling factor. The wear phenomena were investigated using dedicated laboratory experiments. Tests were done using a vacuum roller rig for a range of roller misalignment angles. The wear in these tests was mainly adhesive wear. The measured wear rates were highly correlated to the misalignment angle. For all tests with some roller misalignment, the steel rollers lost mass while the titanium rollers gained mass indicating strong adhesion of the steel with the titanium alloy. Inspection of the rollers revealed that the adhesive wear was a two-way process as titanium alloy was found on the steel rollers and vice versa. The qualification test unit made use of 440F steel rollers in the annealed condition. Both annealed 440F steel rollers and hardened 440C rollers were tested in the vacuum roller rig to investigate possibility to reduce wear rates and the risk of loose debris formation. The 440F and 440C rollers had differing wear behaviors with significantly lesser wear rates for the 440C. For the test condition of zero roller misalignment, the adhesive wear rates were very low, but still some loose debris was formed

  15. Thermoelectric assessment of laser peening induced effects on a metallic biomaterial Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Carreón, H.; Barriuso, S.; Porro, J. A.; González-Carrasco, J. L.; Ocaña, J. L.

    2014-03-01

    Laser peening has recently emerged as a useful technique to overcome detrimental effects associated to another wellknown surface modification processes such as shot peening or grit blasting used in the biomedical field. It is worth to notice that besides the primary residual stress effect, thermally induced effects might also cause subtle surface and subsurface microstructural changes that might influence corrosion resistance. Moreover, since maximum loads use to occur at the surface, they could also play a critical role in the fatigue strength. In this work, plates of Ti-6Al-4V alloy of 7 mm in thickness were modified by laser peening without using a sacrificial outer layer. Irradiation by a Q-switched Nd-YAG laser (9.4 ns pulse length) working in fundamental harmonic at 2.8 J/pulse and with water as confining medium was used. Laser pulses with a 1.5 mm diameter at an equivalent overlapping density (EOD) of 5000 cm-2 were applied. Attempts to analyze the global induced effects after laser peening were addressed by using the contacting and non-contacting thermoelectric power (TEP) techniques. It was demonstrated that the thermoelectric method is entirely insensitive to surface topography while it is uniquely sensitive to subtle variations in thermoelectric properties, which are associated with the different material effects induced by different surface modification treatments. These results indicate that the stress-dependence of the thermoelectric power in metals produces sufficient contrast to detect and quantitatively characterize regions under compressive residual stress based on their thermoelectric power contrast with respect to the surrounding intact material. However, further research is needed to better separate residual stress effects from secondary material effects, especially in the case of low-conductivity engineering materials like titanium alloys.

  16. Short-term microvascular response of striated muscle to cp-Ti, Ti-6Al-4V, and Ti-6Al-7Nb.

    PubMed

    Pennekamp, Peter H; Gessmann, Jan; Diedrich, Oliver; Burian, Björn; Wimmer, Markus A; Frauchiger, Vinzenz M; Kraft, Clayton N

    2006-03-01

    Due to excellent mechanical properties and good corrosion resistance, titanium-aluminium-vanadium (Ti-6Al-4V) and titanium-aluminium-niobium (Ti-6Al-7Nb) are extensively used for orthopedic surgery. Concern has been voiced concerning the implications of the constituent vanadium in Ti-6Al-4V on the surrounding environment. Particularly in osteosynthesis where the alloys stand in direct contact to skeletal muscle, undesirable biologic reactions may have severe consequences. In a comparative study, we assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the metals Ti-6Al-4V, Ti-6Al-7Nb, and commercially pure titanium (cpTi), thereby drawing conclusions on their short-term inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we quantified primary and secondary leukocyte-endothelial cell interaction, leukocyte extravasation, microvascular diameter change, and capillary perfusion in collecting and postcapillary venules of skeletal muscle. A manifest discrepancy between the metals concerning impact on local microvascular parameters was not found. All metals induced an only transient and moderate inflammatory response. Only a slight increase in leukocyte recruitment and a more sluggish recuperation of inflammatory parameters in animals treated with Ti-6Al-4V compared to the other two metals suggested a minor, overall not significant discrepancy in biocompatibility. Gross toxicity of bulk Ti-6Al-4V on surrounding tissue could not be found. Conclusively, the commonly used biomaterials Ti-6Al-4V, Ti-6Al-7Nb, and cpTi induce an only transient inflammatory answer of the skeletal muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys and cpTi do not cause adverse biologic reactions in striated muscle.

  17. Implementation status of the extreme light infrastructure - nuclear physics (ELI-NP) project

    NASA Astrophysics Data System (ADS)

    Gales, S.; Zamfir, N. V.

    2015-02-01

    The Project Extreme Light Infrastructure (ELI) is part of the European Strategic Forum for Research Infrastructures (ESFRI) Roadmap. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

  18. Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009.

    PubMed

    Maverakis, Emanual

    2012-01-01

    During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

  19. Implementation status of the extreme light infrastructure - nuclear physics (ELI-NP) project

    SciTech Connect

    Gales, S. Zamfir, N. V.

    2015-02-24

    The Project Extreme Light Infrastructure (ELI) is part of the European Strategic Forum for Research Infrastructures (ESFRI) Roadmap. ELI will be built as a network of three complementary pillars at the frontier of laser technologies. The ELI-NP pillar (NP for Nuclear Physics) is under construction near Bucharest (Romania) and will develop a scientific program using two 10 PW lasers and a Compton back-scattering high-brilliance and intense gamma beam, a marriage of laser and accelerator technology at the frontier of knowledge. In the present paper, the technical description of the facility, the present status of the project as well as the science, applications and future perspectives will be discussed.

  20. Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites

    NASA Astrophysics Data System (ADS)

    Jiao, Y.; Huang, L. J.; Duan, T. B.; Wei, S. L.; Kaveendran, B.; Geng, L.

    2016-09-01

    Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature.

  1. Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites

    PubMed Central

    Jiao, Y.; Huang, L. J.; Duan, T. B.; Wei, S. L.; Kaveendran, B.; Geng, L.

    2016-01-01

    Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature. PMID:27622992

  2. Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites.

    PubMed

    Jiao, Y; Huang, L J; Duan, T B; Wei, S L; Kaveendran, B; Geng, L

    2016-01-01

    Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature. PMID:27622992

  3. Micro-Structures of Hard Coatings Deposited on Titanium Alloys by Laser Alloying Technique

    NASA Astrophysics Data System (ADS)

    Li, Wei; Yu, Huijun; Chen, Chuanzhong; Wang, Diangang; Weng, Fei

    2013-02-01

    This work is based on micro-structural performance of the Ti-B4C-C laser alloying coatings on Ti-6Al-4V titanium alloy. The test results indicated that laser alloying of the Ti-B4C-C pre-placed powders on the Ti-6Al-4V alloy substrate can form the ceramics reinforced hard alloying coatings, which increased the micro-hardness and wear resistance of substrate. The test result also indicated that the TiB phase was produced in alloying coating, which corresponded to its (101) crystal plane. In addition, yttria has a refining effect on micro-structures of the laser alloying coating, and its refinement mechanism was analyzed. This research provided essential experimental and theoretical basis to promote the applications of the laser alloying technique in manufacturing and repairing of the aerospace parts.

  4. Phase Transformations and Formation of Ultra-Fine Microstructure During Hydrogen Sintering and Phase Transformation (HSPT) Processing of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Sun, Pei; Fang, Zhigang Zak; Koopman, Mark; Xia, Yang; Paramore, James; Ravi Chandran, K. S.; Ren, Yang; Lu, Jun

    2015-12-01

    The hydrogen sintering and phase transformation (HSPT) process is a novel powder metallurgy method for producing Ti alloys, particularly the Ti-6Al-4V alloy, with ultra-fine microstructure in the as-sintered state. The ultra-fine microstructure is obtained as a direct result of the use of H2 gas during sintering. The refinement of the microstructure during HSPT is similar to that of thermal hydrogen processing (THP) of bulk Ti alloys. For both THP and HSPT of Ti-6Al-4V alloy, the mechanisms of the grain refinement depend on the phase equilibria and phase transformations in the presence of hydrogen, which are surprisingly still not well established to date and are still subjected to research and debate. In recent work by the present authors, a pseudo-binary phase diagram of (Ti-6Al-4V)-H has been determined by using in situ synchrotron XRD and TGA/DSC techniques. Aided by this phase diagram, the current paper focuses on the series of phase transformations during sintering and cooling of Ti-6Al-4V in a hydrogen atmosphere and the mechanisms for the formation of the ultra-fine microstructures obtained. Using experimental techniques, including in situ synchrotron XRD, SEM, EBSD, and TEM, the microstructural refinement was found to be the result of (1) the precipitation of ultra-fine α/α2 within coarse β grains during an isothermal hold at intermediate temperatures, and (2) the eutectoid transformation of β → α + δ at approximately 473 K (200 °C).

  5. Wetting Behavior of Laser Synthetic Surface Micro Textures on Ti-6Al-4V for Bioapplication

    SciTech Connect

    Dahotre, Narendra B; Paital, Sameer R; Samant, Anoop N; Daniel, Claus

    2010-01-01

    Wettability at the surface of an implant material play a key role in its success as it modulate the protein adsorption and thereby influences cell attachment and tissue integration at the interface. Hence, surface engineering of implantable materials to enhance wettability to physiological fluid under in vivo conditions is an area of active research. In light of this, in the present work a laser based optical interference and direct melting techniques were used to develop synthetic micro textures on Ti-6Al-4V alloys and their effects on wettability were systematically studied. Improved wettability to simulated body fluid and distilled water was observed for the Ca-P coatings obtained by direct melting technique. This superior wettability was attributed to both the appropriate surface chemistry and three dimensional surface features obtained using this technique. To assert a better control on surface texture and wettability a three dimensional thermal model based on COMSOL sTM multiphysics was employed to predict the features obtained by laser melting technique. The effect of physical texture and wetting on biocompatibility of laser processed Ca-P coating was evaluated in the preliminary efforts on culturing of mouse MC3T3-E1 osteoblast cells.

  6. Biocompatibility and compressive properties of Ti-6Al-4V scaffolds having Mg element.

    PubMed

    Kalantari, Seyed Mohammad; Arabi, Hossein; Mirdamadi, Shamsodin; Mirsalehi, Seyed Ali

    2015-08-01

    Porous scaffolds of Ti-6Al-4V were produced by mixing of this alloy with different amount of magnesium (Mg) powders. The mixtures were compacted in steel die by applying uniaxial pressure of 500 MPa before sintering the compacts in sealed quartz tubes at 900 °C for 2 h. Employing Archimedes׳ principle and Image Tool software, the total and open volume percentages of porosities within the scaffolds were found to be in the range of 47-64% and 41-47%, respectively. XRD results of titanium before and after sintering showed that no contamination, neither oxides nor nitrides formed during processes. Compressive properties of the scaffolds were studied using an Instron machine. The observed compressive strength and Young׳s module of the scaffolds were in the range of 72-132 MPa, and 37-47 GPa, respectively. Cell attachment and proliferation rate of MG-63 on porous samples were investigated. The results showed that proliferation rate increased with increasing Mg content. However no clear differences were observed between samples regarding cell attachment, so that bridges were observed in all cell gaps within the scaffolds. PMID:25955560

  7. Wetting behaviour of laser synthetic surface microtextures on Ti-6Al-4V for bioapplication.

    PubMed

    Dahotre, Narendra B; Paital, Sameer R; Samant, Anoop N; Daniel, Claus

    2010-04-28

    Wettability at the surface of an implant material plays a key role in its success as it modulates the protein adsorption and thereby influences cell attachment and tissue integration at the interface. Hence, surface engineering of implantable materials to enhance wettability to physiological fluid under in vivo conditions is an area of active research. In light of this, in the present work, laser-based optical interference and direct melting techniques were used to develop synthetic microtextures on Ti-6Al-4V alloys, and their effects on wettability were studied systematically. Improved wettability to simulated body fluid and distilled water was observed for Ca-P coatings obtained by direct melting technique. This superior wettability was attributed to both the appropriate surface chemistry and the three-dimensional surface features obtained using this technique. To assert a better control on surface texture and wettability, a three-dimensional thermal model based on COMSOL's multiphysics was employed to predict the features obtained by laser melting technique. The effect of physical texture and wetting on biocompatibility of laser-processed Ca-P coatings was evaluated in the preliminary efforts on culturing of mouse MC3T3-E1 osteoblast cells.

  8. Synthesis and In vitro Evaluation of Electrodeposited Barium Titanate Coating on Ti6Al4V

    PubMed Central

    Rahmati, Shahram; Basiriani, Mohammad Basir; Rafienia, Mohammad; Yaghini, Jaber; Raeisi, Keyvan

    2016-01-01

    Osseointegration has been the concern of implantology for many years. Researchers have used various ceramic coatings for this purpose; however, piezoelectric ceramics (e.g., barium titanate [BTO]) are a novel field of interest. In this regard, BTO (BaTiO3) coating was fabricated by electrophoretic deposition on Ti6Al4V medical alloy, using sol-gel-synthesized nanometer BTO powder. Structure and morphologies were studied using X-ray diffraction and scanning electron microscopy (SEM), respectively. Bioactivity response of coated samples was evaluated by SEM and inductively coupled plasma (ICP) analysis after immersion in simulated body fluid (SBF). Cell compatibility was also studied via MTT assay and SEM imaging. Results showed homogenous coating with cubic structure and crystallite size of about 41 nm. SEM images indicated apatite formation on the coating after 7 days of SBF immersion, and ICP analysis approved ions concentration decrement in SBF. Cells showed flattened morphology in intimate contact with coating after 7 days of culture. Altogether, coated samples demonstrated appropriate bioactivity and biocompatibility. PMID:27186538

  9. New Strategies For Hole Making In Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Urbicain, G.; Olvera, D.; de Lacalle, L. N. López; Zamakona, I.; Rodal, P.

    2009-11-01

    The working conditions for the aircraft engines components demand a good response of their mechanical properties at high temperatures and aggressive environments. Those challenging conditions force the use of new materials like titanium (and nickel) based alloys, qualified as difficult-to-cut materials due to their low machinability. Among them, the Ti-6Al-4V is very widespread because of its high strength/weight ratio. On the other hand, a very demand task for aeronautical components is the hole making operation, being in most cases, the last performed operation. For this reason, drilling operation is strongly related to the quality and productivity since any machining error could damage the component in the final steps. Thus, drilling operation determines the minimum machining time which is reflected upon the cost per unit. This study focuses the attention on a relative new technique that could replace the conventional drilling resulting in a more added-value operation: ball helical milling (BHM). This new technique and a modified version (CBHM) were compared with a common drilling operation.

  10. Surface Deformation Behavior of BSTOA Ti-6Al-4V during Laser Shock Processing

    SciTech Connect

    El-Dasher, B S; Zaleski, T M; Gray, J J; Rybak, S J; Chen, H

    2005-07-21

    The surface of a beta solution treated and overaged (BSTOA) Ti-6Al-4V alloy specimen deformed by laser shock processing was studied using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Slip steps were observed within grains oriented with their c-axis nearly parallel to the specimen surface normal. Based on the slip step traces and orientation information, the slip planes were determined to be (11{bar 2}2) for grains with their c-axis within 15{sup o} of the specimen surface normal and (11{bar 2}1) for grains with their c-axis between 15{sup o} and 40{sup o} away from the specimen surface normal. Although both these planes are known to belong to twinning systems, (11{bar 2}2)<11{bar 2}{bar 3}> and (11{bar 2}1)<11{bar 2}{bar 6}> respectively, the latter has not been observed to operate as a slip system. Examination of the Taylor factors associated with these slip systems shows that the grains with slip steps have the lowest Taylor factors. Determination of localized lattice rotations showed a unique behavior in grains with slip steps, such that all the lattice rotations were concentrated about the steps, with almost no orientation variations in between slip steps. This distribution indicates that stress concentrations exist at the slip steps, which could potentially affect the performance of the material.

  11. Wetting behaviour of femtosecond laser textured Ti-6Al-4V surfaces

    NASA Astrophysics Data System (ADS)

    Cunha, Alexandre; Serro, Ana Paula; Oliveira, Vitor; Almeida, Amélia; Vilar, Rui; Durrieu, Marie-Christine

    2013-01-01

    The aim of the present work was to investigate the wetting behaviour of biomedical grade Ti-6Al-4V alloy surfaces textured by a femtosecond laser treatment. The material was treated in ambient atmosphere using an Yb: KYW chirped-pulse-regenerative amplification laser with a wavelength of 1030 nm and a pulse duration of 500 fs. Four main types of surface textures were obtained depending on the processing parameters and laser treatment method. These textures consist of: (1) nanoscale laser-induced periodic surface structures (LIPSS); (2) nanopillars; (3) a bimodal roughness distribution texture formed of LIPSS overlapping microcolumns; (4) a complex texture formed of LIPSS overlapping microcolumns with a periodic variation of the columns size in the laser scanning direction. The wettability of the surfaces was evaluated by the sessile drop method using distilled-deionized (DD) water and Hank's balanced salt solution (HBSS) as testing liquids. The laser treated surfaces present a hydrophilic behaviour as well as a high affinity for the saline solution, with equilibrium contact angles in the ranges 24.1-76.2° for DD water and 8.4-61.8° for HBSS. The wetting behaviour is anisotropic, reflecting the anisotropy of the surface textures.

  12. Texture Evolution During Laser Direct Metal Deposition of Ti-6Al-4V

    DOE PAGES

    Sridharan, Niyanth; Chaudhary, Anil; Nandwana, Peeyush; Babu, Sudarsanam Suresh

    2016-01-20

    Titanium alloys are used in a wide variety of high performance applications and hence the processing of the titanium and the resulting microstructures after additive manufacturing has received significant attention. During additive manufacturing the processing route involves the transition from a liquid to solid state. The addition of successive layers results in a complex microstructure due to solid-state transformations. The current study focuses on understanding the phase transformations and relate it to the transformation texture in Ti-6Al-4V to identify conditions leading to a strong alpha transformation texture. The as deposited builds were characterized using optical microscopy and electron backscattered diffraction.more » The results showed columnar prior β grains with a martensitic structure after the deposition of a single layer. On subsequent depositions the martensitic microstructure decomposes to a colony and basketweave microstructure with a stronger transformation texture. The alpha texture with a colony and basketweave microstructure shows a stronger transformation texture as a result of variant selection. Thus by controlling the cooling rate of the build from the β transus it is possible to control the alpha transformation texture.« less

  13. Modelling and simulation of effect of ultrasonic vibrations on machining of Ti6Al4V.

    PubMed

    Patil, Sandip; Joshi, Shashikant; Tewari, Asim; Joshi, Suhas S

    2014-02-01

    The titanium alloys cause high machining heat generation and consequent rapid wear of cutting tool edges during machining. The ultrasonic assisted turning (UAT) has been found to be very effective in machining of various materials; especially in the machining of "difficult-to-cut" material like Ti6Al4V. The present work is a comprehensive study involving 2D FE transient simulation of UAT in DEFORM framework and their experimental characterization. The simulation shows that UAT reduces the stress level on cutting tool during machining as compared to that of in continuous turning (CT) barring the penetration stage, wherein both tools are subjected to identical stress levels. There is a 40-45% reduction in cutting forces and about 48% reduction in cutting temperature in UAT over that of in CT. However, the reduction magnitude reduces with an increase in the cutting speed. The experimental analysis of UAT process shows that the surface roughness in UAT is lower than in CT, and the UATed surfaces have matte finish as against the glossy finish on the CTed surfaces. Microstructural observations of the chips and machined surfaces in both processes reveal that the intensity of thermal softening and shear band formation is reduced in UAT over that of in CT.

  14. Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding

    NASA Technical Reports Server (NTRS)

    Palmieri, Frank L.; Watson, Kent A.; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J.; Hopkins, John W.; Connell, John W.

    2012-01-01

    Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability.

  15. Synthesis and In vitro Evaluation of Electrodeposited Barium Titanate Coating on Ti6Al4V.

    PubMed

    Rahmati, Shahram; Basiriani, Mohammad Basir; Rafienia, Mohammad; Yaghini, Jaber; Raeisi, Keyvan

    2016-01-01

    Osseointegration has been the concern of implantology for many years. Researchers have used various ceramic coatings for this purpose; however, piezoelectric ceramics (e.g., barium titanate [BTO]) are a novel field of interest. In this regard, BTO (BaTiO3) coating was fabricated by electrophoretic deposition on Ti6Al4V medical alloy, using sol-gel-synthesized nanometer BTO powder. Structure and morphologies were studied using X-ray diffraction and scanning electron microscopy (SEM), respectively. Bioactivity response of coated samples was evaluated by SEM and inductively coupled plasma (ICP) analysis after immersion in simulated body fluid (SBF). Cell compatibility was also studied via MTT assay and SEM imaging. Results showed homogenous coating with cubic structure and crystallite size of about 41 nm. SEM images indicated apatite formation on the coating after 7 days of SBF immersion, and ICP analysis approved ions concentration decrement in SBF. Cells showed flattened morphology in intimate contact with coating after 7 days of culture. Altogether, coated samples demonstrated appropriate bioactivity and biocompatibility. PMID:27186538

  16. Aquatic assessment of the Ely Copper Mine Superfund site, Vershire, Vermont

    USGS Publications Warehouse

    Seal, Robert R., II; Kiah, Richard G.; Piatak, Nadine M.; Besser, John M.; Coles, James F.; Hammarstrom, Jane M.; Argue, Denise M.; Levitan, Denise M.; Deacon, Jeffrey R.; Ingersoll, Christopher G.

    2010-01-01

    The information was used to develop an overall assessment of the impact on the aquatic system that appears to be a result of the acid rock drainage at the Ely Mine. More than 700 meters of Ely Brook, including two of the six ponds, were found to be severely impacted, on the basis of water-quality data and biological assessments. The reference location was of good quality based on the water quality and biological assessment. More than 3,125 meters of Schoolhouse Brook are also severely impacted, on the basis of water-quality data and biological assessments. The biological community begins to recover near the conflu

  17. Plasma-sprayed CaTiSiO5 ceramic coating on Ti-6Al-4V with excellent bonding strength, stability and cellular bioactivity

    PubMed Central

    Wu, Chengtie; Ramaswamy, Yogambha; Liu, Xuanyong; Wang, Guocheng; Zreiqat, Hala

    2008-01-01

    Novel Ca-Si-Ti-based sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study was to prepare sphene coating on titanium alloy (Ti-6Al-4V) for orthopaedic applications using the plasma spray method. The phase composition, surface and interface microstructure, coating thickness, surface roughness and bonding strength of the plasma-sprayed sphene coating were analysed using X-ray diffraction, scanning electron microscopy, atomic force microscopy and the standard mechanical testing of the American Society for Testing and Materials, respectively. The results indicated that sphene coating was obtained with a uniform and dense microstructure at the interface of the Ti-6Al-4V surface and the thickness and surface roughness of the coating were approximately 150 and 10 μm, respectively. Plasma-sprayed sphene coating on Ti-6Al-4V possessed a significantly improved bonding strength and chemical stability compared with plasma-sprayed hydroxyapatite (HAp) coating. Plasma-sprayed sphene coating supported human osteoblast-like cell (HOB) attachment and significantly enhanced HOB proliferation and differentiation compared with plasma-sprayed HAp coating and uncoated Ti-6Al-4V. Taken together, plasma-sprayed sphene coating on Ti-6Al-4V possessed excellent bonding strength, chemical stability and cellular bioactivity, indicating its potential application for orthopaedic implants. PMID:18664431

  18. Plasma-sprayed CaTiSiO5 ceramic coating on Ti-6Al-4V with excellent bonding strength, stability and cellular bioactivity.

