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Sample records for al-si alloy reinforced

  1. Dendrite coherency of Al-Si-Cu alloys

    NASA Astrophysics Data System (ADS)

    Veldman, Natalia L. M.; Dahle, Arne K.; Stjohn, David H.; Arnberg, Lars

    2001-01-01

    The dendrite coherency point of Al-Si-Cu alloys was determined by thermal analysis and rheological measurement methods by performing parallel measurements at two cooling rates for aluminum alloys across a wide range of silicon and copper contents. Contrary to previous findings, the two methods yield significantly different values for the fraction solid at the dendrite coherency point. This disparity is greatest for alloys of low solute concentration. The results from this study also contradict previously reported trends in the effect of cooling rate on the dendritic coherency point. Consideration of the results shows that thermal analysis is not a valid technique for the measurement of coherency. Analysis of the results from rheological testing indicates that silicon concentration has a dominant effect on grain size and dendritic morphology, independent of cooling rate and copper content, and thus is the factor that determines the fraction solid at dendrite coherency for Al-Si-Cu alloys.

  2. Microstructure and wear resistance of Al-SiC composites coatings on ZE41 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Rodrigo, P.; Campo, M.; Torres, B.; Escalera, M. D.; Otero, E.; Rams, J.

    2009-08-01

    Al and Al-SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesium alloy substrates. Coatings with controlled reinforcement rate of up to 23 vol.% were obtained by spraying mixtures containing aluminium powder with up to 50 vol.% SiC particles. The coatings were sprayed on the magnesium alloy with minor degradation of its microstructure or mechanical properties. The coatings were compacted to improve their microstructure and protective behaviour. The wear behaviour of these coatings has been tested using the pin-on-disk technique and the reinforced coatings provided 85% more wear resistance than uncoated ZE41 and 400% more than pure Al coatings.

  3. Eutectic nucleation in hypoeutectic Al-Si alloys

    SciTech Connect

    Nafisi, S. Ghomashchi, R.; Vali, H.

    2008-10-15

    The nucleation mechanism of eutectic grains in hypoeutectic Al-Si foundry alloys has been investigated by examining deep etched specimens in high-resolution field emission gun scanning electron microscope (FEG-SEM) and by using in-situ Focused Ion Beam (FIB) milling and microscopy. Both unmodified and Sr-modified alloys were studied to characterize the nucleation mechanism of eutectic silicon flakes and fibers. It is proposed that following nucleation of eutectic Al on the primary {alpha}-Al dendrites, fine Si particles form at the solidification front upon which the eutectic Si flakes and fibers could develop. The formation of small Si particles is attributed to Si enrichment of the remaining melt due to the formation of eutectic Al (aluminum spikes) at the eutectic temperature. A hypothesis is then proposed to explain the mechanism of eutectic grains formation with main emphasis on the eutectic Si phase.

  4. Nucleation Effects in Thermally Managed Graphite Fiber-Reinforced Al-Cu and Al-Si Composites

    NASA Astrophysics Data System (ADS)

    Seong, H. G.; Lopez, H. F.; Gajdardziska-Josifovska, M.; Rohatgi, P. K.

    2007-11-01

    The influence of heat extraction through fiber reinforcements on the resultant solidification morphologies was investigated in cast Al-Cu and Al-Si alloy composites reinforced with graphite fibers (GRFs). For this purpose, the GRFs were externally cooled by exposing their ends to ambient air during pressure infiltration. It was found that in the Al-Cu system, heat extraction through the fiber ends promoted the development of single α-Al envelopes around the GRFs. In particular, radial growth of the α envelopes occurred with a planar solid/liquid solidification front as a result of heat extraction. Apparently, the high thermal conductivity of GRFs causes significant heat extraction to enable the development of a positive temperature gradient at the GRF/melt interface. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAD) unveiled the occurrence of (002) α-Al//(0002)GR orientation relationship at α-Al/GRF interfaces. Preferential nucleation of primary Si along the graphite surfaces of the GRF-reinforced Al-Si alloy composite was also promoted by external fiber heat extraction. However, in this case, numerous nucleation events along the fiber interfaces were common, as well as nucleation at active substrates within the constrained melt. Finally, differential thermal analysis (DTA) indicated that the onset temperatures for nucleation shift toward higher values (by 7 °C for the Al-Cu composite and 2 °C for the Al-Si composite) when compared with their corresponding matrix alloys.

  5. 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

    2016-06-01

    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.

  6. Performance improvement of vertical ultraviolet-LEDs with AlSi alloy substrates.

    PubMed

    Chen, Kung-Cheng; Huang, Shih-Yung; Wang, Wei-Kai; Horng, Ray-Hua

    2015-06-15

    A composite AlSi alloy substrate was fabricated to eliminate thermal expansion coefficient mismatch in high-power vertical light-emitting diodes (VLEDs). At 2000-mA injection current, the light output power performance of LED/sapphire, VLED/Si, and VLED/AlSi are 1458, 2465, and 2499 mW and the wall-plug efficiencies are 13.66%, 26.39%, and 28.02%, respectively. The enhanced performance is attributable to the lower tensile stress and series resistance in VLED/AlSi than in LED/sapphire. The surface temperature of LED/AlSi is almost identical to and lower than that of LED/Si and LED/sapphire, respectively. Raman spectroscopy confirms that the residual strain in GaN film bonding on the composite AlSi is lower than that on bulk sapphire. PMID:26193525

  7. Infiltration of Saffil alumina fiber with AlCu and AlSi alloys

    SciTech Connect

    Garbellini, O.; Morando, C.; Biloni, H.; Palacio, H. . Inst. de Fisica de Materiales)

    1999-06-18

    Currently there is a considerable scientific and technological interest in the composite materials, which a strong ceramic reinforcement is incorporated into a metal matrix (MMC) to tailor its properties for specific applications. Among the various techniques for fabricating MMC, the liquid metal infiltration process by means of a pressurized gas is an attractive fabrication route for near net shaped metal matrix composite and has been successfully used to fabricate Al, Mg and more recently, Ni and Ni aluminide matrix composites, which can be reinforced by SiC or Al[sub 2]O[sub 3] particles, whiskers, or short fibers. This paper describes the experimental technique used and presents an experimental investigation of the effects of the process parameters employed, such as the preform and melt temperatures, the volume fraction of fibers in the preform and the applied pressure upon the infiltration length of a chopped preform during a unidirectional infiltration aided by gas pressure casting. The experiments of the present work were conducted to provide kinetic data with a view to optimizing the selection of the process initial conditions for infiltration which have an effect on the infiltration length of the molten matrix alloy into a preform and it is a first step in investigating the correlation between the infiltration length (fluidity) of AlCuSi matrix alloys and the microstructure of the composites fabricated by pressure casting. For this purpose, this paper focuses on AlCu and AlSi matrix alloys reinforced by short-fibers [delta]-alumina SAFFIL. The experiments reported here were performed with the fibers initially at a temperature significantly below the metal melting point. This is the case of practical interest for the fabrication of many fiber-reinforced metal components.

  8. Fatigue characteristics and microcosmic mechanism of Al-Si-Mg alloys under multiaxial proportional loadings

    NASA Astrophysics Data System (ADS)

    Jiang, Xiao-Song; He, Guo-Qiu; Liu, Bing; Zhu, Zheng-Yu; Zhang, Wei-Hua

    2011-08-01

    With the increasing use of Al-Si-Mg alloys in the automotive industry, the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability. The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research. As low cycle fatigue life and material strengthening behavior are closely related, the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed. Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties. The fatigue life exhibits a stable behavior under multiaxial proportional loadings. The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy (TEM). The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles. Simultaneously, the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings. The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material, which is caused by multiaxial proportional loadings.

  9. Low Cost Al-Si Casting Alloy As In-Situ Composite for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

    A new aluminum-silicon (Al-Si) alloy has been successfully developed at NASA- Marshall Space Flight Center (MSFC) that has significant improvement in tensile and fatigue strength at elevated temperatures (500 F-700 F). The alloy offers a number of benefits such as light weight, high hardness, low thermal expansion and high surface wear resistance. In hypereutectic form, this alloy is considered as an in-situ Al-Si composite with tensile strength of about 90% higher than the auto industry 390 alloy at 600 F. This composite is very economically produced by using either conventional permanent steel molds or die casting. The projected material cost is less than $0.90 per pound, and automotive components such as pistons can be cast for high production rate using conventional casting techniques with a low and fully accounted cost. Key Words: Metal matrix composites, In-situ composite, aluminum-silicon alloy, hypereutectic alloy, permanent mold casting, die casting.

  10. Tensile properties influencing variables in eutectic Al-Si casting alloys

    SciTech Connect

    Hafiz, M.F. . Dept. of Mechanical Engineering); Kobayashi, Toshiro . Dept. of Production Systems Engineering)

    1994-09-15

    Efforts to identify and characterize the physical properties of aluminum castings alloys are envisaged to lead to a new guideline from which the mechanical behavior of these alloys can be accurately predicted. For aluminum-silicon (Al-Si) casting alloys the tensile properties of a specific composition are observed to vary depending on the production parameters. The difference in the tensile properties appears to be mainly due to the microstructural features concomitant with the imposed production parameters. The present study aims to identify, quantitatively, the tensile properties influencing variables in high purity eutectic Al-Si casting alloy produced under a variety of solidification cooling rate with different strontium (Sr) additions, as a modifying agent. The correlation between the fracture characteristics and the microstructures has also been investigated.

  11. Recycling of aluminium scrap for secondary Al-Si alloys.

    PubMed

    Velasco, Eulogio; Nino, Jose

    2011-07-01

    An increasing amount of recycled aluminium is going into the production of aluminium alloy used for automotive applications. In these applications, it is necessary to control and remove alloy impurities and inclusions. Cleaning and fluxing processes are widely used during processing of the alloys for removal of inclusions, hydrogen and excess of magnesium. These processes use salt fluxes based in the system NaCl-KCl, injection of chlorine or mixture of chlorine with an inert gas. The new systems include a graphite wand and a circulation device to force convection in the melt and permit the bubbling and dispersion of reactive and cleaning agents. This paper discusses the recycling of aluminium alloys in rotary and reverberatory industrial furnaces. It focuses on the removal of magnesium during the melting process. In rotary furnaces, the magnesium lost is mainly due to the oxidation process at high temperatures. The magnesium removal is carried out by the reaction between chlorine and magnesium, with its efficiency associated to kinetic factors such as concentration of magnesium, mixing, and temperature. These factors are also related to emissions generated during the demagging process. Improvements in the metallic yield can be reached in rotary furnaces if the process starts with a proper salt, with limits of addition, and avoiding long holding times. To improve throughput in reverberatories, start the charging with high magnesium content material and inject chlorine gas if the molten metal is at the right temperature. Removal of magnesium through modern technologies can be efficiently performed to prevent environmental problems. PMID:20837560

  12. Quantification of Microsegregation in Cast Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Ganesan, M.; Thuinet, L.; Dye, D.; Lee, P. D.

    2007-08-01

    The random sampling approach offers an elegant yet accurate way of validating microsegregation models. However, both instrumental errors and interference from secondary phases complicate the treatment of randomly sampled microprobe data. This study demonstrates that the normal procedure of sorting the data for each element independently can lead to inaccurate estimation of segregation profiles within multicomponent, multiphase, aluminum alloys. A recently proposed alloy-independent approach is shown to more reliably isolate these interferences, allowing more accurate validation of microsegregation models. Application of this approach to examine solidification segregation of a 319-type alloy demonstrated that, for these slowly cooled castings, neither Sr or TiB2 additions significantly affected coring of Cu within the primary α-Al dendrites. Comparison against predictions of CALPHAD-type Gulliver-Scheil models was less satisfactory. Consideration of back-diffusion and morphology effects through a one-dimensional (1-D) numerical model do not improve the agreement. Possible reasons for the lack of agreement are hypothesized.

  13. Brazeability of a 3003 Aluminum alloy with Al-Si-Cu-based filler metals

    NASA Astrophysics Data System (ADS)

    Tsao, L. C.; Weng, W. P.; Cheng, M. D.; Tsao, C. W.; Chuang, T. H.

    2002-08-01

    Al-Si-Cu-based filler metals have been used successfully for brazing 6061 aluminum alloy as reported in the authors’ previous studies. For application in heat exchangers during manufacturing, the brazeability of 3003 aluminum alloy with these filler metals is herein further evaluated. Experimental results show that even at such a low temperature as 550 °C, the 3003 alloys can be brazed with the Al-Si-Cu fillers and display bonding strengths that are higher than 77 MPa as well. An optimized 3003 joint is attained in the brazements with the innovative Al-7Si-20Cu-2Sn-1Mg filler metal at 575 °C for 30 min, which reveals a bonding strength capping the 3003 Al matrix.

  14. Microstructural Characteristic and Mechanical Behavior of Nodular Silicon Hypereutectic Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Ruyao; Lu, Weihua

    2012-02-01

    The microstructure and mechanical properties of Al-Si-Cu-Mg alloys containing 12 wt.% to 30 wt.% Si are discussed. The eutectic and primary silicon particles are nodulized by a designed modification practice followed by a solution heat treatment of 6 h to 8 h at 510°C to 520°C. Metallographic analysis was used to measure structural characteristics of the Si-rich structures. Spheroidization of silicon phase leads to an increase in tensile strength and ductility of alloys at room temperature and 300°C compared with commercial Al-Si alloy. Increasing Si concentration causes the ultimate tensile strength and elongation at room temperature to fall due to the appearance of coarse silicon particles, but the ultimate tensile strength at 300°C remains unchanged.

  15. Hypereutectic AlSi Alloy: Gathering of 3D Microstructure Data

    NASA Astrophysics Data System (ADS)

    Schaberger-Zimmermann, E.; Mathes, M.; Zimmermann, G.

    2016-06-01

    Hypereutectic and eutectic AlSi-base alloys find frequent application in casting automotive components. The properties of this type of alloy depend significantly on their solidification microstructure, especially the size, shape, and distribution of primary and eutectic silicon. The serial sectioning technique was applied for determining the three-dimensional (3D) microstructure of an Al-18wt.%Si alloy. For clear identification of both the larger primary Si particles grown in the melt and the fine lamellar eutectic Si, a series of two-dimensional equidistant cross sections were metallographically prepared. The microstructure in these cross sections was detected and observed at high resolution using a light microscope. The images were stored in a digital library. The 3D reconstruction of primary Si particles and AlSi eutectic was achieved through the application of various software tools. This provided data about the faceted growth behavior of octahedral Si particles and feathery eutectic Si. The image stack was also imported to hierarchical data format (version 5) (HDF5) open source format, thus, enabling availability of the 3D image data to the wider community. In this way, 3D reconstructions of this kind can contribute to a greater understanding of processing/microstructure property relationships in hypereutectic AlSi alloys.

  16. Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys

    SciTech Connect

    Hosch, Timothy

    2010-01-01

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  17. Effect of Silicon on the Thixoformability of Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Benati, Davi Munhoz; Zoqui, Eugênio José

    2014-09-01

    The thixoformability of new Al-Si-Cu alloys was evaluated and characterized by their microstructural and rheological behavior. Alloys Al1Si2.6Cu, Al2Si2.6Cu, Al4Si2.6Cu, and Al7Si2.6Cu were produced with the addition of Al5Ti1B grain refiner alloy. The materials were heat treated under two controlled conditions: holding times of 0, 30, 90, and 210 s and solid fraction of 45 and 60%. The evaluation of the microstructure and semisolid behavior was characterized by globule size, shape factor (SF), minimum stress to flow, maximum stress, and apparent viscosity. The heat treatment times promoted the globularization of solid phase particles to achieve better apparent viscosity results for the alloys treated for 210 s. Both 45 and 60% solid fraction showed no significant differences in terms of SF, but the alloys containing lower solid fraction showed better performance for apparent viscosity. Better working ranges for these new Al-Si-Cu alloys were determined reaching average strain of 0.5 MPa and apparent viscosity of 105 Pa s.

  18. Effect of Reinforcement on Sliding Wear Behaviors of Hypereutectic Al-Si Composites Prepared by Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Park, Seul-Ki; Choi, Jin-Myung; Kim, Yong-Jin; Park, Ik-Min; Park, Yong-Ho

    In this study, the effect of the reinforcement on the wear behavior of hypereutectic Al-Si composites was investigated by performing a ball-on-disk test. The specimens were manufactured by hot press after gas atomizing. Al-20Si-5TiC composite exhibited superior wear resistance than other composites used in this study.

  19. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  20. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Asmael, M. B. A.

    2016-05-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  1. The influence of Cu, Mg and Ni on the solidification and microstructure of Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Darlapudi, A.; McDonald, S. D.; StJohn, D. H.

    2016-03-01

    The influence of alloying elements (Cu, Mg, and Ni) on eutectic nucleation, eutectic grain morphology and the final microstructure of an Al-10Si commercial purity alloy in unmodified and Sr-modified conditions was investigated. It was found that the nucleation and eutectic grain growth morphologies of both the unmodified and Sr-modified Al-Si eutectic were significantly influenced by the addition of ternary alloying elements to a degree dependent on when the intermetallic phase formed during the solidification of the alloy with respect to the Al-Si eutectic. In cases where an intermetallic phase nucleated prior to the onset of the Al-Si eutectic reaction, the eutectic nucleation frequency was affected by changes to the available nuclei population. In cases where the intermetallic nucleated after the Al-Si eutectic, segregation of the ternary solutes in front of the Al-Si eutectic interface changed the nucleation and macroscopic growth dynamics. The changes in nucleation and growth dynamics of the Al-Si eutectic due to the presence of solute altered the morphology of the eutectic silicon considerably. This study has revealed a number of insights into the mechanisms of nucleation and growth of the Al-Si eutectic.

  2. Microstructure and Wear Behavior of Solidification Sonoprocessed B390 Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Khalifa, Waleed; El-Hadad, Shimaa; Tsunekawa, Yoshiki

    2013-12-01

    The hypereutectic Al-Si alloys constitute an important family of alloys because of their excellent wear resistance and low thermal expansion. However, the optimal microstructure and hence the optimal service performance of these alloys cannot be achieved by the conventional melt treatments used in industry today, because of the chemical incompatibility between the primary-Si refiners and the eutectic-Si modifiers used in microstructure control. The current study aimed at using ultrasonic vibrations to improve the microstructure and the properties of these alloys. The results of the current study showed that for the B390 Al-Si alloy (i) the ultrasonic treatment has potential refining effect on the primary Si and Fe intermetallic phases, (ii) the primary Si particles become finer as the pouring temperature decreases from 1033 K (760 °C) to 938 K (665 °C), (iii) pouring and ultrasonic treatment at temperatures below the start of primary Si precipitation result in the coexistence of large and fine Si particles in microstructure, (iv) phosphorous additions of 50 ppm did not show any substantial effect in the ultrasonically treated ingots, (v) ultrasonic-treated samples have uniform hardness over the surface while the untreated samples show large scattering (high standard deviation) in hardness levels and (vi) ultrasonic-treated samples showed better wear resistance in the absence of phosphorous.

  3. An Investigation on Axial Deformation Behavior of Thin-Wall Unfilled and Filled Tube with Aluminum Alloy (Al-Si7Mg) Foam Reinforced with SiC Particles

    NASA Astrophysics Data System (ADS)

    Kumaraswamidhas, L. A.; Rajak, Dipen Kumar; Das, S.

    2016-06-01

    The objective of this research is to produce superior quality aluminum alloy foam with low relative density and higher resistance against compression deformation. This investigation has studied crash energy capacities of unfilled and filled aluminum alloy foams in mild steel tubes. The foam has been prepared by the melt route process with an addition of 5wt.% silicon carbide particles. The fabricated aluminum alloy foams were characterized by field emission scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and Material Pro analyzer. It was observed that the foam-filled tubes could absorb more energy as compared to the unfilled tubes before reaching the complete densification point. Also, the aluminum alloy foams had better energy absorption capacity during the crash or impact loading. This article demonstrates the excellent ability of aluminum alloy foam application in the field where there is a need to absorb crash energy. It is to be noted that the amount of energy absorption will be greater for low-density foam filled in thin-wall rectangular section tubes. We have seen an increasing trend in the application of aluminum foams inside the thin-wall mild steel tubes for maximum energy absorption.

  4. The structure-property relationships of powder processed Fe-Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Prichard, Paul Dehnhardt

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape PN processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic%). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (Dsb{84} < 32μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 mum. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 mum to 104 mum. Mechanical property testing was conducted on both extruded and sintered material using small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25sp°C to 550sp°C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase alpha + DOsb3 structure. The extruded material developed higher yield strength at temperatures below the DBTT, but the sintered material developed higher strengths above the DBTT. The fracture energy of these

  5. Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility

    NASA Astrophysics Data System (ADS)

    Bösch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Göken, Mathias; Höppel, Heinz Werner

    2015-03-01

    Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed α-Al15(Fe,Mn)3Si2 phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the α-Al15(Fe,Mn)3Si2 phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys.

  6. Influence of SiC reinforcement particles on the tribocorrosion behaviour of Al-SiCp FGMs in 0.05M NaCl solution

    NASA Astrophysics Data System (ADS)

    Vieira, A. C.; Rocha, L. A.; Mischler, S.

    2011-05-01

    The main aim of this work was to study and understand the influence of SiC particles on the corrosion and tribocorrosion of Al-matrix composite materials. For that, Al-SiCp functionally graded composites were produced by centrifugal casting and different SiCp contents were achieved. Their mechanical properties were improved by age-hardening heat treatments. The tribocorrosion behaviour was studied in 0.05M NaCl solutions using a reciprocating motion tribometer involving an alumina ball sliding against the Al-based samples. Above critical SiC particles' content the matrix alloy surface was found to be protected against wear by SiC particles protruding from the surface. Below this threshold content, the SiC reinforcement was inefficient and the wear rate of the composite was the same as the non-reinforced alloy.

  7. Heterogeneous Nb-Based Nuclei for the Grain Refinement of Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Bolzoni, L.; Hari Babu, N.

    2016-05-01

    Nb-based intermetallics are, generally, low-density high-temperature materials used for structural applications or cryogenic superconductors. In this work, we report the development of an Al(96)-Nb(2)-B(2) master alloy where in situ-formed micrometric Nb-based intermetallics (i.e. NbB2 and Al3Nb) are used for a completely different purpose: to promote the refinement of Al-Si alloys by taking advantage of enhanced heterogeneous nucleation. Nb-based intermetallics have the right characteristics, like low density, stability at high temperature and good lattice match, to be used as heterogeneous nucleation substrates. It was found that the addition of these Nb-based intermetallics permits the significant refinement of the microstructural features of the Al-Si alloy studied. The enhanced heterogeneous nucleation makes the grain size of the material far less dependent on the cooling rate, which is one of the critical parameters influencing the variation of the properties of the alloy.

  8. Reliability and microstructure of Al-Si-V-Pd alloy films for use in ultralarge scale integration

    NASA Astrophysics Data System (ADS)

    Dirks, A. G.; Augur, R. A.

    1994-02-01

    New data on a highly reliable interconnect material based on aluminum will be presented. As compared with conventional Al-Si-Cu alloy films, quaternary Al-Si-V-Pd films with only 0.1 at. % vanadium and 0.1 at. % palladium combine excellent plasma etchability with good corrosion resistance. Electromigration tests of Al-Si-V-Pd films have shown a surprisingly high stability at 180 °C. Studies of microstructural attributes show: (a) for Al-Si-V-Pd relative to Al-Si, texture is not significantly changed and average grain size is slightly increased, and (b) the dominant factor leading to a highly stable microstructure is the combined presence of finely dispersed, small precipitates of both (Al,V) and (Al,Pd) phases.

  9. The structure-property relationships of powder processed Fe-Al-Si alloys

    SciTech Connect

    Prichard, P.D.

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D{sub 84} < 32 {micro}m). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 {micro}m. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 {micro}m to 104 {micro}m. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase {alpha} + DO{sub 3} structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  10. Thermodynamics calculation of reactions between phosphorus and main elements in Al-Si-Cu alloys

    NASA Astrophysics Data System (ADS)

    Li, Wangxing; Zhang, Ying; Yi, Danqing; Kong, Fanxiao; Chen, Xingyu

    2011-05-01

    The Gibbs free energy was calculated between phosphorus and the main elements in Al-Si-Cu alloys sampled as A390 to study the reaction process and give theoretical directions for the adding of phosphorus in industry. The results show that the elements such as aluminum, silicon, and copper have the capabilities to react with phosphorus according to the preference of Al, Cu, Si. As temperature increases, the reactions between phosphorus and the elements become more difficult. If aluminum is in existence, the phosphides of other elements will transform to aluminum phosphide.

  11. Evaluating Primary Dendrite Trunk Diameters in Directionally Solidified Al-Si Alloys

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2014-01-01

    The primary dendrite trunk diameters of Al-Si alloys that were directionally solidified over a range of processing conditions have been measured. These data are analyzed with a model based primarily on an assessment of secondary dendrite arm dissolution in the mushy zone. Good fit with the experimental data is seen and it is suggested that the primary dendrite trunk diameter is a useful metric that correlates well with the actual solidification processing parameters. These results are placed in context with the limited results from the aluminium - 7 wt. % silicon samples directionally solidified aboard the International Space Station as part of the MICAST project.

  12. Effect of Phosphorous Inoculation on Creep Behavior of a Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Faraji, Masoumeh; Khalilpour, Hamid

    2014-10-01

    Creep behavior of Al-Si hypereutectic alloys inoculated with phosphorus was investigated using the impression creep testing. The results showed that at stress regimes of up to 400-450 MPa and temperatures up to 300 °C, no significant creep deformation occurred in both uninoculated and inoculated specimens; however, at temperatures above 300 °C, the inoculated alloys presented better creep properties. Creep data were used to calculate the stress exponent of steady-state creep rate, n, and creep activation energy, Q, for different additive conditions where n was found varied between 5 and 8. Owing to the fact that most alloys have lower values for n (4, 5), threshold stress was estimated for studied conditions. The creep governing mechanisms for different conditions are discussed here, with a particular attention to the effect of phosphorous addition on the microstructural features, including number of primary silicon particles, mean primary silicon spacing, and morphology and distribution of eutectic silicon.

  13. The roles of Eu during the growth of eutectic Si in Al-Si alloys

    PubMed Central

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-01-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si. PMID:26328541

  14. The roles of Eu during the growth of eutectic Si in Al-Si alloys.

    PubMed

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-01-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si. PMID:26328541

  15. The roles of Eu during the growth of eutectic Si in Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Li, Jiehua; Hage, Fredrik; Wiessner, Manfred; Romaner, Lorenz; Scheiber, Daniel; Sartory, Bernhard; Ramasse, Quentin; Schumacher, Peter

    2015-09-01

    Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si.

  16. Experimental and Theoretical Investigations of the Solidification of Eutectic Al-Si Alloy

    NASA Technical Reports Server (NTRS)

    Sen, S.; Catalina, A. V.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    The eutectic alloys have a wide spectrum of applications due to their good castability and physical and mechanical properties. The interphase spacing resulting during solidification is an important microstructural feature that significantly influences the mechanical behavior of the material. Thus, knowledge of the evolution of the interphase spacing during solidification is necessary in order to properly design the solidification process and optimize the material properties. While the growth of regular eutectics is rather well understood, the irregular eutectics such as Al-Si or Fe-graphite exhibit undercoolings and lamellar spacings much larger than those theoretically predicted. Despite of a considerable amount of experimental and theoretical work a clear understanding of the true mechanism underlying the spacing selection in irregular eutectics is yet to be achieved. A new experimental study of the solidification of the eutectic Al-Si alloy will be reported in this paper. The measured interface undercoolings and lamellar spacing will be compared to those found in the literature in order to get more general information regarding the growth mechanism of irregular eutectics. A modification of the present theory of the eutectic growth is also proposed. The results of the modified mathematical model, accounting for a non-isothermal solid/liquid interface, will be compared to the experimental measurements.

  17. Spheroidization of Eutectic Silicon in Direct-Electrolytic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Ruyao; Lu, Weihua

    2013-06-01

    The spheroidization process of direct-electrolytic Al-Si alloy (DEASA) containing Si content in the range of 7 to 12 pct heated at temperatures of 778 K to 803 K (505 °C to 530 °C) was studied. The width, length, and aspect ratio of Si particles were measured to quantitatively analyze the microstructural variety of Si phase during the heating process in terms of chemical composition and remelting. Compared to existing Al-Si alloy, the lower soaking temperature of 778 K to 783 K (505 °C to 510 °C) is required to obtain the full spheroidization of the Si phase of DEASA. When remelting DEASA, a satisfactory granulation rate can be achieved at a higher soak temperature of 788 K to 803 K (515 °C to 530 °C). The origin of the high spheroidizaton rate is attributed to the microstructural characteristic relative to the electrolysis process. It would be expected that high crystallographic defects of Si grain result in the complete spheroidization of Si phase at lower temperatures for a short period.

  18. Experimental study on directional solidification of Al-Si alloys under the influence of electric currents

    NASA Astrophysics Data System (ADS)

    Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.

    2016-07-01

    The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.

  19. Effect of boron on the microstructure of near-eutectic Al-Si alloys

    SciTech Connect

    Wu Yuying . E-mail: wyy532001@163.com; Liu Xiangfa; Bian Xiufang

    2007-02-15

    The effect of boron on the microstructure of a near-eutectic Al-Si alloy (ZL109) was investigated by scanning electron microscopy (SEM) and electron beam microprobe analysis (EPMA). It was found that {alpha}-Al dendrites and eutectic clusters were significantly refined by the addition of boron. Another interesting discovery is that the near-eutectic alloy exhibited hypereutectic structure characteristics when the level of boron added exceeds 0.3%, i.e., primary Si is precipitated in the eutectic microstructure. A new type of nucleation substrate for the primary Si is found, Al {sub x}Ca {sub m}B {sub n}Si. This appears to be the main reason for the precipitation of primary Si.

  20. Annealing texture of a cold-rolled Fe-Mn-Al-Si-C alloy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Basudev; Ray, Ranjit Kumar

    2015-09-01

    The study of recrystallization texture of a cold deformed Fe-Mn-Al-Si-C alloy, with about 30% Mn, has been discussed in this paper. The alloy is fully austenitic at room temperature, and therefore, principal FCC rolling textures were developed in this material at different stages of cold rolling. The present study was undertaken to observe the transformation of FCC rolling texture during recrystallization of a heavily cold deformed specimen. It was observed that isothermal annealing at 750 °C led to a weak recrystallisation texture, which was quite similar to the deformation texture developed at the early stage of cold rolling. During recovery stage, a strong Bs/Goss-type texture was developed, which was identified as a new observation in this work.

  1. Coherency strains and coarsening in Ni-Al-Si alloys: An experimental study

    SciTech Connect

    Muralidharan, G. |; Epperson, J.E.; Petri, M.; Chen, H.

    1994-07-01

    Coarsening rates have been measured in a series of alloys in the ternary Ni-Al-Si system using in-situ Small Angle Neutron Scattering, the alloys having a constant Ni content and their Si content varying from 4.0 at. % to 11.0 at. %. Using expressions available in the literature for describing coarsening in multi-component systems, it is shown that it is possible to account for the variation in coarsening rates due to chemical effects. It is observed that the quality of the fit is improved if the composition dependence of the diffusion coefficient is considered in the analysis. Finally, the possible contribution of coherence strains to the measured coarsening rates is discussed.

  2. Modification Performance of WC Nanoparticles in Aluminum and an Al-Si Casting Alloy

    NASA Astrophysics Data System (ADS)

    Borodianskiy, Konstantin; Zinigrad, Michael

    2016-04-01

    The influence of a modifier based on tungsten carbide (WC) nanoparticles is investigated first using 1 kg of bulk aluminum and then in a real industrial process using a commercial Al-Si casting alloy. The modifier is prepared by two different approaches, and its influence is investigated in pure aluminum and in commercial aluminum alloy A356. Microstructural studies show that the mean grain size in pure aluminum is reduced by 11.5 pct. Such a change usually causes an improvement in the mechanical properties of metals. Accordingly, the mechanical properties of the A356 alloy modified with WC nanoparticles are determined after T6 heat treatment and compared with unmodified specimens of the same alloy. The results obtained in the modified A356 alloy reveal unusual behavior of the mechanical properties, where the elongation of the alloys improved by 32 to 64 pct, while the tensile strength and yield strength remained unchanged. This behavior is attributable to a grain-size strengthening mechanism, where strengthening occurs due to the high concentration of grain boundaries, which act as obstacles to the motion of dislocations in the lattice.

  3. Dissolution of iron intermetallics in Al-Si alloys through nonequilibrium heat treatment

    SciTech Connect

    Anantha Narayanan, L. |; Samuel, F.H.; Gruzleski, J.E.

    1995-08-01

    Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-1Fe alloys is found to be between 515 C and 520 C.

  4. Numerical Simulation Microstructure Morphology Evolution and Solute Microsegregation of Al-Si-Cu Ternary Alloys during Solidification Process

    NASA Astrophysics Data System (ADS)

    Xie, Shuisheng; Huang, Guojie; Cheng, Lei; Fu, Yao; Li, Qiang

    2011-06-01

    A 2D microstructure and solute microsegregation model of Al-Si-Cu ternary alloys is presented by using cellular automaton(CA) method. In CA model, an improved algorithm was presented that abandoned the assumption of solid/liquid interface position and velocity so as to calculate the solid fraction in the solid/liquid interface unit. Then, using CA model, a dendrite of Al-Si-Cu ternary alloys is simulated. Finally, solidification microstructure and solute microsegregation are simulated, and the simulated results can reflect the microstructure and different solute microsegregation during solidification process.

  5. The influence of ternary alloying elements on the Al-Si eutectic microstructure and the Si morphology

    NASA Astrophysics Data System (ADS)

    Darlapudi, A.; McDonald, S. D.; Terzi, S.; Prasad, A.; Felberbaum, M.; StJohn, D. H.

    2016-01-01

    The influence of the ternary alloying elements Cu, Mg and Fe on the Al-Si eutectic microstructure is investigated using a commercial purity Al-10 wt%Si alloy in unmodified and Sr-modified conditions. A change in the Al-Si eutectic microstructure was associated with a change in the nucleation density of the eutectic grains caused by the addition of ternary alloying elements. When the ternary alloying element addition resulted in an increase in the eutectic nucleation frequency, a fibrous to flake-like transition was observed within the eutectic grain. When the ternary alloying element addition decreased the eutectic nucleation frequency significantly, a change in the eutectic morphology from flake-like to a mixture of flake-like and fibrous morphologies was observed. The mechanism of Al-Si eutectic modification is discussed. The growth velocity of the eutectic grain - liquid interface and the constitutional driving force available for growth are proposed as important parameters that influence the degree of eutectic modification in Al-Si alloys.

  6. Positron annihilation study on the effect of Si-content on the recovery of deformed cast Al-Si alloys

    NASA Astrophysics Data System (ADS)

    El-Gamal, S.

    2013-09-01

    Isochronal annealing of Al-1100 and cast Al-Si alloys (Si-content 2, 4, 6 and 8 wt%) after deformation of 66% thickness reduction was investigated between room temperature (RT) and 500 °C. The annealing of defects was studied using Doppler Broadening Spectroscopy (DBS), Total Strain (εT) and Scanning Electron Microscope (SEM). It was found that; (i) three annealing stages of microstructure have been identified for Al-1100 and Al-Si alloys which are related to recovery, partial recrystallization and complete recrystallization (ii) the interaction between Si-precipitates and dislocations in Al-Si alloys leads to higher values of normalized line shape parameter (Snor) and lower values of εT than those for Al-1100 alloy also, it retarded the recovery and recrystallization with temperature (iii) the S-W plot revealed the presence of one type of defects in Al-1100 alloy but in Al-Si alloys the slope of the trajectory changes, which may indicate the occurrence of another defect type (Si-dislocation interaction) (iv) a negative correlation is observed between εT and Snor while a positive correlation between εT and normalized wing parameter (Wnor) is obvious.

  7. Microstructure analysis of Al-Si-Cu alloys prepared by gradient solidification technique

    NASA Astrophysics Data System (ADS)

    Borkar, Hemant; Seifeddine, Salem; Jarfors, Anders E. W.

    2015-03-01

    Al-Si-Cu alloys were cast with the unique gradient solidification technique to produce alloys with two cooling rates corresponding to secondary dendrite arm spacing (SDAS) of 9 and 27 μm covering the microstructural fineness of common die cast components. The microstructure was studied with optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The alloy with higher cooling rate, lower SDAS, has a more homogeneous microstructure with well distributed network of eutectic and intermetallic phases. The results indicate the presence of Al-Fe-Si phases, Al-Cu phases and eutectic Si particles but their type, distribution and amount varies in the two alloys with different SDAS. EBSD analysis was also performed to study the crystallographic orientation relationships in the microstructure. One of the major highlights of this study is the understanding of the eutectic formation mechanism achieved by studying the orientation relationships of the aluminum in the eutectic to the surrounding primary aluminum dendrites.

  8. Wear behavior and microstructure of hypereutectic Al-Si alloys prepared by selective laser melting

    NASA Astrophysics Data System (ADS)

    Kang, Nan; Coddet, Pierre; Liao, Hanlin; Baur, Tiphaine; Coddet, Christian

    2016-08-01

    This work investigates the microstructure and wear behavior of hypereutectic Al-Si alloys, in-situ fabricated using selective laser melting of a mixture of eutectic Al-12Si (wt.%) and pure Si powders. The first observation was that the size and morphology of the Si phase are strongly influenced by the laser power. In addition, it was also observed that a high laser power causes serious evaporation of aluminum during the remelting process. Dry sliding wear test and Vickers microhardness measurements were employed to characterize the mechanical properties of the material. The lowest wear rate of about 7.0 × 10-4 mm3 N-1 m-1 was observed for samples having the highest value of relative density (96%) and microhardness (105 Hv0.3).

  9. Anisotropic Responses of Mechanical and Thermal Processed Cast Al-Si-Mg-Cu Alloy

    NASA Astrophysics Data System (ADS)

    Adeosun, S. O.; Akpan, E. I.; Balogun, S. A.; Onoyemi, O. K.

    2015-05-01

    The effects of ambient directional rolling and heat treatments on ultimate tensile strength (UTS), hardness (HD), percent elongation (PE), and impact energy (IE) on Al-Si-Mg-Cu alloy casting with reference to inclination to rolling direction are discussed in this article. The results show that rolled and quenched (CQ) sample possess superior UTS and HD to as-cast and those of rolled and aged samples (CA). Improved IE resistance with ductility is shown by both CQ and CA samples. However, these mechanical properties are enhanced as changes in the test sample direction moved away from rolling direction for all heat-treated samples. The CQ samples displayed highest tensile strength (108 MPa) and PE (19.8%) in the 90° direction.

  10. Role of Laser Cladding Parameters in Composite Coating (Al-SiC) on Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Riquelme, Ainhoa; Escalera-Rodriguez, María Dolores; Rodrigo, Pilar; Rams, Joaquin

    2016-08-01

    The effect of the different control parameters on the laser cladding fabrication of Al/SiCp composite coatings on AA6082 aluminum alloy was analyzed. A high-power diode laser was used, and the laser control parameters were optimized to maximize the size (height and width) of the coating and the substrate-coating interface quality, as well as to minimize the melted zone depth. The Taguchi DOE method was applied using a L18 to reduce the number of experiments from 81 to only 18 experiments. Main effects, signal-noise ratio and analysis of variance were used to evaluate the effect of these parameters in the characteristics of the coating and to determine their optimum values. The influence of four control parameters was evaluated: (1) laser power, (2) scanning speed, (3) focal condition, and (4) powder feed ratio. Confirmation test with the optimal control parameters was carried out to evaluate the Taguchi method's effectivity.

  11. Nanoscale analysis on interfacial reactions in Al-Si-Cu alloys and Ti underlayer films

    NASA Astrophysics Data System (ADS)

    Yang, Jun-Mo; Lee, Sukjae; Park, Ju-Chul; Lee, Deok-Won; Lee, Tae-Kwon; Choi, Jin-Tae; Lee, Soun-Young; Kawasaki, Masahiro; Oikawa, Tetsuo

    2003-01-01

    Solid-phase reactions at the interface between sputtered Al-Si-Cu alloys and Ti films were investigated at the atomic scale by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy (EDS) coupled with a field-emission (scanning) transmission electron microscope. The analysis results showed that the interface is composed of an amorphous-like Ti-Si layer, an intermediate-crystalline layer, and a Si-dissolved TiAl3 layer containing dissolved Si TiAl3 with a crystallographic relationship with the Al film. The nanometer-scaled interlayers effectively play a role as a barrier suppressing the interdiffusion reaction of Al and Ti during annealing treatment. Further, the quantitative composition of the interlayers was revealed by the analysis of the intensity profiles obtained from EDS elemental maps.

  12. Secondary and tertiary dendrite arm spacing relationships in directionally solidified Al-Si alloys

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.

    1993-01-01

    Secondary, lambda sub 2, and tertiary, lambda sub 3, dendrite arm spacings have been measured from Al-Si alloys which were directionally solidified as functions of growth velocity, V, temperature gradient, G, and composition, Co. Both lambda sub 2 and lambda sub 3 decreased as the imposed growth velocity and silicon concentrations were increased, and for each function a systematic variance in the rate was seen. Complications with measuring secondary arm spacings are shown and it was found that the tertiary arm data agree much better with coarsening theory, the implication being that lambda sub 3, when measurable, is a more representative and reliable measure of the solidification history than lambda sub 2.

  13. 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.%.

  14. Validated thermodynamic prediction of AlP and eutectic (Si) solidification sequence in Al-Si cast alloys

    NASA Astrophysics Data System (ADS)

    Liang, S. M.; Schmid-Fetzer, R.

    2016-03-01

    The eutectic microstructure in hypoeutectic Al-Si cast alloys is strongly influenced by AlP particles which are potent nuclei for the eutectic (Si) phase. The solidification sequence of AlP and (Si) phases is, thus, crucial for the nucleation of eutectic silicon with marked impact on its morphology. This study presents this interdependence between Si- and P-compositions, relevant for Al-Si cast alloys, on the solidification sequence of AlP and (Si). These data are predicted from a series of thermodynamic calculations. The predictions are based on a self-consistent thermodynamic description of the Al-Si-P ternary alloy system developed recently. They are validated by independent experimental studies on microstructure and undercooling in hypoeutectic Al-Si alloys. A constrained Scheil solidification simulation technique is applied to predict the undercooling under clean heterogeneous nucleation conditions, validated by dedicated experimental observations on entrained droplets. These specific undercooling values may be very large and their quantitative dependence on Si and P content of the Al alloy is presented.

  15. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy.

    PubMed

    Dang, B; Zhang, X; Chen, Y Z; Chen, C X; Wang, H T; Liu, F

    2016-01-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy. PMID:27502444

  16. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

    NASA Astrophysics Data System (ADS)

    Dang, B.; Zhang, X.; Chen, Y. Z.; Chen, C. X.; Wang, H. T.; Liu, F.

    2016-08-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

  17. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

    PubMed Central

    Dang, B.; Zhang, X.; Chen, Y. Z.; Chen, C. X.; Wang, H. T.; Liu, F.

    2016-01-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy. PMID:27502444

  18. Corrosion and protection of heterogeneous cast Al-Si (356) and Al-Si-Cu-Fe (380) alloys by chromate adn cerium inhibitors

    NASA Astrophysics Data System (ADS)

    Jain, Syadwad

    presence of soluble cerium cations showed that of anodic and cathodic activity was not as strongly inhibited as was observed for chromate ions. Overall cerium conversion coating showed good performance on Al-Si (356) ally, but poor performance on Fe- and Cu-rich alloy (380).

