Influence of Mg on Grain Refinement of Near Eutectic Al-Si Alloys

NASA Astrophysics Data System (ADS)

Ravi, K. R.; Manivannan, S.; Phanikumar, G.; Murty, B. S.; Sundarraj, Suresh

2011-07-01

Although the grain-refinement practice is well established for wrought Al alloys, in the case of foundry alloys such as near eutectic Al-Si alloys, the underlying mechanisms and the use of grain refiners need better understanding. Conventional grain refiners such as Al-5Ti-1B are not effective in grain refining the Al-Si alloys due to the poisoning effect of Si. In this work, we report the results of a newly developed grain refiner, which can effectively grain refine as well as modify eutectic and primary Si in near eutectic Al-Si alloys. Among the material choices, the grain refining response with Al-1Ti-3B master alloy is found to be superior compared to the conventional Al-5Ti-1B master alloy. It was also found that magnesium additions of 0.2 wt pct along with the Al-1Ti-3B master alloy further enhance the near eutectic Al-Si alloy's grain refining efficiency, thus leading to improved bulk mechanical properties. We have found that magnesium essentially scavenges the oxygen present on the surface of nucleant particles, improves wettability, and reduces the agglomeration tendency of boride particles, thereby enhancing grain refining efficiency. It allows the nucleant particles to act as potent and active nucleation sites even at levels as low as 0.2 pct in the Al-1Ti-3B master alloy.

3-Dimensional Microstructure of Al-Al3Ti Alloy Severely Deformed by ECAP

NASA Astrophysics Data System (ADS)

Sato, Hisashi; Hishikawa, Takahisa; Makino, Yuuki; Kunimine, Takahiro; Watanabe, Yoshimi

Microstructure of Al-Al3Ti alloy deformed by Equal-Channel-Angular Pressing (ECAP) is 3-dimensionally investigated. Especially, distribution of Al3Ti particles is focused in this study. The Al-Al3Ti alloy has coarse Al3Ti platelet particles in α-Al matrix. When the Al-Al3Ti alloy is deformed by ECAP under route A, fine Al3Ti platelet particles are observed. These Al3Ti platelet particles are aligned along to deformation axis, and its plane normal is perpendicular to the deformation axis. On the other hand, Al-Al3Ti alloy ECAPed under route Bc forms several groups consisted of fine Al3Ti platelet particles. Moreover, longitudinal size of the Al3Ti particle groups is close to that of initial Al3Ti particles with 4-pass ECAP specimen. These distribution behaviors of the Al3Ti particle can be explained by plastic flow of α-Al matrix. Finally, it is concluded that distribution of Al3Ti particle in Al-Al3Ti alloy by ECAP is controlled by plastic deformation of α-Al matrix.

Evaluation of the mechanical properties of powder metallurgy Ti-6Al-7Nb alloy.

PubMed

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

2017-03-01

Titanium and its alloys are common biomedical materials owing to their combination of mechanical properties, corrosion resistance and biocompatibility. Powder metallurgy (PM) techniques can be used to fabricate biomaterials with tailored properties because changing the processing parameters, such as the sintering temperature, products with different level of porosity and mechanical performances can be obtained. This study addresses the production of the biomedical Ti-6Al-7Nb alloy by means of the master alloy addition variant of the PM blending elemental approach. The sintering parameters investigated guarantee that the complete diffusion of the alloying elements and the homogenization of the microstructure is achieved. The sintering of the Ti-6Al-7Nb alloy induces a total shrinkage between 7.4% and 10.7% and the level of porosity decreases from 6.2% to 4.7% with the increment of the sintering temperature. Vickers hardness (280-300 HV30) and tensile properties (different combination of strength and elongation around 900MPa and 3%) are achieved. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Comparison of the Behaviour of AlTiB and AlTiC Grain Refiners

NASA Astrophysics Data System (ADS)

Schneider, W.; Kearns, M. A.; McGarry, M. J.; Whitehead, A. J.

AlTiC master alloys present a new alternative to AlTiB grain refiners which have enjoyed pre-eminence in cast houses for several decades. Recent investigations have shown that, under defined casting conditions, AlTiC is a more efficient grain refiner than AlTiB, is less prone to agglomeration and is more resistant to poisoning by Zr, Cr. Moreover it is observed that there are differences in the mechanism of grain refinement for the different alloys. This paper describes the influence of melt temperature and addition rate on the performance of both types of grain refiner in DC casting tests on different wrought alloys. Furthermore the effects of combined additions of the grain refiners and the recycling behaviour of the treated alloys are presented. Results are compared with laboratory test data. Finally, mechanisms of grain refinement are discussed which are consistent with the observed differences in behaviour with AlTiC and AlTiB.

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.

Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB2 Composites Produced by Direct Metal Laser Sintering (DMLS)

NASA Astrophysics Data System (ADS)

Lorusso, Massimo; Aversa, Alberta; Manfredi, Diego; Calignano, Flaviana; Ambrosio, Elisa Paola; Ugues, Daniele; Pavese, Matteo

2016-08-01

Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB2 composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB2, 1% wt. of nanosize TiB2. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB2 reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.

Microstructural evolution of single Ni 2TiAl or hierarchical NiAl/Ni 2 TiAl precipitates in Fe-Ni-Al-Cr-Ti ferritic alloys during thermal treatment for elevated-temperature applications

DOE PAGES

Song, Gian; Sun, Zhiqian; Poplawsky, Jonathan D.; ...

2017-01-07

Precipitate features, such as the size, morphology, and distribution, are important parameters determining the mechanical properties of semi- or fully-coherent precipitatehardened alloys at elevated temperatures. In this study, the microstructural formation and evolution of recently-developed Fe-Ni-Al-Cr-Ti alloys with superior creep resistance have been systematically investigated using transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), and atom-probe tomography (APT). These alloys were designed by adding 2 or 4 weight percent (wt. %) Ti into a NiAl-hardened ferritic alloy with a nominal composition of Fe-6.5Al-10Cr-10Ni-3.4Mo-0.25Zr-0.005B in wt. %. These alloys were, then, subjected to a homogenization treatment at 1,473 K for 0.5 hour, followedmore » by aging treatments at 973 K for 1 ~ 500 hours. In the homogenization-treated case, both alloys contain a primary L21-type Ni 2TiAl precipitate, but with the distinct size and morphology of the precipitates and precipitate/matrix interface structures. In the subsequent aging treatments, the 2 wt. % Ti alloy establishes a hierarchical-precipitate structure consisting of a fine network of a B2-type NiAl phase within the parent L2 1-type Ni2TiAl precipitate, while the 4 wt. % Ti alloy retains the single Ni 2TiAl precipitate. It was found that the hierarchical structure is more effective in remaining the coherent interface during the growth/coarsening of the precipitate. The formation of the different types of the precipitates, and their effects on the microstructural evolution are discussed, and the driving forces for these features are identified from the competition between the interface energy and elastic interactions due to the lattice misfit and misfit dislocations.« less

Microstructural evolution of single Ni 2TiAl or hierarchical NiAl/Ni 2 TiAl precipitates in Fe-Ni-Al-Cr-Ti ferritic alloys during thermal treatment for elevated-temperature applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Sun, Zhiqian; Poplawsky, Jonathan D.

Precipitate features, such as the size, morphology, and distribution, are important parameters determining the mechanical properties of semi- or fully-coherent precipitatehardened alloys at elevated temperatures. In this study, the microstructural formation and evolution of recently-developed Fe-Ni-Al-Cr-Ti alloys with superior creep resistance have been systematically investigated using transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), and atom-probe tomography (APT). These alloys were designed by adding 2 or 4 weight percent (wt. %) Ti into a NiAl-hardened ferritic alloy with a nominal composition of Fe-6.5Al-10Cr-10Ni-3.4Mo-0.25Zr-0.005B in wt. %. These alloys were, then, subjected to a homogenization treatment at 1,473 K for 0.5 hour, followedmore » by aging treatments at 973 K for 1 ~ 500 hours. In the homogenization-treated case, both alloys contain a primary L21-type Ni 2TiAl precipitate, but with the distinct size and morphology of the precipitates and precipitate/matrix interface structures. In the subsequent aging treatments, the 2 wt. % Ti alloy establishes a hierarchical-precipitate structure consisting of a fine network of a B2-type NiAl phase within the parent L2 1-type Ni2TiAl precipitate, while the 4 wt. % Ti alloy retains the single Ni 2TiAl precipitate. It was found that the hierarchical structure is more effective in remaining the coherent interface during the growth/coarsening of the precipitate. The formation of the different types of the precipitates, and their effects on the microstructural evolution are discussed, and the driving forces for these features are identified from the competition between the interface energy and elastic interactions due to the lattice misfit and misfit dislocations.« less

Corrosion behaviour of Al-Fe-Ti-V medium entropy alloy

NASA Astrophysics Data System (ADS)

Bodunrin, M. O.; Obadele, B. A.; Chown, L. H.; Olubambi, P. A.

2017-12-01

Alloys containing up to four multi-principal elements in equiatomic ratios are referred to as medium entropy alloys (MEA). These alloys have attracted the interest of many researchers due to the superior mechanical properties it offers over the traditional alloys. The design approach of MEA often results to simple solid solution with either body centered cubic; face centered cubic structures or both. As the consideration for introducing the alloys into several engineering application increases, there have been efforts to study the corrosion behaviour of these alloys. Previous reports have shown that some of these alloys are more susceptible to corrosion when compared with traditional alloys due to lack of protective passive film. In this research, we have developed AlFeTiV medium entropy alloys containing two elements (Ti and Al) that readily passivate when exposed to corrosive solutions. The alloys were produced in vacuum arc furnace purged with high purity argon. Open circuit potential and potentiodynamic polarisation tests were used to evaluate the corrosion behaviour of the as-cast AlFeTiV alloy in 3.5 wt% NaCl and 1 M H2SO4. The corrosion performance of the alloy was compared with Ti-6Al-4V alloy tested under similar conditions. The results show that unlike in Ti-6Al-4V alloy, the open circuit potential of the AlFeTiV alloy move towards the negative values in both 3.5 wt% NaCl and 1 M H2SO4 solutions indicating that self-activation occurred rapidly on immersion. Anodic polarisation of the alloys showed that AlFeTiV alloy exhibited a narrow range of passivity in both solutions. In addition, the alloys exhibited lower Ecorr and higher Icorr when compared with traditional Ti-6Al-4V alloy. The traditional Ti-6Al-4V alloy showed superior corrosion resistant to the AlFeTiV alloy in both 3.5 wt.% NaCl and 1 M H2SO4 solutions.

Phase Constituents and Microstructure of Ti3Al/Fe3Al + TiN/TiB2 Composite Coating on Titanium Alloy

NASA Astrophysics Data System (ADS)

Li, Jianing; Chen, Chuanzhong; Zhang, Cuifang

Laser cladding of the Fe3Al + B4C/TiN + Al2O3 pre-placed powders on the Ti-6Al-4V alloy can form the Ti3Al/Fe3Al + TiN/TiB2 composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti3Al/Fe3Al + TiN/TiB2 composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al2O3 can react with TiB2, leading to the formations of Ti3Al and B. This principle can be used to improve the Fe3Al + B4C/TiN laser-cladded coating on the Ti-6Al-4V alloy. Furthermore, during the cladding process, C consumed the oxygen in Fe3Al + B4C /TiN + Al2O3 molten pool, which retarded the productions of the redundant metal oxides.

A study on wear resistance and microcrack of the Ti 3Al/TiAl + TiC ceramic layer deposited by laser cladding on Ti-6Al-4V alloy

NASA Astrophysics Data System (ADS)

Li, Jianing; Chen, Chuanzhong; Squartini, Tiziano; He, Qingshan

2010-12-01

Laser cladding of the Al + TiC alloy powder on Ti-6Al-4V alloy can form the Ti 3Al/TiAl + TiC ceramic layer. In this study, TiC particle-dispersed Ti 3Al/TiAl matrix ceramic layer on the Ti-6Al-4V alloy by laser cladding has been researched by means of X-ray diffraction, scanning electron microscope, electron probe micro-analyzer, energy dispersive spectrometer. The main difference from the earlier reports is that Ti 3Al/TiAl has been chosen as the matrix of the composite coating. The wear resistance of the Al + 30 wt.% TiC and the Al + 40 wt.% TiC cladding layer was approximately 2 times greater than that of the Ti-6Al-4V substrate due to the reinforcement of the Ti 3Al/TiAl + TiC hard phases. However, when the TiC mass percent was above 40 wt.%, the thermal stress value was greater than the materials yield strength limit in the ceramic layer, the microcrack was present and its wear resistance decreased.

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. (c) 2005 Wiley Periodicals, Inc.

Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

1998-01-01

A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

Grain Refinement of Al-Si-Fe-Cu-Zn-Mn Based Alloy by Al-Ti-B Alloy and Its Effect on Mechanical Properties.

PubMed

Yoo, Hyo-Sang; Kim, Yong-Ho; Jung, Chang-Gi; Lee, Sang-Chan; Lee, Seong-Hee; Son, Hyeon-Taek

2018-03-01

We investigated the effects of Al-5.0wt%Ti-1.0wt%B addition on the microstructure and mechanical properties of the as-extruded Al-0.15wt%Si-0.2wt%Fe-0.3wt%Cu-0.15wt%Zn-0.9wt%Mn based alloys. The Aluminum alloy melt was held at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 38:1. AlTiB addition to Al-0.15Si-0.2Fe-0.3Cu-0.15Zn-0.9Mn based alloys resulted in the formation of Al3Ti and TiB2 intermetallic compounds and grain refinement. With increasing of addition AlTiB, ultimate tensile strength increased from 93.38 to 99.02 to 100.01 MPa. The tensile strength of the as-extruded alloys was improved due to the formation of intermetallic compounds and grain refinement.

Modeling creep deformation of a two-phase TiAI/Ti3Al alloy with a lamellar microstructure

NASA Astrophysics Data System (ADS)

Bartholomeusz, Michael F.; Wert, John A.

1994-10-01

A two-phase TiAl/Ti3Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti3Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti3Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti3Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti3Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar micro-structure. Application of the model yields a very good correlation between predicted and experimentally observed minimum creep rates over moderate stress and temperature ranges.

Oxidation characteristics of Ti-25Al-10Nb-3V-1Mo intermetallic alloy

NASA Technical Reports Server (NTRS)

Wallace, Terryl A.; Clark, Ronald K.; Sankaran, Sankara N.; Wiedemann, Karl E.

1990-01-01

Static oxidation kinetics of the super-alpha 2 titanium-aluminide alloy Ti-25Al-10Nb-3V-1Mo (at. percent) were investigated in air over the temperature range of 650 to 1000 C using thermogravimetric analysis. The oxidation kinetics were complex at all exposure temperatures and displayed up to three distinct oxidation rates. Breakaway oxidation occurred after long exposure times at high temperatures. Oxidation products were determined using x ray diffraction techniques, electron microprobe analysis, and energy dispersive x ray analysis. Oxide scale morphology was examined by scanning electron microscopy of the surfaces and cross sections of oxidized specimens. The oxides during the parabolic stages were compact and multilayered, consisting primarily of TiO2 doped with Nb, a top layer of Al2O3, and a thin bottom layer of TiN. The transition between the second and third parabolic stage was found to be linked to the formation of a TiAl layer at the oxide-metal interface. Porosity was formed during the third stage, causing degradation of the oxide and the beginning of breakaway oxidation.

Atom probe tomographic studies of precipitation in Al-0.1Zr-0.1Ti (at.%) alloys.

PubMed

Knipling, Keith E; Dunand, David C; Seidman, David N

2007-12-01

Atom probe tomography was utilized to measure directly the chemical compositions of Al(3)(Zr(1)-(x)Ti(x)) precipitates with a metastable L1(2) structure formed in Al-0.1Zr-0.1Ti (at.%) alloys upon aging at 375 degrees C or 425 degrees C. The alloys exhibit an inhomogeneous distribution of Al(3)(Zr(1)-(x)Ti(x)) precipitates, as a result of a nonuniform dendritic distribution of solute atoms after casting. At these aging temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that Ti remains mainly in solid solution rather than partitioning to the Al(3)(Zr(1)-(x)Ti(x)) precipitates. This is interpreted as being due to the very small diffusivity of Ti in alpha-Al, consistent with prior studies on Al-Sc-Ti and Al-Sc-Zr alloys, where the slower diffusing Zr and Ti atoms make up a small fraction of the Al(3)(Zr(1)-(x)Ti(x)) precipitates. Unlike those alloys, however, the present Al-Zr-Ti alloys exhibit no interfacial segregation of Ti at the matrix/precipitate heterophase interface, a result that may be affected by a significant disparity in the evaporation fields of the alpha-Al matrix and Al(3)(Zr(1)-(x)Ti(x)) precipitates and/or a lack of local thermodynamic equilibrium at the interface.

Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy.

PubMed

Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

2017-09-19

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α₂) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10 -5 s -1 to 1 × 10 -3 s -1 . The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10 -5 s -1 , while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001) γ //(110) γ .

Effect of Inoculant Alloy Selection and Particle Size on Efficiency of Isomorphic Inoculation of Ti-Al

PubMed Central

Rouat, Bernard; Daloz, Dominique; Bouzy, Emmanuel

2018-01-01

The process of isomorphic inoculation relies on precise selection of inoculant alloys for a given system. Three alloys, Ti-10Al-25Nb, Ti-25Al-10Ta, and Ti-47Ta (at %) were selected as potential isomorphic inoculants for a Ti-46Al alloy. The binary Ti-Ta alloy selected was found to be ineffective as an inoculant due to its large density difference with the melt, causing the particles to settle. Both ternary alloys were successfully implemented as isomorphic inoculants that decreased the equiaxed grain size and increased the equiaxed fraction in their ingots. The degree of grain refinement obtained was found to be dependent on the number of particles introduced to the melt. Also, more new grains were formed than particles added to the melt. The grains/particle efficiency varied from greater than one to nearly twenty as the size of the particle increased. This is attributed to the breaking up of particles into smaller particles by dissolution in the melt. For a given particle size, Ti-Al-Ta and Ti-Al-Nb particles were found to have a roughly similar grain/particle efficiency. PMID:29693591

Study on the Anti-Poison Performance of Al-Y-P Master Alloy for Impurity Ca in Aluminum Alloys.

PubMed

Zuo, Min; Dong, Yu; Zhao, Degang; Wang, Yan; Teng, Xinying

2017-11-26

In this article, the anti-poison performance of novel Al-6Y-2P master alloy for impurity Ca in hypereutectic Al-Si alloys was investigated in detail. According to the microstructural analysis, it can be found that the primary Si and eutectic Si particles could be relatively modified and refined. In order to investigate the influence mechanism of Ca on the limited refinement performance of Al-6Y-2P master alloy, types of Al-xSi-2Ca-3Y-1P (x = 0, 6, 12, 18, and 30) alloys were prepared. It is observed that Ca takes the form of more stable Ca3P2 compounds by reacting with YP, and the surface of Ca3P2 particles are unsmooth, and even some have wrinkles in Al Al-2Ca-3Y-1P alloy. With the increase of Si content in Al-xSi-2Ca-3Y-1P (x = 6, 12, 18 and 30) systems, the multi-encapsulation structures, i.e., the phosphide (AlP and YP), hexagonal Al2Si2Ca, the Al3Si2Y2 or primary Si from inside to outside in order were examined.The excapsulation of YP and AlP caused by Al2Si2Ca might be the reason for the limited refinement effect of Al-6Y-2P master alloy for hypereutectic Al-18Si alloys.

Laser Cladding of Ti-6Al-4V Alloy with Ti-Al2O3 Coating for Biomedical Applications

NASA Astrophysics Data System (ADS)

Mthisi, A.; Popoola, A. P. I.; Adebiyi, D. I.; Popoola, O. M.

2018-05-01

The indispensable properties of Ti-6Al-4V alloy coupled with poor tribological properties and delayed bioactivity make it a subject of interest to explore in biomedical application. A quite number of numerous coatings have been employed on titanium alloys, with aim to overcome the poor properties exhibited by this alloy. In this work, the possibility of laser cladding different ad-mixed powders (Ti - 5 wt.% Al2O3 and Ti - 8wt.% Al2O3) on Ti-6Al-4V at various laser scan speed (0.6 and 0.8 m/min) were investigated. The microstructure, phase constituents and corrosion of the resultant coatings were characterized by scanning electron microscope (SEM), Optical microscope, X-Ray diffractometer (XRD) and potentiostat respectively. The electrochemical behaviour of the produced coatings was studied in a simulated body fluid (Hanks solution). The microstructural results show that a defect free coating is achieved at low scan speed and ad-mixed of Ti-5 wt. % Al2O3. Cladding of Ti - Al2O3 improved the corrosion resistance of Ti-6Al-4V alloy regardless of varying neither scan speed nor ad-mixed percentage. However, Ti-5 wt.% Al2O3 coating produced at low scan speed revealed the highest corrosion resistance among the coatings due to better quality coating layer. Henceforth, this coating may be suitable for biomedical applications.

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.

Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy

PubMed Central

Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

2017-01-01

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α2) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10−5 s−1 to 1 × 10−3 s−1. The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10−5 s−1, while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001)γ//(110)γ. PMID:28925971

Advanced Mechanical Properties of a Powder Metallurgy Ti-Al-N Alloy Doped with Ultrahigh Nitrogen Concentration

NASA Astrophysics Data System (ADS)

Shen, J.; Chen, B.; Umeda, J.; Kondoh, K.

2018-03-01

Titanium and its alloys are recognized for their attractive properties. However, high-performance Ti alloys are often alloyed with rare or noble-metal elements. In the present study, Ti alloys doped with only ubiquitous elements were produced via powder metallurgy. The experimental results showed that pure Ti with 1.5 wt.% AlN incorporated exhibited excellent tensile properties, superior to similarly extruded Ti-6Al-4V. Further analysis revealed that its remarkably advanced strength could primarily be attributed to nitrogen solid-solution strengthening, accounting for nearly 80% of the strength increase of the material. In addition, despite the ultrahigh nitrogen concentration up to 0.809 wt.%, the Ti-1.5AlN sample showed elongation to failure of 10%. This result exceeds the well-known limitation for nitrogen (over 0.45 wt.%) that causes embrittlement of Ti alloys.

Oxidation behavior of Al/Cr coating on Ti2AlNb alloy at 900 °C

NASA Astrophysics Data System (ADS)

Yang, Zhengang; Liang, Wenping; Miao, Qiang; Chen, Bowen; Ding, Zheng; Roy, Nipon

2018-04-01

In this paper, the Al/Cr coating was fabricated on the surface of Ti2AlNb alloy via rf magnetron sputtering and double glow treatment to enhance oxidation resistance. The protective coating with an outer layer of Al and inner layer of Cr has great bonding strength due to the in-diffusion of Cr and the inter-diffusion between Al and Cr to form Al-Cr alloyed layer which has great hardness. Acoustic emission curve which was detected via WS-2005 scratch tester indicates the bonding strength between Al/Cr coating and substrate is great. Morphology of Ti2AlNb alloy with Al/Cr coating after scratch test shows that the scratch is smooth without disbanding, and the depth and breadth of scratch are changed uniformly. The mass change was reduced after oxidation test due to the Al/Cr protective coating. Isothermal oxidation test at 900 °C was researched. Results indicate that Al/Cr coating provided oxidation resistance of Ti2AlNb alloy with prolonged air exposure at 900 °C. Al2O3 was detected by XRD patterns and SEM images, and was formed on the surface of Ti2AlNb alloy to protect substrate during oxidation test. A certain content of Cr is beneficial for the formation of Al2O3. Besides, Cr2O3 was produced under Al2O3 by outward diffusion of Cr to protect substrate sequentially, no cracks were discovered on Al/Cr protective coating. The process of Ti outward diffusion into surface was suppressive due to integration of Cr-Ti and Al-Ti intermetallics. A steady, adherent and continuous coated layer of Al/Cr on Ti2AlNb alloy increases oxidation resistance.

Osteoblast Cell Response on the Ti6Al4V Alloy Heat-Treated

PubMed Central

Chávez-Díaz, Mercedes Paulina; Escudero-Rincón, María Lorenza; Arce-Estrada, Elsa Miriam; Cabrera-Sierra, Román

2017-01-01

In an effort to examine the effect of the microstructural changes of the Ti6Al4V alloy, two heat treatments were carried out below (Ti6Al4V800) and above (Ti6Al4V1050) its β-phase transformation temperature. After each treatment, globular and lamellar microstructures were obtained. Saos-2 pre-osteoblast human osteosarcoma cells were seeded onto Ti6Al4V alloy disks and immersed in cell culture for 7 days. Electrochemical assays in situ were performed using OCP and EIS measurements. Impedance data show a passive behavior for the three Ti6Al4V alloys; additionally, enhanced impedance values were recorded for Ti6Al4V800 and Ti6Al4V1050 alloys. This passive behavior in culture medium is mostly due to the formation of TiO2 during their sterilization. Biocompatibility and cell adhesion were characterized using the SEM technique; Ti6Al4V as received and Ti6Al4V800 alloys exhibited polygonal and elongated morphology, whereas Ti6Al4V1050 alloy displayed a spherical morphology. Ti and O elements were identified by EDX analysis due to the TiO2 and signals of C, N and O, related to the formation of organic compounds from extracellular matrix. These results suggest that cell adhesion is more likely to occur on TiO2 formed in discrete α-phase regions (hcp) depending on its microstructure (grains). PMID:28772804

Milling of gamma TiAl intermetallic alloys

NASA Astrophysics Data System (ADS)

Beranoagirre, A.; López de Lacalle, L. N.

2009-11-01

The work here exposed, is framed in the line of development of slight materials with good properties, used to reduction of weight in different components for the aviation and automotion. To use at high temperatures in slight pieces with high resistance. The superalloys of type Gamma TiAl is a attractive alternative to other titanium alloys, due to high relationship resistance/weigh and the resistance to the corrosion. This work, obtained the results in millin of three types of gamma TiAl alloys. Tools of integral hard metal are used, with different advances and cut speeds.

Preferential site occupancy of alloying elements in TiAl-based phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holec, David, E-mail: david.holec@unileoben.ac.at; Reddy, Rajeev K.; Klein, Thomas

2016-05-28

First principles calculations are used to study the preferential occupation of ternary alloying additions into the binary Ti-Al phases, namely, γ-TiAl, α{sub 2}-Ti{sub 3}Al, β{sub o}-TiAl, and B19-TiAl. While the early transition metals (TMs, group IVB, VB, and VIB elements) prefer to substitute for Ti atoms in the γ-, α{sub 2}-, and B19-phases, they preferentially occupy Al sites in the β{sub o}-TiAl. Si is, in this context, an anomaly, as it prefers to sit on the Al sublattice for all four phases. B and C are shown to prefer octahedral Ti-rich interstitial positions instead of substitutional incorporation. The site preferencemore » energy is linked with the alloying-induced changes of energy of formation, hence alloying-related (de)stabilisation of the phases. We further show that the phase-stabilisation effect of early TMs on β{sub o}-phase has a different origin depending on their valency. Finally, an extensive comparison of our predictions with available theoretical and experimental data (which is, however, limited mostly to the γ-phase) shows a consistent picture.« less

Microstructure/Oxidation/Microhardness Correlations in Gamma-Based and Tau-Based Al-Ti-Cr Alloys

NASA Technical Reports Server (NTRS)

Brady, Michael P.; Smialek, J. L.; Humphrey, D. L.

1994-01-01

The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800 C and 1000 C were investigated. The relevant phases were identified as tau (Ll2), gamma (LIO), r-Al2Ti, TiCrAl (laves), and Cr2AI. Protective alumina formation was associated with tau, Al-rich TiCrAl, and gamma/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and tau decomposition to A12Ti + Cr2AI. It was concluded that two-phase gamma + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.

Effect of Mn and AlTiB Addition and Heattreatment on the Microstructures and Mechanical Properties of Al-Si-Fe-Cu-Zr Alloy.

PubMed

Yoo, Hyo-Sang; Kim, Yong-Ho; Lee, Seong-Hee; Son, Hyeon-Taek

2018-09-01

The microstructure and mechanical properties of as-extruded Al-0.1 wt%Si-0.2 wt%Fe- 0.4 wt%Cu-0.04 wt%Zr-xMn-xAlTiB (x = 1.0 wt%) alloys under various annealing processes were investigated and compared. After the as-cast billets were kept at 400 °C for 1 hr, hot extrusion was carried out with a reduction ratio of 38:1. In the case of the as-extruded Al-Si-Fe-Cu-Zr alloy at annealed at 620 °C, large equiaxed grain was observed. When the Mn content is 1.0 wt%, the phase exhibits a skeleton morphology, the phase formation in which Mn participated. Also, the volume fraction of the intermetallic compounds increased with Mn and AlTiB addition. For the Al-0.1Si-0.2Fe-0.4Cu-0.04Zr alloy with Mn and AlTiB addition from 1.0 wt%, the ultimate tensile strength increased from 100.47 to 119.41 to 110.49 MPa. The tensile strength of the as-extruded alloys improved with the addition of Mn and AlTiB due to the formation of Mn and AlTiB-containing intermetallic compounds.

Strengthening behavior of beta phase in lamellar microstructure of TiAl alloys

NASA Astrophysics Data System (ADS)

Zhu, Hanliang; Seo, D. Y.; Maruyama, K.

2010-01-01

β phase can be introduced to TiAl alloys by the additions of β stabilizing elements such as Cr, Nb, W, and Mo. The β phase has a body-centered cubic lattice structure and is softer than the α2 and γ phases in TiAl alloys at elevated temperatures, and hence is thought to have a detrimental effect on creep strength. However, fine β precipitates can be formed at lamellar interfaces by proper heat treatment conditions and the β interfacial precipitate improves the creep resistance of fully lamellar TiAl alloys, since the phase interface of γ/β retards the motion of dislocations during creep. This paper reviews recent research on high-temperature strengthening behavior of the β phase in fully lamellar TiAl alloys.

Microstructure and properties of an Al-Ti-Cu-Si brazing alloy for SiC-metal joining

NASA Astrophysics Data System (ADS)

Dai, Chun-duo; Ma, Rui-na; Wang, Wei; Cao, Xiao-ming; Yu, Yan

2017-05-01

An Al-Ti-Cu-Si solid-liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500-600°C was designed for SiC-metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al-8.5Ti-5Cu-10Si alloy is mainly composed of Al-Al2Cu and Al-Si hypoeutectic low-melting-point microstructures (493-586°C) and the high-melting-point intermetallic compound AlTiSi (840°C). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al4C3 phase at the interface is suppressed by the addition of 10wt% Si to the alloy.

Semisolid Microstructural Evolution during Partial Remelting of a Bulk Alloy Prepared by Cold Pressing of the Ti-Al-2024Al Powder Mixture

PubMed Central

Qin, Yahong; Chen, Tijun; Wang, Yingjun; Zhang, Xuezheng; Li, Pubo

2016-01-01

A new method, powder thixoforming, has been proposed to fabricate an in situ Al3Tip/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and the formation mechanism of the Al3Ti particles produced by the reaction between the Ti powder and the Al alloy melt is also discussed in detail. The results indicate that the microstructural evolution of the 2024 alloy matrix can be divided into three stages: a rapid coarsening of the powder grains; a formation of primary α-Al particles surrounded with a continuous liquid film; and a slight coarsening of the primary α-Al particles. Simultaneously, a reaction layer of Al3Ti can be formed on the Ti powder surface when the bulk is heated for 10 min at 640 °C The thickness (X) of the reaction layer increases with the time according to the parabolic law of X=−0.43t2+4.21t+0.17. The stress generated in the reaction layer due to the volume dilatation can be calculated by using the equation σAl3Ti=−EAl3Ti6(1−υAl3Ti)t2Al3TitTi(1R−1R0). Comparing the obtained data with the results of the drip experiment, the reaction rate for the Ti powder and Al powder mixture is greater than that for the Ti plate and Al alloy mixture, respectively.