    PubMed

    Wu, Chengtie; Ramaswamy, Yogambha; Liu, Xuanyong; Wang, Guocheng; Zreiqat, Hala

    2009-02-01

    Novel Ca-Si-Ti-based sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study was to prepare sphene coating on titanium alloy (Ti-6Al-4V) for orthopaedic applications using the plasma spray method. The phase composition, surface and interface microstructure, coating thickness, surface roughness and bonding strength of the plasma-sprayed sphene coating were analysed using X-ray diffraction, scanning electron microscopy, atomic force microscopy and the standard mechanical testing of the American Society for Testing and Materials, respectively. The results indicated that sphene coating was obtained with a uniform and dense microstructure at the interface of the Ti-6Al-4V surface and the thickness and surface roughness of the coating were approximately 150 and 10 microm, respectively. Plasma-sprayed sphene coating on Ti-6Al-4V possessed a significantly improved bonding strength and chemical stability compared with plasma-sprayed hydroxyapatite (HAp) coating. Plasma-sprayed sphene coating supported human osteoblast-like cell (HOB) attachment and significantly enhanced HOB proliferation and differentiation compared with plasma-sprayed HAp coating and uncoated Ti-6Al-4V. Taken together, plasma-sprayed sphene coating on Ti-6Al-4V possessed excellent bonding strength, chemical stability and cellular bioactivity, indicating its potential application for orthopaedic implants.

  19. A Comparison Between Mechanical And Electrochemical Tests on Ti6Al4V Welded By LBW

    NASA Astrophysics Data System (ADS)

    Serroni, G.; Bitondo, C.; Astarita, A.; Scala, A.; Gloria, A.; Prisco, U.; Squillace, A.; Bellucci, F.

    2011-05-01

    Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). To this aim, lots of researches are now focusing on new and emerging technologies capable to make titanium objects and, at the same time, reducing the scrap, since titanium alloys for aeronautic application are very expensive. This paper examines Grade 5 Titanium Alloy (Ti6Al4V) welded by Laser Beam (LBW) in butt-joint configuration. The source was Nd:YAG laser, moreover two inert gases were used, in order to provide a shield both on the top and on the bottom of the weld bead. The joints were studied by varying two process parameters: welding speed and power of the laser beam. It was not possible to realize a full experimental plan, due to technological limits in making titanium laser beam welds. The joints were tested to measure their mechanical properties and the corrosion resistance. The process parameters do not significantly affect the maximum static strength of the joints. Microscopic analysis showed that welds made with high power and low welding speed have a uniform weld bead, and no macroscopic defect occurs. Fatigue test results, instead, show a marked influence of the morphology of the weld bead: the occurrence of some defects, such as the undercut, both on the top and on the bottom of the weld bead, dramatically reduced fatigue resistance of the joints. Corrosion resistance was studied using the electrochemical micro cell technique, which allows to distinguish electrochemical properties of each zone of the weld bead, even when, as in this case, they are very narrow. By a general point of view, it has been demonstrated that the joints showing the best

  20. [Validation of the Essen Quality of Life-Index for Eating Disorders (ELI)].

    PubMed

    Tagay, Sefik; Lindner, Marion; Friederich, Hans-Christoph; Schlottbohm, Ellen

    2015-09-01

    The aim of this study was the validation of a short disease-specific questionnaire (ELI, Essen Quality of Life Index for Eating Disorders) to measure the health-related quality of life in patients with eating disorders. A total of 182 currently ill and former eating disordered patients and 87 healthy controls completed the ELI questionnaire as well as other reliable and valid instruments (EDQOL, SF-12, EDI-2, FKB-20, SEED, BSI, IIP-D and SOC-13). In addition, 46 eating disorder patients completed the same questionnaires at the end of therapy. The ELI proved to have a high internal consistency of α=0.96. As expected, one main factor was found with a high declaration of variance of 71.25%. There is also evidence for very good construct validity and good sensitivity for change. Therefore, the ELI is an economic, reliable and valid instrument that assesses disease-specific health-related quality of life of individuals with eating disorders. The questionnaire can be recommended for research as well as clinical care contexts.

  1. 78 FR 21849 - Television Broadcasting Services; Ely, NV to Middletown Township, NJ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-12

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 Television Broadcasting Services; Ely, NV to Middletown Township, NJ AGENCY... U.S.C. 801(a)(1)(A). List of Subjects in 47 CFR Part 73 Television. Federal...

  2. 75 FR 81190 - Television Broadcasting Services; Vernal and Santaquin, UT, and Ely and Caliente, NV

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-27

    ... COMMISSION 47 CFR Part 73 Television Broadcasting Services; Vernal and Santaquin, UT, and Ely and Caliente.... The Commission was required by the DTV Delay Act to ] terminate all licenses for full-power television... Commission no longer has the authority to act on rulemaking proposals in the full-power analog...

  3. Aquatic assessment of the Ely Copper Mine Superfund site, Vershire, Vermont

    USGS Publications Warehouse

    Seal, Robert R., II; Kiah, Richard G.; Piatak, Nadine M.; Besser, John M.; Coles, James F.; Hammarstrom, Jane M.; Argue, Denise M.; Levitan, Denise M.; Deacon, Jeffrey R.; Ingersoll, Christopher G.

    2010-01-01

    The information was used to develop an overall assessment of the impact on the aquatic system that appears to be a result of the acid rock drainage at the Ely Mine. More than 700 meters of Ely Brook, including two of the six ponds, were found to be severely impacted, on the basis of water-quality data and biological assessments. The reference location was of good quality based on the water quality and biological assessment. More than 3,125 meters of Schoolhouse Brook are also severely impacted, on the basis of water-quality data and biological assessments. The biological community begins to recover near the confluence with the Ompompanoosuc River. The evidence is less conclusive regarding the Ompompanoosuc River. The sediment data suggest that the sediments could be a source of toxicity in Ely Brook and Schoolhouse Brook. The surface-water assessment is consistent with the outcome of a surface-water toxicity testing program performed by the U.S. Environmental Protection Agency for Ely Brook and Schoolhouse Brook and a surface-water toxicity testing program and in situ amphibian testing program for the ponds.

  4. Surface morphology of nanotube formed Ti alloy by electrochemical methods.

    PubMed

    Kim, Sung-Hwan; Choe, Han-Cheol

    2014-11-01

    In order to investigate the surface morphology of nanotube formed Ti alloy by electrochemical methods, the Ti-6Al-4V alloys for dental implant were used in this study. Heat treatment was carried out at 800 degrees C for 1 hour and then water quenching in argon atmosphere, that will be have a specimen name of 800 WQ. The formation of nanotube structure was conducted by electrochemical method on Ti-6Al-4V alloy in mixed electrolytes at 30 V for 1 hour. Microstructure of β phases showed dot-like structures at non-treated Ti-6Al-4V alloy, and needle-like in equiaxed structure from treated the alloy at 800 WQ. In non-treated Ti-6Al-4V alloy case, nanotubes only exhibited at α phase region with dissolved V-oxide area of β phase. However, in the case of 800 WQ, nanotubes of Ti-6Al-4V alloy exhibited at both α and βphase region. Electrochemical corrosion studies showed that the nanotubular alloy of 800 WQ possesses slightly higher corrosion resistance than that of non-treated nanotubular alloy. PMID:25958530

  5. Influence of Laser Power on the Hardening of Ti6Al4V Low-Pressure Steam Turbine Blade Material for Enhancing Water Droplet Erosion Resistance

    NASA Astrophysics Data System (ADS)

    Mann, B. S.; Arya, Vivek; Pant, B. K.

    2011-03-01

    To overcome water droplet erosion of Ti6Al4V alloy blade material used in low-pressure steam turbine (LPST) of high-rating nuclear and super critical thermal power plants, high-power diode laser (HPDL) surface treatment at two temperatures corresponding to two different power levels was carried out. During incubation as well as under prolonged erosion testing, the HPDL surface treatment of this alloy has enhanced its resistance significantly. This is due to the formation of fine-grained martensitic (ά) phase due to rapid heating and cooling associated with laser treatment. The droplet erosion test results after HPDL surface treatment on this alloy, SEM, XRD analysis, and residual stresses developed due to HPDL surface treatment are given in this paper.

  6. Fixation of bioactive calcium alkali phosphate on Ti6Al4V implant material with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Symietz, Christian; Lehmann, Erhard; Gildenhaar, Renate; Koter, Robert; Berger, Georg; Krüger, Jörg

    2011-04-01

    Bone implants made of metal, often titanium or the titanium alloy Ti6Al4V, need to be surface treated to become bioactive. This enables the formation of a firm and durable connection of the prosthesis with the living bone. We present a new method to uniformly cover Ti6Al4V with a thin layer of ceramics that imitates bone material. These calcium alkali phosphates, called GB14 and Ca10, are applied to the metal by dip coating of metal plates into an aqueous slurry containing the fine ceramic powder. The dried samples are illuminated with the 790 nm radiation of a pulsed femtosecond laser. If the laser fluence is set to a value just below the ablation threshold of the ceramic (ca. 0.4 J/cm 2) the 30 fs laser pulses penetrate the partly transparent ceramic layer of 20-40 μm thickness. The remaining laser fluence at the ceramic-metal interface is still high enough to generate a thin metal melt layer leading to the ceramic fixation on the metal. The laser processing step is only possible because Ti6Al4V has a lower ablation threshold (between 0.1 and 0.15 J/cm 2) than the ceramic material. After laser treatment in a fluence range between 0.1 and 0.4 J/cm 2, only the particles in contact with the metal withstand a post-laser treatment (ultrasonic cleaning). The non-irradiated rest of the layer is washed off. In this work, we present results of a successful ceramic fixation extending over larger areas. This is fundamental for future applications of arbitrarily shaped implants.

  7. Laser deposited biocompatible Ca-P coatings on Ti-6Al-4V: microstructural evolution and thermal modeling.

    PubMed

    Nag, Soumya; Paital, Sameer R; Nandawana, Peeyush; Mahdak, Kristopher; Ho, Yee Hsien; Vora, Hitesh D; Banerjee, Rajarshi; Dahotre, Narendra B

    2013-01-01

    A high intensity continuous wave diode pumped ytterbium laser source was used to deposit Ca-P coatings on a Ti-6Al-4V biocompatible alloy in order to generate a physically textured surface, enhancing osseointegration. Scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) studies were coupled with X-ray and micro diffraction work to determine the structure, composition, and phases present in various zones of a sample prepared across the coating/substrate interaction zone. Three-dimensional thermal modeling was also carried out to determine the cooling rate and maximum temperature experienced by different regions of the substrate. Combining these results provide us with valuable insights regarding the thermo-physical as well as chemical interactions that take place across the coating-substrate interface.

  8. Parametric optimization of selective laser melting for forming Ti6Al4V samples by Taguchi method

    NASA Astrophysics Data System (ADS)

    Sun, Jianfeng; Yang, Yongqiang; Wang, Di

    2013-07-01

    In this study, a selective laser melting experiment was carried out with Ti6Al4V alloy powders. To produce samples with maximum density, selective laser melting parameters of laser power, scanning speed, powder thickness, hatching space and scanning strategy were carefully selected. As a statistical design of experimental technique, the Taguchi method was used to optimize the selected parameters. The results were analyzed using analyses of variance (ANOVA) and the signal-to-noise (S/N) ratios by design-expert software for the optimal parameters, and a regression model was established. The regression equation revealed a linear relationship among the density, laser power, scanning speed, powder thickness and scanning strategy. From the experiments, sample with density higher than 95% was obtained. The microstructure of obtained sample was mainly composed of acicular martensite, α phase and β phase. The micro-hardness was 492 HV0.2.

  9. Surface Residual Stresses in Ti-6Al-4V Friction Stir Welds: Pre- and Post-Thermal Stress Relief

    NASA Astrophysics Data System (ADS)

    Edwards, P.; Ramulu, M.

    2015-09-01

    The purpose of this study was to determine the residual stresses present in titanium friction stir welds and if a post-weld thermal stress relief cycle would be effective in minimizing those weld-induced residual stresses. Surface residual stresses in titanium 6Al-4V alloy friction stir welds were measured in butt joint thicknesses ranging from 3 to 12 mm. The residual stress states were also evaluated after the welds were subjected to a post-weld thermal stress relief cycle of 760 °C for 45 min. High (300-400 MPa) tensile residual stresses were observed in the longitudinal direction prior to stress relief and compressive residual stresses were measured in the transverse direction. After stress relief, the residual stresses were decreased by an order of magnitude to negligible levels.

  10. On the Use of Infrared Thermography for Analysis of Fatigue Damage in Ti6Al4V-Welded Joints

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Gao, Xiao-Long; Zhang, Lin-Jie; Zhang, Jian-Xun

    2014-08-01

    The present work is aimed at comparatively studying fatigue damage evolution of a pulsed Nd:YAG laser beam-welded (LBW) joint and the base metal (BM) of Ti6Al4V alloy subjected to cyclic loading. To reveal crack nucleation and propagation during the fatigue process, in situ fatigue was generated using infrared measurement methods. The results indicate that the rate of damage accumulated in the LBW joint was higher than in the BM specimens during a fatigue test, which decreased the fatigue life of the LBW joint. This observation is attributable to the LBW joint fusion zone microstructure, which has a higher void nucleation and growth rate compared with the BM microstructure.

  11. Experimental analysis of selective laser melting process for Ti-6Al-4V turbine blade manufacturing

    NASA Astrophysics Data System (ADS)

    Caiazzo, Fabrizia; Cardaropoli, Francesco; Alfieri, Vittorio; Sergi, Vincenzo; Cuccaro, Luigi

    2012-01-01

    The present work focuses on the use of Selective Laser Melting (SLM) technique for manufacturing of near-net-shape aircraft component prototypes with Ti-6Al-4V titanium alloy, which has already successfully employed for the production of turbine blades since it combines mechanical properties with excellent wear resistance. The main characteristic of SLM is layer manufacturing which allows to obtain complex shaped elements using three dimensional computer aided design data, with the addition of particular features like channels or cavities which can not been easily obtained with traditional technologies. The other key aspect in comparison with investment casting is shorter post-processing. The feasibility of manufacturing turbine blades with mentioned process using a laser sintered machine EOSINT M 270 (Titanium version) is analysed. The first experimental phase has dealt with the definition of processing parameters which would guarantee laser sintered part maximum density. Preliminary specimens have been manufactured to define any material-dependent scaling value to control dimensional shrinkage. Afterwards a prototype of a turbine blade has been produced using optimal process parameter set. The element positioning and support definition are discussed as they influence the overall job time and the need of post processing operations. Further analyses have been carried out to check the whole structure of the prototype using X-rays and Fluorescent Penetrant Inspection, aiming to point out possible imperfections; no defects have been detected. Furthermore, laser sintered part dimensional inspection has been successively performed via coordinate measuring machine. Eventually, the microstructure of the prototype has been examined.

  12. Friction and wear of titanium alloys and copper alloys sliding against titanium 6-percent-aluminum - 4-percent-vanadium alloy in air at 430 C

    NASA Technical Reports Server (NTRS)

    Wisander, D. W.

    1976-01-01

    Experiments were conducted to determine the friction and wear characteristics of aluminum bronzes and copper-tin, titanium-tin, and copper-silver alloys sliding against a titanium-6% aluminum-4% vanadium alloy (Ti-6Al-4V). Hemispherically tipped riders of aluminum bronze and the titanium and copper alloys were run against Ti-6Al-4V disks in air at 430 C. The sliding velocity was 13 cm/sec, and the load was 250 g. Results revealed that high tin content titanium and copper alloys underwent significantly less wear and galling than commonly used aluminum bronzes. Also friction force was less erratic than with the aluminum bronzes.

  13. The effect of thermal cycling on the shear bond strength of porcelain/Ti-6Al-4V interfaces.

    PubMed

    Sendão, Isabel A; Alves, Alexandra C; Galo, Rodrigo; Toptan, Fatih; Silva, Filipe S; Ariza, Edith

    2015-04-01

    The aim of the study was to evaluate the effect of thermal cycling on the shear bond strength of the porcelain/Ti-6Al-4V interfaces prepared by two different processing routes and metallic surface conditions. Polished and SiO2 particle abraded Ti-6Al-4V alloy and Triceram bonder porcelain were used to produce the interfaces. Porcelain-to-metal specimens were processed by conventional furnace firing and hot pressing. Thermal cycling was performed in Fusayama's artificial saliva for 5000 cycles between 5 ± 1 and 60 ± 2°C. After thermal cycling, shear bond tests were carried out by using a custom-made stainless steel apparatus. The results were analyzed using t-Student test and non-parametric Kruskal-Wallis test (p<0.01). Most of the polished-fired specimens were fractured during thermal cycling; thus, it was not possible to obtain the shear bond strength results for this group. Sandblasted-fired, polished-hot pressed, and sandblasted-hot pressed specimens presented the shear bond strength values of 76.2 ± 15.9, 52.2 ± 23.6, and 59.9 ± 22.0 MPa, respectively. Statistical analysis indicated that thermal cycling affected the polished specimens processed by firing, whereas a significant difference was not observed on the other groups.

  14. Review of Mechanical Properties of Ti-6Al-4V Made by Laser-Based Additive Manufacturing Using Powder Feedstock

    NASA Astrophysics Data System (ADS)

    Beese, Allison M.; Carroll, Beth E.

    2016-03-01

    Laser-based additive manufacturing (AM) of metals using powder feedstock can be accomplished via two broadly defined technologies: directed energy deposition (DED) and powder bed fusion (PBF). In these processes, metallic powder is delivered to a location and locally melted with a laser heat source. Upon deposition, the material undergoes a rapid cooling and solidification, and as subsequent layers are added to the component, the material within the component is subjected to rapid thermal cycles. In order to adopt AM for the building of structural components, a thorough understanding of the relationships among the complex thermal cycles seen in AM, the unique heterogeneous and anisotropic microstructure, and the mechanical properties must be developed. Researchers have fabricated components by both DED and PBF from the widely used titanium alloy Ti-6Al-4V and studied the resultant microstructure and mechanical properties. This review article discusses the progress to date on investigating the as-deposited and heat-treated microstructures and mechanical properties of Ti-6Al-4V structures made by powder-based laser AM using DED and PBF.

  15. The elevated-temperature mechanical behavior of as-cast and wrought Ti-6Al-4V-1B

    SciTech Connect

    Chen, Wei; Boehlert, C. J.; Howe, Jane Y; Payzant, E Andrew

    2011-01-01

    This work studied the effect of processing on the elevated-temperature [728 K (455 C)] fatigue deformation behavior of Ti-6Al-4V-1B for maximum applied stresses between 300 to 700 MPa (R = 0.1, 5 Hz). The alloy was evaluated in the as-cast form as well as in three wrought forms: cast-and-extruded, powder metallurgy (PM) rolled, and PM extruded. Processing caused significant differences in the microstructure, which in turn impacted the fatigue properties. The PM-extruded material exhibited a fine equiaxed {alpha} + {beta} microstructure and the greatest fatigue resistance among all the studied materials. The {beta}-phase field extrusion followed by cooling resulted in a strong {alpha}-phase texture in which the basal plane was predominately oriented perpendicular to the extrusion axis. The TiB whiskers were also aligned in the extrusion direction. The {alpha}-phase texture in the extrusions resulted in tensile-strength anisotropy. The tensile strength in the transverse orientation was lower than that in the longitudinal orientation, but the strength in the transverse orientation remained greater than that for the as-cast Ti-6Al-4V. The ratcheting behavior during fatigue is also discussed.

  16. Influence of oxidative nanopatterning and anodization on the fatigue resistance of commercially pure titanium and Ti-6Al-4V.

    PubMed

    Ketabchi, Amirhossein; Weck, Arnaud; Variola, Fabio

    2015-04-01

    With an increasingly aging population, a significant challenge in implantology is the creation of biomaterials that actively promote tissue integration and offer excellent mechanical properties. Engineered surfaces with micro- and nanoscale topographies have shown great potential to control and direct biomaterial-host tissue interactions. Two simple yet efficient chemical treatments, oxidative nanopatterning and anodization, have demonstrated the ability to confer exciting new bioactive capacities to commercially pure titanium and Ti-6Al-4V alloy. However, the resulting nanoporous and nanotubular surfaces require careful assessment in regard to potential adverse effects on the fatigue resistance, a factor which may ultimately cause premature failure of biomedical implants. In this work, we have investigated the impact of oxidative nanopatterning and anodization on the fatigue resistance of commercially pure titanium and Ti-6Al-4V. Quantitative (e.g., S-N curves) and qualitative analyses were carried out to precisely characterize the fatigue response of treated metals and compare it to that of polished controls. Scanning electron microscopy (SEM) imaging revealed the effects of cyclic loading on the fracture surface and on the structural integrity of chemically grown nanostructured oxides. Results from this study reinforce the importance of mechanical considerations in the development and optimization of micro- and nanoscale surface treatments for metallic biomedical implants.

  17. Numerical and experimental study of the Ti6Al4V macrostructure obtained by Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Conde, J. C.; Paz, M. D.; Serra, J.; González, P.

    2014-04-01

    Titanium and its alloys (Ti6Al4V) have been widely used in the biomedical field; nevertheless, they should be subject to specific surface treatments, before being implanted, in order to improve bio-integration. Although laser processing is a useful technique for this purpose, different aspects of the basic mechanisms of this process are still in progress, with special emphasis on the modeling structure formation on the irradiated surface. For this research, the finite element method was used to study the generation of a macrostructure on the Ti6Al4V surface using a Nd:YAG laser. The temperature profiles, estimated during the extremely high heating and cooling rates caused by the output power of the laser beam, allowed us to analyze, among other things, the melting depth and the heat affected zone, in order to optimize the process. Moreover, the experimental results (SEM data) were positively compared with the numerical model, and a relationship of the crater profile formation (depth to width ratio) was determined.

  18. Effect of Heat Input on the Tensile Damage Evolution in Pulsed Laser Welded Ti6Al4V Titanium Sheets

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Gao, Xiaolong; Zhang, Jianxun

    2016-10-01

    The present paper is focused on studying the effect of heat input on the tensile damage evolution of pulsed Nd:YAG laser welding of Ti6Al4V alloy under monotonic loading. To analyze the reasons that the tensile fracture site of the pulsed-laser-welded Ti6Al4V sheet joints changes with the heat input under monotonic loading, the microstructure of the sample with different nominal strain values was investigated by in situ observation. Experiment results show that the tensile ductility and fatigue life of welded joints with low heat input are higher than that of welded joints with high heat input. Under tensile loads, the critical engineering strain for crack initiation is much lower in the welded joint with high heat input than in the welded joints with low and medium heat input. And the microstructural damage accumulation is much faster in the fusion zone than in the base metal for the welded joints with high input, whereas the microstructural damage accumulation is much faster in the base metal than in the fusion zone for the welded joints with low input. Consequently, the welded joints fractured in the fusion zone for the welds with high heat input, whereas the welded joints ruptured in the base metal for the welds with low heat input. It is proved that the fine grain microstructure produced by low heat input can improve the critical nominal strain for crack initiation and the resistance ability of microstructural damage.

  19. Fracture characteristics of Ti-6Al-4V and Ti-5Al-2.5Fe with refined microstructure using hydrogen

    NASA Astrophysics Data System (ADS)

    Niinomi, M.; Gong, B.; Kobayashi, T.; Ohyabu, Y.; Toriyama, O.