  19. Dissolution of Cu/Mg Bearing Intermetallics in Al-Si Foundry Alloys

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2016-08-01

    Evolutions of the Cu/Mg bearing intermetallics were thoroughly investigated in four Al-Si hypoeutectic alloys containing various Cu (1 and 1.6 wt pct) and Mg (0.4 and 0.8 wt pct) contents. The area fractions of Cu/Mg bearing phases before and after solution heat treatment (SHT) were quantified to evaluate the solubility/stability of the phases. Two Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π-Al8FeMg3Si6) which appear as gray color under optical microscope were discriminated by the developed etchant. Moreover, the concentrations of the elements (Cu, Mg, and Si) in α-Al were analyzed. The results illustrated that in the alloys containing ~0.4 pct Mg, Q-Al5Cu2Mg8Si6 phase was dissolved after 6 hours of SHT at 778 K (505 °C); but containing in the alloys ~0.8 pct Mg, it was insoluble/ partially soluble. Furthermore, after SHT at 778 K (505 °C), Mg2Si was partially substituted by Q-phase. Applying a two-step SHT [6 hours@778 K (505 °C) + 8 hours@798 K (525 °C)] in the alloys containing ~0.4 pct Mg helped to further dissolve the remaining Mg bearing intermetallics and further modified the microstructure, but in the alloys containing ~0.8 pct Mg, it caused partial melting of Q-phase. Thermodynamic calculations were carried out to assess the phase formation in equilibrium and in non-equilibrium conditions. There was an excellent agreement between the experimental results and the predicted results.

  20. Phase stability of U-Mo-Ti alloys and interdiffusion behaviors of U-Mo-Ti/Al-Si

    SciTech Connect

    Park, Jong Man; Ryu, Ho Jin; Park, Jae Soon; Oh, Seok Jin; Kim, Chang Kyu; Kim, Yeon Soo; Hofman, Gerard L.

    2008-07-15

    As a remedy for reducing reaction between U-Mo and Al in U-Mo/Al dispersion fuel, adding an alloying element such as Zr and Ti in U-Mo has been proposed at ANL. Although ANL's work showed the potential effectiveness of these elements based on thermodynamic and metallurgical analyses, the effect of a Ti addition in U-Mo remains unproven. The out-of-pile tests of U-Mo-Ti alloys, which focused on phase stability and interdiffusion behavior against Al, are meaningful to predict their efficacy during an irradiation. At the 2006 RERTR conference, we presented our work on the interdiffusion behaviors of U-Mo-Zr/Al-Si. In this paper, we will present the results for substituting U-Mo-Zr with U-Mo-Ti. Unlike U-Mo-Zr alloys, the gamma-heat-treated U-7Mo-xTi (x=1{approx}3 wt%) exhibited a metastable {gamma}-U phase, regardless of the Ti content. In these samples, however, a small amount of second-phase precipitates with a high Ti concentration was observed. The gamma phase stability of the U-Mo-Ti alloys at 500 deg C was similar to that of the U-Mo-Zr alloys. Interdiffusion test results between U-Mo-Ti alloys and Al-Si alloys will also be presented and a comparison with the previous results with U- Mo-Zr/Al-Si will also be included. (author)

  1. Density, Viscosity, and Diffusion Coefficients in Hypoeutectic Al-Si Liquid Alloys: An Assessment of Available Data

    NASA Astrophysics Data System (ADS)

    Poirier, David R.

    2014-08-01

    This article is a review of empirical and calculated data on density, viscosity, and diffusion coefficients in hypereutectic Al-Si liquid alloys. Many regressions of the data were effected in order to consolidate the data as functions, which can be used to calculate each property as a function of temperature and concentration of Si. The chemical diffusion coefficient in the alloys was derived based on the Sutherland model, which relates the diffusion coefficient to viscosity.

  2. Fracture toughness and corrosion resistance of semisolid AlSi5 alloy

    SciTech Connect

    Pola, A.; Montesano, L.; Gelfi, M.; Roberti, R.

    2011-05-04

    The aim of this work was to investigate fracture toughness and corrosion resistance of semisolid AlSi5 castings, compared to samples obtained from conventional casting operations. In order to have a semisolid microstructure, the melt alloy was treated by means of ultrasound during solidification and then poured into permanent moulds. Mechanical properties of semisolid and conventional castings were compared by means of ultimate tensile strength (R{sub m}), yield stress (Rp{sub 02}) and hardness (HV) measurements. Fracture mechanics tests were carried out on Single Edge Notched Bend (SENB) specimens, machined from castings, and pre-cracked by fatigue. These tests were performed to determine the effect of the microstructure on the J-Integral resistance (J-R) behavior and to deeply understand the ductile fracture behaviour of semisolid parts. The J-Integral versus spaced crack extension (J-{Delta}a) curves showed an improved resistance of the semisolid microstructure, due to the higher ductility. Finally, the corrosion behaviour of semisolid samples was compared to that of castings coming from solidification of fully liquid alloy by means of electrochemical potentiodynamic polarization tests. It was observed that the globular microstructure offers better quality, in terms of higher mechanical properties, as a consequence of a more uniform distribution of the solute.

  3. Refinement of primary Si in hypereutectic Al-Si alloys by intensive melt shearing

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Li, H.-T.; Stone, I. C.; Fan, Z.

    2012-01-01

    Hypereutectic Al-Si based alloys are gaining popularity for applications where a combination of light weight and high wear resistance is required. The high wear resistance arising from the hard primary Si particles comes at the price of extremely poor machine tool life. To minimize machining problems while exploiting outstanding wear resistance, the primary Si particles must be controlled to a uniform small size and uniform spatial distribution. The current industrial means of refining primary Si chemically by the addition of phosphorous suffers from a number of problems. In the present paper an alternative, physical means of refining primary Si by intensive shearing of the melt prior to casting is investigated. Al-15wt%Si alloy has been solidified under varying casting conditions (cooling rate) and the resulting microstructures have been studied using microscopy and quantitative image analysis. Primary Si particles were finer, more compact in shape and more numerous with increasing cooling rate. Intensive melt shearing led to greater refinement and more enhanced nucleation of primary Si than was achieved by adding phosphorous. The mechanism of enhanced nucleation is discussed.

  4. Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys

    NASA Astrophysics Data System (ADS)

    Jelinek, B.; Groh, S.; Horstemeyer, M. F.; Houze, J.; Kim, S. G.; Wagner, G. J.; Moitra, A.; Baskes, M. I.

    2012-06-01

    A set of modified embedded-atom method (MEAM) potentials for the interactions between Al, Si, Mg, Cu, and Fe was developed from a combination of each element's MEAM potential in order to study metal alloying. Previously published MEAM parameters of single elements have been improved for better agreement to the generalized stacking fault energy (GSFE) curves when compared with ab initio generated GSFE curves. The MEAM parameters for element pairs were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure garnered from ab initio calculations, with adjustment to reproduce the ab initio heat of formation of the most stable binary compounds. The new MEAM potentials were validated by comparing the formation energies of defects, equilibrium volumes, elastic moduli, and heat of formation for several binary compounds with ab initio simulations and experiments. Single elements in their ground-state crystal structure were subjected to heating to test the potentials at elevated temperatures. An Al potential was modified to avoid formation of an unphysical solid structure at high temperatures. The thermal expansion coefficient of a compound with the composition of AA 6061 alloy was evaluated and compared with experimental values. MEAM potential tests performed in this work, utilizing the universal atomistic simulation environment (ASE), are distributed to facilitate reproducibility of the results.

  5. Microstructure Evolution of Cold-Sprayed Al-Si Alloy Coatings on γ-TiAl During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2015-08-01

    This paper investigated the influence of heat treatment on the microstructure of Al-Si alloy coatings on γ-TiAl alloy. The coatings were prepared by cold spraying with Al-12Si and Al-20Si alloy powders as the feedstock, and then the as-sprayed coatings were subjected to heat treatment. The microstructure, chemical composition, and phase transformation of the coatings were studied by SEM, XRD, and EPMA. The diffusing behavior of Al and Si during heat treatment was investigated. The results showed that a silicon-aluminizing coating was formed through the inward diffusion of Al/Si elements into the substrate. The obtained kinetics curve of the formation of silicon-aluminizing coating at 580 °C similarly followed parabolic law.

  6. Mechanistic Selection and Growth of Twinned Bicrystalline Primary Si in Near Eutectic Al-Si Alloys

    SciTech Connect

    Choonho Jung

    2006-12-12

    Morphological evolution and selection of angular primary silicon is investigated in near-eutectic Al-Si alloys. Angular silicon arrays are grown directionally in a Bridgman furnace at velocities in the regime of 10{sup -3} m/sec and with a temperature gradient of 7.5 x 10{sup 3} K/m. Under these conditions, the primary Si phase grows as an array of twinned bicrystalline dendrites, where the twinning gives rise to a characteristic 8-pointed star-shaped primary morphology. While this primary Si remains largely faceted at the growth front, a complex structure of coherent symmetric twin boundaries enables various adjustment mechanisms which operate to optimize the characteristic spacings within the primary array. In the work presented here, this primary silicon growth morphology is examined in detail. In particular, this thesis describes the investigation of: (1) morphological selection of the twinned bicrystalline primary starshape morphology; (2) primary array behavior, including the lateral propagation of the starshape grains and the associated evolution of a strong <100> texture; (3) the detailed structure of the 8-pointed star-shaped primary morphology, including the twin boundary configuration within the central core; (4) the mechanisms of lateral propagation and spacing adjustment during array evolution; and (5) the thermosolutal conditions (i.e. operating state) at the primary growth front, including composition and phase fraction in the vicinity of the primary tip.

  7. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-09-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  8. Microstructure Evolution and Rheological Behavior of Cooling Slope Processed Al-Si-Cu-Fe Alloy Slurry

    NASA Astrophysics Data System (ADS)

    Das, Prosenjit; Samanta, Sudip K.; Bera, Supriya; Dutta, Pradip

    2016-05-01

    In the present work, microstructure evolution during semi-solid slurry generation of Al-Si-Cu-Fe alloy, using a cooling slope, was studied and the effect of microstructural morphology of the slurry on its rheological behavior was investigated. Microstructure evolution during melt flow along the slope was studied by extracting samples from various locations of the slope and performing rapid oil quenching experiments. Quantitative investigation was performed to evaluate primary phase shape and size for different process conditions of the semi-solid slurry, and subsequently rheological investigations were performed to correlate slurry morphology with its flow behavior. Three different types of rheological experiments were performed: isothermal test, shear jump test, and shear time test, in order to investigate rheological behavior of the semi-solid slurry. In addition, effect of melt treatment, by adding modifier (0.1 wt pct of Al-10Sr) and grain refiner (0.15 wt pct of Al-5Ti-1B), on the microstructure evolution during slurry generation, flow behavior of the slurry, and intermetallics formation was studied.

  9. Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

    2016-06-01

    Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

  10. Microstructure and microhardness evolution of melt-spun Al-Si-Cu alloy

    NASA Astrophysics Data System (ADS)

    Ahmed, Emad M.; Ebrahim, M. R.

    2014-04-01

    Al-11 wt.% Si-11 wt.% Cu (11.29 at.% Si-5.1 at.% Cu) melt was rapidly solidified into ribbons and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and microhardness technique. The Rietveld X-ray diffraction analysis was applied successfully to analyze the microstructure and phase precipitations. The high cooling rate obtained in rapid solidification has a significant influence on the microstructure and microhardness of this alloy. On the basis of the Al peaks shift measured in the XRD scans, a solid solubility extension value of 3.95 at.% Si and 3.54 at.% Cu in α-Al were determined. No XRD peaks of the Si phase have been detected. XRD peaks of the intermetallic Al2Cu phase have been observed clearly with estimated content of 12.6 wt.%. During prolonged annealing process at 350°C/25 h, XRD peaks of the Si phase clearly appeared with estimated content of 8.6 wt.% and, moreover, the Al2Cu phase content increased to 16 wt.%. The estimated crystallite size and micro-strain % of α-Al are 30 nm and 0.056, respectively. The melt-spun wheel side ribbon represents ultra-fine microstructure with particles size less than 1μm and exhibits enhancement of hardness to 241 HV. Hardness has further increased to 291 HV during heat treatment (150°C/12 h). Rapid solidification exhibited a great influence on microstructure and microhardness of the Al-Si-Cu alloy.

  11. Wettability of binary and ternary alloys of the system Al-Si-Mg with SiC particulates

    SciTech Connect

    Narciso, J.; Alonso, A.; Pamies, A.; Garcia-Cordovilla, C. . Centro de Investigacion y Desarrollo); Louis, E. . Centro de Investigacion y Desarrollo Univ. de Alicante . Dept. de Fisica Aplicada)

    1994-12-01

    The authors have presented results of an investigation of wettability of SiC particulates by liquid alloys of the Al-Si-Mg system. The evaluation of wetting has been carried out through the determination of the threshold pressure for infiltration of packed SiC particulates by the liquid alloy. The results indicate that whereas Si and Mg additions do not affect wetting, in the case of the ternary alloys the contact angle decreases in an amount proportional to the content of Mg[sub 2]Si.

  12. Effect of Electromagnetic Vibration on the Agglomeration Behavior of Primary Silicon in Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Han, Yecong; Li, Qiulin; Liu, Wei; He, Yanjie

    2012-05-01

    An experimental apparatus that enables the simultaneous application of an alternating electric field and a stationary magnetic field was developed. Electromagnetic vibration was induced in a hypereutectic Al-Si alloy melt during solidification at a constant cooling rate. The results showed that the silicon particles collide with each other and agglomerate into clusters with the application of an electromagnetic vibration. With the increase of the electromagnetic force F, the sizes of the silicon clusters decrease and the clusters become more compact.

  13. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys

    PubMed Central

    Li, Jiehua; Hage, Fredrik S.; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-01-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP ‘patch’ dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption. PMID:27120994

  14. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys.

    PubMed

    Li, Jiehua; Hage, Fredrik S; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-01-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP 'patch' dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption. PMID:27120994

  15. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Li, Jiehua; Hage, Fredrik S.; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-04-01

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP ‘patch’ dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption.

  16. Effects of Melt Thermal-Rate Treatment on Fe-Containing Phases in Hypereutectic Al-Si Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Qinglei; Geng, Haoran; Zhang, Shuo; Jiang, Huawei; Zuo, Min

    2013-11-01

    In this paper, effects of melt thermal-rate treatment (MTRT) on Fe-containing phases in hypereutectic Al-Si alloy were investigated. Results show that MTRT can refine microstructures and improve castability, mechanical properties, wear characteristics, and corrosion resistance of Fe-containing Al-Si alloy. When Al-15Si-2.7Fe alloy is treated with MTRT by 1203 K (930 °C) melt: coarse primary Si and plate-like Fe-containing phase both can be refined to small blocky morphology, and the long needle-like Fe-containing phase disappears almost entirely; ultimate tensile strength and elongation are 195 MPa and 1.8 pct, and increase by 12.7 and 50 pct, respectively; and the wear loss and coefficient of friction decrease 7 to 17 and 24 to 30 pct, respectively, compared with that obtained with conventional casting technique. Corrosion resistance of the alloy treated with MTRT by 1203 K (930 °C) melt is the best, that is it has the lowest i corr value and the highest E corr value. Besides, effects of MTRT on Al-15Si-xFe (x = 0.2, 0.7, 1.7, 3.7, 4.7) alloys were also studied, MTRT can only refine microstructure and improve mechanical properties of Al-15Si alloy with 0.7 to 3.7 pct Fe content greatly in the present work.

  17. Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt

    NASA Astrophysics Data System (ADS)

    El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

    2014-10-01

    The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside α-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of α-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of

  18. Effect of thermally stable Cu- and Mg-rich aluminides on the high temperature strength of an AlSi12CuMgNi alloy

    SciTech Connect

    Asghar, Z.

    2014-02-15

    The internal architecture of an AlSi12CuMgNi piston alloy, revealed by synchrotron tomography, consists of three dimensional interconnected hybrid networks of Cu-rich aluminides, Mg-rich aluminides and eutectic/primary Si embedded in an α-Al matrix. The strength at room temperature and at 300°C is studied as a function of solution treatment time at 490°C and compared with results previously reported for an AlSi12Ni alloy. The addition of 1 wt% Cu and 1 wt% Mg to AlSi12CuMgNi increases the room temperature strength by precipitation hardening while the strength at 300°C is similar for both alloys in as-cast condition. The strength of AlSi12CuMgNi decreases with solution treatment time and stabilizes at 4 h solution treatment. The effect of solution treatment time on the strength of the AlSi12CuMgNi alloy is less pronounced than for the AlSi12Ni alloy both at room temperature and at 300°C. - Highlights: • The 3D microstructure of AlSi12CuMgNi is revealed by synchrotron tomography. • An imaging analysis procedure to segment phases with similar contrasts is presented. • 1 wt% Cu and Mg results in the formation of 3D networks of rigid phases. • AlSi12CuMgNi is stronger than AlSi12Ni owing to the stability of the 3D networks.

  19. Effects of breadfruit seed hull ash on the microstructures and properties of Al-Si-Fe alloy/breadfruit seed hull ash particulate composites

    NASA Astrophysics Data System (ADS)

    Atuanya, C. U.; Ibhadode, A. O. A.; Dagwa, I. M.

    2012-01-01

    The microstructures and properties of Al-Si-Fe alloy matrix composites reinforced with different weight fractions of breadfruit seed hull (husk) ash particles of size 500 nm were investigated. Six (6) different weight fractions of breadfruit seed hull ash particles were added to aluminium alloy matrix using a double stir-casting method. Microstructural analysis shows that with the increase of the reinforcement weight fraction, the matrix grain size decreases. The mechanical properties of the composites are improved over the matrix materials, except for the slightly decrease of the impact energy. Fracture surface examination indicates that there is a good interfacial bonding between the aluminium alloy matrix and the breadfruit seed hull ash particles and that fracture initiation does not occur at the particle-matrix interface. Hence, incorporation of breadfruit seed hull ash particles in aluminium matrix can lead to the production of low cost aluminium composites with improved hardness and strength. These composites can find applications in automotive components where light weight materials are required with good stiffness and strength.

  20. Effect of T6 heat treatment on the microstructural and mechanical properties of Al-Si-Cu-Mg alloys

    NASA Astrophysics Data System (ADS)

    Patel, Dhruv; Davda, Chintan; Solanki, P. S.; Keshvani, M. J.

    2016-05-01

    In this communication, it is aimed to optimize the conditions for T6 heat treatment of permanent die cast Al-Si-Cu-Mg alloys. Various solutionizing temperatures, aging treatments and soaking times were used to improve / modify the mechanical properties of presently studied alloys. Formation mechanism of the particles was understood by carrying out optical microscopy and energy dispersive X-ray (EDX) spectroscopy measurements. Spherical particles of alloys were studied for their microstructural properties using scanning electron microscopy (SEM). Microhardness test was performed to investigate their mechanical properties. Dependence of cluster formation and microhardness of the alloys on the adequate solutionizing temperature, aging treatment and soaking time has been discussed in detail.

  1. Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase

    NASA Astrophysics Data System (ADS)

    Hou, L. G.; Yu, H.; Cui, H.; Cai, Y. H.; Zhuang, L. Z.; Zhang, J. S.

    2013-04-01

    Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined α-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized α-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the α-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined α-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized α-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.

  2. X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si hypoeutectic alloy

    SciTech Connect

    Manickaraj, Jeyakumar; Gorny, Anton; Shankar, Sumanth; Cai, Zhonghou

    2014-02-17

    The evolution of strontium (Sr) containing intermetallic phase in the eutectic reaction of Sr-modified Al-Si hypoeutectic alloy was studied with high energy synchrotron beam source for nano-diffraction experiments and x-ray fluorescence elemental mapping. Contrary to popular belief, Sr does not seem to interfere with the Twin Plane Re-entrant Edge (TPRE) growth mechanism of eutectic Si, but evolves as the Al{sub 2}Si{sub 2}Sr phase during the eutectic reaction at the boundary between the eutectic Si and Al grains.

  3. Thermal and Microstructure Characterization of Zn-Al-Si Alloys and Chemical Reaction with Cu Substrate During Spreading

    NASA Astrophysics Data System (ADS)

    Berent, Katarzyna; Pstruś, Janusz; Gancarz, Tomasz

    2016-04-01

    The problems associated with the corrosion of aluminum connections, the low mechanical properties of Al/Cu connections, and the introduction of EU directives have forced the potential of new materials to be investigated. Alloys based on eutectic Zn-Al are proposed, because they have a higher melting temperature (381 °C), good corrosion resistance, and high mechanical strength. The Zn-Al-Si cast alloys were characterized using differential scanning calorimetry (DSC) measurements, which were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed at temperature ranges of -50 to 250 °C and 25 to 300 °C, respectively. The addition of Si to eutectic Zn-Al alloys not only limits the growth of phases at the interface of liquid solder and Cu substrate but also raises the mechanical properties of the solder. Spreading test on Cu substrate using eutectic Zn-Al alloys with 0.5, 1.0, 3.0, and 5.0 wt.% of Si was studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed with contact times of 1, 8, 15, 30, and 60 min, and at temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreadability of Zn-Al-Si on Cu was determined. Selected, solidified solder/substrate couples were cross-sectioned, and the interfacial microstructures were studied using scanning electron microscopy and energy dispersive x-ray spectroscopy. The growth of the intermetallic phase layer was studied at the solder/substrate interface, and the activation energy of growth of Cu5Zn8, CuZn4, and CuZn phases were determined.

  4. Amorphous structure and properties in laser-clad Ni-Cr-Al coating on Al-Si alloy

    NASA Astrophysics Data System (ADS)

    Liang, Gongying; Wong, T. T.; Su, J. Y.; Woo, C. H.

    1999-09-01

    A Ni-Cr-Al coating was clad by a 5 kW CO2 laser with different laser power on Al-Si alloy. Using transmission electron microscopy, a mixing microstructure containing Ni- based amorphous structures was observed in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni3Al crystals coexisted in the cladding. According to the morphologies of Ni-based amorphous structures, the amorphous structure existed not only in the net-like boundaries surrounding the granular structure but also in the granular structure. The microhardness of the mixture amorphous structure is between HV 600 - 800, which is lower than that of crystal phases in the coating. A differential thermal analysis showed that Ni- based amorphous structure exhibits a higher initial crystallizing temperature (about 588 degree(s)C), which is slightly higher than that of the eutectic temperature of Al- Si alloy. The wear experimental results showed that some amorphous structure exist in the laser cladding can reduce the peeling of the granular phases from matrix, and improve the its wear resistance.

  5. Improving Tribological Properties of Cast Al-Si Alloys through Application of Wear-Resistant Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Culliton, David; Betts, Anthony; Carvalho, Sandra; Kennedy, David

    2013-04-01

    Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity.

  6. Precipitation of silicon from splat-cooled Al-Si alloys

    NASA Technical Reports Server (NTRS)

    Matyja, H.; Russell, K. C.; Grant, N. J.; Giessen, B. C.

    1975-01-01

    Splat cooled Al-Si solid solutions with 1 to 11 at.% Si were prepared and their precipitation kinetics were studied by transmission electron microscopy. The time required for appearance of particles visible at a magnification of 35,000 times was determined at temperatures between 248 K and 573 K. The resulting Arrhenius plots yielded activation energies ranging from 55 to 40 plus or minus 2kJ/mol over the composition range. Precipitate densities were higher and denuded zones of 100 to 150 nm were narrower than in comparable solid quenched samples. The activation energies are explained in terms of excess point defect concentrations.

  7. Thermodynamics of Nitrogen in Fe-Mn-Al-Si-C Alloy Melts

    NASA Astrophysics Data System (ADS)

    Paek, Min-Kyu; Chatterjee, Saikat; Pak, Jong-Jin; Jung, In-Ho

    2016-04-01

    Thermodynamic behavior of nitrogen in the entire range of the Fe-Mn-Al-Si-C liquid solution was modeled based on the critical evaluation and optimization of all available experimental data. The Gibbs energy of liquid solution was described using the Modified Quasichemical Model (MQM) in the pair approximation, instead of classical Wagner Interaction Parameter Formalism, to consider the strong interactions between species in liquid state. In particular, the dissolution behavior of N and formation of AlN in the entire ternary and higher order liquids were accurately predicted from the MQM only with binary model parameters of N.

  8. Mechanics and mechanisms of surface damage in Al-Si alloys under ultra-mild wear conditions

    NASA Astrophysics Data System (ADS)

    Chen, Ming

    Al-Si alloys intended for use in engine components must operate under ultra-mild wear (UMW) conditions to fit an acceptable amount of wear during a typical vehicle life. This study simulated surface damage in a UMW regime on five chemically etched Al-Si alloy surfaces using a pin-on-disc tribometer at low loads (0.5-2.0 N) under boundary lubricated conditions. The five alloys contained 11 to 25 wt.% Si and differed in matrix hardness, silicon particle morphology, and size. The mechanisms leading to the UMW damage and the role that the matrix hardness and microstructure play on said mechanisms were studied. Quantitative measurement methods based on statistical analysis of particle height changes and material loss from elevated aluminum using a profilometer technique were developed and used to assess UMW. The Greenwood and Tripp's numerical model was adapted to analyze the contact that occurred between Al-Si alloys with silicon particles protruding above the aluminum and steel balls. The estimation of the real contact pressure applied to the silicon particles was used to rationalize the damage mechanisms. The UMW mechanisms consisted of (i) abrasive wear on the top of the silicon particle surfaces; (ii) sinking-in of the silicon particles; (iii) piling-up of the aluminium around sunken-in particles and (vi) wear of the aluminium by the counterface, which eventually led to the initiation of UMW-II. Increasing the size or areal density of silicon particles with small aspect ratios delayed the onset of UMW-II by providing resistance against the silicon particles sinking-in and the aluminum piling-up. The UMW wear rates, however, began to decrease after long sliding cycles once an oil residue layer supported by hardened ultra-fine subsurface grains formed on the deformed aluminium matrix. The layer formation depended on the microstructure and applied load. Overall experimental observations suggested that Al-11% Si with small silicon particles exhibited optimal long

  9. Assessment of Post-eutectic Reactions in Multicomponent Al-Si Foundry Alloys Containing Cu, Mg, and Fe

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2015-07-01

    Post-eutectic reactions occurring in Al-Si hypoeutectic alloys containing different proportions of Cu, Mg, and Fe were thoroughly investigated in the current study. As-cast microstructures were initially studied by optical and electron microscopy to investigate the microconstituents of each alloy. Differential scanning calorimetry (DSC) was then used to examine the phase transformations occurring during the heating and cooling processes. Thermodynamic calculations were carried out to assess the phase formation under equilibrium and in nonequilibrium conditions. The Q-Al5Cu2Mg8Si6 phase was predicted to precipitate from the liquid phase, either at the same temperature or earlier than the θ-Al2Cu phase depending on the Cu content of the alloy. The AlCuFe-intermetallic, which was hardly observed in the as-cast microstructure, significantly increased after the solution heat treatment in the alloys containing high Cu and Fe contents following a solid-state transformation of the β-Al5FeSi phase. After the solution heat treatment, the AlCuFe-intermetallics were mostly identified with the stoichiometry of the Al7Cu2Fe phase. Thermodynamic calculations and microstructure analysis helped in determining the DSC peak corresponding to the melting temperature of the N-Al7Cu2Fe phase. The effect of Cu content on the formation temperature of π-Al8Mg3FeSi6 is also discussed.

  10. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    NASA Astrophysics Data System (ADS)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  11. Evaluation of dendrite morphology using fractal dimension and dimensionless perimeter in unidirectionally solidified Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Ohsasa, K.; Natsume, Y.; Sekiya, T.; Hatayama, T.

    2015-06-01

    The dendrite morphology of unidirectionally solidified Al-Si alloys was evaluated by measuring the fractal dimension and dimensionless perimeter of dendrites. In an unidirectional solidification experiment, columnar crystals grew from a bottom chill and columnar to equiaxed transition (CET) occurred at the upper part of an ingot. Then, equiaxed crystals were formed at the top of the ingot. Different dendrite morphology was observed in longitudinal, transverse and oblique sections, however, the fractal dimension or dimensionless perimiter of the dendrites in the sections with same local solidification time showed same values, and continuously decreased with increase in the local solidification time through columnar, CET and equiaxed regions. It can be considered that the fractal dimension and dimensionless perimiter of dendrites are controlled by local solidification time and irrespective of dendrite morphology. This result demonstrated the potential of the fractal dimension and dimensionless perimiter as a parameter for estimating local solidification time of an ingot in which the measurement of SDAS is difficult.

  12. 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

    2013-10-01

    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.

  13. Mechanical properties of rapidly solidified Al-Si-Ni-Ce P/M alloys

    SciTech Connect

    Lee, T.H. |; Kawamura, Yoshihito; Inoue, Akihisa; Masumoto, Tsuyoshi; Cho, S.S.

    1997-02-15

    To meet current and future materials needs for structural members or engine parts in aircraft, motorcycle and automobile, it is needed to develop high-performance light weight alloys with higher room-temperature strength, higher elevated temperature strength, higher wear resistance and lower thermal expansion. Powder metallurgy (P/M) alloys with novel mechanical properties have been developed by a rapid solidification technique. The improved properties result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit. The aim of this paper is to examine the effect of adding of glass-forming elements, Ni and Ce, to a RS P/M Al-19at.%Si alloy for the development of high strength and good wear resistance aluminum alloys.

  14. Work of Adhesion in Al/SiC Composites with Alloying Element Addition

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Fan, Tongxiang; Zhang, Di

    2013-11-01

    In the current work, a general methodology was proposed to demonstrate how to calculate the work of adhesion in a reactive multicomponent alloy/ceramic system. Applying this methodology, the work of adhesion of Al alloy/SiC systems and the influence of different alloying elements were predicted. Based on the thermodynamics of interfacial reaction and calculation models for component activities, the equilibrium compositions of the melts in Al alloy/SiC systems were calculated. Combining the work of adhesion models for reactive metal/ceramic systems, the work of adhesion in Al alloy/SiC systems both before and after the reaction was calculated. The results showed that the addition of most alloying elements, such as Mg, Si, and Mn, could increase the initial work of adhesion, while Fe had a slightly decreasing effect. As for the equilibrium state, the additions of Cu, Fe, Mn, Ni, Ti, and La could increase the equilibrium work of adhesion, but the additions of Mg and Zn had an opposite effect. Si was emphasized due to its suppressing effect on the interfacial reaction.

  15. Preparation of Al-Si Master Alloy by Electrochemical Reduction of Volcanic Rock in Cryolite Molten Salt

    NASA Astrophysics Data System (ADS)

    Liu, Aimin; Shi, Zhongning; Xu, Junli; Hu, Xianwei; Gao, Bingliang; Wang, Zhaowen

    2016-06-01

    Volcanic rock found in the Longgang Volcano Group in Jilin Province of China has properties essentially similar to Apollo lunar soils and previously prepared lunar soil simulants, such as Johnson Space Center Lunar simulant and Minnesota Lunar simulant. In this study, an electrochemical method of preparation of Al-Si master alloy was investigated in 52.7 wt.%NaF-47.3 wt.%AlF3 melt adding 5 wt.% volcanic rock at 1233 K. The cathodic electrochemical process was studied by cyclic voltammetry, and the results showed that the cathodic reduction of Si(IV) is a two-step reversible diffusion-controlled reaction. Si(IV) is reduced to Si(II) by two electron transfers at -1.05 V versus platinum quasi-reference electrode in 52.7 wt.%NaF-47.3 wt.%AlF3 molten salt adding 5 wt.% volcanic rock, while the reduction peak at -1.18 V was the co-deposition of aluminum and silicon. In addition, the cathodic product obtained by galvanostatic electrolysis for 4 h was analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy and energy dispersive spectrometry. The results showed that the phase compositions of the products are Al, Si, Al5FeSi, and Al3.21Si0.47, while the components are 90.5 wt.% aluminum, 4.4 wt.% silicon, 1.9 wt.% iron, and 0.2 wt.% titanium.

  16. The debonding and fracture of Si particles during the fatigue of a cast Al-Si alloy

    SciTech Connect

    Gall, K.; Yang, N.; Horstemeyer, M.; McDowell, D.L.; Fan, J.

    1999-12-01

    Constant-amplitude high-cycle fatigue tests ({sigma}{sub max} = 133 MPa, {sigma}{sub max}/{sigma}{sub y} = 0.55, and R = 0.1) were conducted on a cylindrical samples machined from a cast A356-T6 aluminum plate: The fracture surface of the sample with the smallest fatigue-crack nucleating defect was examined using a scanning electron microscope (SEM). For low crack-tip driving forces (fatigue-crack growth rates of da/dN {lt} 1 x 10{sup {minus}7} m/cycle), the authors discovered that a small semicircular surface fatigue crack propagated primarily through the Al-1% Si dendrite cells. The silicon particles in the eutectic remained intact and served as barriers at low fatigue-crack propagation rates. when the semicircular fatigue crack inevitably crossed the three-dimensional Al-Si eutectic network, it propagated primarily along the interface between the silicon particles and the Al-1% Si matrix. Furthermore, nearly all of the silicon particles were progressively debonded by the fatigue cracks propagating at low rates, with the exception of elongated particles with a major axis perpendicular to the crack plane, which were fractured. As the fatigue cracks grew with a high crack-tip driving force (fatigue-crack growth rates of da/dN {gt} 1 x 10{sup {minus}6} m/cycle), silicon particles ahead of the crack tip were fractured, and the crack subsequently propagated through the weakest distribution of prefractured particles in the Al-Si eutectic. Only small rounded silicon particles were observed to debond while the fatigue crack grew at high rates. Using fracture-surface markings and fracture mechanics, a macroscopic measure of the maximum critical driving force between particle debonding vs fracture during fatigue-crack growth was calculated to be approximately K{sub max}{sup tr} {approx} 6.0 MPa {radical}m for the present cast A356 alloy.

  17. Preparation of Al-Si Master Alloy by Electrochemical Reduction of Volcanic Rock in Cryolite Molten Salt

    NASA Astrophysics Data System (ADS)

    Liu, Aimin; Shi, Zhongning; Xu, Junli; Hu, Xianwei; Gao, Bingliang; Wang, Zhaowen

    2016-04-01

    Volcanic rock found in the Longgang Volcano Group in Jilin Province of China has properties essentially similar to Apollo lunar soils and previously prepared lunar soil simulants, such as Johnson Space Center Lunar simulant and Minnesota Lunar simulant. In this study, an electrochemical method of preparation of Al-Si master alloy was investigated in 52.7 wt.%NaF-47.3 wt.%AlF3 melt adding 5 wt.% volcanic rock at 1233 K. The cathodic electrochemical process was studied by cyclic voltammetry, and the results showed that the cathodic reduction of Si(IV) is a two-step reversible diffusion-controlled reaction. Si(IV) is reduced to Si(II) by two electron transfers at -1.05 V versus platinum quasi-reference electrode in 52.7 wt.%NaF-47.3 wt.%AlF3 molten salt adding 5 wt.% volcanic rock, while the reduction peak at -1.18 V was the co-deposition of aluminum and silicon. In addition, the cathodic product obtained by galvanostatic electrolysis for 4 h was analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy and energy dispersive spectrometry. The results showed that the phase compositions of the products are Al, Si, Al5FeSi, and Al3.21Si0.47, while the components are 90.5 wt.% aluminum, 4.4 wt.% silicon, 1.9 wt.% iron, and 0.2 wt.% titanium.

  18. Interfacial Heat Transfer during Die Casting of an Al-Si-Cu Alloy

    NASA Astrophysics Data System (ADS)

    Hamasaiid, A.; Wang, G.; Davidson, C.; Dour, G.; Dargusch, M. S.

    2009-12-01

    The relationship between in-cavity pressure, heat flux, and heat-transfer coefficient during high-pressure die casting of an Al-9 pct Si-3 pct Cu alloy was investigated. Detailed measurements were performed using infrared probes and thermocouple arrays that accurately determine both casting and die surface temperatures during the pressure die casting of an aluminum A380 alloy. Concurrent in-cavity pressure measurements were also performed. These measurements enabled the correlation between in-cavity pressure and accurate heat-transfer coefficients in high-pressure die-casting operations.

  19. Structure of molten Al and eutectic Al-Si alloy studied by neutron diffraction

    SciTech Connect

    Dahlborg, U.; Kramer, Matthew J.; Besser, M.; Morris, J. R.; Calvo-Dahlborg, M.

    2012-11-24

    The structure of molten eutectic Al87.8Si12.2 alloy has been studied by neutron diffraction during a temperature cycle. For comparison measurements were performed on pure molten Al. The measurements show that the alloy after heating above the liquidus contains particles of two kinds, aluminum-rich and silicon-rich. The silicon-rich particles are partly dissolved after a further heating. Earlier published data obtained by the γ-ray absorption technique of the density of the molten eutectic Al–Si alloy had demonstrated the existence of two temperatures above the liquidus temperature: A dissolution temperature Td, at which the microstructure of the melt inherited from the ingot starts to dissolve and a branching temperature, Tb, at which the melt reaches a fully mixed state. The highest temperature that was possible to reach during the neutron experiments lies between Td and Tb. The obtained results support these conclusions that molten alloys after melting are inhomogeneous up to a temperature well above the liquidus. Moreover, the difference in shape between the static structure factors measured by neutron and X-ray diffraction on molten aluminum is observed and is found to be more accentuated and to extend to larger wavevectors than in earlier works.

  20. Tensile and Fracture Properties of Cast and Forged Composite Synthesized by Addition of Al-Si Alloy to Magnesium

    NASA Astrophysics Data System (ADS)

    Nanjunda Swamy, H. M.; Nath, S. K.; Ray, S.

    2009-12-01

    Cast Mg-Al-Si composites synthesized by addition of Al-Si alloy containing 10, 15, and 20 wt pct of Si, in molten magnesium, to generate particles of Mg2Si by reaction between silicon and magnesium during stir casting has opened up the possibility to control the size of these particles. The microstructure of the cast composite consists of relatively dark polyhedral phase of Mg2Si and bright phase of β-Al12Mg17 along the boundary between dendrites of α-Mg solid solution. After hot forging at 350 °C, the microstructure has changed to relatively smaller sizes of β-Al12Mg17 and Mg2Si particles apart from larger grains surrounded by smaller grains due to dynamic recovery and recrystallization. Some of the Mg2Si particles crack during forging. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing volume fraction of Mg2Si, but the hardness is higher in forged composites by about 100 BHN. Yield strength in cast composites improves over that of the cast alloy, but there is a marginal increase in yield strength with increasing Mg2Si content. In forged composites, there is significant improvement in yield strength with increasing Mg2Si particles and also over those observed in their cast counterpart. In cast composites, ultimate tensile strength (UTS) decreases with increasing Mg2Si content possibly due to increased casting defects such as porosity and segregation, which increases with increasing Mg2Si content and may counteract the strengthening effect of Mg2Si content. However, in forged composite, UTS increases with increasing Mg2Si content until 5.25 vol pct due to elimination of segregation and lowering of porosity, but at higher Mg2Si content of 7 vol pct, UTS decreases, possibly due to extensive cracking of Mg2Si particles. On forging, the ductility decreases in forged alloy and composites possibly due to the remaining strain and the forged microstructure. The initiation fracture toughness, J IC , decreases drastically in

  1. PEO of pre-anodized Al-Si alloys: Corrosion properties and influence of sealings

    NASA Astrophysics Data System (ADS)

    Mohedano, M.; Matykina, E.; Arrabal, R.; Mingo, B.; Pardo, A.

    2015-08-01

    Voltage-controlled PEO coatings were developed on A356 aluminum alloys (gravity-cast and rheocast) with a pre-anodized layer. The influence of the alloy manufacturing process and the effect of Si-rich phase on the structure and composition of the oxide layers were evaluated using SEM, EDS and XRD. The pre-anodized oxide layer preserves the microstructure of the substrate due to the presence of secondary phases that have a different behavior relative to the matrix during anodizing. PEO coatings consisted of a mixture of α-Al2O3, γ-Al2O3 and mullite. The corrosion behavior and the effectiveness of different sealing techniques based on salts of nickel, cobalt, cerium and phosphonic acid were also studied. Post-treatments improved the hydrophobic properties of the coatings and showed a beneficial effect, significantly increasing the coating impedance and thereby reducing the susceptibility to corrosion.

  2. Magnetic properties of ultrasoft-nanocomposite FeAlSiBNbCu alloys

    NASA Astrophysics Data System (ADS)

    Todd, I.; Tate, B. J.; Davies, H. A.; Gibbs, M. R. J.; Kendall, D.; Major, R. V.

    2000-06-01

    The effects of up to 10 at% substitution of Fe by Al on the microstructure and DC and AC magnetic properties of nanocrystalline FeSiBCuNb alloy ribbon are summarised and analysed. The minimum DC H c developed during annealing decreases by 40% for 2 at% Al (to 0.3 A/m) and remains roughly constant for larger Al contents. The largest peak value of μ 0.4 at 50 Hz also corresponds to 2 at% Al. The best frequency response for μ 0.4 occurs for 6 at% Al while there was no improvement in AC power loss behaviour over the 0% Al alloy. The improvements in DC H c and AC μ 0.4 are ascribed to a reduction in K 1 of the Fe-Si-based nanocrystallites by the introduction of Al.

  3. Automatic optimization of localized heat treatment for Al-Si-Mg alloys

    NASA Astrophysics Data System (ADS)

    Ludwig, A.; Holzmann, T.

    2016-03-01

    Material properties of aluminium alloys can usually be achieved by a heat treatment and quenching procedure. In case that only local strengthening is needed, a local heat treatment and quenching strategy could be an option to the energy intensive, time consuming and costly treatment of the whole part. One of the essential problem using a local strengthening procedure is the lack of knowledge about suitable process parameters. Therefore, a multiple criteria optimization approach with local strengthening as target function was set up, whereby the material constitution was calculated based on the precipitation evolution during local heat treatment and cooling. By automatically varying the exposure time and laser power, a series of process simulations was performed to find adequate process parameters for the sufficient local strengthening of the alloy.

  4. Directional solidification of binary AlSi-alloys in diffusive and convective regimes

    NASA Astrophysics Data System (ADS)

    Steinbach, Sonja; Ratke, Lorenz; Masslow, Hans Dieter

    2005-08-01

    Since heat and mass transport determines fully the solidification microstructure, it is essential to perfectly control both in a controlled manner. One extreme is experimentation under microgravity conditions, in which all sources of fluid flow are eliminated; the other extreme is microgravity with an induced fluid flow being fully controlled by the experimenter. The first move was done with the experiment on TEXUS 39. A ARTEX facility under diffuse material transport conditions. In the ARTEXplus facility, flown on TEXUS 41, an implemented coil system generates a controlled fluid flow in the melt. The experiment on TEXUS 41 should lead to a direct comparison of the effect of controlled convective conditions and pure diffusive growth conditions on microstructure development using the same alloy. A sample evaluation shows a decreasing of the primary spacing with increasing fluid flow whereas the secondary dendrite arm spacing increases.

  5. Strain Ratio Effects on Low-Cycle Fatigue Behavior of Gravity Cast Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Fan, K. L.; Liu, X. S.; He, G. Q.; Cheng, H.; Lv, S. Q.