Hot Corrosion Behavior of Ti-48Al and Ti-48Al-2Cr Intermetallic Alloys Produced by Electric Current Activated Sintering

NASA Astrophysics Data System (ADS)

Garip, Y.; Ozdemir, O.

2018-06-01

In this study, Ti-48Al and Ti-48Al-2Cr (at. pct) intermetallic alloys were produced by electric current activated sintering (ECAS). In order to characterize the phase formation and microstructures of these alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis were used. The XRD result shows that the intermetallic alloys are composed of γ-TiAl and α 2-Ti3Al phases. The microstructure is dense with a low amount of porosity. The hot corrosion behavior of intermetallic alloys was carried out in a salt mixture of 25 wt pct K2SO4 and 75 wt pct Na2SO4 at 700 °C for 180 hours. The morphology of corroded surfaces was observed by SEM-EDS and XRD. Corrosion phases were identified as TiO2 and Al2O3. Well-adhering oxide scale was detected on the corroded sample surface at the end of 180 hours, and no spallation was observed. In addition, a parabolic curve was obtained at the weight change rate vs time.

Corrosion characterization of in-situ titanium diboride (TiB2) reinforced aluminium-copper (Al-Cu) alloy by two methods: Salts spray fog and linear polarization resistance (LPR)

NASA Astrophysics Data System (ADS)

Rosmamuhamadani, R.; Talari, M. K.; Yahaya, Sabrina M.; Sulaiman, S.; Ismail, M. I. S.; Hanim, M. A. Azmah

2018-05-01

Aluminium-copper (Al-Cu) alloys is the one of most Metal Matrix Composites (MMCs) have important high-strength Al alloys. The aluminium (Al) casting alloys, based on the Al-Cu system are widely used in light-weight constructions and transport applications requiring a combination of high strength and ductility. In this research, Al-Cu master alloy was reinforced with 3 and 6wt.% titanium diboride (TiB2) that obtained from salts route reactions. The salts used were were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). The salts route reaction process were done at 800 °C. The Al-Cu alloy then has characterized on the mechanical properties and microstructure characterization. Salts spray fog test and Gamry-electrode potentiometer instruments were used to determine the corrosion rate of this alloys. From results obtained, the increasement of 3wt.%TiB2 contents will decrease the value of the corrosion rate. In corrosion test that conducted both of salt spray fog and Gamry-electrode potentiometer, the addition of 3wt.%TiB2 gave the good properties in corrosion characterization compare to Al-Cu-6wt.%TiB2 and Al-Cu cast alloy itself. As a comparison, Al-Cu with 3wt.%TiB2 gave the lowest value of corrosion rate, which means alloy has good properties in corrosion characterization. The results obtained show that in-situ Al-Cu alloy composites containing the different weight of TiB2 phase were synthesized successfully by the salt-metal reaction method.

Mechanical strength and microstructure of laser-welded Ti-6Al-7Nb alloy castings.

PubMed

Srimaneepong, Viritpon; Yoneyama, Takayuki; Kobayashi, Equo; Doi, Hisashi; Hanawa, Takao

2005-12-01

Mechanical properties of laser-welded castings of Ti-6Al-7Nb alloy, CP Ti, and Co-Cr alloy were investigated and compared to the unwelded castings using a tensile test. Dumbbell-shaped specimens were cut at the center, and two halves of the specimens were welded with an Nd:YAG laser welding machine at 220 or 260 V of laser voltage. The mechanical strength of 260 V groups was higher than that of 220 V groups for Ti-6Al-7Nb and Co-Cr alloys except for CP Ti. All 260 V laser-welded castings of Ti-6Al-7Nb alloy and CP Ti, which fractured outside the welded joints, exhibited ductile characteristics, while all laser-welded Co-Cr alloy castings, which fractured within the welded joints, showed brittle characteristics. This study proved that the mechanical strength of laser-welded Ti-6Al-7Nb alloy and CP Ti castings was as high as that of unwelded castings, while the mechanical properties of laser-welded alloy joints were influenced by microstructural changes.

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Effect of in-situ formed Al3Ti particles on the microstructure and mechanical properties of 6061 Al alloy

NASA Astrophysics Data System (ADS)

Gupta, Rahul; Chaudhari, G. P.; Daniel, B. S. S.

2018-03-01

In this study, in situ Titanium-tri-aluminide (Al3Ti) particles reinforced Al 6061 alloy matrix composites were fabricated by the reaction of potassium hexafluorotitanate (K2TiF6) inorganic salt with molten Al 6061 alloy via liquid metallurgy route. The development of in-situ Al3Ti particles and their effects on the mechanical properties such as yield strength (YS), ductility, ultimate tensile strength (UTS) and hardness, and microstructure of Al 6061 alloy were studied. It was observed from the results that in-situ formed Al3Ti particles were blocky in morphology whose average size was around 2.6 ± 1.1 μm. Microstructure studies showed that grain size of Al matrix was reduced due to the nucleating effect of Al3Ti particles. It was observed from the mechanical properties analysis that when the volume fraction of Al3Ti particles was increased, the hardness, UTS and YS of the composites were also increased as compared to that of Al 6061 alloy. An improvement in ductility was observed with the dispersion of Al3Ti particles in base alloy which is contrary to many other composites.

Effect of the Heat-Treated Ti6Al4V Alloy on the Fibroblastic Cell Response

PubMed Central

Chávez-Díaz, Mercedes Paulina; Escudero-Rincón, María Lorenza; Arce-Estrada, Elsa Miriam; Cabrera-Sierra, Román

2017-01-01

Two heat treatments were carried out below (Ti6Al4V800) and above (Ti6Al4V1050) Ti6Al4V beta-phase transformation temperature (980 °C), with the purpose of studying the effect of microstructure on the adhesion and proliferation of fibroblast cells, as well as their electrochemical behavior. These alloys were seeded with 10,000 L929 fibroblast cells and immersed for 7 days in the cell culture at 37 °C, pH 7.40, 5% CO2 and 100% relative humidity. Cell adhesion was characterized by Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) techniques. Polygonal and elongated cell morphology was observed independent of Ti6Al4V microstructure. Besides, C, O, P, S, Na and Cl signals were detected by Energy Dispersive X-Ray Spectroscopy (EDX), associated with the synthesis of organic compounds excreted by the cells, including protein adsorption from the medium. In certain areas on Ti6Al4V and Ti6Al4V800 alloys, cells were agglomerated (island type), likely related to the globular microstructure; meanwhile, larger cellular coverage is shown for Ti6Al4V1050 alloy, forming more than one layer on the surface, where only Ca was recorded. Impedance diagrams showed a similar passive behavior for the different Ti6Al4V alloys, mainly due to TiO2 overlaying the contribution of the organic compounds excreted by fibroblast cells. PMID:29301205

Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

NASA Technical Reports Server (NTRS)

Mehrotra, Gopal M.

1992-01-01

Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

Development of a TiAl Alloy by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Couret, Alain; Voisin, Thomas; Thomas, Marc; Monchoux, Jean-Philippe

2017-12-01

Spark plasma sintering (SPS) is a consolidated powder metallurgy process for which the powder sintering is achieved through an applied electric current. The present article aims to describe the method we employed to develop a TiAl-based alloy adjusted for this SPS process. Owing to its enhanced mechanical properties, this alloy was found to fully match the industrial specifications for the aeronautic and automotive industries, which require a high strength at high temperature and a reasonably good ductility at room temperature. A step-by-step method was followed for this alloy development. Starting from a basic study on the as-SPSed GE alloy (Ti-48Al-2Cr-2Nb) in which the influence of the microstructure was studied, the microstructure-alloy composition relationships were then investigated to increase the mechanical properties. As a result of this study, we concluded that tungsten had to be the major alloying element to improve the resistance at high temperature and a careful addition of boron would serve the properties at room temperature. Thus, we developed the IRIS alloy (Ti-48Al-2W-0.08B). Its microstructure and mechanical properties are described here.

High-Pressure Spark Plasma Sintering (HP SPS): A Promising and Reliable Method for Preparing Ti-Al-Si Alloys.

PubMed

Knaislová, Anna; Novák, Pavel; Cygan, Sławomir; Jaworska, Lucyna; Cabibbo, Marcello

2017-04-27

Ti-Al-Si alloys are prospective material for high-temperature applications. Due to low density, good mechanical properties, and oxidation resistance, these intermetallic alloys can be used in the aerospace and automobile industries. Ti-Al-Si alloys were prepared by powder metallurgy using reactive sintering, milling, and spark plasma sintering. One of the novel SPS techniques is high-pressure spark plasma sintering (HP SPS), which was tested in this work and applied to a Ti-10Al-20Si intermetallic alloy using a pressure of 6 GPa and temperatures ranging from 1318 K (1045 °C) to 1597 K (1324 °C). The low-porosity consolidated samples consist of Ti₅Si₃ silicides in an aluminide (TiAl) matrix. The hardness varied between 720 and 892 HV 5.

Effect of heat treatment on morphology evolution of Ti2Ni phase in Ti-Ni-Al-Zr alloy

NASA Astrophysics Data System (ADS)

Sheng, Liyuan; Yang, Yang; Xi, Tingfei

2018-03-01

The Ti6Al2Zr alloy with 15 wt.% Ni addition was prepared and then heat treated in the research. The microstructure of the alloy and evolution of Ti2Ni precipitate were investigated. The microstructure observations demonstrate that the Ni addition could promote the formation of eutectoid and eutectic structures in Ti-Al-Zr alloy. In the eutectoid structure, the ultrafine Ti2Ni fiber precipitates in the α-Ti matrix, but in the eutectic structure, the fine α-Ti phases precipitate in the Ti2Ni matrix. The heat treatment could change the morphology of Ti2Ni precipitates by thinning, fragmenting, merging and spherizing. In the alloy heat treated at and below 1073K, the coarsening of α-Ti precipitates in eutectic structure and Ti2Ni precipitates in eutectoid structure is the mainly characteristic. In the alloy heat treated above 1073K, the phase transformation of α to β phase is the main characteristic, which changes the morphology and amount of Ti2Ni phase by the solid solution of Ni. The phase transformation temperature of Ti-Ni-Al-Zr alloy is between 1073-1123K, which is increased compared with that of the Ti-Ni binary phase diagram.

Parameter optimization for selective laser melting of TiAl6V4 alloy by CO2 laser

NASA Astrophysics Data System (ADS)

Baitimerov, R. M.; Lykov, P. A.; Radionova, L. V.; Safonov, E. V.

2017-10-01

TiAl6V4 alloy is one of the widely used materials in powder bed fusion additive manufacturing technologies. In recent years selective laser melting (SLM) of TiAl6V4 alloy by fiber laser has been well studied, but SLM by CO2-lasers has not. SLM of TiAl6V4 powder by CO2-laser was studied in this paper. Nine 10×10×10 mm cubic specimens were fabricated using different SLM process parameters. All of the fabricated specimens have a good dense structure and a good surface finish quality without dimensional distortion. The lowest porosity that was achieved was about 0.5%.

Application of Al-2La-1B Grain Refiner to Al-10Si-0.3Mg Casting Alloy

NASA Astrophysics Data System (ADS)

Jing, Lijun; Pan, Ye; Lu, Tao; Li, Chenlin; Pi, Jinhong; Sheng, Ningyue

2018-05-01

This paper reports the application and microstructure refining effect of an Al-2La-1B grain refiner in Al-10Si-0.3Mg casting alloy. Compared with the traditional Al-5Ti-1B refiner, Al-2La-1B refiner shows better performances on the grain refinement of Al-10Si-0.3Mg alloy. Transmission electron microscopy analysis suggests that the crystallite structure features of LaB6 are beneficial to the heterogeneous nucleation of α-Al grains. Regarding the mechanical performances, tensile properties of Al-10Si-0.3Mg casting alloy are prominently improved, due to the refined microstructures.

Synthesis of As-Cast Ti-Al-V Alloy from Titanium-Rich Material by Thermite Reduction

NASA Astrophysics Data System (ADS)

Cheng, Chu; Dou, Zhi He; Zhang, Ting An; Zhang, Hui Jie; Yi, Xin; Su, Jian Ming

2017-10-01

We present a novel methodology for preparing as-cast Ti-Al-V alloy directly from titanium-rich material through a thermite reduction. The new method is shown to be feasible through a thermodynamics and dynamics analysis. The as-cast Ti-Al-V alloys synthesized from titanium dioxide, rutile, and high-titanium slag were analyzed by an x-ray diffractometer, a scanning electron microscope, an inductively coupled plasma emission spectrometer, and an oxygen/nitrogen/hydrogen analyzer. The results indicate that the alloy is composed of a Ti-Al-V matrix and Al2O3 inclusions. The Al and V contents in the matrix are close to the mass ratio of Ti-6Al-4V (Al: 5.5-6.8 wt.%, V: 3.5-4.5 wt.%). The Si and Fe in the alloys synthesized from rutile and high-titanium slag can be used as alloying elements in low-cost titanium alloys. The present method is expected to be useful for preparing Ti-Al-V alloys at a low production cost.

Evaluation of precipitation hardening in TiC-reinforced Ti2AlNb-based alloys

NASA Astrophysics Data System (ADS)

Zhang, Ya-ran; Cai, Qi; Liu, Yong-chang; Ma, Zong-qing; Li, Chong; Li, Hui-jun

2018-04-01

Ti2AlNb-based alloys with 0.0wt%, 0.6wt%, and 2.0wt% carbon nanotube (CNT) addition were fabricated from spherical Ti-22Al-25Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050°C were identified as TiC and facilitated the transformation of α2 + B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2 + O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0wt% CNT addition increased to HV 429 ± 9.

Microstructure, Mechanical and Surface Morphological Properties of Al5Ti5Cr Master Alloy as Friction Material Prepared by Stir Die Casting

NASA Astrophysics Data System (ADS)

Ahmed, Syed Faisal; Srivastava, Sanjay; Agarwal, Alka Bani

2018-04-01

Metal matrix composite offers outstanding properties for better performance of disc brakes. In the present study, the composite of AlTiCr master alloy was prepared by stir die casting method. The developed material was reinforced with (0-10 wt%) silicon carbide (SiC) and boron carbide (B4C). The effects of SiC reinforcement from 0 to 10 wt% on mechanical, microstructure and surface morphological properties of Al MMC was investigated and compared with B4C reinforcement. Physical properties like density and micro Vickers hardness number show an increasing trend with an increase in the percentage of SiC and B4C reinforcement. Mechanical properties viz. UTS, yield strength and percentage of elongation are improved with increasing the fraction of reinforcement. The surface morphology and phase were identified from scanning electron microscopy (SEM) and X-ray diffraction analysis and the oxidized product formed during the casting was investigated by Fourier transformation infrared spectroscopy. This confirms the presence of crystallization of corundum (α-Al2O3) in small traces as one of the alumina phases, within casting sample. Micro-structural characterization by SEM depicted that the particles tend to be more agglomerated more and more with the percentage of the reinforcement. The AFM results reveal that the surface roughness value shows a decreasing trend with SiC reinforcement while roughness increases with increase the percentage of B4C.

Principles of Structure and Phase Composition Formation in Composite Master Alloys of the Al-Ti-B/B4c Systems Used for Aluminum Alloy Modification

NASA Astrophysics Data System (ADS)

Zhukov, I. A.; Promakhov, V. V.; Matveev, A. E.; Platov, V. V.; Khrustalev, A. P.; Dubkova, Ya. A.; Vorozhtsov, S. A.; Potekaev, A. I.

2018-03-01

The principles of formation of structure and properties of materials produced by self-propagating hightemperature synthesis (SHS) from the Al-Ti-B/B4C powder systems are identified. It is shown that the SHSmaterials produced from the Al-Ti-B powder systems consist of a TiAl intermetallic matrix with inclusions of titanium diboride particles. It is found out that an introduction of 1 wt.% of TiB2 particles into the melt of the AD35 aluminum alloy allows reducing the grain size from 620 to 220 μm and gives rise to an increase in the ultimate tensile strength of as-cast specimens from 100 to 145 MPa and in the plasticity from 7 to 9%.

Corrosion resistance, mechanical properties, corrosion fatigue strength and cytocompatibility of new Ti alloys without Al and V.

PubMed

Okazaki, Y; Rao, S; Ito, Y; Tateishi, T

1998-07-01

The effects of various metallic ions using various metallic powders on the relative growth ratio of fibroblasts L929 and osteoblasts MC3T3-E1 cells were carried out. Ti, Zr, Sn, Nb and Ta had evidently no effect on the relative growth ratios of cells. Otherwise, Al and V ions exhibit cytotoxicity from a concentration of > or = 0.2 ppm. This Al effect on cells tend to be stronger in medium containing small quantity of V ions (< or = 0.03 ppm). The new Ti-15%Zr-4%Nb-4%Ta-0.2%Pd alloy exhibited a higher corrosion resistance in physiological saline solution. The addition of 0.02%O and 0.05%N to Ti-Zr alloy improved the mechanical properties at room temperature and corrosion fatigue strength. The relative growth ratios for the new Ti alloy plate and the alloy block extraction were unity. Further, the relative growth ratios were almost unity for the new Ti alloy against apatite ceramic pins up to 10(5) wear cycles in Eagle's MEM solution. However, there was a sharp decrease for Ti-6%Al-4%V ELI alloy from 3 x 10(4) wear cycles as V ion was released during wear into the wear test solution since the pH of the Eagle's MEM increases with increasing wear cycles.

Fatigue design curve of a TiNi/Al shape memory alloy composite for aircraft stringer design

NASA Astrophysics Data System (ADS)

Park, Young-Chul; Jo, Young-Jik; Baek, Seok-Heum; Furuya, Yasubumi

2009-05-01

In this study, a TiNi/Al6061 shape memory alloy (SMA) composite was fabricated by the hot press method, and pressed by a roller for its strength improvement using the shape memory fiber shrinkage phenomenon. These two kinds of specimens were fabricated with 0% and 5% volume ratio and 0%, 10 % and 20% reduction ratio of TiNi alloy fiber, respectively. A fatigue test has been performed to evaluate the fatigue life for the fabricated TiNi/Al SMA composite as an S-N curve. The results from the Goodman diagram is able to illustrate the failure criterion and fatigue limit between tensile and bending fatigue strength in the fatigue characterization of TiNi/Al SMA composites.

Phase relations in Ti-Al-Nb alloys at 1200 degrees C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suryanarayana, C.; Lee, D.S.

1992-03-15

This paper reports that titanium aluminides based on both Ti{sub 3}Al ({alpha}{sub 2}) and TiAl ({gamma}) have received considerable attention during the past few years as potential candidates for high temperature structural applications in the aerospace industry. This has been due to the attractive combination of properties such as low density, high specific strength, elevated temperature strength and modulus retention, excellent creep resistance and high resistance to oxidation. A serious handicap in using these alloys has been their vary poor ductility. Refinement of grain size, addition of ternary and quaternary alloying elements (e.g., Nb, Mn and Ta) and microstructural refinementsmore » through either innovative heat treatments or by production of nanometer-sized grains through mechanical alloying or magnetron sputtering methods have been explored to increase the ductility. Amongst these approaches, addition of alloying elements, especially of niobium, has proven extremely beneficial. Thus, there have been several investigations in recent years on the constitution, microstructure and properties of ternary Ti-Al-Nb alloys.« less

Effect of different alloyed layers on the high temperature oxidation behavior of newly developed Ti 2AlNb-based alloys

NASA Astrophysics Data System (ADS)

Wu, Hongyan; Zhang, Pingze; Zhao, Haofeng; Wang, Ling; Xie, Aigen

2011-01-01

The application of titanium aluminide orthorhombic alloys (O-phase alloys) as potential materials in aircraft and jet engines was limited by their poor oxidation resistance at high temperature. The Ti 2AlNb-based alloys were chromised (Cr), chromium-tungstened (Cr-W) and nickel-chromised (Ni-Cr) by the double glow plasma surface alloying process to improve their high temperature oxidation resistance. The discontinuous oxidative behavior of Cr, Cr-W and Ni-Cr alloyed layers on Ti 2AlNb-based alloy at 1093 K was explored in this study. After exposing at 1093 K, the TiO 2 layer was formed on the bare alloy and accompanied by the occurrence of crack, which promoted oxidation rate. The oxidation behavior of Ti 2AlNb-based alloys was improved by surface alloying due to the formation of protective Al 2O 3 scale or continuous and dense NiCr 2O 4 film. The Ni-Cr alloyed layer presented the best high-temperature oxidation resistance among three alloyed layers.

Wetting of TiC by Al-Cu alloys and interfacial characterization.

PubMed

Contreras, A

2007-07-01

The wetting behavior and the interfacial reactions that occurred between molten Al-Cu alloys (1, 4, 8, 20, 33, and 100 wt% Cu) and solid TiC substrates were studied by the sessile drop technique in the temperature range of 800-1130 degrees C. The effect of wetting behavior on the interfacial reaction layer was studied. All the Al-Cu alloys react with TiC at the interface forming an extensive reaction layer. The interface thickness varied with the samples, and depends on the temperature, chemical composition of the alloy and the time of the test. Wetting increases with increasing concentration of copper in the Al-Cu alloy at 800 and 900 degrees C. In contrast, at higher temperature such as 1000 degrees C wetting decreases with increasing copper content. The spreading kinetics and the work of adhesion were evaluated. The high values of activation energies indicated that spreading is not a simple viscosity controlled phenomenon but is a chemical reaction process. The spreading of the aluminum drop is observed to occur according to the formation of Al4C3, CuAl2O4, CuAl2, TiCux mainly, leading to a decreases in the contact angle. As the contact angle decreases the work of adhesion increases with increasing temperature. Al-Cu/TiC assemblies showed cohesive fracture corresponding to a strong interface. However, using pure Cu the adhesion work is poor, and the percentage of cohesion work is also too low (27-34%).

Vacuum Pressureless Sintering of Ti-6Al-4V Alloy with Full Densification and Forged-Like Mechanical Properties

NASA Astrophysics Data System (ADS)

Zhang, Ce; Lu, Boxin; Wang, Haiying; Guo, Zhimeng; Paley, Vladislav; Volinsky, Alex A.

2018-01-01

Ti-6Al-4V ingots with a nearly 100% density, fine and homogeneous basket-weave microstructure, and better comprehensive mechanical properties (UTS = 935 MPa, Y.S. = 865 MPa, El. = 15.8%), have been manufactured by vacuum pressureless sintering of blended elemental powders. Coarse TiH2 powder, Al powder (2, 20 μm), V powder, and Al-V master alloy powder were used as raw materials to produce different powder mixtures ( D 50 = 10 μm). Then, the compacts made by cold isostatic pressing were consolidated by different sintering curves. A detailed investigation of different as-sintered samples revealed that a higher density can be obtained by generating transient molten Al in the sintering process. Coarse Al powder and a rapid heating rate under the melting point of Al contribute to molten Al formation. The presence of temporary liquid phase changes the sintering mechanism, accelerating the sintering neck formation, improving sinterability of the powder mixtures. Density of 99.5% was achieved at 1150 °C, which is markedly lower than the sintering temperatures reported for conventional blended elemental powder metallurgy routes. In addition, low interstitial content, especially for oxygen (0.17 wt.%), is obtained by strict process control.

RETRACTED ARTICLE: Microstructure of carbide precipitates in L12-Ni3Al and L10-TiAl

NASA Astrophysics Data System (ADS)

Han, Chang Suk

2008-04-01

The crystallographic structures of carbide formed in Ni3Al- and TiAl-based intermetallics containing carbon are investigated in this study using transmission electron microscopy. In an L12-ordered Ni3Al alloy with 4 mol.% of chromium and 0.2 mol.% to 3.0 mol.% of carbon, fine octahedral precipitates of M23C6 type carbide were formed in the matrix by aging at temperatures around 973 K after solution annealing at 1423 K. TEM examination revealed that the M23C6 phase and the matrix lattices have a cube-cube orientation relationship and maintain partial atomic matching at the {111} interface. After prolonged aging or by aging at higher temperatures, the M23C6 precipitates adopt a rod-like morphology elongated parallel to the <100> directions. In L10-ordered TiAl containing from 0.1 mol.% to 2.0 mol.% carbon, TEM observations reveal that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the L10 matrix appear in the matrix mainly at dislocations. Selected-area electron diffraction (SAED) patterns analyses showed that the needle-shaped precipitate is perovskite-type Ti3AlC. The orientation relationship between the Ti3AlC and the L10 matrix was found to be (001)Ti3AlC//(001)L10 matrix and [010]Ti3AlC//[010]L10 matrix. By aging at higher temperatures or for a longer period at 1073 K, plate-like precipitates of Ti2AlC with a hexagonal structure form on the {111} planes of the L10 matrix. The orientation relationship between the Ti2AlC and the L10 matrix is (0001)Ti2AlC//(111)L10 matrix and Ti2AlC//L10 matrix.

Interface characterization of Cu-Mo coating deposited on Ti-Al alloys by arc spraying

NASA Astrophysics Data System (ADS)

Bai, Shengqiang; Li, Fei; Wu, Ting; Yin, Xianglin; Shi, Xun; Chen, Lidong

2015-03-01

Cu-Mo pseudobinary alloys are promising candidates as electrode materials in CoSb3-based skutterudite thermoelectric (TE) devices for TE power generation. In this study, Cu-Mo coatings were deposited onto Ti-Al substrates by applying a dual-wire electric arc spraying coating technique. The microstructure of the surfaces, cross sections and coating interfaces were analyzed by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). Cu-Mo coatings showed a typical banded splat with compact microstructures, and have no coarse pores nor micro-cracks. The thermal shock resistance of the Cu-Mo coating was also investigated to show good combinations with Ti-Al substrates. After 50 thermal shock cycles, there were no cracks observed at the interface. In contrast, the test of the thermal shock resistance of the Cu coating on the Ti-Al substrate was also investigated. Due to a large difference in the thermal expansion coefficients between Cu and Ti-Al alloys, the Cu coating flaked from the Ti-Al substrate completely after 10 thermal shock cycles. The contact resistivity of the Ti-Al/Cu-Mo interface was about 1.6 μΩṡcm2 and this value was unchanged after 50 thermal shock cycles, indicating the low electric resistance and high thermal stability of the Cu-Mo/Ti-Al interface.

Influence of Rare-Earth Additions on Properties of Titanium Alloys - Effects of Yttrium and Erbium Additions on Ti-8Al and Ti-10Al Alloy.

DTIC Science & Technology

1980-08-31

loop generated during the alternate tension-compression fatigue testing of Ti-8A1 alloy at 6000C at a plastic strain amplitude of * 0.5Z...Dependence of peak stress on the number of cycles in the longitudinal orientation of Ti-lOAl-RE alloys deformed in alternate tension-compression at...of cycles in the transverse orientation of Ti-OAl-RE alloys deformed in alternate tension- A compression fatigue at 500 0C at a plastic strain

Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

NASA Astrophysics Data System (ADS)

Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

2017-01-01

Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

Characteristics and porcelain bond strength of (Ti,Al)N coating on dental alloys.

PubMed

Chung, Kwok-Hung; Duh, Jeng-Gong; Shin, Daehwan; Cagna, David R; Cronin, Robert J

2002-01-01

The effect of a novel titanium-aluminum nitride film, or (Ti,Al)N film, on the bond strength between a dental porcelain and two nickel-based dental alloy substrates was investigated. A thin layer of (Ti,Al)N film was deposited on flat metal samples using a reactive radio-frequency sputtering method. A uniform thickness of porcelain was applied to the film- coated metal samples. Metal-ceramic specimens were subjected to three-point bending, and failure loads were recorded. Bond strengths between the porcelain and (Ti,Al)N-coated metal alloys ranged from 159.0 +/- 11.7 N to 278.0 +/- 12.3 N. These values were significantly greater (p< 0.05) than bond strengths recorded for control samples that did not incorporate the (Ti,Al)N film. An electron probe microanalyzer with a line profile mode was used to characterize the interface between the (Ti,Al)N film and the porcelain. Results of this investigation suggest that the (Ti,Al)N film (1) increases the flexural bond strength between dental porcelain and nickel-based alloy substrates by permitting elemental diffusion, (2) interferes with the surface oxide formation that characteristically originates from the nickel-based metal alloy substrate, and (3) provides an appropriate oxide layer for porcelain application. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 516-521, 2002

Casting of Ti-6Al-4V alloy compared with pure Ti in an Ar-arc casting machine.

PubMed

Syverud, M; Okabe, T; Herø, H

1995-10-01

Dental prostheses of Ti are normally cast in pure Ti. Some appliances, however, require higher yield strength. Casting of Ti alloys is of interest in such cases. The objective of the present work was to study the quality of castings made of Ti-6Al-4V compared with those made of pure Ti. Casting was made into a mold kept at room temperature using a MgO-Al2O3 investment. A standardized five-unit bridge was cast, consisting of two cylindrical crowns with sharp margins and three pontics. The overall mold filling was satisfactory. The margins of the casting alloys were, however, more rugged and incomplete than those of pure Ti. The most likely reason for this difference is the increased formation of dendrites in the alloy and thus more resistance to fluid flow. Furthermore, the sprue of the alloy was also found to contain some spherical, internal pores. Such pores were rare in the pure Ti castings. The surface reactions were found to be minimal for both of the materials. Increased casting deficiencies observed in the cast bridges of the Ti-6Al-4V alloy, compared with pure Ti, were: 1) the margins of the crowns in the bridge were less complete and 2) there was a tendency to an increased internal porosity, particularly in the sprues.

Laser Cladding of γ-TiAl Intermetallic Alloy on Titanium Alloy Substrates

NASA Astrophysics Data System (ADS)

Maliutina, Iuliia Nikolaevna; Si-Mohand, Hocine; Piolet, Romain; Missemer, Florent; Popelyukh, Albert Igorevich; Belousova, Natalya Sergeevna; Bertrand, Philippe

2016-01-01

The enhancement of titanium and titanium alloy's tribological properties is of major interest in many applications such as the aerospace and automotive industry. Therefore, the current research paper investigates the laser cladding of Ti48Al2Cr2Nb powder onto Ti6242 titanium alloy substrates. The work was carried out in two steps. First, the optimal deposition parameters were defined using the so-called "combined parameters," i.e., the specific energy E specific and powder density G. Thus, the results show that those combined parameters have a significant influence on the geometry, microstructure, and microhardness of titanium aluminide-formed tracks. Then, the formation of dense, homogeneous, and defect-free coatings based on optimal parameters has been investigated. Optical and scanning electron microscopy techniques as well as energy-dispersive spectroscopy and X-ray diffraction analyses have shown that a duplex structure consisting of γ-TiAl and α 2-Ti3Al phases was obtained in the coatings during laser cladding. Moreover, it was shown that produced coatings exhibit higher values of microhardness (477 ± 9 Hv0.3) and wear resistance (average friction coefficient is 0.31 and volume of worn material is 5 mm3 after 400 m) compared to those obtained with bare titanium alloy substrates (353 Hv0.3, average friction coefficient is 0.57 and a volume of worn material after 400 m is 35 mm3).

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. Copyright © 2012 Wiley Periodicals, Inc.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Adhesive and tribocorrosive behavior of TiAlPtN/TiAlN/TiAl multilayers sputtered coatings over CoCrMo

NASA Astrophysics Data System (ADS)

Canto, C. E.; Andrade, E.; Rocha, M. F.; Alemón, B.; Flores, M.