    1995-05-01

    The hydrogenation behavior of Ti-6Al-4V, with the starting microstructures of coarse equiaxed α and coarse Widmanstätten α, respectively, was investigated under a hydrogen pressure of 0.1 MPa at temperatures between 843 and 1123 K. The hydrogen content was determined as a function of hydrogenation time, hydrogenation temperature, and hydrogen flow rate. The phases presented in the alloy of after hydrogenation were determined with X-ray and electron diffraction analysis in order to define the effect of Thermochemical Processing (TCP) on the microstructure of the alloy. Mechanical properties and fracture toughness of Ti-6Al-4V and Ti-5Al-2.5Fe subjected to the various TCP were then investigated. Hydrogenation of Ti-6Al-4V with the starting microstructure of coarse equiaxed α at 1023 K, just below hydrogen saturated β (denoted β″ (H)) transus temperature, produces a microstructure of a, orthohombic martensite (denoted α″ (H)) and β (H). Hydrogenation at 1123 K, above β (H) transus, results in a microstructure of α″ (H) and β (H). Microstructure refinement during TCP results mainly from decomposition of α″ (H) and ;β (H) into a fine mixture of α + β during dehydrogenation. An alternative TCP method is below β (H) transus hydrogenation (BTH), consisting of hydrogenation of the alloy below the hydrogenated β (H) transus temperature, air cooling to room temperature, and dehydrogenation at a lower temperature, which is found to improve mechanical properties significantly over a conventional TCP treatment. Compared with the untreated material, the BTH treatment increases the yield strength and increases the ultimate tensile strength significantly without decreasing the tensile elongation in the starting microstructure of coarse equiaxed α or with a little decrease in the tensile elongation in the starting microstructure of coarse Widmanstätten α, although the conventional TCP treatment results in a large decrease in elongation over the

  20. In vitro assessment of the biological response of Ti6Al4V implants coated with hydroxyapatite microdomains.

    PubMed

    Clavell, R Salvador; de Llano, J J Martín; Carda, C; Ribelles, J L Gómez; Vallés-Lluch, A

    2016-11-01

    Dental implantology is still an expanding field of scientific study because of the number of people that receive dental therapies throughout their lives worldwide. Recovery times associated to dental surgery are still long and demand strategies to improve integration of metallic devices with hard tissues. In this work, an in vitro ceramic coating is proposed to improve and accelerate osseointegration of titanium surfaces conceived to be used as dental implants or hip or knee prosthesis, shaped either as dishes or screws. Such coating consists of hydroxyapatite microdomains on the implant surfaces obtained in vitro by immersion of titanium alloy samples (Ti6Al4V) in a simulated body fluid. This titanium alloy is highly used in implant dentistry and trauma surgery, among other fields. Once the immersion times under physiological conditions yielding to different ceramic topographies on this alloy were set, the acellular coating time of major interest so as to optimize its biological development was determined. For this purpose, dental pulp mesenchymal cells were cultured on titanium coated surfaces with different hydroxyapatite outline, and cell adhesion, proliferation and morphology were followed through histological techniques and scanning electron microscopy. It was found that 4 days of acellular hydroxyapatite coating led to a significant cell adhesion on the titanium alloys at an early stage (6 h). Cells tended although to detach from the surface of the coating over time, but those adhered on domains of intricated topography or hydroxyapatite cauliflowers proliferated on them, leading to isolated large cell clusters. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2723-2729, 2016.

  1. Self-organized nanotubular oxide layers on Ti-6Al-7Nb and Ti-6Al-4V formed by anodization in NH4F solutions.

    PubMed

    Macak, Jan M; Tsuchiya, Hiroaki; Taveira, Luciano; Ghicov, Andrei; Schmuki, Patrik

    2005-12-15

    The present work reports the fabrication of self-organized porous oxide-nanotube layers on the biomedical titanium alloys Ti-6Al-7Nb and Ti-6Al-4V by a simple electrochemical treatment. These two-phase alloys were anodized in 1M (NH(4))(2)SO(4) electrolytes containing 0.5 wt % of NH(4)F. The results show that under specific anodization conditions self-organized porous oxide structures can be grown on the alloy surface. SEM images revealed that the porous layers consist of arrays of single nanotubes with a diameter of 100 nm and a spacing of 150 nm. For the V-containing alloy enhanced etching of the beta phase is observed, leading to selective dissolution and an inhomogeneous pore formation. For the Nb-containing alloy an almost ideal coverage of both phases is obtained. According to XPS measurements the tubes are a mixed oxide with an almost stoichiometric oxide composition, and can be grown to thicknesses of several hundreds of nanometers. These findings represent a simple surface treatment for Ti alloys that has high potential for biomedical applications.

  2. Direct space decomposition of ELI-D: interplay of charge density and pair-volume function for different bonding situations.

    PubMed

    Wagner, Frank R; Kohout, Miroslav; Grin, Yuri

    2008-10-01

    The topological features, i.e., gradients and curvatures of the same-spin electron pair restricted electron localizability indicator (ELI-D) in position space are analyzed in terms of those of the electron density and the pair-volume function. The analysis of the topology of these constituent functions and their interplay on ELI-D attractor formation for a number of molecules representing chemically different bonding situations allows distinguishing between different chemical bonding scenarios on a quantum mechanical basis without the recourse to orbitals. The occurrence of the Laplacian of the electron density in the expression for the Laplacian of ELI-D allows us to establish a physical link between electron localizability and electron pairing as displayed by ELI-D and the role of Laplacian of the density in this context.

  3. 6D phase space electron beam analysis and machine sensitivity studies for ELI-NP GBS

    NASA Astrophysics Data System (ADS)

    Giribono, A.; Bacci, A.; Curatolo, C.; Drebot, I.; Palumbo, L.; Petrillo, V.; Rossi, A. R.; Serafini, L.; Vaccarezza, C.; Vannozzi, A.; Variola, A.

    2016-09-01

    The ELI-NP Gamma Beam Source (GBS) is now under construction in Magurele-Bucharest (RO). Here an advanced source of gamma photons with unprecedented specifications of brilliance (>1021), monochromaticity (0.5%) and energy tunability (0.2-19.5 MeV) is being built, based on Inverse Compton Scattering in the head-on configuration between an electron beam of maximum energy 750 MeV and a high quality high power ps laser beam. These requirements make the ELI-NP GBS an advanced and challenging gamma ray source. The electron beam dynamics analysis and control regarding the machine sensitivity to the possible jitter and misalignments are presented. The effects on the beam quality are illustrated providing the basis for the alignment procedure and jitter tolerances.

  4. Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP

    NASA Astrophysics Data System (ADS)

    Negoita, F.; Gugiu, M.; Petrascu, H.; Petrone, C.; Pietreanu, D.; Fuchs, J.; Chen, S.; Higginson, D.; Vassura, L.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Antici, P.; Balabanski, D.; Balascuta, S.; Cernaianu, M.; Dancus, I.; Gales, S.; Neagu, L.; Petcu, C.; Risca, M.; Toma, M.; Turcu, E.; Ursescu, D.

    2015-02-01

    The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr3(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.

  5. Laser-based acceleration for nuclear physics experiments at ELI-NP

    NASA Astrophysics Data System (ADS)

    Tesileanu, O.; Asavei, Th.; Dancus, I.; Gales, S.; Negoita, F.; Turcu, I. C. E.; Ursescu, D.; Zamfir, N. V.

    2016-05-01

    As part of the Extreme Light pan-European research infrastructure, Extreme Light Infrastructure - Nuclear Physics (ELI-NP) in Romania will focus on topics in Nuclear Physics, fundamental Physics and applications, based on very intense photon beams. Laser-based acceleration of electrons, protons and heavy ions is a prerequisite for a multitude of laser-driven nuclear physics experiments already proposed by the international research community. A total of six outputs of the dual-amplification chain laser system, two of 100TW, two of 1PW and two of 10PW will be employed in 5 experimental areas, with the possibility to use long and short focal lengths, gas and solid targets, reaching the whole range of laser acceleration processes. We describe the main techniques and expectations regarding the acceleration of electrons, protons and heavy nuclei at ELI-NP, and some physics cases for which these techniques play an important role in the experiments.

  6. Geographic variation in the elicitin-like glycoprotein, ELI025, of Pythium insidiosum isolated from human and animal subjects.

    PubMed

    Lerksuthirat, Tassanee; Lohnoo, Tassanee; Rujirawat, Thidarat; Yingyong, Wanta; Jongruja, Nujarin; Krajaejun, Theerapong

    2015-10-01

    Oomycetes are fungus-like in appearance, but form a distinct clade within the eukaryotes. While most pathogenic oomycetes infect plants, the understudied oomycete Pythium insidiosum infects humans and animals, and causes a life-threatening infectious disease, called pythiosis. Phylogenetic analyses divide P. insidiosum into 3 groups, according to geographic origins: Clade-I (Americas), Clade-II (Asia and Australia), and Clade-III (Thailand). Surgical removal of the infected organ is the inevitable treatment for patients with pythiosis, but it is often too late or unsuccessful, and many patients die from advanced infection. Understanding P. insidiosum's basic biology could lead to improved infection control. Elicitins, a unique group of proteins found only in oomycetes, are involved in sterol acquisition and stimulation of host responses. Recently, we identified glycosylated and non-glycosylated forms of the elicitin-like protein, ELI025, which is secreted by P. insidiosum, and detected during P. insidiosum infection. In this study, we investigated geographic variation of ELI025 in 24 P. insidiosum strains isolated from humans, animals, and the environment. Genotypes of ELI025, based on 2 sets of PCR primers, correlated well with rDNA-based phylogenetic grouping. Unlike strains in Clade-I and -II, Clade-III strains secreted no glycosylated ELI025. Sera from 17 pythiosis patients yielded a broad range of antibody responses against ELI025, and ∼30% lacked reactivity against the protein. Selective production or secretion of glycosylated ELI025 by different P. insidiosum strains might contribute to the variable host antibody responses. In conclusion, ELI025 was secreted by all P. insidiosum strains isolated from different hosts and geographic origins, but the protein had different biochemical, and immunological characteristics. These finding contribute to the better understanding of the biology and evolution of P. insidiosum, and could lead to appropriate clinical

  7. Geographic variation in the elicitin-like glycoprotein, ELI025, of Pythium insidiosum isolated from human and animal subjects.

    PubMed

    Lerksuthirat, Tassanee; Lohnoo, Tassanee; Rujirawat, Thidarat; Yingyong, Wanta; Jongruja, Nujarin; Krajaejun, Theerapong

    2015-10-01

    Oomycetes are fungus-like in appearance, but form a distinct clade within the eukaryotes. While most pathogenic oomycetes infect plants, the understudied oomycete Pythium insidiosum infects humans and animals, and causes a life-threatening infectious disease, called pythiosis. Phylogenetic analyses divide P. insidiosum into 3 groups, according to geographic origins: Clade-I (Americas), Clade-II (Asia and Australia), and Clade-III (Thailand). Surgical removal of the infected organ is the inevitable treatment for patients with pythiosis, but it is often too late or unsuccessful, and many patients die from advanced infection. Understanding P. insidiosum's basic biology could lead to improved infection control. Elicitins, a unique group of proteins found only in oomycetes, are involved in sterol acquisition and stimulation of host responses. Recently, we identified glycosylated and non-glycosylated forms of the elicitin-like protein, ELI025, which is secreted by P. insidiosum, and detected during P. insidiosum infection. In this study, we investigated geographic variation of ELI025 in 24 P. insidiosum strains isolated from humans, animals, and the environment. Genotypes of ELI025, based on 2 sets of PCR primers, correlated well with rDNA-based phylogenetic grouping. Unlike strains in Clade-I and -II, Clade-III strains secreted no glycosylated ELI025. Sera from 17 pythiosis patients yielded a broad range of antibody responses against ELI025, and ∼30% lacked reactivity against the protein. Selective production or secretion of glycosylated ELI025 by different P. insidiosum strains might contribute to the variable host antibody responses. In conclusion, ELI025 was secreted by all P. insidiosum strains isolated from different hosts and geographic origins, but the protein had different biochemical, and immunological characteristics. These finding contribute to the better understanding of the biology and evolution of P. insidiosum, and could lead to appropriate clinical

  8. Study of nuclear reactions in laser plasmas at future ELI-NP facility

    NASA Astrophysics Data System (ADS)

    Lanzalone, G.; Altana, C.; Anzalone, A.; Cappuzzello, F.; Cavallaro, M.; Gizzi, L. A.; Labate, L.; Lamia, L.; Mascali, D.; Muoio, A.; Negoita, F.; Odorici, F.; Petrascu, H.; Trifirò, A.; Trimarchi, M.; Tudisco, S.

    2016-05-01

    In this contribution we will present the future activities that our collaboration will carry out at ELI-NP (Extreme Light Infrastructure Nuclear Physics), the new multi peta-watt Laser facility, currently under construction at Bucharest (Romania). The activities concerns the study of nuclear reactions in laser plasmas. In this framework we proposed the construction of a new, general-purpose experimental set-up able to detect and identify neutrons and charged particles.

  9. Osteogenic differentiation of adipose tissue-derived mesenchymal stem cells on nanostructured Ti6Al4V and Ti13Nb13Zr.

    PubMed

    Marini, Francesca; Luzi, Ettore; Fabbri, Sergio; Ciuffi, Simone; Sorace, Sabina; Tognarini, Isabella; Galli, Gianna; Zonefrati, Roberto; Sbaiz, Fausto; Brandi, Maria Luisa

    2015-01-01

    Bone tissue engineering and nanotechnology enable the design of suitable substitutes to restore and maintain the function of human bone tissues in complex fractures and other large skeletal defects. Long-term stability and functionality of prostheses depend on integration between bone cells and biocompatible implants. Human adipose tissue-derived mesenchymal stem cells (hAMSCs) have been shown to possess the same ability to differentiate into osteoblasts and to produce bone matrix of classical bone marrow derived stem cells (BMMSCs). Ti6A14V and Ti13Nb13Zr are two different biocompatible titanium alloys suitable for medical bone transplantation. Preliminary results from our Research Group demonstrated that smooth Ti6Al4V surfaces exhibit an osteoconductive action on hAMSCs, granting their differentiation into functional osteoblasts and sustaining bone matrix synthesis and calcification. The purpose of this study is to assay the ability of nanostructured Ti6Al4V and Ti13Nb13Zr alloys to preserve the growth and adhesion of hAMSCs and, mostly, to sustain and maintain their osteogenic differentiation and osteoblast activity. The overall results showed that both nanostructured titanium alloys are capable of sustaining cell adhesion and proliferation, to promote their differentiation into osteoblast lineage, and to support the activity of mature osteoblasts in terms of calcium deposition and bone extracellular matrix protein production.

  10. Osteogenic differentiation of adipose tissue-derived mesenchymal stem cells on nanostructured Ti6Al4V and Ti13Nb13Zr

    PubMed Central

    Marini, Francesca; Luzi, Ettore; Fabbri, Sergio; Ciuffi, Simone; Sorace, Sabina; Tognarini, Isabella; Galli, Gianna; Zonefrati, Roberto; Sbaiz, Fausto; Brandi, Maria Luisa

    2015-01-01

    Summary Bone tissue engineering and nanotechnology enable the design of suitable substitutes to restore and maintain the function of human bone tissues in complex fractures and other large skeletal defects. Long-term stability and functionality of prostheses depend on integration between bone cells and biocompatible implants. Human adipose tissue-derived mesenchymal stem cells (hAMSCs) have been shown to possess the same ability to differentiate into osteoblasts and to produce bone matrix of classical bone marrow derived stem cells (BMMSCs). Ti6A14V and Ti13Nb13Zr are two different biocompatible titanium alloys suitable for medical bone transplantation. Preliminary results from our Research Group demonstrated that smooth Ti6Al4V surfaces exhibit an osteoconductive action on hAMSCs, granting their differentiation into functional osteoblasts and sustaining bone matrix synthesis and calcification. The purpose of this study is to assay the ability of nanostructured Ti6Al4V and Ti13Nb13Zr alloys to preserve the growth and adhesion of hAMSCs and, mostly, to sustain and maintain their osteogenic differentiation and osteoblast activity. The overall results showed that both nanostructured titanium alloys are capable of sustaining cell adhesion and proliferation, to promote their differentiation into osteoblast lineage, and to support the activity of mature osteoblasts in terms of calcium deposition and bone extracellular matrix protein production. PMID:26811701

  11. In vitro Wear Rate and Co Ion Release of Compositionally and Structurally Graded CoCrMo-Ti6Al4V Structures

    PubMed Central

    Dittrick, Stanley; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit

    2010-01-01

    Novel, unitized structures with porous Ti6Al4V alloy on one side and compositionally graded, hard CoCrMo alloy surface on the other side have been fabricated using laser engineered net shaping (LENS™) process. Gradient structures with 50%, 70% and 86% CoCrMo alloy on the top surface showed high hardness in the range of 615 and 957 HV. The gradient structures were evaluated for their in vitro wear rate and Co release up to 3000 m of sliding distance. The wear rate of ultrahigh molecular weight polyethylene and 100% CoCrMo alloy substrates found to depend on the hardness and microstructural features of the counter surface rubbing against them. In general, the wear rate of both the substrates increased with a decrease in the CoCrMo alloy concentration on the top surface of gradient pins. However, the wear rate of gradient pins was lower than 100% CoCrMo alloy pins due to their high hardness. Lowest wear rate in the range of 5.07 to 7.99 × 10−8 mm3/Nm was observed for gradient pins having 86% CoCrMo alloy on the top surface. The amount of Co released, in the range of 0.38 and 0.91 ppm, during in vitro wear testing of gradient structures was comparable to that of 100% CoCrMo alloy (0.25 and 0.77 ppm). Present unitized structures with open porosity on one side and hard, wear resistant surface on the other side can minimize the wear-induced osteolysis and aseptic loosening, and eliminate the need for multiple parts with different compositions for load-bearing implants such as total hip prostheses. PMID:21516206

  12. Mixed-mode fatigue-crack growth thresholds in Ti-6Al-4V at high frequency

    SciTech Connect

    Campbell, J.P.; Ritchie, R.O.

    1999-10-22

    Multiaxial loading conditions exist at fatigue-critical locations within turbine engine components, particularly in association with fretting fatigue in the blade dovetail/disk contact section. For fatigue-crack growth in such situations, the resultant crack-driving force is a combination of the influence of a mode I (tensile opening) stress-intensity range, {Delta}K{sub I}, as well as mode II (in-plane shear) and/or mode III (anti-plane shear) stress-intensity ranges, {Delta}K{sub II} and {Delta}K{sub III}, respectively. For the case of the high-cycle fatigue of turbine-engine alloys, it is critical to quantify such behavior, as the extremely high cyclic loading frequencies ({approximately}1--2 kHz) and correspondingly short times to failure may necessitate a design approached based on the fatigue-crack growth threshold. Moreover, knowledge of such thresholds is required for accurate prediction of fretting fatigue failures. Accordingly, this paper presents the mixed-mode fatigue crack growth thresholds for mode I + II loading (phase angles from 0{degree} to 82{degree}) in a Ti-6Al-4V blade alloy. These results indicate that when fatigue-crack growth in this alloy is characterized in terms of the crack-driving force {Delta}G, which incorporates both the applied tensile and shear loading, the mode 1 fatigue-crack growth threshold is a lower bound (worst case) with respect to mixed-mode (I + II) crack-growth behavior.

  13. Understanding the Role of Hot Isostatic Pressing Parameters on the Microstructural Evolution of Ti-6Al-4V and Inconel 718 Fabricated by Electron Beam Melting

    SciTech Connect

    Peter, William H.; Nandwana, Peeyush; Kirka, Michael M.; Dehoff, Ryan R.; Sames, William; Erdman, III, Donald L.; Eklund, Anders; Howard, Ron

    2015-04-01

    In this project, Avure and ORNL evaluated the influence of hot isostatic pressing (HIP) and thermal cycling as standalone post processing techniques on the microstructure of electron beam powder bed deposited Ti-6Al-4V and Inconel 718 alloys. Electron beam powder bed deposition is an effective technology for fabricating complex net shape components that cannot be manufactured with conventional processes. However, material deposited by this technology results in columnar grain growth which is detrimental for many applications. For Ti-6Al-4V, it has been found that thermal cycling alone is not sufficient to breakdown the columnar microstructure that is typical of electron beam powder bed technology. HIP, on the other hand, has the potential to be an effective technique to break down the columnar microstructure of Ti-6Al-4V into a more equiaxed and refined β grain structure, and provide a more homogeneous microstructure compared to the thermally cycled samples. Overall, the project showed that hot isostatic pressing reduced/eliminated porosity in both Ti-6Al-4V and Inconel 718 However, based on the unique thermal cycle and the application of pressure in the HIP vessel, Ti-6Al-4V e-beam deposited microstructures were modified from columnar grain growth to equiaxed microstructures; a significant outcome to this collaboration. Inconel 718, on the other hand, shows no change in the macrostructure as a result of the current HIP cycle based on the thermal history, and would require further investigation. Though the results of HIP cycle were very good at changing the microstructure, further development in optimizing the post heat treatments and HIP cycles is required to improve mechanical properties.

  14. Improving osteointegration and osteogenesis of three-dimensional porous Ti6Al4V scaffolds by polydopamine-assisted biomimetic hydroxyapatite coating.

    PubMed

    Li, Yong; Yang, Wei; Li, Xiaokang; Zhang, Xing; Wang, Cairu; Meng, Xiangfei; Pei, Yifeng; Fan, Xiangli; Lan, Pingheng; Wang, Chunhui; Li, Xiaojie; Guo, Zheng

    2015-03-18

    Titanium alloys with various porous structures can be fabricated by advanced additive manufacturing techniques, which are attractive for use as scaffolds for bone defect repair. However, modification of the scaffold surfaces, particularly inner surfaces, is critical to improve the osteointegration of these scaffolds. In this study, a biomimetic approach was employed to construct polydopamine-assisted hydroxyapatite coating (HA/pDA) onto porous Ti6Al4V scaffolds fabricated by the electron beam melting method. The surface modification was characterized with the field emission scanning electron microscopy, energy dispersive spectroscopy, water contact angle measurement, and confocal laser scanning microscopy. Attachment and proliferation of MC3T3-E1 cells on the scaffold surface were significantly enhanced by the HA/pDA coating compared to the unmodified surfaces. Additionally, MC3T3-E1 cells grown on the HA/pDA-coated Ti6Al4V scaffolds displayed significantly higher expression of runt-related transcription factor-2, alkaline phosphatase, osteocalcin, osteopontin, and collagen type-1 compared with bare Ti6Al4V scaffolds after culture for 14 days. Moreover, microcomputed tomography analysis and Van-Gieson staining of histological sections showed that HA/pDA coating on surfaces of porous Ti6Al4V scaffolds enhanced osteointegration and significantly promoted bone regeneration after implantation in rabbit femoral condylar defects for 4 and 12 weeks. Therefore, this study provides an alternative to biofunctionalized porous Ti6Al4V scaffolds with improved osteointegration and osteogenesis functions for orthopedic applications.

  15. Improving osteointegration and osteogenesis of three-dimensional porous Ti6Al4V scaffolds by polydopamine-assisted biomimetic hydroxyapatite coating.