    2015-10-01

    The strain-controlled low-cycle fatigue properties of gravity cast Al-Si-Cu alloys for engine cylinder heads were investigated. At strain ratios of R ɛ = -2, 0, and 0.1, the cyclic stress amplitude progressively increased from initiation to the 450th cycle, and then proceeded into a steady stage until failure. At a strain ratio of R ɛ = -∞, the material exhibited a continuous cyclic hardening. The hysteresis loops in this alloy for the 2nd and half-life cycle were tension/compression asymmetry, which also corresponded well to the evolution of peak/valley stress. Transmission electron microscopy analysis suggested that cyclic hardening was caused by the dislocations multiplication/tangles at strain ratios of R ɛ = -∞ and 0. Besides, the presence of dislocation cross slip contributed to cyclic stabilization observed at later stage of deformation at a strain ratio of R ɛ = 0. Micro-analysis of specimen fracture appearance was conducted in order to obtain the fracture characteristics and crack paths for different strain ratios. It showed that the fatigue cracks initiated basically at the internal defects in the samples. Meanwhile, at strain ratios of R = -∞ and 0, the fracture surface was rough with a large number of small unequiaxed dimples and some tear ridges. Moreover, the localized pores offered a preferential crack path in the samples, where they were surrounded by silicon particles. At a strain ratio of R ɛ = -∞, the fatigue cracks preferentially initiated at pores rather than α-Fe phases. At a strain ratio of R ɛ = 0, where fatigue crack initiation was observed at the interface between plate-like branch of α-Fe phase and aluminum matrix.

  6. Tribological Study on Plasma Electrolytic Oxidation Treatment in Al-Si Alloys for Engine Application

    NASA Astrophysics Data System (ADS)

    Eiliat, Hoda

    Automotive industry strives to reach an optimum level of fuel economy. This can be achieved by overcoming two impacting factors on fuel consumption: weight and friction force. This research contributes to reduce both. The proposed surface treatment can replace cylinder liners of hypoeutectic aluminum silicon alloy engine blocks with a thin layer of ceramic oxide composed of alpha and gamma phases of Al2O3 and mullite. The coatings are achieved in an aqueous electrolytic bath with current densities of 0.1 to 0.2 A/cm2. Coatings produced in silicate based solutions have shown good adaptability to the counter surface with an average 0.12 coefficient of friction. Coatings produced in phosphate and aluminate solution have shown signs of delamination, and excessive porosity and roughness respectively. Coatings produced under Bipolar Pulsed Direct Current mode has up to 12% higher hardness values compared to unipolar coatings. For each increment of 0.2 A/cm2 current density, there is a 30% of increase in coating growth rate. Higher pH values of the solution creates faster growth rate up to 1.5 mu/min. These coatings are 20% more susceptible to wear. Samples treated in MoS2 solution showed 22% lower average roughness values and 37% of reduction in coefficient of friction. Mild wear scars on the piston rings were detected for the optimized coatings.

  7. Microstructural refinement of Al-Si alloy upon ultrasonic nanocrystalline surface modification treatment.

    PubMed

    He, Yinsheng; Li, Kejian; Cho, In Shik; Park, In Gyu; Shin, Keesam

    2014-11-01

    In this work, an Al-7 wt.% Si alloy, which is widely used as the structural materials in the automotive and aerospace industries for their high specific strength, was subjected to ultrasonic nanocrystalline surface modification (UNSM) treatment. After UNSM treatment, the effect of UNSM on the microstructural evolution of both Al grain and the dispersed Si particles was studied by using scanning electron microscope (SEM) and transmission electron microscope (TEM). Experimental results show that the ultra-fine grain (UFG, - 400 nm in size) structure is developed in the top surface layer (up to - 15 μm in depth). The coarse Si particles were refined and well dispersed in the UFG Al matrix. Cross-sectional TEM observation revealed that the grain refinement mechanism involved the formation of new grain boundaries dividing the coarse grain into UFG structure. Nanotwin and nanosize Si were formed within the original coarse Si particles. The presence of dispersed Si particles in the Al matrix accelerated the Al grain refinement process. PMID:25958593

  8. Effect of Viscosity Measurement Method to Simulate High Pressure Die Casting of Thin-Wall AlSi10MnMg Alloy Castings

    NASA Astrophysics Data System (ADS)

    Zhu, B. W.; Li, L. X.; Liu, X.; Zhang, L. Q.; Xu, R.

    2015-12-01

    In the present study, a rotating cylinder viscometer (RCV) was adopted to measure the viscosity of AlSi10MnMg aluminum alloy. The results show that the measured viscosity is much higher than previously reported viscosity of aluminum alloys measured by oscillation vessel viscometer. The viscosity measured by RCV was introduced into the simulation of the filling progress of high pressure die casting (HPDC) for thin-walled castings of aluminum alloy (TWCA). The simulated results match well with the experimental results indicating that the RCV is the most appropriate to use for simulations of HPDC for TWCA.

  9. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  10. Growth Directions of Precipitates in the Al-Si-Mg-Hf Alloy Using Combined EBSD and FIB 3D-Reconstruction Techniques.

    PubMed

    Wang, Xueli; Xing, Yuan; Huang, Huilan; Li, Yanjun; Jia, Zhihong; Liu, Qing

    2015-06-01

    Nanobelt-like precipitates in an Al-Si-Mg-Hf alloy were studied using electron backscattered diffraction (EBSD) and focused ion beam (FIB) scanning electron microscopy techniques. One grain of the Al matrix with a near [111] normal direction was identified by EBSD and the three-dimensional (3D) microstructure of nanobelt-like precipitates in this grain was studied using 3D-FIB. Ten growth directions of the nanobelt-like precipitates in the grain were identified. PMID:25951774

  11. Dendritic Arm Spacing Affecting Mechanical Properties and Wear Behavior of Al-Sn and Al-Si Alloys Directionally Solidified under Unsteady-State Conditions

    NASA Astrophysics Data System (ADS)

    Cruz, Kleber S.; Meza, Elisangela S.; Fernandes, Frederico A. P.; Quaresma, José M. V.; Casteletti, Luiz C.; Garcia, Amauri

    2010-04-01

    Alloys of Al-Sn and Al-Si are widely used in tribological applications such as cylinder liners and journal bearings. Studies of the influence of the as-cast microstructures of these alloys on the final mechanical properties and wear resistance can be very useful for planning solidification conditions in order to permit a desired level of final properties to be achieved. The aim of the present study was to contribute to a better understanding about the relationship between the scale of the dendritic network and the corresponding mechanical properties and wear behavior. The Al-Sn (15 and 20 wt pct Sn) and Al-Si (3 and 5 wt pct Si) alloys were directionally solidified under unsteady-state heat flow conditions in water-cooled molds in order to permit samples with a wide range of dendritic spacings to be obtained. These samples were subjected to tensile and wear tests, and experimental quantitative expressions correlating the ultimate tensile strength (UTS), yield tensile strength, elongation, and wear volume to the primary dendritic arm spacing (DAS) have been determined. The wear resistance was shown to be significantly affected by the scale of primary dendrite arm spacing. For Al-Si alloys, the refinement of the dendritic array improved the wear resistance, while for the Al-Sn alloys, an opposite effect was observed, i.e., the increase in primary dendrite arm spacing improved the wear resistance. The effect of inverse segregation, which is observed for Al-Sn alloys, on the wear resistance is also discussed.

  12. Effect of Particle Size on Microstructure and Cold Compaction of Gas-Atomized Hypereutectic Al-Si Alloy Powder

    NASA Astrophysics Data System (ADS)

    Cai, Zhiyong; Wang, Richu; Peng, Chaoqun; Zhang, Chun

    2015-04-01

    The effect of particle size on the cold compaction behavior of rapidly solidified hypereutectic Al-27 wt pct Si alloy powder was studied by double action axial pressing at room temperature. The geometrical characteristics (morphology, size, shape, and distribution of Si reinforcing phase) and hardness of the powder as a function of the particle size were investigated. The result shows that finer powder particle size showed smaller primary Si particles and achieved a lower density at a given pressure. Whereas, the microhardness of Al matrix increases while the particle size decreases, which indicates that the supersaturation due to the high solidification rate increases the deformation resistance of the alloy powder. Furthermore, the geometrical characteristics of Si phases strongly depend on the particle size due to the suppressed growth of Si phases during atomization. This microstructural characteristic evidently affects the powder compactibility at high applied pressures.

  13. In Situ Study of Microstructure Evolution in Solidification of Hypereutectic Al-Si Alloys with Application of Thermal Analysis and Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Sediako, Dimitry G.; Kasprzak, Wojciech

    2015-09-01

    Understanding of the kinetics of solid-phase evolution in solidification of hypereutectic aluminum alloys is a key to control their as-cast microstructure and resultant mechanical properties, and in turn, to enhance the service characteristics of actual components. This study was performed to evaluate the solidification kinetics for three P-modified hypereutectic Al-19 pct Si alloys: namely, Al-Si binary alloy and with the subsequent addition of 2.8 pct Cu and 2.8 pct Cu + 0.7 pct Mg. Metallurgical evaluation included thermodynamic calculations of the solidification process using the FactSage™ 6.2 software package, as well as experimental thermal analysis, and in situ neutron diffraction. The study revealed kinetics of solid α-Al, solid Si, Al2Cu, and Mg2Si evolution, as well as the individual effects of Cu and Mg alloying additions on the solidification path of the Al-Si system. Various techniques applied in this study resulted in some discrepancies in the results. For example, the FactSage computations, in general, resulted in 281 K to 286 K (8 °C to 13 °C) higher Al-Si eutectic temperatures than the ones recorded in the thermal analysis, which are also ~278 K (~5 °C) higher than those observed in the in situ neutron diffraction. None of the techniques can provide a definite value for the solidus temperature, as this is affected by the chosen calculation path [283 K to 303 K (10 °C to 30 °C) higher for equilibrium solidification vs non-equilibrium] for the FactSage analysis; and further complicated by evolution of secondary Al-Cu and Mg-Si phases that commenced at the end of solidification. An explanation of the discrepancies observed and complications associated with every technique applied is offered in the paper.

  14. Prediction of U-Mo dispersion nuclear fuels with Al-Si alloy using artificial neural network

    NASA Astrophysics Data System (ADS)

    Susmikanti, Mike; Sulistyo, Jos

    2014-09-01

    Dispersion nuclear fuels, consisting of U-Mo particles dispersed in an Al-Si matrix, are being developed as fuel for research reactors. The equilibrium relationship for a mixture component can be expressed in the phase diagram. It is important to analyze whether a mixture component is in equilibrium phase or another phase. The purpose of this research it is needed to built the model of the phase diagram, so the mixture component is in the stable or melting condition. Artificial neural network (ANN) is a modeling tool for processes involving multivariable non-linear relationships. The objective of the present work is to develop code based on artificial neural network models of system equilibrium relationship of U-Mo in Al-Si matrix. This model can be used for prediction of type of resulting mixture, and whether the point is on the equilibrium phase or in another phase region. The equilibrium model data for prediction and modeling generated from experimentally data. The artificial neural network with resilient backpropagation method was chosen to predict the dispersion of nuclear fuels U-Mo in Al-Si matrix. This developed code was built with some function in MATLAB. For simulations using ANN, the Levenberg-Marquardt method was also used for optimization. The artificial neural network is able to predict the equilibrium phase or in the phase region. The develop code based on artificial neural network models was built, for analyze equilibrium relationship of U-Mo in Al-Si matrix.

  15. Prediction of U-Mo dispersion nuclear fuels with Al-Si alloy using artificial neural network

    SciTech Connect

    Susmikanti, Mike; Sulistyo, Jos

    2014-09-30

    Dispersion nuclear fuels, consisting of U-Mo particles dispersed in an Al-Si matrix, are being developed as fuel for research reactors. The equilibrium relationship for a mixture component can be expressed in the phase diagram. It is important to analyze whether a mixture component is in equilibrium phase or another phase. The purpose of this research it is needed to built the model of the phase diagram, so the mixture component is in the stable or melting condition. Artificial neural network (ANN) is a modeling tool for processes involving multivariable non-linear relationships. The objective of the present work is to develop code based on artificial neural network models of system equilibrium relationship of U-Mo in Al-Si matrix. This model can be used for prediction of type of resulting mixture, and whether the point is on the equilibrium phase or in another phase region. The equilibrium model data for prediction and modeling generated from experimentally data. The artificial neural network with resilient backpropagation method was chosen to predict the dispersion of nuclear fuels U-Mo in Al-Si matrix. This developed code was built with some function in MATLAB. For simulations using ANN, the Levenberg-Marquardt method was also used for optimization. The artificial neural network is able to predict the equilibrium phase or in the phase region. The develop code based on artificial neural network models was built, for analyze equilibrium relationship of U-Mo in Al-Si matrix.

  16. Laser cladding of quasi-crystal-forming Al-Cu-Fe-Bi on an Al-Si alloy substrate

    NASA Astrophysics Data System (ADS)

    Biswas, Krishanu; Chattopadhyay, Kamanio; Galun, Rolf; Mordike, Barry L.

    2005-07-01

    We report here the results of an investigation aimed at producing coatings containing phases closely related to the quasi-crystalline phase with dispersions of soft Bi particles using an Al-Cu-Fe-Bi elemental powder mixture on Al-10.5 at. pct Si substrates. A two-step process of cladding followed by remelting is used to fine-tune the alloying, phase distribution, and microstructure. A powder mix of Al64Cu22.3Fe11.7Bi2 has been used to form the clads. The basic reason for choosing Bi lies in the fact that it is immiscible with each of the constituent elements. Therefore, it is expected that Bi will solidify in the form of dispersoids during the rapid solidification. A detailed microstructural analysis has been carried out by using the backscattered imaging mode in a scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructural features are described in terms of layers of different phases. Contrary to our expectation, the quasi-crystalline phase could not form on the Al-Si substrate. The bottom of the clad and remelted layers shows the regrowth of aluminum. The formation of phases such as blocky hexagonal Al-Fe-Si and a ternary eutectic (Al + CuAl2 + Si) have been found in this layer. The middle layer shows the formation of long plate-shaped Al13Fe4 along with hexagonal Al-Fe-Si phase growing at the periphery of the former. The formation of metastable Al-Al6Fe eutectic has also been found in this layer. The top layer, in the case of the as-clad track, shows the presence of plate-shaped Al13Fe4 along with a 1/1 cubic rational approximant of a quasi-crystal. The top layer of the remelted track shows the presence of a significant amount of a 1/1 cubic rational approximant. In addition, the as-clad and remelted microstructures show a fine-scale dispersion of Bi particles of different sizes formed during monotectic solidification. The remelting is found to have a strong effect on the size and distribution of Bi particles. The dry

  17. Simulation of automotive wrist pin joint and tribological studies of tin coated Al-Si alloy, metal matrix composites and nitrogen ceramics under mixed lubrication

    NASA Astrophysics Data System (ADS)

    Wang, Qian

    Development of automotive engines with high power output demands the application of high strength materials with good tribological properties. Metal matrix composites (MMC's) and some nitrogen ceramics are of interest to replace some conventional materials in the piston/pin/connecting rod design. A simulation study has been developed to explore the possibility to employ MMC's as bearing materials and ceramics as journal materials, and to investigate the related wear mechanisms and the possible journal bearing failure mechanisms. Conventional tin coated Al-Si alloy (Al-Si/Sn) have been studied for the base line information. A mixed lubrication model for journal bearing with a soft coating has been developed and applied to the contact and temperature analysis of the Al-Si/Sn bearing. Experimental studies were performed to reveal the bearing friction and wear behavior. Tin coating exhibited great a advantage in friction reduction, however, it suffered significant wear through pitting and debonding. When the tin wore out, the Al-Si/steel contact experienced higher friction. A cast and P/M MMC's in the lubricated contact with case hardened steel and ceramic journals were studied experimentally. Without sufficient material removal in the conformal contact situation, MMC bearings in the MMC/steel pairs gained weight due to iron transfer and surface tribochemical reactions with the lubricant additives and contact failure occurred. However, the MMC/ceramic contacts demonstrated promising tribological behavior with low friction and high wear resistance, and should be considered for new journal bearing design. Ceramics are wear resistant. Ceramic surface roughness is very crucial when the journals are in contact with the tin coated bearings. In contact with MMC bearings, ceramic surface quality and fracture toughness seem to play some important roles in affecting the friction coefficient. The wear of silicon nitride and beta sialon (A) journals is pitting due to grain

  18. A comparative study on wear behavior of TiN and diamond coated WC-Co substrates against hypereutectic Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Chakravarthy, G. V.; Chandran, Maneesh; Bhattacharya, S. S.; Rao, M. S. Ramachandra; Kamaraj, M.

    2012-11-01

    The demand for better tools for machining hypereutectic aluminum-silicon (Al-Si) alloys are increasing day by day since the extensive use of these alloys in internal combustion engines. In addition to the lifetime of the machining tool, surface finish of the machined piece is also equally important, as it directly affects the performance of the engine. In this paper, we compared the wear behavior of bare tungsten carbide (WC-Co), titanium nitride (TiN) coated WC-Co and diamond coated WC-Co substrates against Al-Si alloys using pin-on-disc method. Both TiN and diamond coatings were done using chemical vapor deposition technique. Diamond coated WC-Co substrates show one order less wear loss compared to the bare WC-Co substrates. Instead of weight loss, a weight gain was observed for the TiN coated WC-Co substrates. Average coefficient of friction was lowest for the diamond coated WC-Co substrates due to the different wear behavior of diamond coated tribological system, which is explained in detail.

  19. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    SciTech Connect

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the applied magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.

  20. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

    DOE PAGESBeta

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the appliedmore » magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.« less

  1. Reinforcing aluminum alloys with high strength fibers

    NASA Technical Reports Server (NTRS)

    Kolpashnikov, A. I.; Manuylov, V. F.; Chukhin, B. D.; Shiryayev, Y. V.; Shurygin, A. S.

    1982-01-01

    A study is made of the possibility of reinforcing aluminum and aluminum based alloys with fibers made of high strength steel wire. The method of introducing the fibers is described in detail. Additional strengthening by reinforcement of the high alloy system Al - An - Mg was investigated.

  2. Characteristics of Friction Welding Between Solid Bar of 6061 Al Alloy and Pipe of Al-Si12CuNi Al Cast Alloy

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Sakaguchi, H.; Kusaka, M.; Kaizu, K.; Takahashi, T.

    2015-11-01

    This paper describes the characteristics of friction welding between a solid bar of 6061 Al alloy and a pipe of Al-Si12CuNi (AC8A) Al cast alloy. When the joint was made by a continuous drive friction welding machine (conventional method), the AC8A portion of the joint showed heavy deformation and the AA6061 showed minimal deformation. In particular, the joint could not be successfully made with following conditions, because AC8A pipe side crushed due to insufficient friction heat or high pressure: a short friction time such as 0.3 s, high friction pressure such as 100 MPa, or high forge pressure such as 150 MPa. The heavy deformation of AC8A side was caused by increasing friction torque during braking. To prevent braking deformation until rotation stops, a joint was made by a continuous drive friction welding machine that has an electromagnetic clutch. When the clutch was released, the relative speed between both specimens simultaneously decreased to zero. When the joint was made with friction pressure of 25 MPa, friction time of 0.3 s, and forge pressure of 125 MPa, the joining could be successfully achieved and that had approximately 16% efficiency. In addition, when the joint was made with friction pressure of 25 MPa, friction time of 0.7 s, and forge pressure of 125 MPa, it had approximately 54% efficiency. However, all joints showed the fracture between the traveled weld interface and the AC8A side, because the weld interface traveled in the longitudinal direction of AC8A side from the first contacted position of both weld faying surfaces. Hence, it was clarified that the friction welding between a solid bar of AA6061 and a cast pipe of AC8A was not desirable since the traveling phenomena of the weld interface were caused by the combination of the shapes of the friction welding specimens.

  3. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  4. Application of the Eyring Equation in the Evaluation of Semi-Solid Forming-Induced Si Particle Refinement in the Hypereutectic Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Fukui, Yasuyoshi; Nara, Daisaku; Fushimi, Kazuyo; Kumazawa, Noriyoshi

    2015-12-01

    On the basis of Eyring's theory of absolute reaction rate, an approach to modeling Si particle refinement acceleration in the semi-solid forming of a hypereutectic Al-Si alloy has been developed. The acceleration variable data used in the present analysis were obtained from a semi-solid compression test using Al-25 mass pct Si alloy cylindrical specimens with a diameter of 15 mm and a height of 15 mm; the test conditions comprised a combination of compression displacements ∆ h = 5, 10, and 12 mm; compression rates v = 5, 25, and 125 mm/min; and test temperatures T = 853 K and 863 K (580 °C and 590 °C). The coarse primary Si particle refinement depends on a complex interaction among variables, such as compression displacement, compression rate, and test temperature. The performance of Si particle refinement degraded under higher temperature, slower strain rates, and slower shear rates. The results of the Si particle size are suitably summarized by the Eyring equation as a function of the temperature and the shear rate. The baseline Si particle size and the baseline temperature of Si particle refinement, i.e., the reference temperature, were G N = 0.27 mm and T N = 866.4 K (593.4 °C), respectively. The calculated results using this equation correlated well with the observed results. An acceleration factor of Si particle refinement was successfully derived on the basis of this equation and indicated that operating at a higher shear rate and a temperature just above the melting point of eutectic Al-Si alloy are the optimum conditions for refining Si particles.

  5. Eutectic morphology evolution and Sr-modification in Al-Si based alloys studied by 3D phase-field simulation coupled to Calphad data

    NASA Astrophysics Data System (ADS)

    Eiken, J.; Apel, M.

    2015-06-01

    The mechanical properties of Al-Si cast alloys are mainly controlled by the morphology of the eutectic silicon. Phase-field simulations were carried out to study the evolution of the multidimensional branched eutectic structures in 3D. Coupling to a Calphad database provided thermodynamic data for the multicomponent multiphase Al-Si-Sr-P system. A major challenge was to model the effect of the trace element Sr. Minor amounts of Sr are known to modify the silicon morphology from coarse flakes to fine coral-like fibers. However, the underlying mechanisms are still not fully understood. Two different in literature most discussed mechanisms were modelled: a) an effect of Sr on the growth kinetics of eutectic silicon and b) the formation of Al2Si2Sr on AlP particles, which consumes most potent nucleation sites and forces eutectic silicon to form with lower frequency and higher undercooling. The phase-field simulations only revealed a successful modification of the eutectic morphology when both effects acted in combination. Only in this case a clear depression of the eutectic temperature was observed. The required phase formation sequence L → fcc-(Al) → AlP → Al2Si2Sr → (Si) determines critical values for the Sr and P content.

  6. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    NASA Astrophysics Data System (ADS)

    Bahrami, A.; Pech-Canul, M. I.; Gutiérrez, C. A.; Soltani, N.

    2015-12-01

    A study of the wetting behavior of three substrate types (SiC, SiO2-derived RHA and SiC/SiO2-derived RHA) by two Al-Si-Mg alloys using the sessile drop method has been conducted, using amorphous and crystalline SiO2 in the experiment. Mostly, there is a transition from non-wetting to wetting contact angles, being the lowest θ values achieved with the alloy of high Mg content in contact with amorphous SiO2. The observed wetting behavior is attributed to the deposited Mg on the substrates. A strong diffusion of Si from the SiC/Amorphous RHA substrate into the metal drop explains the free Si segregated at the drop/substrate interface and drop surface. Although incorporation of both SiO2-derived RHA structures into the SiC powder compact substrates increases the contact angles in comparison with the SiC substrate alone, the still observed acute contact angles in RHA/SiC substrates make them promising for fabrication of composites with high volume fraction of reinforcement by the pressureless infiltration technique. The observed wetting characteristics, with decrease in surface tension and contact angles is explained by surface related phenomena. Based on contact angle changes, drop dimensions and surface tension values, as well as on the interfacial elemental mapping, and XRD analysis of substrates, some wetting and reaction pathways are proposed and discussed.

  7. Aging characteristics of the Al-Si-Cu-Mg cast alloy modified with transition metals Zr, V and Ti

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    The hypoeutectic Al-7Si-1Cu-0.5Mg base alloy was modified with different contents of Zr, V and Ti. The wedge-shape samples with varying solidification rates during casting were subjected to isochronal aging at temperatures up to 500 °C. Moreover, as-cast and solution treated alloys were subjected to long-term isothermal aging at 150°C. As a reference, the A380 alloy, seen as commercial standard for the automotive application target, was used. The modified alloys exerted different aging characteristics than the A380 grade with higher peak hardness and lower temperature of alloy softening. Besides, the influence of the applied solidification rates on hardness after aging was less pronounced in modified alloys than in the A380 grade. For three combinations of Zr, V and Ti tested with contents of individual elements ranging from 0.14 to 0.47%, no essential differences in aging characteristics were recorded. The results are discussed in terms of the role of chemistry and heat treatment in generating precipitates contributing to the thermal stability of Al based alloys.

  8. Effect of strontium modification on near-threshold fatigue crack growth in an Al-Si-Cu die cast alloy

    SciTech Connect

    Schaefer, M.; Fournelle, R.A.

    1996-05-01

    The effects of strontium modification on microstructure and fatigue properties in a die cast commercial aluminum-silicon alloy are demonstrated. Strontium additions of 0.010 and 0.018 wt pct drastically change the morphology of the eutectic silicon. The influence of these microstructural changes on fatigue properties is evaluated through fatigue crack growth testing. Examination of the fracture surfaces and the crack path establish distinct fatigue fracture modes for the modified and unmodified eutectic structures. Changes in fracture mode and crack path are correlated to the microstructure changes. A higher energy fracture mode and increased crack path tortuosity explain the observed improvement in fatigue properties for the modified alloys. Strontium modified alloys exhibit a 10 to 20 pct higher fatigue crack growth threshold compared to an unmodified alloy for testing at a load ratio of 0.5. No difference was observed for testing at a load ratio of 0.1.

  9. 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.

  10. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  11. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  12. 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.

  13. Electronic, magnetic and thermal properties of Co2CrxFe1-xX (X=Al, Si) Heusler alloys: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Guezlane, M.; Baaziz, H.; El Haj Hassan, F.; Charifi, Z.; Djaballah, Y.

    2016-09-01

    Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co2CrxFe1-xX (X=Al, Si) full Heusler alloys, with L21 structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel-Vosko generalized gradient approximation (EVGGA) and modified Becke-Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co2CrxFe1-xX that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions.

  14. The Effects of Microstructure Heterogeneities and Casting Defects on the Mechanical Properties of High-Pressure Die-Cast AlSi9Cu3(Fe) Alloys

    NASA Astrophysics Data System (ADS)

    Timelli, Giulio; Fabrizi, Alberto

    2014-11-01

    Detailed investigations of the salient microstructural features and casting defects of the high-pressure die-cast (HPDC) AlSi9Cu3(Fe) alloy are reported. These characteristics are addressed to the mechanical properties and reliability of separate HPDC tensile bars. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes throughout the tensile specimen. The results indicate that the die-cast microstructure consists of several microstructural heterogeneities such as positive eutectic segregation bands, externally solidified crystals (ESCs), cold flakes, primary Fe-rich intermetallics (sludge), and porosities. In addition, it results that sludge particles, gas porosity, as well as ESCs, and cold flakes are concentrated toward the casting center while low porosity and fine-grained structure is observed on the surface layer of the castings bars. The local variation of the hardness along the cross section as well as the change of tensile test results as a function of gage diameter of the tensile bars seem to be ascribed to the change of porosity content, eutectic fraction, and amount of sludge. Further, this behavior reflects upon the reliability of the die-cast alloy, as evidenced by the Weibull statistics.

  15. Evaluation of the Deformation Behavior of a Semi-solid Hypereutectic Al-Si Alloy Compressed in a Drop-Forge Viscometer

    NASA Astrophysics Data System (ADS)

    Fukui, Yasuyoshi; Nara, Daisaku; Kumazawa, Noriyoshi

    2015-05-01

    The rheological behavior of an Al-25 mass pct Si alloy, i.e., a hypereutectic Al-Si alloy, was investigated to determine its processability under semi-solid forming conditions. To measure the viscosity of the semi-solid alloy, a parallel-plate drop-forge viscometer similar to that devised by Yurko and Flemings was developed. Drop-forge experiments revealed that the viscosity initially decreased as the shear rate increased and subsequently increased as the shear rate decreased. Thus, the viscosity reached a minimum at approximately the maximum shear rate. The summarized relationship between the viscosity, μ [Pa s], and the shear rate, [s-1], can be described by the power-law model μ = 1.78 × 107 -1.5. The decrease in viscosity as a function of the shear rate derived from this equation depends on both the temperature and the applied force but not the duration of deformation. A convex curve was obtained when the effective duration of deformation, i.e., the actual compression time, was plotted as a function of the viscosity and the effective duration of deformation reached a maximum at approximately μ = 30 kPa s ( = 70 s-1). The origin of this profile can be attributed to a combination of both a moderate working time and an adequate deformation, which resulted from a decrease in the deformation resistance accompanied by a lowering of the viscosity. The viscosity at the maximum effective duration of deformation thus corresponds to the transition point for the change in the flow process dominant factor from plastic forming (forging) to casting. Therefore, the viscosity μ = 30 kPa s is believed to be the optimum viscosity for the semi-solid forming of the Al-25 mass pct Si alloy. The approximate temperature condition can be ranged from 855 K to 859 K (582 °C to 586 °C).

  16. Role of Si on the Diffusional Interactions between U-Mo and Al-Si Alloys at 823 K (550 degrees C)

    SciTech Connect

    E. Perez; Y.H. Sohn; D.D. Keiser, Jr.

    2013-01-01

    U-Mo dispersions in Al-alloy matrix and monolithic fuels encased in Al-alloy are under development to fulfill the requirements for research and test reactors to use low-enriched molybdenum stabilized uranium alloys fuels. Significant interaction takes place between the U-Mo fuel and Al during manufacturing and in-reactor irradiation. The interactions products are Al-rich phases with physical and thermal characteristics that adversely affect fuel performance and lead to premature failure. Detailed analysis of the interdiffusion and microstructural development of this system was carried through diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo in contact with pure Al, Al-2wt.%Si, and Al-5wt.%Si, annealed at 823K for 1, 5 and 20 hours. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for the analysis. Diffusion couples consisting of U-Mo vs. pure Al contained UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases. The addition of Si to the Al significantly reduced the thickness of the interdiffusion zone. The interdiffusion zones developed Al and Si enriched regions, whose locations and size depended on the Si and Mo concentrations in the terminal alloys. In the couples, the (U,Mo)(Al,Si)3 phase was observed throughout interdiffusion zone, and the U6Mo4Al43 and UMo2Al20 phases were observed only where the Si concentrations were low.

  17. Effect of Different Production Methods on the Mechanical and Microstructural Properties of Hypereutectic Al-Si Alloys

    NASA Astrophysics Data System (ADS)

    Fatih Kilicaslan, M.; Uzun, Orhan; Yilmaz, Fikret; Çağlar, Seyit

    2014-10-01

    In this study, the effects of different production methods like melt spinning, high-energy ball milling, and combined melt spinning and high-energy ball milling on the mechanical and microstructural properties of hypereutectic Al-20Si-5Fe alloys were investigated. While microstructural and spectroscopic analyses were performed using scanning electron microscopy and X-ray diffractometry, mechanical properties were measured using a depth-sensing indentation instrument with a Berkovich tip. Microstructural and spectroscopic analyses demonstrate that high-energy ball milling process applied on the melt-spun Al-20-Si-5Fe alloy for 10 minutes brings about a reduction in the size of silicon particles and intermetallic compounds. However, further increase in milling time does not yield any significant reduction in size. High-energy ball milling for 10 minutes on the starting powders is not enough to form any intermetallic phase. According to the depth-sensing indentation experiments, high-energy milling of melt-spun Al-20Si-5Fe alloys shows an incremental behavior in terms of hardness values. For the Al-20Si-5Fe alloys investigated in this study, the production technique remarkably influences their elastic-plastic response to the indentation process in terms of both magnitude and shape of P- h curves.

  18. Morphologies of Primary Silicon in Hypereutectic Al-Si Alloys: Phase-Field Simulation Supported by Key Experiments

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Wei, Ming; Zhang, Lijun; Du, Yong

    2016-04-01

    We realized a three-dimensional visualization of the morphology evolution and the growth behavior of the octahedral primary silicon in hypereutectic Al-20wtpctSi alloy during solidification in a real length scale by utilizing the phase-field simulation coupled with CALPHAD databases, and supported by key experiments. Moreover, through two-dimensional cut of the octahedral primary silicon at random angles, different morphologies observed in experiments, including triangle, square, trapezoid, rhombic, pentagon, and hexagon, were well reproduced.

  19. Effect of Stress Ratio on the Fatigue Behavior of a Friction Stir Processed Cast Al-Si-Mg Alloy

    SciTech Connect

    Jana, Saumyadeep; Mishra, Rajiv S.; Baumann, John B.; Grant, Glenn J.

    2009-11-01

    The effect of friction stir processing (FSP) on the fatigue life of a cast Al-7Si-0.6Mg alloy at a stress ratio of R=0 was evaluated. Two types of specimen geometry were used for the FSPed condition, through-thickness processed and partial thickness processed. FSP enhanced the fatigue life by a factor of 15 for the through thickness processed samples at lower stress amplitudes. This is different from the FSP specimens tested at R=-1 and similar stress amplitudes where a 5 times improvement in fatigue life was observed. In light of these observations, various closure mechanisms were examined.

  20. Investigation of the Phase Formation of AlSi-Coatings for Hot Stamping of Boron Alloyed Steel

    NASA Astrophysics Data System (ADS)

    Veit, R.; Hofmann, H.; Kolleck, R.; Sikora, S.

    2011-01-01

    Hot stamping of boron alloyed steel is gaining more and more importance for the production of high strength automotive body parts. Within hot stamping of quenchenable steels the blank is heated up to austenitization temperature, transferred to the tool, formed rapidly and quenched in the cooled tool. To avoid scale formation during the heating process of the blank, the sheet metal can be coated with an aluminium-silicum alloy. The meltimg temperature of this coating is below the austenitization temperature of the base material. This means, that a diffusion process between base material and coating has to take place during heating, leading to a higher melting temperature of the coating. In conventional heating devices, like roller hearth furnaces, the diffusion process is reached by relatively low heating rates. New technologies, like induction heating, reach very high heating rates and offer great potentials for the application in hot stamping. Till now it is not proofed, that this technology can be used with aluminum-silicon coated materials. This paper will present the results of comparative heating tests with a conventional furnace and an induction heating device. For different time/temperature-conditions the phase formation within the coating will be described.

  1. SDAS, Si and Cu Content, and the Size of Intermetallics in Al-Si-Cu-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Sivarupan, Tharmalingam; Taylor, John Andrew; Cáceres, Carlos Horacio

    2015-05-01

    Plates of Al-(a)Si-(b)Cu-Mg-(c)Fe alloys with varying content of (mass pct) Si ( a = 3, 4.5, 7.5, 9, 10, or 11), Cu ( b = 0, 1, or 4), and Fe ( c = 0.2, 0.5 or 0.8) were cast in sand molds with a heavy chill at one end to ensure quasi-directional solidification over a wide range of Secondary Dendrite Arm Spacing (SDAS). Statistical analysis on the size of the β-Al5FeSi, α-Al8Fe2Si, or Al2Cu intermetallics on Backscattered Electron images showed that a high Si content reduced the size of the β platelets in alloys with up to 0.5 Fe content regardless of the SDAS, whereas at small SDAS the refining effect extended up to 0.8 Fe, and involved α-phase intermetallics which replaced the beta platelets at those concentrations. At low Si contents, a high Cu level appeared to have similar refining effects as increased Si, through the formation of α-phase particles in the post-eutectic stage which agglomerated with the Al2Cu intermetallics. A high content of Si appears to make the overall refining process less critical in terms of SDAS/cooling rate.

  2. Investigation of the Phase Formation of AlSi-Coatings for Hot Stamping of Boron Alloyed Steel

    SciTech Connect

    Veit, R.; Kolleck, R.; Hofmann, H.; Sikora, S.

    2011-01-17

    Hot stamping of boron alloyed steel is gaining more and more importance for the production of high strength automotive body parts. Within hot stamping of quenchenable steels the blank is heated up to austenitization temperature, transferred to the tool, formed rapidly and quenched in the cooled tool. To avoid scale formation during the heating process of the blank, the sheet metal can be coated with an aluminium-silicum alloy. The meltimg temperature of this coating is below the austenitization temperature of the base material. This means, that a diffusion process between base material and coating has to take place during heating, leading to a higher melting temperature of the coating.In conventional heating devices, like roller hearth furnaces, the diffusion process is reached by relatively low heating rates. New technologies, like induction heating, reach very high heating rates and offer great potentials for the application in hot stamping. Till now it is not proofed, that this technology can be used with aluminum-silicon coated materials. This paper will present the results of comparative heating tests with a conventional furnace and an induction heating device. For different time/temperature-conditions the phase formation within the coating will be described.

  3. Electrochemical properties of the ternary alloy Li5AlSi2 synthesized by reacting LiH, Al and Si as an anodic material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Yongfeng; Yan, Ping; Ma, Ruijun; Gao, Mingxia; Pan, Hongge

    2015-06-01

    The ternary alloy Li5AlSi2 is successfully synthesized by a hydrogen-driven chemical reaction at 500-650 °C and used as an anode for Li-ion batteries. It is observed that a higher dehydrogenation temperature induces a higher phase purity and a larger particle size and that the Li5AlSi2 prepared at 600 °C exhibits the best electrochemical properties. The Li5AlSi2 prepared at 600 °C delivers a Li-extraction capacity of approximately 849 mAh/g at 100 mA/g via a two-step reaction in the first charge cycle, corresponding to 3.8 mol Li ions. More interestingly, the Li-insertion capacity of the delithiated sample reaches 1303 mAh/g during the subsequent discharge process, much higher than the previous Li-extraction capacity. The capacity retention is determined to be approximately 59% after 25 cycles, which is superior to that of the sample prepared by the conventional melting technique. Structural analyses and CV measurements reveal that the active lithium storage species is converted to the amorphous Li-Si and Li-Al alloys instead of the initial Li5AlSi2 after 1 charge/discharge cycle, which is believed to be the most important reason for the rapid capacity fading upon cycling.

  4. Effect of Thermal and Chemical Treatment on the Microstructural, Mechanical and Machining Performance of W319 Al-Si-Cu Cast Alloy Engine Blocks and Directionally Solidified Machinability Test Blocks

    NASA Astrophysics Data System (ADS)

    Szablewski, Daniel

    The research presented in this work is focused on making a link between casting microstructural, mechanical and machining properties for 319 Al-Si sand cast components. In order to achieve this, a unique Machinability Test Block (MTB) is designed to simulate the Nemak V6 Al-Si engine block solidification behavior. This MTB is then utilized to cast structures with in-situ nano-alumina particle master alloy additions that are Mg based, as well as independent in-situ Mg additions, and Sr additions to the MTB. The Universal Metallurgical Simulator and Analyzer (UMSA) Technology Platform is utilized for characterization of each cast structure at different Secondary Dendrite Arm Spacing (SDAS) levels. The rapid quench method and Jominy testing is used to assess the capability of the nano-alumina master alloy to modify the microstructure at different SDAS levels. Mechanical property assessment of the MTB is done at different SDAS levels on cast structures with master alloy additions described above. Weibull and Quality Index statistical analysis tools are then utilized to assess the mechanical properties. The MTB is also used to study single pass high speed face milling and bi-metallic cutting operations where the Al-Si hypoeutectic structure is combined with hypereutectoid Al-Si liners and cast iron cylinder liners. These studies are utilized to aid the implementation of Al-Si liners into the Nemak V6 engine block and bi-metallic cutting of the head decks. Machining behavior is also quantified for the investigated microstructures, and the Silicon Modification Level (SiML) is utilized for microstructural analysis as it relates to the machining behavior.

  5. DOE applied to study the effect of process parameters on silicon spacing in lost foam Al-Si-Cu alloy casting

    NASA Astrophysics Data System (ADS)

    Shayganpour, A.; Idris, M. H.; Izman, S.; Jafari, H.

    2012-09-01

    Lost foam casting as a relatively new manufacturing process is extensively employed to produce sound complicated castings. In this study, an experimental investigation on lost foam casting of an Al-Si-Cu aluminium cast alloy was conducted. The research was aimed in evaluating the effect of different pouring temperatures, slurry viscosities, vibration durations and sand grain sizes on eutectic silicon spacing of thin-wall castings. A stepped-pattern was used in the study and the focus of the investigations was at the thinnest 3 mm section. A full two-level factorial design experimental technique was used to plan the experiments and afterwards identify the significant factors affecting casting silicon spacing. The results showed that pouring temperature and its interaction with vibration time have pronounced effect on eutectic silicon phase size. Increasing pouring temperature coarsened the eutectic silicon spacing while the higher vibration time diminished coarsening effect. Moreover, no significant effects on silicon spacing were found with variation of sand size and slurry viscosity.

  6. Effect of interface layer on the microstructure and electromigration resistance of Al-Si-Cu alloy on TiN/Ti substrates

    NASA Astrophysics Data System (ADS)

    Olowolafe, J. O.; Kawasaki, H.; Lee, C. C.; Klein, J.; Pintchovski, F.; Jawarani, D.

    1993-05-01

    Al-Si-Cu alloy films sputter-deposited on reactively ion-sputtered TiN/Ti/SiO2 substrates were characterized and evaluated for interconnect reliability. Using x-ray diffraction techniques, both TiN and Al microstructures were analyzed and the (111) intensities of the latter correlated with the electromigration median time to fail (MTTF). The values of the MTTF increased with the Al(111) intensities for the TiN/Ti/SiO2 substrates annealed below 400 °C. A progressive decrease in both the Al(111) texture and MTTF was observed for substrates annealed above this temperature. While the improved Al(111) texture has been attributed to an improved TiN barrier textured in the (111) crystal plane (anneals below 400 °C), a TiO2 layer over the TiN barrier has been found responsible for the degradation of the Al(111) texture and the MTTF for barrier anneals above 400 °C.

  7. Multiscale modeling of the influence of Fe content in a Al-Si-Cu alloy on the size distribution of intermetallic phases and micropores

    NASA Astrophysics Data System (ADS)

    Wang, Junsheng; Li, Mei; Allison, John; Lee, Peter D.

    2010-03-01

    A multiscale model was developed to simulate the formation of Fe-rich intermetallics and pores in quaternary Al-Si-Cu-Fe alloys. At the microscale, the multicomponent diffusion equations were solved for multiphase (liquid-solid-gas) materials via a finite difference framework to predict microstructure formation. A fast and robust decentered plate algorithm was developed to simulate the strong anisotropy of the solid/liquid interfacial energy for the Fe-rich intermetallic phase. The growth of porosity was controlled by local pressure drop due to solidification and interactions with surrounding solid phases, in addition to hydrogen diffusion. The microscale model was implemented as a subroutine in a commercial finite element package, producing a coupled multiscale model. This allows the influence of varying casting conditions on the Fe-rich intermetallics, the pores, and their interactions to be predicted. Synchrotron x-ray tomography experiments were performed to validate the model by comparing the three-dimensional morphology and size distribution of Fe-rich intermetallics as a function of Fe content. Large platelike Fe-rich β intermetallics were successfully simulated by the multiscale model and their influence on pore size distribution in shape castings was predicted as a function of casting conditions.

  8. Effects of metallurgical parameters on the decomposition of pi-AlFeMgSi phase in Al-Si-Mg alloys and its influence on the mechanical properties

    NASA Astrophysics Data System (ADS)

    Elsharkawi, Ehab A.