2017-09-01

The tribocorrosion resistance and adherence of multilayer coatings of TiAlPtN/TiAlN/TiAl synthesized by PVD reactive magnetron sputtering over a CoCrMo alloy substrate in 10 periods of 30 min each were analyzed and compared to those of the substrate alone and to that of a TiAlPtN single layer coating of the same thickness. The objective of the present work was to create multilayers with different amounts of Pt in order to enhance the tribocorrosion resistance of a biomedical alloy of CoCrMo. Tribocorrosion tests were performed using Simulated Body Fluid (SBF) at typical body temperature with a tribometer in a pin on disk test. The elemental composition and thickness of the coating which behave better at the tribocorrosion tests were evaluated by means of RBS (Rutherford Backscattering Spectroscopy) IBA (Ion Beam Analysis) technique, using an alpha particles beam of 1.8 MeV, before and after the reciprocating motion in the tribocorrosion test. In order to simulate the elemental profile of the samples, the SIMNRA simulation computer code was used. Measurements of the adhesion of the coatings to the substrate were carried on by means of a scratch test using a tribometer. By taking micrographs of the produced tracks, the critical loads at which the coatings are fully separated from the substrate were determined. From these tests it was observed that a coating with 10 min of TiAlPtN in a TiAlPtN/TiAl period of 30 min in multilayers of 10 periods and with an average thickness of 145 nm for the TiAlPtN nanolayers had the best tribocorrosion resistance behavior, compared to that of the CoCrMo alloy. The RBS experiments showed a reduction of the thickness of the films along with some loss of the multilayer structure after the reciprocating motion. The adhesion tests indicated that the multilayer with the average TiAlPtN thickness of 145 nm displayed the highest critical load. These results indicate a high correlation between the adherence and the tribocorrosion behavior.

Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Go

Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgymore » (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition

Fabrication of Ti-0.48Al Alloy by Centrifugal Casting.

PubMed

Park, Jong Bum; Lee, Jung-Il; Ryu, Jeong Ho

2018-09-01

Many of the unique properties of TiAl alloys that make are attractive for use in high-temperature structural applications also make it challenging to process them into useful products. Cast TiAl is rapidly nearing commercialization, particularly in the vehicle industry, owing to its low production cost. In this study, the centrifugal casting of a TiAl (Ti-48%Al, mole fraction) turbocharger was simulated and an experimental casting was created in vacuum using an induction melting furnace coupled to a ceramic composite mold. Numerical simulation results agreed with the experiment. The crystal structure, microstructure, and chemical composition of the TiAl prepared by centrifugal casting were studied by X-ray diffractometry, optical microscopy, field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). FE-SEM and EDS examinations of the TiAl casting revealed that the thickness of the oxide layer (α-case) was typically less than 35 μm.

Surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding

NASA Astrophysics Data System (ADS)

Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F. M.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.

2007-09-01

The present work describes the surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.

Preparation of Aluminum-Zirconium Master Alloy by Aluminothermic Reduction in Cryolite Melt

NASA Astrophysics Data System (ADS)

Liu, Fengguo; Ding, Chenliang; Tao, Wenju; Hu, Xianwei; Gao, Bingliang; Shi, Zhongning; Wang, Zhaowen

2017-12-01

Al-Zr master alloy was prepared by aluminothermic reduction in cryolite melt without alumina impurity. The Al-Zr master alloy was characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The composition of the master alloy was analyzed by inductively coupled plasma optical emission spectrometry. The results indicated that Al-Zr master alloy with high purity could be obtained when byproduct Al2O3 was dissolved in the cryolite melt. The Al-Zr alloy was embedded in the Al matrix in the form of Al3Zr phase with long rod or tetragonal morphology due to temperature variation. Finally, we obtained Al-Zr alloy with 7 wt.% Zr by aluminothermic reduction for 90 min in cryolite melt at 980°C.

Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

NASA Astrophysics Data System (ADS)

Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

2016-05-01

Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

Key improvements in machining of Ti6al4v alloy: A review

NASA Astrophysics Data System (ADS)

Katta, Sivakoteswararao; Chaitanya, G.

2017-07-01

Now a days the use of ti-6al-4v alloy is high in demand in many industries like aero space, bio medical automobile, space, military etc. the production rates in the industries are not sufficient because the machiniability of ti-6al-4v is the main problem, there are several cutting tools available for metal cutting operations still there is a gap in finding the proper cutting tool material for machining of ti-6al-4v. because the properties of titanium like high heat resistant, low thermal conductivity, low weight ratio, less corrosiveness, and more many properties attracting the industrialists to use titanium as their material for their products, many researchers done the research on machininbility of ti-6al-4v by using different tool materials. but as for my literature survey there is still lot of scope is available, to find better cutting tool with techniques for machining ti-6al-4v. in this paper iam discussing the work done by various researchers on ti-6al-4v alloy with different techniques.

The comparison of microstructures and mechanical properties between 14Cr-Al and 14Cr-Ti ferritic ODS alloys

DOE PAGES

Zhang, Guangming; Zhou, Zhangjian; Mo, Kun; ...

2016-03-03

In this study, two kinds of 14Cr ODS alloys (14Cr-Al and 14Cr-Ti) were investigated to reveal the different effects between Al and Ti on the microstructures and mechanical properties of 14Cr ferritic ODS alloys. The microstructure information such as grains, minor phases of these two alloys has been investigated by high-energy X-ray diffraction and transmission electron microscopy (TEM). The in situ synchrotron X-ray diffraction tensile test was applied to investigate the mechanical properties of these two alloys. The lattice strains of different phases through the entire tensile deformation process in these two alloys were analyzed to calculate their elastic stresses.more » From the comparison of elastic stress, the strengthening capability of Y 2Ti 2O 7 is better than TiN in 14Cr-Ti, and the strengthening capability of YAH is much better than YAM and AlN in 14Cr-Al ODS. The dislocation densities of 14Cr-Ti and 14Cr-Al ODS alloys during tensile deformation were also examined by modified Williamson-Hall analyses of peak broadening, respectively. In conclusion, the different increasing speed of dislocation density with plastic deformation reveals the better strengthening effect of Y-Ti-O particles in 14Cr-Ti ODS than that of Y-Al-O particles in 14Cr-Al ODS alloy.« less

Effect of Impact Damage on the Fatigue Response of TiAl Alloy-ABB-2

NASA Technical Reports Server (NTRS)

Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Nazmy, M. Y.; Staubli, M.; Clemens, D. R.

2001-01-01

The ability of gamma-TiAl to withstand potential foreign or domestic object damage is a technical risk to the implementation of gamma-TiAl in low pressure turbine (LPT) blade applications. In the present study, the impact resistance of TiAl alloy ABB-2 was determined and compared to the impact resistance of Ti(48)Al(2)Nb(2)Cr. Specimens were impacted with four different impact conditions with impact energies ranging from 0.22 to 6.09 J. After impacting, the impact damage was characterized by crack lengths on both the front and backside of the impact. Due to the flat nature of gamma-TiAl's S-N (stress vs. cycles to failure) curve, step fatigue tests were used to determine the fatigue strength after impacting. Impact damage increased with increasing impact energy and led to a reduction in the fatigue strength of the alloy. For similar crack lengths, the fatigue strength of impacted ABB-2 was similar to the fatigue strength of impacted Ti(48)Al(2)Nb(2)Cr, even though the tensile properties of the two alloys are significantly different. Similar to Ti(48)Al(2)Nb(2)Cr, ABB-2 showed a classical mean stress dependence on fatigue strength. The fatigue strength of impacted ABB-2 could be accurately predicted using a threshold analysis.

Effect of TiC nano-particles on the mechanical properties of an Al-5Cu alloy after various heat treatments

NASA Astrophysics Data System (ADS)

Zhang, Qingquan; Zhang, Wei; Tian, Weisi; Zhao, Qinglong

2017-12-01

In this paper, the effects of TiC nano-particles on the mechanical properties of Al-5Cu alloy were investigated. Adding TiC nano-particles can effectively refine grain size and secondary dendritic arm. The ultimate tensile strength, yield strength and elongation of the Al-5Cu alloy in each of the three states (i.e. as-cast, solid-solution state and T6 state) were also improved by adding TiC nano-particles. Moreover, the elastic-plastic plane-strain fracture toughness (K J) and work of fracture ( wof) of Al-5Cu containing TiC were significantly higher than those of Al-5Cu without TiC after aging for 10 h. The addition of TiC nano-particles also led to finer and denser ‧ precipitates.

Spectro-photometric determinations of Mn, Fe and Cu in aluminum master alloys

NASA Astrophysics Data System (ADS)

Rehan; Naveed, A.; Shan, A.; Afzal, M.; Saleem, J.; Noshad, M. A.

2016-08-01

Highly reliable, fast and cost effective Spectro-photometric methods have been developed for the determination of Mn, Fe & Cu in aluminum master alloys, based on the development of calibration curves being prepared via laboratory standards. The calibration curves are designed so as to induce maximum sensitivity and minimum instrumental error (Mn 1mg/100ml-2mg/100ml, Fe 0.01mg/100ml-0.2mg/100ml and Cu 2mg/100ml-10mg/ 100ml). The developed Spectro-photometric methods produce accurate results while analyzing Mn, Fe and Cu in certified reference materials. Particularly, these methods are suitable for all types of Al-Mn, Al-Fe and Al-Cu master alloys (5%, 10%, 50% etc. master alloys).Moreover, the sampling practices suggested herein include a reasonable amount of analytical sample, which truly represent the whole lot of a particular master alloy. Successive dilution technique was utilized to meet the calibration curve range. Furthermore, the workout methods were also found suitable for the analysis of said elements in ordinary aluminum alloys. However, it was observed that Cush owed a considerable interference with Fe, the later one may not be accurately measured in the presence of Cu greater than 0.01 %.

Band gap depiction of quaternary FeMnTiAl alloy using Hubbard (U) potential

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Yousuf, Saleem; Khandy, Shakeel Ahmad; Gupta, Dinesh C.

2018-05-01

We have employed self-consistent ab-initio calculations to investigate new quaternary alloy FeMnTiAl by applying Hubbard potential (U). The alloy is found to be stable in ferromagnetic phase with cubic structure. The alloy shows half-metallic (HM) ferromagnet character. The values of minority band gap FeMnTiAl are found to be 0.33 eV respectively. Electronic charge density reveals that both types of bonds covalent as well as ionic are present in the alloy. Thus the new quaternary alloy can be proved as vital contender for spin valves and spin generator devices.

Properties of liquid Ti alloys from electrostatic levitation experiments and simulation

NASA Astrophysics Data System (ADS)

Novak, Brian; Raush, Jonathan; Zhang, Xiaoman; Moldovan, Dorel; Meng, Wenjin; Guo, Shengmin

Accurate thermophysical property data for liquid metals and alloys are important for the development of realistic simulations of laser-based 3D printing processes. We are using the container-less electrostatic levitation (ESL) method, molecular simulation, and CALPHAD calculations to obtain such data for Ti alloys. We performed vacuum ESL measurements of viscosity and surface tension with an oscillating drop technique at NASA MSFC on molten elemental Ti, Ti-xAl binaries (x = 0-10 wt%), Ti-6Al-4V, and Ti-6Al-4V-10Mo which showed improved mechanical properties compared with traditional β Ti alloys. We also used classical molecular simulations to obtain viscosities and surface tensions for Ti-xAl. Pair distribution functions, diffusivities, and vapor pressures were also obtained from simulations. The simulated viscosities and surface tensions for pure Ti agree well with the ESL data while the Ti-xAl viscosities have the same trends as the ESL data, but not quantitative agreement. Chemical activity and Gibbs free energy of Ti-10Al were generated using the CALPHAD technique and compared to experimental values. Supported by the National Science Foundation through cooperative agreement OIA-1541079 and the Louisiana Board of Regents.

Grindability of cast Ti-Cu alloys.

PubMed

Kikuchi, Masafumi; Takada, Yukyo; Kiyosue, Seigo; Yoda, Masanobu; Woldu, Margaret; Cai, Zhuo; Okuno, Osamu; Okabe, Toru

2003-07-01

The purpose of the present study was to evaluate the grindability of a series of cast Ti-Cu alloys in order to develop a titanium alloy with better grindability than commercially pure titanium (CP Ti), which is considered to be one of the most difficult metals to machine. Experimental Ti-Cu alloys (0.5, 1.0, 2.0, 5.0, and 10.0 mass% Cu) were made in an argon-arc melting furnace. Each alloy was cast into a magnesia mold using a centrifugal casting machine. Cast alloy slabs (3.5 mm x 8.5 mm x 30.5 mm), from which the hardened surface layer (250 microm) was removed, were ground using a SiC abrasive wheel on an electric handpiece at four circumferential speeds (500, 750, 1000, or 1250 m/min) at 0.98 N (100 gf). Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1min. Data were compared to those for CP Ti and Ti-6Al-4V. For all speeds, Ti-10% Cu alloy exhibited the highest grindability. For the Ti-Cu alloys with a Cu content of 2% or less, the highest grindability corresponded to an intermediate speed. It was observed that the grindability increased with an increase in the Cu concentration compared to CP Ti, particularly for the 5 or 10% Cu alloys at a circumferential speed of 1000 m/min or above. By alloying with copper, the cast titanium exhibited better grindability at high speed. The continuous precipitation of Ti(2)Cu among the alpha-matrix grains made this material less ductile and facilitated more effective grinding because small broken segments more readily formed.

Dynamic Shear Deformation and Failure of Ti-6Al-4V and Ti-5Al-5Mo-5V-1Cr-1Fe Alloys

PubMed Central

Chen, Pengwan

2018-01-01

To study the dynamic shear deformation and failure properties of Ti-6Al-4V (Ti-64) alloy and Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy, a series of forced shear tests on flat hat shaped (FHS) specimens for the two investigated materials was performed using a split Hopkinson pressure bar setup. The evolution of shear deformation was monitored by an ultra-high-speed camera (Kirana-05M). Localized shear band is induced in the two investigated materials under forced shear tests. Our results indicate that severe strain localization (adiabatic shear) is accompanied by a loss in the load carrying capacity, i.e., by a sudden drop in loading. Three distinct stages can be identified using a digital image correlation technique for accurate shear strain measurement. The microstructural analysis reveals that the dynamic failure mechanisms for Ti-64 and Ti-55511 alloys within the shear band are of a cohesive and adhesive nature, respectively. PMID:29303988

Preparation of Al-La Master Alloy by Thermite Reaction in NaF-NaCl-KCl Molten Salt

NASA Astrophysics Data System (ADS)

Jang, Poknam; Li, Hyonmo; Kim, Wenjae; Wang, Zhaowen; Liu, Fengguo

2015-05-01

A NaF-NaCl-KCl ternary system containing La2O3 was investigated for the preparation of Al-La master alloy by the thermite reaction method. The solubility of La2O3 in NaF-NaCl-KCl molten salt was determined by the method of isothermal solution saturation. Inductively coupled plasma-optical emission spectroscopy and x-ray diffraction (XRD) analyses were used to consider the content of La2O3 in molten salt and the supernatant composition of molten salt after dissolution of La2O3, respectively. The results showed that the content of NaF had a positive influence on the solubility of La2O3 in NaF-NaCl-KCl molten salts, and the solubility of La2O3 could reach 8.71 wt.% in molten salts of 50 wt.%NaF-50 wt.% (44 wt.%NaCl + 56 wt.%KCl). The XRD pattern of cooling molten salt indicated the formation of LaOF in molten salt, which was probably obtained by the reaction between NaF and La2O3. The kinetic study showed that the thermite reaction was in accord with a first-order reaction model. The main influence factors on La content in the Al-La master alloy product, including molten salt composition, amount of Al, concentration of La2O3, stirring, reduction time and temperature, were investigated by single-factor experimentation. The content of La in the Al-La master alloy could be reached to 10.1 wt.%.

A Novel Process for Joining Ti Alloy and Al Alloy using Two-Stage Sintering Powder Metallurgy

NASA Astrophysics Data System (ADS)

Long, Luping; Liu, Wensheng; Ma, Yunzhu; Wu, Lei; Liu, Chao

2018-04-01

The major challenges for conventional diffusion bonding of joining Ti alloy and Al alloy are the undesirable interfacial reaction, low matrixes and joint strength. To avoid the problem in diffusion bonding, a novel two-stage sintering powder metallurgy process is developed. In the present work, the interface characterization and joint performance of the bonds obtained by powder metallurgy bonding are investigated and are compared with the diffusion bonded Ti/Al joints obtained with the same and the optimized process parameters. The results show that no intermetallic compound is visible in the Ti/Al joint obtained by powder metallurgy bonding, while a new layer formed at the joint diffusion bonded with the same parameters. The maximum tensile strength of joint obtained by diffusion bonding is 58 MPa, while a higher tensile strength reaching 111 MPa for a bond made by powder metallurgy bonding. Brittle fractures occur at all the bonds. It is shown that the powder metallurgy bonding of Ti/Al is better than diffusion bonding. The results of this study should benefit the bonding quality.

Preliminary study on the corrosion resistance, antibacterial activity and cytotoxicity of selective-laser-melted Ti6Al4V-xCu alloys.

PubMed

Guo, Sai; Lu, Yanjin; Wu, Songquan; Liu, Lingling; He, Mengjiao; Zhao, Chaoqian; Gan, Yiliang; Lin, Junjie; Luo, Jiasi; Xu, Xiongcheng; Lin, Jinxin

2017-03-01

In this study, a series of Cu-bearing Ti6Al4V-xCu (x=0, 2, 4, 6wt%) alloys (shorten by Ti6Al4V, 2C, 4C, and 6C, respectively.) with antibacterial function were successfully fabricated by selective laser melting (SLM) technology with mixed spherical powders of Cu and Ti6Al4V for the first time. In order to systematically investigate the effects of Cu content on the microstructure, phase constitution, corrosion resistance, antibacterial properties and cytotoxicity of SLMed Ti6Al4V-xCu alloys, experiments including XRD, SEM-EDS, electrochemical measurements, antibacterial tests and cytotoxicity tests were conducted with comparison to SLMed Ti6Al4V alloy (Ti6Al4V). Microstructural observations revealed that Cu had completely fused into the Ti6Al4V alloy, and presented in the form of Ti 2 Cu phase at ambient temperature. With Cu content increase, the density of the alloy gradually decreased, and micropores were obviously found in the alloy. Electrochemical measurements showed that corrosion resistance of Cu-bearing alloys were stronger than Cu-free alloy. Antibacterial tests demonstrated that 4C and 6C alloys presented strong and stable antibacterial property against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) compared to the Ti6Al4V and 2C alloy. In addition, similar to the Ti6Al4V alloy, the Cu-bearing alloys also exerted good cytocompatibility to the Bone Marrow Stromal Cells (BMSCs) from Sprague Dawley (SD) rats. Based on those results, the preliminary study verified that it was feasible to fabricated antibacterial Ti6Al4V-xCu alloys direct by SLM processing mixed commercial Ti6Al4V and Cu powder. Copyright © 2016 Elsevier B.V. All rights reserved.

The Effect of Coatings on the Wear Behavior of Ti6Al4V Alloy Used in Biomedical Applications

NASA Astrophysics Data System (ADS)

Danışman, Ş.; Odabas, D.; Teber, M.

2018-01-01

The properties expected from implant materials are biocompatibility, long service life and wear resistance. The wear resistance of the implant materials varies according to the type of implant, usage area and the movement. The ability of implant material to be more compatible with biological tissues and to increase the useful life depends on the surface properties. Today many different kind of surface modification techniques are applying on medical and dental implant surfaces to improve surface specifications and wear resistance. In this study TiN, TiAlN, TiCN coatings were applied on Ti6Al4V alloy used as implant material by reactive magnetron sputtering method. The wear resistances of uncoated Ti6Al4V alloy and TiN, TiAlN, TiCN coatings were investigated at room temperature under dry conditions. The wear resistance at different load and different sliding rates were compared using an wear tester. The wear losses, wear track widths and friction coefficients of coated and uncoated Ti6Al4V alloys are taken into account for comparison. The results show that a significant improvement in wear resistance of the alloy with the coating is achieved and TiN-coated Ti6Al4V alloy has the highest wear resistance.

Mechanical Properties of the TiAl IRIS Alloy

NASA Astrophysics Data System (ADS)

Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

2016-12-01

This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

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.

Surface modification by electrolytic plasma processing for high Nb-TiAl alloys

NASA Astrophysics Data System (ADS)

Gui, Wanyuan; Hao, Guojian; Liang, Yongfeng; Li, Feng; Liu, Xiao; Lin, Junpin

2016-12-01

Metal surface modification by electrolytic plasma processing (EPP) is an innovative treatment widely commonly applied to material processing and pretreatment process of coating and galvanization. EPP involves complex processes and a great deal of parameters, such as preset voltage, current, solution temperature and processing time. Several characterization methods are presented in this paper for evaluating the micro-structure surfaces of Ti45Al8Nb alloys: SEM, EDS, XRD and 3D topography. The results showed that the oxide scale and other contaminants on the surface of Ti45Al8Nb alloys can be effectively removed via EPP. The typical micro-crater structure of the surface of Ti45Al8Nb alloys were observed by 3D topography after EPP to find that the mean diameter of the surface structure and roughness value can be effectively controlled by altering the processing parameters. The mechanical properties of the surface according to nanomechanical probe testing exhibited slight decrease in microhardness and elastic modulus after EPP, but a dramatic increase in surface roughness, which is beneficial for further processing or coating.

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. © 2013 Elsevier Ltd. All rights reserved.

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

2016-11-01

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.

Effect of Al content on structure and mechanical properties of the Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yurchenko, N.Yu.

2016-11-15

In present study, structure and mechanical properties of the Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys after arc melting and annealing at 1200 °C for 24 h are investigated. The CrNbTiVZr alloy is composed of body centered cubic (bcc) and C15 (face centered cubic) Laves phases while the Al{sub x}CrNbTiVZr (x = 0.25; 0.5; 1) alloys consist of bcc and two C14 (hexagonal close packed) Laves phases with different chemical compositions. Thermodynamic modeling predicts existence of two phases – bcc and C15 Laves phase and broadening of single bcc phase field due to Al addition. The densitymore » of the alloys decreases with the increase of Al content. The alloys are found to be extremely brittle at room temperature and 600 °C. The alloys have high strength at temperatures of 800–1000 °C. For example, yield strength at 800 °C increases from 440 MPa for the CrNbTiVZr alloy to 1250 MPa for the AlCrNbTiVZr alloy. The experimental phase composition of the Al{sub x}CrNbTiVZr alloys is compared with predicted equilibrium phases and the factors governing the transformation of C15 to C14 Laves phases due to Al addition to the CrNbTiVZr alloy analyzed. Specific properties of the alloys are compared with other high-entropy alloys and commercial Ni-based superalloys. - Highlights: •Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) alloys are arc melted and annealed at 1200 °C. •The CrNbTiVZr alloy has bcc and C15 Laves phases. •The Al-containing alloys are composed of bcc and two C14 Laves phases. •The alloys demonstrate high specific strength at temperatures of 800 °C and 1000 °C. •The strength of the alloys increases in proportion with increase of Al content.« less

Characterization of an Additive Manufactured TiAl Alloy-Steel Joint Produced by Electron Beam Welding.

PubMed

Basile, Gloria; Baudana, Giorgio; Marchese, Giulio; Lorusso, Massimo; Lombardi, Mariangela; Ugues, Daniele; Fino, Paolo; Biamino, Sara

2018-01-17

In this work, the characterization of the assembly of a steel shaft into a γ-TiAl part for turbocharger application, obtained using Electron Beam Welding (EBW) technology with a Ni-based filler, was carried out. The Ti-48Al-2Nb-0.7Cr-0.3Si (at %) alloy part was produced by Electron Beam Melting (EBM). This additive manufacturing technology allows the production of a lightweight part with complex shapes. The replacement of Nickel-based superalloys with TiAl alloys in turbocharger automotive applications will lead to an improvement of the engine performance and a substantial reduction in fuel consumption and emission. The welding process allows a promising joint to be obtained, not affecting the TiAl microstructure. Nevertheless, it causes the formation of diffusive layers between the Ni-based filler and both steel and TiAl, with the latter side being characterized by a very complex microstructure, which was fully characterized in this paper by means of Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and nanoindentation. The diffusive interface has a thickness of about 6 µm, and it is composed of several layers. Specifically, from the TiAl alloy side, we find a layer of Ti₃Al followed by Al₃NiTi₂ and AlNi₂Ti. Subsequently Ni becomes more predominant, with a first layer characterized by abundant carbide/boride precipitation, and a second layer characterized by Si-enrichment. Then, the chemical composition of the Ni-based filler is gradually reached.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganjeh, E., E-mail: navidganjehie@sina.kntu.ac.ir; Sarkhosh, H.; Bajgholi, M.E.

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 andmore » 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

Atomistic Modeling of Quaternary Alloys: Ti and Cu in NiAl

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Mosca, Hugo O.; Wilson, Allen W.; Noebe, Ronald D.; Garces, Jorge E.

2002-01-01

The change in site preference in NiAl(Ti,Cu) alloys with concentration is examined experimentally via ALCHEMI and theoretically using the Bozzolo-Ferrante-Smith (BFS) method for alloys. Results for the site occupancy of Ti and Cu additions as a function of concentration are determined experimentally for five alloys. These results are reproduced with large-scale BFS-based Monte Carlo atomistic simulations. The original set of five alloys is extended to 25 concentrations, which are modeled by means of the BFS method for alloys, showing in more detail the compositional range over which major changes in behavior occur. A simple but powerful approach based on the definition of atomic local environments also is introduced to describe energetically the interactions between the various elements and therefore to explain the observed behavior.

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

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. Copyright 2004 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 717-724, 2004

Preparation of silicon target material by adding Al-B master alloy in directional solidification

NASA Astrophysics Data System (ADS)

Li, Pengting; Wang, Kai; Ren, Shiqiang; Jiang, Dachuan; Tan, Yi

2017-03-01

The silicon target material was prepared by adding Al-6B master alloy in directional solidification. The microstructure was characterized and the resistivity was studied in this work. The results showed that the purity of the silicon target material was more than 99.999% (5N). The resistivity was ranges from 0.002 to 0.030 Ω·cm along the ingot height. It was revealed that the particles of AlB2 in Al-6B master alloy would react spontaneously and generate clusters of [B] and [Al] in molten silicon at 1723 K. After directional solidification, the content of B and Al were increasing gradually with the increase of solidified fraction. The measured values of B were in good agreement with the curve of the Scheil equation below 80% of the ingot height. The mean concentration of B was about 17.20 ppmw and the mean concentration of Al was about 8.07 ppmw after directional solidification. The measured values of Al were fitting well with the curve of values which the effective segregation coefficient was 0.00378. It was observed that B co-doped Al in directional solidification polysilicon could regulate resistivity mutually. This work provides the theoretical basis and technical support for industrial production of the silicon target material.

Fabrication of Intermetallic Titanium Alloy Based on Ti2AlNb by Rapid Quenching of Melt

NASA Astrophysics Data System (ADS)

Senkevich, K. S.; Serov, M. M.; Umarova, O. Z.

2017-11-01

The possibility of fabrication of rapidly quenched fibers from alloy Ti - 22Al - 27Nb by extracting a hanging melt drop is studied. The special features of the production of electrodes for spraying the fibers by sintering mechanically alloyed powdered components of the alloy, i.e., titanium hydride, niobium, and aluminum dust, are studied. The rapidly quenched fibers with homogeneous phase composition and fine-grained structure produced from alloy Ti - 22Al - 27Nb are suitable for manufacturing compact semiproducts by hot pressing.

Thermal Shock and Oxidation Behavior of HiPIMS TiAlN Coatings Grown on Ti-48Al-2Cr-2Nb Intermetallic Alloy

PubMed Central

Badini, Claudio; Deambrosis, Silvia M.; Padovano, Elisa; Fabrizio, Monica; Ostrovskaya, Oxana; Miorin, Enrico; D’Amico, Giuseppe C.; Montagner, Francesco; Biamino, Sara; Zin, Valentina

2016-01-01

A High Power Impulse Magnetron Sputtering (HiPIMS) method for depositing TiAlN environmental barrier coatings on the surface of Ti-48Al-2Cr-2Nb alloy was developed in view of their exploitation in turbine engines. Three differently engineered TiAlN films were processed and their performance compared. Bare intermetallic alloy coupons and coated specimens were submitted to thermal cycling under oxidizing atmosphere up to 850 °C or 950 °C, at high heating and cooling rates. For this purpose, a burner rig able to simulate the operating conditions of the different stages of turbine engines was used. Microstructures of the samples were compared before and after each test using several techniques (microscopy, XRD, and XPS). Coating-intermetallic substrate adhesion and tribological properties were investigated too. All the TiAlN films provided a remarkable increase in oxidation resistance. Good adhesion properties were observed even after repeated thermal shocks. HiPIMS pretreatments of the substrate surfaces performed before the coating deposition significantly affected the oxidation rate, the oxide layer composition and the coating/substrate adhesion. PMID:28774082

Thermophysical properties of substantially undercooled liquid Ti-Al-Nb ternary alloy measured by electromagnetic levitation

NASA Astrophysics Data System (ADS)

Zhou, K.; Wang, H. P.; Wei, B.

2013-03-01

The thermophysical properties of undercooled liquid alloys at high temperature are usually difficult to measure by experiment. Here, we report the specific heat of liquid Ti45Al45Nb10 ternary alloy in the undercooled state. By using electromagnetic levitation technique, a maximum undercooling of 287 K (0.15 T L) is achieved for this alloy. Its specific heat is determined to be 32.72 ± 2.51 J mol-1 K-1 over a broad temperature range of 1578-2010 K.

Low elastic modulus Ti-Ta alloys for load-bearing permanent implants: enhancing the biodegradation resistance by electrochemical surface engineering.

PubMed

Kesteven, Jazmin; Kannan, M Bobby; Walter, Rhys; Khakbaz, Hadis; Choe, Han-Choel

2015-01-01

In this study, the in vitro degradation behaviour of titanium-tantalum (Ti-Ta) alloys (10-30 wt.% Ta) was investigated and compared with conventional implant materials, i.e., commercially pure titanium (Cp-Ti) and titanium-aluminium-vanadium (Ti6Al4V) alloy. Among the three Ti-Ta alloys studied, the Ti20Ta (6.3×10(-4) mm/y) exhibited the lowest degradation rate, followed by Ti30Ta (1.2×10(-3) mm/y) and Ti10Ta (1.4×10(-3) mm/y). All the Ti-Ta alloys exhibited lower degradation rate than that of Cp-Ti (1.8×10(-3) mm/y), which suggests that Ta addition to Ti is beneficial. As compared to Ti6Al4V alloy (8.1×10(-4) mm/y), the degradation rate of Ti20Ta alloy was lower by ~22%. However, the Ti30Ta alloy, which has closer elastic modulus to that of natural bone, showed ~48% higher degradation rate than that of Ti6Al4V alloy. Hence, to improve the degradation performance of Ti30Ta alloy, an intermediate thin porous layer was formed electrochemically on the alloy followed by calcium phosphate (CaP) electrodeposition. The coated Ti30Ta alloy (3.8×10(-3) mm/y) showed ~53% lower degradation rate than that of Ti6Al4V alloy. Thus, the study suggests that CaP coated Ti30Ta alloy can be a viable material for load-bearing permanent implants. Copyright © 2014 Elsevier B.V. All rights reserved.

Carbon fibers coated with graphene reinforced TiAl alloy composite with high strength and toughness.

PubMed

Cui, Sen; Cui, Chunxiang; Xie, Jiaqi; Liu, Shuangjin; Shi, Jiejie

2018-02-05

To meet the more rigorous requirement in aerospace industry, recent studies on strengthening and toughening TiAl alloys mostly focus on high Nb addition, which inevitably bring in an increasing of density. In this study, a carbon fibers coated with graphene reinforced TiAl alloy composite was fabricated by powder metallurgy, melt spun and vacuum melting. This composite got remarkable mechanical properties combined with a prominent density reduction. In contrast with pure TiAl ingots, this sample exhibits an average fracture strain from 16% up to 26.27%, and an average strength from 1801 MPa up to 2312 MPa. Thus, we can achieve a new method to fabricate this low-density, good mechanical performance TiAl composite which could bring in more opportunities for application in aerospace industry.