    PubMed

    Li, Yong; Yang, Wei; Li, Xiaokang; Zhang, Xing; Wang, Cairu; Meng, Xiangfei; Pei, Yifeng; Fan, Xiangli; Lan, Pingheng; Wang, Chunhui; Li, Xiaojie; Guo, Zheng

    2015-03-18

    Titanium alloys with various porous structures can be fabricated by advanced additive manufacturing techniques, which are attractive for use as scaffolds for bone defect repair. However, modification of the scaffold surfaces, particularly inner surfaces, is critical to improve the osteointegration of these scaffolds. In this study, a biomimetic approach was employed to construct polydopamine-assisted hydroxyapatite coating (HA/pDA) onto porous Ti6Al4V scaffolds fabricated by the electron beam melting method. The surface modification was characterized with the field emission scanning electron microscopy, energy dispersive spectroscopy, water contact angle measurement, and confocal laser scanning microscopy. Attachment and proliferation of MC3T3-E1 cells on the scaffold surface were significantly enhanced by the HA/pDA coating compared to the unmodified surfaces. Additionally, MC3T3-E1 cells grown on the HA/pDA-coated Ti6Al4V scaffolds displayed significantly higher expression of runt-related transcription factor-2, alkaline phosphatase, osteocalcin, osteopontin, and collagen type-1 compared with bare Ti6Al4V scaffolds after culture for 14 days. Moreover, microcomputed tomography analysis and Van-Gieson staining of histological sections showed that HA/pDA coating on surfaces of porous Ti6Al4V scaffolds enhanced osteointegration and significantly promoted bone regeneration after implantation in rabbit femoral condylar defects for 4 and 12 weeks. Therefore, this study provides an alternative to biofunctionalized porous Ti6Al4V scaffolds with improved osteointegration and osteogenesis functions for orthopedic applications. PMID:25711714

  16. Materials Characterization of Electron Beam Melted Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Draper, Susan; Lerch, Brad; Rogers, Richard; Martin, Richard; Locci, Ivan; Garg, Anita

    2015-01-01

    An in-depth material characterization of Electron Beam Melted (EBM) Ti-6Al-4V material has been completed. Hot Isostatic Pressing (HIP) was utilized to close porosity from fabrication and also served as a material heat treatment to obtain the desired microstructure. The changes in the microstructure and chemistry from the powder to pre-HIP and post-HIP material have been analyzed. Computed tomography (CT) scans indicated porosity closure during HIP and high-density inclusions scattered throughout the specimens. The results of tensile and high cycle fatigue (HCF) testing are compared to conventional Ti-6Al-4V. The EBM Ti-6Al-4V had similar or superior mechanical properties compared to conventionally manufactured Ti-6Al-4V.

  17. Properties of Hot Pressed Titanium Alloy Powders for Cryogenic Applications.

    NASA Technical Reports Server (NTRS)

    Friedman, G. I.; Kazaroff, J. M.

    1970-01-01

    Evaluation of strength and toughness of hot-pressed titanium alloy powders at room and at cryogenic temperatures. The purpose was to determine how the mechanical properties of solid bodies formed from powder would compare with wrought specimens of the same size and with the same chemical analysis. It was found that of five titanium powder-making processes investigated, only the Rotating Electrode Process (REP) was capable of producing ELI-grade titanium alloy powder. Blocks hot-pressed from spherical REP powders had tensile properties equivalent to or better than those obtained from wrought bar.

  18. Novel insights into the molecular pathogenesis of CYP4V2-associated Bietti's retinal dystrophy

    PubMed Central

    Astuti, Galuh D N; Sun, Vincent; Bauwens, Miriam; Zobor, Ditta; Leroy, Bart P; Omar, Amer; Jurklies, Bernhard; Lopez, Irma; Ren, Huanan; Yazar, Volkan; Hamel, Christian; Kellner, Ulrich; Wissinger, Bernd; Kohl, Susanne; De Baere, Elfride; Collin, Rob W J; Koenekoop, Robert K

    2015-01-01

    Bietti's crystalline dystrophy (BCD) is a rare, autosomal recessive retinal degenerative disease associated with mutations in CYP4V2. In this study, we describe the genetic and clinical findings in 19 unrelated BCD patients recruited from five international retinal dystrophy clinics. Patients underwent ophthalmic examinations and were screened for CYP4V2 mutations by Sanger sequencing and quantitative polymerase chain reaction (qPCR) copy number variation screening. Eight CYP4V2 mutations were found in 10/19 patients, including three patients in whom only monoallelic mutations were detected. Four novel mutations were identified: c.604G>A; p.(Glu202Lys), c.242C>G; p.(Thr81Arg), c.604+4A>G; p.(?), and c.1249dup; p.(Thr417Asnfs*2). In addition, we identified a heterozygous paternally inherited genomic deletion of at least 3.8 Mb, encompassing the complete CYP4V2 gene and several other genes, which is novel. Clinically, patients demonstrated phenotypic variability, predominantly showing choroidal sclerosis, attenuated vessels, and crystalline deposits of varying degrees of severity. To our knowledge, our study reports the first heterozygous CYP4V2 deletion and hence a novel mutational mechanism underlying BCD. Our results emphasize the importance of copy number screening in BCD. Finally, the identification of CYP4V2-negative patients with indistinguishable phenotypes from CYP4V2-positive patients might suggest the presence of mutations outside the coding regions of CYP4V2, or locus heterogeneity, which is unreported so far. PMID:25629076

  19. Tribocorrosion behavior of veneering biomedical PEEK to Ti6Al4V structures.

    PubMed

    Sampaio, Miguel; Buciumeanu, Mihaela; Henriques, Bruno; Silva, Filipe S; Souza, Júlio C M; Gomes, José R

    2016-02-01

    In dentistry, prosthetic structures must be able to support masticatory loads combined with a high biocompatibility and wear resistance in the presence of a corrosive environment. In order to improve the simultaneous wear and corrosion response of highly biocompatible prosthetic structures, a veneering poly-ether-ether-ketone (PEEK) to Ti6Al4V substrate was assessed by tribocorrosion analyses under conditions mimicking the oral environment. Samples were synthesized by hot pressing the PEEK veneer onto Ti6Al4V cylinders. The tribocorrosion tests on Ti6Al4V or PEEK/Ti6Al4V samples were performed on a reciprocating ball-on-plate tribometer at 30N normal load, 1Hz and stroke length of 3mm. The tests were carried out in artificial saliva at 37°C. Open circuit potential (OCP) was measured before, during and after reciprocating sliding tests. The worn surfaces were characterized by scanning electron microscopy. The results revealed a lower wear rate on PEEK combined with a lower coefficient of friction (COF), when compared to Ti6Al4V. In fact, PEEK protected Ti6Al4V substrate against the corrosive environment and wear avoiding the release of metallic ions to the surrounding environment. PMID:26454136

  20. New titanium alloys for biomaterials: a study of mechanical and corrosion properties and cytotoxicity.

    PubMed

    Kim, T I; Han, J H; Lee, I S; Lee, K H; Shin, M C; Choi, B B

    1997-01-01

    Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.

  1. Eruptive history of an alkali basaltic diatreme from Elie Ness, Fife, Scotland

    NASA Astrophysics Data System (ADS)

    Gernon, T. M.; Upton, B. G. J.; Hincks, T. K.

    2013-05-01

    The Elie Ness diatreme (Fife, Scotland) is an ideal place to study the internal architecture and emplacement processes of diatremes. Elie Ness is one of approximately 100 alkali basaltic diatremes and intrusions in the East Fife area, emplaced during Upper Carboniferous to Early Permian times into an extensive rift system in the northern Variscan foreland. Within the diatreme, seven lithofacies and three lithofacies associations (LFAs 1-3) are recognised. Field, petrographic and geochemical studies demonstrate that the diatreme experienced a protracted history of eruption and infill, initially driven by volatile expansion and later by magma-water interaction. Massive lapilli tuffs of LFA 1 contain abundant highly vesicular juvenile scoria and magma-coated clasts, which are best explained by a magmatic origin for the early explosive eruptions. On a large-scale, the tuffs are well mixed and locally exhibit small-scale degassing structures attributed to fluidisation processes occurring within the diatreme fill. The occurrence of abundant volcaniclastic autoliths and megablocks within LFA 1 can be explained by subsidence of volcaniclastic strata from the maar crater and upper diatreme during emplacement. Pyroclastic density current deposits of LFA 2 form a series of continuous sheets across the diatreme, some of which may have originated from phreatomagmatic explosions in a neighbouring vent. We attribute the overall bedding pattern to a combination of primary volcanic processes and post-depositional folding related to movement along an adjacent fault. Minor steeply inclined breccias and tuffs of LFA 3 cross-cut the LFA 2 succession and are interpreted as late-stage volcaniclastic dykes and conduits, signalling the final phase of eruptive activity at Elie Ness. The study offers new insights into the volcanic evolution of diatremes fed by low viscosity, alkali-rich magmas.

  2. Free-Form-Fabricated Commercially Pure Ti and Ti6Al4V Porous Scaffolds Support the Growth of Human Embryonic Stem Cell-Derived Mesodermal Progenitors

    PubMed Central

    de Peppo, G. M.; Palmquist, A.; Borchardt, P.; Lennerås, M.; Hyllner, J.; Snis, A.; Lausmaa, J.; Thomsen, P.; Karlsson, C.

    2012-01-01

    Commercially-pure titanium (cp-Ti) and the titanium-aluminum-vanadium alloy (Ti6Al4V) are widely used as reconstructive implants for skeletal engineering applications, due to their good mechanical properties, biocompatibility and ability to integrate with the surrounding bone. Electron beam melting technology (EBM) allows the fabrication of customized implants with tailored mechanical properties and high potential in the clinical practice. In order to augment the interaction with the biological tissue, stem cells have recently been combined with metallic scaffolds for skeletal engineering applications. We previously demonstrated that human embryonic stem cell-derived mesodermal progenitors (hES-MPs) hold a great potential to provide a homogeneous and unlimited supply of cells for bone engineering applications. This study demonstrates the effect of EBM-fabricated cp-Ti and Ti6Al4V porous scaffolds on hES-MPs behavior, in terms of cell attachment, growth and osteogenic differentiation. Displaying different chemical composition but similar surface properties, EBM-fabricated cp-Ti and Ti6Al4V scaffolds supported cell attachment and growth, and did not seem to alter the expression of genes involved in osteogenic differentiation and affect the alkaline phosphatase activity. In conclusion, interfacing hES-MPs to EBM-fabricated scaffolds may represent an interesting strategy for design of third-generation biomaterials, with the potential to promote implant integration in clinical conditions characterized by poor bone quality. PMID:22262956

  3. A Honeycomb-Structured Ti-6Al-4V Oil-Gas Separation Rotor Additively Manufactured by Selective Electron Beam Melting for Aero-engine Applications

    NASA Astrophysics Data System (ADS)

    Tang, H. P.; Wang, Q. B.; Yang, G. Y.; Gu, J.; Liu, N.; Jia, L.; Qian, M.

    2016-03-01

    Oil -gas separation is a key process in an aero-engine lubrication system. This study reports an innovative development in oil -gas separation. A honeycomb-structured rotor with hexagonal cone-shaped pore channels has been designed, additively manufactured from Ti-6Al-4V using selective electron beam melting (SEBM) and assessed for oil -gas separation for aero-engine application. The Ti-6Al-4V honeycomb structure showed a high compressive strength of 110 MPa compared to less than 20 MPa for metal foam structures. The oil -gas separation efficiency of the honeycomb-structured separation rotor achieved 99.8% at the rotation speed of 6000 rpm with much lower ventilation resistance (17.3 kPa) than that of the separator rotor constructed using a Ni-Cr alloy foam structure (23.5 kPa). The honeycomb-structured Ti-6Al-4V separator rotor produced by SEBM provides a promising solution to more efficient oil -gas separation in the aero-engine lubrication system.

  4. Cryogenic stopping cell for photofission fragments at the ELI-NP facility

    SciTech Connect

    Constantin, P. Balabanski, D. L.; Cuong, P. V.

    2015-10-15

    The brilliant gamma beam at the future Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility will be used to generate a beam of exotic neutron-rich isotopes via photofission of actinide targets. We present simulations with the Geant4 toolkit of the photofission process for the design and optimization of the expected performance parameters of the Cryogenic Stopping Cell (CSC). The CSC will be used to extract the photofission fragments into the secondary beam of about 10{sup 6} ions/s. We propose an experimental program to study refractory neutron-rich isotopes.

  5. Depositional processes of the basaltic Elie Ness diatreme, East Fife, Scotland

    NASA Astrophysics Data System (ADS)

    Gernon, Thomas; Hincks, Thea

    2010-05-01

    The East Fife coast of Scotland exposes multiple (~100) volcanic vents or diatremes of late Carboniferous to early Permian age. Here, we present preliminary results of detailed geological mapping of the Elie Ness (EN) diatreme. The key objective was to map the volcanic structure and lithofacies of the vent-fill, and to determine the eruption styles and key emplacement processes that occur more generally in basaltic maar-diatreme systems. Within the EN diatreme, seven lithofacies and three lithofacies associations (LFA 1-3) were recognised. Preliminary results demonstrate that the diatreme had a protracted history of eruption and infill. The massive lapilli tuffs of LFA 1 are texturally and compositionally homogeneous with occasional degassing structures, making them similar to typical massive volcaniclastic deposits infilling kimberlite pipes. The formation of such deposits are attributed to gas-fluidisation processes operating within the vent. The occurrence within LFA 1 of abundant volcaniclastic autoliths and megablocks together with steeply inclined lenticular breccia and tuff packages, makes the deposits similar to marginal lithofacies of the Jwaneng Centre kimberlite pipe, Botswana. All these features can be explained by subsidence of volcaniclastic strata from the surrounding tephra ring during emplacement. The steep internal contacts between the lithofacies of LFA 1 can be explained by variations in gas flux as the main eruptive phase waned. Pyroclastic base surge deposits of LFA 2 form a series of continuous sheets across the EN diatreme, and are therefore likely to have originated from a neighbouring pipe. The most probable source of the LFA 2 pyroclastic surges is a small vent to the NE of Elie Ness, where similar diffuse stratified lithofacies are observed. Minor steeply-inclined breccias and tuffs of LFA 3 cross-cut bedded tuffs of LFA 2, and are therefore likely to represent late-stage dykes and conduits. A significant observation is that the diatreme

  6. Immunology's foundation: the 100-year anniversary of the Nobel Prize to Paul Ehrlich and Elie Metchnikoff.

    PubMed

    Kaufmann, Stefan H E

    2008-07-01

    One hundred years ago the birth of immunology was made official by the Nobel Prize award to Elie Metchnikoff and Paul Ehrlich. Metchnikoff discovered phagocytosis by macrophages and microphages as a critical host-defense mechanism and thus is considered the father of cellular innate immunity. Ehrlich described the side-chain theory of antibody formation and the mechanisms of how antibodies neutralize toxins and induce bacterial lysis with the help of complement and thus is considered one of the fathers of humoral adaptive immunity. Despite many discordant discussions in the initial phase after these discoveries, innate and adaptive responses are now known to be complementary partners in producing robust immunity.

  7. An antibacterial and antiviral peptide produced by Enterococcus mundtii ST4V isolated from soya beans.

    PubMed

    Todorov, Svetoslav D; Wachsman, Mónica B; Knoetze, Hendriëtte; Meincken, Martina; Dicks, Leon M T

    2005-06-01

    Enterococcus mundtii ST4V, isolated from soya beans, produces a 3950Da antibacterial peptide active against Gram-positive and Gram-negative bacteria, including Enterococcus faecalis, Streptococcus spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae and Staphylococcus aureus. The peptide also inactivated the herpes simplex viruses HSV-1 (strain F) and HSV-2 (strain G), a polio virus (PV3, strain Sabin) and a measles virus (strain MV/BRAZIL/001/91, an attenuated strain of MV). MV, HSV-1 and HSV-2 were 95.5%-99.9% inactivated by peptide ST4V at 400 microg/ml. Monkey kidney Vero cells were not inactivated, even at four times the level peptide ST4V displayed antiviral activity, indicating that the effect was not due to cytotoxicity. Complete inactivation or significant reduction in antimicrobial activity was observed after treatment of peptide ST4V with Proteinase K, pronase, pepsin and trypsin. No change in antimicrobial activity was recorded after treatment with alpha-amylase, suggesting that peptide ST4V was not glycosylated. This is the first description of an antibacterial and antiviral peptide with such broad-spectrum of activity, produced by a lactic acid bacterium.

  8. Materials Characterization of Electron Beam Melted Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Draper, Susan L.; Lerch, Bradley A.; Telesman, Jack; Martin, Richard E.; Locci, Ivan E.; Garg, Anita; Ring, Andrew J.

    2016-01-01

    An in-depth material characterization of Electron Beam Melted (EBM) Ti-6Al-4V material has been completed on samples fabricated on an ARCAM A2X EBM machine. The specimens were fabricated under eight separate builds with the material divided into two lots for material testing purposes. Hot Isostatic Pressing (HIP) was utilized to close porosity from fabrication and also served as a material heat treatment to obtain the desired microstructure. The changes in the microstructure and chemistry from the powder to pre-HIP and post-HIP material have been analyzed. Several nondestructive evaluation (NDE) techniques were utilized to characterize the samples both before and after HIP. The test matrix included tensile, high cycle fatigue, low cycle fatigue, fracture toughness, and fatigue crack growth at cryogenic, room, and elevated temperatures. The mechanical properties of the EBM Ti-6Al-4V are compared to conventional Ti-6Al-4V in the annealed condition. Fractography was performed to determine failure initiation site. The EBM Ti-6Al-4V had similar or superior mechanical properties compared to conventionally manufactured Ti-6Al-4V.

  9. An antibacterial and antiviral peptide produced by Enterococcus mundtii ST4V isolated from soya beans.

    PubMed

    Todorov, Svetoslav D; Wachsman, Mónica B; Knoetze, Hendriëtte; Meincken, Martina; Dicks, Leon M T

    2005-06-01

    Enterococcus mundtii ST4V, isolated from soya beans, produces a 3950Da antibacterial peptide active against Gram-positive and Gram-negative bacteria, including Enterococcus faecalis, Streptococcus spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae and Staphylococcus aureus. The peptide also inactivated the herpes simplex viruses HSV-1 (strain F) and HSV-2 (strain G), a polio virus (PV3, strain Sabin) and a measles virus (strain MV/BRAZIL/001/91, an attenuated strain of MV). MV, HSV-1 and HSV-2 were 95.5%-99.9% inactivated by peptide ST4V at 400 microg/ml. Monkey kidney Vero cells were not inactivated, even at four times the level peptide ST4V displayed antiviral activity, indicating that the effect was not due to cytotoxicity. Complete inactivation or significant reduction in antimicrobial activity was observed after treatment of peptide ST4V with Proteinase K, pronase, pepsin and trypsin. No change in antimicrobial activity was recorded after treatment with alpha-amylase, suggesting that peptide ST4V was not glycosylated. This is the first description of an antibacterial and antiviral peptide with such broad-spectrum of activity, produced by a lactic acid bacterium. PMID:15869868

  10. Development of porous Ti6Al4V/chitosan sponge composite scaffold for orthopedic applications.

    PubMed

    Guo, Miao; Li, Xiang

    2016-01-01

    A novel composite scaffold consisting of porous Ti6Al4V part filled with chitosan sponge was fabricated using a combination of electron beam melting and freeze-drying. The mechanical properties of porous Ti6Al4V part were examined via compressive test. The ultimate compressive strength was 85.35 ± 8.68 MPa and the compressive modulus was 2.26 ± 0.42 GPa. The microstructure of composite scaffold was characterized using scanning electron microscopy. The chitosan sponge filled in Ti6Al4V part exhibited highly porous and well-interconnected micro-pore architecture. The osteoblastic cells were seeded on scaffolds to test their seeding efficiency and biocompatibility. Significantly higher cell seeding efficiency was found on composite scaffold. The biological response of osteoblasts on composite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to porous Ti6Al4V part. These results suggest that the Ti6Al4V/chitosan composite scaffold is potentially useful as a biomedical scaffold for orthopedic applications. PMID:26478418

  11. Development of porous Ti6Al4V/chitosan sponge composite scaffold for orthopedic applications.

    PubMed

    Guo, Miao; Li, Xiang

    2016-01-01

    A novel composite scaffold consisting of porous Ti6Al4V part filled with chitosan sponge was fabricated using a combination of electron beam melting and freeze-drying. The mechanical properties of porous Ti6Al4V part were examined via compressive test. The ultimate compressive strength was 85.35 ± 8.68 MPa and the compressive modulus was 2.26 ± 0.42 GPa. The microstructure of composite scaffold was characterized using scanning electron microscopy. The chitosan sponge filled in Ti6Al4V part exhibited highly porous and well-interconnected micro-pore architecture. The osteoblastic cells were seeded on scaffolds to test their seeding efficiency and biocompatibility. Significantly higher cell seeding efficiency was found on composite scaffold. The biological response of osteoblasts on composite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to porous Ti6Al4V part. These results suggest that the Ti6Al4V/chitosan composite scaffold is potentially useful as a biomedical scaffold for orthopedic applications.

  12. Identification of Conserved MEL-28/ELYS Domains with Essential Roles in Nuclear Assembly and Chromosome Segregation.

    PubMed

    Gómez-Saldivar, Georgina; Fernandez, Anita; Hirano, Yasuhiro; Mauro, Michael; Lai, Allison; Ayuso, Cristina; Haraguchi, Tokuko; Hiraoka, Yasushi; Piano, Fabio; Askjaer, Peter

    2016-06-01

    Nucleoporins are the constituents of nuclear pore complexes (NPCs) and are essential regulators of nucleocytoplasmic transport, gene expression and genome stability. The nucleoporin MEL-28/ELYS plays a critical role in post-mitotic NPC reassembly through recruitment of the NUP107-160 subcomplex, and is required for correct segregation of mitotic chromosomes. Here we present a systematic functional and structural analysis of MEL-28 in C. elegans early development and human ELYS in cultured cells. We have identified functional domains responsible for nuclear envelope and kinetochore localization, chromatin binding, mitotic spindle matrix association and chromosome segregation. Surprisingly, we found that perturbations to MEL-28's conserved AT-hook domain do not affect MEL-28 localization although they disrupt MEL-28 function and delay cell cycle progression in a DNA damage checkpoint-dependent manner. Our analyses also uncover a novel meiotic role of MEL-28. Together, these results show that MEL-28 has conserved structural domains that are essential for its fundamental roles in NPC assembly and chromosome segregation. PMID:27341616

  13. The Electronic Logbook for the Information Storage of ATLAS Experiment at LHC (ELisA)

    NASA Astrophysics Data System (ADS)

    Corso Radu, A.; Lehmann Miotto, G.; Magnoni, L.

    2012-12-01

    A large experiment like ATLAS at LHC (CERN), with over three thousand members and a shift crew of 15 people running the experiment 24/7, needs an easy and reliable tool to gather all the information concerning the experiment development, installation, deployment and exploitation over its lifetime. With the increasing number of users and the accumulation of stored information since the experiment start-up, the electronic logbook actually in use, ATLOG, started to show its limitations in terms of speed and usability. Its monolithic architecture makes the maintenance and implementation of new functionality a hard-to-almost-impossible process. A new tool ELisA has been developed to replace the existing ATLOG. It is based on modern web technologies: the Spring framework using a Model-View-Controller architecture was chosen, thus helping building flexible and easy to maintain applications. The new tool implements all features of the old electronic logbook with increased performance and better graphics: it uses the same database back-end for portability reasons. In addition, several new requirements have been accommodated which could not be implemented in ATLOG. This paper describes the architecture, implementation and performance of ELisA, with particular emphasis on the choices that allowed having a scalable and very fast system and on the aspects that could be re-used in different contexts to build a similar application.