    2011-12-01

    The formation of the pi-AlFeMgSi iron intermetallic phase in Al-Si-Mg alloys is known for its detrimental effect on ductility and strength, in that it is controlled by the Fe and Mg content of the alloy, as well as by the cooling rate. The current study was carried out with a view to investigating all the metallurgical parameters affecting the formation of the pi-phase iron intermetallic and, in turn, the role of the pi-phase as it relates to the tensile and impact properties of Al-Si-Mg alloys. Microstructural assessment was carried out by means of quantitative metallography using electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). The results indicate that increasing the Mg and Fe content increases the amount of the pi-AlMgFeSi phase formed. All the alloys containing low levels of iron regardless of the amount of Mg-content show low amounts of pi-phase iron intermetallic. The addition of trace amounts of Be has an observable effect in reducing the amount of the pi-phase formed in all the alloys studied. The pi-phase iron intermetallic particles appear to be segregated away from the modified Si in the Sr-modified alloys, particularly those solidified at a low cooling rate. The effects of different solution treatment times on the decomposition of the pi-phase were investigated in order to examine how this type of decomposition affected the chemistry of the matrix itself. After 8 hours of solution heat treatment and at Mg content of 0.4wt%, the pi-phase showed complete decomposition into fine beta-phase needles. The a-phase, however, showed only partial decomposition into beta-AlFeSi phase needles at Mg levels of over 0.4%wt. This type of decomposition was examined for the purposes of this study over extended periods of solution heat treatment time in Al-7Si-0.55Mg-0.1Fe alloy samples obtained at different cooling rates in order to evaluate the mechanism of pi to beta-phase decomposition. The results obtained show that the volume fraction of

  9. Effects of La addition on the microstructure and tensile properties of Al-Si-Cu-Mg casting alloys

    NASA Astrophysics Data System (ADS)

    Lu, Tao; Pan, Ye; Wu, Ji-li; Tao, Shi-wen; Chen, Yu

    2015-04-01

    The effects of La addition on the microstructure and tensile properties of B-refined and Sr-modified Al-11Si-1.5Cu-0.3Mg casting alloys were investigated. With a trace addition of La (0.05wt%-0.1wt%), the mutual poisoning effect between B and Sr can be neutralized by the formation of LaB6 rather than SrB6. By employing a La/B weight ratio of 2:1, uniform microstructures, which are characterized by well refined α-Al grains and adequately modified eutectic Si particles as well as the incorporation of precipitated strengthening intermetallics, are obtained and lead to appreciable tensile properties with an ultimate tensile strength of 270 MPa and elongation of 5.8%.

  10. Reconstruction and Quantitative Characterization of Multiphase, Multiscale Three-Dimensional Microstructure of a Cast Al-Si Base Alloy

    NASA Astrophysics Data System (ADS)

    Singh, H.; Gokhale, A. M.; Mao, Y.; Tewari, A.; Sachdev, A. K.

    2009-12-01

    The serial sectioning technique is well known for the reconstruction of three-dimensional (3D) microstructures of opaque materials. In recent years, techniques also have been developed for the reconstruction of high-fidelity, large-volume segments of 3D microstructures that use montage serial sections and robot-assisted automated acquisitions of montage serial sections. This article reports the reconstruction of the multiphase, multiscale 3D microstructure of a permanent mold cast unmodified Al-12 wt pct Si-1 wt pct Ni base alloy that contains eutectic Si platelets, coarse primary polyhedral Si particles, Fe-rich script intermetallic particles, and pores. These constituents are segmented, reconstructed, rendered, and characterized in three dimensions. The estimated 3D microstrucutral attributes include the distribution of eutectic platelet thickness; the mean volume, mean surface area, and mean thickness of the eutectic Si platelets; the mean volume and the mean surface area of the polyhedral primary Si particles; and the mean number of faces, edges, and corners on the polyhedral primary Si particles.

  11. Kinetic Analyses of the Growth and Dissolution Phenomena of Primary Si and α-Al in Partially Molten Al-Si (-Cu-Mg) Alloy Particles Using In Situ Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Eswara Moorthy, Santhana K.; Howe, James M.

    2011-06-01

    The growth and dissolution behavior of primary Si and α-Al in partially molten hypereutectic Al-Si-based alloy particles was investigated using in situ TEM to reveal the dynamic and instantaneous processes occurring during these phenomena. Direct evidence for the preferential growth of Si {113} facets compared with {111} facets resulting in prominent {111} facets bounding the Si crystals was obtained. The nucleation of primary Si was found to occur heterogeneously on the encapsulating alumina shell, whereas the α-Al phase nucleated homogeneously from the liquid Al-Si phase. The morphology of primary Si during growth was found to be highly faceted during growth but smoothly curved during dissolution, revealing fundamental mechanistic differences during these processes. We provide a ledge-based interpretation to explain the difference in growth and dissolution behavior. The α-Al phase displayed smoothly curved growth and dissolution morphologies, which are characteristic of an isotropic interfacial energy and a continuous growth mechanism.

  12. Influence of heat treatment on tribological properties of electroless Ni-P and Ni-P-Al 2O 3 coatings on Al-Si casting alloy

    NASA Astrophysics Data System (ADS)

    Novák, M.; Vojtěch, D.; Vítů, T.

    2010-02-01

    Evolution of tribological properties of electroless Ni-P and Ni-P-Al 2O 3 coating on an Al-10Si-0.3Mg casting alloy during heat treatment is investigated in this work. The pre-treated substrate was plated using a bath containing nickel hypophosphite, nickel lactate and lactic acid. For preparation of fiber-reinforced coating Al 2O 3 Saffil fibers pre-treated in demineralised water were used. The coated samples were heat treated at 400-550 °C/1-8 h. Tribological properties were studied using the pin-on-disc method. It is found that the best coating performance is obtained using optimal heat treatment regime (400 °C/1 h). Annealing at higher temperatures (450 °C and above) leads to the formation of intermetallic compounds that reduce the coating wear resistance. The reason is that the intermetallic phases adversely affect the coating adherence to the substrate. The analysis of wear tracks proves that abrasion is major wear mechanism, however due to the formed intermetallic sub-layers, partial coating delamination may occur during the pin-on-disc test on the samples annealed at 450 °C and above. It was found that fiber reinforcement reduces this scaling and increases wear resistance of coatings as compared to the non-reinforced Ni-P coatings.

  13. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  14. In-situ processing of aluminum nitride particle reinforced aluminum alloy composites

    NASA Astrophysics Data System (ADS)

    Zheng, Qingjun

    Discontinuously reinforced aluminum alloy composites (DRACs) have potential applications in automotive, electronic packaging, and recreation industries. Conventional processing of DRACs is by incorporation of ceramic particles/whiskers/fibers into matrix alloys. Because of the high cost of ceramic particles, DRACs are expensive. The goal of this work was to develop a low-cost route of AlN-Al DRACs processing through bubbling and reacting nitrogen and ammonia gases with aluminum alloy melt in the temperature range of 1373--1523 K. Thermodynamic analysis of AlN-Al alloy system was performed based on Gibbs energy minimization theory. AlN is stable in aluminum, Al-Mg, Al-Si, Al-Zn, and Al-Li alloys over the whole temperature range for application and processing of DRACs. Experiments were carried out to form AlN by bubbling nitrogen and ammonia gases through aluminum, Al-Mg, and Al-Si alloy melts. Products were characterized with XRD, SEM, and EDX. The results showed that in-situ processing of AlN reinforced DRACs is technically feasible. Significant AlN was synthesized by bubbling deoxidized nitrogen and ammonia gases. When nitrogen gas was used as the nitrogen precursor, the AlN particles formed in-situ are small in size, (<10 mum). The formation of AlN is strongly affected by the trace oxygen impurities in the nitrogen gas. The deleterious effect of oxygen impurities is due to their inhibition to the chemisorption of nitrogen gas at the interface. In comparison with nitrogen gas, bubbling ammonia led to formation of AlN particles in smaller size (about 2 mum or less) at a significantly higher rate. Ammonia is not stable and dissociated into nitrogen and hydrogen at reaction temperatures. The hydrogen functions as oxygen-getter at the interface and benefits chemisorption of nitrogen, thereby promoting the formation of AlN. The overall process of AlN formation was modeled using two-film model. For nitrogen bubbling gas, the whole process is controlled by chemisorption

  15. Mechanism of Corrosion in Al-Si-Cu

    NASA Astrophysics Data System (ADS)

    Hayasaka, Nobuo; Koga, Yuri; Shimomura, Koji; Yoshida, Yukimasa; Okano, Haruo

    1991-07-01

    An Al-Cu local cell was formed between the Cu precipitation and adjacent Al in an Al-Si-Cu alloy when Cu was added in excess to the alloy. Once an Al-Cu local cell was formed, corrosion took place simply by dipping the alloy in deionized water without any contamination. Furthermore, it was found that corrosion was enhanced at the Al-Si-Cu lines in contact with the p+-n junction of Si. The reason for this is that holes are injected into Al-Si-Cu from p+-Si due to electromotive force produced by light irradiation and an external circuit connecting the alloy and n-Si formed by the adsorption of moisture on the surface. Furthermore, it was found that the irradiation of light with a wavelength between 320 to 380 nm was most effective in enhancing the corrosion reaction.

  16. Effect of internal stresses and microstructure of sputtered TiN films on solid-phase reactions with Al-Si-Cu alloy films

    NASA Astrophysics Data System (ADS)

    Yamauchi, T.; Yamaoka, T.; Yashiro, K.; Sobue, S.

    1995-08-01

    Solid-phase reactions at the interface between Al-Si-Cu and reactively sputtered TiN thin films have been investigated by cross-sectional transmission electron microscopy, Auger electron spectroscopy, and x-ray diffraction. In the case in which the internal stress in the TiN thin film is extremely compressive at 209 MPa, a very thin amorphous Al-Ti-Si ternary compound layer (a-Al-Ti-Si) containing microcrystallites, about 4 nm thick, is found to form at the Al-Si-Cu/TiN interface by annealing at the temperature of 450 °C for 30 min. On the other hand, in the case of a minimally compressive stress of 21 MPa, it is in a marked contrast to form a polycrystalline TiAl3 layer (c-TiAl3) on the amorphous intermediate layer ununiformly. Behavior of the internal stress in the latter TiN film as a function of heating and cooling temperature shows nonlinear characteristics, indicating that a rearrangement of the TiN film actively occurs even at low temperatures below 300 °C. Monte Carlo simulations of internal microstructures based on a ballistic aggregation model suggest to us that a short migration length corresponding to the condition of low internal stress brings about numerous vacancies and disordered regions in the TiN films. It is considered that the rearrangement of the TiN films with a diffusion of Ti atoms governs the solid-phase reactions at the Al-Si-Cu/TiN interfaces and that the formation of the bilayer of c-TiAl3/a-Al-Ti-Si originates in phase separation of the resultant Al-Ti mixing layer.

  17. Studies of waste-canister compatibility. [Waste forms: Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus SiC

    SciTech Connect

    McCoy, H.E.

    1983-01-01

    Compatibility studies were conducted between 7 waste forms and 15 potential canister structural materials. The waste forms were Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus silicon carbide. The canister materials included carbon steel (bare and with chromium or nickel coatings), copper, Monel, Cu-35% Ni, titanium (grades 2 and 12), several Inconels, aluminum alloy 5052, and two stainless steels. Tests of either 6888 or 8821 h were conducted at 100 and 300/sup 0/C, which bracket the low and high limits expected during storage. Glass and FUETAP evolved sulfur, which reacted preferentially with copper, nickel, and alloys of these metals. The Pb-Sn matrix alloy stuck to all samples and the carbon-coated particles to most samples at 300/sup 0/C, but the extent of chemical reaction was not determined. Testing for 0.5 h at 800/sup 0/C was included because it is representative of a transportation accident and is required of casks containing nuclear materials. During these tests (1) glass and FUETAP evolved sulfur, (2) FUETAP evolved large amounts of gas, (3) Synroc stuck to titanium alloys, (4) glass was molten, and (5) both matrix alloys were molten with considerable chemical interactions with many of the canister samples. If this test condition were imposed on waste canisters, it would be design limiting in many waste storage concepts.

  18. Development and characterization of Powder Metallurgy (PM) 2XXX series Al alloy products and Metal Matrix Composite (MMC) 2XXX Al/SiC materials for high temperature aircraft structural applications

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.; Gurganus, T. B.; Walker, J. A.

    1992-01-01

    The results of a series of material studies performed by the Lockheed Aeronautical Systems Company over the time period from 1980 to 1991 are discussed. The technical objective of these evaluations was to develop and characterize advanced aluminum alloy materials with temperature capabilities extending to 350 F. An overview is given of the first five alloy development efforts under this contract. Prior work conducted during the first five modifications of the alloy development program are listed. Recent developments based on the addition of high Zr levels to an optimum Al-Cu-Mg alloy composition by powder metallurgy processing are discussed. Both reinforced and SiC or B4C ceramic reinforced alloys were explored to achieve specific target goals for high temperature aluminum alloy applications.

  19. Compressive strength of the mineral reinforced aluminium alloy composite

    NASA Astrophysics Data System (ADS)

    Arora, Rama; Sharma, Anju; Kumar, Suresh; Singh, Gurmel; Pandey, O. P.

    2016-05-01

    This paper presents the results of quasi-static compressive strength of aluminium alloy reinforced with different concentration of rutile mineral particles. The reinforced material shows increase in compressive strength with 5wt% rutile concentration as compared to the base alloy. This increase in compressive strength of composite is attributed to direct strengthening due to transfer of load from lower stiffness matrix (LM13 alloy) to higher stiffness reinforcement (rutile particles). Indirect strengthening mechanisms like increase in dislocation density at the matrix-reinforcement interface, grain size refinement of the matrix and dispersion strengthening are also the contributing factors. The decrease in compressive strength of composite with the increased concentration of rutile concentration beyond 5 wt.% can be attributed to the increase in dislocation density due to the void formation at the matrix-reinforcement interface.

  20. X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

    NASA Astrophysics Data System (ADS)

    Mathiesen, R. H.; Arnberg, L.; Li, Y.; Meier, V.; Schaffer, P. L.; Snigireva, I.; Snigirev, A.; Dahle, A. K.

    2011-01-01

    Al-Si eutectic growth has been studied in-situ for the first time using X-ray video microscopy during directional solidification (DS) in unmodified and Sr-modified Al-Si-Cu alloys. In the unmodified alloys, Si is found to grow predominantly with needle-like tip morphologies, leading a highly irregular progressing eutectic interface with subsequent nucleation and growth of Al from the Si surfaces. In the Sr-modified alloys, the eutectic reaction is strongly suppressed, occurring with low nucleation frequency at undercoolings in the range 10 K to 18 K. In order to transport Cu rejected at the eutectic front back into the melt, the modified eutectic colonies attain meso-scale interface perturbations that eventually evolve into equiaxed composite-structure cells. The eutectic front also attains short-range microscale interface perturbations consistent with the characteristics of a fibrous Si growth. Evidence was found in support of Si nucleation occurring on potent particles suspended in the melt. Yet, both with Sr-modified and unmodified alloys, Si precipitation alone was not sufficient to facilitate the eutectic reaction, which apparently required additional undercooling for Al to form at the Si-particle interfaces.

  1. Mechanical Properties of Particulate Reinforced Aluminium Alloy Matrix Composite

    SciTech Connect

    Sayuti, M.; Sulaiman, S.; Baharudin, B. T. H. T.; Arifin, M. K. A.; Suraya, S.; Vijayaram, T. R.

    2011-01-17

    This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium-silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.

  2. Application of X-ray microtomography to study the influence of the casting microstructure upon the tensile behaviour of an Al-Si alloy

    NASA Astrophysics Data System (ADS)

    Limodin, Nathalie; El Bartali, Ahmed; Wang, Long; Lachambre, Joël; Buffiere, Jean-Yves; Charkaluk, Eric

    2014-04-01

    In cast aluminium alloys used in the automotive industry the microstructure inherited from the foundry process has a strong influence on the mechanical properties. In the cylinder heads produced by the Lost Foam Casting process, the microstructure consists of hard intermetallic phases and large gas and microshrinkage pores. To study its influence, full field measurements at the microstructure scale were performed during a tensile test performed in situ under X-ray microtomography. Intermetallics were used as a natural speckle pattern. Feasibility of Digital Volume Correlation on this alloy was proved and the accuracy of the measurement was assessed and discussed in light of the small volume fraction of intermetallics and in comparison with the accuracy of Digital Image Correlation performed on optical images at a finer spatial resolution.

  3. Fabrication of tungsten wire reinforced nickel-base alloy composites

    NASA Technical Reports Server (NTRS)

    Brentnall, W. D.; Toth, I. J.

    1974-01-01

    Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.

  4. Effect of flask vibration time on casting integrity, Surface Penetration and Coating Inclusion in lost foam casting of Al-Si Alloy

    SciTech Connect

    Karimian, Majid; Idris, M. H.; Ourdjini, A.; Muthu, Kali

    2011-01-17

    The paper presents the result of an experimental investigation conducted on medium aluminum silicon alloy casting- LM6, using no-vacuum assisted lost foam casting process. The study is directed for establishing the relationship between the flask vibrations times developed for molded sample on the casting integrity, surface penetration and coating inclusion defects of the casting. Four different flask vibration times namely 180, 120, 90 and 60 sec. were investigated. The casting integrity was investigated in terms of fulfilling in all portions and edges. The surface penetration was measured using optical microscope whilst image analyzer was used to quantify the percentage of coating inclusion in the casting. The results show that vibration time has significant influence on the fulfilling as well as the internal integrity of the lost foam casting. It was found that the lower vibration time produced comparatively sound casing.

  5. Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

    NASA Astrophysics Data System (ADS)

    Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin

    2013-12-01

    Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.

  6. Heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-Si alloys investigated by entrained droplet technique and DSC

    NASA Astrophysics Data System (ADS)

    Li, J. H.; Albu, M.; Ludwig, T. H.; Hofer, F.; Arnberg, L.; Schumacher, P.

    2016-03-01

    Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed. This can be attributed to the formation of phosphide compounds having a lower free energy and hence may preferentially form compared to AlP. Only a trace P addition was found to have a profound effect on the nucleation process. The nucleation kinetics is discussed on the basis of the classical nucleation theory and the free growth model, respectively. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur within the droplets, which strongly indicates that the nucleation of Si on an AlP patch or AlP particle is a limiting step for free growth. The maximum nucleation site density within one droplet is directly related to the size distribution of AlP particles or AlP patches for Si nucleation, but is independent of the cooling rates. Although the nucleation conditions were optimized in entrained droplet experiments, the observed mechanisms are also valid at moderate cooling conditions, such as in shape casting.

  7. Formation of intermetallic phases in AlSi7Fe1 alloy processed under microgravity and forced fluid flow conditions and their influence on the permeability

    NASA Astrophysics Data System (ADS)

    Steinbach, S.; Ratke, L.; Zimmermann, G.; Budenkova, O.

    2016-03-01

    Ternary Al-6.5wt.%Si-0.93wt.%Fe alloy samples were directionally solidified on-board of the International Space Station ISS in the ESA payload Materials Science Laboratory (MSL) equipped with Low Gradient Furnace (LGF) under both purely diffusive and stimulated convective conditions induced by a rotating magnetic field. Using different analysis techniques the shape and distribution of the intermetallic phase β-Al5SiFe in the dendritic microstructure was investigated, to study the influence of solidification velocity and fluid flow on the size and spatial arrangement of intermetallics. Deep etching as well as 3-dimensional computer tomography measurements characterized the size and the shape of β-Al5SiFe platelets: Diffusive growth results in a rather homogeneous distribution of intermetallic phases, whereas forced flow promotes an increase in the amount and the size of β-Al5SiFe platelets in the centre region of the samples. The β-Al5SiFe intermetallics can form not only simple platelets, but also be curved, branched, crossed, interacting with dendrites and porosity located. This leads to formation of large and complex groups of Fe-rich intermetallics, which reduce the melt flow between dendrites leading to lower permeability of the mushy zone and might significantly decrease feeding ability in castings.

  8. Analysis and optimization of process parameters in Al-SiCp laser cladding

    NASA Astrophysics Data System (ADS)

    Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín

    2016-03-01

    The laser cladding process parameters have great effect on the clad geometry and on dilution in the single and multi-pass aluminum matrix composite reinforced with SiC particles (Al/SiCp) coatings on ZE41 magnesium alloys deposited using a high-power diode laser (HPLD). The influence of the laser power (500-700 W), scan speed (3-17 mm/s) and laser beam focal position (focus, positive and negative defocus) on the shape factor, cladding-bead geometry, cladding-bead microstructure (including the presence of pores and cracks), and hardness has been evaluated. The correlation of these process parameters and their influence on the properties and ultimately, on the feasibility of the cladding process, is demonstrated. The importance of focal position is demonstrated. The different energy distribution of the laser beam cross section in focus plane or in positive and negative defocus plane affect on the cladding-bead properties.

  9. Effect of Y2O3 and TiC Reinforcement Particles on Intermetallic Formation and Hardness of Al6061 Composites via Mechanical Alloying and Sintering

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Liang; Lin, Chen-Han

    2015-08-01

    Al6061-based composites reinforced with 2 wt pctY2O3 and 2 wt pctTiC particles produced by mechanical alloying were investigated. The reinforced particles play important roles in the microstructural development and in determining the properties of the alloys. High-energy ball milling can facilitate a solid-state reaction between reinforced particles and the Al matrix, and the reaction kinetics of atomic diffusion can be accelerated enormously by subsequent sintering processing. As a result, complex intermetallic compounds and oxide particles can be formed in the alloy. In this study, the effect of reinforcement on phase formation and mechanical properties of Al6061-based composites has been examined. The results suggest that nano-Y2O3 particles can act as nucleation sites to facilitate formation of Al-Si-Y-O-based oxide particles. The addition of TiC particles can effectively refine the grain structure and encourage formation of iron-rich intermetallic compounds. Nanoindentation was used to understand the local variations in mechanical properties of the Al6061-based composites.

  10. Fluidity and microstructure formation during flow of Al-SiC particle composites

    SciTech Connect

    Yarandi, F.M.; Rohatgi, P.K.; Ray, S. . Dept. of Materials)

    1993-06-01

    This article presents the results of casting and spiral fluidity in a Al--7 wt% Si alloy reinforced with 10, 15, and 20 vol% SiC particles in permanent molds. The fluidity of the Al-SiC slurry increases linearly with temperature up to about 760 C. Above this temperature, the casting fluidity of the Al-SiC particle slurry does not change significantly with an increase in temperature. In several cases, the fluidity decreased at temperatures above 760 C. The fluidity of Al-SiC melts containing 9-[mu]m SiC particles decreased with an increase in volume percentage of SiC up to 15 vol% (the range studied), presumably due to an increase in the viscosity of the melt with increasing volume percentage of dispersoid and changes in the thermophysical properties of the composite. However, the fluidity of Al-20 vol% SiC of 14-[mu]m particle size is higher than the fluidity of Al-15 vol% SiC 9-[mu]m particles, indicating the role of particle size and surface area in decreasing fluidity. Composite slurries travel farther in a channel of larger cross sections compared to channels of smaller cross sections under similar conditions. Casting fluidity increases linearly with an increase in cross section of the channel. A model has been proposed to calculate the values of fluidity of the composite as a function of particle volume percent, superheat, flow velocity of the melt, and the cross section of the flow channel. Experimental observations have been compared with the predictions of the model, and some deviations have been attributed to settling and segregation of SiC particles observed through microstructural examination.

  11. Powder processing and properties of zircon-reinforced Al-13.5Si-2.5Mg alloy composites

    SciTech Connect

    Ejiofor, J.U.; Reddy, R.G.; Okorie, B.A.

    1997-06-01

    Zircon, ZrSiO{sub 4}, is a thermally stable mineral requiring expensive and energy-intensive process to reduce. Owing to its abundance, high hardness, excellent abrasion/wear resistance, and low coefficient of thermal expansion, a low-cost alternative use of the mineral for medium-strength tribology was investigated. The present study has developed a conventional low-cost, double-compaction powder metallurgy route in the synthesis of Al-13.5Si-2.5Mg alloy reinforced with zircon. The mechanical and physical properties were determined following the development of optimum conditions of cold pressing and reaction sintering. Reinforcing the hypereutectic Al-Si alloy with 15 vol% zircon particles (size <200 {micro}m) and cold pressing at 350 MPa to near-net shape, followed by liquid-phase reaction sintering at 615 C in vacuum for 20 min, improved the ultimate tensile strength, 0.2% yield strength, and hardness of the alloy by 4, 12.8, and 88%, respectively. At values of more than 9 vol% zircon, percent elongation and the dimensional changes of the sintered composites remained virtually unchanged. At a critical volume fraction of zircon, between 0.03 and 0.05, a sharp rise in hardness was observed. Microstructural and mechanical property analysis showed that the improvement in the mechanical properties is attributable largely to the load-bearing ability and intrinsic hardness of zircon, rather than to particulate dispersion effects. A good distribution of the dispersed zircon particulates in the matrix alloy was achieved.

  12. Compositions and morphologies of TiAlSi intermetallics in different diffusion couples

    SciTech Connect

    Gao, Tong; Liu, Guiliang; Liu, Xiangfa

    2014-09-15

    Two kinds of diffusion couples were designed to investigate the formation of ternary TiAlSi phases in Al–Si–Ti alloys. It was found that different diffusion processes result in various compositions and morphologies of TiAlSi intermetallics. The melted Al, Si and Ti atoms in the diffusion couple leads to the formation of flake-like TiAlSi phase through liquid–liquid reaction. Besides, unidirectional diffusion of Al and Si atoms into blocky TiAl{sub 3} particles or Ti powders via a liquid–solid diffusion process also results in the formation of TiAlSi, while keeping the block-like morphology. This kind of diffusion is a gradual process, driven by the concentration gradient. The reactions in the diffusion couples are helpful to understand the compositional and morphological evolutions of TiAlSi as reported in previous work. - Highlights: • Two diffusion couples were designed to investigate the formation of TiAlSi phases. • Compositions and morphologies of TiAlSi are influenced by the diffusion process. • Liquid–liquid and liquid–solid diffusions were detected. • The corresponding mechanisms were discussed.

  13. Fatigue Resistance of Liquid-assisted Self-repairing Aluminum Alloys Reinforced with Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Wright, M. Clara; Manuel, Michele; Wallace, Terryl

    2013-01-01

    A self-repairing aluminum-based composite system has been developed using a liquid-assisted healing theory in conjunction with the shape memory effect of wire reinforcements. The metal-metal composite was thermodynamically designed to have a matrix with a relatively even dispersion of a low-melting eutectic phase, allowing for repair of cracks at a predetermined temperature. Additionally, shape memory alloy (SMA) wire reinforcements were used within the composite to provide crack closure. Investigators focused the research on fatigue cracks propagating through the matrix in order to show a proof-of-concept Shape Memory Alloy Self-Healing (SMASH) technology for aeronautical applications.

  14. STRESS ANNEALING INDUCED DIFFUSE SCATTERING FROM Ni3(Al,Si) PRECIPITATES

    SciTech Connect

    Barabash, Rozaliya; Ice, Gene E; Karapetrova, Evgenia; Zschack, P.

    2012-01-01

    Diffuse scattering caused by L12 type Ni3 (Al,Si) precipitates after stress annealing of Ni-Al-Si alloys is studied. Experimental reciprocal space maps are compared to the theoretical ones. Oscillations of diffuse scattering due to Ni3 (Al,Sc) precipitates are observed. Peculiarities of diffuse scattering in asymptotic region as compared to Huang scattering region are discussed. Coupling between the stress annealing direction and the precipitate shape is demonstrated.

  15. Evaluation of CNT Dispersion Methodology Effect on Mechanical Properties of an AlSi Composite

    NASA Astrophysics Data System (ADS)

    Carvalho, O.; Buciumeanu, M.; Soares, D.; Silva, F. S.; Miranda, G.

    2015-06-01

    The aim of this paper was to evaluate the effect of different dispersion methodologies on mechanical properties of the aluminum-silicon (AlSi) composites reinforced by multi-walled carbon nanotubes (MWCNTs) coated with Ni. Different mixing procedures of MWCNTs with AlSi powder were tested, and AlSi-CNT composites were produced by hot pressing—powder metallurgy technique. The shear tests were performed to get the mechanical properties. Scanning electron microscopy with x-ray energy dispersive spectroscopy analysis and thermal analysis was used to investigate the microstructure of AlSi-CNT composites, interface reactions, and fracture morphology after shear tests. The experimental results proved that an improvement of dispersion of CNTs was achieved by using a combination of different mixing processes.

  16. The fracture of boron fibre-reinforced 6061 aluminium alloy

    NASA Technical Reports Server (NTRS)

    Wright, M. A.; Welch, D.; Jollay, J.

    1979-01-01

    The fracture of 6061 aluminium alloy reinforced with unidirectional and cross-plied 0/90 deg, 0/90/+ or - 45 deg boron fibres has been investigated. The results have been described in terms of a critical stress intensity, K(Q). Critical stress intensity factors were obtained by substituting the failure stress and the initial crack length into the appropriate expression for K(Q). Values were obtained that depended on the dimensions of the specimens. It was therefore concluded that, for the size of specimen tested, the values of K(Q) did not reflect any basic materials property.

  17. Properties and microstructures of carbon fiber reinforced magnesium alloys

    SciTech Connect

    Oettinger, O.; Gruber, M.; Grau, C.; Singer, R.F.

    1994-12-31

    Two types of carbon fibers (M40J, T300J) were incorporated into magnesium alloy matrices by a new gas pressure infiltration technique using infiltration pressures of about 10--50 MPa. Mechanical testing of the unidirectionally reinforced magnesium alloys shows excellent in-axis properties. Tensile strength of consistently more than 1000 MPa for 1.8 g/cm{sup 3} density has been obtained. However, the off-axis properties of these composites are rather poor. A promising approach to improve the fiber/matrix interface strength is by using magnesium alloys with carbide forming alloying elements such as aluminum or zirconium (AM20, AZ91, MSR-B) . The interface microstructure is observed to depend on the processing parameters, matrix content and the characteristics of the employed carbon fibers. Bending tests with varying beam length over thickness ratio are used to study the microstructure/interfacial strength relation, following an approach which is common for polymer composites. With optimized processing conditions and fiber/matrix selection interlaminar shear strength values nearly equal to polymer composites can be reached.

  18. Angle-dependent photovoltaic effect in Al-Si multilayers

    SciTech Connect

    Kyarad, A.; Lengfellner, H.

    2005-10-31

    Al-Si multilayer stacks have been prepared by an alloying process from aluminum and silicon platelets. Irradiation of a stack with infrared to visible laser radiation generates photovoltaic signals depending on the angle of incidence of the laser beam with respect to the layer planes, with zero signal and a polarity reversal for beam and layers in parallel. Results are explained in terms of photoactive layers connected in series and symmetrically aligned along the stack axis. For light beams inclined with respect to the layer planes, asymmetry is introduced by fractional shadowing of photoactive regions due to the intransparent metallic layers.

  19. Interfacial stresses in shape memory alloy-reinforced composites

    NASA Astrophysics Data System (ADS)

    Hiremath, S. R.; Prajapati, Maulik; Rakesh, S.; Roy Mahapatra, D.

    2014-03-01

    Debonding of Shape Memory Alloy (SMA) wires in SMA reinforced polymer matrix composites is a complex phenomenon compared to other fabric fiber debonding in similar matrix composites. This paper focuses on experimental study and analytical correlation of stress required for debonding of thermal SMA actuator wire reinforced composites. Fiber pull-out tests are carried out on thermal SMA actuator at parent state to understand the effect of stress induced detwinned martensites. An ASTM standard is followed as benchmark method for fiber pull-out test. Debonding stress is derived with the help of non-local shear-lag theory applied to elasto-plastic interface. Furthermore, experimental investigations are carried out to study the effect of Laser shot peening on SMA surface to improve the interfacial strength. Variation in debonding stress due to length of SMA wire reinforced in epoxy are investigated for non-peened and peened SMA wires. Experimental results of interfacial strength variation due to various L/d ratio for non-peened and peened SMA actuator wires in epoxy matrix are discussed.

  20. Strengthening Mechanisms in Nanostructured Al/SiCp Composite Manufactured by Accumulative Press Bonding

    NASA Astrophysics Data System (ADS)

    Amirkhanlou, Sajjad; Rahimian, Mehdi; Ketabchi, Mostafa; Parvin, Nader; Yaghinali, Parisa; Carreño, Fernando

    2016-07-01

    The strengthening mechanisms in nanostructured Al/SiCp composite deformed to high strain by a novel severe plastic deformation process, accumulative press bonding (APB), were investigated. The composite exhibited yield strength of 148 MPa which was 5 and 1.5 times higher than that of raw aluminum (29 MPa) and aluminum-APB (95 MPa) alloys, respectively. A remarkable increase was also observed in the ultimate tensile strength of Al/SiCp-APB composite, 222 MPa, which was 2.5 and 1.2 times greater than the obtained values for raw aluminum (88 MPa) and aluminum-APB (180 MPa) alloys, respectively. Analytical models well described the contribution of various strengthening mechanisms. The contributions of grain boundary, strain hardening, thermal mismatch, Orowan, elastic mismatch, and load-bearing strengthening mechanisms to the overall strength of the Al/SiCp microcomposite were 64.9, 49, 6.8, 2.4, 5.4, and 1.5 MPa, respectively. Whereas Orowan strengthening mechanism was considered as the most dominating strengthening mechanism in Al/SiCp nanocomposites, it was negligible for strengthening the microcomposite. Al/SiCp nanocomposite showed good agreement with quadratic summation model; however, experimental results exhibited good accordance with arithmetic and compounding summation models in the microcomposite. While average grain size of the composite reached 380 nm, it was less than 100 nm in the vicinity of SiC particles as a result of particle-stimulated nucleation mechanism.

  1. and Carbon Fiber Reinforced 2024 Aluminum Alloy Composites

    NASA Astrophysics Data System (ADS)

    Kaczmar, Jacek W.; Naplocha, Krzysztof; Morgiel, Jerzy

    2014-08-01

    The microstructure and mechanical properties of 2024 aluminum alloy composite materials strengthened with Al2O3 Saffil fibers or together with addition of carbon fibers were investigated. The fibers were stabilized in the preform with silica binder strengthened by further heat treatment. The preforms with 80-90% porosity were infiltrated by direct squeeze casting method. The microstructure of the as-cast specimens consisted mainly of α-dendrites with intermetallic compounds precipitated at their boundaries. The homogenization treatment of the composite materials substituted silica binder with a mixture of the Θ phase and silicon precipitates distributed in the remnants of SiO2 amorphous phase. Outside of this area at the binder/matrix interface, fine MgO precipitates were also present. At surface of C fibers, a small amount of fine Al3C4 carbides were formed. During pressure infiltration of preforms containing carbon fibers under oxygen carrying atmosphere, C fibers can burn releasing gasses and causing cracks initiated by thermal stress. The examination of tensile and bending strength showed that reinforcing of aluminum matrix with 10-20% fibers improved investigated properties in the entire temperature range. The largest increase in relation to unreinforced alloy was observed for composite materials examined at the temperature of 300 °C. Substituting Al2O3 Saffil fibers with carbon fibers leads to better wear resistance at dry condition with no relevant effect on strength properties.

  2. Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

  3. Thermodynamic analysis of compatibility of several reinforcement materials with beta phase NiAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with beta phase NiAl alloys within the concentration range 40 to 50 at. percent Al have been analyzed from thermodynamic considerations at 1373 and 1573 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, beryllides, and silicides. Thermodynamic data for NiAl alloys have been reviewed and activity of Ni and Al in the beta phase have been derived at 1373 and 1573 K. Criteria for chemical compatibility between the reinforcement material and the matrix have been defined and several chemically compatible reinforcement materials have been defined.

  4. Preparation and Properties of a Novel Al-Si-Ge-Zn Filler Metal for Brazing Aluminum

    NASA Astrophysics Data System (ADS)

    Niu, Zhiwei; Huang, Jihua; Yang, Hao; Chen, Shuhai; Zhao, Xingke

    2015-06-01

    The study is concerned with developing a filler metal with low melting temperature and good processability for brazing aluminum and its alloys. For this purpose, a novel Al-Si-Ge-Zn alloy was prepared according to Al-Si-Ge and Al-Si-Zn ternary phase diagrams. The melting characteristics, microstructures, wettability, and processing property of the alloy were investigated. The results showed that the melting temperature range of the novel filler metal was 505.2-545.1 °C, and the temperature interval between the solidus and the liquidus was 39.9 °C. Compared with a common Al-Si-Ge alloy, it had smaller and better dispersed β-GeSi solid solution precipitates, and the Zn-rich phases distributed on the boundary of the β-GeSi precipitates. The novel filler metal has good processability and good wettability with Al. There was one obvious transition layer with a thin α-Al solid solution between the filler metal and base metal, which is favorable to improve the strength of brazing joint.

  5. Ballistic Impact Properties of Zr-Based Amorphous Alloy Composites Reinforced with Woven Continuous Fibers

    NASA Astrophysics Data System (ADS)

    Kim, Gyeong Su; Son, Chang-Young; Lee, Sang-Bok; Lee, Sang-Kwan; Song, Young Buem; Lee, Sunghak

    2012-03-01

    This study aims at investigating ballistic impact properties of Zr-based amorphous alloy (LM1 alloy) matrix composites reinforced with woven stainless steel or glass continuous fibers. The fiber-reinforced composites with excellent fiber/matrix interfaces were fabricated without pores and misinfiltration by liquid pressing process, and contained 35 to 41 vol pct of woven continuous fibers homogeneously distributed in the amorphous matrix. The woven-STS-continuous-fiber-reinforced composite consisted of the LM1 alloy layer of 1.0 mm in thickness in the upper region and the fiber-reinforced composite layer in the lower region. The hard LM1 alloy layer absorbed the ballistic impact energy by forming many cracks, and the fiber-reinforced composite layer interrupted the crack propagation and blocked the impact and traveling of the projectile, thereby resulting in the improvement of ballistic performance by about 20 pct over the LM1 alloy. According to the ballistic impact test data of the woven-glass-continuous-fiber-reinforced composite, glass fibers were preferentially fragmented to form a number of cracks, and the amorphous matrix accelerated the fragmentation of glass fibers and the initiation of cracks. Because of the absorption process of ballistic impact energy by forming very large amounts of cracks, fragments, and debris, the glass-fiber-reinforced composite showed better ballistic performance than the LM1 alloy.

  6. Separation Mechanism of Primary Silicon from Hypereutectic Al-Si Melts Under Alternating Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Xue, Haiyang; Lv, Guoqiang; Ma, Wenhui; Chen, Daotong; Yu, Jie

    2015-07-01

    Solar grade silicon (SOG-Si) and hypereutectic Al-Si alloys with low silicon (silicon composition below 25 pct) can be successfully obtained by separation of hypereutectic Al-Si alloy with high silicon (silicon composition above 30 pct) under an alternating electromagnetic field after post-processing. To explore the separation mechanism in detail, experiments were conducted in this study using a high-frequency induction furnace with different pulling conditions of the crucible which is loaded with Al-45 wt pct Si melt. Results demonstrate that the separation of hypereutectic Al-Si alloy is feasible through either a pull-up or drop-down process. The height of each separation interface between the compact and sparse parts of the primary silicon decrease as the pull-up distance rose. When the pulling rate is very low, resultant morphologies of compact primary silicon are rounded and polygonal, allowing for more effective separation of the primary silicon. A novel physical model is presented here based on the experimental results and simulation. The model can be used to effectively describe the separation mechanism of primary silicon from hypereutectic Al-Si melts under alternating electromagnetic fields.

  7. Control of silicon solidification and the impurities from an Al-Si melt

    NASA Astrophysics Data System (ADS)

    Wang, Panpan; Lu, Huimin; Lai, Yuanshi

    2014-03-01

    The investigation on purification of metallurgical grade silicon by solidification of hypereutectic Al-Si melt under the temperature gradient as an intensified separation way was carried out. Based on the available thermodynamic parameters and experimental data, the thermodynamic behavior and chemical composition of metallic impurities was studied in the solidification process. The principle for the silicon growth in the Al-Si melts was investigated. The results indicated that the refined silicon grains were successfully enriched at the top of the Al-Si alloy. Then the top part refined silicon was collected by aqua regia leaching. Electrorefining of the bottom part (Al-22%Si) was investigated effectively in view of recovering pure Si and Al. Additionally, according to previous investigation, the optimized technical process for SOG-Si production was proposed.

  8. Anomalous phonon properties in the silicide superconductors CaAlSi and SrAlSi

    NASA Astrophysics Data System (ADS)

    Kuroiwa, S.; Hasegawa, T.; Kondo, T.; Ogita, N.; Udagawa, M.; Akimitsu, J.

    2008-11-01

    Lattice-dynamical properties of CaAlSi and SrAlSi with a similar layer structure to MgB2 have been first investigated by both Raman-scattering and ab initio calculations. All Raman-active phonons with E' symmetry have been clearly observed for both compounds. Their line shapes are asymmetric but their linewidths are ˜10cm-1 , which is very narrower than that of MgB2 . In addition to the Raman-active modes, several extra peaks have been observed below 160cm-1 . These low-energy extra modes can be assigned to the out-of-plane vibrations of Al perpendicular to Al-Si basal plane. Since these peak intensities are strongly affected by the incident energy (resonance Raman process), the electronic state is important for them. Moreover, in both crystals of CaAlSi and SrAlSi, we point out the energy difference for the different propagation directions along the c axis and the c plane, in spite of the very close wave vector to the Brillouin-zone center. This energy difference cannot be explained by a usual Raman-scattering scenario at this stage.

  9. Physical and Mechanical Properties of Composites and Light Alloys Reinforced with Detonation Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Sakovich, G. V.; Vorozhtsov, S. A.; Vorozhtsov, A. B.; Potekaev, A. I.; Kulkov, S. N.

    2016-07-01

    The influence of introduction of particles of detonation-synthesized nanodiamonds into composites and aluminum-base light alloys on their physical and mechanical properties is analyzed. The data on microstructure and physical and mechanical properties of composites and cast aluminum alloys reinforced with diamond nanoparticles are presented. The introduction of nanoparticles is shown to result in a significant improvement of the material properties.

  10. Load carrying capacity of RCC beams by replacing steel reinforcement bars with shape memory alloy bars

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2016-04-01

    In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

  11. Low-Cost Process for Silicon Purification with Bubble Adsorption in Al-Si Melt

    NASA Astrophysics Data System (ADS)

    Yu, Wenzhou; Ma, Wenhui; Lv, Guoqiang; Ren, Yongsheng; Dai, Yongnian; Morita, Kazuki

    2014-08-01

    The primary silicon and Al-Si alloy have been separated in hypereutectic Al-Si melt by the electromagnetic stirring and directional solidification processes. During the electromagnetic separation process, the behavior of a hydrogen bubble in Al-Si melt has been discussed. Furthermore, the bubble adsorption effect for the Si purification has been revealed. The results show that the bubble cavity formed in the lower part of the sample by pulling it up. The scanning electron microscope along with energy dispersive spectrometer (SEM-EDS) analysis indicated that a lot of impurities were adsorbed onto the surface of the bubble cavity that may be beneficial for the Si purification. By decreasing the pulling-up rates, the size of the bubble cavity in Al-Si alloy increased, which results in the decreasing of the impurity contents in primary silicon. In this work, the impurity content in primary silicon is 10.8 ppmw, which is obviously improved compared with the 777.57 ppmw in metallurgical silicon. It is a low-cost technology that will be a potential route for the Si purification.

  12. Improvement in performance of reinforced concrete structures using shape memory alloys

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2015-04-01

    Shape memory alloys (SMA) are a unique class of materials which have ability to undergo large deformation and also regain its undeformed shape by removal of stress or by heating. This unique property could be effectively utilized to enhance the safety of a structure. This paper presents the pushover analysis performance of a Reinforced Concrete moment resistance frame with the traditional steel reinforcement replaced partially with Nickel-Titanium (Nitinol) SMA. The results are compared with the RC structure reinforced with conventional steel. Partial replacement of traditional steel reinforcement by SMA shows better performance.