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

Thermomechanical processing of aluminum micro-alloyed with Sc, Zr, Ti, B, and C

NASA Astrophysics Data System (ADS)

McNamara, Cameron T.

Critical exploration of the minimalistic high strength low alloy aluminum (HSLA-Al) paradigm is necessary for the continued development of advanced aluminum alloys. In this study, scandium (Sc) and zirconium (Zr) are examined as the main precipitation strengthening additions, while magnesium (Mg) is added to probe the synergistic effects of solution and precipitation hardening, as well as the grain refinement during solidification afforded by a moderate growth restriction factor. Further, pathways of recrystallization are explored in several potential HSLA-Al syste =ms sans Sc. Aluminum-titanium-boron (Al-Ti-B) and aluminum-titanium-carbon (Al-Ti-C) grain refining master alloys are added to a series of Al-Zr alloys to examine both the reported Zr poisoning effect on grain size reduction and the impact on recrystallization resistance through the use of electron backscattered diffraction (EBSD) imaging. Results include an analysis of active strengthening mechanisms and advisement for both constitution and thermomechanical processing of HSLA-Al alloys for wrought or near-net shape cast components. The mechanisms of recrystallization are discussed for alloys which contain a bimodal distribution of particles, some of which act as nucleation sites for grain formation during annealing and others which restrict the growth of the newly formed grains.

Effects of Insert Metal Type on Interfacial Microstructure During Dissimilar Joining of TiAl Alloy to SCM440 by Friction Welding

NASA Astrophysics Data System (ADS)

Park, Jong-Moon; Kim, Ki-Young; Kim, Kyoung-Kyun; Ito, Kazuhiro; Takahashi, Makoto; Oh, Myung-Hoon

2018-05-01

Although the welding zone of direct bonding between a TiAl alloy and SCM440 can be obtained by friction welding, martensitic transformation and the formation of intermetallic compounds (IMCs) and cracks result in a lower tensile strength of the joints relative to those of other welding techniques. Insert metals were used as a buffer layer to relieve stress while increasing the bond strength. In this study, the microstructure and mechanical properties on welded joints of a TiAl alloy and SCM440 with various insert metals, were investigated. The TiAl/Cu/SCM440 and TiAl/Ni/SCM440 joints were fabricated using a servo-motor-type friction welding machine. As a result, it was confirmed that the formation of a welding flash was dependent on the insert metal type, and the strength of the base metal. At the TiAl/Cu/SCM440 interface, the formation of IMCs CuTiAl and Cu2TiAl was observed at TiAl/Cu, while no IMC formation was observed at Cu/SCM440. On the other hand, at the TiAl/Ni/SCM440 interface, several IMCs with more than 100 μm thickness were found, and roughly two compositions, viz., Ti2NiAl3 and TiNi2Al, were observed at the TiAl/Ni interface. At the Ni/SCM440 interface, 10 μm-thick FeNi and others were found.

Use of B4C powder for preparing in situ Al-Ti-B-C inoculant in Al-Ti melt and its refining effect on A356 alloy

NASA Astrophysics Data System (ADS)

Liu, Shuiqing; Cui, Chunxiang; Wang, Xin; Zhao, Lichen; Sun, Yijiao; Shi, Jiejie; Cui, Sen; Ding, Jinhua

2018-01-01

A novel preparation technology of Al-Ti-B-C inoculant with uniform microstructure is prepared using B4C powder instead of graphite in Al-Ti melt reaction method in this study. It is found that the addition of B4C powder improves the wettability between carbon element and liquid aluminum and reduce the tendency to the gravity segregation simultaneously. The result shows that Al-Ti-B-C inoculant using B4C powder presents excellent grain refinement performance than the conventional approach. After T6 heat treatment, the ultimate tensile strength, the yield strength and elongation of A356 alloy are increased to 292 ± 6 MPa, 238 ± 7 MPa and 8.2% ± 0.5% from 260 ± 7 MPa, 218 ± 5 MPa and 4.9% ± 0.6% by addition of Al-Ti-B-C inoculant with a very small ratio of 0.3% in weight. The increase of strength in Al-Ti-B-C refined alloy is attributed to the grain refinement of primary α-Al, while the increase of ductility results from the submicron particles in Al-Ti-B-C inoculant adsorb impurity atoms as well as decreased grain size.

Wear Resistance Enhancement of Ti-6Al-4 V Alloy by Applying Zr-Modified Silicide Coatings

NASA Astrophysics Data System (ADS)

Li, Xuan; Hu, Guangzhong; Tian, Jin; Tian, Wei; Xie, Wenling; Li, Xiulan

2018-03-01

Zr-modified silicide coatings were prepared on Ti-6Al-4 V alloy by pack cementation process to enhance its wear resistance. The microstructure and wear properties of the substrate and the coatings were comparatively investigated using GCr15 and Al2O3 as the counterparts under different sliding loads. The obtained Zr-modified silicide coating had a multilayer structure, consisting of a thick (Ti, X)Si2 (X represents Al, Zr and V elements) outer layer, a TiSi middle layer and a Ti5Si4 + Ti5Si3 inner layer. The micro-hardness of the coating was much higher than the substrate and displayed a decrease tendency from the coating surface to the interior. Sliding against either GCr15 or Al2O3 balls, the coatings showed superior anti-friction property to the Ti-6Al-4 V alloy, as confirmed by its much lower wear rate under each employed sliding condition.

Osteogenic potential of a novel microarc oxidized coating formed on Ti6Al4V alloys

NASA Astrophysics Data System (ADS)

Wang, Yaping; Lou, Jin; Zeng, Lilan; Xiang, Junhuai; Zhang, Shufang; Wang, Jun; Xiong, Fucheng; Li, Chenglin; Zhao, Ying; Zhang, Rongfa

2017-08-01

In order to improve the biocompatibility, Ti6Al4V alloys are processed by micro arc oxidation (MAO) in a novel electrolyte of phytic acid, a natural organic phosphorus-containing matter. The MAO coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The cytocompatibility of Ti6A14V alloys before and after MAO were comprehensively evaluated. The results showed that the fabricated MAO coatings were composed of rutile, anatase, TiP2O7 as well as some OH- groups, exhibiting the excellent hydrophilicity and a porous structure with small micro pores. No cytotoxicity towards MC3T3-E1cells was observed in this study. In particular, MAO treated Ti6Al4V alloys presented comparable cell adhesion and proliferation as well as significantly enhanced alkaline phosphatase activity, extracellular matrix (ECM) mineralization and collagen secretion in comparison with the untreated control. The results suggest that the Ti6Al4V alloys treated by MAO in phytic acid can be used as implants for orthopaedic applications, providing a simple and practical method to widen clinical acceptance of titanium alloys.

A preliminary research on the mechanical properties of TiAl + Ti{sub 5}Si{sub 3} dual phase alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, L.; Qiu, G.; Wu, J.

A sufficient Si addition to TiAl matrix has led to TiAl + Ti{sub 5}Si{sub 3} dual phase alloys, showing coupled-growth microstructure. Compression tests at R.T. as well as high temp indicated that the yield stress increased with increasing Ti{sub 5}Si{sub 3} volume fraction, and decreased at higher temperature. The reinforcement from Ti{sub 5}Si{sub 3} phase was obvious while high Si and Al contents resulted in low ductility. The fracture surfaces were quasi-cleavage. Further research should concern with the adjustment of the shape and amount of the second phase.

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Microstructure and properties of Ti-Al intermetallic/Al2O3 layers produced on Ti6Al2Mo2Cr titanium alloy by PACVD method

NASA Astrophysics Data System (ADS)

Sitek, R.; Bolek, T.; Mizera, J.

2018-04-01

The paper presents investigation of microstructure and corrosion resistance of the multi-component surface layers built of intermetallic phases of the Ti-Al system and an outer Al2O3 ceramic sub-layer. The layers were produced on a two phase (α + β) Ti6Al2Mo2Cr titanium alloy using the PACVD method with the participation of trimethylaluminum vapors. The layers are characterized by a high surface hardness and good corrosion, better than that of these materials in the starting state. In order to find the correlation between their structure and properties, the layers were subjected to examinations using optical microscopy, X-ray diffraction analysis (XRD), surface analysis by XPS, scanning electron microscopy (SEM), and analyses of the chemical composition (EDS). The properties examined included: the corrosion resistance and the hydrogen absorptiveness. Moreover growth of the Al2O3 ceramic layer and its influence on the residual stress distribution was simulated using finite element method [FEM]. The results showed that the produced layer has amorphous-nano-crystalline structure, improved corrosion resistance and reduces the permeability of hydrogen as compared with the base material of Ti6Al2Mo2Cr -titanium alloy.

Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys

PubMed Central

Shi, Chengcheng; Jiang, Shaosong; Zhang, Kaifeng

2017-01-01

This paper focuses on the fabrication of as-forged Ti46.5Al2Cr1.8Nb-(W, B) alloy via pulse current auxiliary isothermal forging (PCIF). The starting material composed of near gamma (NG) microstructure was fabricated by adopting pre-alloyed powders via hot pressing sintering (HPS) at 1300 °C. Isothermal compression tests were conducted at a strain rate range of 0.001–0.1 s−1 and a temperature range of 1125–1275 °C to establish the constitutive model and processing map. The optimal hot deformation parameters were successfully determined (in a strain rate range of 10−3–2.5 × 10−3 s−1 and temperature range of 1130–1180 °C) based on the hot processing map and microstructure observation. Accordingly, an as-forged TiAl based alloy without cracks was successfully fabricated by PCIF processing at 1175 °C with a nominal strain rate of 10−3 s−1. Microstructure observation indicated that complete dynamic recrystallization (DRX) and phase transformation of γ→α2 occurred during the PCIF process. The elongation of as-forged alloy was 136%, possessing a good secondary hot workability, while the sintered alloy was only 66% when tested at 900 °C with a strain rate of 2 × 10−4 s−1. PMID:29258198

Hot Deformation Behavior and Pulse Current Auxiliary Isothermal Forging of Hot Pressing Sintering TiAl Based Alloys.

PubMed

Shi, Chengcheng; Jiang, Shaosong; Zhang, Kaifeng

2017-12-16

This paper focuses on the fabrication of as-forged Ti46.5Al2Cr1.8Nb-(W, B) alloy via pulse current auxiliary isothermal forging (PCIF). The starting material composed of near gamma (NG) microstructure was fabricated by adopting pre-alloyed powders via hot pressing sintering (HPS) at 1300 °C. Isothermal compression tests were conducted at a strain rate range of 0.001-0.1 s -1 and a temperature range of 1125-1275 °C to establish the constitutive model and processing map. The optimal hot deformation parameters were successfully determined (in a strain rate range of 10 -3 -2.5 × 10 -3 s -1 and temperature range of 1130-1180 °C) based on the hot processing map and microstructure observation. Accordingly, an as-forged TiAl based alloy without cracks was successfully fabricated by PCIF processing at 1175 °C with a nominal strain rate of 10 -3 s -1 . Microstructure observation indicated that complete dynamic recrystallization (DRX) and phase transformation of γ→α₂ occurred during the PCIF process. The elongation of as-forged alloy was 136%, possessing a good secondary hot workability, while the sintered alloy was only 66% when tested at 900 °C with a strain rate of 2 × 10 -4 s -1 .

Understanding fracture toughness in gamma TiAl

NASA Astrophysics Data System (ADS)

Chan, Kwai S.

1992-05-01

The ambient-temperature ductility and fracture toughness of TiAl-base intermetallic alloys have been improved in recent years by both alloy additions and microstructural control. Two-phase TiAl alloys have emerged as a new class of lightweight, high-temperature materials with potential importance for aerospace applications. This overview summarizes recent advances in the basic understanding of the fracture processes and toughening mechanisms in TiAl-base alloys and the relationships between microstructures and mechanical properties.

Phase transformations involving the [alpha][sub 2] and O phases in Ti-Al-Nb alloys. [Ti-28. 5Al-13Nb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muraleedharan, K.; Banerjee, D.

1993-08-15

An orthorhombic (O) phase with Cmcm space group and Ti[sub 2]AlNb composition has ben established in the Ti-Al-Nb system. Efforts to develop alloys with this orthorhombic phase as a major phase, in place of the [alpha][sub 2] (Ti[sub 3]Al) phase, resulted in compositions with superior combinations of strength and toughness. The determination of phase diagrams for the Ti-Al-Nb system is a continuing effort. Bendersky et al. considered possible transformation paths and the hierarchy of structures in going from the [beta] phase to [alpha][sub 2] or O phases through displacive or replacive reactions. Microstructures predicted by these considerations have been documentedmore » in the particularly well investigated [beta]-->O transformation. Very little work has however been carried out on the [alpha][sub 2]-->O phase transformation. In this paper, the authors report preliminary results of isothermal aging study of this transformation.« less

Origin of Surface Irregularities on Ti-10V-2Fe-3Al Beta Titanium Alloy

NASA Astrophysics Data System (ADS)

Utama, Muhammad Iman; Ammar, Abdul Aziz; Park, Nokeun; Baek, Eung Ryul

2018-03-01

We studied the origin of different characteristics and properties of a Ti-10V-2Fe-3Al beta (β) titanium alloy with surface height irregularities that occurred during machining. The height differences were observed in two different regions, labeled as "soft region" and "hard region." The present study showed a higher Fe and a lower Al content in the hard region, which resulted in higher β-phase stability to resist primary alpha (αp) phase precipitation caused by a failure of the solution treatment process. In contrast, the soft region contained a higher volume fraction of αp phase and a lower volume fraction of the matrix, which consisted of a combination of β and secondary alpha (αs) phase. A high number of αs/β interface in the matrix with a predicted hardness of 520 HV generated an improvement of hardness in the hard region. Therefore, the hard and the soft regions had different abilities to resist wear during machining process, resulting in surface height irregularities.

Synthesis of aluminum-based scandium-yttrium master alloys

NASA Astrophysics Data System (ADS)

Bazhin, V. Yu.; Kosov, Ya. I.; Lobacheva, O. L.; Dzhevaga, N. V.

2015-07-01

The preparation technology for an Al-2% Sc-0.5% Y master alloy using aluminum-manganese alloys has been developed and tested. The microstructure of the prepared master alloy is studied and the compositions of intermetallics is determined. The efficient technological parameters of the synthesis are determined. It is shown that varying the compositions of starting reagents and alloying additions and optimizing the process conditions (temperature, mixing, etc.) allow us to forecast the manufacturing and operating characteristics of aluminum-based master alloys. Joint additions of scandium and yttrium oxides to a charge favor a substantial decrease in the grain size of the formed intermetallics; this effect appears to the utmost in the case of microallying with yttrium up to 0.5 wt %.

Effects of Duplex Nitriding and TiN Coating Treatment on Wear Resistance, Corrosion Resistance and Biocompatibility of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Kao, W. H.; Su, Y. L.; Hsieh, Y. T.

2017-08-01

Ti6Al4V alloy substrates were nitrided at 900 °C. TiN coatings were then deposited on the nitrided substrates using a closed-field unbalanced magnetron sputtering system. The microstructure, hardness and adhesion properties of the TiN-N-Ti6Al4V substrates were evaluated and compared with those of an untreated Ti6Al4V sample, a nitrided Ti6Al4V sample and a TiN-coated Ti6Al4V sample, respectively. The tribological properties of the various samples were investigated by means of reciprocating sliding wear tests performed in 0.9 wt.% NaCl solution against 316L, Si3N4 and Ti6Al4V balls, respectively. In addition, the corrosion resistance was evaluated using potentiodynamic polarization tests. Finally, the biocompatibility of the samples was investigated by observing the attachment and growth of purified mouse leukemic monocyte/macrophage cells (Raw 264.7) on the sample surface after culturing periods of 24, 72 and 120 h, respectively. Overall, the results showed that the duplex nitriding/TiN coating treatment significantly improved the tribological, anti-corrosion and biocompatibility properties of the original Ti6Al4V alloy.

Fit of cast commercially pure titanium and Ti-6Al-4V alloy crowns before and after marginal refinement by electrical discharge machining.

PubMed

Contreras, Edwin Fernando Ruiz; Henriques, Guilherme Elias Pessanha; Giolo, Suely Ruiz; Nobilo, Mauro Antonio Arruda

2002-11-01

Titanium has been suggested as a replacement for alloys currently used in single-tooth restorations and fixed partial dentures. However, difficulties in casting have resulted in incomplete margins and discrepancies in marginal fit. This study evaluated and compared the marginal fit of crowns fabricated from a commercially pure titanium (CP Ti) and from Ti-6Al-4V alloy with crowns fabricated from a Pd-Ag alloy that served as a control. Evaluations were performed before and after marginal refinement by electrical discharge machining (EDM). Forty-five bovine teeth were prepared to receive complete cast crowns. Stone and copper-plated dies were obtained from impressions. Fifteen crowns were cast with each alloy (CP Ti, Ti-6Al-4V, and Pd-Ag). Marginal fit measurements (in micrometers) were recorded at 4 reference points on each casting with a traveling microscope. Marginal refinement with EDM was conducted on the titanium-based crowns, and measurements were repeated. Data were analyzed with the Kruskal-Wallis test, paired t test, and independent t test at a 1% probability level. The Kruskal-Wallis test showed significant differences among mean values of marginal fit for the as-cast CP Ti crowns (mean [SD], 83.9 [26.1] microm) and the other groups: Ti-6Al-4V (50.8 [17.2] microm) and Pd-Ag (45.2 [10.4] microm). After EDM marginal refinement, significant differences were detected among the Ti-6Al-4V crowns (24.5 [10.9] microm) and the other 2 groups: CP Ti (50.6 [20.0] microm) and Pd-Ag (not modified by EDM). Paired t test results indicated that marginal refinement with EDM effectively improved the fit of CP Ti crowns (from 83.9 to 50.6 microm) and Ti-6Al-4V crowns (from 50.8 to 24.5 microm). However, the difference in improvement between the two groups was not significant by t test. Within the limitations of this study, despite the superior results for Ti-6Al-4V, both groups of titanium-based crowns had clinically acceptable marginal fits. After EDM marginal refinement

First-principles study of intermetallic phase stability in the ternary Ti-Al-Nb alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asta, M.; Ormeci, A.; Wills, J.M.

The stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong orderingmore » tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti{sub 2}AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.« less

INFLUENCE OF THE FINAL TEMPERATURE OF INVESTMENT HEALTING ON THE TENSILE STRENGTH AND VICKERS HARDNESS OF CP TI AND TI-6AL-4V ALLOY

PubMed Central

Oliveira, Pedro César Garcia; Adabo, Gelson Luis; Ribeiro, Ricardo Faria; da Rocha, Sicknan Soares; Ávila, Fabiano Araújo; do Valle, Accácio Lins

2007-01-01

The aim of the work was to evaluate the influence of the temperature of investment healting on the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy casting. Were obtained for the tensile strength test dumbbell rods that were invested in the Rematitan Plus investment and casting in the Discovery machine cast. Thirty specimens were obtained, fiftten to the CP Titanium and fifteen to the Ti-6Al-4V alloy, five samples to each an of the three temperatures of investment: 430°C (control group), 480°C and 530°C. The tensile test was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile strenght test the specimens were secctioned, embedded and polished to hardness measurements, using a Vickers tester, Micromet 2100. The means values to tensile tests to the temperatures 430°C, 480 and 530: CP Ti (486.1 – 501.16 – 498.14 –mean 495.30 MPa) and Ti-6Al-4V alloy (961.33 – 958.26 – 1005.80 – mean 975.13 MPa) while for the Vickers hardness the values were (198.06, 197.85, 202.58 – mean 199.50) and (352.95, 339.36, 344.76 – mean 345.69), respectively. The values were submitted to Analysis of Variance (ANOVA) and Tukey,s Test that indicate differences significant only between the materials, but not between the temperature, for both the materias. It was conclued that increase of the temperature of investment its not chance the tensile strength and the Vickers hardness of the CP Titanium and Ti-6Al-4V alloy. PMID:19089099

Designing Gamma TiAl Alloys (K5 Based) for Use at 840 C and Above

NASA Technical Reports Server (NTRS)

Kim, Young-Won; Kim, Sang-Lan

2002-01-01

The objective of this program was to investigate how carbon additions and Al content variation affects RT tensile properties and creep performance in gamma TiAl alloys. On the basis of the results from the work four alloys were selected within the composition range of Ti-(44.7-47.0) Al-(1.0-1.7)Cr-3.0Nb-0.2W-0.2B-(0.23-0.43)C-(0, 0.2)Si. Through extensive annealing/aging experiments, detailed observations of microstructure evolution, property measurements and analyses, comprehensive understanding was made in the carbide formation process. It was found that creep properties depend on the distribution of carbide particles, which is controlled not only by the aging process but also the amount ratio fo Al and carbon. From the results and analysis, new creep-resistant alloy compositions are suggested for further development.

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.

Adsorption of oxygen on low-index surfaces of the TiAl{sub 3} alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latyshev, A. M.; Bakulin, A. V.; Kulkova, S. E., E-mail: kulkova@ms.tsc.ru

Method of the projector augmented waves in the plane-wave basis within the generalized-gradient approximation for the exchange-correlation functional has been used to study oxygen adsorption on (001), (100), and (110) low-index surfaces of the TiAl{sub 3} alloy. It has been established that the sites that are most energetically preferred for the adsorption of oxygen are hollow (H) positions on the (001) surface and bridge (B) positions on the (110) and (100) surfaces. Structural and electronic factors that define their energy preference have been discussed. Changes in the atomic and electronic structure of subsurface layers that occur as the oxygen concentrationmore » increases to three monolayers have been analyzed. It has been shown that the formation of chemical bonds of oxygen with both components of the alloy leads to the appearance of states that are split-off from the bottoms of their valence bands, which is accompanied by the formation of a forbidden gap at the Fermi level and by a weakening of the Ti–Al metallic bonds in the alloy. On the Al-terminated (001) and (110) surfaces, the oxidation of aluminum dominates over that of titanium. On the whole, the binding energy of oxygen on the low-index surfaces with a mixed termination is higher than that at the aluminum-terminated surface. The calculation of the diffusion of oxygen in the TiAl{sub 3} alloy has shown that the lowest barriers correspond to the diffusion between tetrahedral positions in the (001) plane; the diffusion of oxygen in the [001] direction occurs through octahedral and tetrahedral positions. An increase in the concentration of aluminum in the alloy favors a reduction in the height of the energy barriers as compared to the corresponding barriers in the γ-TiAl alloy.« less

A Performance Comparison Study of Uncoated and TiAlN Coated Carbide End Mill on Machining of the Al-35Zn Alloy

NASA Astrophysics Data System (ADS)

Bayraktar, S.; Hekimoglu, A. P.; Turgut, Y.; Haciosmanoglu, M.

2018-01-01

In this study, Al-35Zn alloy was produced by permanent mold casting. To investigate the cutting performance of uncoated and TiAlN coated carbide end mills on this alloy, a series of tests were carried out in the CNC vertical machining center at a constant cutting speed, feed rate and depth of cut. The results obtained from the tests showed that uncoated carbide end mill have lower cutting force and surface roughness than TiAlN coated carbide end mill. These observations are discussed in terms of the alloys properties, cutting tool surfaces, and friction and wear behavior between the cutting tool and the material.

Microstructural Influence on Mechanical Properties in Plasma Microwelding of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Baruah, M.; Bag, S.

2016-11-01

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.

B2 Grain Growth Behavior of a Ti-22Al-25Nb Alloy Fabricated by Hot Pressing Sintering

NASA Astrophysics Data System (ADS)

Jia, Jianbo; Liu, Wenchao; Xu, Yan; Chen, Chen; Yang, Yue; Luo, Junting; Zhang, Kaifeng

2018-05-01

Grain growth behavior of a powder metallurgy (P/M) Ti-22Al-25Nb alloy was investigated by applying a series of isothermal treatment tests over a wide range of temperatures and holding times. An isothermal treatment scheme was conducted in the B2 phase region (1070-1110 °C) and α 2 + B2 phase region (1010-1050 °C) at holding times of 10, 30 min, 1, 2, and 3 h, respectively. The effects of temperature and holding time on the microstructure evolution and microhardness of the P/M Ti-22Al-25Nb alloy at elevated temperatures were evaluated using optical microscope, scanning electron microscope, x-ray diffraction, and Vickers hardness test techniques. The results revealed that the alloy's treated microstructure was closely linked to temperature and holding time, respectively. The change law of B2 grain growth with holding time and temperature can be well interpreted by the Beck equation and Hillert equation, respectively. The B2 grain growth exponent n and activation energy Q were acquired based on experimental data in the α 2 + B2 and B2 phase regions. In addition, the grain growth contour map for the P/M Ti-22Al-25Nb alloy was constructed to depict variations in B2 grain size based on holding time and temperature.

On the preparation of TiAl alloy by direct reduction of the oxide mixtures in calcium chloride melt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhat K. Tripathy; Derek J. Fray

2011-11-01

In recent years, TiAl-based intermetallic alloys are being increasingly considered for application in areas such as (i) automobile/transport sector (passenger cars, trucks and ships) (ii) aerospace industry (jet engines and High Speed Civil Transport propulsion system) and (iii) industrial gas turbines. These materials offer excellent (i) high temperature properties (at higher than 6000C) (ii) mechanical strength and (iii) resistance to corrosion and as a result have raised renewed interest. The combination of these properties make them possible replacement materials for traditional nickel-based super-alloys, which are nearly as twice as dense (than TiAl based alloys). Since the microstructures of these intermetallicmore » alloys affect, to a significant extent, their ultimate performance, further improvements (by way of alteration/modification of these microstructures), have been the subject matter of intense research investigations. It has now been established that the presence of alloy additives, such as niobium, tantalum, manganese, boron, chromium, silicon, nickel and yttrium etc, in specific quantities, impart marked improvement to the properties, viz. fatigue strength, fracture toughness, oxidation resistance and room temperature ductility, of these alloys. From a number of possible alloy compositions, {gamma}-TiAl and Ti-Al-Nb-Cr have, of late, emerged as two promising engineering alloys/materials. . The conventional fabrication process of these alloys include steps such as melting, forging and heat treatment/annealing of the alloy compositions. However, an electrochemical process offers an attractive proposition to prepare these alloys, directly from the mixture of the respective oxides, in just one step. The experimental approach, in this new process, was, therefore, to try to electrochemically reduce the (mixed) oxide pellet to an alloy phase. The removal of oxygen, from the (mixed) oxide pellet, was effected by polarizing the oxide pellet against a

Effect of Grain Refinement and Cooling Rate on the Microstructure and Mechanical Properties of Secondary Al-Si-Cu Alloys

NASA Astrophysics Data System (ADS)

Timelli, Giulio; Camicia, Giordano; Ferraro, Stefano

2014-02-01

The effect of AlTi5B1 grain refinement and different solidification rates on metallurgical and mechanical properties of a secondary AlSi7Cu3Mg alloy is reported. While the Ti content ranges from 0.04 up to 0.225 wt.%, the cooling rate varies between 0.1 and 5.5 °C/s. Metallographic and thermal analysis techniques have been used to quantitatively examine the macro- and microstructural changes occurring with grain refiner addition at various cooling rates. The results indicate that a small AlTi5B1 addition produces the greatest refinement, while no significant reduction of grain size is obtained with a great amount of grain refiner. On increasing the cooling rate, a lower amount of AlTi5B1 master alloy is necessary to produce a uniform grain size throughout the casting. The combined addition of AlTi5B1 and Sr does not produce any reciprocal interaction or effect on primary α-Al and eutectic solidification. The grain refinement improves the plastic behavior of the alloy and increases the reliability of castings, as evidenced by the Weibull statistics.

Superelasticity, corrosion resistance and biocompatibility of the Ti-19Zr-10Nb-1Fe alloy.

PubMed

Xue, Pengfei; Li, Yan; Li, Kangming; Zhang, Deyuan; Zhou, Chungen

2015-05-01

Microstructure, mechanical properties, superelasticity and biocompatibility of a Ti-19Zr-10Nb-1Fe alloy are investigated. X-ray diffraction spectroscopy and transmission electron microscopy observations show that the as-cast Ti-19Zr-10Nb-1Fe alloy is composed of α' and β phases, but only the β phase exists in the as-rolled and as-quenched alloys. The tensile stress-strain tests indicate that the as-quenched alloy exhibits a good combination of mechanical properties with a large elongation of 25%, a low Young's modulus of 59 GPa and a high ultimate tensile stress of 723 MPa. Superelastic recovery behavior is found in the as-quenched alloy during tensile tests, and the corresponding maximum of superelastic strain is 4.7% at the pre-strain of 6%. A superelastic recovery of 4% with high stability is achieved after 10 cyclic loading-unloading training processes. Potentiodynamic polarization and ion release measurements indicate that the as-quenched alloy shows a lower corrosion rate in Hank's solution and a much less ion release rate in 0.9% NaCl solution than those of the NiTi alloys. Cell culture results indicate that the osteoblasts' adhesion and proliferation are similar on both the Ti-19Zr-10Nb-1Fe and NiTi alloys. A better hemocompatibility is confirmed for the as-quenched Ti-19Zr-10Nb-1Fe alloy, attributed to more stable platelet adhesion and small activation degree, and a much lower hemolysis rate compared with the NiTi alloy. Copyright © 2015 Elsevier B.V. All rights reserved.

AlGaN/GaN High Electron Mobility Transistor Grown and Fabricated on ZrTi Metallic Alloy Buffer Layers

DOE PAGES

Ren, Fan; Pearton, Stephen J.; Ahn, Shihyun; ...

2017-09-26

AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated for structures grown on ZrTi metallic alloy buffer layers, which provided lattice matching of the in-plane lattice parameter (“a-parameter”) to hexagonal GaN. The quality of the GaN buffer layer and HEMT structure were confirmed with X-ray 2θ and rocking scans as well as cross-section transmission electron microscopy (TEM) images. The X-ray 2θ scans showed full widths at half maximum (FWHM) of 0.06°, 0.05° and 0.08° for ZrTi alloy, GaN buffer layer, and the entire HEMT structure, respectively. TEM of the lower section of the HEMT structure containing the GaN buffer layer andmore » the AlN/ZrTi/AlN stack on the Si substrate showed that it was important to grow AlN on the top of ZrTi prior to growing the GaN buffer layer. Finally, the estimated threading dislocation (TD) density in the GaN channel layer of the HEMT structure was in the 10 8 cm -2 range.« less

Reaction process of {alpha} {yields} {gamma} massive transformation in Ti-rich TiAl alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumagai, T.; Abe, E.; Nakamura, M.

1995-08-01

Reaction sequence of the massive transformation from the high-temperature {alpha}-Ti phase to the {gamma}-TiAl phase ({gamma}{sub m}) in a Ti-48at.% Al alloy has been examined in terms of optical and transmission electron microscopes. Both transformed and untransformed regions were macroscopically observed in the sample quenched from the high-temperature {alpha} phase field, when the sample was held there for a extended period of time prior to quenching. The transformed region consists of randomly oriented fine {gamma} single phase grains, in which many thermal anti-phase domains (TAPDs), together with a number of stacking faults were observed. In contrast, the untransformed region comprisesmore » extremely fine lamellae of the {gamma} and {alpha}{sub 2}-Ti{sub 3}Al phases, and the {gamma} plates were found to run through the TAPDs caused by {alpha} {yields} {alpha}{sub 2} ordering. Subsequent aging at 1,273 K causes the microstructure change in the untransformed region from {alpha}{sub 2}/{gamma} lamellae to {gamma}/{gamma} lamellae spontaneously and expands the {gamma}{sub m} region. These observations suggest that the {alpha} {yields} {gamma}{sub m} transformation proceeds through formation of fine {gamma} plates.« less

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.

Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO₂ Nanotubes Using a Super-Oxidative Solution.

PubMed

Beltrán-Partida, Ernesto; Moreno-Ulloa, Aldo; Valdez-Salas, Benjamín; Velasquillo, Cristina; Carrillo, Monica; Escamilla, Alan; Valdez, Ernesto; Villarreal, Francisco

2015-03-02

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO₂ nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials.

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; ...

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 brieflymore » discuss the application of our approach to general multicomponent/multiphase alloy systems.« less

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.

Investigations into Ti-(Nb,Ta)-Fe alloys for biomedical applications.

PubMed

Biesiekierski, Arne; Lin, Jixing; Li, Yuncang; Ping, Dehai; Yamabe-Mitarai, Yoko; Wen, Cuie

2016-03-01

In this study, a Ti-(Ta,Nb)-Fe system was investigated with aims toward the development of high strength, biocompatible titanium alloy suitable for the development of porous orthopedic biomaterials with minimal processing. Notable findings include yield strengths of 740, 1250 and 1360 MPa for the Ti-12Nb-5Fe, Ti-7Ta-5Fe and Ti-10Ta-4Fe alloys, respectively, with elastic moduli comparable to existing Ti-alloys, yielding admissible strains of 0.9 ± 0.3, 1.2 ± 0.2 and 1.13 ± 0.02% for the Ti-12Nb-5Fe, Ti-7Ta-5Fe and Ti-10Ta-4Fe alloys, respectively; more than twice that of human bone. Observed microstructure varied significantly depending on alloy; near pure β-phase was seen in Ti-12Nb-5Fe, β with some ω precipitation in Ti-10Ta-4Fe, and a duplex α+β structure was observed throughout the Ti-7Ta-5Fe. In addition to suitable mechanical parameters, all investigated alloys exhibited promising corrosion potentials on the order of -0.24 V SCE, equalling that seen for a C.P.-Ti control at -0.25V SCE, and substantially more noble than that seen for Ti-6Al-4V. Electrochemical corrosion rates of 0.5-3 μm/year were likewise seen to agree well with that measured for C.P.-Ti. Further, no statistically significant difference could be seen between any of the alloys relative to a C.P.-Ti control regards to cell proliferation, as investigated via MTS assay and confocal microscopy. As such, the combination of high admissible strain and low corrosion indicate all investigated alloys show significant promise as potential porous biomaterials while in the as-cast state, with the Ti-10Ta-4Fe alloy identified as the most promising composition investigated. The findings of this paper are of significance to the field of metallic biomaterials as they detail the development of alloys of satisfactory biocompatibility and electrochemical behaviour, that furthermore display exceptional mechanical properties. Notably, both extremely high compressive yield strengths and admissible strains

Grain Refinement and Texture Mitigation in Low Boron Containing TiAl-Alloys

NASA Astrophysics Data System (ADS)

Hecht, Ulrike; Witusiewicz, Victor T.

2017-12-01

Controlling the grain size and texture of lamellar TiAl-alloys is essential for well-balanced creep and fatigue properties. Excellent refinement and texture mitigation are achieved in aluminum lean alloys by low boron additions of 0.2 at.%. This amount is sufficient to promote in situ formation of ultrafine borides during the last stages of body centered cubic (BCC) solidification. The borides subsequently serve as nucleation sites for hexagonal close packed (HCP) during the BCC-HCP phase transformation. Bridgman solidification experiments with alloy Ti-43Al-8Nb-0.2C-0.2B were performed under a different growth velocity, i.e., cooling rate, to evaluate the HCP grain size distribution and texture. For slow-to-moderate cooling rates, about 65% of HCP grains are randomly oriented, despite the pronounced texture of the parent BCC phase resulting from directional solidification. For high cooling rates, obtained by quenching, texture mitigation is less pronounced. Only 28% of the HCP grains are randomly oriented, the majority being crystallographic variants of the Burgers orientation relationship.

Effects of ultrasonic vibration on the microstructure and mechanical properties of high alloying TiAl

PubMed Central

Ruirun, Chen; Deshuang, Zheng; Tengfei, Ma; Hongsheng, Ding; Yanqing, Su; Jingjie, Guo; Hengzhi, Fu

2017-01-01

To modify the microstructure and enhance performances, the ultrasonic vibration is applied in the mould casting of TiAl alloy. The effects and mechanism of ultrasonic vibration on the solidifying microstructure and mechanical properties are investigated and the model for predicting lamellar colony size is established. After ultrasonic vibration, the coarse microstructure is well modified and lamellar colony is refined from 534 μm to 56 μm. Most of precipitated phases are dissolved into the lamellar colony leading to a homogenous element distribution. The phase ratio of α2-Ti3Al and γ-TiAl is increased, and the chemical composition is promoted to more close to equilibrium level by weakening the influence of β-alloying elements. The microhardness and yield strength are gradually improved by 23.72% and 181.88% due to the fine grain strengthening, while the compressive strength is enhanced by 24.47% through solution strengthening. The critical ultrasonic intensity (Ib) for TiAl alloy is estimated at 220 W cm−2 and the model for average lamellar colony size is established as . The ultrasonic refinement efficiency exponentially increases as the ultrasonic vibration time with a theoretic limit maximum value of Elim = 88% and the dominating refinement mechanism by ultrasonic vibration is the cavitation-enhanced nucleation rather than cavitation-induced dendrite fragmentation. PMID:28117451

Microstructure and Mechanical Behavior of Microwave Sintered Cu50Ti50 Amorphous Alloy Reinforced Al Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Reddy, M. Penchal; Ubaid, F.; Shakoor, R. A.; Mohamed, A. M. A.

2018-06-01

In the present work, Al metal matrix composites reinforced with Cu-based (Cu50Ti50) amorphous alloy particles synthesized by ball milling followed by a microwave sintering process were studied. The amorphous powders of Cu50Ti50 produced by ball milling were used to reinforce the aluminum matrix. They were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness and compression testing. The analysis of XRD patterns of the samples containing 5 vol.%, 10 vol.% and 15 vol.% Cu50Ti50 indicates the presence of Al and Cu50Ti50 peaks. SEM images of the sintered composites show the uniform distribution of reinforced particles within the matrix. Mechanical properties of the composites were found to increase with an increasing volume fraction of Cu50Ti50 reinforcement particles. The hardness and compressive strength were enhanced to 89 Hv and 449 MPa, respectively, for the Al-15 vol.% Cu50Ti50 composites.

Functionalization of Biomedical Ti6Al4V via In Situ Alloying by Cu during Laser Powder Bed Fusion Manufacturing.

PubMed

Krakhmalev, Pavel; Yadroitsev, Igor; Yadroitsava, Ina; de Smidt, Olga

2017-10-03

The modern medical industry successfully utilizes Laser Powder Bed Fusion (LPBF) to manufacture complex custom implants. Ti6Al4V is one of the most commonly used biocompatible alloys. In surgery practice, infection at the bone-implant interface is one of the key reasons for implant failure. Therefore, advanced implants with biocompatibility and antibacterial properties are required. Modification of Ti alloy with Cu, which in small concentrations is a proven non-toxic antibacterial agent, is an attractive way to manufacture implants with embedded antibacterial functionality. The possibility of achieving alloying in situ, during manufacturing, is a unique option of the LPBF technology. It provides unique opportunities to manufacture customized implant shapes and design new alloys. Nevertheless, optimal process parameters need to be established for the in situ alloyed materials to form dense parts with required mechanical properties. This research is dedicated to an investigation of Ti6Al4V (ELI)-1 at % Cu material, manufactured by LPBF from a mixture of Ti6Al4V (ELI) and pure Cu powders. The effect of process parameters on surface roughness, chemical composition and distribution of Cu was investigated. Chemical homogeneity was discussed in relation to differences in the viscosity and density of molten Cu and Ti6Al4V. Microstructure, mechanical properties, and fracture behavior of as-built 3D samples were analyzed and discussed. Pilot antibacterial functionalization testing of Ti6Al4V (ELI) in situ alloyed with 1 at % Cu showed promising results and notable reduction in the growth of pure cultures of Escherichia coli and Staphylococcus aureus.

Effect of commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy.

PubMed

Alves Rezende, Maria Cristina Rosifini; Alves, Ana Paula Rosifini; Codaro, Eduardo Norberto; Dutra, Conceição Aparecida Matsumoto

2007-01-01

The purpose of this work was to evaluate the effect of three commercial mouthwashes on the corrosion resistance of Ti-10Mo experimental alloy. Experiments were made at 37.0 +/- 0.5 degrees C in a conventional three-compartment double wall glass cell containing commercial mouthwashes. Three mouthwashes with different active ingredients were tested: (I) 0.05% sodium fluoride + 0.03% triclosan; (II) 0.5 g/l cetylpyridinium chloride + 0.05% sodium fluoride; (III) 0.12% chlorohexidine digluconate. The assessment of the individual effect of active ingredients was studied by using 0.05% sodium fluoride. Commercially pure titanium (CP Ti) was used as control. Microstructures from Ti-10Mo experimental alloy and CP Ti were also evaluated using optical microscopy. Ti-10Mo as-cast alloy shows the typical rapidly cooled dendrites microstructure (beta phase) while CP Ti has exhibited a metastable martensitic microstructure. Electrochemical behavior of dental materials here studied was more affected by mouthwash type than by Ti alloy composition or microstructure. In both alloys passivation phenomenon was observed. This process may be mainly related to Ti oxides or other Ti species present in spontaneously formed film. Small differences in passive current densities values may be connected with changes in film porosity and thickness. Protective characteristics of this passive film are lower in 0.05% sodium fluoride + 0.03% triclosan mouthwash than in the other two mouthwashes tested.

Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO2 Nanotubes Using a Super-Oxidative Solution

PubMed Central

Beltrán-Partida, Ernesto; Moreno-Ulloa, Aldo; Valdez-Salas, Benjamín; Velasquillo, Cristina; Carrillo, Monica; Escamilla, Alan; Valdez, Ernesto; Villarreal, Francisco

2015-01-01

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials. PMID:28787976

Electrochemical corrosion, wear and cell behavior of ZrO2/TiO2 alloyed layer on Ti-6Al-4V.

PubMed

Li, Jianfang; He, Xiaojing; Zhang, Guannan; Hang, Ruiqiang; Huang, Xiaobo; Tang, Bin; Zhang, Xiangyu

2018-06-01

Ti-6Al-4V (TC4) has received increasing attention as biomaterial but also raised concerns about the long-term safety of releasing of metal ions and poor wear resistance. In this work, an ZrO 2 /TiO 2 alloyed layer was prepared on TC4 by plasma surface alloying with Zr and subsequently annealed in the air for improved corrosion and wear resistant. To assess the corrosion performance of the alloyed layer, the specimens were measured by open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid solution. The result shows that the ZrO 2 /TiO 2 alloyed layer exhibits strikingly high polarization resistance, wide passive region and very low current density, indicating the excellent corrosion resistance. The layer also displays significant improvement of wear resistance. Furthermore, the alloyed layer restricts cell adhesion and spreading. We infer that the ZrO 2 /TiO 2 alloyed layer might be potentially useful implanted devices such as biosensors, bioelectronics or drug delivery devices. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of TiC addition on fracture toughness of Al6061 alloy

NASA Astrophysics Data System (ADS)

Raviraj, M. S.; Sharanprabhu, C. M.; Mohankumar, G. C.

2018-04-01

Al 6061 matrix was reinforced with different proportions of TiC particles such as 3wt%, 5wt% and 7wt% and the effect on fracture toughness was studied. Al-TiC metal matrix composites were produced by stir casting method to ensure uniform distribution of the TiC particulates in the Al matrix. LEFM (Linear Elastic Fracture Mechanics) has been used to characterize the fracture toughness using various specimen geometries. The compact tension (CT) specimens with straight through notch were machined as per ASTM E399 specifications. All the specimens were machined to have constant a/W=0.5 and B/W was varied from 0.2 to 0.7. A sharp crack initiation was done at the end of notch by fatigue loading using servo-hydraulic controlled testing machine. Load v/s crack mouth opening displacement (CMOD) data was plotted and stress intensity factor, KQ determined. Critical stress intensity factor KIC was obtained by plotting KQ v/s thickness of specimen data. The fracture toughness of the composites varied between 16-19 MPa√m as compared to 23MPa√m for base alloy Al6061. Composites with 3wt% and 7wt% TiC showed better fracture toughness than 5wt% TiC reinforced Al metal matrix composites.

Effect of microstructure on the mechanical properties of as-cast Ti-Nb-Al-Cu-Ni alloys for biomedical application.

PubMed

Okulov, I V; Pauly, S; Kühn, U; Gargarella, P; Marr, T; Freudenberger, J; Schultz, L; Scharnweber, J; Oertel, C-G; Skrotzki, W; Eckert, J

2013-12-01

The correlation between the microstructure and mechanical behavior during tensile loading of Ti68.8Nb13.6Al6.5Cu6Ni5.1 and Ti71.8Nb14.1Al6.7Cu4Ni3.4 alloys was investigated. The present alloys were prepared by the non-equilibrium processing applying relatively high cooling rates. The microstructure consists of a dendritic bcc β-Ti solid solution and fine intermetallic precipitates in the interdendritic region. The volume fraction of the intermetallic phases decreases significantly with slightly decreasing the Cu and Ni content. Consequently, the fracture mechanism in tension changes from cleavage to shear. This in turn strongly enhances the ductility of the alloy and as a result Ti71.8Nb14.1Al6.7Cu4Ni3.4 demonstrates a significant tensile ductility of about 14% combined with the high yield strength of above 820 MPa already in the as-cast state. The results demonstrate that the control of precipitates can significantly enhance the ductility and yet maintaining the high strength and the low Young's modulus of these alloys. The achieved high bio performance (ratio of strength to Young's modulus) is comparable (or even superior) with that of the recently developed Ti-based biomedical alloys. © 2013.

Surface Properties of the IN SITU Formed Ceramics Reinforced Composite Coatings on TI-3AL-2V Alloys

NASA Astrophysics Data System (ADS)

Liu, Peng; Guo, Wei; Hu, Dakui; Luo, Hui; Zhang, Yuanbin

2012-04-01

The synthesis of hard composite coating on titanium alloy by laser cladding of Al/Fe/Ni+C/Si3N4 pre-placed powders has been investigated in detail. SEM result indicated that a composite coating with metallurgical joint to the substrate was formed. XRD result indicated that the composite coating mainly consisted of γ-(Fe, Ni), FeAl, Ti3Al, TiC, TiNi, TiC0.3N0.7, Ti2N, SiC, Ti5Si3 and TiNi. Compared with Ti-3Al-2V substrate, an improvement of the micro-hardness and the wear resistance was observed for this composite coating.

Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications

NASA Astrophysics Data System (ADS)

Yadroitsev, I.; Krakhmalev, P.; Yadroitsava, I.; Du Plessis, A.

2018-03-01

Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performed based on x-ray micro-computed tomography, scanning electron microscopy, and x-ray diffraction methods. The types of fracture and the tensile fracture mechanisms of the LPBF Ti6Al4V ELI alloy were also studied. Detailed analysis of the microstructure and the corresponding mechanical properties were compared against standard specifications for conventional Ti6Al4V alloy for use in surgical implant applications. Conclusions regarding the mechanical properties and heat treatment of LPBF Ti6Al4V ELI for biomedical applications are made.

Functionalization of Biomedical Ti6Al4V via In Situ Alloying by Cu during Laser Powder Bed Fusion Manufacturing

PubMed Central

Krakhmalev, Pavel; Yadroitsev, Igor; Yadroitsava, Ina; de Smidt, Olga

2017-01-01

The modern medical industry successfully utilizes Laser Powder Bed Fusion (LPBF) to manufacture complex custom implants. Ti6Al4V is one of the most commonly used biocompatible alloys. In surgery practice, infection at the bone–implant interface is one of the key reasons for implant failure. Therefore, advanced implants with biocompatibility and antibacterial properties are required. Modification of Ti alloy with Cu, which in small concentrations is a proven non-toxic antibacterial agent, is an attractive way to manufacture implants with embedded antibacterial functionality. The possibility of achieving alloying in situ, during manufacturing, is a unique option of the LPBF technology. It provides unique opportunities to manufacture customized implant shapes and design new alloys. Nevertheless, optimal process parameters need to be established for the in situ alloyed materials to form dense parts with required mechanical properties. This research is dedicated to an investigation of Ti6Al4V (ELI)-1 at % Cu material, manufactured by LPBF from a mixture of Ti6Al4V (ELI) and pure Cu powders. The effect of process parameters on surface roughness, chemical composition and distribution of Cu was investigated. Chemical homogeneity was discussed in relation to differences in the viscosity and density of molten Cu and Ti6Al4V. Microstructure, mechanical properties, and fracture behavior of as-built 3D samples were analyzed and discussed. Pilot antibacterial functionalization testing of Ti6Al4V (ELI) in situ alloyed with 1 at % Cu showed promising results and notable reduction in the growth of pure cultures of Escherichia coli and Staphylococcus aureus. PMID:28972546

Corrosion resistance tests on NiTi shape memory alloy.

PubMed

Rondelli, G

1996-10-01

The corrosion performances of NiTi shape memory alloys (SMA) in human body simulating fluids were evaluated in comparison with other implant materials. As for the passivity current in potentiostatic conditions, taken as an index of ion release, the values are about three times higher for NiTi than for Ti6Al4V and austenitic stainless steels. Regarding the localized corrosion, while plain potentiodynamic scans indicated for NiTi alloy good resistance to pitting attack similar to Ti6Al4V, tests in which the passive film is abruptly damaged (i.e. potentiostatic scratch test and modified ASTM F746) pointed out that the characteristics of the passive film formed on NiTi alloy (whose strength can be related to the alloy's biocompatibility) are not as good as those on Ti6Al4V but are comparable or inferior to those on austenitic stainless steels.

Microstructure and Tribological Properties of AlCoCrFeNiTi0.5 High-Entropy Alloy in Hydrogen Peroxide Solution

NASA Astrophysics Data System (ADS)

Yu, Y.; Liu, W. M.; Zhang, T. B.; Li, J. S.; Wang, J.; Kou, H. C.; Li, J.

2014-01-01

Microstructure and tribological properties of an AlCoCrFeNiTi0.5 high-entropy alloy in high-concentration hydrogen peroxide solution were investigated in this work. The results show that the sigma phase precipitates and the content of bcc2 decrease during the annealing process. Meanwhile, the complex construction of the interdendrite region changes into simple isolated-island shape, and much more spherical precipitates are formed. Those changes of microstructure during the annealing process lead to the increase of hardness of this alloy. In the testing conditions, the AlCoCrFeNiTi0.5 alloy shows smoother worn surfaces and steadier coefficient of friction curves than does the 1Cr18Ni9Ti stainless steel, and SiC ceramic preserves better wear resistance than ZrO2 ceramic. After annealing, the wear resistance of the AlCoCrFeNiTi0.5 alloy increases coupled with SiC counterface but decreases with ZrO2 counterface.

Improving High-Temperature Tensile and Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloys Through Micro-additions of Ti, V, and Zr

NASA Astrophysics Data System (ADS)

Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

2015-07-01

High-temperature tensile and low-cycle fatigue tests were performed to assess the influence of micro-additions of Ti, V, and Zr on the improvement of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in the as-cast condition. Addition of transition metals led to modification of microstructure where in addition to conventional phases present in the Al-7Si-1Cu-0.5Mg base, new thermally stable micro-sized Zr-Ti-V-rich phases Al21.4Si4.1Ti3.5VZr3.9, Al6.7Si1.2TiZr1.8, Al2.8Si3.8V1.6Zr, and Al5.1Si35.4Ti1.6Zr5.7Fe were formed. The tensile tests showed that with increasing test temperature from 298 K to 673 K (25 °C to 400 °C), the yield stress and tensile strength of the present studied alloy decreased from 161 to 84 MPa and from 261 to 102 MPa, respectively. Also, the studied alloy exhibited 18, 12, and 5 pct higher tensile strength than the alloy A356, 354 and existing Al-Si-Cu-Mg alloy modified with additions of Zr, Ti, and Ni, respectively. The fatigue life of the studied alloy was substantially longer than those of the reference alloys A356 and the same Al-7Si-1Cu-0.5Mg base with minor additions of V, Zr, and Ti in the T6 condition. Fractographic analysis after tensile tests revealed that at the lower temperature up to 473 K (200 °C), the cleavage-type brittle fracture for the precipitates and ductile fracture for the matrix were dominant while at higher temperature fully ductile-type fracture with debonding and pull-out of cracked particles was identified. It is believed that the intermetallic precipitates containing Zr, Ti, and V improve the alloy performance at increased temperatures.

Cleaner Production of Ti Powder by a Two-Stage Aluminothermic Reduction Process

NASA Astrophysics Data System (ADS)

Zhao, Kun; Wang, Yaowu; Feng, Naixiang

2017-10-01

A two-stage aluminothermic reduction process for preparing Ti powder under vacuum conditions using Na2TiF6 was investigated. An Al-Ti master alloy and a clean cryolite were simultaneously obtained as co-products. The first-stage reduction was an exothermic process that occurred at approximately 660°C. The Al and O contents of the Ti powder product were 0.18 wt.% and 0.35 wt.%, respectively, with an average particle size <74 μm. Ti(IV), Ti(III), and metallic Ti were present in the Ti-containing cryolite produced by the first-stage reduction, at a total content of approximately 3.13 wt.%. After second-stage reduction, the Ti elemental contents of the clean cryolite were reduced to 0.002 wt.%. The Al-Ti master alloy obtained by second-stage reduction was composed of Al and TiAl3. The mechanisms involved in these reduction processes were also examined.

Dynamic Recrystallization of the Constituent γ Phase and Mechanical Properties of Ti-43Al-9V-0.2Y Alloy Sheet

PubMed Central

Zhang, Yu; Wang, Xiaopeng; Kong, Fantao

2017-01-01

A crack-free Ti-43Al-9V-0.2Y alloy sheet was successfully fabricated via hot-pack rolling at 1200 °C. After hot-rolling, the β/γ lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average γ grain size of 10.5 μm. The dynamic recrystallization (DRX) of the γ phase was systematically investigated. A recrystallization fraction of 62.5% was obtained for the γ phase in the TiAl alloy sheet, when a threshold value of 0.8° was applied to the distribution of grain orientation spread (GOS) values. The high strain rate and high stress associated with hot-rolling are conducive for discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), respectively. A certain high-angle boundary (HAGB: θ = 89° ± 3°<100>), which is associated with DDRX, occurs in both the recrystallized and deformed γ grains. The twin boundaries play an important role in the DDRX of the γ phase. Additionally, the sub-structures and sub-boundaries originating from low-angle boundaries in the deformed grains also indicate that CDRX occurs. The mechanical properties of the alloy sheet were determined at both room and elevated temperatures. At 750 °C, the alloy sheet exhibited excellent elongation (53%), corresponding to a failure strength of 467 MPa. PMID:28914797

Dynamic Recrystallization of the Constituent γ Phase and Mechanical Properties of Ti-43Al-9V-0.2Y Alloy Sheet.

PubMed

Zhang, Yu; Wang, Xiaopeng; Kong, Fantao; Chen, Yuyong

2017-09-15

A crack-free Ti-43Al-9V-0.2Y alloy sheet was successfully fabricated via hot-pack rolling at 1200 °C. After hot-rolling, the β/γ lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average γ grain size of 10.5 μm. The dynamic recrystallization (DRX) of the γ phase was systematically investigated. A recrystallization fraction of 62.5% was obtained for the γ phase in the TiAl alloy sheet, when a threshold value of 0.8° was applied to the distribution of grain orientation spread (GOS) values. The high strain rate and high stress associated with hot-rolling are conducive for discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), respectively. A certain high-angle boundary (HAGB: θ = 89° ± 3°<100>), which is associated with DDRX, occurs in both the recrystallized and deformed γ grains. The twin boundaries play an important role in the DDRX of the γ phase. Additionally, the sub-structures and sub-boundaries originating from low-angle boundaries in the deformed grains also indicate that CDRX occurs. The mechanical properties of the alloy sheet were determined at both room and elevated temperatures. At 750 °C, the alloy sheet exhibited excellent elongation (53%), corresponding to a failure strength of 467 MPa.

Al-TiC in situ composite coating fabricated by low power pulsed laser cladding on AZ91D magnesium alloy

NASA Astrophysics Data System (ADS)

Yang, Liuqing; Li, Zhiyong; Zhang, Yingqiao; Wei, Shouzheng; Liu, Fuqiang

2018-03-01

Al + (Ti + B4C) composite coating was cladded on AZ91D magnesium alloy by a low power pulsed Nd-YAG laser. The Ti+B4C mixed powder is with the ratio of Ti: B4C = 5:1, which was then mixed with Al powder by weight fraction of 10%, 15% and 20%, respectively. Scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction were used to study the microstructure, chemical composition and phase composition of the coating. Results showed that the coating had satisfied metallurgical bonding with the magnesium substrate. Al3Mg2, Al12Mg17, Al3Ti and TiC were formed by in-situ reaction. The coatings have micro-hardness of 348HV, which is about 5-6 times higher than that of AZ91D. The wear resistance and corrosion resistance of the coatings are enhanced with the addition of the mixed powder.

Study of Tool Wear Mechanisms and Mathematical Modeling of Flank Wear During Machining of Ti Alloy (Ti6Al4V)

NASA Astrophysics Data System (ADS)

Chetan; Narasimhulu, A.; Ghosh, S.; Rao, P. V.

2015-07-01

Machinability of titanium is poor due to its low thermal conductivity and high chemical affinity. Lower thermal conductivity of titanium alloy is undesirable on the part of cutting tool causing extensive tool wear. The main task of this work is to predict the various wear mechanisms involved during machining of Ti alloy (Ti6Al4V) and to formulate an analytical mathematical tool wear model for the same. It has been found from various experiments that adhesive and diffusion wear are the dominating wear during machining of Ti alloy with PVD coated tungsten carbide tool. It is also clear from the experiments that the tool wear increases with the increase in cutting parameters like speed, feed and depth of cut. The wear model was validated by carrying out dry machining of Ti alloy at suitable cutting conditions. It has been found that the wear model is able to predict the flank wear suitably under gentle cutting conditions.

Surface characterization of implant materials c.p. Ti, Ti-6Al-7Nb and Ti-6Al-4V with different pretreatments.

PubMed

Sittig, C; Textor, M; Spencer, N D; Wieland, M; Vallotton, P H

1999-01-01

The biocompatibility of commercially pure titanium and its alloys is closely related to their surface properties, with both the composition of the protecting oxide film and the surface topography playing an important role. Surfaces of commercially pure titanium and of the two alloys Ti-6Al-7Nb and Ti-6Al-4V (wt %) have been investigated following three different pretreatments: polishing, nitric acid passivation and pickling in nitric acid-hydrogen fluoride. Nitric acid treatment is found to substantially reduce the concentration of surface contaminants present after polishing. The natural 4-6 nm thick oxide layer on commercially pure titanium is composed of titanium oxide in different oxidation states (TiO2, Ti2O3 and TiO), while for the alloys, aluminium and niobium or vanadium are additionally present in oxidized form (Al2O3, Nb2O5 or V-oxides). The concentrations of the alloying elements at the surface are shown to be strongly dependent on the pretreatment process. While pickling increases the surface roughness of both commercially pure titanium and the alloys, different mechanisms appear to be involved. In the case of commercially pure titanium, the dissolution rate depends on grain orientation, whereas in the case of the two alloys, selective alpha-phase dissolution and enrichment of the beta-phase appears to occur. Copyright 1999 Kluwer Academic Publishers

Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography

PubMed Central

Klein, Thomas; Clemens, Helmut; Mayer, Svea

2016-01-01

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys. PMID:28773880

Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography.

PubMed

Klein, Thomas; Clemens, Helmut; Mayer, Svea

2016-09-06

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys.

Microstructural characterization and mechanical property of active soldering anodized 6061 Al alloy using Sn-3.5Ag-xTi active solders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei-Lin, E-mail: wangwl77@gmail.com; Tsai, Yi-Chia, E-mail: tij@itri.org.tw

2012-06-15

Active solders Sn-3.5Ag-xTi varied from x = 0 to 6 wt.% Ti addition were prepared by vacuum arc re-melting and the resultant phase formation and variation of microstructure with titanium concentration were analyzed using X-ray diffraction, optical microscopy and scanning electron microscopy. The Sn-3.5Ag-xTi active solders are used as metallic filler to join with anodized 6061 Al alloy for potential applications of providing a higher heat conduction path. Their joints and mechanical properties were characterized and evaluated in terms of titanium content. The mechanical property of joints was measured by shear testing. The joint strength was very dependent on themore » titanium content. Solder with a 0.5 wt.% Ti addition can successfully wet and bond to the anodized aluminum oxide layers of Al alloy and posses a shear strength of 16.28 {+-} 0.64 MPa. The maximum bonding strength reached 22.24 {+-} 0.70 MPa at a 3 wt.% Ti addition. Interfacial reaction phase and chemical composition were identified by a transmission electron microscope with energy dispersive spectrometer. Results showed that the Ti element reacts with anodized aluminum oxide to form Al{sub 3}Ti-rich and Al{sub 3}Ti phases at the joint interfaces. - Highlights: Black-Right-Pointing-Pointer Active solder joining of anodized Al alloy needs 0.5 wt.% Ti addition for Sn-3.5Ag. Black-Right-Pointing-Pointer The maximum bonding strength occurs at 3 wt.% Ti addition. Black-Right-Pointing-Pointer The Ti reacts with anodized Al oxide to form Al{sub 3}Ti-rich and Al{sub 3}Ti at joint interface.« less

Compact Process for the Preparation of Microfine Spherical High-Niobium-Containing TiAl Alloy Powders

NASA Astrophysics Data System (ADS)

Tong, J. B.; Lu, X.; Liu, C. C.; Wang, L. N.; Qu, X. H.

2015-03-01

High-Nb-containing TiAl alloys are a new generation of materials for high-temperature structural applications because of their superior high-temperature mechanical properties. The alloy powders can be widely used for additive manufacturing, thermal spraying, and powder metallurgy. Because of the difficulty of making microfine spherical alloy powders in quantity by conventional techniques, a compact method was proposed, which consisted of two-step ball milling of elemental powders and subsequent radio frequency (RF) argon plasma spheroidization. In comparison with conventional mechanical alloying techniques, the two-step milling process can be used to prepare alloy powders with uniform scale in a short milling time with no addition of process control agent. This makes the process effective and less contaminating. After RF argon plasma spheroidization, the powders produced exhibit good sphericity, and the number-average diameter is about 8.2 μm with a symmetric unimodal particle size distribution. The powders perform high composition homogeneity and contain predominately supersaturated α 2-Ti3Al phase. The oxygen and carbon contents of the spheroidized powder are 0.47% and 0.050%, respectively.

Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

1996-01-01

A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

Production and mechanical properties of Ti-5Al-2.5Fe-xCu alloys for biomedical applications.