  14. Strong field physics and QED experiments with ELI-NP 2×10PW laser beams

    SciTech Connect

    Turcu, I. C. E. Balascuta, S. Negoita, F.; Jaroszynski, D.; McKenna, P.

    2015-02-24

    The ELI-NP facility will focus a 10 PW pulsed laser beam at intensities of ∼10{sup 23} W/cm{sup 2} for the first time, enabling investigation of the new physical phenomena at the interfaces of plasma, nuclear and particle physics. The electric field in the laser focus has a maximum value of ∼10{sup 15} V/m at such laser intensities. In the ELI-NP Experimental Area E6, we propose the study of Radiation Reaction, Strong Field Quantum Electrodynamics (QED) effects and resulting production of Ultra-bright Sources of Gamma-rays which could be used for nuclear activation. Two powerful, synchronized 10 PW laser beams will be focused in the E6 Interaction Chamber on either gas or solid targets. One 10 PW beam is the Pump-beam and the other is the Probe-beam. The focused Pump beam accelerates the electrons to relativistic energies. The accelerated electron bunches interact with the very high electro-magnetic field of the focused Probe beam. The layout of the experimental area E6 will be presented with several options for the experimental configurations.

  15. Identification of Conserved MEL-28/ELYS Domains with Essential Roles in Nuclear Assembly and Chromosome Segregation

    PubMed Central

    Hirano, Yasuhiro; Mauro, Michael; Lai, Allison; Ayuso, Cristina; Haraguchi, Tokuko; Hiraoka, Yasushi; Piano, Fabio

    2016-01-01

    Nucleoporins are the constituents of nuclear pore complexes (NPCs) and are essential regulators of nucleocytoplasmic transport, gene expression and genome stability. The nucleoporin MEL-28/ELYS plays a critical role in post-mitotic NPC reassembly through recruitment of the NUP107-160 subcomplex, and is required for correct segregation of mitotic chromosomes. Here we present a systematic functional and structural analysis of MEL-28 in C. elegans early development and human ELYS in cultured cells. We have identified functional domains responsible for nuclear envelope and kinetochore localization, chromatin binding, mitotic spindle matrix association and chromosome segregation. Surprisingly, we found that perturbations to MEL-28’s conserved AT-hook domain do not affect MEL-28 localization although they disrupt MEL-28 function and delay cell cycle progression in a DNA damage checkpoint-dependent manner. Our analyses also uncover a novel meiotic role of MEL-28. Together, these results show that MEL-28 has conserved structural domains that are essential for its fundamental roles in NPC assembly and chromosome segregation. PMID:27341616

  16. Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP

    SciTech Connect

    Negoita, F. Gugiu, M. Petrascu, H. Petrone, C. Pietreanu, D.; Fuchs, J.; Chen, S.; Higginson, D.; Vassura, L.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Antici, P.; Balabanski, D.; Balascuta, S.; Cernaianu, M.; Dancus, I.; Gales, S.; Neagu, L.; Petcu, C.; and others

    2015-02-24

    The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr{sub 3}(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.

  17. Effects of Process Parameters on Deformation and Temperature Uniformity of Forged Ti-6Al-4V Turbine Blade

    NASA Astrophysics Data System (ADS)

    Luo, Shiyuan; Zhu, Dahu; Hua, Lin; Qian, Dongsheng; Yan, Sijie; Yu, Fengping

    2016-09-01

    This work is motivated by the frequent occurrence of macro- and microdefects within forged Ti-6Al-4V turbine blades due to the severely nonuniform strain and temperature distributions. To overcome the problem of nonuniformity during the blade forging operation, firstly, a 2D coupled thermo-mechanical finite element approach using the strain-compensated Arrhenius-type constitutive model is employed to simulate the real movements and processing conditions, and its reliability is verified experimentally. Secondly, two evaluation indexes, standard deviation of equivalent plastic strain and standard deviation of temperature, are proposed to evaluate the uniformity characteristics within the forged blade, and the effects of four process parameters including the forging velocity, friction factor, initial workpiece temperature and dwell time on the uniformity of strain and temperature distributions are carefully studied. Finally, the numerically optimized combination of process parameters is validated by the application in a practical process. The parametric study reveals that a reasonable combination of process parameters considering the flow resistance, flow localization and the effects of deformation and friction heating is crucial for the titanium alloy blade forging with uniformity. This work can provide a significant guidance for the design and optimization of blade forging processes.

  18. Finite Element Simulations of Micro Turning of Ti-6Al-4V using PCD and Coated Carbide tools

    NASA Astrophysics Data System (ADS)

    Jagadesh, Thangavel; Samuel, G. L.

    2016-07-01

    The demand for manufacturing axi-symmetric Ti-6Al-4V implants is increasing in biomedical applications and it involves micro turning process. To understand the micro turning process, in this work, a 3D finite element model has been developed for predicting the tool chip interface temperature, cutting, thrust and axial forces. Strain gradient effect has been included in the Johnson-Cook material model to represent the flow stress of the work material. To verify the simulation results, experiments have been conducted at four different feed rates and at three different cutting speeds. Since titanium alloy has low Young's modulus, spring back effect is predominant for higher edge radius coated carbide tool which leads to the increase in the forces. Whereas, polycrystalline diamond (PCD) tool has smaller edge radius that leads to lesser forces and decrease in tool chip interface temperature due to high thermal conductivity. Tool chip interface temperature increases by increasing the cutting speed, however the increase is less for PCD tool as compared to the coated carbide tool. When uncut chip thickness decreases, there is an increase in specific cutting energy due to material strengthening effects. Surface roughness is higher for coated carbide tool due to ploughing effect when compared with PCD tool. The average prediction error of finite element model for cutting and thrust forces are 11.45 and 14.87 % respectively.

  19. Increased osteoblast adhesion on nanophase metals: Ti, Ti6Al4V, and CoCrMo.

    PubMed

    Webster, Thomas J; Ejiofor, Jeremiah U

    2004-08-01

    Previous studies have demonstrated increased functions of osteoblasts (bone-forming cells) on nanophase compared to conventional ceramics (specifically, alumina, titania, and hydroxyapatite), polymers (such as poly lactic-glycolic acid and polyurethane), carbon nanofibers/nanotubes, and composites thereof. Nanophase materials are unique materials that simulate dimensions of constituent components of bone since they possess particle or grain sizes less than 100 nm. However, to date, interactions of osteoblasts on nanophase compared to conventional metals remain to be elucidated. For this reason, the objective of the present in vitro study was to synthesize, characterize, and evaluate osteoblast adhesion on nanophase metals (specifically, Ti, Ti6Al4V, and CoCrMo alloys). Such metals in conventional form are widely used in orthopedic applications. Results of this study provided the first evidence of increased osteoblast adhesion on nanophase compared to conventional metals. Interestingly, osteoblast adhesion occurred preferentially at surface particle boundaries for both nanophase and conventional metals. Since more particle boundaries are present on the surface of nanophase compared to conventional metals, this may be an explanation for the measured increased osteoblast adhesion. Lastly, material characterization studies revealed that nanometal surfaces possessed similar chemistry and only altered in degree of nanometer surface roughness when compared to their respective conventional counterparts. Because osteoblast adhesion is a necessary prerequisite for subsequent functions (such as deposition of calcium-containing mineral), the present study suggests that nanophase metals should be further considered for orthopedic implant applications.

  20. Characterization of the Ti-10Nb-10Zr-5Ta Alloy for Biomedical Applications. Part 2: Wettability, Tribological Performance and Biocompatibility

    NASA Astrophysics Data System (ADS)

    Braic, V.; Balaceanu, M.; Braic, M.; Vitelaru, C.; Titorencu, I.; Pruna, V.; Parau, A. C.; Fanara, C.; Vladescu, A.

    2014-01-01

    The Ti-10Nb-10Zr-5Ta alloy, prepared in a levitation melting furnace, was investigated as a possible candidate for replacing Ti6Al4V alloy in medical applications. The sessile drop method, pin-on-disc and in vitro tests were used to analyze wettability, wear resistance, and biocompatibility of the new alloy. The characteristics of the Ti-10Nb-10Zr-5Ta alloy were assessed in comparison to those of the Ti6Al4V alloy. The Ti-10Nb-10Zr-5Ta system was found to have hydrophilic characteristics with similar contact angle as the Ti6Al4V alloy. In all environments (deionized water, simulated body fluid and Fusayama Meyer artificial saliva), the friction coefficient showed a stable evolution versus sliding distance, being similar for both alloys. On overall, the wear resistance of Ti-10Nb-10Zr-5Ta alloy was lower than that of Ti6Al4V for all testing environments. The Ti-10Nb-10Zr-5Ta alloy exhibited good biocompatibility characteristics at in vitro test compared to Ti6Al4V alloy. The cell viability on Ti-10Nb-10Zr-5Ta surfaces was higher than the one observed on Ti6Al4V samples, regardless the number of days spent in osteoblast-like cells culture. A high degree of cell attachment and spreading was observed on both alloys.

  1. New metallographic preparation techniques for tantalum and tantalum alloys

    SciTech Connect

    Kelly, A.M.; Bingert, S.R.; Reiswig, R.D.

    1995-09-01

    Two new metallographic techniques have been developed for tantalum and its alloys. The first is a chemical polishing method that can even be used on specimens immediately after grinding on silicon carbide papers. The second is an etching technique that even delineates low-angle grain boundaries, making it particularly suitable for quantitative grain size measurements. It has also been determined that these are suitable for the preparation of a surprisingly large variety of other metals and alloys, including, titanium, tungsten, Ti-6Al-4V, molybdenum, a Zr-Ti-Cu-Ni alloy, a Ti-Ta-Sc alloy, Fansteel 85, and a Hf-Zr alloy to name a few.

  2. Influence of UFG structure formation on mechanical and fatigue properties in Ti-6Al-7Nb alloy

    NASA Astrophysics Data System (ADS)

    Polyakova, V. V.; Anumalasetty, V. N.; Semenova, I. P.; Valiev, R. Z.

    2014-08-01

    Ultrafine-grained (UFG) Ti alloys have potential applications in osteosynthesis and orthopedics due to high bio-compatibility and increased weight-to- strength ratio. In current study, Ti6Al7Nb ELI alloy is processed through equal channel angular pressing-conform (ECAP-Conform) and subsequent thermomechanical processing to generate a UFG microstructure. The fatigue properties of UFG alloys are compared to coarse grained (CG) alloys. Our study demonstrates that the UFG alloys with an average grain size of ~180 nm showed 35% enhancement of fatigue endurance limit as compared to coarse-grained alloys. On the fracture surfaces of the UFG and CG samples fatigue striations and dimpled relief were observed. However, the fracture surface of the UFG sample looks smoother; fewer amounts of secondary micro-cracks and more ductile rupture were also observed, which testifies to the good crack resistance in the UFG alloy after high-cyclic fatigue tests.

  3. National uranium resource evaluation program: hydrogeochemical and stream sediment reconnaissance basic data for Ely quadrangle, Nevada; Utah

    SciTech Connect

    Not Available

    1981-10-15

    Field and laboratory data are presented for 1937 sediment samples from the Ely Quadrangle, Nevada; Utah. The samples were collected by Savannah River Laboratory; laboratory analysis and data reporting were performed by the Uranium Resource Evaluation Project at Oak Ridge, Tennessee.

  4. ELI/SBP'S UVB (VACUUM VAPORIZATION WELL) SYSTEM FOR TREATMENT OF VOC-CONTAMINATED SOILS; INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    This report summarizes the findings of an evaluation of the Unterdruck-Verdampfer-Brunnen (UVB) technology developed by IEG Technologies (IEG) and licensed in the eastern United States by Environmental Laboratories, Inc. (ELI) and SBP Technologies (SBP). This evaluation was cond...

  5. 78 FR 33426 - Eli Lilly and Co.; Withdrawal of Approval of a New Drug Application for ORAFLEX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-04

    ... HUMAN SERVICES Food and Drug Administration Eli Lilly and Co.; Withdrawal of Approval of a New Drug... Administration (FDA) is withdrawing approval of a new drug application (NDA) for ORAFLEX (benoxaprofen) Tablets... Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave., Bldg. 51, rm. 6250,...

  6. Eli Whitney's Patent for the Cotton Gin. The Constitution Community: Revolution and the New Nation (1754-1820s).

    ERIC Educational Resources Information Center

    Schur, Joan Brodsky

    This lesson focuses on the power of the U.S. Congress to pass laws related to issuing patents. Using Eli Whitney's 1812 Congressional petition to extend the patent on his cotton gin as an example, the lesson correlates to the National History Standards and the National Standards for Civics and Government. It contains two primary source documents,…

  7. CFL Labeling Harmonization in the United States, China, Brazil andELI Member Countries: Specifications, Testing, and MutualRecognition

    SciTech Connect

    Fridley, David; Lin, Jiang; Denver, Andrea; Biermayer, Peter; Dillavou, Tyler

    2005-07-20

    This report examines critical differences among energy-efficient labeling programs for CFLs in Brazil, China, the United States, and the seven members of the international Efficient Lighting Initiative (ELI) in terms of technical specifications and test procedures, and review issues related to international harmonization of these standards.

  8. A Constitutive Equation Relating Composition and Microstructure to Properties in Ti-6Al-4V: As Derived Using a Novel Integrated Computational Approach

    NASA Astrophysics Data System (ADS)

    Ghamarian, Iman; Samimi, Peyman; Dixit, Vikas; Collins, Peter C.

    2015-11-01

    While it is useful to predict properties in metallic materials based upon the composition and microstructure, the complexity of real, multi-component, and multi-phase engineering alloys presents difficulties when attempting to determine constituent-based phenomenological equations. This paper applies an approach based upon the integration of three separate modeling approaches, specifically artificial neural networks, genetic algorithms, and Monte Carlo simulations to determine a mechanism-based equation for the yield strength of α+ β processed Ti-6Al-4V (all compositions in weight percent) which consists of a complex multi-phase microstructure with varying spatial and morphological distributions of the key microstructural features. Notably, this is an industrially important alloy yet an alloy for which such an equation does not exist in the published literature. The equation ultimately derived in this work not only can accurately describe the properties of the current dataset but also is consistent with the limited and dissociated information available in the literature regarding certain parameters such as intrinsic yield strength of pure hexagonal close-packed alpha titanium. In addition, this equation suggests new interesting opportunities for controlling yield strength by controlling the relative intrinsic strengths of the two phases through solid solution strengthening.

  9. A conceptual design of an electron spectrometer for ELI-NP

    SciTech Connect

    Balascuta, S. Turcu, I. C. E.

    2015-02-24

    We present the geometry and field parameters of an Electron Spectrometer (ES) with two dipole magnets, considered for electron energy measurements at the High Fields QED experimental area at ELI-NP. The first magnet is a 2 meter long permanent magnet, placed inside the Interaction Chamber (IC). The second magnet is a 1.5 meters long electromagnet, placed outside IC. The pulsed electron beam will be produced by the 10 PW pulsed Laser, ‘pump-beam’, focused into one meter long capillary low density plasma cell. A second 10 PW pulsed Laser, ‘probe-beam’, will interact with the relativistic electron bunch providing the strong electromagnetic field. The ES will measure the subtle changes in the electron energy spectrum as a result of the electron beam interaction with the probe-beam field.

  10. A Journey with Elie Metchnikoff: From Innate Cell Mechanisms in Infectious Diseases to Quantum Biology

    PubMed Central

    Merien, Fabrice

    2016-01-01

    Many reviews of Elie Metchnikoff’s work have been published, all unanimously acknowledging the significant contributions of his cellular theory to the fields of immunology and infectious diseases. In 1883, he published a key paper describing phagocytic cells in frogs. His descriptions were not just about phagocytes involved in host defense, he also described how these specialized cells eliminated degenerating or dying cells of the host. This perspective focuses on key concepts developed by Metchnikoff by presenting relevant excerpts of his 1883 paper and matching these concepts with challenges of modern immunology. A new approach to macrophage polarization is included to introduce some creative thinking about the exciting emerging area of quantum biology. PMID:27379227

  11. Positron production at extreme light infrastructure – nuclear physics (ELI-NP)

    SciTech Connect

    Oprisa, A. Balascuta, S. Ur, C. A.

    2015-02-24

    Applied and material physics studies with positron beams of Fermi–surfaces, defects, interfaces etc. offer excellent diagnostics tools. At ELI-NP, an intense γ beam of about 10{sup 11} photons/s with energies up to 3.5 MeV will be used to generate a positron beam via pair production in a tungsten converter target. To obtain a high intensity beam of moderated positrons the design of the positron source is of high importance. The design of a dedicated positron source at ELI–NP is being investigated based on extensive GEANT4 simulations. The goal of the simulations is to optimize the geometry of the target and the gamma beam collimation. We present here the characteristics of the positron beam obtained for different geometries of the converter target.

  12. ELI-Beamlines: development of next generation short-pulse laser systems

    NASA Astrophysics Data System (ADS)

    Rus, B.; Bakule, P.; Kramer, D.; Naylon, J.; Thoma, J.; Green, J. T.; Antipenkov, R.; Fibrich, M.; Novák, J.; Batysta, F.; Mazanec, T.; Drouin, M. A.; Kasl, K.; Baše, R.; Peceli, D.; Koubíková, L.; Trojek, P.; Boge, R.; Lagron, J. C.; Vyhlídka, Å.; Weiss, J.; Cupal, J.,; Hřebíček, J.; Hříbek, P.; Durák, M.; Polan, J.; Košelja, M.; Korn, G.; Horáček, M.; Horáček, J.; Himmel, B.; Havlíček, T.; Honsa, A.; Korouš, P.; Laub, M.; Haefner, C.; Bayramian, A.; Spinka, T.; Marshall, C.; Johnson, G.; Telford, S.; Horner, J.; Deri, B.; Metzger, T.; Schultze, M.; Mason, P.; Ertel, K.; Lintern, A.; Greenhalgh, J.; Edwards, C.; Hernandez-Gomez, C.; Collier, J.; Ditmire, T.,; Gaul, E.; Martinez, M.; Frederickson, C.; Hammond, D.; Malato, C.; White, W.; Houžvička, J.

    2015-05-01

    Overview of the laser systems being built for ELI-Beamlines is presented. The facility will make available high-brightness multi-TW ultrashort laser pulses at kHz repetition rate, PW 10 Hz repetition rate pulses, and kilojoule nanosecond pulses for generation of 10 PW peak power. The lasers will extensively employ the emerging technology of diode-pumped solid-state lasers (DPSSL) to pump OPCPA and Ti:sapphire broadband amplifiers. These systems will provide the user community with cutting-edge laser resources for programmatic research in generation and applications of high-intensity X-ray sources, in particle acceleration, and in dense-plasma and high-field physics.

  13. The development of molecularly targeted anticancer therapies: an Eli Lilly and Company perspective.

    PubMed

    Perry, William L; Weitzman, Aaron

    2005-03-01

    The ability to identify activated pathways that drive the growth and progression of cancer and to develop specific and potent inhibitors of key proteins in these pathways promises to dramatically change the treatment of cancer: A patient's cancer could be characterized at the molecular level and the information used to select the best treatment options. The development of successful therapies not only requires extensive target validation, but also new approaches to evaluating drug efficacy in animal models and in the clinic compared to the development of traditional cytotoxic agents. This article highlights Eli Lilly and Company's approach to developing targeted therapies, from target identification and validation through evaluation in the clinic. A selection of drugs in the Lilly Oncology pipeline is also discussed.

  14. Evaluation of superplastic forming and co-diffusion bonding of Ti-6Al-4V titanium alloy expanded sandwich structures

    NASA Technical Reports Server (NTRS)

    Arvin, G. H.; Israeli, L.; Stolpestad, J. H.; Stacher, G. W.

    1981-01-01

    The application of the superplastic forming/diffusion bonding (SPF/DB) process to supersonic cruise research is investigated. The capability of an SPF/DB titanium structure to meet the structural requirements of the inner wing area of the NASA arrow-wing advanced supersonic transport design is evaluated. Selection of structural concepts and their optimization for minimum weight, SPF/DB process optimization, fabrication of representative specimens, and specimen testing and evaluation are described. The structural area used includes both upper and lower wing panels, where the upper wing panel is used for static compression strength evaluation and the lower panel, in tension, is used for fracture mechanics evaluations. The individual test specimens, cut from six large panels, consist of 39 static specimens, 10 fracture mechanics specimens, and one each full size panel for compression stability and fracture mechanics testing. Tests are performed at temperatures of -54 C (-65 F), room temperature, and 260 C (500 F).

  15. Preliminary study of raw material for calcium silicate/PVA coating on Ti-6Al-4V alloy

    SciTech Connect

    Azam, Farah 'Atiqah bt Abdul; Shamsudin, Roslinda

    2015-09-25

    Calcium silicate bioceramic was prepared from the rice husk and limestone resources using the sol gel method. The preparations of CaSiO{sub 3} formulation were differ from the previous study due CaO/SiO{sub 2} amount with 45:55 ratio. X-Ray Fluorescence analysis was carried out to clarify the amount of SiO{sub 2} and CaO content in the limestone and rice husk ash. The high amount of CaO was found in the limestone with the percentages of 97.22%, whereby 89% of SiO{sub 2} content of the rice husk ash. Several milling time were studied to obtain the optimized milling ti me and speed in progress to obtain nano size particle. The particle size analysis result confirms that increase in milling time does not certainly reduce the size of particle. The addition of 0.05% polyvinyl alcohol as a binder did not change the phases or composition of calcium silicates after examined by X-Ray diffraction analysis which make it suitable to be used as a binder for calcium silicate coating without changing the chemical structure.

  16. Reducing Wear of Steel Rolling Against Ti6Al4V Operating in Vacuum

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.

    2014-01-01

    This work was motivated by a qualification test of a mechanism for a space telescope. During the test undesired wear debris was formed. In this project alterative materials and coatings were tested with intent to reduce wear and debris when steel has a misaligned rolling contact against Ti6Al4V. Testing was done using a vacuum roller rig mimicking the mechanism's contact conditions. Ten configurations were tested. Most configurations resulted in significant debris. A sputtered 1-micrometer-thick nan-ocomposite molybdenum disulfide (MoS2) film provided the best wear protection. The best configuration made use of the MoS2 coating on both materials, and in preparing for sputtering the anodized Ti6Al4V working surface was smoothed using an ultrasonic process.

  17. Surface characterization and mechanical property evaluation of thermally oxidized Ti-6Al-4V

    SciTech Connect

    Biswas, Amit; Dutta Majumdar, Jyotsna

    2009-06-15

    The present study concerns development of a thin and adherent oxide film on the surface of Ti-6Al-4V by thermal oxidation. Thermal oxidation was carried out over a range of temperature between 400 to 600 deg. C and a time from 25 h to 60 h. A detailed characterization of the surface and cross section of the oxidized surface was carried out by optical/scanning electron microscopy and X-ray diffraction techniques. Finally, the mechanical properties of the oxidized surface in terms of microindentation hardness and wear resistance were evaluated as a function of oxidation parameters. Surface oxidation of Ti-6Al-4V at 600 deg. C for 36 h offered a defect free oxide scale with improved hardness and wear resistance.

  18. Evaluation of Ti-6Al-4V surface treatments for use with a polyphenylquinoxaline adhesive

    NASA Technical Reports Server (NTRS)

    Progar, D. J.