  13. Preparation and Characterization of Binder Less Mg/Mg Alloy Infiltrated SiCp Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Muthu Kumar, S.; Dhindaw, B. K.

    2007-10-01

    SiCp-reinforced commercial pure magnesium and AZ91 alloy MMCs’ were prepared through infiltration route without the use of any special atmospheres. The preform was prepared using a mixture of reinforcement particles and the matrix metal particles. The composites were prepared with various volume percentage of the reinforcement and their properties with the variation of SiCp were analyzed. The interfacial properties of the composites were analyzed using microstructure, microhardness, and wear studies. Calculation of thermal conditions during infiltration was done to study the effect of adding matrix metal particles on the infiltration behavior and its effect on the uniformity distribution of the reinforcements.

  14. Nano-hardness and microstructure of selective laser melted AlSi10Mg scan tracks

    NASA Astrophysics Data System (ADS)

    Aboulkhair, Nesma T.; Maskery, Ian; Tuck, Chris; Ashcroft, Ian; Everitt, Nicola

    2015-07-01

    Selective laser melting (SLM) of aluminium alloys faces more challenges than other ongoing alloys such as stainless steels and titanium alloys because of the material's properties. It is important to study single scan tracks if high density large parts are to be made since they are the primary building blocks. In this study, the geometrical features of AlSi10Mg tracks indicated keyhole mode melting domination. Chemical composition mapping and nanoindentation showed enhanced nano-hardness in SLM material over conventional material with no spatial variation. This is due to a homogeneous elemental distribution and fine microstructure developed by fast solidification.

  15. Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

    2016-01-01

    The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

  16. Investigation on corrosion and wear behaviors of nanoparticles reinforced Ni-based composite alloying layer

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Tao, Jie; Jiang, Shuyun; Xu, Zhong

    2008-04-01

    In order to investigate the role of amorphous SiO 2 particles in corrosion and wear resistance of Ni-based metal matrix composite alloying layer, the amorphous nano-SiO 2 particles reinforced Ni-based composite alloying layer has been prepared by double glow plasma alloying on AISI 316L stainless steel surface, where Ni/amorphous nano-SiO 2 was firstly predeposited by brush plating. The composition and microstructure of the nano-SiO 2 particles reinforced Ni-based composite alloying layer were analyzed by using SEM, TEM and XRD. The results indicated that the composite alloying layer consisted of γ-phase and amorphous nano-SiO 2 particles, and under alloying temperature (1000 °C) condition, the nano-SiO 2 particles were uniformly distributed in the alloying layer and still kept the amorphous structure. The corrosion resistance of composite alloying layer was investigated by an electrochemical method in 3.5%NaCl solution. Compared with single alloying layer, the amorphous nano-SiO 2 particles slightly decreased the corrosion resistance of the Ni-Cr-Mo-Cu alloying layer. X-ray photoelectron spectroscopy (XPS) revealed that the passive films formed on the composite alloying consisted of Cr 2O 3, MoO 3, SiO 2 and metallic Ni and Mo. The dry wear test results showed that the composite alloying layer had excellent friction-reduced property, and the wear weight loss of composite alloying layer was less than 60% of that of Ni-Cr-Mo-Cu alloying layer.

  17. Dispersoid reinforced alloy powder and method of making

    SciTech Connect

    Anderson, Iver E.; Terpstra, Robert L.

    2012-06-12

    A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

  18. Dispersoid reinforced alloy powder and method of making

    SciTech Connect

    Anderson, Iver E.; Terpstra, Robert L.

    2010-04-20

    A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

  19. Microstructural Development in Al-Si Powder During Rapid Solidification

    SciTech Connect

    Amber Lynn Genau

    2004-12-19

    Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

  20. Dispersoid reinforced alloy powder and method of making

    SciTech Connect

    Anderson, Iver E; Rieken, Joel

    2013-12-10

    A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with an introduced reactive species than does the alloying element and wherein one or more atomizing parameters is/are modified to controllably reduce the amount of the reactive species, such as oxygen, introduced into the atomized particles so as to reduce anneal times and improve reaction (conversion) to the desired strengthening dispersoids in the matrix. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies are made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

  1. Effect of nano-hydroxyapatite reinforcement in mechanically alloyed NiTi composites for biomedical implant.

    PubMed

    Akmal, Muhammad; Raza, Ahmad; Khan, Muhammad Mudasser; Khan, M Imran; Hussain, Muhammad Asif

    2016-11-01

    Equi-atomic NiTi alloy composites reinforced with 0, 2, 4 and 6vol.% nano-hydroxyapatite (HA) were successfully synthesized using pressureless sintering. Pure Ni and Ti elements were ball milled for 10h in order to produce a mechanically alloyed equi-atomic NiTi alloy (MA-NiTi). Mechanically alloyed NiTi and HA powders were blended, compacted and then sintered for 3h at 1325K. The sintered density varied inversely with volume percent of HA reinforcement. The X-Ray diffraction spectra and SEM images showed the formation of multiple phases like NiTi, NiTi2, Ni3Ti, and Ni4Ti3. The back scattered-SEM image analysis confirmed the presence of Ni-rich and Ti-rich phases with increasing HA content. The 6vol.% HA reinforced composite showed Ni3Ti as the major phase having the highest hardness value which can be attributed to the presence of relatively harder phases along with higher HA content as a reinforcement. The composite of MA-NiTi with 2vol.% HA manifested the most desirable results in the form of better sintering density mainly due to the minute decomposition of NiTi into other phases. Therefore, the 2vol.% reinforced MA-NiTi composite can be exploited as a novel material for manufacturing biomedical implants. PMID:27523992

  2. Nanostructured Nb reinforced NiTi shape memory alloy composite with high strength and narrow hysteresis

    NASA Astrophysics Data System (ADS)

    Hao, Shijie; Cui, Lishan; Jiang, Daqiang; Yu, Cun; Jiang, Jiang; Shi, Xiaobin; Liu, Zhenyang; Wang, Shan; Wang, Yandong; Brown, Dennis E.; Ren, Yang

    2013-06-01

    An in-situ nanostructured Nb reinforced NiTi shape-memory alloy composite was fabricated by mechanical reduction of an as-cast Nb-NiTi eutectic alloy. The composite exhibits large elastic strain, high strength, narrow hysteresis, and high mechanical energy storage density and efficiency during tensile cycling. In situ synchrotron high-energy X-ray diffraction revealed that these superior properties were attributed to the strong coupling between nanostructured Nb and NiTi matrix during deformation. Furthermore, this study offers a good understanding of the deformation behavior of the nanoscale reinforcement embedded in the metal matrix deformed by stress-induced phase transformation.

  3. A Fatigue Model for Discontinuous Particulate-Reinforced Aluminum Alloy Composite: Influence of Microstructure

    NASA Astrophysics Data System (ADS)

    McCullough, R. R.; Jordon, J. B.; Brammer, A. T.; Manigandan, K.; Srivatsan, T. S.; Allison, P. G.; Rushing, T. W.

    2014-01-01

    In this paper, the use of a microstructure-sensitive fatigue model is put forth for the analysis of discontinuously reinforced aluminum alloy metal matrix composite. The fatigue model was used for a ceramic particle-reinforced aluminum alloy deformed under conditions of fully reversed strain control. Experimental results revealed the aluminum alloy to be strongly influenced by volume fraction of the particulate reinforcement phase under conditions of strain-controlled fatigue. The model safely characterizes the evolution of fatigue damage in this aluminum alloy composite into the distinct stages of crack initiation and crack growth culminating in failure. The model is able to capture the specific influence of particle volume fraction, particle size, and nearest neighbor distance in quantifying fatigue life. The model yields good results for correlation of the predicted results with the experimental test results on the fatigue behavior of the chosen aluminum alloy for two different percentages of the ceramic particle reinforcement. Further, the model illustrates that both particle size and volume fraction are key factors that govern fatigue lifetime. This conclusion is well supported by fractographic observations of the cyclically deformed and failed specimens.

  4. Al-Si-Cu/TiN multilayer interconnection and Al-Ge reflow sputtering technologies for quarter-micron devices

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takamaro; Kikuta, Kuniko

    1993-05-01

    Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.

  5. Dispersoid reinforced alloy powder and method of making

    SciTech Connect

    Anderson, Iver E; Terpstra, Robert L

    2014-10-21

    A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. Bodies made from the dispersion strengthened solidified particles exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures.

  6. Wear resistance of TiAlSiN thin coatings.

    PubMed

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions. PMID:23447962

  7. Multi-Objective Optimization in Hot Machining of Al/SiCp Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Jadhav, M. R.; Dabade, U. A.

    2016-02-01

    Metal Matrix Composites (MMCs) have been found to be useful in a number of engineering applications and particle reinforced MMCs have received considerable attention due to their excellent engineering properties. These materials are generally regarded as extremely difficult to machine, because of the abrasive characteristics of the reinforced particulates. These characteristics of MMCs affect the machined surface quality and integrity. This paper presents use of Taguchi Grey Relational Analyses (GRA) for optimization of Al/SiCp/10p (220 and 600 mesh) MMCs produced by stir casting. Experiments are performed using L16 orthogonal array by using hot machining technique. The objective of this study is to identify the optimum process parameters to improve the surface integrity on Al/SiCp MMCs. The machined surface integrity has been analyzed by process parameters such as speed, feed, depth of cut and preheating temperature. The significance of the process parameters on surface integrity has been evaluated quantitatively by the analysis of variance (ANOVA) method and AOM plots. The grey relational analysis shows optimum machining conditions as 0.05 mm/rev feed, 0.4 mm depth of cut and 60 °C preheating temperature to enhance surface integrity for both Al/SiCp/10p (220 and 600 mesh) MMCs except for cutting speed 50 and 25 m/min respectively.

  8. Interfacial valence electron localization and the corrosion resistance of Al-SiC nanocomposite

    NASA Astrophysics Data System (ADS)

    Mosleh-Shirazi, Sareh; Hua, Guomin; Akhlaghi, Farshad; Yan, Xianguo; Li, Dongyang

    2015-12-01

    Microstructural inhomogeneity generally deteriorates the corrosion resistance of materials due to the galvanic effect and interfacial issues. However, the situation may change for nanostructured materials. This article reports our studies on the corrosion behavior of SiC nanoparticle-reinforced Al6061 matrix composite. It was observed that the corrosion resistance of Al6061 increased when SiC nanoparticles were added. Overall electron work function (EWF) of the Al-SiC nanocomposite increased, along with an increase in the corrosion potential. The electron localization function of the Al-SiC nanocomposite was calculated and the results revealed that valence electrons were localized in the region of SiC-Al interface, resulting in an increase in the overall work function and thus building a higher barrier to hinder electrons in the nano-composite to participate in corrosion reactions.

  9. Interfacial valence electron localization and the corrosion resistance of Al-SiC nanocomposite

    PubMed Central

    Mosleh-Shirazi, Sareh; Hua, Guomin; Akhlaghi, Farshad; Yan, Xianguo; Li, Dongyang

    2015-01-01

    Microstructural inhomogeneity generally deteriorates the corrosion resistance of materials due to the galvanic effect and interfacial issues. However, the situation may change for nanostructured materials. This article reports our studies on the corrosion behavior of SiC nanoparticle-reinforced Al6061 matrix composite. It was observed that the corrosion resistance of Al6061 increased when SiC nanoparticles were added. Overall electron work function (EWF) of the Al-SiC nanocomposite increased, along with an increase in the corrosion potential. The electron localization function of the Al-SiC nanocomposite was calculated and the results revealed that valence electrons were localized in the region of SiC-Al interface, resulting in an increase in the overall work function and thus building a higher barrier to hinder electrons in the nano-composite to participate in corrosion reactions. PMID:26667968

  10. Microstructural development of rapid solidification in Al-Si powder

    SciTech Connect

    Jin, F.

    1995-11-01

    The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 {mu}m to 150 {mu}m diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

  11. Functionally Graded Al Alloy Matrix In-Situ Composites

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.

    2010-01-01

    In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.

  12. Application of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Yano, Hayato; Koetaka, Yuji; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2012-04-01

    Experimental works are done to assess the seismic behavior of concrete beams reinforced with superelastic alloy (SEA) bars. Applicability of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, have been proposed as partial replacements for conventional steel bars in order to reduce residual deformations in structures during and after intense earthquakes. Four-point reverse-cyclic bending tests were done on 1/3 scale concrete beams comprising three different types of specimens - conventional steel reinforced concrete (ST-RC), SEA reinforced concrete (SEA-RC), and SEA reinforced concrete with pre-tensioning (SEA-PC). The results showed that SEA reinforced concrete beams demonstrated significant enhancement in crack recovery capacity in comparison to steel reinforced beam. Average recovery of cracks for each of the specimens was 21% for ST-RC, 84% for SEA-RC, and 86% for SEA-PC. In addition, SEA-RC and SEA-PC beams demonstrated strong capability of recentering with comparable normalized strength and ductility relative to conventional ST-RC beam specimen. ST-RC beam, on the other hand, showed large residual cracks due to progressive reduction in its re-centering capability with each cycle. Both the SEA-RC and SEA-PC specimens demonstrated superiority of Cu-Al-Mn SEA bars to conventional steel reinforcing bars as reinforcement elements.

  13. About molybdenum behaviour during U(Mo)/Al(Si) interaction processes

    NASA Astrophysics Data System (ADS)

    Iltis, X.; Allenou, J.; Verhaeghe, B.; Palancher, H.; Tougait, O.; Bonnin, A.; Tucoulou, R.

    2013-02-01

    U(Mo)/Al(Si) diffusion couples are studied to provide a better understanding of the interaction processes between the U(Mo) fuel and the Al(Si) matrix and, more specifically, to determine the molybdenum behaviour in the interaction product, close to the U(Mo) alloy. Micro-computed tomography and micro-X-ray diffraction measurements in transmission mode, coupled with scanning transmission electron microscopy and energy dispersive X-ray spectroscopy analysis show that molybdenum is present in the interaction layer, close to the U(Mo) interface, in an U4Mo(MoxSi1-x)Si2 ternary intermediate phase, mixed with the U3Si5 phase. The formation of this Mo-containing phase is accompanied by a Mo depletion process, in the underlying U(Mo) alloy, this depletion leading to a γ-U(Mo) phase local destabilisation. A strong correlation between the Si and the Mo behaviours, in the U(Mo)/Al(Si) system, is thus evidenced.

  14. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  15. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  16. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  17. Processing and response of aluminum-lithium alloy composites reinforced with copper-coated silicon carbide particulates

    SciTech Connect

    Khor, K.A.; Cao, Y.; Boey, F.Y.C.; Hanada, K.; Murakoshi, Y.; Sudarshan, T.S.; Srivatsan, T.S.

    1998-02-01

    Lithium-containing aluminum alloys have shown promise for demanding aerospace applications because of their light weight, high strength, and good damage tolerance characteristics. Additions of ceramic reinforcements to an aluminum-lithium alloy can significantly enhance specific strength, and specific modulus while concurrently offering acceptable performance at elevated temperatures. The processing and fabrication of aluminum-lithium alloy-based composites are hampered by particulate agglomeration or clustering and the existence of poor interfacial relationships between the reinforcing phase and the matrix. The problem of distribution of the reinforcing phase in the metal matrix can be alleviated by mechanical alloying. This article presents the results of a study aimed at addressing and improving the interfacial relationship between the host matrix and the reinforcing phase. Copper-coated silicon carbide particulates are introduced as the particulate reinforcing phase, and the resultant composite mixture is processed by conventional milling followed by hot pressing and hot extrusion. The influence of extrusion ration and extrusion temperature on microstructure and mechanical properties was established. Post extrusion processing by hot isostatic pressing was also examined. Results reveal the increase in elastic modulus of the aluminum-lithium alloy matrix reinforced with copper-coated SiC to be significantly more than the mechanically alloyed Al-Li/SiC counterpart. This suggests the possible contributions of interfacial strengthening on mechanical response in direct comparison with a uniform distribution of the reinforcing ceramic particulates.

  18. Microstructure and mechanical properties of titanium alloys reinforced with titanium boride

    NASA Astrophysics Data System (ADS)

    Hill, Davion M.

    Microstructure features in TiB-reinforced titanium alloys are correlated with mechanical properties. Both laser deposition and arc melting are used to fabricate test alloys where microstructure evolution with heat treatment is examined. SEM and TEM investigations of microstructure are coupled with 3D reconstruction to provide an adequate picture of phases in these alloys. Mechanical properties are then studied. Wear testing of several test alloys is presented, followed by hardness and modulus measurements of individual phases via micro- and nano-indentation as well as a novel micro-compression technique. Bulk mechanical properties are then tested in Ti-6Al-4V and Ti-555 (Ti-5Al-5V-5Mo-3Cr-1Fe) with varying amounts of boron. Image processing methods are then applied to high resolution back-scattered scanning electron microscope images to quantify microstructure features in the tensile test specimens, and these values are then correlated with mechanical properties.

  19. Interfaces and failure mechanisms in Al-SiC composites

    NASA Technical Reports Server (NTRS)

    Nutt, S. R.

    1986-01-01

    Aluminum alloys reinforced with silicon carbide whiskers exhibit significantly higher strength and modulus than the unreinforced alloys. However, the composites also exhibit low ductility and poor fracture toughness for reasons which are not well-understood. In this study, high resolution and conventional TEM techniques are used to analyze interface microstructure and failure mechanisms in P/M 2124 and 6061 aluminum alloys reinforced with silicon carbide whiskers. Interfacial oxides are typical of both composite materials, often distributed in clusters or in a discrete layer 2-5 nm thick along the whisker-matrix interface. Highly deformed regions beneath bulk tensile fracture surfaces reveal possible fracture nucleation centers as well as sites of stress concentration where intense plastic strain has occurred. Observations of such highly deformed regions include (1) void initiation at whisker ends, (2) interface decohesion involving the thin oxide layer, (3) transverse cracks in whiskers, and (4) cracks in large constituent particles. TEM results are presented and discussed in relation to mechanisms of composite failure.

  20. Fabrication of a nanocomposite from in situ iron nanoparticle reinforced copper alloy.

    PubMed

    Wang, Zidong; Wang, Xuewen; Wang, Qiangsong; Shih, I; Xu, J J

    2009-02-18

    In situ iron nanoparticle reinforced Cu-3Sn-8Zn-6Pb alloy has been fabricated by centrifugal casting in a vacuum chamber with a medium frequency electrical furnace. The microstructure of this alloy was analyzed with a scanning electron microscope (SEM) and a high-resolution transmission electron microscope (HRTEM), and the results show that the grains of Cu-3Sn-8Zn-6Pb alloy without iron have a typical dendrite structure with dimensions from 500 to 1500 microm, and the grains of the alloy with the addition of 1% iron are small and equiaxed, with dimensions from 20 to 60 microm. Then, the relatively uniform dispersed particles in the copper matrix were identified with the HRTEM to be pure iron with dimensions in the order of 2-20 nm. The mechanical properties of the alloys were measured and the results show a significant increase in the tensile strength of the alloy with iron nanoparticles and a slight increase of the elongation compared to that without iron. The mechanism of formation of the iron nanoparticles was analyzed by thermodynamic and dynamic theories, and the results indicate that the in situ iron nanoparticles of Cu-3Sn-8Zn-6Pb alloy can reasonably form during solidification in the centrifugal casting technique. PMID:19417426

  1. Fabrication of a nanocomposite from in situ iron nanoparticle reinforced copper alloy

    NASA Astrophysics Data System (ADS)

    Wang, Zidong; Wang, Xuewen; Wang, Qiangsong; Shih, I.; Xu, J. J.

    2009-02-01

    In situ iron nanoparticle reinforced Cu-3Sn-8Zn-6Pb alloy has been fabricated by centrifugal casting in a vacuum chamber with a medium frequency electrical furnace. The microstructure of this alloy was analyzed with a scanning electron microscope (SEM) and a high-resolution transmission electron microscope (HRTEM), and the results show that the grains of Cu-3Sn-8Zn-6Pb alloy without iron have a typical dendrite structure with dimensions from 500 to 1500 µm, and the grains of the alloy with the addition of 1% iron are small and equiaxed, with dimensions from 20 to 60 µm. Then, the relatively uniform dispersed particles in the copper matrix were identified with the HRTEM to be pure iron with dimensions in the order of 2-20 nm. The mechanical properties of the alloys were measured and the results show a significant increase in the tensile strength of the alloy with iron nanoparticles and a slight increase of the elongation compared to that without iron. The mechanism of formation of the iron nanoparticles was analyzed by thermodynamic and dynamic theories, and the results indicate that the in situ iron nanoparticles of Cu-3Sn-8Zn-6Pb alloy can reasonably form during solidification in the centrifugal casting technique.

  2. Feasibility of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Koetaka, Yuji; Suzuki, Yusuke; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2013-02-01

    Experimental and numerical works are reported to assess the cyclic response of concrete beams reinforced with superelastic alloy (SEA) bars. The feasibility of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost and high machinability, is examined as partial replacements for conventional steel bars, in order to reduce residual cracks in structures during and after intense earthquakes. Four-point reverse cyclic bending tests were done on one-third scale concrete beams comprising three different types of specimens—conventional steel reinforced concrete, SEA reinforced concrete and SEA reinforced concrete (RC) with pre-tensioning. The results showed that SEA reinforced concrete beams demonstrated strong recentering capability and significant enhancement in crack recovery capacity, in comparison to steel reinforced beams. Furthermore, corresponding finite element models were generated to simulate the experimental observations. Both the experimental observations and finite element computations illustrated the superiority of SEA bars to conventional steel bars in providing RC beam specimens with recentering and crack recovery capabilities.

  3. Experimental investigation of bond in concrete members reinforced with shape memory alloy bars

    NASA Astrophysics Data System (ADS)

    Daghash, S. M.; Sherif, M. M.; Ozbulut, O. E.

    2015-04-01

    Conventional seismic design of reinforced concrete structures relies on yielding of steel reinforcement to dissipate energy while undergoing residual deformations. Therefore, reinforced concrete structures subjected to strong earthquakes experience large permanent displacements and are prone to severe damage or collapse. Shape memory alloys (SMAs) have gained increasing acceptance in recent years for use in structural engineering due to its attractive properties such as high corrosion resistance, excellent re-centering ability, good energy dissipation capacity, and durability. SMAs can undergo large deformations in the range of 6-8% strain and return their original undeformed position upon unloading. Due to their appealing characteristics, SMAs have been considered as an alternative to traditional steel reinforcement in concrete structures to control permanent deformations. However, the behavior of SMAs in combination with concrete has yet to be explored. In particular, the bond strength is important to ensure the composite action between concrete and SMA reinforcements. This study investigates the bond behavior between SMA bars and concrete through pull-out tests. To explore the size effect on bond strength, the tests are performed using various diameters of SMA bars. For the same diameter, the tests are also conducted with different embedment length to assess the effect of embedment length on bond properties of SMA bars. To monitor the slippage of the SMA reinforcement, an optical Digital Image Correlation method is used and the bond-slip curves are obtained.

  4. Microstructural Observations in a Cast Al-Si-Cu/TiC Composite

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Georgatis, E.; Poulas, V.; Mavros, H.

    2010-06-01

    A 3-5 vol.% TiC particulate Al-Si-Cu composite was prepared by diluting Al/20 vol.% TiC composite in an Al-7Si-4Cu alloy matrix. TiC particle distribution consists of isolated and clustered particles which are both located at the primary-α grain boundaries and at the areas of the last solidified liquid. Particle pushing by the solidification front is responsible for the final particle location. The solidified microstructure consists of primary and intermetallic phases formed by a sequence of possible eutectic reactions. No evidence of TiC particle degradation was observed.

  5. Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Girish, B. M.; Satish, B. M.; Kamath, R.

    1998-12-01

    Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials have been evaluated in the present study. The liquid metallurgy technique was used to fabricate the composites, in which preheated short glass fibers were introduced into the ZA-27 alloy melt above its liquidus temperature. The aging temperature employed was 125 °C for 6, 12,18, and 24 h. The aged alloy (no fibers) reached the peak hardness after 18 h, while the composites (regardless of filler content) reached the same hardness in 12 h. It is hypothesized that the aging treatment of a composite improves the strength of the interface between the short fibers and the matrix. This is confirmed by the tensile fractograph analysis, which indicates that at a given aging temperature, the composites aged for 18 h exhibit short fibers that remain attached to the metal matrix, while those aged for 6 h undergo debonding.

  6. Physical and mechanical properties of LoVAR: a new lightweight particle-reinforced Fe-36Ni alloy

    NASA Astrophysics Data System (ADS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-09-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  7. Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

    NASA Technical Reports Server (NTRS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-01-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  8. Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.

    PubMed

    Laha, T; Liu, Y; Agarwal, A

    2007-02-01

    Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites. PMID:17450788

  9. Microstructure and mechanical properties of Ni sub 3 Al-based alloys reinforced with particulates

    SciTech Connect

    McKamey, C.G.; Carmichael, C.A.

    1990-01-01

    Hot-extrusion was used to produce Ni{sub 3}Al-based alloys to which 10 vol % TiN, NbC, HfO{sub 2}, or HfN was added for reinforcement. The TiN, NbC, and HfO{sub 2} particulates produced Ni{sub 3}Al-matrix composites in which no reaction was noted at the particle-matrix interface. However, the addition of HfN resulted in extensive reaction in which the hafnium appeared to diffuse into the matrix. Microstructures of this alloy showed a complex array of phases and voids where the HfN particles are presumed to have been originally. Hot hardness, compression, and compression creep tests were preformed on specimens cut from the extruded bar of each alloy. No significant strengthening was observed for the alloys containing TiN, NbC, or HfO{sub 2}. However the HfN-containing alloy did show significant strengthening in simple compression and compression creep. This presentation will include microstructures and the results of the mechanical properties tests. 26 refs., 5 figs.

  10. Development of Carbon Fiber Reinforced Stellite Alloy Based Composites for Tribocorrosion Applications

    NASA Astrophysics Data System (ADS)

    Khoddamzadeh, Alireza

    This thesis reports the design and development of two classes of new composite materials, which are low-carbon Stellite alloy matrices, reinforced with either chopped plain carbon fiber or chopped nickel-coated carbon fiber. The focus of this research is on obviating the problems related to the presence of carbides in Stellite alloys by substituting carbides as the main strengthening agent in Stellite alloys with the aforementioned carbon fibers. Stellite 25 was selected as the matrix because of its very low carbon content (0.1 wt%) and thereby relatively carbide free microstructure. The nickel coating was intended to eliminate any chance of carbide formation due to the possible reaction between carbon fibers and the matrix alloying additions. The composite specimens were fabricated using the designed hot isostatic pressing and sintering cycles. The fabricated specimens were microstructurally analyzed in order to identify the main phases present in the specimens and also to determine the possible carbide formation from the carbon fibers. The material characterization of the specimens was achieved through density, hardness, microhardness, corrosion, wear, friction, and thermal conductivity tests. These novel materials exhibit superior properties compared to existing Stellite alloys and are expected to spawn a new generation of materials used for high temperature, severe corrosion, and wear resistant applications in various industries.

  11. Compressive behavior of titanium alloy skin-stiffener specimens selectively reinforced with boron-aluminum composite

    NASA Technical Reports Server (NTRS)

    Herring, H. W.; Carri, R. L.; Webster, R. C.

    1971-01-01

    A method of selectively reinforcing a conventional titanium airframe structure with unidirectional boron-aluminum composite attached by brazing was successfully demonstrated in compression tests of short skin-stiffener specimens. In a comparison with all-titanium specimens, improvements in structural performance recorded for the composite-reinforced specimens exceeded 25 percent on an equivalent-weight basis over the range from room temperature to 700 K (800 F) in terms of both initial buckling and maximum strengths. Performance at room temperature was not affected by prior exposure at 588 K (600 F) for 1000 hours in air or by 400 thermal cycles between 219 K and 588 K (-65 F and 600 F). The experimental results were generally predictable from existing analytical procedures. No evidence of failure was observed in the braze between the boron-aluminum composite and the titanium alloy.

  12. Reactive spark plasma sintering (SPS) of nitride reinforced titanium alloy composites

    SciTech Connect

    Borkar, Tushar; Nag, Soumya; Ren, Yang; Tiley, Jaimie; Banerjee, Rajarshi

    2014-12-25

    Coupled in situ alloying and nitridation of titanium–vanadium alloys, has been achieved by introducing reactive nitrogen gas during the spark plasma sintering (SPS) of blended titanium and vanadium elemental powders, leading to a new class of nitride reinforced titanium alloy composites. The resulting microstructure includes precipitates of the d-TiN phase with the NaCl structure, equiaxed (or globular) precipitates of a nitrogen enriched hcp a(Ti,N) phase with a c/a ratio more than what is expected for pure hcp Ti, and fine scale plate-shaped precipitates of hcp a-Ti, distributed within a bcc b matrix. During SPS processing, the d-TiN phase appears to form at a temperature of 1400 C, while only hcp a(Ti,N) and a-Ti phases form at lower processing temperatures. Consequently, the highest microhardness is exhibited by the composite processed at 1400 C while those processed at 1300 C or below exhibit lower values. Processing at temperatures below 1300 C, resulted in an incomplete alloying of the blend of titanium and vanadium powders. These d-TiN precipitates act as heterogeneous nucleation sites for the a(Ti,N) precipitates that appear to engulf and exhibit an orientation relationship with the nitride phase at the center. Furthermore, fine scale a-Ti plates are precipitated within the nitride precipitates, presumably resulting from the retrograde solubility of nitrogen in titanium.

  13. Hard particle reinforced aluminum-alloys for aircraft applications EWISCO 1993--1994

    SciTech Connect

    Lugscheider, E.; Jokiel, P.; Remer, P.; Yushchenko, K.; Borisov, Y.; Vitiaz, P.; Steinhaeuser, S.

    1994-12-31

    Light metals such as aluminum, titanium, magnesium are widely used as structural materials in industrial parts. Their low density combined with reasonable physical properties are the main advantages of these materials that have led to a wide range of applications in transportation, particularly in the fabrication of aircrafts. Some of the disadvantages of these light metals and alloys are low wear resistance, high reactivity and low thermal tolerance. Thermal sprayed coatings are required to protect these structures and to broaden the use of these materials. The goal of this collaborative research work was to improve wear and corrosion properties of common Al-alloys. Five hard particle reinforced aluminum based powders were sprayed with different thermal spray processes. In order to optimize the wear and corrosion resistance of the coatings different spray processes and spray parameters were investigated. The coatings were produced mainly using atmospherical plasma spraying and CDS (continuous detonation spraying). Further tests with two ukrainian types of flame spraying were carried out. The aluminum alloy 7075 [AlZnMgCu1,5] was used as substrate material. Powder and coating morphology, porosity and homogeneity were investigated. Several tests for wear, corrosion behavior, bond strength and hardness were also carried out. The results of this investigation illustrate the excellent properties of thermal sprayed surface coatings in the field of wear and corrosion protection which expands the future applications of these aluminum alloys. This paper presents the results obtained at the Materials Science Institute, Aachen.

  14. Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8 mm, P < 10−4, and 19.3% to 77.7% at 0.1 mm, P < 10−8. Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential. PMID:25553057

  15. A Modified Constitutive Equation for Aluminum Alloy Reinforced by Silicon Carbide Particles at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Yang, Yajing; Li, Fuguo; Yuan, Zhanwei; Qiao, Huijuan

    2013-09-01

    In this paper, the constitutive relationship of an aluminum alloy reinforced by silicon carbide particles is investigated using a new method of double multivariate nonlinear regression (DMNR) in which the strain, strain rate, deformation temperature, and the interaction effect among the strain, strain rate, and deformation temperature are considered. The experimental true stress-strain data were obtained by isothermal hot compression tests on a Gleeble-3500 thermo-mechanical simulator in the temperature range of 623-773 K and the strain rate range of 0.001-10 s-1. The experiments showed that the material-softening behavior changed with the strain rate, and it changed from dynamic recovery to dynamic recrystallization with an increase in the strain rate. A new constitutive equation has been established by the DMNR; the correlation coefficient ( R) and average absolute relative error (AARE) of this model are 0.98 and 7.8%, respectively. To improve the accuracy of the model, separate constitutive relationships were obtained according to the softening behavior. At strain rates of 0.001, 0.01, 0.1, and 1 s-1, the R and AARE are 0.9865 and 6.0%, respectively; at strain rates of 5 and 10 s-1, the R and AARE are 0.9860 and 3.0%, respectively. The DMNR gives an accurate and precise evaluation of the flow stress for the aluminum alloy reinforced by silicon carbide particles.

  16. Analysis of interfacial debonding in shape memory alloy wire-reinforced composites

    NASA Astrophysics Data System (ADS)

    Miramini, A.; Kadkhodaei, M.; Alipour, A.; Mashayekhi, M.

    2016-01-01

    One of the common types of failure in shape memory alloy (SMA) wire-reinforced composites is interfacial debonding between the fiber and the matrix. In this paper, a three dimensional finite element model for an SMA wire-reinforced composite is developed based on cohesive zone modeling to predict interfacial debonding between the SMA wire and the surrounding matrix. The interfacial debonding is also experimentally investigated by conducting a number of pull-out tests on steel as well as Nitinol wires embedded in an epoxy matrix. To evaluate the presented method, the developed finite element analysis is employed to simulate a single wire pull-out test for ordinary (e.g. steel) wires. In order to simulate SMA wire pull-out, a 3D SMA constitutive model is implemented into the commercial finite element software ABAQUS using a user material subroutine (UMAT). An acceptable agreement is shown to exist between the theoretical results and the experimental data, indicating the efficiency of the proposed approach to model interfacial debonding in SMA wire-reinforced composites.

  17. Characterization of reinforcement distribution in cast Al-alloy/SiC{sub p} composites

    SciTech Connect

    Karnezis, P.A.; Durrant, G.; Cantor, B.

    1998-02-01

    The distribution of reinforcement in 10% SiC and 20% SiC{sub p} reinforced A356 alloy processed by gravity casting, squeeze casting, and roll casting is studied by using the mean free path, nearest neighbor distance, radial distribution function, and quadrat methods. The study is performed by using computer image analysis methods in an automated procedure to prevent operator errors, improve sample size, and minimize analysis time. From the methods used to characterize the SiC{sub p} distributions, the quadrat method and radial distribution function are found to be more effective in detecting pronounced changes in the metal-matrix composite (MMC) microstructure through appropriate parameters, whereas the mean free path is characteristic of the particular MMC system rather than process specific. Furthermore, the nearest neighbor distance is of little use in studying cast MMCs, because it is affected by local clusters of a few SiC particles commonly found in cast MMCs, thus failing to characterize the macroscopic arrangement of reinforcement. Quantitative methods present themselves as a useful tool for quality control in MMC fabrication and can be used to correlate particle distribution and properties of MMC systems.

  18. Effect of Alloying Elements on Tensile Properties, Microstructure, and Corrosion Resistance of Reinforcing Bar Steel

    NASA Astrophysics Data System (ADS)

    Panigrahi, B. K.; Srikanth, S.; Sahoo, G.

    2009-11-01

    The effect of copper, phosphorus, and chromium present in a semikilled reinforcing bar steel produced by in-line quenching [thermomechanical treatment (TMT)] process on the tensile properties, microstructure, and corrosion resistance of steel in simulated chloride environment has been investigated. The results have been compared with that of a semikilled C-Mn reinforcing bar steel without these alloying elements produced by the same process route. Though the amount of phosphorus (0.11 wt.%) was higher than that specified by ASTM A 706 standard, the Cu-P-Cr steel exhibited a composite microstructure, and good balance of yield stress, tensile stress, elongation, and ultimate tensile to yield stress ratio. Two conventional test methods, namely, the salt fog, and potentiodynamic polarization tests, were used for the corrosion test. The rust formed on Cu-P-Cr steel was adherent, and was of multiple colors, while the corrosion products formed on the C-Mn steel were weakly adherent and relatively darker blue. Also, the free corrosion potential of the Cu-P-Cr steel was nobler, and the corrosion current was markedly lower than that of a C-Mn rebar. The Cu-P-Cr steel did not develop any pits/deep grooves on its surface even after the prolonged exposure to salt fog. The improved corrosion resistance of the Cu-P-Cr steel has been attributed to the presence of copper, phosphorus, and small amount of chromium in the dense, adherent rust layer on the surface of reinforcing steel bar. A schematic mechanism of charge transfer has been proposed to explain the improved corrosion resistance of the Cu-P-Cr alloyed TMT rebar.

  19. Bondability of Al-Si thin film in thermosonic gold wire bonding. [integrated circuits

    NASA Technical Reports Server (NTRS)

    Nakagawa, K.; Miyata, K.; Banjo, T.; Shimada, W.

    1985-01-01

    The bondability of two kinds of Al-Si thin films in thermosonic Au wire bonding was examined by means of microshear tests. One type of film was formed by sputtering an Al-2% Si alloy, and the other was formed by depositing an 0.05 micrometer-thick polysilicon layer on SiO2 by chemical vapor deposition (CVD) and then depositing a 1.2 micrometer-thick Al layer on them by evaporation. After heat-treatment at 450 deg for 30 min., Si in the Al-Si film crystallized. The grain size of the crystallized Si affects the thermosonic wire bondability, i.e., for Al-2% Si sputtered films, good bondability was obtained under relatively small (1.0 micrometer) grain size conditions. In the successive layer process, on the other hand, the grain size of crystallized Si varies with the polysilicon CVD temperature. The optimum CVD temp. was determined from the standpoint of bondability with respect to grain size.

  20. Dry Sliding Wear Behaviour of Flyash Reinforced ZA-27 Alloy Based Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Krishna, M.; Bhattacharyya, D.

    In the present investigation, an attempt has been made to evaluate the wear rate of ZA-27 alloy composites reinforced with fly ash particles from 1 to 3 wt% in steps of 1 wt%. The compo-casting method has been used to fabricate the composites using Raichur fly ash of average size 3-5 microns. The wear specimens are tested under dry conditions using a pin-on-disc sliding wear testing machine with wear loads of 20-120 N in steps of 20 N, and the sliding distances in the range of 0.5 km to 2.5 km. The results indicate that the wear rate of the composites is less than that of the matrix alloy and it further decreases with the increase in fly ash content. However, the material loss in terms of wear rate and wear volume increases with the increase in load and sliding distance, both in the cases of composites and the matrix alloy. An increase in the applied load increases the wear severity by changing the wear mechanism from abrasion to particle-cracking induced delamination wear. It is found that with the increase in fly ash content, the wear resistance increases monotonically. The observations have been explained using scanning electron microscope (SEM) analysis of the worn surfaces of the composites.

  1. Strength of MWCNT-Reinforced 70Sn-30Bi Solder Alloys

    NASA Astrophysics Data System (ADS)

    Billah, Md Muktadir; Chen, Quanfang

    2016-01-01

    In this study, the effect of Cu-coated multi-walled carbon nanotubes (MWCNTs) on the tensile strength of 70Sn-30Bi solder alloy has been investigated. Copper was first deposited onto metal-activated MWCNTs by an electroless process and confirmed with a scanning electron microscope and energy dispersive spectroscopy. Sn-Bi alloy solder was reinforced with Cu-coated MWCNTs with additions of 0.5 wt.%, 1 wt.%, 2 wt.%, and 3 wt.%, respectively. 70Sn-30Bi solder was produced by melting pure tin and bismuth in an inert gas atmosphere. Cu-coated MWCNTs were then added into the metal matrix by cold rolling, followed by hot pressing to disperse the carbon nanotubes (CNTs) in the matrix. Tensile tests were conducted on an mechanical testing and simulation (MTS) tester. The tensile strength was found to be proportional to the addition of Cu/MWCNTs, and about 47.6% increase in tensile strength over the pure alloy has been obtained for an addition of 3 wt.% Cu/MWCNTs. The Cu coating may enhance CNT dispersion to prevent tangling.

  2. Wear response of a Zn-base alloy in the presence of SiC particle reinforcement: A comparative study with a copper-base alloy

    SciTech Connect

    Prasad, B.K.; Das, S.; Modi, O.P.; Jha, A.K.; Dasgupta, R.; Yegneswaran, A.H.

    1999-12-01

    An attempt has been made in this study to examine the effects produced by the reinforcement of (10 wt%) SiC particles on the sliding wear behavior of a Zn-base alloy. The matrix alloy was also subjected to identical test conditions to assess the influence of the SiC dispersoid phase. The wear characteristics of the (Zn-base alloy) composite and the matrix alloy were also compared with those of a Cu-base alloy (i.e., an aluminum bronze) in order to understand the scope of exploiting the Zn-base alloy matrix/composite as a substitute material for the latter (Cu-base) alloy. It has been observed that low frictional heat generated at the lower sliding speed (0.42 m/s) enabled the Zn-base (matrix) alloy to perform better than the composite material, while the Cu-base alloy showed intermediate wear resistance. On the contrary, the trend changed at a higher sliding speed (4.62 m/s) when high frictional heating caused the wear behavior of the Cu-base alloy to be superior to that of the Zn-base (matrix) alloy. The composite in this case performed better than the matrix alloy. The wear behavior of the specimens has been explained in terms of factors like microcracking tendency and thermal stability introduced by the SiC dispersoid phase and lubricating, load bearing, and low melting characteristics of microconstituents like {alpha} and {eta} in the (Zn-base) alloy system and the thermal stability of the Cu-base alloy. It seems that the predominance of one set of parameters over the other actually controls the overall performance of a material. Once again, it is the test conditions that ultimately allow a particular set of factors to govern the other and influence the response of the specimens accordingly. The observed wear behavior of the samples has been substantiated further with their wear surface characteristics.

  3. Metallic Reinforcement of Direct Squeeze Die Casting Aluminum Alloys for Improved Strength and Fracture Resistance

    SciTech Connect

    D. Schwam: J.F. Wallace: Y. Zhu: J.W. Ki

    2004-10-01

    The utilization of aluminum die casting as enclosures where internal equipment is rotating inside of the casting and could fracture requires a strong housing to restrain the fractured parts. A typical example would be a supercharger. In case of a failure, unless adequately contained, fractured parts could injure people operating the equipment. A number of potential reinforcement materials were investigated. The initial work was conducted in sand molds to create experimental conditions that promote prolonged contact of the reinforcing material with molten aluminum. Bonding of Aluminum bronze, Cast iron, and Ni-resist inserts with various electroplated coatings and surface treatments were analyzed. Also toughening of A354 aluminum cast alloy by steel and stainless steel wire mesh with various conditions was analyzed. A practical approach to reinforcement of die cast aluminum components is to use a reinforcing steel preform. Such performs can be fabricated from steel wire mesh or perforated metal sheet by stamping or deep drawing. A hemispherical, dome shaped casting was selected in this investigation. A deep drawing die was used to fabricate the reinforcing performs. The tendency of aluminum cast enclosures to fracture could be significantly reduced by installing a wire mesh of austenitic stainless steel or a punched austenitic stainless steel sheet within the casting. The use of reinforcements made of austenitic stainless steel wire mesh or punched austenitic stainless steel sheet provided marked improvement in reducing the fragmentation of the casting. The best strengthening was obtained with austenitic stainless steel wire and with a punched stainless steel sheet without annealing this material. Somewhat lower results were obtained with the annealed punched stainless steel sheet. When the annealed 1020 steel wire mesh was used, the results were only slightly improved because of the lower mechanical properties of this unalloyed steel. The lowest results were

  4. The effect of Co alloying content on the kinetics of reaction zone growth in tungsten fiber reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Rodriguez, A.; Tien, J. K.; Caulfield, T.; Petrasek, D. W.