PubMed

Yamanoglu, Ridvan; Efendi, Erdinc; Kolayli, Fetiye; Uzuner, Huseyin; Daoud, Ismail

2018-01-30

In this study, the mechanical, antibacterial properties and cell toxicity response of Ti-5Al2.5Fe alloy with different copper contents were investigated. The alloys were prepared by high-energy ball milling using elemental Ti, Al, Fe, and Cu powders and consolidated by a uniaxial vacuum hot press. Staphylococcus aureus strain ATCC 29213 and Escherichia coli strain ATCC 25922 were used to determine the antibacterial properties of the sintered alloys. The in vitro cytotoxicity of the samples was evaluated with HeLa (ATTC, CCL-2) cells using thiazolyl blue tetrazolium bromide. The mechanical behavior of the samples was determined as a function of hardness and bending tests and analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, optical microscopy and x-ray diffraction (XRD). The results showed that the Cu content significantly improved the antibacterial properties. Cu addition prevented the formation of E. coli and S. aureus colonies on the surface of the samples. All samples exhibited very good cell biocompatibility. The alloys with different copper contents showed different mechanical properties, and the results were correlated by microstructural and XRD analyses in detail. Our results showed that Cu has a great effect on the Ti5Al2.5Fe alloy and the alloy is suitable for biomedical applications with enhanced antibacterial activity.

Study on the Anti-Poison Performance of Al–Y–P Master Alloy for Impurity Ca in Aluminum Alloys

PubMed Central

Zuo, Min; Dong, Yu; Zhao, Degang; Wang, Yan; Teng, Xinying

2017-01-01

In this article, the anti-poison performance of novel Al–6Y–2P master alloy for impurity Ca in hypereutectic Al–Si alloys was investigated in detail. According to the microstructural analysis, it can be found that the primary Si and eutectic Si particles could be relatively modified and refined. In order to investigate the influence mechanism of Ca on the limited refinement performance of Al–6Y–2P master alloy, types of Al–xSi–2Ca–3Y–1P (x = 0, 6, 12, 18, and 30) alloys were prepared. It is observed that Ca takes the form of more stable Ca3P2 compounds by reacting with YP, and the surface of Ca3P2 particles are unsmooth, and even some have wrinkles in Al Al–2Ca–3Y–1P alloy. With the increase of Si content in Al–xSi–2Ca–3Y–1P (x = 6, 12, 18 and 30) systems, the multi-encapsulation structures, i.e., the phosphide (AlP and YP), hexagonal Al2Si2Ca, the Al3Si2Y2 or primary Si from inside to outside in order were examined.The excapsulation of YP and AlP caused by Al2Si2Ca might be the reason for the limited refinement effect of Al–6Y–2P master alloy for hypereutectic Al–18Si alloys. PMID:29186862

Study on Strengthening and Toughening Mechanisms of Aluminum Alloy 2618-Ti at Elevated Temperature

NASA Astrophysics Data System (ADS)

Kun, Ma; Tingting, Liu; Ya, Liu; Xuping, Su; Jianhua, Wang

2018-01-01

The tensile properties of the alloy 2618 and 2618-Ti were tested using a tensile testing machine. The morphologies of the fracture of tensile samples were observed using scanning electron microscopy. The strengthening and toughening mechanisms of alloy 2618-Ti at elevated temperature were systematically investigated based on the analyses of experimental results. The results showed that the tensile strength of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 250 and 300 °C. But the elongation of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 200 and 300 °C. The equal-strength temperature of intragranular and grain boundary of alloy 2618-Ti is about 235 °C. When the temperature is lower than 235 °C, the strengthening of alloy 2618-Ti is ascribed to the strengthening effect of fine grains and dispersed Al3Ti/Al18Mg3Ti2 phase. When the temperature is higher than 235 °C, the strengthening effect of alloy 2618-Ti is mainly attributed to the load transfer of Al3Ti and Al18Mg3Ti2 particles. The toughening of alloy 2618-Ti at elevated temperature is mainly ascribed to the fine grain microstructure, excellent combination between matrix and dispersed Al3Ti/Al18Mg3Ti2 particles as well as the recrystallization of the alloy at elevated temperature.

Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

DOE PAGES

Zhang, W. Y.; Skomski, R.; Kashyap, A.; ...

2016-02-18

Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti 3(Fe,Co) 5B 2, FeCo-rich bcc, and NiAl-rich L2 1 phases; Ti 3(Fe,Co) 5B 2, is a new substitutional alloy series whose end members Ti 3Co 5B 2 and Ti 3Fe 5B 2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti 11+xFe 37.5-0.5xCo 37.5–0.5xB 14 (x = 0, 4) and alnico-like Ti 11Fe 26Co 26Ni 10Al 11Cu 2B 14, the latter also containingmore » an L2 1-type alloy. The volume fraction of the Ti 3(Fe,Co) 5B 2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystallineanisotropy of the tetragonal Ti 3(Fe,Co) 5B 2 phase. The alloy containing Ni,Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Lastly, our results indicate that magnetocrystallineanisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.« less

An Analysis on the Constitutive Models for Forging of Ti6Al4V Alloy Considering the Softening Behavior

NASA Astrophysics Data System (ADS)

Souza, Paul M.; Beladi, Hossein; Singh, Rajkumar P.; Hodgson, Peter D.; Rolfe, Bernard

2018-05-01

This paper developed high-temperature deformation constitutive models for a Ti6Al4V alloy using an empirical-based Arrhenius equation and an enhanced version of the authors' physical-based EM + Avrami equations. The initial microstructure was a partially equiaxed α + β grain structure. A wide range of experimental data was obtained from hot compression of the Ti6Al4 V alloy at deformation temperatures ranging from 720 to 970 °C, and at strain rates varying from 0.01 to 10 s-1. The friction- and adiabatic-corrected flow curves were used to identify the parameter values of the constitutive models. Both models provided good overall accuracy of the flow stress. The generalized modified Arrhenius model was better at predicting the flow stress at lower strain rates. However, the model was inaccurate in predicting the peak strain. In contrast, the enhanced physical-based EM + Avrami model revealed very good accuracy at intermediate and high strain rates, but it was also better at predicting the peak strain. Blind sample tests revealed that the EM + Avrami maintained good predictions on new (unseen) data. Thus, the enhanced EM + Avrami model may be preferred over the Arrhenius model to predict the flow behavior of Ti6Al4V alloy during industrial forgings, when the initial microstructure is partially equiaxed.

Biocorrosion properties of antibacterial Ti-10Cu sintered alloy in several simulated biological solutions.

PubMed

Liu, Cong; Zhang, Erlin

2015-03-01

Ti-10Cu sintered alloy has shown strong antibacterial properties against S. aureus and E. coli and good cell biocompatibility, which displays potential application in dental application. The corrosion behaviors of the alloy in five different simulated biological solutions have been investigated by electrochemical technology, surface observation, roughness measurement and immersion test. Five different simulated solutions were chosen to simulate oral condition, oral condition with F(-) ion, human body fluids with different pH values and blood system. It has been shown that Ti-10Cu alloy exhibits high corrosion rate in Saliva pH 3.5 solution and Saliva pH 6.8 + 0.2F solution but low corrosion rate in Hank's, Tyrode's and Saliva pH 6.8 solutions. The corrosion rate of Ti-10Cu alloy was in a order of Hank's, Tyrode's, Saliva pH 6.8, Saliva-pH 3.5 and Saliva pH 6.8 + 0.2F from slow to fast. All results indicated acid and F(-) containing conditions prompt the corrosion reaction of Ti-Cu alloy. It was suggested that the Cu ion release in the biological environments, especially in the acid and F(-) containing condition would lead to high antibacterial properties without any cell toxicity, displaying wide potential application of this alloy.

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

Study of Crystallographic Texture During Thermo-Mechanical Processing of Boron Modified Ti-Alloys

DTIC Science & Technology

2009-07-15

project developed a processing strategy for boron-modified titanium alloy Ti- 6Al - 4V , and developed an understanding of the deformation and...develop the processing strategy for boron modified titanium alloy Ti- 6Al - 4V 2. To understand the deformation and transformation mechanisms as a function...strength-to-weight ratio, excellent mechanical properties and corrosion resistance, titanium (Ti) and its alloys, especially (α+β) alloys like Ti- 6Al - 4V

High-pressure coolant effect on the surface integrity of machining titanium alloy Ti-6Al-4V: a review

NASA Astrophysics Data System (ADS)

Liu, Wentao; Liu, Zhanqiang

2018-03-01

Machinability improvement of titanium alloy Ti-6Al-4V is a challenging work in academic and industrial applications owing to its low thermal conductivity, low elasticity modulus and high chemical affinity at high temperatures. Surface integrity of titanium alloys Ti-6Al-4V is prominent in estimating the quality of machined components. The surface topography (surface defects and surface roughness) and the residual stress induced by machining Ti-6Al-4V occupy pivotal roles for the sustainability of Ti-6Al-4V components. High-pressure coolant (HPC) is a potential choice in meeting the requirements for the manufacture and application of Ti-6Al-4V. This paper reviews the progress towards the improvements of Ti-6Al4V surface integrity under HPC. Various researches of surface integrity characteristics have been reported. In particularly, surface roughness, surface defects, residual stress as well as work hardening are investigated in order to evaluate the machined surface qualities. Several coolant parameters (including coolant type, coolant pressure and the injection position) deserve investigating to provide the guidance for a satisfied machined surface. The review also provides a clear roadmap for applications of HPC in machining Ti-6Al4V. Experimental studies and analysis are reviewed to better understand the surface integrity under HPC machining process. A distinct discussion has been presented regarding the limitations and highlights of the prospective for machining Ti-6Al4V under HPC.

Characterization and diffusion model for the titanium boride layers formed on the Ti6Al4V alloy by plasma paste boriding

NASA Astrophysics Data System (ADS)

Keddam, Mourad; Taktak, Sukru

2017-03-01

The present study is focused on the estimation of activation energy of boron in the plasma paste borided Ti6Al4V alloy, which is extensively used in technological applications, using an analytical diffusion model. Titanium boride layers were successfully produced by plasma paste boriding method on the Ti6Al4V alloy in the temperature range of 973-1073 K for a treatment time ranging from 3 to 7 h. The presence of both TiB2 top-layer and TiB whiskers sub-layer was confirmed by the XRD analysis and SEM observations. The surface hardness of the borided alloy was evaluated using Micro-Knoop indenter. The formation rates of the TiB2 and TiB layers were found to have a parabolic character at all applied process temperatures. A diffusion model was suggested to estimate the boron diffusivities in TiB2 and TiB layers under certain assumptions, by considering the effect of boride incubation times. Basing on own experimental data on boriding kinetics, the activation energies of boron in TiB2 and TiB phases were estimated as 136.24 ± 0.5 and 63.76 ± 0.5 kJ mol-1, respectively. Finally, the obtained values of boron activation energies for Ti6Al4V alloy were compared with the data available in the literature.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods.

PubMed

Chanbi, Daoud; Ogam, Erick; Amara, Sif Eddine; Fellah, Z E A

2018-05-07

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods

PubMed Central

Chanbi, Daoud; Amara, Sif Eddine; Fellah, Z. E. A.

2018-01-01

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density. PMID:29735946

Centerless grinding of TiAl using conventional grinding wheels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, P.E.; Smits, D.; Eylon, D.

1995-12-31

Ordered gamma titanium aluminide (TiAl) based alloys are now under consideration for automotive valves because of their light weight and high strength at temperatures up to 850 C. Finishing comprises as much as 70% of the cost of an automotive valve, therefore the grindability of TiAl valves will influence their commercial viability. This study compared the grindability of the TiAl alloy Ti-47Al-2Nb-1.75Cr (at%) to standard valve steels, nickel base superalloys, and conventional titanium alloys using the centerless grinding process. Three grinding conditions simulating stem grinding were selected. The power requirements, grinding time, and grinding wheel consumption were used to estimatemore » the cost to grind TiAl on conventional centerless grinding equipment using vitrified bonded silicon carbide wheels. The metallurgical effects of rough and finish stem grinding cycles on the surface were determined. The grindability factor of TiAl, a measure of grinding cost, was slightly inferior to conventional valve steels, but much better than conventional titanium alloys. The high work hardening rate of the TiAl resulted in much better surface finish at high metal removal rates than that achieved in steels. No grinding cracks were observed, even under the rough grinding conditions. Microhardness profiles indicated significant work hardening of the surface under all three grinding conditions.« less

Microstructure and Tensile Behavior of Laser Arc Hybrid Welded Dissimilar Al and Ti Alloys

PubMed Central

Gao, Ming; Chen, Cong; Gu, Yunze; Zeng, Xiaoyan

2014-01-01

Fiber laser-cold metal transfer arc hybrid welding was developed to welding-braze dissimilar Al and Ti alloys in butt configuration. Microstructure, interface properties, tensile behavior, and their relationships were investigated in detail. The results show the cross-weld tensile strength of the joints is up to 213 MPa, 95.5% of same Al weld. The optimal range of heat input for accepted joints was obtained as 83–98 J·mm−1. Within this range, the joint is stronger than 200 MPa and fractures in weld metal, or else, it becomes weaker and fractures at the intermetallic compounds (IMCs) layer. The IMCs layer of an accepted joint is usually thin and continuous, which is about 1μm-thick and only consists of TiAl2 due to fast solidification rate. However, the IMCs layer at the top corner of fusion zone/Ti substrate is easily thickened with increasing heat input. This thickened IMCs layer consists of a wide TiAl3 layer close to FZ and a thin TiAl2 layer close to Ti substrate. Furthermore, both bead shape formation and interface growth were discussed by laser-arc interaction and melt flow. Tensile behavior was summarized by interface properties. PMID:28788533

Ti2Al(C, N) Solid Solution Reinforcing TiAl-Based Composites: Evolution of a Core-Shell Structure, Interfaces, and Mechanical Properties.

PubMed

Song, Xiaojie; Cui, Hongzhi; Han, Ye; Ding, Lei; Song, Qiang

2018-05-16

In this work, Ti 2 Al(C, N) solid solution with lamellar structure-enhanced TiAl matrix composites was synthesized by vacuum arc melting, using bulk g-C 3 N 4 , Ti, and Al powders as raw materials. The phases, microstructures, interfaces, and mechanical properties were investigated. MAX phase of Ti 2 Al(C, N) solid solution with lamellar structure was formed. During the melting process, first, C 3 N 4 reacted with Ti to form Ti(C, N) by Ti + C 3 N 4 → Ti(C, N). Then Ti 2 Al(C, N) was formed by a peritectic reaction of TiAl(l) + Ti(C, N)(s) → Ti 2 Al(C, N). C 3 N 4 is the single reactant that provides C and N simultaneously to final product of Ti 2 Al(C, N). The interfaces of TiAl//Ti 2 Al(C, N) and Ti 2 Al(C, N)//Ti(C, N) display perfect orientation relationships with low misfit values. The microhardness, compressive strength, and strain of best-performing TiAl-10 mol % Ti 2 Al(C, N) composite were improved by 45%, 55.7%, and 50% compared with the TiAl alloy, respectively. Uniformly distributed Ti 2 Al(C, N) and unreacted Ti(C, N) particles contributed to the grain refinement and reinforcement of the TiAl matrix. Laminated tearing, particle pull-out, and the crack-arresting of Ti 2 Al(C, N) are crucial for the improvement in compressive strength and plasticity of the composites.

The biological response to laser-aided direct metal-coated Titanium alloy (Ti6Al4V)

PubMed Central

Shin, T.; Lim, D.; Kim, Y. S.; Kim, S. C.; Jo, W. L.

2018-01-01

Objectives Laser-engineered net shaping (LENS) of coated surfaces can overcome the limitations of conventional coating technologies. We compared the in vitro biological response with a titanium plasma spray (TPS)-coated titanium alloy (Ti6Al4V) surface with that of a Ti6Al4V surface coated with titanium using direct metal fabrication (DMF) with 3D printing technologies. Methods The in vitro ability of human osteoblasts to adhere to TPS-coated Ti6Al4V was compared with DMF-coating. Scanning electron microscopy (SEM) was used to assess the structure and morphology of the surfaces. Biological and morphological responses to human osteoblast cell lines were then examined by measuring cell proliferation, alkaline phosphatase activity, actin filaments, and RUNX2 gene expression. Results Morphological assessment of the cells after six hours of incubation using SEM showed that the TPS- and DMF-coated surfaces were largely covered with lamellipodia from the osteoblasts. Cell adhesion appeared similar in both groups. The differences in the rates of cell proliferation and alkaline phosphatase activities were not statistically significant. Conclusions The DMF coating applied using metal 3D printing is similar to the TPS coating, which is the most common coating process used for bone ingrowth. The DMF method provided an acceptable surface structure and a viable biological surface. Moreover, this method is automatable and less complex than plasma spraying. Cite this article: T. Shin, D. Lim, Y. S. Kim, S. C. Kim, W. L. Jo, Y. W. Lim. The biological response to laser-aided direct metal-coated Titanium alloy (Ti6Al4V). Bone Joint Res 2018;7:357–361. DOI: 10.1302/2046-3758.75.BJR-2017-0222.R1. PMID:29922456

The Role of Surface Protection for High-Temperature Performance of TiAl Alloys

NASA Astrophysics Data System (ADS)

Schütze, Michael

2017-12-01

In the temperature range where TiAl alloys are currently being used in jet engine and automotive industries, surface reaction with the operating environment is not yet a critical issue. Surface treatment may, however, be needed in order to provide improved abrasion resistance. Development routes currently aim at a further increase in operation temperatures in gas turbines up to 800°C and higher, and in automotive applications for turbocharger rotors, even up to 1050°C. In this case, oxidation rates may reach levels where significant metal consumption of the load-bearing cross-section can occur. Another possibly even more critical issue can be high-temperature-induced oxygen and nitrogen up-take into the metal subsurface zone with subsequent massive ambient temperature embrittlement. Solutions for these problems are based on a deliberate phase change of the metal subsurface zone by diffusion treatments and by using effects such as the halogen effect to change the oxidation mechanism at high temperatures. Other topics of relevance for the use of TiAl alloys in high-temperature applications can be high-temperature abrasion resistance, thermal barrier coatings on TiAl and surface quality in additive manufacturing, in all these cases-focusing on the role of the operation environment. This paper addresses the recent developments in these areas and the requirements for future work.

Half-metallic ferromagnetism in {Ti}2 {IrZ} (Z = B, Al, Ga, and In) Heusler alloys: A density functional study

NASA Astrophysics Data System (ADS)

Sadeghi, K. H.; Ahmadian, F.

2018-02-01

The first-principle density functional theory (DFT) calculations were employed to investigate the electronic structures, magnetic properties and half-metallicity of {Ti}2 {IrZ} (Z = B, Al, Ga, and In) Heusler alloys with {AlCu}2 {Mn}- and {CuHg}2 {Ti}-type structures within local density approximation and generalised gradient approximation for the exchange correlation potential. It was found that {CuHg}2 {Ti}-type structure in ferromagnetic state was energetically more favourable than {AlCu}2 {Mn}-type structure in all compounds except {Ti}2 {IrB} which was stable in {AlCu}2 {Mn}-type structure in non-magnetic state. {Ti}2 {IrZ} (Z = B, Al, Ga, and In) alloys in {CuHg}2 {Ti}-type structure were half-metallic ferromagnets at their equilibrium lattice constants. Half-metallic band gaps were respectively equal to 0.87, 0.79, 0.75, and 0.73 eV for {Ti}2 {IrB}, {Ti}2 {IrAl}, {Ti}2 {IrGa}, and {Ti}2 {IrIn}. The origin of half-metallicity was discussed for {Ti}2 {IrGa} using the energy band structure. The total magnetic moments of {Ti}2 {IrZ} (Z = B, Al, Ga, and In) compounds in {CuHg}2 {Ti}-type structure were obtained as 2μ B per formula unit, which were in agreement with Slater-Pauling rule (M_{tot} =Z_{tot}-18). All the four compounds were half-metals in a wide range of lattice constants indicating that they may be suitable and promising materials for future spintronic applications.

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

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.

A comparison of the fatigue behavior of cast Ti-7.5Mo with c.p. titanium, Ti-6Al-4V and Ti-13Nb-13Zr alloys.

PubMed

Lin, Chia-Wei; Ju, Chien-Ping; Chern Lin, Jiin-Huey

2005-06-01

The purpose of the present study is to compare the high-cycle fatigue behavior of newly developed Ti-7.5Mo alloy with that of c.p. Ti, Ti-13Nb-13Zr and Ti-6Al-4V alloys in their as-cast state. Experimental results indicate that Ti-6Al-4V and c.p. Ti have higher stress-controlled fatigue resistance but lower strain-controlled fatigue resistance than Ti-7.5Mo and Ti-13Nb-13Zr. Among four materials Ti-7.5Mo demonstrates the best strain-controlled fatigue performance. The fracture surfaces of the present materials are comprised of three morphologically distinct zones: crack initiation zone, crack propagation zone, and the final-stage overload zone. The fatigue cracks almost always initiate from casting-induced surface/subsurface pores. A river pattern is observed in the propagation zone. In the overload zone dimples are typically observed. Three factors most significantly affecting the fatigue performance of the present materials are the presence of the casting-induced surface/subsurface pores; the location of the pores; and the inherent mechanical properties of the materials.

Plastic behavior of two-phase intermetallic compounds based on L1{sub 2}-type (Al,Cr){sub 3}Ti

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J.Y.; Wee, D.M.; Oh, M.H.

Plastic behavior of two-phase intermetallic compounds based on L1{sub 2}-type (Al,Cr){sub 3}Ti was investigated using compression test at R.T. and 77K. L1{sub 2} single phase alloys and two-phase alloys consisting of mainly L1{sub 2} phase and a few or 20% (mole percent) second phases were selected from Al-Ti-Cr phase diagram. In general, compared with L1{sub 2} single phase, two-phase alloys consisting of 20% second phase showed relatively high yield strength and poor ductility. Among the alloys, however, Al-21Ti-23Cr alloy consisting of 20% Cr{sub 2}Al phase showed available ductility as well as high yield strength. Plastic behavior of L1{sub 2} singlemore » phase alloys and two-phase alloys consisting of a few Cr{sub 2}Al was also investigated. Homogenization of arc melted ingots substantially reduced the amount of second phases but introduced extensive pore. When Cr content increased in L1{sub 2} single phase alloys after the homogenization, the volume fraction of pores in the alloys decreased, and no residual porosity was observed in two-phase alloys consisting of a few% Cr{sub 2}Al phase. Environmental effect on the ductility of the alloys was investigated using compression test at different strain rates (1.2 {times} 10{sup {minus}4}/s and 1.2 {times} 10{sup {minus}2}/s). Environmental embrittlement was least significant in Al-25Ti-10Cr alloy consisting of L1{sub 2} single phase among the alloys tested in this study. However, based on the combined estimation of the pore formation, environmental embrittlement and ingot cast structure, it could be supposed that Al-21Ti-23Cr alloy consisting of 20% Cr{sub 2}Al as a second phase is expected to show the best tensile elongation behavior among the materials tested.« less

Biocompatible low Young's modulus achieved by strong crystallographic elastic anisotropy in Ti-15Mo-5Zr-3Al alloy single crystal.

PubMed

Lee, S-H; Todai, M; Tane, M; Hagihara, K; Nakajima, H; Nakano, T

2012-10-01

The elastic anisotropy of the Ti-15Mo-5Zr-3Al (mass%) β-Ti alloy, an ISO certified biomedical material, was investigated using its single crystal. It was revealed that the Young's modulus exhibited pronounced anisotropy. The Young's modulus was reduced to 44.4GPa along the 〈100〉 direction in the Ti-15Mo-5Zr-3Al single crystal, that is comparable to that of human cortical bones. We determined the strategy that β-Ti alloys with extremely low moduli can be developed by reducing the electron-atom (e/a) ratio in alloys, and by suppressing the formation of the ω-phase at the same time. This new knowledge must lead to the development of "single crystalline β-Ti implant materials" as hard tissue replacements for reducing the stress shielding effect. Copyright © 2012 Elsevier Ltd. All rights reserved.

An Experimental Investigation of Effects of Fluxes (Na3AlF6 and K2TiF6), Element Alloys (Mg), and Composite Powders ((Al + TiC)CP and (Al + B4C)CP) on Distribution of Particles and Phases in Al-B4C and Al-TiC Composites

NASA Astrophysics Data System (ADS)

Mazaheri, Younes; Emadi, Rahmatollah; Meratian, Mahmood; Zarchi, Mehdi Karimi

2017-04-01

The wettability, incorporation, and gravity segregation of TiC and B4C particles into molten aluminum are important problems in the production of Al-TiC and Al-B4C composites by the casting techniques. In order to solve these problems, different methods consisting of adding the Na3AlF6 and K2TiF6 fluxes and Mg (as the alloying element) into the molten aluminum and injection of the (Al + TiC)CP and (Al + B4C)CP composite powders instead of B4C and TiC particles are evaluated. In this work, the conditions of sample preparation, such as particle addition temperature, stirring speed, and stirring time, are determined after many studies and tests. Microstructural characterizations of samples are investigated by scanning electron microscopy equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometry. The results show better distribution and incorporation of TiCp and B4Cp in aluminum matrix when the fluxes are used, as well as EDS analysis of the interface between the matrix and reinforcement-strengthened formation of the different phases such as Al4C3 in the Al-TiC composites and Al3BC, TiB2 in the Al-B4C composites.

Microstructural stability of fine-grained fully lamellar XD TiAl alloys by step aging

NASA Astrophysics Data System (ADS)

Zhu, Hanliang; Maruyama, K.; Seo, D. Y.; Au, P.

2005-05-01

XD TiAl alloys (Ti-45 and 47Al-2Nb-2Mn+0.8 vol pct TiB2) (at. pct) were oil quenched to produce fine-grained fully lamellar (FGFL) structures, and aging treatments at different temperatures for different durations were carried out to stabilize the FGFL structures. Microstructural examinations show that the aging treatments cause phase transformation of α 2 to γ, resulting in stabilization of the lamellar structure, as indicated by a significant decrease in α 2 volume fraction. However, several degradation processes are also introduced. After aging, within lamellar colonies, the α 2 lamellae become finer due to dissolution, whereas most of the γ lamellae coarsen. The dissolution of α 2 involves longitudinal dissolution and lateral dissolution. In addition, at lamellar colony boundaries, lamellar termination migration, nucleation and growth of γ grains, and discontinuous coarsening occur. With the exception of longitudinal dissolution, all the other transformation modes are considered as degradation processes as they result in a reduction in α 2/ γ interfaces. Different phase transformation modes are present to varying degrees in the aged FGFL structures, depending on aging conditions and Al content. A multiple step aging reduces the drive force for phase transformation at high temperature by promoting phase transformation via longitudinal dissolution at low temperatures. As a result, this aging procedure effectively stabilizes the lamellar structure and suppresses other degradation processes. Therefore, the multiple step aging is suggested to be an optimal aging condition for stabilizing FGFL XD TiAl alloys.

Formation of Al3Ti/Mg composite by powder metallurgy of Mg-Al-Ti system.

PubMed

Yang, Zi R; Qi Wang, Shu; Cui, Xiang H; Zhao, Yu T; Gao, Ming J; Wei, Min X

2008-07-01

An in situ titanium trialuminide (Al 3 Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg-Al-Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al 3 Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg-Al-Ti system, Al 3 Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg-Al-Ti system is almost the same as that of the Al-Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

Novel twin-roll-cast Ti/Al clad sheets with excellent tensile properties.

PubMed

Kim, Dae Woong; Lee, Dong Ho; Kim, Jung-Su; Sohn, Seok Su; Kim, Hyoung Seop; Lee, Sunghak

2017-08-14

Pure Ti or Ti alloys are recently spot-lighted in construction industries because they have excellent resistance to corrosions, chemicals, and climates as well as various coloring characteristics, but their wide applications are postponed by their expensiveness and poor formability. We present a new fabrication process of Ti/Al clad sheets by bonding a thin Ti sheet on to a 5052 Al alloy melt during vertical-twin-roll casting. This process has merits of reduced production costs as well as improved tensile properties. In the as-twin-roll-cast clad sheet, the homogeneously cast microstructure existed in the Al alloy substrate side, while the Ti/Al interface did not contain any reaction products, pores, cracks, or lateral delamination, which indicated the successful twin-roll casting. When this sheet was annealed at 350 °C~600 °C, the metallurgical bonding was expanded by interfacial diffusion, thereby leading to improvement in tensile properties over those calculated by a rule of mixtures. The ductility was also improved over that of 5052-O Al alloy (25%) or pure Ti (25%) by synergic effect of homogeneous deformation due to excellent Ti/Al bonding. This work provides new applications of Ti/Al clad sheets to lightweight-alloy clad sheets requiring excellent formability and corrosion resistance as well as alloy cost saving.

Effect of stabilization annealing on SCC susceptibility of β-annealed Ti-6Al-4V alloy in 0.6 M NaCl solution

NASA Astrophysics Data System (ADS)

Jeong, Daeho; Park, Jiho; Ahn, Soojin; Sung, Hyokyung; Kwon, Yongnam; Kim, Sangshik

2018-01-01

The effect of stabilization annealing on the stress corrosion cracking (SCC) susceptibility of β-annealed Ti-6Al-4V (Ti64) alloy was examined in an aqueous 0.6 M NaCl solution under various applied potentials of +0.1, -0.05 and -0.1 V vs Ecorr, respectively, at a strain rate of 10 -6 s -1. The stabilization annealing substantially improved the resistance to SCC of β-annealed Ti64 alloy in 0.6 M NaCl solution under cathodic applied potentials, while the effect was marginal under an anodic applied potential. It was also noted that the areal fraction between ductile and brittle fracture of β-annealed Ti64 specimens, which were slow strain rate tested in 0.6 M NaCl solution, varied with stabilization annealing and applied potentials. The effect of stabilization annealing on the SCC behavior of β-annealed Ti64 alloy in SCC-causing environment was discussed based on the micrographic and fractographic observation.

Technological capabilities of surface layers formation on implant made of Ti-6Al-4V ELI alloy.

PubMed

Kiel-Jamrozik, Marta; Szewczenko, Janusz; Basiaga, Marcin; Nowińska, Katarzyna

2015-01-01

The aim of the presented research was to find a combination of surface modification methods of implants made of the Ti-6Al-4V ELI alloy, that lead to formation of effective barrier for metallic ions that may infiltrate into solution. To this end, the following tests were carried out: roughness measurement, the voltamperometric tests (potentiodynamic and potentiostatic), and the ion infiltration test. The electropolishing process resulted in the lowering of surface roughness in comparison with mechanical treatment of the surface layer. The anodization process and steam sterilization increased corrosion resistance regardless of the mechanical treatment or electropolishing. The crevice corrosion tests revealed that independent of the modification method applied, the Ti-6Al-4V ELI alloy has excellent crevice corrosion resistance. The smallest quantity of ions infiltrated to the solution was observed for surface modification consisting in the mechanical treatment and anodization with the potential of 97 V. Electric parameters deter- mined during studies were the basis for effectiveness estimation of particular surface treatment methods. The research has shown that the anodization process significantly influences the pitting corrosion resistance of the Ti-6Al-4V ELI alloy independent of the previous surface treatment methods (mechanical and electrochemical). The surface layer after such modification is a protective barrier for metallic ions infiltrated to solution and protects titanium alloy against corrosive environment influence.

Characteristics of surface modified Ti-6Al-4V alloy by a series of YAG laser irradiation

NASA Astrophysics Data System (ADS)

Zeng, Xian; Wang, Wenqin; Yamaguchi, Tomiko; Nishio, Kazumasa

2018-01-01

In this study, a double-layer Ti (C, N) film was successfully prepared on Ti-6Al-4V alloy by a series of YAG laser irradiation in nitrogen atmosphere, aiming at improving the wear resistance. The effects of laser irradiation pass upon surface chemical composition, microstructures and hardness were investigated. The results showed that the surface chemicals were independent from laser irradiation pass, which the up layer of film was a mixture of TiN and TiC0.3N0.7, and the down layer was nitrogen-rich α-Ti. Both the surface roughness and hardness increased as raising the irradiation passes. However, surface deformation and cracks happened in the case above 3 passes' irradiation. The wear resistance of laser modified sample by 3 passes was improved approximately by 37 times compared to the as received substrate. Moreover, the cytotoxic V ion released from laser modified sample was less than that of as received Ti-6Al-4V alloy in SBF, suggesting the potentiality of a new try to modify the sliding part of Ti-based hard tissue implants in future biomedical application.