    1986-01-01

    Three surface treatments for Ti-6Al-4V adherends were evaluated using a thermoplastic polymer monoether polyphenylquinoxaline, MEPPQ, which had been shown in previous studies to have good potential as a high temperature adhesive for aerospace applications. Initial results based on long term thermal exposure at 232 C (450 F) using the phosphate-fluoride (PF) and chromic acid anodized (CAA) treatments with MEPPQ adhesive were not encouraging. A significant improvement in strength retention and a change in failure mode (cohesive) at 232 C (450F) was found for the SHA treated specimens compared to the PF and CAA treatments. Although an improvement in long term thermal durability was obtained with the SHA treatment of Ti-6Al-4V, an improved surface treatment with better long term durability is still required for aerospace applications.

  19. Evaluation of Ti-6Al-4V surface treatments for use with a polyphenylquinoxaline adhesive

    NASA Technical Reports Server (NTRS)

    Progar, Donald J.

    1987-01-01

    Three surface treatments for Ti-6Al-4V adherends were evaluated using a thermoplastic polymer monoether polyphenylquinoxaline, MEPPQ, which had been shown in previous studies to have good potential as a high temperature adhesive for aerospace applications. Initial results based on long term thermal exposure at 232 C (450 F) using the phosphate-fluoride (PF) and chromic acid anodized (CAA) treatments with MEPPQ adhesive were not encouraging. A significant improvement in strength retention and a change in failure mode (cohesive) at 232 C (450 F) was found for the SHA treated specimens compared to the PF and CAA treatments. Although an improvement in long term thermal durability was obtained with the SHA treatment of Ti-6Al-4V, an improved surface treatment with better long term durability is still required for aerospace applications.

  20. HOS cell adhesion on Ti6Al4V surfaces texturized by laser engraving

    NASA Astrophysics Data System (ADS)

    Sandoval Amador, A.; Carreño Garcia, H.; Escobar Rivero, P.; Peña Ballesteros, D. Y.; Estupiñán Duran, H. A.

    2016-02-01

    The cell adhesion of the implant is determinate by the chemical composition, topography, wettability, surface energy and biocompatibility of the biomaterial. In this work the interaction between human osteosarcoma HOS cells and textured Ti6Al4V surfaces were evaluated. Ti6Al4V surfaces were textured using a CO2 laser in order to obtain circular spots on the surfaces. Test surfaces were uncoated (C1) used as a control surface, and surfaces with points obtained by laser engraving, with 1mm spacing (C2) and 0.5mm (C3). The HOS cells were cultured in RPMI-1640 medium with 10% fetal bovine serum and 1% antibiotics. No cells toxicity after one month incubation time occurred. The increased cell adhesion and cell spreading was observed after 1, 3 and 5 days without significant differences between the sample surfaces (C2 and C3) and control (uncoated) at the end of the experiment.

  1. Global and Local Mechanical Properties of Autogenously Laser Welded Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Cao, Xinjin; Kabir, Abu Syed H.; Wanjara, Priti; Gholipour, Javad; Birur, Anand; Cuddy, Jonathan; Medraj, Mamoun

    2013-11-01

    Ti-6Al-4V sheets, 3.2-mm in thickness, were butt welded using a continuous wave 4 kW Nd:YAG laser welding system. The effect of two main process parameters, laser power and welding speed, on the joint integrity was characterized in terms of the joint geometry, defects, microstructure, hardness, and tensile properties. In particular, a digital image correlation technique was used to determine the local tensile properties of the welds. It was determined that a wide range of heat inputs can be used to fully penetrate the Ti-6Al-4V butt joints during laser welding. At high laser power levels, however, significant defects such as underfill and porosity, can occur and cause marked degradation in the joint integrity and performance. At low welding speeds, however, significant porosity occurs due to its growth and the potential collapse of instable keyholes. Intermediate to relatively high levels of heat input allow maximization of the joint integrity and performance by limiting the underfill and porosity defects. In considering the effect of the two main defects on the joint integrity, the underfill defect was found to be more damaging to the mechanical performance of the weldment than the porosity. Specifically, it was determined that the maximum tolerable underfill depth for Ti-6Al-4V is approximately 6 pct of the workpiece thickness, which is slightly stricter than the value of 7 pct specified in AWS D17.1 for fusion welding in aerospace applications. Hence, employing optimized laser process parameters allows the underfill depth to be maintained within the tolerable limit (6 pct), which in turn prevents degradation in both the weld strength and ductility. To this end, the ability to maintain weld ductility in Ti-6Al-4V by means of applying a high energy density laser welding process presents a significant advantage over conventional arc welding for the assembly of aerospace components.

  2. Novel CYP4V2 mutations associated with Bietti crystalline corneoretinal dystrophy in Chinese patients

    PubMed Central

    Tian, Rong; Wang, Shu-Ran; Wang, Jing; Chen, You-Xin

    2015-01-01

    AIM To analyze the CYP4V2 mutations in five unrelated Chinese patients with Bietti crystalline corneoretinal dystrophy (BCD) and to provide clinical features of these patients. BCD is a rare monogenic autosomal recessively inherited disorder characterized by the presence of crystals in the retina and retinal pigment epithelium atrophy. Mutations in the CYP4V2 gene have been found to be causative for BCD. METHODS Ophthalmic examinations were carried out in the affected individuals. Peripheral blood samples were collected and genomic DNA was extracted. All exons and flanking intronic regions of the CYP4V2 gene were amplified with polymerase chain reaction and screened for mutations by direct DNA sequencing. One hundred control chromosomes were also screened to exclude nonpathogenic polymorphisms. RESULTS Fundus examination revealed the presence of tiny yellowish-sparkling crystals at the posterior pole of the fundus and atrophy of the retinal pigment epithelium in all patients. Choroid neovascularization was noted in one patient. Five different CYP4V2 mutations were identified, including two missense mutations (p.F73L, p.R400H), two splice site mutations (c.802-8_810del17insGC, c.1091-2A>G), and one single base-pair deletion (p.T479TfsX7 or c.1437delC). The two splice site mutations were identified in three of the patients with BCD. Mutation p.T479TfsX7 was a novel mutation not observed in any of 100 ethnically matched control chromosomes. CONCLUSION Mutation c.802-8_810del17insGC and c.1091-2A>G are common mutations in Chinese patients with BCD. Our results expand the allelic heterogeneity of BCD. PMID:26085992

  3. Physical characteristics of Ti-6A1-4V implants fabricated by electrodischarge compaction.

    PubMed

    Okazaki, K; Lee, W H; Kim, D K; Kopczyk, R A

    1991-12-01

    Physical characteristics of a Ti-6A1-4V implant were evaluated following fabrication using a new electrodischarge compaction technique. Ti-6A1-4V atomized powders were loaded into Pyrex tubes (3.3 mm ID) and subjected to a high-voltage, high-current-density pulse in air for a period of less than 300 microseconds. Single pulses (1.0, 1.5, 2.0 and 2.5 KJ/grampowder) were applied from a capacitor bank (240, 480 or 720 microF) to produce solid core implants with porous surface layers. Implants were evaluated microscopically for core size, neck size, pore size, grain structure, and incorporated oxide film. Hardness was also evaluated. Implants were compared with Ti-6A1-4V commercial powders. Core size increased and pore size decreased with increases in energy and capacitance. The cores were composed of equiaxed grains which were free of oxide at the grain boundary. Porous layers, consisting of particles connected in three dimensions by necks, were free of oxide films at the connecting interfaces. Neck size increased with increases in input energy and capacitance. Hardness readings of the core, necks, and porous particles resulted in readings higher than or similar to control materials. Electrodischarge compaction did not alter the physical characteristics during compaction. PMID:1794992

  4. Evaluation of Biological Properties of Electron Beam Melted Ti6Al4V Implant with Biomimetic Coating In Vitro and In Vivo

    PubMed Central

    Wang, Cheng-Tao; Li, Guo-Chen; Lei, Wei; Zhang, Zhi-Yong; Wang, Lin

    2012-01-01

    Background High strength porous titanium implants are widely used for the reconstruction of craniofacial defects because of their similar mechanical properties to those of bone. The recent introduction of electron beam melting (EBM) technique allows a direct digitally enabled fabrication of patient specific porous titanium implants, whereas both their in vitro and in vivo biological performance need further investigation. Methods In the present study, we fabricated porous Ti6Al4V implants with controlled porous structure by EBM process, analyzed their mechanical properties, and conducted the surface modification with biomimetic approach. The bioactivities of EBM porous titanium in vitro and in vivo were evaluated between implants with and without biomimetic apatite coating. Results The physical property of the porous implants, containing the compressive strength being 163 - 286 MPa and the Young’s modulus being 14.5–38.5 GPa, is similar to cortical bone. The in vitro culture of osteoblasts on the porous Ti6Al4V implants has shown a favorable circumstance for cell attachment and proliferation as well as cell morphology and spreading, which were comparable with the implants coating with bone-like apatite. In vivo, histological analysis has obtained a rapid ingrowth of bone tissue from calvarial margins toward the center of bone defect in 12 weeks. We observed similar increasing rate of bone ingrowth and percentage of bone formation within coated and uncoated implants, all of which achieved a successful bridging of the defect in 12 weeks after the implantation. Conclusions This study demonstrated that the EBM porous Ti6Al4V implant not only reduced the stress-shielding but also exerted appropriate osteoconductive properties, as well as the apatite coated group. The results opened up the possibility of using purely porous titanium alloy scaffolds to reconstruct specific bone defects in the maxillofacial and orthopedic fields. PMID:23272208

  5. Fatigue performance of laser additive manufactured Ti-6Al-4V in very high cycle fatigue (VHCF) regime up to 109 cycles

    NASA Astrophysics Data System (ADS)

    Wycisk, Eric; Siddique, Shafaqat; Herzog, Dirk; Walther, Frank; Emmelmann, Claus

    2015-12-01

    Additive manufacturing technologies are in the process of establishing themselves as an alternative production technology to conventional manufacturing such as casting or milling. Especially laser additive manufacturing (LAM) enables the production of metallic parts with mechanical properties comparable to conventionally manufactured components. Due to the high geometrical freedom in LAM the technology enables the production of ultra-light weight designs and therefore gains increasing importance in aircraft and space industry. The high quality standards of these industries demand predictability of material properties for static and dynamic load cases. However, fatigue properties especially in the very high cycle fatigue regime until 109 cycles have not been sufficiently determined yet. Therefore this paper presents an analysis of fatigue properties of laser additive manufactured Ti-6Al-4V under cyclic tension-tension until 107 cycles and tension-compression load until 109 cycles. For the analysis of laser additive manufactured titanium alloy Ti-6Al-4V Woehler fatigue tests under tension-tension and tension-compression were carried out in the high cycle and very high cycle fatigue regime. Specimens in stress-relieved as well as hot-isostatic-pressed conditions were analyzed regarding crack initiation site, mean stress sensitivity and overall fatigue performance. The determined fatigue properties show values in the range of conventionally manufactured Ti-6Al-4V with particularly good performance for hot-isostatic-pressed additive-manufactured material. For all conditions the results show no conventional fatigue limit but a constant increase in fatigue life with decreasing loads. No effects of test frequency on life span could be determined. However, independently of testing principle, a shift of crack initiation from surface to internal initiation could be observed with increasing cycles to failure.

  6. The effect of ion implantation on tribology and hot rolling contact fatigue of Cr4Mo4Ni4V bearing steel

    NASA Astrophysics Data System (ADS)

    Jin, Jie; Chen, Yunbo; Gao, Kewei; Huang, Xiaolin

    2014-06-01

    The Cr4Mo4Ni4V bearing material was implanted by N + Zr dual element implantation process. The mechanical properties were investigated by nanohardness tests, friction and wear tests, as well as hot rolling contact fatigue life tests. The surface structures of the planted samples were studied by GXRD, AES, XPS and TEM tests. The results showed that the N + Zr implanted sample exhibits higher surface hardness, anti-friction and wear-resistance properties and resistance to hot contact fatigue. After implantation, amorphous phase, microcrystalline phase and new alloy phases are formed in implanted region. The new phases and structures take the important roles in improving the surface mechanical properties of the bearing material.

  7. A Novel Investigation of the Formation of Titanium Oxide Nanotubes on Thermally Formed Oxide of Ti-6Al-4V.

    PubMed

    Butt, Arman; Hamlekhan, Azhang; Patel, Sweetu; Royhman, Dmitry; Sukotjo, Cortino; Mathew, Mathew T; Shokuhfar, Tolou; Takoudis, Christos

    2015-10-01

    Traditionally, titanium oxide (TiO2) nanotubes (TNTs) are anodized on Ti-6Al-4V alloy (Ti-V) surfaces with native TiO2 (amorphous TiO2); subsequent heat treatment of anodized surfaces has been observed to enhance cellular response. As-is bulk Ti-V, however, is often subjected to heat treatment, such as thermal oxidation (TO), to improve its mechanical properties. Thermal oxidation treatment of Ti-V at temperatures greater than 200°C and 400°C initiates the formation of anatase and rutile TiO2, respectively, which can affect TNT formation. This study aims at understanding the TNT formation mechanism on Ti-V surfaces with TO-formed TiO2 compared with that on as-is Ti-V surfaces with native oxide. Thermal oxidation-formed TiO2 can affect TNT formation and surface wettability because TO-formed TiO2 is expected to be part of the TNT structure. Surface characterization was carried out with field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, water contact angle measurements, and white light interferometry. The TNTs were formed on control and 300°C and 600°C TO-treated Ti-V samples, and significant differences in TNT lengths and surface morphology were observed. No difference in elemental composition was found. Thermal oxidation and TO/anodization treatments produced hydrophilic surfaces, while hydrophobic behavior was observed over time (aging) for all samples. Reduced hydrophobic behavior was observed for TO/anodized samples when compared with control, control/anodized, and TO-treated samples. A method for improved surface wettability and TNT morphology is therefore discussed for possible applications in effective osseointegration of dental and orthopedic implants.

  8. Microstructure and mechanical behavior of porous Ti-6Al-4V parts obtained by selective laser melting.

    PubMed

    Sallica-Leva, E; Jardini, A L; Fogagnolo, J B

    2013-10-01

    Rapid prototyping allows titanium porous parts with mechanical properties close to that of bone tissue to be obtained. In this article, porous parts of the Ti-6Al-4V alloy with three levels of porosity were obtained by selective laser melting with two different energy inputs. Thermal treatments were performed to determine the influence of the microstructure on the mechanical properties. The porous parts were characterized by both optical and scanning electron microscopy. The effective modulus, yield and ultimate compressive strength were determined by compressive tests. The martensitic α' microstructure was observed in all of the as-processed parts. The struts resulting from the processing conditions investigated were thinner than those defined by CAD models, and consequently, larger pores and a higher experimental porosity were achieved. The use of the high-energy input parameters produced parts with higher oxygen and nitrogen content, their struts that were even thinner and contained a homogeneous porosity distribution. Greater mechanical properties for a given relative density were obtained using the high-energy input parameters. The as-quenched martensitic parts showed yield and ultimate compressive strengths similar to the as-processed parts, and these were greater than those observed for the fully annealed samples that had the lamellar microstructure of the equilibrium α+β phases. The effective modulus was not significantly influenced by the thermal treatments. A comparison between these results and those of porous parts with similar geometry obtained by selective electron beam melting shows that the use of a laser allows parts with higher mechanical properties for a given relative density to be obtained. PMID:23773976

  9. Microstructure and mechanical behavior of porous Ti-6Al-4V parts obtained by selective laser melting.

    PubMed

    Sallica-Leva, E; Jardini, A L; Fogagnolo, J B

    2013-10-01

    Rapid prototyping allows titanium porous parts with mechanical properties close to that of bone tissue to be obtained. In this article, porous parts of the Ti-6Al-4V alloy with three levels of porosity were obtained by selective laser melting with two different energy inputs. Thermal treatments were performed to determine the influence of the microstructure on the mechanical properties. The porous parts were characterized by both optical and scanning electron microscopy. The effective modulus, yield and ultimate compressive strength were determined by compressive tests. The martensitic α' microstructure was observed in all of the as-processed parts. The struts resulting from the processing conditions investigated were thinner than those defined by CAD models, and consequently, larger pores and a higher experimental porosity were achieved. The use of the high-energy input parameters produced parts with higher oxygen and nitrogen content, their struts that were even thinner and contained a homogeneous porosity distribution. Greater mechanical properties for a given relative density were obtained using the high-energy input parameters. The as-quenched martensitic parts showed yield and ultimate compressive strengths similar to the as-processed parts, and these were greater than those observed for the fully annealed samples that had the lamellar microstructure of the equilibrium α+β phases. The effective modulus was not significantly influenced by the thermal treatments. A comparison between these results and those of porous parts with similar geometry obtained by selective electron beam melting shows that the use of a laser allows parts with higher mechanical properties for a given relative density to be obtained.

  10. Low-melting-point titanium-base brazing alloys—part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4v substrate

    NASA Astrophysics Data System (ADS)

    Chang, E.; Chen, C.-H.

    1997-12-01

    Filler metal of a low-melting-point (917 °C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 °C for 2,4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed a plus intergranular β structure of Ti-6Al-4V substrate causes the lamellar Widmanstätten structure to form. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the metal brazed at 960 °C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the β phase to the substrate. In deaerated Hank’s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank’s solution, show similar corrosion behavior, irrespective of the brazing time.

  11. Time exposure studies on stress corrosion cracking of aluminum 2014-T6, aluminum 7075-T651, and titanium 6Al-4V

    NASA Technical Reports Server (NTRS)

    Terrell, J.

    1972-01-01

    The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 7075-T651 and titanium 6A1-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 6) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity). Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, a similar observation was not noted for titanium stressed specimens. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl); while they (both alloys) seem to resist stress corrosion cracking in methyl alcohol, ethyl alcohol, iso-propyl alcohol, and demineralized distilled water. Titanium 6A1-4V showed some evidence of susceptibility to SCC in methanol, while no such susceptibility was exhibited in ethanol, iso-propyl alcohol and demineralized distilled water.

  12. The influence of cell morphology on the compressive fatigue behavior of Ti-6Al-4V meshes fabricated by electron beam melting.

    PubMed

    Zhao, S; Li, S J; Hou, W T; Hao, Y L; Yang, R; Misra, R D K

    2016-06-01

    Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique.

  13. The influence of cell morphology on the compressive fatigue behavior of Ti-6Al-4V meshes fabricated by electron beam melting.

    PubMed

    Zhao, S; Li, S J; Hou, W T; Hao, Y L; Yang, R; Misra, R D K

    2016-06-01

    Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique. PMID:26878293

  14. Heat transfer and fluid flow during keyhole mode laser welding of tantalum, Ti 6Al 4V, 304L stainless steel and vanadium

    NASA Astrophysics Data System (ADS)

    Rai, R.; Elmer, J. W.; Palmer, T. A.; Roy, T. Deb

    2007-09-01

    Because of the complexity of several simultaneous physical processes, most heat transfer models of keyhole mode laser welding require some simplifications to make the calculations tractable. The simplifications often limit the applicability of each model to the specific materials systems for which the model is developed. In this work, a rigorous, yet computationally efficient, keyhole model is developed and tested on tantalum, Ti-6Al-4V, 304L stainless steel and vanadium. Unlike previous models, this one combines an existing model to calculate keyhole shape and size with numerical fluid flow and heat transfer calculations in the weld pool. The calculations of the keyhole profile involved a point-by-point heat balance at the keyhole walls considering multiple reflections of the laser beam in the vapour cavity. The equations of conservation of mass, momentum and energy are then solved in three dimensions assuming that the temperatures at the keyhole wall reach the boiling point of the different metals or alloys. A turbulence model based on Prandtl's mixing length hypothesis was used to estimate the effective viscosity and thermal conductivity in the liquid region. The calculated weld cross-sections agreed well with the experimental results for each metal and alloy system examined here. In each case, the weld pool geometry was affected by the thermal diffusivity, absorption coefficient, and the melting and boiling points, among the various physical properties of the alloy. The model was also used to better understand solidification phenomena and calculate the solidification parameters at the trailing edge of the weld pool. These calculations indicate that the solidification structure became less dendritic and coarser with decreasing weld velocities over the range of speeds investigated in this study. Overall, the keyhole weld model provides satisfactory simulations of the weld geometries and solidification sub-structures for diverse engineering metals and alloys.

  15. On the effect of deep-rolling and laser-peening on the stress-controlled low- and high-cycle fatigue behavior of Ti-6Al-4V at elevated temperatures up to 550?C

    SciTech Connect

    Ritchie, IAltenberger, RKNalla, YSano LWagner, RO

    2012-04-01

    The effect of surface treatment on the stress/life fatigue behavior of a titanium Ti-6Al-4V turbine fan blade alloy is investigated in the regime of 102 to 106 cycles to failure under fully reversed stress-controlled isothermal push-pull loading between 25? and 550?C at a frequency of 5 Hz. Specifically, the fatigue behavior was examined in specimens in the deep-rolled and laser-shock peened surface conditions, and compared to results on samples in the untreated (machined and stress annealed) condition. Although the fatigue resistance of the Ti-6Al-4V alloy declined with increasing test temperature regardless of surface condition, deep-rolling and laser-shock peening surface treatments were found to extend the fatigue lives by factors of more than 30 and 5-10, respectively, in the high-cycle and low-cycle fatigue regimes at temperatures as high as 550?C. At these temperatures, compressive residual stresses are essentially relaxed; however, it is the presence of near-surface work hardened layers, with a nanocystalline structure in the case of deep-rolling and dense dislocation tangles in the case of laser-shock peening, which remain fairly stable even after cycling at 450?-550?C, that provide the basis for the beneficial role of mechanical surface treatments on the fatigue strength of Ti-6Al-4V at elevated temperatures.

  16. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  17. ETV REPORT: REMOVAL OF CHEMICAL CONTAMINANTS IN DRINKING WATER – WATTS PREMIER INC. WP-4V DRINKING WATER TREATMENT SYSTEM

    EPA Science Inventory

    The Watts Premier WP-4V POU drinking water treatment system was tested for removal of aldicarb, benzene, cadmium, carbofuran, cesium, chloroform, dichlorvos, dicrotophos, fenamiphos, mercury, mevinphos, oxamyl, strontium, and strychnine. The WP-4V employs a reverse osmosis (RO) m...