    1988-01-01

    A Co-free modified superalloy similar in composition to Waspaloy is investigated in an effort to understand the effect of Co on reaction zone growth kinetics and verify the chemistry dependence of reaction zone growth in the matrix of tungsten fiber reinforced superalloy composites. The values of the parabolic rate constant, characterizing the kinetics of reaction zone growth, for the Waspaloy matrix and the C-free alloy as well as five other alloys from a previous study confirm the dependence of reaction zone growth kinetics on cobalt content of the matrix. The Co-free alloy composite exhibits the slowest reaction zone growth among all tungsten fiber reinforced composites studied to date.

  5. Design and performance of a shape memory alloy-reinforced composite aerodynamic profile

    NASA Astrophysics Data System (ADS)

    Simpson, J. C.; Boller, C.

    2008-04-01

    Based on a shape memory alloy (SMA)-reinforced composite developed separately, the applicability of the composite has been demonstrated through realization of a realistically scaled aerodynamic profile of around 0.5 m span by 0.5 m root chord whose skins had been made from this composite. The design, manufacturing and assembly of the profile are described. The curved skins were manufactured with two layers of SMA wires integrated into the layup of aramid fibre prepregs. All SMA wires were connected such that they can be operated as individual sets of wires and at low voltages, similar to the conditions for electrical energy generation in a real aircraft. The profile was then mounted on a vibration test rig and excited by a shaker at its tip which allowed the dynamic performance of the profile to be validated under internal actuation conditions generated through the SMA wires.

  6. Aging effects on the fracture toughness of SiC whisker reinforced 2XXX aluminum alloys

    NASA Technical Reports Server (NTRS)

    Ratnaparkhi, P. L.; Rack, H. J.

    1989-01-01

    The effect of aging (at 150 C) time on the fracture toughness behavior of a 2XXX alloy (Al-3.55Cu-1.29Mg-0.01Fe-trace Mn) reinforced with 5 vol pct F-8 SiC whiskers was investigated by measuring hardness and electrical conductivity followed by fracture toughness tests on center-cracked specimens. The ageing time-hardening response plots showed that, independent of whisker orientation, the initial rapid increase in hardness was followed by a more gradual increase, with a broad hardness peak between 32 and 128 hrs of aging. Coincident with the hardness changes, the electrical conductivity initially decreased, reached a minimum, and then increased at aging times beyond 32 hrs. Examination by SEM indicated that the initial increase in hardness and decrease in conductivity was due to the GPB zone formation, while the subsequent increase in electrical conductivity and decrease in hardness (overaging) was due to S nucleation and growth.

  7. Compressive strength of titanium alloy skin-stringer panels selectively reinforced with boron-aluminum composite.

    NASA Technical Reports Server (NTRS)

    Herring, H. W.; Carri, R. L.

    1972-01-01

    Description of a method of selectively reinforcing conventional titanium airframe structure with unidirectional boron-aluminum composite attached by brazing which has been successfully demonstrated based on compression tests of short skin-stringer panels. Improvements in structural performance exceeded 25% on an equivalent weight basis over the range from room temperature to 800 F, both in terms of initial buckling and maximum strengths. Room-temperature performance was not affected by prior exposure at 600 F for 1000 hours in air, or by 400 cycles between -65 and 600 F. The experimental results were generally predictable on the basis of existing analytical procedures. No evidence of failure was observed in the braze bond between the boron-aluminum composite and the titanium alloy.

  8. The failure of notched specimens of boron-fiber reinforced 6061 aluminum alloy

    NASA Technical Reports Server (NTRS)

    Wright, M. A.; Iannuzzi, F. A.

    1974-01-01

    The effect of notches on the strength of boron fiber reinforced 6061 aluminum alloy was determined at room temperature, 300 F, and 600 F. Both unidirectional and cross-plied specimens were tested. The strengths of individual fibers were measured, and upper and lower bounds of composite strength were calculated using bundle theory. Fracture tests were performed on specimens containing center slots of various lengths, and the values of the critical stress intensity factor for initial crack propagation or final failure were calculated. For unidirectional specimens, these parameters depended on thickness; for cross-plied specimens, fairly constant values were obtained at room temperature. The cross-plied material invariably failed at a lower stress as the environmental temperature was raised.

  9. Separation and purification of Si from solidification of hypereutectic Al-Si melt under rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Jie, J. C.; Zou, Q. C.; Wang, H. W.; Sun, J. L.; Lu, Y. P.; Wang, T. M.; Li, T. J.

    2014-08-01

    A low-cost and high-efficiency method to purify Si directly from cheap MG-Si at low temperature was proposed and demonstrated in this paper, which used power frequency rotating magnetic field (RMF) to separate the primary Si from a hypereutectic Al-Si alloy and was followed by the acid peeling. The separation mechanism was based on the flow characteristic of melt under RMF and the cooling condition of the liquid metal. A Si-rich layer with Si content of 65-59 wt% was formed in the periphery of alloy, while the inner microstructure of the alloy was mainly the Al-Si eutectic structure. The refined silicon was collected after aqua regia leaching, and had much fewer typical impurities (Fe, Ti, Ca, B, P) than those in MG-Si, and the metallic impurities besides Al had removal fraction higher than 98%, which is mainly ascribed to the segregation effect of Al-30Si alloy during solidification under RMF.

  10. Dissimilar friction stir welding of aluminum alloys reinforced with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pantelis, D. I.; Karakizis, P. N.; Dragatogiannis, D. A.; Charitidis, C. A.

    2016-01-01

    This chapter is devoted to studying the possibility of incorporating carbon nanotubes (CNTs) as reinforcing fillers in dissimilar metal matrices joints produced by friction stir welding (FSW), as well as the impact of this incorporation on the microstructural and mechanical properties of these joints. Carbon nanotubes are extensively used as a reinforcing material in nanocomposites, due to their high stiffness and strength. FSW is a solid-state welding process of joining aluminum and other metallic alloys and has been employed in the aerospace, rail, automotive, and marine industries. Recently, friction stir processing (FSP), a derivative method of FSW, has been employed as an alternative for the production of metal matrix composites (MMCs). In this work, the process parameters were optimized in order to achieve nondefective welds, with and without the addition of CNTs. Two main cases were studied: (1) FSP was optimized by changing the tool rotational and travel speed as well as the number and direction of FSW passes, and (2) a Taguchi design scheme was adopted to further investigate the FSP in relevance to three factors (number, direction of passes, and tool rotational speed). Mechanical behavior was studied, and the local mechanical properties of the produced MMCs were compared with their bulk counterparts and parent materials. More specifically, the measured mechanical properties in the micro- and nanoscale (namely hardness and elastic modulus) are correlated with the microstructure and the presence of fillers.

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

    PubMed

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

    2013-01-01

    Power ultrasonic vibration (20 kHz, 6 μm) was applied to assist the interaction between a liquid Al-Si alloy and solid Ti-6Al-4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti-6Al-4V surface, chemical dissolution of solid Ti-6Al-4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2-20 μm diameter-sized pits formed on the Ti-6Al-4V surface. Propagation of ultrasonic waves in the liquid Al-Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti-6Al-4V substrate, excessive chemical dissolution of solid Ti-6Al-4V into liquid Al-Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al-Si and Ti-6Al-4V can be produced by ultrasonic-assisted brazing in air. PMID:22824641

  12. Improved Wear Resistance of Al-Mg Alloy with SiC and Al2O3 Particle Reinforcement

    NASA Astrophysics Data System (ADS)

    Mehedi, Md. A.; Bhadhon, K. M. H.; Haque, M. N.

    2016-01-01

    Al-3.73Mg alloy was reinforced with a different ratio of SiC and Al2O3 particulate mixtures, and their corresponding wear properties were investigated by pin-on-disk method. The investigation revealed that the mass loss of the hybrid composite at different loads and sliding velocities reduced with the increase of the SiC volume. Only 6% particulate reinforcement in the Al-Mg matrix was enough to reduce the wear of the surface by one-fourth. The wear mechanism was also investigated by examining the worn surface with a scanning electron microscope.

  13. Microstructure Changes in Isochronally Annealed Alumina Fibre Reinforced Mg-Ag-Nd-Zr Alloy

    NASA Astrophysics Data System (ADS)

    Kiehn, J.; Smola, B.; Vostrý, P.; Stulíková, I.; Kainer, K. U.

    1997-12-01

    The commercial alloy QE22 (Mg-Ag-;Nd-Zr alloy) was reinforced by 22 vol% -Al2O3 short fibres applying the squeeze cast technology. Precipitation effects were studied in this material after a preceding solution heat treatment by isochronal annealing up to 300 °C by means of electrical resistivity, hardness and reversible stress relaxation measurements. The annealing response of the properties was compared to the annealing response of the unreinforced matrix alloy. The microstructure changes were studied in detail by transmission electron microscopy. A sharp drop of resistivity between 180 and 280 °C was found on normalised resistivity annealing curves of both reinforced and unreinforced specimens due to the redistribution of solutes. In composites the fibres act as nucleation centres in the precipitation process promoting e.g. precipitation of Al2Nd or Ag compounds. The Al content in the matrix is enhanced due to the decomposition of the preform binder. The evolution of the particle population inside the grains involves the formation of new Al2Nd-like cubic particles between 120 and 180 °C. Above 180 °C these particles are continuously substituted by hexagonal -phase and/or tetragonal Mg12Nd particles. This process finishes at 300 °C by the transformation of all new particles to semicoherent Mg12Nd precipitates. The precipitation process in grain interiors of the unreinforced alloy is different involving only change of the morphological features of tetragonal semicoherent Mg12Nd particles existing in the alloy already in the initial state after solution heat treatment. Die kommerzielle Legierung QE22 (Mg-Ag-Nd-Zr) wurde im Preßgießverfahren mit 22 Vol.-% δ-Al2O3 Kurzfasern verstärkt. Die Untersuchung des Ausscheidungsverhaltens während isochroner Wärmebehandlungen bis 300 °C nach vorangegangenem Lösungsglühen erfolgte über die Bestimmung der Änderung des elektrischen Widerstandes, der Härte und der reversiblen Spannungsrelaxation. Die Auswirkung der

  14. The strength characterization of Al/Si interfaces with a hybrid nanoindentation/FEM method

    NASA Astrophysics Data System (ADS)

    Xia, Shuman; Qi, Yue; Perry, Thomas A.; Kim, Kyung-Suk

    2008-03-01

    The mechanical property characterization of the reinforcement/matrix interface in a metal matrix composite (MMC) is entailed for tailoring the interface in the microstructure design of the composite. In this work we developed a hybrid method to characterize the interface strength of an MMC, combining a nanoindentation experiment and a finite element analysis. The nanoindentation experiment was carried out by indenting individual reinforcement particles on a free surface with a nanoindenter. The dependence of indentation response on the interface properties was systematically studied through the finite element analysis with cohesive zone modeling of the interface failure. The interface strength could then be extracted from the comparison between the experimental and FEM results. With this method, the shear strength of an Al/Si interface was measured approximately 240MPa which compares well with the lower bound of an atomistic simulation with a modified EAM potential. The intrinsic fracture toughness of the interface crack tip surrounded by densely populated dislocations was measured 0.25 J/m2. We also studied the effect of the strontium modification on the interface strength with this hybrid method.

  15. Numerical Evaluation Of Shape Memory Alloy Recentering Braces In Reinforced Concrete Buildings Subjected To Seismic Loading

    NASA Astrophysics Data System (ADS)

    Charles, Winsbert Curt

    Seismic protective techniques utilizing specialized energy dissipation devices within the lateral resisting frames have been successfully used to limit inelastic deformation in reinforced concrete buildings by increasing damping and/or altering the stiffness of these structures. However, there is a need to investigate and develop systems with self-centering capabilities; systems that are able to assist in returning a structure to its original position after an earthquake. In this project, the efficacy of a shape memory alloy (SMA) based device, as a structural recentering device is evaluated through numerical analysis using the OpenSees framework. OpenSees is a software framework for simulating the seismic response of structural and geotechnical systems. OpenSees has been developed as the computational platform for research in performance-based earthquake engineering at the Pacific Earthquake Engineering Research Center (PEER). A non-ductile reinforced concrete building, which is modelled using OpenSees and verified with available experimental data is used for the analysis in this study. The model is fitted with Tension/Compression (TC) SMA devices. The performance of the SMA recentering device is evaluated for a set of near-field and far-field ground motions. Critical performance measures of the analysis include residual displacements, interstory drift and acceleration (horizontal and vertical) for different types of ground motions. The results show that the TC device's performance is unaffected by the type of ground motion. The analysis also shows that the inclusion of the device in the lateral force resisting system of the building resulted in a 50% decrease in peak horizontal displacement, and inter-story drift elimination of residual deformations, acceleration was increased up to 110%.

  16. Selective Laser Melting Additive Manufacturing of TiC/AlSi10Mg Bulk-form Nanocomposites with Tailored Microstructures and Properties

    NASA Astrophysics Data System (ADS)

    Gu, Dongdong; Wang, Hongqiao; Chang, Fei; Dai, Donghua; Yuan, Pengpeng; Hagedorn, Yves-Christian; Meiners, Wilhelm

    The nanoscale TiC particle reinforced AlSi10Mg nanocomposite parts were produced by selective laser melting (SLM) additive manufacturing process. The influence of laser energy density (LED) on densification behavior, microstructural evolution, microhardness and wear properties of SLM-processed TiC/AlSi10Mg nanocomposites was studied. It showed that the near fully dense nanocomposite parts (>98% theoretical density) were achieved with increasing the applied LED. The TiC reinforcement in SLM-processed parts experienced a microstructural change from the standard nanoscale particle morphology (the average size 77-93 nm) to the relatively coarsened submicron structure (the mean particle size 154 nm) as the LED increased.The sufficiently high densification rate combined with the homogeneousdistribution of nanoscale TiC reinforcement throughout the matrix led to a high microhardness of 181.2 HV0.2, a considerably low coefficient of friction (COF) of 0.36, and a reduced wear rate of 2.94×10-5 mm3N-1m-1 for SLM-processed TiC/AlSi10Mg nanocomposite parts.

  17. Laser shock processing of Al-SiC composite coatings

    NASA Astrophysics Data System (ADS)

    Schnick, T.; Steinhäuser, S.; Wielage, B.; Hofmann, U.; Tondu, S.; Peyre, P.; Bartnicki, E.; Pawlowski, L.

    1999-06-01

    Laser shock processing (LSP) is a technique of surface treatment (similar to shot peening) in which laser-induced mechanical shocks develop compressive stresses in the material. The stresses are of sufficient intensity to modify microstructure and properties of the coatings. In the present study, laser shocks of power density of 5 to 8 GW/cm2 power density, generated by means of a neodymium-glass laser, were used to treat Al + SiC composite coatings deposited by means of a HVOF spraying technique. The laser processed samples were metallographically prepared, and their microstructure was investigated by optical microscope and SEM. The latter was also used to investigate the surface morphology of the laser treated specimens. Finally, the microhardness and oscillating wear resistance of the coatings were tested and compared to data obtained for as-sprayed samples.

  18. Improving the corrosion wear resistance of AISI 316L stainless steel by particulate reinforced Ni matrix composite alloying layer

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Zhuo, Chengzhi; Tao, Jie; Jiang, Shuyun; Liu, Linlin

    2009-01-01

    In order to overcome the problem of corrosion wear of AISI 316L stainless steel (SS), two kinds of composite alloying layers were prepared by a duplex treatment, consisting of Ni/nano-SiC and Ni/nano-SiO2 predeposited by brush plating, respectively, and subsequent surface alloying with Ni-Cr-Mo-Cu by a double glow process. The microstructure of the two kinds of nanoparticle reinforced Ni-based composite alloying layers was investigated by means of SEM and TEM. The electrochemical corrosion behaviour of composite alloying layers compared with the Ni-based alloying layer and 316L SS under different conditions was characterized by potentiodynamic polarization test and electrochemical impedance spectroscopy. Results showed that under alloying temperature (1000 °C) conditions, amorphous nano-SiO2 particles still retained the amorphous structure, whereas nano-SiC particles were decomposed and Ni, Cr reacted with SiC to form Cr6.5Ni2.5Si and Cr23C6. In static acidic solution, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is lower than that of the Ni-based alloying layer. However, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is prominently superior to that of the Ni-based alloying layer under acidic flow medium condition and acidic slurry flow condition. The corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiC particles interlayer is evidently lower than that of the Ni-based alloying layer, but higher than that of 316L SS under all test conditions. The results show that the highly dispersive nano-SiO2 particles are helpful in improving the corrosion wear resistance of the Ni-based alloying layer, whereas carbides and silicide phase are deleterious to that of the Ni-based alloying layer due to the fact that the preferential removal of the matrix around the precipitated phase takes place by the chemical

  19. Rapid Solidification: Selective Laser Melting of AlSi10Mg

    NASA Astrophysics Data System (ADS)

    Tang, Ming; Pistorius, P. Chris; Narra, Sneha; Beuth, Jack L.

    2016-03-01

    Rapid movement of the melt pool (at a speed around 1 m/s) in selective laser melting of metal powder directly implies rapid solidification. In this work, the length scale of the as-built microstructure of parts built with the alloy AlSi10Mg was measured and compared with the well-known relationship between cell size and cooling rate. Cooling rates during solidification were estimated using the Rosenthal equation. It was found that the solidification structure is the expected cellular combination of silicon with α-aluminum. The dependence of measured cell spacing on calculated cooling rate follows the well-established relationship for aluminum alloys. The implication is that cell spacing can be manipulated by changing the heat input. Microscopy of polished sections through particles of the metal powder used to build the parts showed that the particles have a dendritic-eutectic structure; the dendrite arm spacings in metal powder particles of different diameters were measured and also agree with literature correlations, showing the expected increase in secondary dendrite arm spacing with increasing particle diameter.

  20. Electro-bending characterization of adaptive 3D fiber reinforced plastics based on shape memory alloys

    NASA Astrophysics Data System (ADS)

    Ashir, Moniruddoza; Hahn, Lars; Kluge, Axel; Nocke, Andreas; Cherif, Chokri

    2016-03-01

    The industrial importance of fiber reinforced plastics (FRPs) is growing steadily in recent years, which are mostly used in different niche products, has been growing steadily in recent years. The integration of sensors and actuators in FRP is potentially valuable for creating innovative applications and therefore the market acceptance of adaptive FRP is increasing. In particular, in the field of highly stressed FRP, structural integrated systems for continuous component parts monitoring play an important role. This presented work focuses on the electro-mechanical characterization of adaptive three-dimensional (3D)FRP with integrated textile-based actuators. Here, the friction spun hybrid yarn, consisting of shape memory alloy (SMA) in wire form as core, serves as an actuator. Because of the shape memory effect, the SMA-hybrid yarn returns to its original shape upon heating that also causes the deformation of adaptive 3D FRP. In order to investigate the influences of the deformation behavior of the adaptive 3D FRP, investigations in this research are varied according to the structural parameters such as radius of curvature of the adaptive 3D FRP, fabric types and number of layers of the fabric in the composite. Results show that reproducible deformations can be realized with adaptive 3D FRP and that structural parameters have a significant impact on the deformation capability.

  1. Effects of stress concentration on the fatigue strength of 7003-T5 aluminum alloy butt joints with weld reinforcement

    NASA Astrophysics Data System (ADS)

    Zhu, Zongtao; Li, Yuanxing; Zhang, Mingyue; Hui, Chen

    2015-03-01

    7003-T5 Aluminum (Al) alloy plates with a thickness of 5 mm are welded by gas metal arc welding (GMAW) method in this work. In order to investigate the influence of stress concentration introduced by weld reinforcement on fatigue strength, the stress concentration factor of the butt joint is calculated. Microscopic and X-ray techniques were utilized to make sure there are no weld defects with large size in butt weld, which can induce extra stress concentration. The cyclic stress - number of cycles to failure (S-N) curves of the joints with and without the welder were obtained by fatigue testing, and the results show that the fatigue strength of 7003-T5 Al alloy butt joints with the weld reinforcement is 50 MPa, which is only 45% of the joints without the weld reinforcement. Fracture surface observation indicated that the fatigue source and propagation are dissimilar for the specimens with and without the welder due to the stress concentration at the weld root. The stress concentration with a factor of 1.7 has great effect on the fatigue strength, but little influence on the tensile strength.

  2. Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders

    SciTech Connect

    Johnson, Matthew ); Weyant, J.; Garner, S. ); Occhionero, M. )

    2010-01-07

    Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate’s effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.

  3. Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

    NASA Astrophysics Data System (ADS)

    Wang, Linzhi; Liu, Ying; Chang, Sen

    2016-05-01

    Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

  4. Study on reinforced concrete beams strengthened using shape memory alloy wires in combination with carbon-fiber-reinforced polymer plates

    NASA Astrophysics Data System (ADS)

    Li, Hui; Liu, Zhi-qiang; Ou, Jin-ping

    2007-12-01

    It has been proven that carbon-fiber-reinforced polymer (CFRP) sheets or plates are capable of improving the strength of reinforced concrete (RC) structures. However, residual deformation of RC structures in service reduces the effect of CFRP strengthening. SMA can be applied to potentially decrease residual deformation and even close concrete cracks because of its recovery forces imposed on the concrete when heated. Therefore, a method of a RC structure strengthened by CFRP plates in combination with SMA wires is proposed in this paper. The strengthening effect of this method is investigated through experiments and numerical study based on the nonlinear finite element software ABAQUS in simple RC beams. Parametric analysis and assessment of damage by defining a damage index are carried out. The results indicate that recovery forces of SMA wires can decrease deflections and even close cracks in the concrete. The recovery rate of deflection of the beam increases with increasing the ratio of SMA wires. The specimen strengthened with CFRP plates has a relatively large stiffness and smaller damage index value when the residual deformation of the beam is first reduced by activation of the SMA wires. The effectiveness of this strengthening method for RC beams is verified by experimental and numerical results.

  5. Thermal- and electromigration-induced stresses in passivated Al- and AlSiCu-interconnects

    SciTech Connect

    Beckers, D.; Schroeder, H.; Schilling, W.; Eppler, I.

    1997-05-01

    Mechanical stresses in microelectronic devices are of special interest because of degradation effects in microelectronic circuits such as stress induced voiding or electromigration. Al and al-alloys are commonly used as interconnect materials in integrated electronic devices. Stress induced voiding and degradation of metal lines by electromigration are closely related to the stresses in the lines. The authors have studied the strain and stress evolution during thermal cycling, isothermal relaxation and due to electromigration in passivated Al and AlSi(1%)Cu(0.5%) lines by X-Ray diffraction with variation of experimental parameters such as the aspect ratio and the electrical current density. Furthermore the extent of voiding and plastic shear deformation has been determined from the experimental metal strains with the help of finite element calculations. Main results are: (1) During thermal cycling the voiding is less than 2 {center_dot} 10{sup {minus}3}. The extent of plastic shear deformation increases with increasing line width and with decreasing flowstress. (2) During isothermal relaxation void growth occurs but no significant change in the plastic shear deformation. (3) An electric current in the lines causes no measurable additional change of the volume averaged stresses up to line failure.

  6. Enhancing tensile ductility of a particulate-reinforced aluminum MMC by lamination with Mg-9% Li alloy

    SciTech Connect

    Syn, C.K.; Lesuer, D.R.; Sherby, O.D.

    1995-05-01

    A laminated metal composite has been made by press bonding alternating layers of a particulate-reinforced aluminum MMC, 6090/SiC/25p, and a Mg-9%Li alloy. The mechanical properties including tensile ductility were evaluated. The tensile ductility of the Al MMC was found to increase from 3.5% to 11.5%. In contrast to other laminates based on ultrahigh carbon, steel, the laminate of this study and other Al MMC laminates exhibited tensile yield strengths that did not follow the rule of averages. This is attributed to interlayer reaction products developed during processing of the Al MMC laminates.

  7. Improvement in Microstructure Performance of the NiCrBSi Reinforced Coating on TA15 Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Peng, Li

    2012-10-01

    This work is based on the dry sliding wear of NiCrBSi reinforced coating deposited on TA15 titanium alloy using the laser cladding technique, the parameters of which were such as to provide almost crack-free coatings with minimum dilution and very low porosity. SEM results indicated that a laser clad coating with metallurgical joint to the substrate was formed. Compared with TA15 substrate, an improvement of the micro-hardness and wear resistance was observed for this composite coating. Rare earth oxide Y2O3 was beneficial in producing of the amorphous phases in laser clad coating. With addition of Y2O3, more amorphous alloys were produced, which increased the micro-hardness and wear resistance of the coating.

  8. Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

    SciTech Connect

    Soh, Wee Tee; Ong, C. K.; Zhong, Xiaoxi

    2014-09-15

    FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.

  9. Spray-forming monolithic aluminum alloy and metal matrix composite strip

    SciTech Connect

    McHugh, K.M.

    1995-10-01

    Spray forming with de Laval nozzles is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. Using this approach, aluminum alloys have been spray formed as strip, with technoeconomic advantages over conventional hot mill processing and continuous casting. The spray-formed strip had a flat profile, minimal porosity, high yield, and refined microstructure. In an adaptation to the technique, 6061 Al/SiC particulate-reinforced metal matrix composite strip was produced by codeposition of the phases.

  10. Effects of water absorption of dielectric underlayers on Al-Si-Cu film properties and electromigration performance in Al-Si-Cu/Ti/TiN/Ti interconnects

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1998-01-01

    The effects of underlying dielectric (phosphosilicate glass and borophosphosilicate glass) films to a humid air ambient on Al-Si-Cu film properties and electromigration (EM) performance in Al-Si-Cu/Ti/TiN/Ti layered films have been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered films was found to improve drastically with increasing boron content and exposure time. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and grain sizes increase as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. Further, it was demonstrate that interconnects fabricated from the improved layered film have excellent EM performance.

  11. Diffusion bonding of an aluminum-copper alloy reinforced with silicon carbide particles (AA2014/SiC/13p) using metallic interlayers

    SciTech Connect

    Urena, A.; Gomez de Salazar, J.M.; Escalera, M.D.

    1996-12-01

    In this work, the application of solid state diffusion bonding to a SiC particulate reinforced aluminium-copper alloy (AA2014) has been studied. The use of metallic interlayers such as an aluminum-lithium alloy and pure silver, has been tested. Bonding interfaces were microstructural characterized using scanning electron (SEM) and transmission electron microscopies (TEM). Joint strengths were evaluated by shear mechanical tests, completed with fractographic studies to determine the failure mechanisms of each kind of joint.

  12. Growth and deformation structure of gradient and layer-gradient Ti-Al-Si-Cu-N coatings

    SciTech Connect

    Ovchinnikov, Stanislav V. Pinzhin, Yurii P.; Korotaev, Alexandr D.

    2014-11-14

    The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer.

  13. Vacuum brazing of high volume fraction SiC particles reinforced aluminum matrix composites

    NASA Astrophysics Data System (ADS)

    Cheng, Dongfeng; Niu, Jitai; Gao, Zeng; Wang, Peng

    2015-03-01

    This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al-Si-Cu-Zn-Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

  14. Influence of Stored Strain on Fabricating of Al/SiC Nanocomposite by Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Khorrami, M. Sarkari; Kazeminezhad, M.; Kokabi, A. H.

    2015-05-01

    In this work, 1050 aluminum (Al) sheets were annealed and severely deformed by 1, 2, and 3 passes of constrained groove pressing process to obtain the various initial stored strain values of 0, 1.16, 2.32, and 3.48, respectively. Friction stir processing (FSP) was then applied using SiC nanoparticles to fabricate Al/SiC nanocomposite with approximately 1.5 vol pct reinforced particles. Microstructural examinations revealed that an increase in the initial stored strain of the base metal led to the formation of finer grain structure after 1 pass of FSP. The finer grain structure occurred in the stir zone where a sufficient amount of nanoparticles with a relatively proper distribution existed. However, the initial stored strain value had a contrary influence in the regions with low volume fraction of nanoparticles. In fact, more stored strain in the base metal provided more driving force for both nucleation and grain growth of newly recrystallized grains at the stir zone. Pinning effect of well-distributed nanoparticles could effectively retard grain growth leading to the formation of very fine grain structure. Also it was observed that the initial stored strain values did not have impressive rule in the microstructural evolutions at the stir zone during the second and third FSP passes signifying that all of the stored energy in the base metal would be released after 1 pass of FSP. The results obtained with microhardness measurement at the stir zone were fairly in agreement with those achieved by the microstructure assessments.

  15. Effect of Machining Parameters on Surface Integrity in Machining Nimonic C-263 Super Alloy Using Whisker-Reinforced Ceramic Insert

    NASA Astrophysics Data System (ADS)

    Ezilarasan, C.; Senthil kumar, V. S.; Velayudham, A.

    2013-06-01

    Whisker-reinforced ceramic inserts were used to conduct turning trials on nimonic C-263 super alloy to study the effect of different combinations of cutting parameters on surface integrity (roughness, microhardness, and residual stress) by employing energy dispersive spectroscopy, scanning electron microscopy, x-ray diffraction, and Vicker's microhardness test. Abrasion, adhesion and diffusion were found to be the main tool wear mechanisms in turning nimonic C-263 alloy. Based on characterization of surface roughness, a combination of 190 m/min cutting speed and 0.102 mm/rev feed rate was found to be the critical condition for turning nimonic C-263 alloy. Microhardness varied between 550 and 690 HV at the feed rates of 0.102-0.143 mm/rev for a cutting speed of 250 m/min after 9 min of turning. A tensile residual stress of 725-850 MPa on the machined surface was recorded at the preceding combination of cutting parameters. Cutting speed and cutting time had a dominant effect on the magnitude of the residual stress. No evidence of thermal relaxation and reduction in the degree of work hardening was noted during machining at high cutting speed.

  16. Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder

    NASA Astrophysics Data System (ADS)

    Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.

    2013-07-01

    UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable γ-UMo phases partly decomposed into two different γ-UMo phases, U2Mo and α'-U in ground powder or α″-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the γ-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ⩽1 μm - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some μm diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the γ-UMo with respect to α-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the

  17. Carbon nanotube reinforced aluminum based nanocomposite fabricated by thermal spray forming

    NASA Astrophysics Data System (ADS)

    Laha, Tapas

    The present research concentrates on the fabrication of bulk aluminum matrix nanocomposite structures with carbon nanotube reinforcement. The objective of the work was to fabricate and characterize multi-walled carbon nanotube (MWCNT) reinforced hypereutectic Al-Si (23 wt% Si, 2 wt% Ni, 1 wt% Cu, rest Al) nanocomposite bulk structure with nanocrystalline matrix through thermal spray forming techniques viz. plasma spray forming (PSF) and high velocity oxy-fuel (HVOF) spray forming. This is the first research study, which has shown that thermal spray forming can be successfully used to synthesize carbon nanotube reinforced nanocomposites. Microstructural characterization based on quantitative microscopy, scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and X ray photoelectron spectroscopy (XPS) confirms (i) retention and macro/sub-macro level homogenous distribution of multiwalled carbon nanotubes in the Al-Si matrix and (ii) evolution of nanostructured grains in the matrix. Formation of ultrathin beta-SiC layer on MWCNT surface, due to chemical reaction of Si atoms diffusing from Al-Si alloy and C atoms from the outer walls of MWCNTs has been confirmed theoretically and experimentally. The presence of SiC layer at the interface improves the wettability and the interfacial adhesion between the MWCNT reinforcement and the Al-Si matrix. Sintering of the as-sprayed nanocomposites was carried out in an inert environment for further densification. As-sprayed PSF nanocomposite showed lower microhardness compared to HVOF, due to the higher porosity content and lower residual stress. The hardness of the nanocomposites increased with sintering time due to effective pore removal. Uniaxial tensile test on CNT-bulk nanocomposite was carried out, which is the first ever study of such nature. The tensile test results showed inconsistency in the data attributed to inhomogeneous

  18. Electromigration in multilayer metallization: Drift-controlled degradation and the electromigration threshold of Al-Si- Cu/TiNxOy/TiSi2 contacts

    NASA Astrophysics Data System (ADS)

    Oates, A. S.

    1991-11-01

    Metallizations that incorporate a conductive layer beneath an Al alloy (multilayers) are necessary for the improvement in electromigration performance required by the continued feature size reduction and increased integration of microelectronic devices. Degradation of contact structures that utilize multilayer metallization will result from electromigration-induced voiding of the Al layer. A detailed understanding of the mechanisms of voiding is required for the accurate prediction of contact reliability. We have examined electromigration voiding in Al-Si-Cu/TiNxOy/TiSi2 multilayer contacts. Accelerated testing reveals that a TiNxOy/TiSi2 layer formed by rapid thermal anneal of Ti is an effective Si diffusion barrier at operating temperatures (<125 °C) and eliminates electromigration-induced leakage failures. Contact degradation occurs by increased resistance due to voiding of the Al-Si-Cu layer. Voiding involves drift-controlled edge displacement where the Al-Si-Cu layer migrates out of positively biased contacts, leaving the TiNxOy/TiSi2 layer intact. For 1-μm-diam contacts, the drift velocity has a significant lattice diffusion component and failure times are expected to far exceed operation lifetimes of devices. Additionally, evidence is presented for an electromigation threshold that eliminates voiding degradation for contacts connected by stripes.

  19. Analysis of the interaction products in U(Mo,X)/Al and U(Mo,X)/Al(Si) diffusion couples, with X = Cr, Ti, Zr

    NASA Astrophysics Data System (ADS)

    Allenou, J.; Palancher, H.; Iltis, X.; Tougait, O.; El Bekkachi, H.; Bonnin, A.; Tucoulou, R.

    2014-03-01

    In the framework of the development of a low 235U enriched nuclear fuel for material testing reactors, γ-U(Mo)/Al based materials are considered as the most interesting prospect. In the process to optimize their composition, addition to both γ-U(Mo) and Al have been proposed. In this paper, the crystallographic composition of Interaction Layers (ILs) in γ-U(Mo,X)/Al and γ-U(Mo,X)/AlSi7 diffusion couples, with X = Cr, Ti, Zr, heat-treated at 600 °C for 2 h, were studied by micro-X-ray diffraction (μ-XRD). When compared to the U(Mo)/Al and U(Mo)/Al(Si) reference systems, all investigated systems involving either Al or Al(Si) as counterparts show interaction products composed of similar phases and related sequences of phase formation. Only relative thicknesses of sub-layers and relative fractions of intermediate phases are correlated with the nature of the X element in the γ-U(Mo,X) alloy.

  20. One-dimensional shape memory alloy models for use with reinforced composite structures

    NASA Astrophysics Data System (ADS)

    Zak, A. J.; Cartmell, M. P.; Ostachowicz, W. M.; Wiercigroch, M.

    2003-06-01

    In this paper three models of the shape memory alloy behaviour have been presented and re-investigated. The models are attributed to Tanaka, Liang and Rogers, and Brinson, and have been used extensively in the literature for studying the static or dynamic performance of different composite material structures with embedded shape memory alloy components. The major differences and similarities between these models have been emphasised and examined in the paper. A simple experimental rig was designed and manufactured to gain additional insight into the main mechanics governing the shape memory alloy (SMA) mechanical properties. Data obtained from the experimental measurements on Ni-Ti wires have been used in the numerical simulation for validation purposes. It has been found that the three models all agree well in their predictions of the superelastic behaviour at higher temperatures, above the austenite finish temperature when shape memory alloys stay in the fully austenitic phase. However, at low temperatures, when the alloys stay in the fully martensitic phase, some difficulties may be encountered. The model developed by Brinson introduces two new state variables and therefore two different mechanisms for the instigation of stress-induced and temperature-induced martensite. This enables more accurate predictions of the superelastic behaviour. In general, it can be recommended that for investigations of the shape memory and superelastic behaviour of shape memory alloy components the Brinson model, or refinements based on the Brinson model, should be applied.

  1. Aging effects of diamond reinforced aluminium alloys submitted to deep space real conditions. Structural, chemical and electrical degradation

    NASA Astrophysics Data System (ADS)

    Korneli, Grigorov; Bouzekova-Penkova, Anna; Datcheva, Maria; Avdeev, George; Grushin, Valerii; Klimov, Stanislav

    2016-07-01

    An aluminium alloy (Al-Cu-Zn-Mg) reinforced with ultra-dispersed diamond powder and tungsten (W), has been prepared in form of 7 cm bars and 4 mm diameter. One part of them stayed 2 years on satellite exposed to outer space, where the Sun activity and the background radiation were monitored. After satellite return both batches has been studied. Structural test, mainly micro-hardness together with detailed X-rays analyses was performed. The satellite makes a tour around the Earth each two hours, the temperature difference being circa 300oC. The micro-hardness being measured with Agilent G200 nano-indentor shows a significant drop of 25%. The XRD patterns are consistent with the previous results, states defects incorporation, and crystalline cells deterioration.

  2. Crack bridging by uncracked ligaments during fatigue-crack growth in SiC-reinforced aluminum-alloy composites

    NASA Astrophysics Data System (ADS)

    Shang, Jian Ku; Ritchie, R. O.

    1989-05-01

    Micro-mechanisms of crack-tip shielding associated with the growth of fatigue cracks in metalmatrix composites are examined with specific emphasis on the role of crack bridging by uncracked ligaments. Simple analytical models are developed for such bridging induced by both overlapping cracks and by coplanar ligaments in the wake of the crack tip; the models are based on respective notions of a critical tensile strain or critical crack-opening displacement in the ligament. The predicted degree of shielding derived from these mechanisms is not large, but is found to be consistent with experimental observations in high-strength P/M aluminum alloys reinforced with 15 to 20 vol pct of SiC particulate.

  3. Study on preparation and properties of molybdenum alloys reinforced by nano-sized ZrO2 particles

    NASA Astrophysics Data System (ADS)

    Cui, Chaopeng; Gao, Yimin; Wei, Shizhong; Zhang, Guoshang; Zhou, Yucheng; Zhu, Xiangwei; Guo, Songliang

    2016-03-01

    The nano-sized ZrO2-reinforced Mo alloy was prepared by a hydrothermal method and a subsequent powder metallurgy process. During the hydrothermal process, the nano-sized ZrO2 particles were added into the Mo powder via the hydrothermal synthesis. The grain size of Mo powder decreases obviously with the addition of ZrO2 particles, and the fine-grain sintered structure is obtained correspondingly due to hereditation. In addition to a few of nano-sized ZrO2 particles in grain boundaries or sub-boundaries, most are dispersed in grains. The tensile strength and yield strength have been increased by 32.33 and 53.76 %.

  4. Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

    2015-12-01

    In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

  5. Compound characterization of laser brazed SiC-steel joints using tungsten reinforced SnAgTi-alloys

    NASA Astrophysics Data System (ADS)

    Südmeyer, I.; Rohde, M.; Fürst, T.

    2010-02-01

    With the help of a CO2-laser (λ = 10.64 μm) Silicon carbide (Trade name: Ekasic-F, Comp: ESK Ceramics) has been brazed to commercial steel (C45E, Matnr. 1.1191) using SnAgTi-filler alloys. The braze pellets were dry pressed based on commercially available powders and polished to a thickness of 300 μm. The SnAgTi-fractions were varied with the objective of improving the compound strength. Furthermore, tungsten reinforced SnAgTi-fillers were examined with regard to the shear strength of the ceramic/steel joints. Polished microsections of SnAgTi-pellets were investigated before brazing in order to evaluate the particle distribution and to detect potential porosities using optical microscopy. The brazing temperature and the influence of the reinforcing particles on the active braze filler were determined by measurements with a differential scanning calorimeter (DSC). After brazing. the ceramic-steel joints were characterized by scanning electron micrographs and EDX-analysis. Finally the mechanical strength of the braze-joints was determined by shear tests.

  6. Interfacial Reactions at Elevated Temperatures in New Low-Cost AL/SiC Metal Matrix Composite

    SciTech Connect

    Grant, Glenn J.; Mccready, David E.; Herling, Darrell R.; Smith, M. T.

    2001-08-21

    The mechanical properties of Metal Matrix Composites (MMCs) are strongly affected by the quality of the bond between the matrix and the reinforcing particle. In aluminum MMCs reinforced with SiC particles, the particle/matrix interface can be degraded at high temperature by the formation of aluminum carbide and aluminum/magnesium oxides. The temperature that these reactions occur at is an important process limit during melting, casting, and eventual product recycling. Recently, lower cost Al/SiC MMCs have become available that utilize less well-graded particulate and a unique rapid-mixing technique. However, as a result of the relaxed control on the particle size fraction, a significantly larger percentage of the particulate is found in the finer size ranges. This leads to an increase in the interface area between the SiC particles and the aluminum melt, and raises the possibility that detrimental aluminum carbide and oxide reactions could occur at lower temperatures, or lower time-at-temperature, than in current commercial products. In this study, we quantify by conventional, and in-situ liquid metal XRD, the time-temperature relationship for interfacial carbide/oxide formation, and compare commercially available MMC materials to MMC material produced from less well-graded SiC particulate.

  7. After-Corrosion Suppression Using Low-Temperature Al-Si-Cu Etching

    NASA Astrophysics Data System (ADS)

    Aoki, Hidemitsu; Ikawa, Eiji; Kikkawa, Takamaro; Teraoka, Yuden; Nishiyama, Iwao

    1991-07-01

    The authors investigated the low-temperature etching effect on Al-Si-Cu after-corrosion. The after-corrosion extent was evaluated from the corrosion point density generated on the rinsed Al-Si-Cu stripes after dry etching. As the etching temperature was reduced, after-corrosion was suppressed. In order to study the low-temperature etching effect, the authors analyzed the Cl compounds remaining on the Al-Si-Cu film by thermal desorption spectroscopy (TDS). TDS revealed that the Cl concentration remaining on the Al-Si-Cu film etched at -60°C after rinsing in water was smaller than that remaining on the film etched at 30°C. Consequently, suppression of after-corrosion by low temperature etching could be attributed to the smaller number of Al-Cu bonds remaining in the Al-Si-Cu etch surface after removal of the AlClx layer by rinsing with water. This fact is due to the reduction of chemical reaction and diffusion rate by lowering the substrate temperature.

  8. The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles

    SciTech Connect

    Fei Tang

    2004-12-19

    Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two important aspects, including improving the properties of MMCs and finding more economical techniques to produce MMCs. Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. Microstructures and tensile properties of AYAl-Cu-Fe composites were characterized. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of

  9. AlSiTiN and AlSiCrN multilayer coatings: Effects of structure and surface composition on tribological behavior under dry and lubricated conditions

    NASA Astrophysics Data System (ADS)

    Faga, Maria Giulia; Gautier, Giovanna; Cartasegna, Federico; Priarone, Paolo C.; Settineri, Luca

    2016-03-01

    Nanocomposite coatings have been widely studied over the last years because of their high potential in several applications. The increased interest for these coatings prompted the authors to study the tribological properties of two nanocomposites under dry and lubricated conditions (applying typical MQL media), in order to assess the influence of the surface and bulk properties on friction evolution. To this purpose, multilayer and nanocomposite AlSiTiN and AlSiCrN coatings were deposited onto tungsten carbide-cobalt (WC-Co) samples. Uncoated WC-Co materials were used as reference. Coatings were analyzed in terms of hardness and adhesion. The structure of the samples was assessed by X-ray diffraction (XRD), while the surface composition was studied by XPS analysis. Friction tests were carried out under both dry and lubricated conditions using an inox ball as counterpart. Both coatings showed high hardness and good adhesion to the substrate. As far as the friction properties are concerned, in dry conditions the surface properties affect the sliding contact at the early beginning, while bulk structure and tribolayer formation determine the main behavior. Only AlSiTiN coating shows a low and stable coefficient of friction (COF) under dry condition, while the use of MQL media results in a rapid stabilization of the COF for all the materials.

  10. Fabrication and Wear Behavior of Nanostructured Plasma-Sprayed 6061Al-SiCp Composite Coating

    NASA Astrophysics Data System (ADS)

    Tailor, Satish; Mohanty, R. M.; Sharma, V. K.; Soni, P. R.