The effect of TiB2 reinforcement on the mechanical properties of an Al-Cu-Li alloy-based metal-matrix composite

NASA Technical Reports Server (NTRS)

Langan, T. J.; Pickens, J. R.

1991-01-01

Weldalite 049, an Al-base Cu-Li-Mg-Ag-Zr alloy, achieves 700 MPa tensile strengths in the near-peak-aged temper in virtue of the nucleation of a T(1)-type platelike strengthening precipitate. Attention is presently given to the possibility that the alloy's modulus could be further increased through the addition of high-modulus TiB2 particles, using the 'XD' process, due to TiB2's good wettability with liquid Al. An 8-percent modulus increase is obtained with 4 vol pct TiB2.

Modeling of Processing-Induced Pore Morphology in an Additively-Manufactured Ti-6Al-4V Alloy

PubMed Central

Kabir, Mohammad Rizviul; Richter, Henning

2017-01-01

A selective laser melting (SLM)-based, additively-manufactured Ti-6Al-4V alloy is prone to the accumulation of undesirable defects during layer-by-layer material build-up. Defects in the form of complex-shaped pores are one of the critical issues that need to be considered during the processing of this alloy. Depending on the process parameters, pores with concave or convex boundaries may occur. To exploit the full potential of additively-manufactured Ti-6Al-4V, the interdependency between the process parameters, pore morphology, and resultant mechanical properties, needs to be understood. By incorporating morphological details into numerical models for micromechanical analyses, an in-depth understanding of how these pores interact with the Ti-6Al-4V microstructure can be gained. However, available models for pore analysis lack a realistic description of both the Ti-6Al-4V grain microstructure, and the pore geometry. To overcome this, we propose a comprehensive approach for modeling and discretizing pores with complex geometry, situated in a polycrystalline microstructure. In this approach, the polycrystalline microstructure is modeled by means of Voronoi tessellations, and the complex pore geometry is approximated by strategically combining overlapping spheres of varied sizes. The proposed approach provides an elegant way to model the microstructure of SLM-processed Ti-6Al-4V containing pores or crack-like voids, and makes it possible to investigate the relationship between process parameters, pore morphology, and resultant mechanical properties in a finite-element-based simulation framework. PMID:28772504

Modeling of Processing-Induced Pore Morphology in an Additively-Manufactured Ti-6Al-4V Alloy.

PubMed

Kabir, Mohammad Rizviul; Richter, Henning

2017-02-08

A selective laser melting (SLM)-based, additively-manufactured Ti-6Al-4V alloy is prone to the accumulation of undesirable defects during layer-by-layer material build-up. Defects in the form of complex-shaped pores are one of the critical issues that need to be considered during the processing of this alloy. Depending on the process parameters, pores with concave or convex boundaries may occur. To exploit the full potential of additively-manufactured Ti-6Al-4V, the interdependency between the process parameters, pore morphology, and resultant mechanical properties, needs to be understood. By incorporating morphological details into numerical models for micromechanical analyses, an in-depth understanding of how these pores interact with the Ti-6Al-4V microstructure can be gained. However, available models for pore analysis lack a realistic description of both the Ti-6Al-4V grain microstructure, and the pore geometry. To overcome this, we propose a comprehensive approach for modeling and discretizing pores with complex geometry, situated in a polycrystalline microstructure. In this approach, the polycrystalline microstructure is modeled by means of Voronoi tessellations, and the complex pore geometry is approximated by strategically combining overlapping spheres of varied sizes. The proposed approach provides an elegant way to model the microstructure of SLM-processed Ti-6Al-4V containing pores or crack-like voids, and makes it possible to investigate the relationship between process parameters, pore morphology, and resultant mechanical properties in a finite-element-based simulation framework.

Microstructure and wear resistance of one-step in-situ synthesized TiN/Al composite coatings on Ti6Al4V alloy by a laser nitriding process

NASA Astrophysics Data System (ADS)

Fu, Yao; Zhang, Xian-Cheng; Sui, Jian-Feng; Tu, Shan-Tung; Xuan, Fu-Zhen; Wang, Zheng-Dong

2015-04-01

The aim of this paper was to develop a one-step in situ method to synthesize the TiN reinforced Al metallic matrix composite coatings on Ti6Al4V alloy. In this method, the Al powder and nitrogen gas were simultaneously fed into feeding nozzle during a laser nitriding process. The microstructure, microhardness and sliding wear resistance of TiN/Al coatings synthesized at different laser powers in laser nitriding were investigated. Results showed that the crack- and pore-free coatings can be made through the proposed method. However, the morphologies and distribution of TiN dendrites and wear resistance of coatings were strongly dependent on laser power used in nitriding. With increasing the laser power, the amount and density of massive TiN dendritic structure in the coating decreased and the elongated and narrow dendrites increased, leading to the increment of wear resistance of coating. When the laser power is high, the convectional flow pattern of the melt pool can be seen near the bottom of pool.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of alloying elements and heat treatment on the fracture toughness of Ti-Al-Nb alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamat, S.V.; Gogia, A.K.; Banerjee, D.

The fracture toughness and toughening mechanisms of Ti{sub 3}Al based alloy compositions covering a large range of Nb, small variations in Al and quaternary substitutions of Nb have been studied in a variety of heat treated conditions designed to vary the volume fractions of the constituents phases. It was found that the B2 phase of these alloys failed by cleavage in a coarse grained condition but in a ductile manner when fine grained. A higher Nb and a lower Al content improved the cleavage fracture stress of the B2 phase while replacement of a part of Nb and a lowermore » Al content improved the cleavage fracture stress of the B2 phase while replacement of a part of Nb with Mo or Ta had no significant effect. Heat treatments which result in a two phase microstructure ({alpha}{sub 2} + {beta}/B2) exhibited a trend of increasing fracture toughness with increasing volume fraction of {beta}/B2 up to about 60--80 volume fraction of {beta}/B2. This behavior was largely explained by quantifying the role of crack tip blunting. The effect of alloying elements on fracture toughness in two phase microstructures was similar to that observed in the coarse grained B2 condition.« less

Microstructure and wear resistance of Ti-Cu-N composite coating prepared via laser cladding/laser nitriding technology on Ti-6Al-4V alloy

NASA Astrophysics Data System (ADS)

Yang, Yuling; Cao, Shiyin; Zhang, Shuai; Xu, Chuan; Qin, Gaowu

2017-07-01

Ti-Cu-N coatings with three different Cu contents on Ti-6Al-4V alloy (TC4) were obtained via laser cladding together with laser nitriding (LC/LN) technology. Phase constituents, microstructure, microhardness, and wear resistance of the coatings were investigated. The evolution of the coefficients of friction for the three coatings was measured under dry sliding conditions as a function of the revolutions until the coating failure. The results show that the coatings are mainly composed of TiN, CuTi3 and some TiO6 phases dispersed in the matrix. A good metallurgical bonding between the coating and substrate has been successfully obtained. The prepared Ti-Cu-N composite coatings almost doubly enhance the microhardness of the TC4 alloy and reduce the friction down to 1/4-1/2 of the TC4 alloy, and thus significantly improve the wear resistance. The coefficient of friction depends on the Cu content in the coating.

Grain Refinement and Mechanical Properties of Cu–Cr–Zr Alloys with Different Nano-Sized TiCp Addition

PubMed Central

Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

2017-01-01

The TiCp/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiCp/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiCp-reinforced Cu–Cr–Zr composites. Results show that nano-sized TiCp can effectively refine the grain size of Cu–Cr–Zr alloys. The morphologies of grain in Cu–Cr–Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiCp. The grain size decreased from 82 to 28 μm with the nano-sized TiCp content. Compared with Cu–Cr–Zr alloys, the ultimate compressive strength (σUCS) and yield strength (σ0.2) of 4 wt% TiCp-reinforced Cu–Cr–Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu–Cr–Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiCp-reinforced Cu–Cr–Zr composites decreased with the increasing TiCp content under abrasive particles. The eletrical conductivity of Cu–Cr–Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu–Cr–Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively. PMID:28786937

Effect of quenching medium on the microstructure of hot rolled Ti-6Al-6Nb alloy for medical application

NASA Astrophysics Data System (ADS)

Sutowo, Cahya; Alhamidi, A. Ali; Basir, Muh. Idrus Abdul; Rokhmanto, Fendy

2018-05-01

The Ti-6Al-6Nb alloy has been used as bone plate in biomedical application. But, its modulus elasticity still lies above its cortical-bone, which causes stress shielding. An alternative process for reduce modulus of elasticity by means of treatment solutions with heating β-transus temperature follows with rapid cooling for obtaining high % intensity of β-phase fractions. In this study the Ti-6Al-6Nb as-cast alloys were homogenized at 1050 °C for 12 hours, then hot-rolled with a reduction 60% (from 10mm to 4 mm thickness) at 1000 °C and then dissolved at 1100 °C for 2 hours and then cooled by water, oil and air. The microstructural observations were performed with OM and SEM-EDS. The phase analyzes were observed by XRD test and mechanical properties observed by Ultrasonic test. The observation result shows the elasticity modulus value in alloys which being ST with cooling is 106,71 GPa. This is consistent with the observation of the microstructure that the presence of β-transformed and it is also in accordance with the XRD analysis and the intensity of the phase fraction, where the peak and% intensity of the β (35%) phase fraction increase in alloys which ST and oil quench.

Air Oxidation Behavior of Two Ti-Base Alloys Synthesized by HIP

NASA Astrophysics Data System (ADS)

Liu, S.; Guo, Q. Q.; Liu, L. L.; Xu, L.; Liu, Y. Y.

2016-04-01

The oxidation behavior of Ti-5Al-2.5Sn and Ti-6Al-4V produced by hot isostatic pressing (HIP) has been studied at 650-850°C in air for 24 h. The oxidation kinetics of both alloys followed the parabolic law with good approximation, except for Ti-5Al-2.5Sn oxidized at 850°C. Multi-layered scales formed on both alloys at 750°C and 850°C. Ternary additions of Sn and V accounted for the different morphology of the scales formed on these two alloys. In addition, the oxidation behavior of HIP alloys is compared with that of the corresponding cast alloys and the scaling mechanism is discussed.

Schaeffler-Type Phase Diagram of Ti-Based Alloys

NASA Astrophysics Data System (ADS)

Ishida, K.

2017-10-01

The α(hcp)/β(bcc) phase equilibria of Ti-based multi-component alloys can be described by a Schaeffler-type diagram, where Al and Mo equivalents (Aleq and Moeq) are used. Aleq is thermodynamically defined by the ratio of partial molar free energy changes transfer of one mole of each α forming element and Al from a dilute solution of α to β phases, while Moeq is also deduced by similar thermodynamic quantities of β forming element and Mo. Aleq and Moeq for 40 alloying elements are estimated from the thermodynamic parameters assessed by Kaufman and Murray. It is shown that three types of Ti alloys, i.e., α and near α, α+β, and β alloys, can be exactly classified using Aleq and Moeq. The Ms and β transus temperatures can also be predicted by Aleq and Moeq. The proposed Aleq and Moeq are very useful for alloy design, heat treatment, and microstructural evolution of Ti-based alloys.

Formation Of Nano Layered Lamellar Structure In a Processed γ-TiAl Based Alloy

NASA Astrophysics Data System (ADS)

Heshmati-Manesh, S.; Shakoorian, H.; Armaki, H. Ghassemi; Ahmadabadi, M. Nili

2009-06-01

In this research, microstructures of an intermetallic alloy based on γ-TiAl has been investigated by optical and transmission electron microscopy. Samples of Ti-47Al-2Cr alloy were subjected to either a cyclic heat treatment or thermomechanical treatment with the aim of microstructural refinement. In both cases it was found that very fine lamellar structure with an interlamellar spacing in the nano scale is formed. Upon cyclic heat treatment, nano layers of α2 and γ ordered intermetallic phases were either formed during rapid cooling cycle in competition with massive structure formation, or formed as secondary lamellar structure during final stages of cyclic heat treatment. Also, TEM observations in hot forged specimens with initial lamellar structure revealed that micro twins form during the deformation within lamellar structure with twinning plates parallel to lamellar interfaces. Concurrent dynamic recrystallisation results in a nano layered structure with an interlamellar spacing of less than 100 nm.

Oxidation studies of Fe10CrAl-RE alloys exposed to Pb at 550 °C for 10,000 h

NASA Astrophysics Data System (ADS)

Ejenstam, Jesper; Halvarsson, Mats; Weidow, Jonathan; Jönsson, Bo; Szakalos, Peter

2013-11-01

Five experimental FeCrAl-RE alloys have been exposed up to 10,000 h in stagnant liquid Pb at 550 °C. The test matrix consisted of three 10 wt.% Cr alloys, with an Al content ranging from 4 to 8 wt.% (10Cr-4Al, 10Cr-6Al and 10Cr-8Al), one alloy without additions of reactive elements (RE) (10Cr-6Al), and one reference alloy with 21 wt.% Cr and 5 wt.% Al (21Cr-5Al). The evaluation showed a clear difference in oxidation properties, and it was possible to divide the alloys into two distinct groups. A critical Al concentration in the interval of 4-6 wt.% at the given RE content was required to form a thin protective oxide. However, the absence of RE addition in one of the two 10Cr-6Al alloys resulted in a significant reduction in oxidation resistance, comparable with 10Cr-4Al. None of the alloys were severely corroded, however Pb penetrated to a relatively large extent into the porous oxide of the low performing alloys. A 100 nm thick oxide scale, partly consisting of alumina (Al2O3), was observed for the high performing 10Cr-6Al alloy. The Fe10CrAl-RE alloys showed overall very good corrosion resistance and are hence a promising new alloy category for liquid Pb applications.

Weldability of high toughness Fe-12% Ni alloys containing Ti, Al or Nb

NASA Technical Reports Server (NTRS)

Devletian, J. H.; Stephens, J. R.; Witzke, W. R.

1977-01-01

Three exceptionally high-toughness Fe-12%Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy (KIed) fracture toughness tests, transverse-weld tensile tests at -196 and 25 C and weld crack sensitivity tests. The Fe-12%Ni-0.25%Ti alloy proved extremely weldable for cryogenic applications, having weld and HAZ properties comparable with those of the wrought base alloy. The Fe-12%Ni-0.5%Al had good weld properties only after the weld joint was heat treated. The Fe-12%Ni-0.25%Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.

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.

Effect of time variation on coating characteristic of Ti-6Al-4V alloy coated with TiO2 by dip coating method

NASA Astrophysics Data System (ADS)

Hashim Aneed, Shaymaa

2018-05-01

In this reserch samples of Ti-6Al-4V alloy was coated with TiO2 layer by dip coating method in solution consist of 8 gm TiO2 nanoparticle dissolved in 100 ml. ethanol absolute (99%) and 1 gm P2O5, with various coating periods (1,2,3) minuts. The corrosion characteristics was investigated using (parstat 2273,USA made),the corrosion rate reach to 7.047 × 10-4 mm/y for sample coated at 3 minutes compared with 8.266 × 10-3mm/y for uncoated sample. Then the samples immersed in simulated body fluid (SBF) synthesized in the laboratory for one month in order to investigate the osseointegration from hydroxyapatite biomimatically formed, the corrosion charactaristics also invistigated after immirsing in (SBF) and it was 1.479 × 10-4 mm/y. For each part of reaserch we test the optical microscopic images,XRD and SEM in order to evaluate the results.

The growth of protective ultra-thin alumina layers on γ-TiAl(1 1 1) intermetallic single-crystal surfaces

NASA Astrophysics Data System (ADS)

Maurice, V.; Despert, G.; Zanna, S.; Josso, P.; Bacos, M.-P.; Marcus, P.

2005-12-01

An XPS and AES study of the early stages of oxidation of γ-TiAl(1 1 1) surfaces at 650 °C under 1.0 × 10 -7-1.0 × 10 -6 mbar O 2 is reported. The data evidence a first regime of oxidation characterized by the growth of a pure alumina layer followed by a second regime of simultaneous oxidation of both alloying elements. In the first regime, continuous alumina layers from ˜0.4 to ˜1.5 nm thick have been observed by angle-resolved XPS. The composition of the metallic phase underneath the growing oxide is modified by a depletion of Al and the injection of Al vacancies in the metal during the growth of the transient alumina formed at 650 °C. The onset of Ti oxidation was repeatedly observed for a critical concentration in the modified region of the alloy underneath the alumina layer: Ti 75±2Al 25±2 (Ti 50Al 17±2V(Al) 33±2), showing that decreasing the number of Ti-Al bonds in the modified intermetallic region increases the activity of Ti up to a critical point where its oxidation at the oxide/metal interface becomes competitive with that of Al. The growth of Ti 3+ and Ti 4+ oxide particles observed above the alumina layer by angle-resolved XPS indicates the transport of titanium cations trough the alumina layer and their subsequent reaction with oxygen at the outer gas/oxide interface. Improving structural ordering in the intermetallic phase slows down the growth kinetics of the alumina layer and the related Al-depletion of the substrate, and increases the resistance of the alloy to the subsequent oxidation of Ti. This is assigned to two combined effects: a slower diffusion of Al in the better ordered metallic phase and the growth of less defective alumina layers allowing to slow down the ionic transport through the oxide. Highly stable and corrosion resistant alloy surfaces covered by a 0.4 nm thick alumina layer have been obtained by slowly oxidizing the alloy at lower partial pressure (<5.0 × 10 -10 mbar O 2).

Thermo-mechanical treatment of low-cost alloy Ti-4.5Al-6.9Cr-2.3Mn and microstructure and mechanical characteristics

NASA Astrophysics Data System (ADS)

Chen, Guangyao; Kang, Juyun; Wang, Shusen; Wang, Shihua; Lu, Xionggang; Li, Chonghe

2018-04-01

In this study, the thermo-mechanical treatment process for low-cost Ti-4.5Al-6.9Cr-2.3Mn alloy were designed on the basis of assessment of Ti-Al-Cr-Mn thermodynamic system. The microstructure and mechanical properties of Ti-4.5Al-6.9Cr-2.3Mn forging and sheet were investigated by using the OM, SEM and universal tensile testing machine. The results show that both the forging and sheet were consisted of α + β phase, which is consistent with the expectation, and no element Cr and Mn existed in the grain boundaries of the sheet after quenching, and the C14 laves phase was not detected. The average ultimate tensile strength (σ b), 0.2% proof strength (σ 0.2) and elongation (EI) of alloy sheet after quenching can reach 1059 MPa, 1051 MPa and 24.6 Pct., respectively. Moreover, the average ultimate tensile strength of Ti-4.5Al-6.9Cr-2.3Mn forgings can reach 1599 MPa and the average elongation can reach 11.2 Pct., and a more excellent property of Ti-4.5Al-6.9Cr-2.3Mn forging is achieved than that of TC4 forging. It provides a theoretical support for further developing this low-cost alloy.

Influence of strain rate on the structure/property behavior of the alpha-2 alloy Ti-24.5Al-10.5Nb-1.5Mo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, G.T. III; Hong, Sun Ig; Marquardt, B.J.

Preliminary dislocation g{center_dot}b analysis revealed that following room temperature deformation at low strain rate the majority of the dislocations are a-dislocations lying on basal planes, 2nd order pyramidal (a/2 + c) slip on [1211], and 1st order pyramidal a-slip on [1011]. Increasing the rate of deformation at room temperature to 6000 s{sup {minus}1} is seen to result in increased a-slip on prism planes and a decreased amount of basal slip. At high-strain-rates and elevated temperatures the substructure was seen to be generally similar to that observed following high-rate deformation at room temperature except for an increased amount of basal slipmore » and a somewhat higher incidence of 2nd order pyramidal slip. The defect generation and the rate sensitivity of Ti-24.5Al-10.5Nb-1.5Mo are discussed as a function of strain rate and temperature and contrasted to that observed in conventional titanium alloys and TiAl.« less

Thermophysical Properties of Solid and Liquid Ti-6Al-4V (TA6V) Alloy

NASA Astrophysics Data System (ADS)

Boivineau, M.; Cagran, C.; Doytier, D.; Eyraud, V.; Nadal, M.-H.; Wilthan, B.; Pottlacher, G.

2006-03-01

Ti-6Al-4V (TA6V) titanium alloy is widely used in industrial applications such as aeronautic and aerospace due to its good mechanical properties at high temperatures. Experiments on two different resistive pulse heating devices (CEA Valduc and TU-Graz) have been carried out in order to study thermophysical properties (such as electrical resistivity, volume expansion, heat of fusion, heat capacity, normal spectral emissivity, thermal diffusivity, and thermal conductivity) of both solid and liquid Ti-6Al-4V. Fast time-resolved measurements of current, voltage, and surface radiation and shadowgraphs of the volume have been undertaken. At TU-Graz, a fast laser polarimeter has been used for determining the emissivity of liquid Ti-6Al-4V at 684.5 nm and a differential scanning calorimeter (DSC) for measuring the heat capacity of solid Ti-6Al-4V. This study deals with the specific behavior of the different solid phase transitions (effect of heating rate) and the melting region, and emphasizes the liquid state ( T > 2000 K).

Site preference of ternary alloying additions to NiTi: Fe, Pt, Pd, Au, Al, Cu, Zr and Hf

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Ronald D.; Mosca, Hugo O.

2004-01-01

Atomistic modeling of the site substitution behavior of Pd in NiTi (J. Alloys and Comp. (2004), in press) has been extended to examine the behavior of several other alloying additions, namely, Fe, Pt, Au, Al, Cu, Zr and Hf in this important shape memory alloy. It was found that all elements, to a varying degree, displayed absolute preference for available sites in the deficient sublattice. How- ever, the energetics of the different substitutional schemes, coupled with large scale simulations indicate that the general trend in all cases is for the ternary addition to want to form stronger ordered structures with Ti.

Effect of surface contamination on adhesive bonding of cast pure titanium and Ti-6Al-4V alloy.

PubMed

Watanabe, I; Watanabe, E; Yoshida, K; Okabe, T

1999-03-01

There is little information regarding bond strengths of resin cements to cast titanium surfaces contaminated by investment material. This study examined the effect of surface contamination on the shear bond strength of resin cements to cast titanium and Ti-6Al-4V alloy. Two types of disks were cast from commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy ingots using an argon-arc pressure casting unit and a phosphate-bonded Al2 O3 /LiAlSiO6 investment. After casting, disks were subjected to 3 surface treatments: (1) cast surface sandblasted (50 microm-sized Al2 O3 ) for 30 seconds; (2) metal surface sanded with silicon-carbide paper (600 grit) after grinding the contaminated cast surface (approximately 200 microm in thickness); and (3) metal surface sandblasted for 30 seconds after treatment 2. Surface structures were examined after each treatment with SEM and optical microscopy. Each type of disk was then bonded with 2 types of luting materials. Bonded specimens were subjected to thermocycling for up to 50,000 cycles, and shear bond strengths were determined after 0 (baseline) and 50,000 thermocycles. Results were statistically analyzed with 3-way ANOVA (P <.05). Microscopic observation of cast CP-Ti and Ti-6Al-4V exhibited noticeable structures on the cast surfaces apparently contaminated with investment material. However, there were no statistical differences (P >.05) in the bond strengths of both cements between contaminated (treatment 1) and uncontaminated surfaces (treatment 3) for both metals at baseline and after 50,000 thermocycles. The bond strength of specimens sanded with silicon-carbide paper (treatment 2) deteriorated dramatically after 50,000 thermocycles. Contamination of the cast metal surfaces by elements of the investment during casting did not affect bond strengths of the luting materials to CP-Ti and Ti-6Al-4V.

Grain Refinement and Mechanical Properties of Cu-Cr-Zr Alloys with Different Nano-Sized TiCp Addition.

PubMed

Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

2017-08-08

The TiC p /Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiC p /Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu-Cr-Zr alloys to fabricate the nano-sized TiC p -reinforced Cu-Cr-Zr composites. Results show that nano-sized TiC p can effectively refine the grain size of Cu-Cr-Zr alloys. The morphologies of grain in Cu-Cr-Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiC p . The grain size decreased from 82 to 28 μm with the nano-sized TiC p content. Compared with Cu-Cr-Zr alloys, the ultimate compressive strength (σ UCS ) and yield strength (σ 0.2 ) of 4 wt% TiC p -reinforced Cu-Cr-Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu-Cr-Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiC p -reinforced Cu-Cr-Zr composites decreased with the increasing TiC p content under abrasive particles. The eletrical conductivity of Cu-Cr-Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu-Cr-Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively.

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.

Effects of Plasma ZrN Metallurgy and Shot Peening Duplex Treatment on Fretting Wear and Fretting Fatigue Behavior of Ti6Al4V Alloy.

PubMed

Tang, Jingang; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing; Yu, Shouming

2016-03-23

A metallurgical zirconium nitride (ZrN) layer was fabricated using glow metallurgy using nitriding with zirconiuming prior treatment of the Ti6Al4V alloy. The microstructure, composition and microhardness of the corresponding layer were studied. The influence of this treatment on fretting wear (FW) and fretting fatigue (FF) behavior of the Ti6Al4V alloy was studied. The composite layer consisted of an 8-μm-thick ZrN compound layer and a 50-μm-thick nitrogen-rich Zr-Ti solid solution layer. The surface microhardness of the composite layer is 1775 HK 0.1 . A gradient in cross-sectional microhardness distribution exists in the layer. The plasma ZrN metallurgical layer improves the FW resistance of the Ti6Al4V alloy, but reduces the base FF resistance. This occurs because the improvement in surface hardness results in lowering of the toughness and increasing in the notch sensitivity. Compared with shot peening treatment, plasma ZrN metallurgy and shot peening composite treatment improves the FW resistance and enhances the FF resistance of the Ti6Al4V alloy. This is attributed to the introduction of a compressive stress field. The combination of toughness, strength, FW resistance and fatigue resistance enhance the FF resistance for titanium alloy.

Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modification.

PubMed

Kon, Masayuki; Hirakata, Luciana M; Asaoka, Kenzo

2004-01-15

Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128-178 MPa and 16-18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used. Copyright 2003 Wiley Periodicals, Inc.

The effect of fluoride ions on the corrosion behaviour of Ti metal, and Ti6-Al-7Nb and Ti-6Al-4V alloys in artificial saliva.

PubMed

Milošev, Ingrid; Kapun, Barbara; Selih, Vid Simon

2013-01-01

Metallic materials used for manufacture of dental implants have to exhibit high corrosion resistance in order to prevent metal release from a dental implant. Oral cavity is aggressive towards metals as it represents a multivariate environment with wide range of conditions including broad range of temperatures, pH, presence of bacteria and effect of abrasion. An increasing use of various Ti-based materials for dental implants and orthodontic brackets poses the question of their corrosion resistance in the presence of fluoride ions which are present in toothpaste and mouth rinse. Corrosion behaviour of Ti metal, Ti-6Al-7Nb and Ti-6Al-4V alloys and constituent metals investigated in artificial saliva is significantly affected by the presence of fluoride ions (added as NaF), as proven by electrochemical methods. Immersion test was performed for 32 days. During that time the metal dissolution was measured by inductively coupled plasma mass spectrometry. At the end of the test the composition, thickness and morphology of the surface layers formed were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy.

The black and white coatings on Ti-6Al-4V alloy or pure titanium by plasma electrolytic oxidation in concentrated silicate electrolyte

NASA Astrophysics Data System (ADS)

Han, Jun-xiang; Cheng, Yu-lin; Tu, Wen-bin; Zhan, Ting-Yan; Cheng, Ying-liang

2018-01-01

Black TiO2 has triggered scientific interest due to its unique properties such as enhanced solar-driven photocatalytic activity. In this paper, plasma electrolytic oxidation (PEO) treatment of Ti-6Al-4V alloy has been carried out in concentrated sodium silicate electrolyte. Silica-based black and white TiO2 coatings respectively have been obtained by controlling the oxidation time. The black coating, which was formed with a short treatment time, shows good corrosion resistance and the black appearance can be attributed to the presence of Ti2+ and Ti3+ in the coating. The lower valence titanium ions are absent in the white coatings and they also contain relatively higher Na content compared to the black coatings. The white coatings have great surface roughnesses and super hydrophilicity. The bonding strengths of the black and white coatings on the Ti-6Al-4V alloy are ∼14.4 and 4.3 MPa, respectively. The vanadium contributes little to the black appearance of the coating on Ti6Al4V alloy, since the same phenomena occur for the PEO of a pure titanium substrate.

Preliminary investigation of the kinetics of primary creep of a two phase gamma TiAl alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, R.W.

1993-11-01

It is the intent of this communication to present and discuss some data regarding the kinetics of primary creep of a two phase gamma TiAl alloy which had been studied previously to determine the mechanisms giving rise to the minimum strain rate. In order to study the kinetics of primary creep of the present gamma TiAl alloy an approach previously taken by Dorn et al and also recently employed by Argon and Bhattacharya was taken. Dorn et al demonstrated that at a given constant stress, the strain rate during primary creep is governed by a combined time-temperature parameter [Theta] =more » t exp([minus]Q/RT) where Q is the activation energy for self diffusion which many times also governs the process of steady-state creep. It was shown that at the same constant stress level all primary creep curves were found to collapse on one another when the primary creep strain is plotted as a function of [Theta][sup (9)].« less

Structural, morphological and interfacial characterization of Al-Mg/TiC composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contreras, A.; Angeles-Chavez, C.; Flores, O.

2007-08-15

Morphological and structural characterization of Al-Mg/TiC composites obtained by infiltration process and wetting by the sessile drop technique were studied. Focusing at the interface, wetting of TiC substrates by molten Al-Mg-alloys at 900 deg. C was investigated. Electron probe microanalysis (EPMA) indicated that aluminum carbide (Al{sub 4}C{sub 3}) is formed at the interface and traces of TiAl{sub 3} in the wetting assemblies were detected. Scanning Electron Microscopy (SEM) observations show that TiC particles do not appear to be uniformly attacked to produce a continuous layer of Al{sub 4}C{sub 3} at the interface. Molten Al-Mg-alloys were infiltrated into TiC preforms withmore » flowing argon at a temperature of 900 deg. C. In the composites no reaction phase was observed by SEM. Quantification of the Al phase in the composite was carried out by X-ray diffraction (XRD) and Rietveld analysis. Chemical mapping analyzed by SEM shows that the Al-Mg alloy surrounds TiC particles. In the composites with 20 wt.% of Mg the Al-Mg-{beta} phase was detected through XRD.« less

Alpha phase precipitation from phase-separated beta phase in a model Ti-Mo-Al alloy studied by direct coupling of transmission electron microscopy and atom probe tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devaraj, Arun; Nag, Soumya; Banerjee, Rajarshi

2013-10-19

The benefit of direct coupling of APT with TEM dark field imaging to investigate early stages of phase transformation in multicomponent alloys is demonstrated by analyzing alpha phase precipitated in a model Ti-10 at% Mo-10 at% Al alloy during annealing at 400oC. Through such a direct coupling approach a thermodynamically unexpected solute partitioning trend between beta matrix and alpha precipitate is observed in the early stages of precipitation, which is explained based on possible nucleation of alpha phase in the Ti rich (Mo and Al depleted regions) created as a result of phase separation in beta matrix. On further highermore » temperature annealing at 600oC for 1 hour, the alpha precipitates were shown to grow and get enriched in Al and further depleted in Mo reaching the thermodynamic equilibrium.« less

Effect of thermal oxidation on corrosion and corrosion-wear behaviour of a Ti-6Al-4V alloy.