  18. Identification of CYP4V2 mutation in 36 Chinese families with Bietti crystalline corneoretinal dystrophy.

    PubMed

    Yin, Xiaobei; Yang, Liping; Chen, Ningning; Cui, Hui; Zhao, Lin; Feng, Lina; Li, Aijun; Zhang, Huirong; Ma, Zhizhong; Li, Genlin

    2016-05-01

    Bietti crystalline corneoretinal dystrophy (BCD) is an inherited eye disease that is most common in the Chinese. It is caused by a mutation in the CYP4V2 gene. In this study, 43 Chinese BCD families were recruited; most patients manifested the characteristic phenotype of BCD, with 2 families initially misdiagnosed with retinitis pigmentosa. Five patients in our cohort presented with BCD and choroidal neovascularization (CNV), and 1 patient presented with typical BCD and abnormality in the terminals of both fingers and toes. A total of 17 pathogenic mutations involving 68 alleles were identified from 36 families using targeted exon sequencing and Sanger sequencing; we achieved a diagnostic rate of approximately 84%. Fifteen families were found to carry homozygous mutations, 17 families carried compound heterozygous mutations, and 4 families carried a single heterozygous mutation. Of the mutations identified, four variants c.802-8_810del17bpinsGC, c.802-8_810del17bpinsGT, c.992A > C (p.H331P), and c.1091-2A > G accounted for 71% of the mutations identified in CYP4V2. These mutations were hotspots in Chinese populations for BCD. Five among them were novel and predicted to be disease-causing, including c.65T > A (p.L22H), c.681_4delTGAG (p.S227Rfs*1), c.802-8_810del17bpinsGT, c.965_7delAAG (p.321delE), and c.994G > A (p.D332N). No apparent correlation between genotype and phenotype was identified. Our findings broaden the spectrum of CYP4V2 mutations that cause BCD and the phenotypic spectrum of the disease in Chinese families. These results will be useful for the genetic diagnosis of BCD, genetic consultation, and gene therapy in the future. PMID:26971461

  19. Adsorption of human fibrinogen and albumin onto hydrophobic and hydrophilic Ti6Al4V powder

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, Jesús; Gallardo-Moreno, Amparo M.; Bruque, José M.; González-Martín, M. Luisa

    2016-07-01

    Adsorption of proteins on solid surfaces has been widely studied because of its importance in various biotechnological, medical and technical applications, such as medical implants or biosensors. One of the main problems is the adsorption-induced conformational changes because they often modify the biological activity of the proteins, which is believed to be a key factor on the subsequent cellular adhesion. The aim of this work is the study of the adsorption of human fibrinogen (Fg) and human serum albumin (HSA) onto Ti6Al4V particles, commercially available on different size, that are used to elaborate scaffolds to provide structural support to cell proliferation, promoting tissue development and bone regeneration among others. The study was done through the analysis of the adsorption isotherms and the electrical characterization of surfaces after adsorption in terms of the zeta potential (ζ). From this analysis it seems that Fg adsorbs preferentially vertically oriented (end-on) and HSA moves sequentially over the surface of the Ti6Al4V particles through dimmer formation, allowing adsorption progress over this initial bilayer. The zeta potential values of both proteins remain constant when the monolayer is formed. The study also extends the analysis of both adsorption behaviour and ζ potential characterization factors to the influence of the substrate hydrophobicity as this property can be modified for the Ti6Al4V by irradiating it with ultraviolet light (UV-C) without changes on its chemical composition [1,2]. Differences at low protein concentrations were found for both isotherms and zeta-potential values.

  20. Mechanical evaluation of porous titanium (Ti6Al4V) structures with electron beam melting (EBM).

    PubMed

    Parthasarathy, Jayanthi; Starly, Binil; Raman, Shivakumar; Christensen, Andy

    2010-04-01

    Patient specific porous implants for the reconstruction of craniofacial defects have gained importance due to their better performance over their generic counterparts. The recent introduction of electron beam melting (EBM) for the processing of titanium has led to a one step fabrication of porous custom titanium implants with controlled porosity to meet the requirements of the anatomy and functions at the region of implantation. This paper discusses an image based micro-structural analysis and the mechanical characterization of porous Ti6Al4V structures fabricated using the EBM rapid manufacturing process. SEM studies have indicated the complete melting of the powder material with no evidence of poor inter-layer bonding. Micro-CT scan analysis of the samples indicate well formed titanium struts and fully interconnected pores with porosities varying from 49.75%-70.32%. Compression tests of the samples showed effective stiffness values ranging from 0.57(+/-0.05)-2.92(+/-0.17)GPa and compressive strength values of 7.28(+/-0.93)-163.02(+/-11.98)MPa. For nearly the same porosity values of 49.75% and 50.75%, with a variation in only the strut thickness in the sample sets, the compressive stiffness and strength decreased significantly from 2.92 GPa to 0.57 GPa (80.5% reduction) and 163.02 MPa to 7.28 MPa (93.54 % reduction) respectively. The grain density of the fabricated Ti6Al4V structures was found to be 4.423 g/cm(3) equivalent to that of dense Ti6Al4V parts fabricated using conventional methods. In conclusion, from a mechanical strength viewpoint, we have found that the porous structures produced by the electron beam melting process present a promising rapid manufacturing process for the direct fabrication of customized titanium implants for enabling personalized medicine.

  1. Overcharge Protection for 4 V Lithium Batteries at High Rates and Low Temperature

    SciTech Connect

    Chen, Guoying; Richardson, Thomas J.

    2010-01-04

    Overcharge protection for 4 V Li{sub 1.05}Mn{sub 1.95}O{sub 4}/lithium cells at charging rates in excess of 1 mA/cm{sup 2} (3C) and at temperatures as low as -20 C was achieved using a bilayer separator coated with two electroactive polymers. High rate and low temperature overcharge protection and discharge performance were improved by employing a design in which the polymer-coated portion of the separator is in parallel with the cell rather than between the electrodes. The effects of different membrane supports for the electroactive polymers are also examined.

  2. Microstructural Evolution of Ti-6Al-4V during High Strain Rate Conditions of Metal Cutting

    NASA Technical Reports Server (NTRS)

    Dong, Lei; Schneider, Judy

    2009-01-01

    The microstructural evolution following metal cutting was investigated within the metal chips of Ti-6Al-4V. Metal cutting was used to impose a high strain rate on the order of approx.10(exp 5)/s within the primary shear zone as the metal was removed from the workpiece. The initial microstructure of the parent material (PM) was composed of a bi-modal microstructure with coarse prior grains and equiaxed primary located at the boundaries. After metal cutting, the microstructure of the metal chips showed coarsening of the equiaxed primary grains and lamellar. These metallographic findings suggest that the metal chips experienced high temperatures which remained below the transus temperature.

  3. Laser Surface Preparation for Adhesive Bonding of Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Belcher, Marcus A.; List, Martina S.; Wohl, Christopher J.; Ghose, Sayata; Watson, Kent A.; Hopkins, John W.; Connell, John W.

    2010-01-01

    Adhesively bonded structures are potentially lighter in weight than mechanically fastened ones, but existing surface treatments are often considered unreliable. Two main problems in achieving reproducible and durable adhesive bonds are surface contamination and variability in standard surface preparation techniques. In this work three surface pretreatments were compared: laser etching with and without grit blasting and conventional Pasa-Jell treatment. Ti-6Al-4V surfaces were characterized by contact angle goniometry, optical microscopy, and X-ray photoelectron spectroscopy (XPS). Laser -etching was found to produce clean surfaces with precisely controlled surface topographies and PETI-5 lap shear strengths and durabilities were equivalent to those produced with Pasa-Jell.

  4. SOD1A4V-mediated ALS: absence of a closely linked modifier gene and origination in Asia.

    PubMed

    Broom, W J; Johnson, D V; Auwarter, K E; Iafrate, A J; Russ, C; Al-Chalabi, A; Sapp, P C; McKenna-Yasek, D; Andersen, P M; Brown, R H

    2008-01-17

    Familial amyotrophic lateral sclerosis (ALS) accounts for 10% of all ALS. Approximately 20% of cases are due to mutations in the Cu/Zn superoxide dismutase gene (SOD1). In North America, SOD1(A4V) is the most common SOD1 mutation. Carriers of the SOD1(A4V) mutation share a common phenotype with rapid disease progression and death on average occurring at 1.4 years (versus 3-5 years with other dominant SOD1 mutations). Previous studies of SOD1(A4V) carriers identified a common haplotype around the SOD1 locus, suggesting a common founder for most SOD1(A4V) patients. In the current study we sequenced the entire common haplotypic region around SOD1 to test the hypothesis that polymorphisms in either previously undescribed coding regions or non-coding regions around SOD1 are responsible for the more aggressive phenotype in SOD1(A4V)-mediated ALS. We narrowed the conserved region around the SOD1 gene in SOD1(A4V) ALS to 2.8Kb and identified five novel SNPs therein. None of these variants was specifically found in all SOD1(A4V) patients. It therefore appears likely that the aggressive nature of the SOD1(A4V) mutation is not a result of a modifying factor within the region around the SOD1 gene. Founder analysis estimates that the A4V mutation occurred 540 generations (approximately 12,000 years) ago (95% CI 480-700). The conserved minimal haplotype is statistically more similar to Asian than European population DNA sets, suggesting that the A4V mutation arose in native Asian-Americans who reached the Americas through the Bering Strait. PMID:18055113

  5. A Study on the Laser Spatter and the Oxidation Reactions During Selective Laser Melting of 316L Stainless Steel, Al-Si10-Mg, and Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Simonelli, Marco; Tuck, Chris; Aboulkhair, Nesma T.; Maskery, Ian; Ashcroft, Ian; Wildman, Ricky D.; Hague, Richard

    2015-09-01

    The creation of an object by selective laser melting (SLM) occurs by melting contiguous areas of a powder bed according to a corresponding digital model. It is therefore clear that the success of this metal Additive Manufacturing (AM) technology relies on the comprehension of the events that take place during the melting and solidification of the powder bed. This study was designed to understand the generation of the laser spatter that is commonly observed during SLM and the potential effects that the spatter has on the processing of 316L stainless steel, Al-Si10-Mg, and Ti-6Al-4V. With the exception of Ti-6Al-4V, the characterization of the laser spatter revealed the presence of surface oxides enriched in the most volatile alloying elements of the materials. The study will discuss the implication of this finding on the material quality of the built parts.

  6. EliXR: an approach to eligibility criteria extraction and representation

    PubMed Central

    Wu, Xiaoying; Luo, Zhihui; Boland, Mary Regina; Theodoratos, Dimitri; Johnson, Stephen B

    2011-01-01

    Objective To develop a semantic representation for clinical research eligibility criteria to automate semistructured information extraction from eligibility criteria text. Materials and Methods An analysis pipeline called eligibility criteria extraction and representation (EliXR) was developed that integrates syntactic parsing and tree pattern mining to discover common semantic patterns in 1000 eligibility criteria randomly selected from http://ClinicalTrials.gov. The semantic patterns were aggregated and enriched with unified medical language systems semantic knowledge to form a semantic representation for clinical research eligibility criteria. Results The authors arrived at 175 semantic patterns, which form 12 semantic role labels connected by their frequent semantic relations in a semantic network. Evaluation Three raters independently annotated all the sentence segments (N=396) for 79 test eligibility criteria using the 12 top-level semantic role labels. Eight-six per cent (339) of the sentence segments were unanimously labelled correctly and 13.8% (55) were correctly labelled by two raters. The Fleiss' κ was 0.88, indicating a nearly perfect interrater agreement. Conclusion This study present a semi-automated data-driven approach to developing a semantic network that aligns well with the top-level information structure in clinical research eligibility criteria text and demonstrates the feasibility of using the resulting semantic role labels to generate semistructured eligibility criteria with nearly perfect interrater reliability. PMID:21807647

  7. ELiXIR—Solid-State Luminaire With Enhanced Light Extraction by Internal Reflection

    NASA Astrophysics Data System (ADS)

    Allen, Steven C.; Steckl, Andrew J.

    2007-06-01

    A phosphor-converted light-emitting diode (pcLED) luminaire featuring enhanced light extraction by internal reflection (ELiXIR) with efficacy of 60 lm/W producing 18 lumens of yellowish green light at 100 mA is presented. The luminaire consists of a commercial blue high power LED, a polymer hemispherical shell lens with interior phosphor coating, and planar aluminized reflector. High extraction efficiency of the phosphor-converted light is achieved by separating the phosphor from the LED and using internal reflection to steer the light away from lossy reflectors and the LED package and out of the device. At 10 and 500 mA, the luminaire produces 2.1 and 66 lumens with efficacies of 80 and 37 lm/W, respectively. Technological improvements over existing commercial LEDs, such as more efficient pcLED packages or, alternatively, higher efficiency green or yellow for color mixing, will be essential to achieving 150 200 lm/W solid-state lighting. Advances in both areas are demonstrated.

  8. Straight talk with...Stephen O'Brien. Interviewed by Elie Dolgin.

    PubMed

    O'Brien, Stephen

    2013-01-01

    Stephen O'Brien joined the US National Cancer Institute as a post doc in 1971 and climbed the ranks to become head of the institute's Laboratory of Genomic Diversity, a position he held for 25 years. But, after four decades at the government agency, O'Brien was ready for something new. In December 2011, he stepped down and took up a three-year, $5 million 'megagrant' in Russia through a program started a year earlier by the Russian Ministry of Education and Science to attract big-name researchers to work at least part-time in that country. O'Brien used his money to help launch the Theodosius Dobzhansky Center for Genome Bioinformatics at Saint Petersburg State University. Although O'Brien is a cancer researcher, he has diverse scientific interests. He led the team that discovered the CCR5-Δ32 mutation that confers resistance to HIV, and he has helped document the remarkable genetic uniformity of African cheetahs. Recently, he and two California scientists started the Genome 10K project, which aims to sequence the genetic blueprints of 10,000 vertebrate species. On a trip back to the US, O'Brien spoke with Elie Dolgin about how comparative genomics and his new Russian center will help advance the search for new therapeutics. PMID:23295996

  9. Mutational analysis of the human immunodeficiency virus type 1 Eli Nef function.

    PubMed Central

    Zazopoulos, E; Haseltine, W A

    1992-01-01

    The studies presented here define an internally consistent experimental system that permits systematic analysis of the effect of nef on the rate of the human immunodeficiency virus type 1 (HIV-1) replication in a CD4+ tumor T-cell line and in primary peripheral blood mononuclear cells. The parental full-length Nef protein, derived from the Eli strain of HIV-1, accelerates virus replication in both cell types. Mutations that destabilize or alter the intracellular location of the protein affect the ability of the Nef protein to accelerate virus replication. A set of mutants was made in amino acids proposed to be required for Nef function, including threonine and serine residues proposed to be targets for phosphorylation, and in sequences thought to resemble the G-1, G-3, and G-4 sites of the family of G proteins. In most cases alterations of the critical amino acids yield stable Nef proteins of parental phenotype. These results challenge the existing theories for the mechanism of Nef function. The results also identify two residues in the carboxyl half of the protein that are important for Nef function. Images PMID:1631166

  10. Benthic macroinvertebrate assemblages and sediment toxicity testing in the Ely Creek watershed restoration project

    SciTech Connect

    Soucek, D.J.; Currie, R.J.; Cherry, D.S.; Latimer, H.A.; Trent, G.C.

    1998-12-31

    The Ely Creek watershed in Lee County, Virginia, contains an abundance of abandoned mined land (AML) seeps that contaminate the majority of the creek and its confluence into Big Stone Creek. Contaminated sediments had high concentrations of iron ({approximately}10,000 mg/kg), aluminum ({approximately}1,500 mg/kg), magnesium ({approximately}400 mg/kg) and manganese ({approximately}150 mg/kg). Copper and zinc generally ranged from 3 to 20 mg/kg. Benthic macroinvertebrates surveys at six of 20 sites sampled in the watershed yielded no macroinvertebrates, while eight others had total abundances of 1 to 9 organisms. Four reference sites contained {ge}100 organisms and at least 14 different taxa. Laboratory, 10-day survival/impairment sediments tests with Daphnia magna did not support the field data. Mortality of 92 to 100% for D. magna occurred in samples collected from six cities. Daphnid reproduction was more sensitive than laboratory test organism survivorship; however, neither daphnid survivorship nor reproduction were good predictors of taxa richness. Laboratory test concerns included the use of a reference diluent water rather than site specific diluent water.

  11. Ultrafast beam dump materials and mirror coatings tested with the ELI beamlines LIDT test station

    NASA Astrophysics Data System (ADS)

    Durák, Michal; Kramer, Daniel; Velpula, Praveen K.; Cupal, Josef; Medřík, TomáÅ.¡; Hřebíček, Jan; Golasowski, Jiří; Peceli, Davorin; Fekete, Ladislav; Å tepán, Václav; Kozlová, Michaela; Rus, Bedřich

    2015-11-01

    The ELI Beamlines project will deliver ultrafast laser pulses with peak powers up to 10PW available every minute and PW class beams at 10Hz complemented by a 10TW 1kHz beamline. To properly determine damage thresholds of involved optical components in conditions similar to the operational environment and with expected laser parameters, a high vacuum LIDT test station was constructed at PALS facility. Our study presents results of ISO based S-on-1 and R-on-1 tests in femtosecond regime (50fs, 800nm, 10Hz/1kHz) performed on two different types of coatings: a) highabsorption black coatings with low outgassing rates, intended for use as a beam dump surface; and b) high-reflectivity, low-dispersion 45° AOI ultrafast mirror coatings. Testing of absorptive coatings was accompanied with QMS residual gas analysis to verify, that high intensity laser radiation approaching the damage threshold does not increase concentration of volatile organic compounds in the vacuum chamber. In case of HR mirror coatings, we also investigate the effect of cleaning on LIDT value, comparing characteristic S-on-1 curves of given sample with values obtained after 12h immersion in ethanol-water solution.

  12. Mechanical behaviour of pressed and sintered titanium alloys obtained from master alloy addition powders.

    PubMed

    Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

    2012-11-01

    The fabrication of the workhorse Ti-6Al-4V alloy and of the Ti-3Al-2.5V alloy was studied considering the master alloy addition variant of the blending elemental approach conventionally used for titanium powder metallurgy. The powders were characterised by means thermal analysis and X-ray diffraction and shaped by means of uniaxial pressing. The microstructural evolution with the sintering temperature (900-1400 °C) was evaluated by SEM and EDS was used to study the composition. XRD patterns as well as the density by Archimedes method were also obtained. The results indicate that master alloy addition is a suitable way to fabricate well developed titanium alloy but also to produce alloy with the desired composition, not available commercially. Density of 4.3 g/cm³ can be obtained where a temperature higher than 1200 °C is needed for the complete diffusion of the alloying elements. Flexural properties comparable to those specified for wrought Ti-6Al-4V medical devices are, generally, obtained.

  13. The Development of Titanium Alloys for Application in the Space Shuttle Main Engine

    NASA Technical Reports Server (NTRS)

    Halchak, John A.; Jerman, Gregory A.; Zimmerman, Frank R.

    2010-01-01

    The high-strength-to-weight ratio of titanium alloys, particularly at cryogenic temperatures, make them attractive for application in rocket engines - offering the potential of superior performance while minimizing component weight. This was particularly attractive for rotating components, such as pump impellers, where titanium alloys presented the potential to achieve a major advance in rotational tip speed, with a reduction in stages and resultant saving in pump weight and complexity. The investigation into titanium alloys for application in cryogenic turbopumps began in the early 1960's. However, it was found that the reactivity of titanium limited applications and produced unique processing challenges. Specialized chemical compositions and processing techniques had to be developed. A substantial amount of material properties testing and trials in experimental turbopumps occurred, ultimately leading to application in the Space Shuttle Main Engine. One particular alloy stood out for use at liquid hydrogen temperatures, Ti-5Al-2.5Sn ELI. This alloy was employed for several critical components. This presentation deals with the development effort, the challenges that were encountered and operational experiences with Ti-5Al-2.5Sn ELI in the SSME.

  14. Evaluation of Interfacial Interactions Between Ti-6Al-4V and Mold Use Ti-Added Backup Coat in Investment Casting

    NASA Astrophysics Data System (ADS)

    Cheng, Xu; Chai, Lianjing; Wu, Guoqing; Wang, Hong; Nan, Hai

    2016-05-01

    In this article, the chemical inertness of shell using Ti-added mullite backup coat against molten Ti-6Al-4V (Ti64) alloy was investigated. The metal/shell interfacial microstructures and compositions were characterized using an optical microscope, scanning electron microscope, roughness tester, and X-ray diffractometer; the hardened layer thickness was evaluated using a microhardness tester. By adding titanium powder into the mullite backup coat, the alpha case and hardened layer thickness of the Ti64 castings were largely reduced with good surface finishing. Silicon ions, from the backup coat, penetrated into the alloy and coarsened the β lath at the metal/shell interfacial area. The Ti powder in the mullite backup coat oxidized and interacted with silica during mold firing and casting, which reduced the silicon and oxygen concentrations at the metal/shell interfacial area. The oxygen penetration depth is thicker than the alpha case layer thickness, and around 0.26 wt pct, oxygen can obviously coarsen the alpha lath at the metal/shell interfacial area during investment casting.

  15. Examination of the distribution of the tensile deformation systems in tension and tension-creep of Ti-6Al-4V (wt.%) at 296 K and 728 K

    NASA Astrophysics Data System (ADS)

    Li, H.; Boehlert, C. J.; Bieler, T. R.; Crimp, M. A.

    2015-03-01

    The deformation behaviour of an α + β Ti-6Al-4V (wt.%) alloy was investigated during in situ deformation inside a scanning electron microscopy (SEM). Tensile experiments were performed at 296 and 728 K (~0.4Tm), while a tensile-creep experiment was performed at 728 K and 310 MPa (σ/σys = 0.74). The active deformation systems were identified using electron backscattered diffraction-based slip-trace analysis and SEM images of the specimen surface. The distribution of the active deformation systems varied as a function of temperature. Basal slip deformation played a major role in the tensile deformation behaviour, and the relative activity of basal slip increased with increasing temperature. For the 296 K tension deformation, basal slip was less active than prismatic slip, whereas this was reversed at 728 K. Twinning was observed in both the 296 and 728 K tension experiments; however, no more than 4% of the total deformation systems observed was twins. The tension-creep experiment revealed no slip traces, however grain boundary ledge formation was observed, suggesting that grain boundary sliding was an active deformation mechanism. The results of this work were compared with those from previous studies on commercially pure Ti, Ti-5Al-2.5Sn (wt.%) and Ti-8Al-1Mo-1V (wt.%), and the effects of alloying on the deformation behaviour are discussed. The relative amount of basal slip activity increased with increasing Al content.

  16. Electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification.

    PubMed

    Jeong, Yong-Hoon; Kim, Won-Gi; Choe, Han-Cheol

    2011-02-01

    In this study, the electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification has been researched using the potentiostat equipment. Cp-Ti and Ti-6Al-4V alloy, located on X-Y motorized stage, were irradiated using femtosecond laser. The corrosion properties were examined by a potentiodynamic and AC impedance test.

  17. Osteoblast differentiation and phenotype expressions on chitosan-coated Ti-6Al-4V.

    PubMed

    Lin, Hsin-Yi; Chen, Jing-Huei

    2013-09-12

    Chitosan (C), alginate-crosslinked chitosan (CA), and pectin-crosslinked chitosan (CP) were covalently bonded to Ti-6Al-4V surfaces and tested for their biocompatibility. Compared to the clinically treated Ti-6Al-4V surface (Ti64), C, CA, and CP, had higher contact angles and promoted higher cell proliferation, type I collagen deposition, and mineralization after two weeks (all p<0.05). Cells on C, CA, and CP expressed more alkaline phosphatase (ALP) activity compared to those on Ti64 (p<0.05). The swelling ratios and drug release efficacies of CA and CP were significantly higher and lower, respectively, than those of C (both p<0.05). Only cells on CA expressed ALP activity after three weeks of culture. Generally speaking, crosslinking with alginate and pectin changed surface wettability as well as the swelling and drug release properties of the chitosan coatings. Cells on the coatings had higher proliferation, type I collagen deposition, and degree of mineralization compared to those on Ti64.

  18. EPR study of new defects in neutron irradiated KS-4V and KU1 fused silica

    NASA Astrophysics Data System (ADS)

    Lagomacini, J. C.; Bravo, D.; Martín, P.; Ibarra, A.; Martín, A.; López, F. J.