    2014-10-01

    6061Al powder with 15 wt.% SiC particulate (SiCp) reinforcement was mechanically alloyed (MA) in a high-energy attrition mill. The MA powder was then plasma sprayed onto weathering steel (Cor-Ten A242) substrate using an atmospheric plasma spray process. Results of particle size analysis and scanning electron microscopy show that the addition of SiC particles as the reinforcement influences on the matrix grain size and morphology. XRD studies revealed embedment of SiCp in the MA-processed composite powder, and nanocrystals in the MA powder and the coating. Microstructural studies showed a uniform distribution of reinforced SiC particles in the coating. The porosity level in the coating was as low as 2% while the coating hardness was increased to 232VHN. The adhesion strength of the coatings was high and this was attributed to higher degree of diffusion at the interface. The wear rate in the coatings was evaluated using a pin-on-disk type tribometer and found to decrease by 50% compared to the 6061Al matrix coating. The wear mechanism in the coating was delamination and oxidative type.

  11. Microstructural dependence of annealing temperature in magnetron-sputtered Al-Si-Cu films

    NASA Astrophysics Data System (ADS)

    Liang, Ming-Kaan; Ling, Yong-Chien

    1993-09-01

    The effect of sputtering temperature, sputtering bias, and annealing temperature upon the sheet resistance, WO3 formation at the Al-Si-Cu/Ti-W interface, and diffraction intensity of the Al2Cu precipitates of magnetron-sputtered Al-Si-Cu films were investigated. Statistical methods and microcharacterization techniques were applied to study these effects. Statistical analysis verifies the effect of annealing temperature on the measured sheet resistance. Annealing temperature alone is the dominant factor upon the WO3 formation at the Al-Si-Cu/Ti-W interface and the Al2Cu (211) plane diffraction intensity. Annealed samples are of higher sheet resistance. Increase in sheet resistance is ascribed to the formation of interfacial WO3. Reduced electromigration is related to the formation of Al2Cu precipitates. Secondary ion mass spectrometry (SIMS) analysis of the as-deposited sample depicts the presence of an excess amount of oxygen atoms at the surface and the Al-Si-Cu/Ti-W and Ti-W/Ti interfaces. Rutherford backscattering spectrometry and SIMS analyses reveal the outdiffusion of W from the Ti-W layer toward the Al-Si-Cu layer, the presence of Si nodules at the Al-Si-Cu/Ti-W interface, and the formation of Ti silicides at the Ti/Si interface. These phenomena are confirmed by transmission electron microscopy, energy dispersive x-ray analysis, and scanning electron microscopy analyses. It is concluded that interfacial oxygen, which reacts with W to form WO3 upon annealing, warrants further reduction to yield films of better sheet resistance.

  12. Synthesis and characterization of nanoscale Al-Si-O gradient membranes

    SciTech Connect

    Trouillet, V.; Troesse, H.; Bruns, M.; Nold, E.; White, R. G.

    2007-07-15

    Novel ultrathin gas-permeable Al-Si-oxide membranes have been developed by means of ion induced chemical vapor deposition in order to improve the gas analytical performance of an electronic nose. Dependent on the used precursor tailored Al/Si concentration ratios and even concentration gradients are attainable. The diversity in chemical composition and thickness across the gas sensor microarray has been proven by the combination of ellipsometry for the freshly prepared membrane and line scans derived from Auger electron spectroscopy and angle resolved x-ray photoelectron spectroscopy, respectively, for the baked membrane.

  13. On Porosity Formation in Metal Matrix Composites Made with Dual-Scale Fiber Reinforcements Using Pressure Infiltration Process

    NASA Astrophysics Data System (ADS)

    Etemadi, Reihaneh; Pillai, Krishna M.; Rohatgi, Pradeep K.; Hamidi, Sajad Ahmad

    2015-05-01

    This is the first such study on porosity formation phenomena observed in dual-scale fiber preforms during the synthesis of metal matrix composites (MMCs) using the gas pressure infiltration process. In this paper, different mechanisms of porosity formation during pressure infiltration of Al-Si alloys into Nextel™ 3D-woven ceramic fabric reinforcements (a dual-porosity or dual-scale porous medium) are studied. The effect of processing conditions on porosity content of the ceramic fabric infiltrated by the alloys through the gas PIP (PIP stands for "Pressure Infiltration Process" in which liquid metal is injected under pressure into a mold packed with reinforcing fibers.) is investigated. Relative density (RD), defined as the ratio of the actual MMC density and the density obtained at ideal 100 pct saturation of the preform, was used to quantify the overall porosity. Increasing the infiltration temperature led to an increase in RD due to reduced viscosity of liquid metal and enhanced wettability leading to improved feedability of the liquid metal. Similarly, increasing the infiltration pressure led to enhanced penetration of fiber tows and resulted in higher RD and reduced porosity. For the first time, the modified Capillary number ( Ca*), which is found to predict formation of porosity in polymer matrix composites quite well, is employed to study porosity in MMCs made using PIP. It is observed that in the high Ca* regime which is common in PIP, the overall porosity shows a strong downward trend with increasing Ca*. In addition, the effect of matrix shrinkage on porosity content of the samples is studied through using a zero-shrinkage Al-Si alloy as the matrix; usage of this alloy as the matrix led to a reduction in porosity content.

  14. The effect of Si in Al-alloy on electromigration performance in Al filled vias

    NASA Astrophysics Data System (ADS)

    Kageyama, Makiko; Hashimoto, Keiichi; Onoda, Hiroshi

    1998-01-01

    Electromigration performance of vias filled with Al-Si-Cu alloys on Ti glue layers was investigated in comparison with W-stud vias. In Al-Si-Cu filled vias, voids were formed at only a few locations in the test structure, while voids were formed at every via in W-stud via chains. It is supposed that Al moves through the Al-Si-Cu via during electromigration in spite of the existence of a glue layer at the via bottom. This phenomenon was observed only in the vias filled with Al-Si-Cu alloy. Al movement was prohibited in Al-Cu filled vias. In Al-Si-Cu filled vias, an Al-Ti-Si alloy was formed at the via bottom while Al3Ti was formed at Al-Cu filled vias. Al is speculated to move through this Al-Ti-Si alloy during electromigration.

  15. High strain rate superplasticity of Si{sub 3}N{sub 4} whisker reinforced 7075 alloy matrix composite fabricated by squeeze casting

    SciTech Connect

    Lim, S.W.; Nishida, Yoshinori

    1995-06-01

    The {alpha}-Si{sub 3}N{sub 4} whisker reinforced 7075 aluminum alloy composite which exhibits superplasticity was produced by squeeze casting, followed by hot extrusion to pursue industrial advantages, and following results were obtained: (1) the production of {alpha}-Si3N4 whisker reinforced 7075 aluminum alloy composite which exhibits superplasticity was succeeded by squeeze casting; (2) the composite exhibited a total elongation of 260% at strain rates 0.18 s{sup {minus}1} at 773 K; (3) the superplasticity occurred in the wide range of strain rate from 0.1 to 1 s{sup {minus}1}; (4) the superplasticity occurred in the industrially useful whisker volume fraction range of 20%--30%.

  16. Aging kinetics of a silicon carbide reinforced Al-Zn-Mg-Cu alloy

    SciTech Connect

    Davies, C.H.J.; Raghunathan, N.; Sheppard, T.

    1994-01-01

    The aging kinetics of a composite of an Al-Zn-Mg-Cu powder (CW67) combined with a varied volume fraction of a particulate silicon carbide were investigated by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). DSC revealed that the maximum rate of precipitation of the metastable {eta}{prime} phase was substantially lower for CW67/SiC/20p than for the unreinforced alloy or CW67/SiC/10p. TEM of isothermally aged material revealed differences between the unreinforced alloy and composites in respect of precipitate size and morphology. The authors conclude that SiC additions, by dint of additional dislocations generated during quenching, can affect the aging of CW67 either by accelerating the nucleation of precipitates or by accelerating precipitate growth. The aging rate of CW67/SiC/20p was increased by accelerating both the nucleation of precipitates and growth, whereas the aging in CW67/SiC10p was enhanced by accelerating precipitate growth only.

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

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The addition of ceramic particles to aluminum based alloys can substantially improve mechanical properties, especially Young's modulus and room and elevated temperature strengths. However, these improvements typically occur at the expense of tensile ductility. The mechanical properties are evaluated to a metal matrix composite (MMC) consisting of an ultrahigh strength aluminum lithium alloy, Weldalite (tm) 049, reinforced with TiB2 particles produced by an in situ precipitation technique called the XD (tm) process. The results are compared to the behavior of a nonreinforced Weldalite 049 variant. It is shown that both 049 and 049-TiB2 show very attractive warm temperature properties e.g., 625 MPa yield strength at 150 C after 100 h at temperature. Weldalite 049 reinforced with a nominal 4 v pct. TiB2 shows an approx. 8 pct. increase in modulus and a good combination of strength (529 MPa UTS) and ductility (6.5 pct.) in the T3 temper. And the high ductility of Weldalite 049 in the naturally aged and underaged tempers makes the alloy a good, high strength matrix for ceramic reinforcement.

  18. Biodegradable poly-lactic acid based-composite reinforced unidirectionally with high-strength magnesium alloy wires.

    PubMed

    Li, X; Chu, C L; Liu, L; Liu, X K; Bai, J; Guo, C; Xue, F; Lin, P H; Chu, Paul K

    2015-05-01

    Biodegradable poly-lactic acid (PLA)--based composites reinforced unidirectionally with high-strength magnesium alloy wires (MAWs) are fabricated by a heat-compressing process and the mechanical properties and degradation behavior are studied experimentally and theoretically. The composites possess improved strengthening and toughening properties. The bending strength and impact strength of the composites with 40 vol% MAWs are 190 MPa and 150 kJ/m(2), respectively, although PLA has a low viscosity and an average molecular weight of 60,000 g/mol. The mechanical properties of the composites can be further improved by internal structure modification and interface strengthening and a numerical model incorporating the equivalent section method (ESM) is proposed for the bending strength. Micro arc oxidization (MAO) of the MAWs is an effective interfacial strengthening method. The composites exhibit high strength retention during degradation and the PLA in the composite shows a smaller degradation rate than pure PLA. The novel biodegradable composites have large potential in bone fracture fixation under load-bearing conditions. PMID:25725562

  19. Development of a self-stressing NiTiNb shape memory alloy (SMA)/fiber reinforced polymer (FRP) patch

    NASA Astrophysics Data System (ADS)

    El-Tahan, M.; Dawood, M.; Song, G.

    2015-06-01

    The objective of this research is to develop a self-stressing patch using a combination of shape memory alloys (SMAs) and fiber reinforced polymer (FRP) composites. Prestressed carbon FRP patches are emerging as a promising alternative to traditional methods to repair cracked steel structures and civil infrastructure. However, prestressing these patches typically requires heavy and complex fixtures, which is impractical in many applications. This paper presents a new approach in which the prestressing force is applied by restraining the shape memory effect of NiTiNb SMA wires. The wires are subsequently embedded in an FRP overlay patch. This method overcomes the practical challenges associated with conventional prestressing. This paper presents the conceptual development of the self-stressing patch with the support of experimental observations. The bond between the SMA wires and the FRP is evaluated using pull-out tests. The paper concludes with an experimental study that evaluates the patch response during activation subsequent monotonic tensile loading. The results demonstrate that the self-stressing patch with NiTiNb SMA is capable of generating a significant prestressing force with minimal tool and labor requirements.

  20. Wear Resistance of Aluminum Matrix Composites Reinforced with Al2O3 Particles After Multiple Remelting

    NASA Astrophysics Data System (ADS)

    Klasik, Adam; Pietrzak, Krystyna; Makowska, Katarzyna; Sobczak, Jerzy; Rudnik, Dariusz; Wojciechowski, Andrzej

    2016-01-01

    Based on previous results, the commercial composites of A359 (AlSi9Mg) alloy reinforced with 22 vol.% Al2O3 particles were submitted to multiple remelting by means of gravity casting and squeeze-casting procedures. The studies were focused on tribological tests, x-ray phase analyses, and microstructural examinations. More promising results were obtained for squeeze-casting method mainly because of the reduction of the negative microstructural effects such as shrinkage porosity or other microstructural defects and discontinuities. The results showed that direct remelting may be treated as economically well-founded and alternative way compared to other recycling processes. It was underlined that the multiple remelting method must be analyzed for any material separately.

  1. Effects of porous carbon on sintered Al-Si-Mg matrix composites

    NASA Astrophysics Data System (ADS)

    Ejiofor, J. U.; Reddy, R. G.

    1997-12-01

    The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO2 gas flow. Activated char particles at 0.02 V f were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 °C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 °C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6 %, respectively; with increasing surface area of the reinforcement from 123 to 821 m2g-1. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13 % (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16 % (11.7 × 10-6 to 9.8 × 10-6 °C-1), and remained unaffected at more than 35 % burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds.

  2. Effects of porous carbon on sintered Al-Si-Mg matrix composites

    SciTech Connect

    Ejiofor, J.U.; Reddy, R.G.

    1997-12-01

    The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO{sub 2} gas flow. Activated char particles at 0.02 V{sub f} were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6%, respectively; with increasing surface area of the reinforcement from 123 to 821 m{sup 2} g{sup {minus}1}. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13% (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16% (11.7 {times} 10{sup {minus}6} to 9.8 {times} 10{sup {minus}6} C{sup {minus}1}), and remained unaffected at more than 35% burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds.

  3. Research on an AlSiNx bi-material thermal-mechanical uncooled infrared FPA pixel

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Zhang, Da-cheng

    2011-08-01

    AlSiNx bi-material thermal strain structure is used in uncooled optic readout infrared focal plane array (UOR IR FPA) pixel based on Micro-Electro-Mechanical Systems (MEMS) technology. In this paper, the problems that the AlSiNxstructure prevents FPA pixel scaling down and fill factor improving, and the Au reflection layer of the pixel leads to larger readout light energy loss are analyzed. The feasibility of AlSiNx instead of AlSiNx in the UOR IR FPA fabrication is researched in detail. The theoretical analyzing and simulation results demonstrate that, with optimized thicknesses and their matching designing of SiNx and Al, the thermal-mechanical response of AlSiNx bi-material structure is improved to 1.8 times and the intensity of optic readout signal is improved to about 2 times compared with AuSiNAlSiNx one.

  4. Atomic structure and electronic properties of the two-dimensional (Au ,Al )/Si (111 )2 ×2 compound

    NASA Astrophysics Data System (ADS)

    Gruznev, D. V.; Bondarenko, L. V.; Matetskiy, A. V.; Tupchaya, A. Y.; Chukurov, E. N.; Hsing, C. R.; Wei, C. M.; Eremeev, S. V.; Zotov, A. V.; Saranin, A. A.

    2015-12-01

    A combination of scanning tunneling microscopy, angle-resolved photoelectron spectroscopy, ab initio random structure searching, and density functional theory electronic structure calculations was applied to elucidate the atomic arrangement and electron band structure of the (Au ,Al )/Si (111 )2 ×2 two-dimensional compound formed upon Al deposition onto the mixed 5 ×2 /√{3 }×√{3 } Au/Si(111) surface. It was found that the most stable 2 ×2 -(Au, Al) compound incorporates four Au atoms, three Al atoms, and two Si atoms per 2 ×2 unit cell. Its atomic arrangement can be visualized as an array of meandering Au atomic chains with two-thirds of the Al atoms incorporated into the chains and one-third of the Al atoms interconnecting the chains. The compound is metallic and its electronic properties can be controlled by appropriate Al dosing since energetic location of the bands varies by ˜0.5 eV during increasing of Al contents. The 2 ×2 -(Au, Al) structure appears to be lacking the C3 v symmetry typical for the hexagonal lattices. The consequence of the peculiar atomic structure of the two-dimensional alloy is spin splitting of the metallic states, which should lead to anisotropy of the current-induced in-plane spin polarization.

  5. Non-linear resistance behavior in the early stages and after electromigration in Al-Si lines

    NASA Astrophysics Data System (ADS)

    Scorzoni, A.; De Munari, I.; Stulens, H.; D'Haeger, V.

    1996-07-01

    A common result obtained in electromigration experiments carried out on Al-Si lines using different high resolution resistometric methods, is a monotonous non-linear resistance increase at the very beginning of the high current electromigration test, and a decrease after the high stressing current is switched off. These effects have often been attributed to the attainment of a steady state of vacancy concentration during and after electromigration. This paper shows how even small abrupt temperature steps, always present at the beginning and after electromigration tests, are the triggering events for different, often reversible, physical phenomena contributing to non-linear resistance changes. Precipitation-dissolution of alloyed elements appears to be the most significant one. Abrupt temperature changes also induce a change of the hydrostatic stress of passivated lines. The relaxation of the hydrostatic stress could be coupled with a void volume change, and the total resistance is a function of both the hydrostatic stress (through resistivity) and of void volume. However, we demonstrate that in our experiments the effect of hydrostatic stress relaxation on resistance variations is negligible with respect to the action of precipitation-dissolution. These non-linear, thermally induced effects, however, do not exclude possible simultaneous resistance changes due to the accumulation/relaxation of the electromigration damage. Experimental results are collected by means of different, complementary techniques.

  6. Quasicrystalline particulate reinforced aluminum composite

    SciTech Connect

    Anderson, I.E.; Biner, S.B.; Sordelet, D.J.; Unal, O.

    1997-07-01

    Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared.

  7. Friction and Wear of Monolithic and Fiber Reinforced Silicon-Ceramics Sliding Against IN-718 Alloy at 25 to 800 C in Atmospheric Air at Ambient Pressure

    NASA Technical Reports Server (NTRS)

    Deadmore, Daniel L.; Sliney, Harold E.

    1988-01-01

    The friction and wear of monolithic and fiber reinforced Si-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C was measured. The monolithic materials tested were silicon carbide (SiC), fused silica (SiO2), syalon, silicon nitride (Si3N4) with W and Mg additives, and Si3N4 with Y2O3 additive. At 25 C fused silica had the lowest friction while Si3N4 (W,Mg type) had the lowest wear. At 800 C syalon had the lowest friction while Si3N4 (W,Mg type) and syalon had the lowest wear. The SiC/IN-718 couple had the lowest total wear at 25 C. At 800 C the fused silica/IN-718 couple exhibited the least total wear. SiC fiber reinforced reaction bonded silicon nitride (RBSN) composite material with a porosity of 32 percent and a fiber content of 23 vol percent had a lower coefficient of friction and wear when sliding parallel to the fiber direction than in the perpendicular at 25 C. The coefficient of friction for the carbon fiber reinforced borosilicate composite was 0.18 at 25 C. This is the lowest of all the couples tested. Wear of this material was about two decades smaller than that of the monolithic fused silica. This illustrates the large improvement in tribological properties which can be achieved in ceramic materials by fiber reinforcement. At higher temperatures the oxidation products formed on the IN-718 alloy are transferred to the ceramic by sliding action and forms a thin, solid lubricant layer which decreases friction and wear for both the monolithic and fiber reinforced composites.

  8. Effect of ZrO2 Nanoparticles on the Microstructure of Al-Si-Cu Filler for Low-Temperature Al Brazing Applications

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Roh, Myung-Hwan; Jung, Do-Hyun; Jung, Jae-Pil

    2016-01-01

    In this study, the effect of ZrO2 nanoparticles on Al-12Si-20Cu alloy has been studied as a filler metal for aluminum brazing. The microstructural and thermal characterizations are performed using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential thermal analysis (DTA). The intermetallic compound (IMC) phases are identified by the energy-dispersive spectroscopy analysis coupled with the SEM. The filler spreading test is performed according to JIS-Z-3197 standard. XRD and SEM analyses confirm the presence of Si particles, the CuAl2 ( θ) intermetallic, and the eutectic structures of Al-Si, Al-Cu, and Al-Si-Cu in the Al matrix in the monolithic and composite samples. It is observed that when the ZrO2 is added in the alloy, the CuAl2 IMCs and Si particles are found to be dispersed uniformly in the Al matrix up to 0.05 wt pct ZrO2. DTA results show that the liquidus temperature of Al-12Si-20Cu filler metal is dropped from ~806.78 K to 804.6 K (533.78 °C to 531.6 °C) with a lowering of 2 K (2 °C) in liquidus temperature, when the amount of ZrO2 is increased up to 0.05 wt pct. It is also shown that the presence of ZrO2 nanoparticles in the filler metal has no deleterious effect on wettability up to 0.05 wt pct of ZrO2. The ultimate tensile strength and elongation percentage are also found to improve with the addition of ZrO2 nanoparticles in the Al-12Si-20Cu alloy.

  9. Local crystallography and stress voiding in Al-Si-Cu versus copper interconnects

    NASA Astrophysics Data System (ADS)

    Keller, R. R.; Kalnas, C. E.; Phelps, J. M.

    1999-07-01

    We compare the local crystallographic orientations associated with stress voids in Al-1Si-0.5Cu (wt %) with those in pure copper interconnects. Orientations were sorted by whether grains were immediately adjacent to voids. Grains adjacent to voids in Al-Si-Cu showed a <111> fiber texture that was slightly stronger than those in intact regions. This is in contrast to copper, which showed weaker local <111> texture around voids. We postulate the difference to be due to the relative effectiveness of the diffusion paths available in the lines. For Al-Si-Cu, the presence of defects associated with precipitates may allow more rapid diffusion than grain boundaries. Voiding in copper, which is free from such defects, depends more on grain boundary structure.

  10. On the Precipitation Hardening of Selective Laser Melted AlSi10Mg

    NASA Astrophysics Data System (ADS)

    Aboulkhair, Nesma T.; Tuck, Chris; Ashcroft, Ian; Maskery, Ian; Everitt, Nicola M.

    2015-08-01

    Precipitation hardening of selective laser melted AlSi10Mg was investigated in terms of solution heat treatment and aging duration. The influence on the microstructure and hardness was established, as was the effect on the size and density of Si particles. Although the hardness changes according to the treatment duration, the maximum hardening effect falls short of the hardness of the as-built parts with their characteristic fine microstructure. This is due to the difference in strengthening mechanisms.

  11. Oxidation resistance of quintuple Ti-Al-Si-C-N coatings and associated mechanism

    SciTech Connect

    Wu Guizhi; Ma Shengli; Xu Kewei; Ji, Vincent; Chu, Paul K.

    2012-07-15

    The oxidation behavior of Ti-Al-Si-C-N hard coatings with different Al contents deposited on high-speed steel and Si substrates by hybrid arc-enhanced magnetron sputtering is investigated in the temperature range of 500 Degree-Sign C-1000 Degree-Sign C. The coating hardness is maintained at around 35 GPa, and the parabolic oxidation rate constant K{sub p} at 1000 Degree-Sign C decreases to 3.36 Multiplication-Sign 10{sup -10} kg{sup 2} m{sup -4} s{sup -1} when the Al concentration is increased to 30 at. %, indicating that Ti-Al-Si-C-N coatings with larger Al concentrations have better oxidation resistance. X-ray diffraction, cross-sectional scanning electron microscopy, and x-ray photoelectron spectroscopy reveal a protective surface layer consisting of Al{sub 2}O{sub 3}, TiO{sub 2}, and SiO{sub 2} that retards inward oxygen diffusion. A mechanism is proposed to elucidate the oxide formation. As a consequence of the good oxidation resistance, the Ti-Al-Si-C-N coatings have a large potential in high-speed dry cutting as well as other high temperature applications.

  12. (Ti,Al,Si,C)N nanocomposite coatings synthesized by plasma-enhanced magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Yanfeng; Zhengxian, Li; Jihong, Du; Yunfeng, Hua; Baoyun, Wang

    2011-10-01

    Materials' surface service property could be enhanced by transition metal nitride hard coatings due to their high hardness, wear and high temperature oxidation resistance, but the higher friction coefficient (0.4-0.9) of which aroused terrible abrasion. In this work, quinternary (Ti,Al,Si,C)N hard coating 3-4 μm was synthesized at 300 °C using plasma enhanced magnetron sputtering system. It was found that the coating's columnar crystals structure was restrained obviously with the increase of C content and a non-columnar crystals growth mode was indicated at the C content of 33.5 at.%. Both the XRD and TEM showed that the (Ti,Al,Si,C)N hard coatings had unique nanocomposite structures composed of nanocrystalline and amorphous nc-(Ti,Al)(C,N)/nc-AlN/a-Si 3N 4/a-Si/a-C. However, the coatings were still super hard with the highest hardness of 41 GPa in spite of the carbon incorporation. That a-C could facilitate the graphitization process during the friction process which could improve the coating's tribological performance. Therefore, that nanocomposite (Ti,Al,Si,C)N coatings with higher hardness (>36 GPa) and a lower friction coefficient (<0.2) could be synthesized and enhance the tribological performance and surface properties profoundly.

  13. Surface modification of TiAlSiCN coatings to improve oxidation protection

    NASA Astrophysics Data System (ADS)

    Kuptsov, K. A.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Shtansky, D. V.

    2015-08-01

    Coatings with high thermal stability and oxidation resistance are highly anticipated for various high-temperature applications. In this work we compare three different approaches to increase the oxidation resistance of nanocomposite TiAlSiCN coatings with exceptionally high thermal stability: (i) deposition of a thin Al top-layer, (ii) Al ion implantation into their topmost surface, and (iii) deposition of a thin AlOx top-layer. The coatings were annealed in air at 1000, 1100, and 1200 °C for 1 h and their oxidation was studied using scanning electron microscopy and glow discharge optical emission spectroscopy. The obtained results demonstrate that the deposition of a thin top-layer of amorphous AlOx increases the oxidation resistance of the TiAlSiCN coatings from 1000 to 1100 °C. This decreases the gap between the high thermal stability (1300 °C) and oxidation resistance of the TiAlSiCN coatings, which is particularly important for high-speed and dry cutting applications. In contrast, the deposition of either a thin Al top-layer or Al ion implantation resulted in a negative effect. The factors affecting the rapid oxidation of such coatings at 1000 and 1100 °C are discussed.

  14. Hybrid Effect on Whisker Orientation Dependence of Composite Strength of Aluminum Cast Alloy Reinforced by Al2O3 Whiskers and SiC Particles

    NASA Astrophysics Data System (ADS)

    Md, Rafiquzzaman; Arai, Yoshio

    The hybrid effect on the orientation dependence of the composite strength of an aluminum cast alloy reinforced by Al2O3 whiskers and SiC particles is studied experimentally and numerically. Two types of specimens are prepared for monotonic bending tests. The longitudinal specimen orientation (maximum stress direction) is parallel to or normal to randomly oriented whiskers in plane. The monotonic strength is 18% higher when the hybrid metal matrix composite (MMC) is subjected to an external load parallel to the random whisker orientation in plane than when the load is perpendicular to the whisker orientation. The whisker orientation dependence of composite strength in hybrid composite is weaker than that in whisker-reinforced composite. On the fracture surface of the specimen loaded along the direction parallel to the random whisker orientation in plane, most whiskers are broken while many de-bonded interfaces between the whiskers and matrix are observed on the fracture surface of the specimen loaded along the direction perpendicular to the whisker orientation. To characterize the hybrid effect on the whisker orientation dependence of composite strength, a three-dimensional hybrid composite unit cell model including one whisker and a few particles under a periodic boundary condition is developed using the finite element method. The hybrid composites have higher whisker stress than whisker-reinforced composite when subjected to an external load parallel to the whisker orientation if these composites have the same total volume fraction of reinforcement and the particles are distributed randomly. Under an external load perpendicular to the whisker orientation, the interface stress of hybrid composites is lower than that of whisker-reinforced composite. As a result, the strength difference for parallel and perpendicular loading conditions of the hybrid composites is smaller than that of whisker-reinforced composite. Thus, the weak whisker orientation effect in the

  15. Weld bead reinforcement removal: A method of improving the strength and ductility of peaked welds in 2219-T87 aluminum alloy plate

    NASA Technical Reports Server (NTRS)

    Lovoy, C. V.

    1979-01-01

    The results of a study to determine the degree to which the ductility and tensile properties of peaked welds could be enhanced by removing the reinforcing bead and fairing the weld nugget into the adjacent parent metal are presented. The study employed 2219-T87 aluminum alloy plate, tungsten inert gas (TIG) welding, and 2319 filler wire. The study concluded that significant improvements in peak weld, ultimate strength, and ductility can be obtained through removal and fairing of the weld reinforcing bead. The specimens so treated and tested in this program exhibited ultimate strength improvements of 2 to 3 percent for peak angles of 5.8 to 10 degrees and 10 to 22 percent for welds with peak angles of 11.7 to 16.9 degrees. It was also determined that removal of the weld bead enhanced the ability of peaked welds to straighten when exposed to cyclic loading at stress levels above the yield strength.

  16. Metalorganic chemical vapor deposition and characterization of (Al,Si)O dielectrics for GaN-based devices

    NASA Astrophysics Data System (ADS)

    Chan, Silvia H.; Tahhan, Maher; Liu, Xiang; Bisi, Davide; Gupta, Chirag; Koksaldi, Onur; Li, Haoran; Mates, Tom; DenBaars, Steven P.; Keller, Stacia; Mishra, Umesh K.

    2016-02-01

    In this paper, we report on the growth and electrical characterization of (Al,Si)O dielectrics grown by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, oxygen, and silane as precursors. The growth rates, refractive indices, and composition of (Al,Si)O films grown on Si(001) were determined from ellipsometry and XPS measurements. Crystallinity and electrical properties of (Al,Si)O films grown in situ on c-plane GaN were characterized using grazing incidence X-ray diffraction and capacitance-voltage with current-voltage measurements, respectively. Si concentration in the films was found to be tunable by varying the trimethylaluminum and/or oxygen precursor flows. The Si incorporation suppressed the formation of crystalline domains, leading to amorphous films that resulted in reduced interfacial trap density, low gate leakage and ultra-low hysteresis in (Al,Si)O/n-GaN MOS-capacitors.

  17. Metalorganic chemical vapor deposition and characterization of (Al,Si)O dielectrics for GaN–based devices

    DOE PAGESBeta

    Chan, Silvia; Mishra, Umesh K.; Tahhan, Maher; Liu, Xiang; Bisi, David; Gupta, Chirag; Koksaldi, Onur; Li, Haoran; Mates, Tom; DenBaars, Steven P.; et al

    2016-01-20

    In this study, we report on the growth and electrical characterization of (Al,Si)O dielectrics grown by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, oxygen, and silane as precursors. The growth rates, refractive indices, and composition of (Al,Si)O films grown on Si(001) were determined from ellipsometry and XPS measurements. Crystallinity and electrical properties of (Al,Si)O films grown in situ on c-plane GaN were characterized using grazing incidence X-ray diffraction and capacitance–voltage with current–voltage measurements, respectively. Si concentration in the films was found to be tunable by varying the trimethylaluminum and/or oxygen precursor flows. The Si incorporation suppressed the formation of crystallinemore » domains, leading to amorphous films that resulted in reduced interfacial trap density, low gate leakage and ultra-low hysteresis in (Al,Si)O/n-GaN MOS-capacitors.« less

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

    PubMed

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

    2014-01-01

    Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants. PMID:24121827

  19. Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal

    PubMed Central

    Chan, Ya-Ting; Kuan, Wen-Hui; Tzou, Yu-Min; Chen, Tsan-Yao; Liu, Yu-Ting; Wang, Ming-Kuang; Teah, Heng-Yi

    2016-01-01

    Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates. PMID:27095071

  20. Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal

    NASA Astrophysics Data System (ADS)

    Chan, Ya-Ting; Kuan, Wen-Hui; Tzou, Yu-Min; Chen, Tsan-Yao; Liu, Yu-Ting; Wang, Ming-Kuang; Teah, Heng-Yi

    2016-04-01

    Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

  1. Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal.

    PubMed

    Chan, Ya-Ting; Kuan, Wen-Hui; Tzou, Yu-Min; Chen, Tsan-Yao; Liu, Yu-Ting; Wang, Ming-Kuang; Teah, Heng-Yi

    2016-01-01

    Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates. PMID:27095071

  2. Effect of confining pressure due to external jacket of steel plate or shape memory alloy wire on bond behavior between concrete and steel reinforcing bars.

    PubMed

    Choi, Eunsoo; Kim, Dongkyun; Park, Kyoungsoo

    2014-12-01

    For external jackets of reinforced concrete columns, shape memory alloy (SMA) wires are easy to install, and they provide active and passive confining pressure; steel plates, on the other hand, only provide passive confining pressure, and their installation on concrete is not convenient because of the requirement of a special device. To investigate how SMA wires distinctly impact bond behavior compared with steel plates, this study conducted push-out bond tests of steel reinforcing bars embedded in concrete confined by SMA wires or steel plates. For this purpose, concrete cylinders were prepared with dimensions of 100 mm x 200 mm, and D-22 reinforcing bars were embedded at the center of the concrete cylinders. External jackets of 1.0 mm and 1.5 mm thickness steel plates were used to wrap the concrete cylinders. Additionally, NiTiNb SMA wire with a diameter of 1.0 mm was wound around the concrete cylinders. Slip of the reinforcing bars due to pushing force was measured by using a displacement transducer, while the circumferential deformation of specimens was obtained by using an extensometer. The circumferential deformation was used to calculate the circumferential strains of the specimens. This study assessed the radial confining pressure due to the external jackets on the reinforcing bars at bond strength from bond stress-slip curves and bond stress-circumferential strain curves. Then, the effects of the radial confining pressure on the bond behavior of concrete are investigated, and an equation is suggested to estimate bond strength using the radial confining pressure. Finally, this study focused on how active confining pressure due to recovery stress of the SMA wires influences bond behavior. PMID:25971115

  3. Microstructure control in iron aluminides by phase decomposition or by mechanical alloying for improved strength and ductility

    SciTech Connect

    Morris, D.G.; Gunther, S.

    1997-12-31

    The iron aluminides based on Fe{sub 3}Al or FeAl being developed for intermediate temperature applications suffer from mediocre room temperature strength and ductility and poor high temperature tensile and creep strength. Attempts to overcome these problems have been restricted by the limited possibilities of structure modification by, for example, precipitation of stable strengthening particles. The present study examines two approached to obtaining two-phase mixtures for improved strength and ductility: by adjusting chemical compositions such that two-phase order-disorder ({alpha}-{alpha}{double_prime}) mixtures are obtained, and by mechanical alloying. Two-phase {alpha}-{alpha}{double_prime} mixtures are obtained by heat treatment of Fe-Al alloys with Al content near 20--24% and in ternary Fe-Al-Si alloys with suitably adjusted Al and Si contents. Microstructures of such alloys can be modified during heat treatments by ordering, precipitation or decomposition, and two-phase mixtures similar to those in the {gamma}-{gamma}{prime} superalloys obtained. Such two-phase alloys show good high temperature tensile and creep strength with some indication of reasonable ductility and reduced environmental sensitivity. Mechanical alloying can easily produce Fe-Al alloys of fine grain size reinforced with stable oxide particles. These structures lead to high room temperature strength with some ductility; controlled recrystallization can significantly modify both strength and ductility.

  4. Structure and properties of the Al/SiC composite material

    NASA Astrophysics Data System (ADS)

    Pugacheva, N. B.; Michurov, N. S.; Bykova, T. M.

    2016-06-01

    Structure has been studied and the distribution of the filler in the samples of the metal-matrix Al/SiC composite containing 50% SiC has been analyzed. The sizes and shapes of the particles of the filler have been determined; the cohesion of the metallic matrix with the filler has been investigated. The analysis of the mechanism of fracture after tensile tests at 350°C and uniaxial compression of the samples of composite at 300 and 600°C has been carried out.

  5. Structure of AlSi-SiC composite foams surface formed by mechanical and thermal cutting

    NASA Astrophysics Data System (ADS)

    Krajewski, Sławomir; Nowacki, Jerzy

    2015-02-01

    The article presents the geometric structure of AlSi-SiC composite foam surface after thermal, mechanical and erosive cutting with regards to its subsequent practical applications. In stereometric measurements of foam surfaces, confocal microscopy was suggested as a method fit for measuring surfaces of high discontinuity ratio that results from porosity. Basic quality parameters of cutting plane were characterised, and technical as well as methodological problems deriving from atypical porous structure of metallic foams were identified. On the basis of the results obtained, the influence of cutting methods on the geometric parameters of foam plane was established, and most favourable cutting conditions were determined.

  6. Effect of Cooling Rate on Phosphorus Removal During Al-Si Solvent Refining

    NASA Astrophysics Data System (ADS)

    Li, Yanlei; Ban, Boyuan; Li, Jingwei; Zhang, Taotao; Bai, Xiaolong; Chen, Jian; Dai, Songyuan

    2015-04-01

    The effect of cooling rate on phosphorus removal during Al-Si solvent refining is studied during solar grade silicon purification. It is found that the phosphorus removal rate is controlled by kinetic factors. When the cooling rate decreases, the phosphorus removal rate increases. A concept of apparent segregation coefficient of phosphorus is introduced to characterize the phosphorous removal ability. It increases with the decrease in the average solidification temperature between 910.5 K and 1050.5 K (637.5 °C and 777.5 °C).

  7. Electromigration performance improvement of Al-Si-Cu/TiN/Ti/n+Si contact

    NASA Astrophysics Data System (ADS)

    Shi, Gang; Sun, Zhen; Xu, Geng-Fu; Min, Yun-Hao; Luo, Jun-Yi; Lu, Yong; Li, Bing-Zong; Qu, Xin-Ping; Qian, Gang; Doan, My T.; Lee, Edmund

    1998-02-01

    In this study, two different processes, with and without rapid thermal annealing (RTA), have been compared for the Al-Si- Cu/TiN/Ti multilayer contact on n+ diffusions. A series of wafer level reliability (WLR) measurement performed on a test structure with two 1.08 X 1.08 micrometer2 contacts on n+ diffusion. The results show that RTA can increase contact electromigration (EM) lifetime dramatically. The XRD, AES and TEM analysis indicate that this improvement is attributed to oxygen stuffing in TiN, phase change of TiN and TiSi2 formation at the interface of Ti and Si.

  8. Benzimidazole as corrosion inhibitor for heat treated 6061 Al- SiCp composite in acetic acid

    NASA Astrophysics Data System (ADS)

    Chacko, Melby; Nayak, Jagannath

    2015-06-01

    6061 Al-SiCpcomposite was solutionizedat 350 °C for 30 minutes and water quenched. It was then underaged at 140 °C (T6 treatment). The aging behaviour of the composite was studied using Rockwell B hardness measurement. Corrosion behaviour of the underaged sample was studied in different concentrations of acetic acid and at different temperatures. Benzimidazole at different concentrations was used for the inhibition studies. Inhibition efficiency of benzimidazole was calculated for different experimental conditions. Thermodynamic parameters were found out which suggested benzimidazole is an efficient inhibitor and it adsorbed on to the surface of composite by mixed adsorption where chemisorption is predominant.

  9. Characterization of Hypereutectic Al-Si Powders Solidified under Far-From Equilibrium Conditions

    SciTech Connect

    Y.E. Kalay; L.S. Chumbley; I.E. Anderson; R.E. Napolitano

    2007-07-01

    The rapid solidification microstructure of gas-atomized Al-Si powders of 15, 18, 25, and 50 wt pct Si were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In order of increasing particle size, the powders exhibited microcellular Al, cellular/dendritic Al, eutectic Al, and primary Si growth morphologies. Interface velocity and undercooling were estimated from measured eutectic spacing based on the Trivedi-Magnin-Kurz (TMK) model, permitting a direct comparison with theoretical predictions of solidification morphology. Based on our observations, additional conditions for high-undercooling morphological transitions are proposed as an extension of coupled-zone predictions.

  10. Degradation of Al/SiCp composites produced with rice-hull ash and aluminum cans.

    PubMed

    Escalera-Lozano, R; Gutiérrez, C A; Pech-Canul, M A; Pech-Canul, M I

    2008-01-01

    The use of recycling aluminum from beverage containers and rice-hull ash (RHA) offers to be an attractive alternative for the economic production of Al/SiCp composites. However, corrosion phenomena in the composites represent technological barriers yet to be resolved before they can be exploited to their full potential. A simple methodology involving characterization by XRD, SEM, EDX, FTIR and ICP was designed in order to investigate the causes of the rapid degradation in a humid environment of Al/SiCp composites produced with RHA and aluminum cans. Results reveal that the use of RHA was beneficial to avoid degradation through the formation and subsequent hydration of the Al4C3 phase. However with condensed moisture acting as an electrolyte, localized corrosion took place with aggressive damage manifested by the disintegration of the composite into a powdery mixture. The relevant corrosion mechanism was mainly attributed to microgalvanic coupling between the Mg2Si intermetallic compound and the matrix (although other phases such as SiC, Si, MgAl2O4 could also work as microcathodes). PMID:17320370

  11. Lamellar Spacing Selection in Al-Si Eutectic System: a Theoretical Investigation

    NASA Technical Reports Server (NTRS)

    Catalina, Adrian V.; Sen, Subhayu; Curreri, Peter A.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    It is well known that irregular eutectics such as Al-Si and Fe-C exhibit larger lamellar spacings and undercoolings compared to the predictions made by the Jackson and Hunt (JH) theory. In this paper, we reexamine the JH theory and relax some of the assumptions used in that treatment. The modified theoretical model has enhanced capabilities to predict the lamellar spacing in both regular and irregular eutectics. For the Al-Si system in particular we identified two different spacing selection mechanisms:a) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing lambda(sub I); b) the average spacing in the microstructure (lambda(sub av) greater than lambda(sub I)) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model a semi-empirical expression has been developed to account for the influence of the temperature gradient. Application of a Mullin and Sekerka type stability analysis for eutectics will also be presented and the results compared to the modified JH model. It will be shown that the both theoretical approaches are in good agreement with each other and also with the published experimental measurements.

  12. A finite element model of the effects of primary creep in an Al-SiC metal matrix composite

    NASA Astrophysics Data System (ADS)

    Atkins, Steven L.; Gibeling, Jeffery C.

    1995-12-01

    A two dimensional axisymmetric finite element model has been developed to study the creep behavior of a high-temperature aluminum alloy matrix (alloy 8009) reinforced with 11 vol pct silicon carbide paniculate. Because primary creep represents a significant portion of the total creep strain for this matrix alloy, the emphasis of the present investigation is on the influence of primary creep on the high-temperature behavior of the composite. The base alloy and composite are prepared by rapid solidification processing, resulting in a very fine grain size and the absence of precipitates that may complicate modeling of the composite. Because the matrix microstructure is unaffected by the presence of the SiC paniculate, this material is particularly well suited to continuum finite element modeling. Stress contours, strain contours, and creep curves are presented for the model. While the final distribution of stresses and strains is unaffected by the inclusion of primary creep, the overall creep response of the model reveals a significant primary strain transient. The effects of true primary creep are more significant than the primary-like transient introduced by the redistribution of stresses after loading. Examination of the stress contours indicates that the matrix axial and shear components become less uniform while the effective stress becomes more homogeneous as creep progresses and that the distribution of stresses do not change significantly with time after the strain rate reaches a steady state. These results also confirm that load transfer from the matrix to reinforcement occurs primarily through the shear stress. It is concluded that inclusion of matrix primary creep is essential to obtaining accurate representations of the creep response of metal matrix composites.