PubMed

Güleryüz, Hasan; Cimenoğlu, Hüseyin

2004-07-01

In this study, comparative investigation of thermal oxidation treatment for Ti-6Al-4V was carried out to determine the optimum oxidation conditions for further evaluation of corrosion-wear performance. Characterization of modified surface layers was made by means of microscopic examinations, hardness measurements and X-ray diffraction analysis. Optimum oxidation condition was determined according to the results of accelerated corrosion tests made in 5m HCl solution The examined Ti-6Al-4V alloy exhibited excellent resistance to corrosion after oxidation at 600 degrees C for 60 h. This oxidation condition achieved 25 times higher wear resistance than the untreated alloy during reciprocating wear test conducted in a 0.9% NaCl solution.

Refining Mechanism of 7075 Al Alloy by In-Situ TiB₂ Particles.

PubMed

Gan, Guisheng; Yang, Bin; Zhang, Bo; Jiang, Xin; Shi, Yunlong; Wu, Yiping

2017-02-04

The nucleation undercooling of TiB₂/7075 Al matrix composites, the microstructure observed after solidification at different cooling rate, and the size and distribution of TiB₂ particles were investigated. The experimental results have shown that the grain sizes of TiB₂/7075 Al matrix composites firstly decreased, then increased, and finally decreased again with the increase of TiB₂ content. The nucleation undercooling of TiB₂/7075 Al matrix composites first increased, then decreased, and finally increased again with the increase of TiB₂ content when the cooling rates was 5 and 10 °C/min respectively, but kept decreasing with the increase of TiB₂ content at a cooling rate of 20 °C/min. The melting and solidification process showed no significant change with the decrease of cooling rate in 9.0% TiB₂/7075 Al matrix composites. Most small particles can act as heterogeneous nucleus, which induced grain growth and were captured into the grain by the solid/liquid interface. At the same time, most of the larger particles and a minority of the small TiB₂ particles are pushed into the grain boundary; locating in the grain boundary can hinder the Al atoms from diffusing during the solidification process and restrain α-Al phase growth. The influence of particles shifted from dominating by locating to dominating by nucleation as the quantity of TiB₂ particles increased.

Bone response to a novel Ti-Ta-Nb-Zr alloy.

PubMed

Stenlund, Patrik; Omar, Omar; Brohede, Ulrika; Norgren, Susanne; Norlindh, Birgitta; Johansson, Anna; Lausmaa, Jukka; Thomsen, Peter; Palmquist, Anders

2015-07-01

Commercially pure titanium (cp-Ti) is regarded as the state-of-the-art material for bone-anchored dental devices, whereas the mechanically stronger alloy (Ti-6Al-4V), made of titanium, aluminum (Al) and vanadium (V), is regarded as the material of choice for high-load applications. There is a call for the development of new alloys, not only to eliminate the potential toxic effect of Al and V but also to meet the challenges imposed on dental and maxillofacial reconstructive devices, for example. The present work evaluates a novel, dual-stage, acid-etched, Ti-Ta-Nb-Zr alloy implant, consisting of elements that create low toxicity, with the potential to promote osseointegration in vivo. The alloy implants (denoted Ti-Ta-Nb-Zr) were evaluated after 7 days and 28 days in a rat tibia model, with reference to commercially pure titanium grade 4 (denoted Ti). Analyses were performed with respect to removal torque, histomorphometry and gene expression. The Ti-Ta-Nb-Zr showed a significant increase in implant stability over time in contrast to the Ti. Further, the histological and gene expression analyses suggested faster healing around the Ti-Ta-Nb-Zr, as judged by the enhanced remodeling, and mineralization, of the early-formed woven bone and the multiple positive correlations between genes denoting inflammation, bone formation and remodeling. Based on the present experiments, it is concluded that the Ti-Ta-Nb-Zr alloy becomes osseointegrated to at least a similar degree to that of pure titanium implants. This alloy is therefore emerging as a novel implant material for clinical evaluation. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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.

Elastic moduli of cast Ti-Au, Ti-Ag, and Ti-Cu alloys.

PubMed

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2006-07-01

This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys. A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30 mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were determined with an ultrasonic-pulse method. The density of each alloy was previously measured by the Archimedes' principle. Results were analyzed using one-way ANOVA and the Scheffé's test. The densities of Ti-Au, Ti-Ag, and Ti-Cu alloys monotonically increased as the concentration of alloying elements increased. As the concentration of gold or silver increased to 20%, the Young's modulus significantly decreased, followed by a subsequent increase in value. As the concentration of copper increased, the Young's modulus monotonically increased. The Young's moduli of all the Ti-Cu alloys were significantly higher than that of the titanium. The density of all the experimental alloys was virtually independent of the alloy phases, while the Young's moduli and Poisson's ratios of the alloys were dependent. The addition of gold or silver slightly reduced the Young's modulus of the titanium when the alloy phase was single alpha. The increase in the Young's modulus of the Ti-Cu alloys is probably due to the precipitation of intermetallic compound Ti2Cu. Copper turned out to be a moderate stiffener that gains a Young's modulus of titanium up to 20% at the copper concentration of 30 mass%.

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

2016-09-13

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.

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

Effects of substrate microstructure on the formation of oriented oxide nanotube arrays on Ti and Ti alloys

NASA Astrophysics Data System (ADS)

Ferreira, C. P.; Gonçalves, M. C.; Caram, R.; Bertazzoli, R.; Rodrigues, C. A.

2013-11-01

The formation of nanotubular oxide layers on Ti and Ti alloys has been widely investigated for the photocatalytic degradation of organic compounds due to their excellent catalytic efficiency, chemical stability, and low cost and toxicity. Aiming to improve the photocatalytic efficiency of this nanostructured oxide, this work investigated the influence of substrate grain size on the growth of nanotubular oxide layers. Ti and Ti alloys (Ti-6Al, Ti-6Al-7Nb) were produced by arc melting with non-consumable tungsten electrode and water-cooled copper hearth under argon atmosphere. Some of the ingots were heat-treated at 1000 °C for 12 and 24 h in argon atmosphere, followed by slow cooling rates to reduce crystalline defects and increase the grain size of their microstructures. Three types of samples were anodized: commercial substrate, as-prepared and heat-treated samples. The anodization was performed using fluoride solution and a cell potential of 20 V. The samples were characterized by optical microscopy, field-emission scanning electron microscopy and X-ray diffraction. The heat treatment preceding the anodization process increased the grain size of pure Ti and Ti alloys and promoted the formation of Widmanstätten structures in Ti6Al7Nb. The nanotubes layers grown on smaller grain and thermally untreated samples were more regular and homogeneous. In the case of Ti-6Al-7Nb alloy, which presents a α + β phase microstructure, the morphology of nanotubes nucleated on α matrix was more regular than those of nanotubes nucleated on β phase. After the annealing process, the Ti-6Al-7Nb alloy presented full diffusion process and the growth of equilibrium phases resulting in the appearance of regions containing higher concentrations of Nb, i.e. beta phase. In those regions the dissolution rate of Nb2O5 is lower than that of TiO2, resulting in a nanoporous layer. In general, heat treating reduces crystalline defects and promotes the increasing of the grain sizes, not

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.

Surface properties of Ti-6Al-4V alloy part I: Surface roughness and apparent surface free energy.

PubMed

Yan, Yingdi; Chibowski, Emil; Szcześ, Aleksandra

2017-01-01

Titanium (Ti) and its alloys are the most often used implants material in dental treatment and orthopedics. Topography and wettability of its surface play important role in film formation, protein adhesion, following osseointegration and even duration of inserted implant. In this paper, we prepared Ti-6Al-4V alloy samples using different smoothing and polishing materials as well the air plasma treatment, on which contact angles of water, formamide and diiodomethane were measured. Then the apparent surface free energy was calculated using four different approaches (CAH, LWAB, O-W and Neumann's Equation of State). From LWAB approach the components of surface free energy were obtained, which shed more light on the wetting properties of samples surface. The surface roughness of the prepared samples was investigated with the help of optical profilometer and AFM. It was interesting whether the surface roughness affects the apparent surface free energy. It was found that both polar interactions the electron donor parameter of the energy and the work of water adhesion increased with decreasing roughness of the surfaces. Moreover, short time plasma treatment (1min) caused decrease in the surface hydrophilic character, while longer time (10min) treatment caused significant increase in the polar interactions and the work of water adhesion. Although Ti-6Al-4V alloy has been investigated many times, to our knowledge, so far no paper has been published in which surface roughness and changes in the surface free energy of the alloy were compared in the quantitative way in such large extent. This novel approach deliver better knowledge about the surface properties of differently smoothed and polished samples which may be helpful to facilitate cell adhesion, proliferation and mineralization. Therefore the results obtained present also potentially practical meaning. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of laser parameters in surface texturing of Ti6Al4V and AA2024-T3 alloys

NASA Astrophysics Data System (ADS)

Ahuir-Torres, J. I.; Arenas, M. A.; Perrie, W.; de Damborenea, J.

2018-04-01

Laser texturing can be used for surface modification of metallic alloys in order to improve their properties under service conditions. The generation of textures is determined by the relationship between the laser processing parameters and the physicochemical properties of the alloy to be modified. In the present work the basic mechanism of dimple generation is studied in two alloys of technological interest, titanium alloy Ti6Al4V and aluminium alloy AA2024-T3. Laser treatment was performed using a pulsed solid state Nd: Vanadate (Nd: YVO4) laser with a pulse duration of 10 ps, operating at a wavelength of 1064 nm and 5 kHz repetition rate. Dimpled surface geometries were generated through ultrafast laser ablation while varying pulse energy between 1 μJ and 20 μJ/pulse and with pulse numbers from 10 to 200 pulses per spot. In addition, the generation of Laser Induced Periodic Surface Structures (LIPSS) nanostructures in both alloys, as well as the formation of random nanostructures in the impact zones are discussed.

Effects of combined plasma chromizing and shot peening on the fatigue properties of a Ti6Al4V alloy

NASA Astrophysics Data System (ADS)

Yu, Shouming; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing

2015-10-01

A plasma chromizing treatment was conducted on Ti6Al4V samples by employing the recently developed double glow plasma surface alloying technology. The Cr-alloyed layer consisted of four sub-layers, namely the Cr deposition, Cr2Ti, CrTi4, and Cr-Ti solid-solution layers. The local hardness and moduli were determined via nanoindentation. In addition, the fatigue properties of the samples were evaluated by using a rotating-bending fatigue machine under a given load. The results showed that the hardness or elastic moduli of the adjacent sub-layers differed significantly and the fatigue properties of the Ti6Al4V alloy deteriorated with the plasma chromizing treatment. This deterioration stemmed mainly from cracks initiated at the interfaces between the sub-layers and the microstructural changes of the substrate; these changes were induced by the high temperature used in the plasma chromizing process. However, the fatigue life of the plasma-chromized samples was increased by a shot peening post-treatment. The fatigue life of the samples resulting from this combination of treatments was slightly higher than that of the single-shot-peened Ti6Al4V substrate. In fact, the sample retaining only the Cr-Ti solid-solution layer (that is, the first three sub-layers were removed), when shot-peened, exhibited the highest fatigue life among all the tested samples; this was attributed to that sample having the highest residual compressive stress, the significant work hardening, and the good hardness to toughness balance.

My Experience with Ti-Ni-Based and Ti-Based Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Miyazaki, Shuichi

2017-12-01

The present author has been studying shape memory alloys including Cu-Al-Ni, Ti-Ni-based, and Ni-free Ti-based alloys since 1979. This paper reviews the present author's research results for the latter two materials since 1981. The topics on the Ti-Ni-based alloys include the achievement of superelasticity in Ti-Ni alloys through understanding of the role of microstructures consisting of dislocations and precipitates, followed by the contribution to the development of application market of shape memory effect and superelasticity, characterization of the R-phase and monoclinic martensitic transformations, clarification of the basic characteristics of fatigue properties, development of sputter-deposited shape memory thin films and fabrication of prototypes of microactuators utilizing thin films, development of high temperature shape memory alloys, and so on. The topics of Ni-free Ti-based shape memory alloys include the characterization of the orthorhombic phase martensitic transformation and related shape memory effect and superelasticity, the effects of texture, omega phase and adding elements on the martensitic transformation and shape memory properties, clarification of the unique effects of oxygen addition to induce non-linear large elasticity, Invar effect and heating-induced martensitic transformation, and so on.

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. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of Plasma ZrN Metallurgy and Shot Peening Duplex Treatment on Fretting Wear and Fretting Fatigue Behavior of Ti6Al4V Alloy

PubMed Central

Tang, Jingang; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing; Yu, Shouming

2016-01-01

A metallurgical zirconium nitride (ZrN) layer was fabricated using glow metallurgy using nitriding with zirconiuming prior treatment of the Ti6Al4V alloy. The microstructure, composition and microhardness of the corresponding layer were studied. The influence of this treatment on fretting wear (FW) and fretting fatigue (FF) behavior of the Ti6Al4V alloy was studied. The composite layer consisted of an 8-μm-thick ZrN compound layer and a 50-μm-thick nitrogen-rich Zr–Ti solid solution layer. The surface microhardness of the composite layer is 1775 HK0.1. A gradient in cross-sectional microhardness distribution exists in the layer. The plasma ZrN metallurgical layer improves the FW resistance of the Ti6Al4V alloy, but reduces the base FF resistance. This occurs because the improvement in surface hardness results in lowering of the toughness and increasing in the notch sensitivity. Compared with shot peening treatment, plasma ZrN metallurgy and shot peening composite treatment improves the FW resistance and enhances the FF resistance of the Ti6Al4V alloy. This is attributed to the introduction of a compressive stress field. The combination of toughness, strength, FW resistance and fatigue resistance enhance the FF resistance for titanium alloy. PMID:28773345

Nanosized-Particle Dispersion-Strengthened Al Matrix Composites Fabricated by the Double Mechanical Alloying Process.

PubMed

Kim, Chungseok

2018-03-01

The objective of this study was to fabricate an Al metal matrix composite strengthened by nanosized Al3Ti particles via double mechanical alloying process. Several Al-xTi alloys were fabricated, including Al-12%Ti, Al-15%Ti, and Al-12%Ti-1%Y2O3. The lattice parameter of as-milled state was calculated to be 4.0485 Å; after a milling time of 540 min, it was 4.0401 Å. This decrease was induced by Ti solutionizing into the Al matrix. The equivalent size of a coarse Al3Ti particle was 200-500 nm after the heat treatment; however, the particles were uniformly distributed and were refined through the MA2 process. The particle size of a Al3Ti phase was 30 nm or less, and the particles were uniformly distributed. These particles remained in a fine state in the matrix without growth and coarsening, even after the hot extrusion process. The microstructure of hot extruded alloys consisted of a uniform distribution of Al3Ti particles and other dispersoids in the Al matrix.

Rapid Repairs: Surface Preparation of Ti-3 Al-2.5V Alloy Tubes by Fiber Laser and Welding

DTIC Science & Technology

2008-11-01

processing of titanium 6Al - 4V alloy for potential aerospace component cleaning application, Appl Surf Sci 2005;247:623-630. [11] Turner MW, Crouse...Debroy T, Heat transfer and fluid flow during keyhole mode laser welding of tantalum, Ti- 6Al - 4V , 304 Stainless Steel and Vanadium, J Phy D : Appl Phy...14Titanium alloys are used extensively in aerospace applications mainly due to their superior strength to weight ratio. Different grades of titanium

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys

PubMed Central

Song, Ho-Jun; Han, Mi-Kyung; Jeong, Hyeon-Gyeong; Lee, Yong-Tai; Park, Yeong-Joon

2014-01-01

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti. PMID:28788660

Plasma-Sprayed Ti6Al4V Alloy Composite Coatings Reinforced with In Situ Formed TiB-TiN

NASA Astrophysics Data System (ADS)

Anand, Akrity; Das, Mitun; Kundu, Biswanath; Balla, Vamsi Krishna; Bodhak, Subhadip; Gangadharan, S.

2017-12-01

Plasma spraying was used to deposit premixed Ti6Al4V + 15 wt.% BN powder on titanium substrate to fabricate Ti6Al4V matrix composite coatings reinforced with in situ synthesized TiB-TiN. The formation of in situ TiB-TiN reinforcements increased with plasma power. The in situ reaction appears to be complete under present experimental conditions but with considerable oxidation of Ti in the composite coatings. The hardness of composite coatings was 7 times higher (855HV), and the in vitro wear rate (2.4 × 10-5 mm3/N m) was one order of magnitude less than that of titanium substrate. However, the microstructural non-uniformity decreased the corrosion resistance of these composite coatings in Hank's balanced salt solution.

Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

NASA Astrophysics Data System (ADS)

Canulescu, S.; Borca, C. N.; Rechendorff, K.; Davidsdóttir, S.; Pagh Almtoft, K.; Nielsen, L. P.; Schou, J.

2016-04-01

The structural, optical, and transport properties of sputter-deposited Al-Ti thin films have been investigated as a function of Ti alloying with a concentration ranging from 2% to 46%. The optical reflectivity of Al-Ti films at visible and near-infrared wavelengths decreases with increasing Ti content. X-ray absorption fine structure measurements reveal that the atomic ordering around Ti atoms increases with increasing Ti content up to 20% and then decreases as a result of a transition from a polycrystalline to amorphous structure. The transport properties of the Al-Ti films are influenced by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as anti-site effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller than k allows us to explore the parameter space for the free-electron behavior in transition metal-Al alloys. The free electron model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to an optical reflectance at near infrared wavelengths that scales linearly with the square root of the electrical resistivity.

Enhanced fatigue performance of porous coated Ti6Al4V biomedical alloy

NASA Astrophysics Data System (ADS)

Apachitei, I.; Leoni, A.; Riemslag, A. C.; Fratila-Apachitei, L. E.; Duszczyk, J.

2011-05-01

Biofunctional coatings are necessary to improve integration of titanium implants in the host tissue but they may be detrimental for the implant fatigue properties. This study presents an attempt towards enhancement of the in vitro fatigue strength of plasma electrolytic oxidation coated Ti6Al4V alloy by applying shot peening process prior to coating. The electrolytic oxidation was performed in calcium acetate and calcium glycerophosphate electrolytes that allowed formation of porous oxide coatings with high surface free energy and apatite like ability. A deformed surface layer coupled with induced residual compressive stresses seem to affect oxide growth rate and fatigue behavior of the titanium alloy.

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.

Grindability of dental cast Ti-Ag and Ti-Cu alloys.

PubMed

Kikuchi, Masafumi; Takahashi, Masatoshi; Okabe, Toru; Okuno, Osamu

2003-06-01

Experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500 m min(-1)), there were no statistical differences among the grindability values of the titanium and titanium alloys. The grindability of the alloys increased as the grinding speed increased. At the highest grinding speed (1500 m x min(-1)), the grindability of the 20% Ag, 5% Cu, and 10% Cu alloys was significantly higher than that of titanium. It was found that alloying with silver or copper improved the grindability of titanium, particularly at a high speed. It appeared that the decrease in elongation caused by the precipitation of small amounts of intermetallic compounds primarily contributed to the favorable grindability of the experimental alloys.

The machinability of cast titanium and Ti-6Al-4V.

PubMed

Ohkubo, C; Watanabe, I; Ford, J P; Nakajima, H; Hosoi, T; Okabe, T

2000-02-01

This study investigated the machinability (ease of metal removal) of commercially pure (CP) titanium and Ti-6Al-4V alloy. Both CP Ti and Ti-6Al-4V were cast into magnesia molds. Two types of specimens (with alpha-case and without alpha-case) were made for CP Ti and Ti-6Al-4V. Machinability (n = 5) was evaluated as volume loss (mm3) by cutting/grinding the 3.0 mm surface using fissure burs and silicon carbide (SiC) under two machining conditions: (1) two machining forces (100 or 300 gf) at two rotational speeds (15000 or 30000 rpm) for 1 min, and (2) constant machining force of 100 gf and rotational speed of 15000 rpm for 1, 2, 5, 10, and 30 min. As controls, conventionally cast Co-Cr and Type IV gold alloys were evaluated in the same manner as the titanium. When fissure burs were used, there was a significant difference in the machinability between CP titanium with alpha-case and without alpha-case. On the other hand, there was no appreciable difference in the amount of metal removed for each tested metal when using the SiC points.

EFFECT OF PRE-ALLOYING CONDITION ON THE BULK AMORPHOUS ALLOY ND(60)FE(30)AL(10).

DOE Office of Scientific and Technical Information (OSTI.GOV)

OCONNOR,A.S.; LEWIS,L.H.; MCCALLUM,R.W.

Bulk metallic glasses are materials that require only modest cooling rates to obtain amorphous solids directly from the melt. Nd{sub 60}Fe{sub 30}Al{sub 10} has been reported to be a ferromagnetic bulk metallic glass that exhibits high coercivity, a combination unlike conventional Nd-based amorphous magnetic alloys. To clarify the relationship between short-range order and high coercivity in glassy Nd{sub 60}Fe{sub 30}Al{sub 10}, experiments were performed to verify the existence of a homogeneous liquid state prior to rapid solidification. Alloys were prepared by various pre-alloying routes and then melt-spun. Arc-melted alloys were prepared for melt spinning using three different protocols involving: (1)more » alloying all three elements at once, (2) forming a Nd-Fe alloy which was subsequently alloyed with Al, and (3) forming a Fe-Al alloy for subsequent alloying with Nd. XRD, DTA, and magnetic measurement data from the resultant ribbons indicate significant differences in both the glassy fraction and the crystalline phase present in the as-spun material. These observed differences are attributed to the presence of highly stable nanoscopic aluminide-and/or silicide-phases, or motes, present in the melt prior to solidification. These motes would affect the short-range order and coercivity of the resultant glassy state and are anticipated to provide heterogeneous nucleation sites for crystallization.« less

Corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloys in different storage environments.

PubMed

Zavanelli, R A; Pessanha Henriques, G E; Ferreira, I; De Almeida Rollo, J M

2000-09-01

Removable partial dentures are affected by fatigue because of the cyclic mechanism of the masticatory system and frequent insertion and removal. Titanium and its alloys have been used in the manufacture of denture frameworks; however, preventive agents with fluorides are thought to attack titanium alloy surfaces. This study evaluated, compared, and analyzed the corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloy in different storage environments. For each metal, 33 dumbbell rods, 2.3 mm in diameter at the central segment, were cast in the Rematitan system. Corrosion-fatigue strength test was carried out through a universal testing machine with a load 30% lower than the 0.2% offset yield strength and a combined influence of different environments: in air at room temperature, with synthetic saliva, and with fluoride synthetic saliva. After failure, the number of cycles were recorded, and fracture surfaces were examined with an SEM. ANOVA and Tukey's multiple comparison test indicated that Ti-6Al-4V alloy achieved 21,269 cycles (SD = 8,355) against 19,157 cycles (SD = 3, 624) for the commercially pure Ti. There were no significant differences between either metal in the corrosion-fatigue life for dry specimens, but when the solutions were present, the fatigue life was significantly reduced, probably because of the production of corrosion pits caused by superficial reactions.

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2009-01-01

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

Effect of Ti content on the microstructure and mechanical behavior of (Fe 36Ni 18Mn 33Al 13) 100–xTi x high entropy alloys

DOE PAGES

Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; ...

2016-06-13

The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe 36Ni 18Mn 33Al 13Ti x with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σ y, from 270 MPa to 953 MPa, but with a concomitant decrease inmore » ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe 36Ni 18Mn 33Al 13Ti 4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less

Effect of Ti content on the microstructure and mechanical behavior of (Fe 36Ni 18Mn 33Al 13) 100–xTi x high entropy alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou

The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe 36Ni 18Mn 33Al 13Ti x with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σ y, from 270 MPa to 953 MPa, but with a concomitant decrease inmore » ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe 36Ni 18Mn 33Al 13Ti 4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less

Manipulation of the osteoblast response to a Ti 6Al 4V titanium alloy using a high power diode laser

NASA Astrophysics Data System (ADS)

Hao, L.; Lawrence, J.; Li, L.

2005-07-01

To improve the bone integration of titanium-based implants a high power diode laser (HPDL) was used to modify the material for improved osteoblast cell response. The surface properties of un-treated and HPDL treated samples were characterized. Contact angles for the un-treated and the HPDL modified titanium alloy (Ti-6Al-4V) were determined with selected biological liquids by the sessile drop technique. The analysis revealed that the wettability of the Ti-6Al-4V improved after HPDL laser treatment, indicating that better interaction with the biological liquids occurred. Moreover, an in vitro human fetal osteoblast cells (hFOB 1.19) evaluation revealed a more favourable cell response on the HPDL laser treated Ti-6Al-4V alloy than on either un-treated sample or a mechanically roughened sample. It was consequently determined that the HPDL provides more a controllable and effective technique to improve the biocompatibility of bio-metals.

An Evaluation of a Borided Layer Formed on Ti-6Al-4V Alloy by Means of SMAT and Low-Temperature Boriding

PubMed Central

Yao, Quantong; Sun, Jian; Fu, Yuzhu; Tong, Weiping; Zhang, Hui

2016-01-01

In this paper, a nanocrystalline surface layer without impurities was fabricated on Ti-6Al-4V alloy by means of surface mechanical attrition treatment (SMAT). The grain size in the nanocrystalline layer is about 10 nm and grain morphology displays a random crystallographic orientation distribution. Subsequently, the low-temperature boriding behaviors (at 600 °C) of the SMAT sample, including the phase composition, microstructure, micro-hardness, and brittleness, were investigated in comparison with those of coarse-grained sample borided at 1100 °C. The results showed that the boriding kinetics could be significantly enhanced by SMAT, resulting in the formation of a nano-structured boride layers on Ti-6Al-4V alloy at lower temperature. Compared to the coarse-grained boriding sample, the SMAT boriding sample exhibits a similar hardness value, but improved surface toughness. The satisfactory surface toughness may be attributed to the boriding treatment that was carried out at lower temperature. PMID:28774115

In vitro assessments on bacterial adhesion and corrosion performance of TiN coating on Ti6Al4V titanium alloy synthesized by multi-arc ion plating

NASA Astrophysics Data System (ADS)

Lin, Naiming; Huang, Xiaobo; Zhang, Xiangyu; Fan, Ailan; Qin, Lin; Tang, Bin

2012-07-01

TiN coating was synthesized on Ti6Al4V titanium alloy surface by multi-arc ion plating (MIP) technique. Surface morphology, cross sectional microstructure, elemental distributions and phase compositions of the obtained coating were analyzed by means of scanning electron microscope (SEM), optical microscope (OM), glow discharge optical emission spectroscope (GDOES) and X-ray diffraction (XRD). Bacterial adhesion and corrosion performance of Ti6Al4V and the TiN coating were assessed via in vitro bacterial adhesion tests and corrosion experiments, respectively. The results indicated that continuous and compact coating which was built up by pure TiN with a typical columnar crystal structure has reached a thickness of 1.5 μm. This TiN coating could significantly reduce the bacterial adhesion and enhance the corrosion resistance of Ti6Al4V substrate.

Synthesis of Ti-6Al-4V alloy with nano-TiN microstructure via spark plasma sintering technique

NASA Astrophysics Data System (ADS)

E Falodun, O.; Obadele, B. A.; Oke, S. R.; E Maja, M.; Olubambi, P. A.

2017-12-01

The effect of nano-TiN dispersion strengthened Ti-6Al-4V via spark plasma sintering method has been investigated. Ti-6Al-4V with 4 vol. percent of nano-TiN were mixed in a Turbula shaker mixer for 8 h at a speed of 49 rpm and the admixed powders were sintered at sintering temperature range of 1000 - 1100 °C, holding time of 10-30 mins, heating rate of 100 °C/min under an applied pressure of 50 MPa. The morphology of the as-received and sintered compacts was examined by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and phase analysis was done by X-ray diffractometry (XRD). The sintered compacts without nano-TiN reveal lamellar structure while reinforced Ti-6Al-4V with nano-TiN shows a bimodal structure and titanium nitride has a great influence on a grain growth at high temperature. Furthermore, the microstructural formation mechanism was investigated. With the addition of the content of Ti-6Al-4V with 4 vol.% of nano-TiN, the micro-hardness also improved and this was due to homogenous distribution of TiN in Ti-6Al-4V matrix.

Machinability of experimental Ti-Ag alloys.

PubMed

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2008-03-01

This study investigated the machinability of experimental Ti-Ag alloys (5, 10, 20, and 30 mass% Ag) as a new dental titanium alloy candidate for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Machinability was evaluated through cutting force using a three-component force transducer fixed on the table of the milling machine. The horizontal cutting force of the Ti-Ag alloys tended to decrease as the concentration of silver increased. Values of the component of the horizontal cutting force perpendicular to the feed direction for Ti-20% Ag and Ti-30% Ag were more than 20% lower than those for titanium under both cutting conditions. Alloying with silver significantly improved the machinability of titanium in terms of cutting force under the present cutting conditions.

Preparation of Al-Si Master Alloy by Electrochemical Reduction of Fly Ash in Molten Salt

NASA Astrophysics Data System (ADS)

Liu, Aimin; Li, Liangxing; Xu, Junli; Shi, Zhongning; Hu, Xianwei; Gao, Bingliang; Wang, Zhaowen; Yu, Jiangyu; Chen, Gong

2014-05-01

An electrochemical method on preparation of Al-Si master alloy was investigated in fluoride-based molten salts of 47.7wt.%NaF-43.3wt.%AlF3-4wt.%CaF2 containing 5 wt.% fly ash at 1233 K. The cathodic products obtained by galvanostatic electrolysis were analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy, and energy-dispersive spectrometry. The result showed that the compositions of the products are Al, Si, and Al3.21Si0.47. Meanwhile, the cathodic electrochemical process was studied by cyclic voltammetry, and the results showed the reduction peak of aluminum deposition is at -1.3 V versus the platinum quasi-reference electrode in 50.3wt.%NaF-45.7wt.%AlF3-4wt.%CaF2 molten salts, while the reduction peak at -1.3 V was the co-deposition of aluminum and silicon when the fly ash was added. The silicon and iron were formed via both co-deposition and aluminothermic reduction. In the electrolysis experiments, current efficiency first increased to a maximum value of 40.7% at a current density of 0.29 A/cm2, and then it decreased with the increase of current density. With the electrolysis time lasting, the content of aluminum in the alloys decreased from 76.05 wt.% to 48.29 wt.% during 5 h, while the content of silicon increased from 15.94 wt.% to 37.89 wt.%.

Effect of Al–5Ti–C Master Alloy on the Microstructure and Mechanical Properties of Hypereutectic Al–20%Si Alloy

PubMed Central

Ding, Wanwu; Xia, Tiandong; Zhao, Wenjun; Xu, Yangtao

2014-01-01

Al–5Ti–C master alloy was prepared and used to modify hypereutectic Al–20%Si alloy. The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Al–5Ti–C master alloy additions (0, 0.4, 0.6, 1.0, 1.6 and 2.0 wt%) were investigated. The results show that, Al–5Ti–C master alloy (0.6 wt%, 10 min) can significantly refine both eutectic and primary Si of hypereutectic Al–20%Si alloy. The morphology of the primary Si crystals was significantly refined from a coarse polygonal and star-like shape to a fine polyhedral shape and the grain size of the primary Si was refined from roughly 90–120 μm to 20–50 μm. The eutectic Si phases were modified from a coarse platelet-like/needle-like structure to a fine fibrous structure with discrete particles. The Al–5Ti–C master alloy (0.6 wt%, 30 min) still has a good refinement effect. The ultimate tensile strength (UTS), elongation (El) and Brinell hardness (HB) of Al–20%Si alloy modified by the Al–5Ti–C master alloy (0.6 wt%, 10 min) increased by roughly 65%, 70% and 51%, respectively, due to decreasing the size and changing the morphology on the primary and eutectic Si crystals. The change in mechanical properties corresponds to evolution of the microstructure. PMID:28788509