    2010-11-01

    Electron paramagnetic resonance (EPR) studies have been carried out on high purity fused silica KS-4V (low OH content) and KU1 (high OH content), irradiated with fast neutrons (E > 0.1 MeV) at a high fluence of 1022 n/m2. The spectrum of irradiated samples shows various well-known types of paramagnetic defects, POR, NBOHC and E'. Their thermal stability has also been studied by heating the samples in air up to 775 °C. A detailed analysis of the spectra shows that the POR spectrum of neutron-irradiated KS-4V and KU1 has two contributions from centres POR(I) and POR(II), which show very different thermal annealing behaviour. POR(I) is identified with the POR centre previously reported, whereas POR(II) is associated to the effects of fast neutrons. Moreover, a new broad line centred at g = 2.02 is reported that we suggest could be associated to oxygen-hole centres in the neighbourhood of the high amount of tracks generated by ion displacement due to fast neutrons.

  19. Mechanical properties of Ti-6Al-4V specimens produced by shaped metal deposition

    NASA Astrophysics Data System (ADS)

    Baufeld, Bernd; van der Biest, Omer

    2009-01-01

    Shaped metal deposition is a novel technique to build near net-shape components layer by layer by tungsten inert gas welding. Especially for complex shapes and small quantities, this technique can significantly lower the production cost of components by reducing the buy-to-fly ratio and lead time for production, diminishing final machining and preventing scrap. Tensile testing of Ti-6Al-4V components fabricated by shaped metal deposition shows that the mechanical properties are competitive to material fabricated by conventional techniques. The ultimate tensile strength is between 936 and 1014 MPa, depending on the orientation and location. Tensile testing vertical to the deposition layers reveals ductility between 14 and 21%, whereas testing parallel to the layers gives a ductility between 6 and 11%. Ultimate tensile strength and ductility are inversely related. Heat treatment within the α+β phase field does not change the mechanical properties, but heat treatment within the β phase field increases the ultimate tensile strength and decreases the ductility. The differences in ultimate tensile strength and ductility can be related to the α lath size and orientation of the elongated, prior β grains. The micro-hardness and Young's modulus are similar to conventional Ti-6Al-4V with low oxygen content.

  20. Effect of inflammatory conditions and H2O2 on bare and coated Ti-6Al-4V surfaces: Corrosion behavior, metal ion release and Ca-P formation under long-term immersion in DMEM

    NASA Astrophysics Data System (ADS)

    Höhn, Sarah; Virtanen, Sannakaisa

    2015-12-01

    The surface oxide film and calcium-phosphate (Ca-P) formation on Ti-6Al-4V during long-term immersion in biological environments play a decisive role for the biocompatibility of the implant. Hence, the aim of the study was to evaluate the corrosion resistance, metal ion release and Ca-P formation in DMEM under physiological conditions at pH values of 7.4 and in comparison under simulated inflammatory conditions with pH 5 and in presence of H2O2. Furthermore, the influence of the immersion conditions was investigated on different surface treatments: on bare Ti-6Al-4V, after anodization, and for TiO2 nanoparticle (NP) and hydroxyapatite (HA)-incorporated TiO2-NP coatings. In the absence of H2O2, the impedance response indicated a stable thin oxide film and Ca-P formation after 28 days or 56 days depending on the coating, while under inflammatory conditions the Ca-P formation on the surface is time-delayed and dissolution of the anodized oxide layer as well as selective etching of the β-phase and phase boundaries in case of the bare alloy occur. Electrochemical impedance spectroscopy (EIS), however, indicates a good general corrosion behavior in all cases. The quantities of Ti, Al and V released from the bare and coated Ti-6Al-4V alloy markedly increased with decreasing pH (pH ≤ 5). Although the rapid increase of metal release was observed for all samples at pH 5, the quantities were significantly higher for the bare and anodized alloy than after coating with TiO2-NP or HA.

  1. Copper Speciation in Variably Toxic Sediments at the Ely Copper Mine, Vermont, United States.

    PubMed

    Kimball, Bryn E; Foster, Andrea L; Seal, Robert R; Piatak, Nadine M; Webb, Samuel M; Hammarstrom, Jane M

    2016-02-01

    At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160-1200 times) and sediments (15-79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80-95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

  2. Copper Speciation in Variably Toxic Sediments at the Ely Copper Mine, Vermont, United States.

    PubMed

    Kimball, Bryn E; Foster, Andrea L; Seal, Robert R; Piatak, Nadine M; Webb, Samuel M; Hammarstrom, Jane M

    2016-02-01

    At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160-1200 times) and sediments (15-79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80-95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu. PMID:26734712

  3. Copper speciation in variably toxic sediments at the Ely Copper Mine, Vermont, United States

    USGS Publications Warehouse

    Kimball, Bryn E.; Foster, Andrea L.; Seal, Robert; Piatak, Nadine; Webb, Samuel M.; Hammarstrom, Jane M.

    2016-01-01

    At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160–1200 times) and sediments (15–79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80–95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

  4. Effects of geometric variables on rub characteristics of Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Wolak, J.; Wisander, D. W.

    1981-01-01

    Experiments simulating rub interactions between Ti-6Al-4V blade tips and various seal materials were conducted. The number of blade tips and the blade tip geometry were varied to determine their effects on rub forces and on wear phenomena. Contact was found to be quite unsteady for all blade tip geometries except for those incorporating deliberately rounded blade tips. The unsteady contact was characterized by long periods of rubbing contact and increasing blade tip that terminated in sudden rapid metal removal, sometimes accompanied by tearing and disruption of porous seal material under the rub surface. A model describing the blade tip loading is proposed and is based on the propagation of an elastic stress wave through the seal material as the seal material is dynamically compressed by the blade tip leading edge.

  5. Investigating the Effects of Pin Tool Design on Friction Stir Welded Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Rubisoff, H. A.; Querin, J. A.; Schneider, Judy A.; Magee, D.

    2009-01-01

    Friction stir welding (FSWing), a solid state joining technique, uses a non-consumable rotating pin tool to thermomechanically join materials. Heating of the weldment caused by friction and deformation is a function of the interaction between the pin tool and the work piece. Therefore, the geometry of the pin tool is in part responsible for the resulting microstructure and mechanical properties. In this study microwave sintered tungsten carbide (WC) pin tools with tapers and flats were used to FSW Ti-6Al-4V. Transverse sections of welds were mechanically tested, and the microstructure was characterized using optical microscopy (OM) and scanning election microscopy (SEM). X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD) were used to characterize the texture within the welds produced from the different pin tool designs.

  6. Internal Stress Plasticity-Creep due to Dynamic Hydrogen Gradients in Ti-6Al-4V

    SciTech Connect

    Schuh, C; Dunand, D C

    2001-09-10

    Internal-stress plasticity is a Newtonian creep mechanism which operates at low applied stress levels, when there is a concurrent internal stress. Common sources of internal stress are thermal-expansion or phase-transformation mismatch; in this work we explore the possibility of chemically-induced internal stresses. We report tensile creep experiments on the BCC {beta}-phase of Ti-6A1-4V, in which dynamic gradients of hydrogen concentration were introduced through cycling of the test atmosphere (between Ar/H{sub 2} mixture and pure Ar) under low applied stresses. Under these conditions, we observe Newtonian deformation at rates much higher than for constant-composition conditions, as expected for internal stress plasticity. Also, we present an analytical model which considers chemical, elastic, and creep strains during chemical cycling under stress, and find good agreement with the experimental results.

  7. Surface morphology of Ti-6Al-4V plate fabricated by vacuum selective laser melting

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Tsukamoto, M.; Yamashita, Y.

    2015-06-01

    A plate made of Ti-6Al-4V (Ti64) was built by vacuum selective laser melting (SLM) at a pressure of 10-2 Pa. The vacuum SLM system employed a single-mode fiber laser and three-axis galvanic mirror in order to form 3D metallic structure. In order to investigate the surface morphology on the fabricated plates, Vickers microhardness and surface roughness R a were measured. From the results, the Vickers microhardness of the fabricated plates was recorded at 391 HV, higher than the typical 340 HV for a Ti64 plate. It was also determined that crystal orientation was evaluated with X-ray diffraction. From the results, the crystal orientation of powder is composed mainly of martensitic alpha. Diffraction peaks corresponding to β (110) were detected in vacuum SLM processed samples.

  8. Finite element simulation of conventional and prestressed cutting of Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Peng, Ruitao; Tang, Xinzi; Tan, Yuanqiang; Liu, Xiongwei

    2013-05-01

    Titanium alloys are known as difficult-to-machine materials, chip morphology plays a predominant role in determining machinability and tool wear during the machining of titanium alloys. Based on the finite element analysis and experimental validation, the cutting processes in conventional cutting and prestressed cutting of titanium alloy ring parts were explored respectively. The Johnson-Cook model expressed by equivalent plastic strain flow stress is utilized to describe the constitutive properties. A ductile fracture criterion based on the strain energy is applied to model the crack initiation and evolution during the chip segmentation. Cutting force as well as distributions of stress, temperature and equivalent plastic strain along cutting time were numerically compared. The results indicate that in conventional cutting and prestressed cutting, chips show the similar characteristic of continuous and regular serrated shape. Initial stress distribution of workpiece was changed by prestress, which correspondingly leads to the alteration of stress distribution in the subsurface layer. Prestress hardly influences the distributions of temperature and equivalent plastic strain on workpiece. The cutting force curves share the same average amplitude and analogous undulating rhythm.

  9. Rapidly solidified titanium alloys by melt overflow

    NASA Technical Reports Server (NTRS)

    Gaspar, Thomas A.; Bruce, Thomas J., Jr.; Hackman, Lloyd E.; Brasmer, Susan E.; Dantzig, Jonathan A.; Baeslack, William A., III

    1989-01-01

    A pilot plant scale furnace was designed and constructed for casting titanium alloy strips. The furnace combines plasma arc skull melting techniques with melt overflow rapid solidification technology. A mathematical model of the melting and casting process was developed. The furnace cast strip of a suitable length and width for use with honeycomb structures. Titanium alloys Ti-6Al-4V and Ti-14Al-21 Nb were successfully cast into strips. The strips were evaluated by optical metallography, microhardness measurements, chemical analysis, and cold rolling.

  10. Characterization of the Ti-10Nb-10Zr-5Ta Alloy for Biomedical Applications. Part 1: Microstructure, Mechanical Properties, and Corrosion Resistance

    NASA Astrophysics Data System (ADS)

    Vladescu, A.; Braic, V.; Balaceanu, M.; Braic, M.; Parau, A. C.; Ivanescu, S.; Fanara, C.

    2013-08-01

    Ti-10Nb-10Zr-5Ta alloy was investigated as possible material candidate for replacing Ti6Al4V in medical applications. The alloy was prepared in a levitation melting furnace and characterized in terms of elemental and phase composition, microstructure, mechanical properties, and corrosion resistance in simulated body fluid and Fusayama Meyer artificial saliva solutions. The characteristics of the new alloy were compared to those of the Ti6Al4V alloy. The Ti-10Nb-10Zr-5Ta system was found to posses of a polyhedral structure consisting in α' and β phases. X-ray structural analysis revealed a mixture of hexagonal α' martensite (main phase, with grain size of about 21 nm) and β bcc phase. The Ti-10Nb-10Zr-5Ta alloy exhibited some better mechanical properties (Young modulus, tensile properties) and corrosion resistance (polarization resistance, corrosion current density, and corrosion rate), as compared to Ti6Al4V alloy.

  11. Hybrid diffusive/PVD treatments to improve the tribological resistance of Ti-6Al-4V.

    PubMed

    Marin, E; Offoiach, R; Lanzutti, A; Regis, M; Fusi, S; Fedrizzi, L

    2014-01-01

    Titanium alloys are nowadays used for a wide range of biomedical applications thanks to their combination of high mechanical resistance, high corrosion resistance and biocompatibility. Nevertheless, the applicability of titanium alloys is sometimes limited due to their low microhardness and tribological resistance. Thus the titanium alloys cannot be successfully applied to prosthetic joint couplings. A wide range of surface treatments, in particular PVD coatings such as CrN and TiN, have been used in order to improve the tribological behaviour of titanium alloys. However, the low microhardness of the titanium substrate often results in coating failure due to cracks and delamination. For this reason, hybrid technologies based on diffusive treatments and subsequent PVD coatings may improve the overall coating resistance. In this work, conventional PVD coatings of CrN or TiCN, deposited on Titanium Grade 5, were characterized and then combined with a standard thermal diffusive nitriding treatment in order to improve the tribological resistance of the titanium alloys and avoid coating delamination. The different treatments were studied by means of scanning electron microscopy both on the sample surface and in cross-section. In-depth composition profiles were obtained using glow discharge optical emission spectrometry (GDOES) and localized energy dispersive X-ray diffraction on linear scan-lines. The microhardness and adhesion properties of the different treatments were evaluated using Vickers microhardness tests at different load conditions. The indentations were observed by means of SEM in order to evaluate delaminated areas and the crack's shape and density. The tribological behaviour of the different treatments was tested in dry conditions and in solution, in alternate pin-on-flat configuration, with a frequency of 0.5 Hz. After testing, the surface was investigated by means of stylus profilometry and SEM both on the surface and in cross-section. The standalone PVD

  12. Fabrication of nano-structured HA/CNT coatings on Ti6Al4V by electrophoretic deposition for biomedical applications.

    PubMed

    Zhang, Bokai; Kwok, Chi Tat; Cheng, Fai Tsun; Man, Hau Chung

    2011-12-01

    In order to improve the bone bioactivity and osteointegration of metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. In the present study, cathodic electrophoretic deposition (EPD) has been attempted for depositing nanostructured HA coatings on titanium alloy Ti6Al4V followed by sintering at 800 degrees C. Nano-sized HA powder was used in the EPD process to produce dense coatings. Moreover, multiwalled carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its mechanical strength. The surface morphology, compositions and microstructure of the monolithic coating of HA and nanocomposite coatings of HA with different CNT contents (4 to 25%) on Ti6Al4V were investigated by scanning-electron microscopy, energy-dispersive X-ray spectroscopy and Xray diffractometry, respectively. Electrochemical corrosion behavior of the various coatings in Hanks' solution at 37 degrees C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. The HA and HA/CNT coatings had a thickness of about 10 microm, with corrosion resistance higher than that of the substrate and adhesion strength higher than that of plasma sprayed HA coating. The properties of the composite coatings were optimized by varying the CNT contents. The enhanced properties could be attributed to the use of nano-sized HA particles and CNTs. Compared with the monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness without deteriorating the corrosion resistance or adhesion strength.

  13. Integrated experimental and theoretical approach for corrosion and wear evaluation of laser surface nitrided, Ti-6Al-4V biomaterial in physiological solution.

    PubMed

    Vora, Hitesh D; Shanker Rajamure, Ravi; Dahotre, Sanket N; Ho, Yee-Hsien; Banerjee, Rajarshi; Dahotre, Narendra B

    2014-09-01

    A laser based surface nitriding process was adopted to further enhance the osseo-integration, corrosion resistance, and tribological properties of the commonly used bioimplant alloy, Ti-6Al-4V. Earlier preliminary osteoblast, electrochemical, and corrosive wear studies of laser nitrided titanium in simulated body fluid clearly revealed improvement of cell adhesion as well as enhancement in corrosion and wear resistance but mostly lacked the in-depth fundamental understanding behind these improvements. Therefore, a novel integrated experimental and theoretical approach were implemented to understand the physical phenomena behind the improvements and establish the property-structure-processing correlation of nitrided surface. The first principle and thermodynamic calculations were employed to understand the thermodynamic, electronic, and elastic properties of TiN for enthalpy of formation, Gibbs free energy, density of states, and elastic properties of TiN were investigated. Additionally, open circuit potential and cyclic potentio-dynamic polarization tests were carried out in simulated body fluid to evaluate the corrosion resistance that in turn linked with the experimentally measured and computationally predicted surface energies of TiN. From these results, it is concluded that the enhancement in the corrosion resistance after laser nitriding is mainly attributed to the presence of covalent bonding via hybridization among Ti (p) and N (d) orbitals. Furthermore, mechanical properties, such as, Poisson׳s ratio, stiffness, Pugh׳s ductility criteria, and Vicker׳s hardness, predicted from first principle calculations were also correlated to the increase in wear resistance of TiN. All the above factors together seem to have contributed to significant improvement in both wear and corrosion performance of nitride surface compared to the bare Ti-6Al-4V in physiological environment indicating its suitability for bioimplant applications.

  14. Evaluating the Effect of Processing Parameters on Porosity in Electron Beam Melted Ti-6Al-4V via Synchrotron X-ray Microtomography

    NASA Astrophysics Data System (ADS)

    Cunningham, Ross; Narra, Sneha P.; Ozturk, Tugce; Beuth, Jack; Rollett, A. D.

    2016-03-01

    Electron beam melting (EBM) is one of the subsets of direct metal additive manufacturing (AM), an emerging manufacturing method that fabricates metallic parts directly from a three-dimensional (3D) computer model by the successive melting of powder layers. This family of technologies has seen significant growth in recent years due to its potential to manufacture complex components with shorter lead times, reduced material waste and minimal post-processing as a "near-net-shape" process, making it of particular interest to the biomedical and aerospace industries. The popular titanium alloy Ti-6Al-4V has been the focus of multiple studies due to its importance to these two industries, which can be attributed to its high strength to weight ratio and corrosion resistance. While previous research has found that most tensile properties of EBM Ti-6Al-4V meet or exceed conventional manufacturing standards, fatigue properties have been consistently inferior due to a significant presence of porosity. Studies have shown that adjusting processing parameters can reduce overall porosity; however, they frequently utilize methods that give insufficient information to properly characterize the porosity (e.g., Archimedes' method). A more detailed examination of the result of process parameter adjustments on the size and spatial distribution of gas porosity was performed utilizing synchrotron-based x-ray microtomography with a minimum feature resolution of 1.5 µm. Cross-sectional melt pool area was varied systematically via process mapping. Increasing melt pool area through the speed function variable was observed to significantly reduce porosity in the part.

  15. Effects of Ca and H2O2 added to RPMI on the fretting corrosion of Ti6Al4V.

    PubMed

    Montague, A; Merritt, K; Brown, S; Payer, J

    1996-12-01

    Titanium and its alloys have demonstrated considerable success in various surgical procedures including orthopedic, dental, and cardiovascular surgery. However, particulate debris from corrosion and wear is present in a considerable quantity in tissue local to the implant. This study evaluated the effect of Ca, since it is present in both serum and bone, and H2O2, since it is produced through local inflammation, on the amount of titanium release. Four sets of Ti6Al4V plates and Ti6Al4V screws were used. Each set was designated to one of four solutions: RPMI (cell culture growth media), RPMI with CaCl2, RPMI with CaCO3, and RPMI with H2O2. A fretter was used to cause corrosion by creating micromotion between two screws and a two-hole plate of Ti6Al4V. After fretting for 72 h, weight loss of the plate and screws and the amount of Ti and vanadium (V) in solution was used to assess the amount of fretting corrosion which had occurred. Results of weight loss and Ti in solution indicated that the presence of H2O2 increased the amount of particulate debris produced in RPMI as compared with RPMI alone. The addition of CaCl2 to RPMI also increased both weight loss and Ti in solution compared with RPMI alone. The addition of CaCO2, however, did not give values significantly different from RPMI alone. Comparison of weight loss and Ti in solution indicated that the increase in fretting corrosion was not different between RPMI with CaCl2 and RPMI with H2O2. The particulate wear debris from the four solutions was black in color and the size of the particulate produced was compared using a Coulter Multisizer. The results indicated that particles produced in the four solutions were not different, with mean values between 1.324 and 1.100 microns, and they were similar in size to the particulate found in tissues surrounding failed total hip replacements. In order to better understand the role of Ca in the fretting corrosion of Ti6Al4V, energy dispersive x-ray analysis (EDXA) using

  16. Regulating Direct-to-Consumer Drug Information: A Case Study of Eli Lilly's Canadian 40over40 Erectile Dysfunction Campaign.

    PubMed

    Pipon, Jean-Christophe Bélisle; Williams-Jones, Bryn

    2015-05-01

    Like most jurisdictions, Canada prohibits direct-to-consumer advertising (DTCA) of prescribed drugs. However, direct-to-consumer information (DTCI) is permitted, allowing companies to inform the public about medical conditions. An analysis of Eli Lilly's 40over40 promotion campaign for erectile dysfunction (ED), which included a quiz on ED, shows that DTCI, like DTCA, can be an effective means of drug familiarization. The pharmaceutical industry is "playing by the rules" currently in effect in Canada. Regulators should thus seriously consider whether existing rules permitting DTCI actually meet stated objectives of protecting the public from marketing campaigns (i.e., DTCA) that may deliver misleading information.

  17. The effect of weld porosity on the cryogenic fatigue strength of ELI grade Ti-5Al-2.5Sn

    NASA Technical Reports Server (NTRS)

    Rogers, P. R.; Lambdin, R. C.; Fox, D. E.

    1992-01-01

    The effect of weld porosity on the fatigue strength of ELI grade Ti-5Al-2.5Sn at cryogenic temperature was determined. A series of high cycle fatigue (HCF) and tensile tests were performed at -320 F on specimens made from welded sheets of the material. All specimens were tested with weld beads intact and some amount of weld offset. Specimens containing porosity and control specimens containing no porosity were tested. Results indicate that for the weld configuration tested, the fatigue life of the material is not affected by the presence of spherical embedded pores.

  18. Regulating Direct-to-Consumer Drug Information: A Case Study of Eli Lilly's Canadian 40over40 Erectile Dysfunction Campaign.

    PubMed

    Pipon, Jean-Christophe Bélisle; Williams-Jones, Bryn

    2015-05-01

    Like most jurisdictions, Canada prohibits direct-to-consumer advertising (DTCA) of prescribed drugs. However, direct-to-consumer information (DTCI) is permitted, allowing companies to inform the public about medical conditions. An analysis of Eli Lilly's 40over40 promotion campaign for erectile dysfunction (ED), which included a quiz on ED, shows that DTCI, like DTCA, can be an effective means of drug familiarization. The pharmaceutical industry is "playing by the rules" currently in effect in Canada. Regulators should thus seriously consider whether existing rules permitting DTCI actually meet stated objectives of protecting the public from marketing campaigns (i.e., DTCA) that may deliver misleading information. PMID:26142356

  19. Regulating Direct-to-Consumer Drug Information: A Case Study of Eli Lilly's Canadian 40over40 Erectile Dysfunction Campaign

    PubMed Central

    Williams-Jones, Bryn

    2015-01-01

    Like most jurisdictions, Canada prohibits direct-to-consumer advertising (DTCA) of prescribed drugs. However, direct-to-consumer information (DTCI) is permitted, allowing companies to inform the public about medical conditions. An analysis of Eli Lilly's 40over40 promotion campaign for erectile dysfunction (ED), which included a quiz on ED, shows that DTCI, like DTCA, can be an effective means of drug familiarization. The pharmaceutical industry is “playing by the rules” currently in effect in Canada. Regulators should thus seriously consider whether existing rules permitting DTCI actually meet stated objectives of protecting the public from marketing campaigns (i.e., DTCA) that may deliver misleading information. PMID:26142356

  20. Spherical nanoindentation stress-strain curves of commercially pure titanium and Ti-6Al-4V

    DOE Data Explorer

    Weaver, Jordan S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Priddy, Matthew W. [Georgia Inst. of Technology, Atlanta, GA (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidindi, Surya R. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-07-27

    Spherical nanoindentation combined with electron back-scattered diffraction was employed to characterize the grain-sca