  13. Oxidation and microstructure evolution of Al-Si coated Ni3Al based single crystal superalloy with high Mo content

    NASA Astrophysics Data System (ADS)

    Tu, Xiaolu; Peng, Hui; Zheng, Lei; Qi, Wenyan; He, Jian; Guo, Hongbo; Gong, Shengkai

    2015-01-01

    A Si modified aluminide (Al-Si) coating was prepared on a Ni3Al based single crystal superalloy with high Mo content by high-activity pack cementation. Cyclic oxidation test at 1150 °C was carried out and the microstructure evolution of the coating was investigated. The results show that the oxidation resistance of the substrate was greatly increased by applying an Al-Si coating. During oxidation, outward diffusion of Mo was effectively blocked due to its high affinity with Si. Besides, a layered structure was formed as a result of the elements inter-diffusion. An obvious degradation of the Al-Si coating was observed after 100 h oxidation. Possible mechanisms related to the oxidation and elements inter-diffusion behaviours were also discussed.

  14. Tribological behavior of Ti-Al-Si-C-N hard coatings deposited by hybrid arc-enhanced magnetron sputtering

    SciTech Connect

    Wu Guizhi; Ma Shengli; Xu Kewei; Chu, Paul K

    2012-03-15

    Ti-Al-Si-C-N hard coatings are deposited on high speed steel by hybrid arc-enhanced magnetron sputtering, and the hardness, adhesion, and tribological behavior are studied. On account of the nanocomposite structure, the coatings possess hardness of more than 30 GPa. Failure of the coating during the scratch test is due to the buckling and wedge spallation failure mechanism. Compared to Ti-Al-Si-N, the presence of C in the Ti-Al-Si-C-N coatings leads to reduced friction coefficient and wear rate, indicating effective lubrication rendered by amorphous C. According to the wear tracks examined by scanning electron microscopy, the wear mechanism can be explained by plowing abrasion.

  15. Investigation of carbonized layer on surface of NaAlSi glass fibers

    NASA Astrophysics Data System (ADS)

    Pentjuss, E.; Lusis, A.; Bajars, G.; Gabrusenoks, J.

    2013-12-01

    There are presented and discussed experimental results about carbonate shell on the sodium rich alumosilicate (NaAlSi) glass fibers and carbonization in wet air atmosphere and water uptake kinetic of such fiber fabrics. The analyzes of water uptake kinetic by regression technique, leaching and heating of carbonized glass fabrics helped to separate stages of fast and slow processes between fiber and carbonate shell and air atmosphere. The shell contains mixture of trona and hydrated sodium carbonate. Heating converts both substances to sodium carbonate. The weight uptake after heating encounters two fast exponential processes associated with water absorption on the surface of carbonated shell and its diffusion into volume. The slow process associates with CO2 and H2O absorption from air, hydration and sodium carbonate conversion to trona.

  16. Mesoscale Approach to Feldspar Dissolution: Quantification of Dissolution Incongruency Based on Al/Si Ordering State

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Min, Y.; Jun, Y.

    2012-12-01

    Dissolution mechanism of aluminosilicates is important for understanding natural and anthropogenic carbon cycles. The total mass of atmospheric CO2 is regulated by the weathering of silicate minerals, and the fate of geologically sequestered CO2 is affected by the interactions between brine, sandstone, caprock, and CO2, which is initiated by mineral dissolution. It has been shown through both experimental and ab initio studies that the dissolution/weathering reactivities of Al and Si in the matrix of an aluminosilicate can be different under many conditions. A subsequent observation is that the release rates of Al and Si, both from the same mineral, may not be stoichiometric when compared to the bulk chemistry of the mineral. For a very long time, the relationship between mineral dissolution incongruency and mineral crystallographic properties remain largely qualitative and descriptive. Here we study the dissolution incongruency of feldspars, the most abundant aluminosilicate on earth. Mineral dissolution experiments for a series of alkali feldspars (albite, anorthoclase, sanidine, and microcline) and plagioclases (oligoclase, andesine, labradorite, bytownite, and anorthite) were conducted at pH 1.68 under ambient conditions. Synchrotron-based X-ray diffraction (HR-XRD), Fourier transform infrared spectroscopy (FTIR), and water chemistry analysis (ICP-MS) are combined to examine the effect of Al/Si ordering on mineral dissolution. Our analysis based on a C1 structure model shows that the incongruency, stemming from the different reactivities of Al-O-Si and Si-O-Si linkages in feldspar's framework, is quantifiable and closely related to the Al/Si ordering state of a feldspar. Our results also suggest that the more random the Al/Si distribution of a mineral, the greater the dissolution incongruency. Our results have significant implications for understanding water-rock interactions. First, when studying the effect of water chemistry on water-rock interaction, smaller

  17. Infrared observation of thermally activated oxide reduction within Al/SiOx/Si tunnel diodes

    NASA Astrophysics Data System (ADS)

    Brendel, R.; Hezel, R.

    1992-05-01

    Electron-beam-evaporated aluminum/silicon oxide/silicon tunnel diodes with an initial oxide thickness of 1.3 nm have been annealed for up to 1 h at temperatures from 213 to 369 °C. They have been investigated by infrared grazing internal reflection (GIR) spectroscopy and current-voltage measurements. The measured IR spectra were analyzed by computer modeling. All spectral features could be explained self-consistently within a Al/AlOy/SiOx/Si layer model. In the as-deposited state less than 0.6 monolayers of Al—O bonds are formed at the Al/SiOx interface. A thermally activated reduction of the ultrathin oxide film by Al was observed. The changes in the current-voltage curves induced by slight annealing (1 min at 213 °C) are accompanied by changes in the insulator-bonding structure, which GIR is sensitive enough to detect.

  18. Neutron absorption of Al-Si-Mg-B4C composite

    NASA Astrophysics Data System (ADS)

    Abdullah, Yusof; Ibrahim, Anis Syukriah; Daud, Abdul Razak; Yusof, Mohd Reusmaazran

    2016-01-01

    Al-Si-Mg-B4C composites containing 2-8 wt% of B4C were prepared by stir casting technique. Homogenization treatment was carried out at temperatures of 540°C for 4 houra and followed by ageing at 180°C for 2 houra. Microstructure and phase identification were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Neutron absorption study was investigated using neutron source Am/Be241. The result indicated that higher B4C content improved the neutron absorption property. Meanwhile homogeneity of the composite was increased by ageing processes. This composite is potential to be used as neutron shielding material especially for nuclear reactor application.

  19. Wear Behavior of Aluminum Alloy 6061-Based Composites Reinforced with SiC, Al2O3, and Red Mud: A Comparative Study

    NASA Astrophysics Data System (ADS)

    Singla, Yogesh Kumar; Chhibber, Rahul; Bansal, Hitesh; Kalra, Anil

    2015-09-01

    Metal-matrix composites are widely used in shipping, aerospace, automotive, and nuclear applications. Research attempts have been made in the past to reduce the cost of processing of composites, decrease the weight of the composites, and increase the desired performance characteristics. In this research article, an attempt has been made in using red mud obtained as an industrial waste during the production of aluminum from bauxite ore. This article discusses the novel findings of the experimental study on the dry sliding wear behavior of aluminum alloy 6061-based composites reinforced individually with red mud, SiC, and Al2O3. The microstructural characterization of the composites provides the further insight into the structure—wear behavior of the processed composites.

  20. Development and Characterization of Carbon Nanotubes (CNTs) and Silicon Carbide (SiC) Reinforced Al-based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gujba, Kachalla Abdullahi

    increase in internal strains were observed as milling progressed with increase in wt.% reinforcement due to the severe plastic deformation. Al/SiC and Al/CNTs were successfully consolidated by the SPS at sintering temperatures of 400, 450 and 500°C with SiC at 5, 12 and 20wt% and 0.5wt%CNT milled for 20hrs and 3 hrs respectively. It was obtained that sintering temperature of 500°C was the most suitable as the densification achieved for SiC reinforced sample was above 98% and 100% for unreinforced sample. The hardness increased with increasing SiC content from 0, 5 to 12 wt% i.e 68, 82, 85 respectively. At 20%wt of SiC a slight decrease in the hardness was observed i.e. 70 which might be attributed to high wt.% SiC, a similar trend was observed for the other alloy studied. For CNT reinforced samples, the hardness and densification increased significantly and 100% densification was obtained at 500ºC, a hardness value from 68 to 82 was achieved from 0 to 0.5wt%CNT with a similar trend to the other alloy of interest. Conclusively, sintering of both alloys at 500ºC and above is the most suitable, the use of SiCp and CNTs as reinforcements improved the hardness, 12wt% SiC showed better hardness values than 20wt% SiC at all three temperatures and the Al alloy containing higher Si in its alloying elements showed better hardness values using the same reinforcement and sintering parameters.

  1. Tensile Properties of Nano AL2O3 Particulate-Reinforced Aluminum Matrix Composites by Mechanical Alloying and Hot Extrusion

    NASA Astrophysics Data System (ADS)

    Mehdinia, M.; Jenabali Jahromi, S. A.

    The powder of the micro Al and variant volume fractions of nano Al2O3 were milled by a high energy planetary ball-mill. By milling, a homogenous distribution of nano Al2O3 particles in the metal matrix were developed. Then the milled powder was cold compressed and sintered at 545°C for one hr. The mold and the sintered sample hold in a furnace until the temperature reached 545°C. Then the hot 27mm diameter sample was extruded to 6mm diameter. From the extruded specimens, tensile, hardness and microstructure of the prepared specimens were determined. By these tests the effect of milling time, the percent of nano-particles and the microstructure were evaluated. The hardness and tensile behaviors of aluminum matrix composites reinforced with nano Al2O3 particulate have been found to increase remarkably with the volume fraction of the reinforcement.

  2. EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel

    SciTech Connect

    Cheng, Wei-Jen Wang, Chaur-Jeng

    2012-02-15

    5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.

  3. Superthermostability of nanoscale TIC-reinforced copper alloys manufactured by a two-step ball-milling process

    NASA Astrophysics Data System (ADS)

    Wang, Fenglin; Li, Yunping; Xu, Xiandong; Koizumi, Yuichiro; Yamanaka, Kenta; Bian, Huakang; Chiba, Akihiko

    2015-12-01

    A Cu-TiC alloy, with nanoscale TiC particles highly dispersed in the submicron-grained Cu matrix, was manufactured by a self-developed two-step ball-milling process on Cu, Ti and C powders. The thermostability of the composite was evaluated by high-temperature isothermal annealing treatments, with temperatures ranging from 727 to 1273 K. The semicoherent nanoscale TiC particles with Cu matrix, mainly located along the grain boundaries, were found to exhibit the promising trait of blocking grain boundary migrations, which leads to a super-stabilized microstructures up to approximately the melting point of copper (1223 K). Furthermore, the Cu-TiC alloys after annealing at 1323 K showed a slight decrease in Vickers hardness as well as the duplex microstructure due to selective grain growth, which were discussed in terms of hardness contributions from various mechanisms.

  4. Mechanical properties and 95 C aging characteristics of zircon-reinforced Zn-4Al-3Cu alloy

    SciTech Connect

    Li, B.J.; Chao, C.G.

    1996-03-01

    A process for preparing zinc alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles in Zn-4Al-3Cu (ZAS) alloy melts and subsequently casting these melts in permanent molds. It was found that additions of zircon resulted in an increase in the sliding wear resistance and in the proportional limit in compression. The aging characteristics of the ZAS alloy have also been investigated by hardness tests, dilatometry technique, and transmission electron microscopy observations. There are two kinds of precipitates that occur during the aging process. The {alpha}-phase precipitates form the {eta} phase in the early stage of aging and the copper-rich {var_epsilon}-phase precipitates from the {eta} phase in the later stage of aging. Therefore, there are two peaks in the hardening curve caused by both {alpha}-phase and {var_epsilon}-phase precipitation. The {alpha}-phase precipitation induces the dimensional shrinkage, and the copper-rich {var_epsilon} phase precipitation results in dimensional expansion. Zircon particles existing in ZAS alloy reduce the maximum shrinkage from 353 {times} 10{sup {minus}6} for the monolith to 167 {times} 10{sup {minus}6} for the composite. Two groups of parallel {alpha}-phase plates had formed within the {eta} dendrite during aging at 95 C. The orientation relationship between the {alpha} phase and matrix was determined as [{bar 1}101]{sub {eta}}{parallel}[1{bar 1}0]{sub {alpha}}, (11{bar 2}0){sub {eta}}{parallel}(111){sub {alpha}}.

  5. Femtosecond laser-induced subwavelength ripples on Al, Si, CaF2 and CR-39

    NASA Astrophysics Data System (ADS)

    Bashir, Shazia; Shahid Rafique, M.; Husinsky, Wolfgang

    2012-03-01

    The formation of self-organized subwavelength ripples on Al, Si, CaF2 and CR-39 induced by 25 fs laser pulses at central wavelength of 800 nm has been observed under certain experimental conditions. In case of Al subwavelength gratings with periodicities ranging from 20 to 220 nm are reported. For CaF2 the periodicity goes up to 625 nm. In case of Si, nano-gratings have the periodicity of 10-100 nm. The interspacing of these gratings is 60 nm in case of CR-39. These features which are significantly shorter than incident laser wavelength are observed at the irradiation fluence slightly higher than the ablation threshold regardless of the target material. In addition to these nanoripples, classical or microripples with an average spacing of 1-2 μm have also been registered on irradiated surfaces of Al and Si. These microripples have appeared at fluence higher than that is required for nanoripple-formation. It has been found that the formation of the laser-induced ripples is strongly dependent and quite sensitive to the incident laser fluence and the selection of material.

  6. Al-Si/SiC nanoparticles composites synthesized by double stir casting.

    PubMed

    Aigbodion, V S

    2011-11-01

    The present invention provides Al-Si/SiC nanoparticles composites with the composition of 7%Si, 15%SiC with average particle size (APS) of SiC, 20, 30, 40 nm and 65μm using a novel double stir casting method. The inventive nano-composites by double stir casting show a nearly uniform distribution and good dispersion of the nano-particles within the Al matrix, although small agglomeration was found in the matrix of the micro-composite. The enhancement in values of impact strength and tensile strength observed in this study is due to small particle size and good distribution of the nano particles, which were confirmed by SEM spectrum. Patents WO 2010135848 and WO2011/011601 have some relevant information about the topic developed in this study, because the principle in both cases relies on the interactions between metal matrix and the nano-particles. Hence, novel double stir casting method can be used to improve the properties of nano-composites. PMID:21428904

  7. Transformation of Ba-Al-Si precursors to celsian by high-temperature oxidation and annealing

    NASA Astrophysics Data System (ADS)

    Schmutzler, Hans J.; Sandhage, Kenneth H.

    1995-02-01

    Celsian (monoclinic BaO · A12O3 · 2SiO2) is being considered as a matrix material for ceramic composites used in high-temperature structural applications. The present article describes the synthesis of celsian by the oxidation and annealing of solid, malleable, metallic Ba-Al-Si precursors. The phase and microstructural evolution after various stages of oxidation at 300 °C to 1260 °C in pure oxygen at 1 atm pressure have been examined by X-ray diffraction (XRD) and electron microprobe analyses (EPMA). Barium peroxide, BaO2, formed rapidly during oxidation at 300 °C, with aluminum and silicon remaining largely as unoxidized particles in a BaO2 matrix. Between 300 °C and 500 °C, barium orthosilicate, Ba2Si04, formed by a solid-state reaction between barium peroxide and unoxidized silicon. Further exposure to temperatures between 500 °C and 1200 °C resulted in the oxidation of aluminum and of residual silicon. The oxidized silicon reacted with the barium orthosilicate matrix to yield higher silica-containing barium silicates that, in turn, reacted with alumina or mullite to form metastable hexacelsian (hexagonal BaO-A12O3 · 2SiO2). Celsian was then obtained by further exposure to peak temperatures ≤1260°C.

  8. Residual stress characterization of Al/SiC nanoscale multilayers using X-ray

    SciTech Connect

    Singh, DRP; Deng, X.; Chawla, N.; Bai, J.; Hubbard, Camden R; Tang, G; Shen, Y-L

    2010-01-01

    Nanolayered composites are used in a variety of applications such as wear resistant coatings, thermal barrier coatings, optical and magnetic thin films, and biological coatings. Residual stresses produced in these materials during processing play an important role in controlling their microstructure and properties. In this paper, we have studied the residual stresses in model metal-ceramic Al/SiC nanoscale multilayers produced by physical vapor deposition (magnetron sputtering). X-ray synchrotron radiation was used to measure stresses in the multilayers using the sin{sup 2} {Psi} technique. The stresses were evaluated as a function of layer thicknesses of Al and SiC and also as a function of the number of layers. The stress state of Al in the multilayer was largely compressive, compared to single layer Al stresses. This is attributed to a peening mechanism due to bombardment of the Al layers by SiC and Ar neutrals during deposition. The stress evolution was numerically modeled by a simplified peening process to qualitatively explain the Al thickness-dependent residual stresses.

  9. Residual Stress Characterization of Al/SiC Nanoscale Multilayers using X-ray

    SciTech Connect

    D Singh X Deng; N Chawla; J Bai; C Hubbard; G Tang; Y Shen

    2011-12-31

    Nanolayered composites are used in a variety of applications such as wear resistant coatings, thermal barrier coatings, optical and magnetic thin films, and biological coatings. Residual stresses produced in these materials during processing play an important role in controlling their microstructure and properties. In this paper, we have studied the residual stresses in model metal-ceramic Al/SiC nanoscale multilayers produced by physical vapor deposition (magnetron sputtering). X-ray synchrotron radiation was used to measure stresses in the multilayers using the sin{sup 2} {psi} technique. The stresses were evaluated as a function of layer thicknesses of Al and SiC and also as a function of the number of layers. The stress state of Al in the multilayer was largely compressive, compared to single layer Al stresses. This is attributed to a peening mechanism due to bombardment of the Al layers by SiC and Ar neutrals during deposition. The stress evolution was numerically modeled by a simplified peening process to qualitatively explain the Al thickness-dependent residual stresses.

  10. Predicting the Thermal Conductivity of AlSi/Polyester Abradable Coatings: Effects of the Numerical Method

    NASA Astrophysics Data System (ADS)

    Bolot, Rodolphe; Seichepine, Jean-Louis; Qiao, Jiang Hao; Coddet, Christian

    2011-01-01

    The final target of this study is to achieve a better understanding of the behavior of thermally sprayed abradable seals such as AlSi/polyester composites. These coatings are used as seals between the static and the rotating parts in aero-engines. The machinability of the composite coatings during the friction of the blades depends on their mechanical and thermal effective properties. In order to predict these properties from micrographs, numerical studies were performed with different software packages such as OOF developed by NIST and TS2C developed at the UTBM. In 2008, differences were reported concerning predictions of effective thermal conductivities obtained with the two codes. In this article, a particular attention was paid to the mathematical formulation of the problem. In particular, results obtained with a finite difference method using a cell-centered approach or a nodal formulation allow explaining the discrepancies previously noticed. A comparison of the predictions of the computed effective thermal conductivities is thus proposed. This study is part of the NEWAC project, funded by the European Commission within the 6th RTD Framework programm (FP6).

  11. Prediction of Cooling Curves for Squeeze Cast Al/SiCp Composites Using Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Gurusamy, P.; Balasivanandha Prabu, S.; Paskaramoorthy, R.

    2015-04-01

    This paper reports the experimental and finite element analyses of the solidification behavior of Al/SiCp composites, fabricated by the squeeze casting technique. Experiments were carried out by varying the melt temperatures for cylindrical-shaped composite castings. The composite samples were produced at the following constant temperatures: melt—1023 K, 1073 K, 1123 K, and 1173 K (750 °C, 800 °C, 850 °C, and 900 °C); and die—673 K (400 °C). The pressure applied throughout the experiment is 100 MPa. The melt temperature shows significant influence on the solidification behavior of the metal matrix composite. It was observed that the solidification time was 40 seconds when the melt temperature was 1023 K (750 °C) but it increased to 51 seconds when the melt temperature was at 1173 K (900 °C). The results also showed that the cooling rate decreased on increasing the melt temperature. Cooling curves for our system, squeeze cast composites, were predicted using the finite element software ANSYS. K-type thermocouples were interfaced to the die and the microcomputer from which the experimental cooling curves were constructed. The experimental and predicted cooling curves were then compared. While both show similar trends, the finite element analysis consistently under-predicts the temperature. In addition, finite element stress analysis reveals that both radial and tangential thermal stresses increase with the melt temperature.

  12. Crystallization of LiAlSiO4 Glass in Hydrothermal Environments at Gigapascal Pressures-Dense Hydrous Aluminosilicates.

    PubMed

    Spektor, Kristina; Fischer, Andreas; Häussermann, Ulrich

    2016-08-15

    High-pressure hydrothermal environments can drastically reduce the kinetic constraints of phase transitions and afford high-pressure modifications of oxides at comparatively low temperatures. Under certain circumstances such environments allow access to kinetically favored phases, including hydrous ones with water incorporated as hydroxyl. We studied the crystallization of glass in the presence of a large excess of water in the pressure range of 0.25-10 GPa and at temperatures from 200 to 600 °C. The p and T quenched samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and IR spectroscopy. At pressures of 0.25-2 GPa metastable zeolite Li-ABW and stable α-eucryptite are obtained at low and high temperatures, respectively, with crystal structures based on tetrahedrally coordinated Al and Si atoms. At 5 GPa a new, hydrous phase of LiAlSiO4, LiAlSiO3(OH)2 = LiAlSiO4·H2O, is produced. Its crystal structure was characterized from single-crystal X-ray diffraction data (space group P21/c, a = 9.547(3) Å, b = 14.461(5) Å, c = 5.062(2) Å, β = 104.36(1)°). The monoclinic structure resembles that of α-spodumene (LiAlSi2O6) and constitutes alternating layers of chains of corner-condensed SiO4 tetrahedra and chains of edge-sharing AlO6 octahedra. OH groups are part of the octahedral Al coordination and extend into channels provided within the SiO4 tetrahedron chain layers. At 10 GPa another hydrous phase of LiAlSiO4 with presently unknown structure is produced. The formation of hydrous forms of LiAlSiO4 shows the potential of hydrothermal environments at gigapascal pressures for creating truly new materials. In this particular case it indicates the possibility of generally accessing pyroxene-type aluminosilicates with crystallographic amounts of hydroxyl incorporated. This could also have implications to geosciences by representing a mechanism of water storage and transport in the depths of the Earth. PMID:27482770

  13. Swelling of U(Mo)-Al(Si) dispersion fuel under irradiation - Non-destructive analyses of the LEONIDAS E-FUTURE plates

    NASA Astrophysics Data System (ADS)

    Van den Berghe, S.; Parthoens, Y.; Charollais, F.; Kim, Y. S.; Leenaers, A.; Koonen, E.; Kuzminov, V.; Lemoine, P.; Jarousse, C.; Guyon, H.; Wachs, D.; Keiser, D., Jr.; Robinson, A.; Stevens, J.; Hofman, G.

    2012-11-01

    In the framework of the elimination of High-Enriched Uranium (HEU) from the civil circuit, the search for an appropriate fuel to replace the high-enriched research reactor fuel in those reactors that currently still require it for their operation has led to the development of a U-7 wt.%Mo alloy based dispersion fuel with an Al-Si matrix. The European LEONIDAS program, joining SCK•CEN, ILL, CEA and AREVA-CERCA, is aimed at the qualification of such a fuel for the use in high power conditions. The first experiment of the program, designated E-FUTURE, was performed to select the appropriate matrix Si concentration and fuel plate post-production heat treatment parameters for further qualification. It consisted of the irradiation of four distinct (4% and 6% Si, 3 different heat treatments) full size, flat fuel plates in the BR2 reactor. The irradiation conditions were relatively severe: 470 W/cm2 peak BOL power, with a ˜70% 235U peak burnup.

  14. Spray-atomized and codeposited 6061 Al/SiCp composites

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Lavernia, Enrique J.

    1991-08-01

    Spray atomization and codeposition processes have received considerable attention for the synthesis of discontinuously reinforced metal-matrix composites. This methodology involves the mixing of reinforcements and matrix under thermal conditions such that the matrix contains both solid and liquid phases. In principle, such an approach avoids the extreme thermal excursions, with concomitant degradation in interfacial properties and extensive macrosegregation, normally associated with casting processes. Furthermore, this approach also eliminates the need to handle fine reactive particulates normally associated with powder metallurgical processes. To investigate the utility of this process for the preparation of metal-matrix composites, several silicon carbide particulate-reinforced 6061 Al composites were prepared. The spray-atomized and codeposited materials exhibited attractive combinations of strength, elastic modulus and elongation, although further work is needed to optimize their properties.

  15. Hydrogen bridging in the compounds X2H (X=Al,Si,P,S)

    NASA Astrophysics Data System (ADS)

    Owens, Zachary T.; Larkin, Joseph D.; Schaefer, Henry F.

    2006-10-01

    X2H hydrides (X =Al, Si, P, and S) have been investigated using coupled cluster theory with single, double, and triple excitations, the latter incorporated as a perturbative correction [CCSD(T)]. These were performed utilizing a series of correlation-consistent basis sets augmented with diffuse functions (aug-cc-pVXZ, X =D, T, and Q). Al2H and Si2H are determined to have H-bridged C2v structures in their ground states: the Al2H ground state is of B12 symmetry with an Al-H-Al angle of 87.6°, and the Si2H ground state is of A12 symmetry with a Si-H-Si angle of 79.8°. However, P2H and S2H have nonbridged, bent Cs structures: the P2H ground state is of A'2 symmetry with a P-P-H angle of 97.0°, and the S2H ground state is of A'2 symmetry with a S-S-H angle of 93.2°. Ground state geometries, vibrational frequencies, and electron affinities have been computed at all levels of theory. Our CCSD(T)/aug-cc-pVQZ adiabatic electron affinity of 2.34eV for the Si2H radical is in excellent agreement with the photoelectron spectroscopy experiments of Xu et al. [J. Chem. Phys. 108, 7645 (1998)], where the electron affinity was determined to be 2.31±0.01eV.

  16. Improved optical storage properties of NaAlSiO4: Tb3+ induced by Bi3+

    NASA Astrophysics Data System (ADS)

    Zhou, Junhe; Yu, Xue; Wang, Ting; Zhou, Dacheng; Qiu, Jianbei

    2016-07-01

    NaAlSiO4: Tb3+, Bi3+ phosphor was synthesized with green long persistent luminescence (LPL) and photo-stimulated luminescence (PSL) observed. The influence of metal ion Bi3+ on the optical storage properties of NaAlSiO4: Tb3+ was investigated in detail. The emitter Tb3+ introduced two kinds of traps located at 350 K (TA) and 440 K (TB) in the thermoluminescence (TL) glow curve. Bi3+ as a codopant ion introduced a new trap peaking at 390 K (TC), which contributed to the improved LPL properties. Besides, owing to the existence of deep and stable trap TB, green PSL can still be observed after 72 h since the excitation was stopped. Accordingly, the mechanism of LPL and PSL process was discussed briefly.

  17. The effect of residual stress on the fatigue crack growth behavior of Al-Si-Mg cast alloys—Mechanisms and corrective mathematical models

    NASA Astrophysics Data System (ADS)

    Lados, Diana A.; Apelian, Diran

    2006-01-01

    The fatigue crack growth (FCG) behavior of various types of alloys is significantly affected by the presence of residual stress induced by manufacturing and post-manufacturing processes. There is a qualitative understanding of the effects of residual stress on fatigue behavior, but the effects are not comprehensively quantified or accounted for. The difficulty in quantifying these effects is largely due to the complexity of residual-stress measurements (especially considering that parts produced in similar conditions can have different residual-stress levels) and the lack of mathematical models able to convert experimental data with residual stress into residual-stress-free data. This article provides experimental, testing, and mathematical techniques to account for residual-stress effects on crack growth rate data, together with two methods for eliminating residual stresses in crack growth test specimens. Fracture-mechanics concepts are used to calculate, in simple and convenient ways, stress-intensity factors caused by residual stresses. The method is advantageous, considering that stress-intensity factors are determined before the actual test is conducted. Further on, residual-stress-intensity factors are used to predict the residual-stress distribution in compact tension (CT) specimens prior to testing. Five cast Al-Si-Mg alloys with three Si levels (in unmodified (UM) as well as Sr-modified (M) conditions) were analyzed both with and without residual stress. Fatigue cracks are grown under both constant stress ratio, R=0.1, and constant maximum stress-intensity factor, K max = const., conditions. The mechanisms involved in crack growth through residual-stress fields are presented.

  18. 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.

  19. Thermodynamics of open networks: Ordering and entropy in NaAlSiO4 glass, liquid, and polymorphs

    USGS Publications Warehouse

    Richet, P.; Robie, R.A.; Rogez, J.; Hemingway, B.S.; Courtial, P.; Tequi, C.

    1990-01-01

    The thermodynamic properties of carnegieite and NaAlSiO4 glass and liquid have been investigated through Cp determinations from 10 to 1800 K and solution-calorimetry measurements. The relative entropies S298-S0 of carnegieite and NaAlSiO4 glass are 118.7 and 124.8 J/mol K, respectively. The low-high carnegieite transition has been observed at 966 K with an enthalpy of transition of 8.1??0.3 kJ/mol, and the enthalpy of fusion of carnegieite at the congruent melting point of 1799 K is 21.7??3 kJ/mol. These results are consistent with the reported temperature of the nepheline-carnegieite transition and available thermodynamic data for nepheline. The entropy of quenched NaAlSiO4 glass at 0 K is 9.7??2 J/mol K and indicates considerable ordering among AlO4 and SiO4 tetrahedra. In the liquid state, progressive, temperature-induced Si, Al disordering could account for the high configurational heat capacity. Finally, the differences between the entropies and heat capacities of nepheline and carnegieite do not seem to conform to current polyhedral modeling of these properties ?? 1990 Springer-Verlag.

  20. Development of dispersion U(Mo)/Al-Si miniplates fabricated at 500 °C with Al 6061 as cladding

    NASA Astrophysics Data System (ADS)

    Mirandou, M. I.; Aricó, S. F.; Balart, S. N.; Fabro, J. O.

    2015-02-01

    In the frame of U(Mo) dispersion fuel elements qualification, Si additions to Al matrix arose as a promising solution to the unacceptable failures found when pure Al is used. Analysis of as-fabricated fuel plates made with Al-Si matrices demonstrated that good irradiation behavior is correlated with the formation during fabrication of a Si-containing interaction layer around the U(Mo) particles. Thus, the analysis of the influence of fabrication parameters becomes important. Studies on Al-Si dispersion miniplates fabricated in CNEA, Argentina, have been initiated to determine how to obtain the better interaction layer characteristics with the lesser modifications to the fabrication process and the smaller amount of Si in the matrix. In this work results for miniplates made of atomized U-7 wt%Mo particles dispersed in Al-2 wt%Si and Al-4 wt%Si matrices, obtained by mixing pure Al and Si powders, and Al 6061 as cladding are presented. Interaction layer grown during fabrication process (500 °C) consists of Si-containing phases being U(Al, Si)3 its principal component. Its uniformity is not satisfactory due to the formation of an oxide layer.

  1. X-ray Microtomography Analysis of the Aluminum Alloy Composite Reinforced by SiC After Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Wójcicka, Anna; Mroczka, Krzysztof; Kurtyka, Paweł; Binkowski, Marcin; Wróbel, Zygmunt

    2014-09-01

    Despite many years of using friction stir processing (FSP), there are many unexplained aspects concerning the processes which appear during FSP: determining the direction of flow and mixing of the materials and the degree of mixing and microstructure fragmentation in specific areas. This paper presents the impact of FSP on the micro- and macrostructure of the composite with hypo-eutectic Si matrix reinforced by SiC particles. The analysis of the structure of the processed area in FSP in the relation to the microstructure of the base material has been made using x-ray microtomography. The results of these studies have been juxtaposed with studies using microscopic methods (light microscopy and SEM). The microtomography images revealed an additional separation on the advancing side and the weld nugget, where on the basis of a 3D reconstruction a layer microstructure on the direction of linear movement of the tool has been demonstrated. The analyses have revealed a limited flow of the material above the weld nugget. The main advantages of the research method applied were the possibility to show the invisible or barely visible elements of the microstructure using standard test methods and the ability to analyze the microstructure changes uninterruptedly in different directions in the volume of the material.

  2. Recycling of Al-Si die casting scraps for solar Si feedstock

    NASA Astrophysics Data System (ADS)

    Seo, Kum-Hee; Jeon, Je-Beom; Youn, Ji-Won; Kim, Suk Jun; Kim, Ki-Young

    2016-05-01

    Recycling of aluminum die-casting scraps for solar-grade silicon (SOG-Si) feedstock was performed successfully. 3 N purity Si was extracted from A383 die-casting scrap by using the combined process of solvent refining and an advanced centrifugal separation technique. The efficiency of separating Si from scrap alloys depended on both impurity level of scraps and the starting temperature of centrifugation. Impurities in melt and processing temperature governed the microstructure of the primary Si. The purity of Si extracted from the scrap melt was 99.963%, which was comparable to that of Si extracted from a commercial Al-30 wt% Si alloy, 99.980%. The initial purity of the scrap was 2.2% lower than that of the commercial alloy. This result confirmed that die-casting scrap is a potential source of high-purity Si for solar cells.

  3. Hydrogenation properties of Li{sub x}Sr{sub 1−x}AlSi studied by quantum-chemical methods (0≤x≤1) and in-situ neutron powder diffraction (x=1)

    SciTech Connect

    Kunkel, Nathalie; Reichert, Christian; Springborg, Michael; Wallacher, Dirk; Kohlmann, Holger

    2015-01-15

    In-situ neutron powder diffraction studies of the Half-Heusler phase LiAlSi under high deuterium pressures and first principle calculations of solid solutions of Li{sub x}Sr{sub 1−x}AlSi and their hydrides Li{sub x}Sr{sub 1−x}AlSiH were carried out. In contrast to an earlier study, there is no experimental evidence for hydrogen (deuterium) uptake up to gas pressures of 15 MPa and temperatures of 550 °C. Instead a slow decomposition reaction according to LiAlSi+1/2H{sub 2}=LiH+Al+Si was found by in-situ neutron powder diffraction. Theoretical calculations by DFT methods on hypothetical solid solutions of Li{sub x}Sr{sub 1−x}AlSi show the LiAlSi type to be the energetically most stable structure for 0.7AlSi type structure for lower values of x. Hydrides Li{sub x}Sr{sub 1−x}AlSiH favor the SrAlSiH type for all values of x instead of the structure proposed earlier with hydrogen occupying tetrahedral voids in a LiAlSi structure. As an alternative for a cubic structure for LiAlSiH, we suggest the existence of LiAlSiH in the trigonal SrAlSiH type structure and it might be a candidate worthwhile to be considered for preparative work. - Graphical abstract: In-situ neutron powder diffraction of LiAlSi under high D{sub 2} pressure. - Highlights: • In-situ neutron powder diffraction of LiAlSi under high D{sub 2} pressure was carried out. • LiAlSi decomposes according to LiAlSi + ½ H{sub 2} = LiH + Al + Si. • Mixed crystals Li{sub x}Sr{sub 1-x}AlSi and LixSr{sub 1-x}AlSiH were studied theoretically.

  4. Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

    SciTech Connect

    Jain, Vivek Kumar Jain, Vishal Lakshmi, N. Venugopalan, K.

    2014-04-24

    Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

  5. Structure-phase states evolution in Al-Si alloy under electron-beam treatment and high-cycle fatigue

    SciTech Connect

    Konovalov, Sergey Alsaraeva, Krestina Gromov, Victor Semina, Olga; Ivanov, Yurii

    2015-10-27

    By methods of scanning and transmission electron diffraction microscopy the analysis of structure-phase states and defect substructure of silumin subjected to high-intensity electron beam irradiation in various regimes and subsequent fatigue loading up to failure was carried out. It is revealed that the sources of fatigue microcracks are silicon plates of micron and submicron size are not soluble in electron beam processing. The possible reasons of the silumin fatigue life increase under electron-beam treatment are discussed.

  6. Industrial Application of Ultrasonic Vibrations to Improve the Structure of Al-Si Hypereutectic Alloys: Potential and Limitations

    NASA Astrophysics Data System (ADS)

    Komarov, Segrey; Ishiwata, Yasuo; Mikhailov, Ivan

    2015-07-01

    This work presents the results of research conducted by the authors over the past years in Nippon Light Metal Co., ltd. In the first stage, highly durable ceramic sonotrodes were designed and manufactured to introduce ultrasonic vibrations into molten metal in a launder or in a hot top during DC casting. It was shown that ultrasound can greatly refine the crystals of primary silicon in 75 to 178-mm billets, if vibration amplitude exceeds 40 μm (p-p). The structure uniformity was insufficient in launder treatment and fairly good in hot-top treatment. Care must be taken in controlling the passage of melt through the cavitation zone in order to fully exploit the refining potential of ultrasonic vibrations. The results suggest that if the treatment conditions are controlled properly, up to 20 kg/min of molten metal can be effectively treated using a 2-kW ultrasonic installation equipped with one ceramic sonotrode of 40 to 60 mm in diameter.

  7. A Study on the Laser Spatter and the Oxidation Reactions During Selective Laser Melting of 316L Stainless Steel, Al-Si10-Mg, and Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Simonelli, Marco; Tuck, Chris; Aboulkhair, Nesma T.; Maskery, Ian; Ashcroft, Ian; Wildman, Ricky D.; Hague, Richard

    2015-09-01

    The creation of an object by selective laser melting (SLM) occurs by melting contiguous areas of a powder bed according to a corresponding digital model. It is therefore clear that the success of this metal Additive Manufacturing (AM) technology relies on the comprehension of the events that take place during the melting and solidification of the powder bed. This study was designed to understand the generation of the laser spatter that is commonly observed during SLM and the potential effects that the spatter has on the processing of 316L stainless steel, Al-Si10-Mg, and Ti-6Al-4V. With the exception of Ti-6Al-4V, the characterization of the laser spatter revealed the presence of surface oxides enriched in the most volatile alloying elements of the materials. The study will discuss the implication of this finding on the material quality of the built parts.

  8. Structure, tribological and electrochemical properties of low friction TiAlSiCN/MoSeC coatings

    NASA Astrophysics Data System (ADS)

    Bondarev, A. V.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Shtansky, D. V.

    2015-02-01

    The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe2 and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al2O3 and WC-Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25-400 °C against Al2O3 counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1 N H2SO4 solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12 GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60 ± 5%) from 0.8-0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on counterpart material. This was attributed to the presence of MoSe2 and free carbon-based phases in the tribological contact. The TiAlSiCN/MoSeC coating with a maximal amount of MoSeC also demonstrated superior tribological characteristics in distilled water (CoF ∼ 0.1) and at moderate temperatures up to 300 °C (CoF < 0.1). The electrochemical tests showed that, in general, doping with MoSeC did not negatively affect the coating electrochemical behavior. On the contrary, the Mo

  9. A planar Al-Si Schottky barrier metal–oxide–semiconductor field effect transistor operated at cryogenic temperatures

    SciTech Connect

    Purches, W. E.; Rossi, A.; Zhao, R.; Kafanov, S.; Duty, T. L.; Dzurak, A. S.; Rogge, S.; Tettamanzi, G. C.

    2015-08-10

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  10. A planar Al-Si Schottky barrier metal-oxide-semiconductor field effect transistor operated at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Purches, W. E.; Rossi, A.; Zhao, R.; Kafanov, S.; Duty, T. L.; Dzurak, A. S.; Rogge, S.; Tettamanzi, G. C.

    2015-08-01

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  11. Sr effect on the microstructure and tensile properties of A357 aluminum alloy and Al{sub 2}O{sub 3}/SiC-A357 cast composites

    SciTech Connect

    Razaghian, A.; Emamy, M.; Najimi, A.A.; Ebrahimi, S.H. Seyed

    2009-11-15

    The effect of strontium as a modifier on the microstructures and tensile properties of two castable particulate metal matrix composites has been studied. The particulate metal matrix composites had similar matrix alloy (A357) but different reinforcing fine particles (silicon carbide and alumina). Results showed that the addition of 0.03% strontium makes a modest improvement to the yield strength, ultimate tensile strength and elongation percentage values, and the scatter of these properties, but makes a significant improvement to minimum strength and elongation results. Microstructural examinations by scanning electron microscope and energy dispersive spectroscopy analysis of metal matrix composites showed segregation of strontium on both the silicon carbide and alumina particles. Further results showed that the addition of higher strontium levels contributes to the over-modification of the eutectic silicon and promotes the formation of an Al-Si-Sr intermetallic compound on the particle/matrix interface.

  12. New insights on pressure, temperature, and chemical stability of CsAlSi5O12, a potential host for nuclear waste

    NASA Astrophysics Data System (ADS)

    Gatta, G. D.; Brundu, A.; Cappelletti, P.; Cerri, G.; de'Gennaro, B.; Farina, M.; Fumagalli, P.; Guaschino, L.; Lotti, P.; Mercurio, M.

    2016-06-01

    A Cs-bearing polyphase aggregate with composition (in wt%): 76(1)CsAlSi5O12 + 7(1)CsAlSi2O6 + 17(1)amorphous, was obtained from a clinoptilolite-rich epiclastic rock after a beneficiation process of the starting material (aimed to increase the fraction of zeolite to 90 wt%), cation exchange and then thermal treatment. CsAlSi5O12 is an open-framework compound with CAS topology; CsAlSi2O6 is a pollucite-like material with ANA topology. The thermal stability of this polyphase material was investigated by in situ high-T X-ray powder diffraction, the combined P-T effects by a series of runs with a single-stage piston cylinder apparatus, and its chemical stability following the "availability test" ("AVA test") protocol. A series of additional investigations were performed by WDS-electron microprobe analysis in order to describe the P-T-induced modification of the material texture, and to chemically characterize the starting material and the run products. The "AVA tests" of the polyphase aggregate show an extremely modest release of Cs+: 0.05 mg/g. In response to applied temperature and at room P, CsAlSi5O12 experiences an unquenchable and displacive Ama2-to-Amam phase transition at about 770 K, and the Amam polymorph is stable in its crystalline form up to 1600 K; a crystalline-to-amorphous phase transition occurs between 1600 and 1650 K. In response to the applied P = 0.5 GPa, the crystalline-to-amorphous transition of CsAlSi5O12 occurs between 1670 and 1770 K. This leads to a positive Clapeyron slope (i.e., dP/dT > 0) of the crystalline-to-amorphous transition. When the polyphase aggregate is subjected at P = 0.5 GPa and T > 1770 K, CsAlSi5O12 melts and only CsAlSi2O6 (pollucite-like; dominant) and Cs-rich glass (subordinate) are observed in the quenched sample. Based on its thermo-elastic behavior, P-T phase stability fields, and Cs+ retention capacity, CsAlSi5O12 is a possible candidate for use in the immobilization of radioactive isotopes of Cs, or as potential

  13. Three-Dimensional Microstructure Visualization of Porosity and Fe-Rich Inclusions in SiC Particle-Reinforced Al Alloy Matrix Composites by X-Ray Synchrotron Tomography

    SciTech Connect

    Silva, Flávio de Andrade; Williams, Jason J.; Müller, Bernd R.; Hentschel, Manfred P.; Portella, Pedro D.; Chawla, Nikhilesh

    2011-11-15

    Microstructural aspects of composites such as reinforcement particle size, shape, and distribution play important roles in deformation behavior. In addition, Fe-rich inclusions and porosity also influence the behavior of these composites, particularly under fatigue loading. Three-dimensional (3-D) visualization of porosity and Fe-rich inclusions in three dimensions is critical to a thorough understanding of fatigue resistance of metal matrix composites (MMCs), because cracks often initiate at these defects. In this article, we have used X-ray synchrotron tomography to visualize and quantify the morphology and size distribution of pores and Fe-rich inclusions in a SiC particle-reinforced 2080 Al alloy composite. The 3-D data sets were also used to predict and understand the influence of defects on the deformation behavior by 3-D finite element modeling.

  14. Excimer Laser Surface Treatment Of Non-Ferrous Alloys

    NASA Astrophysics Data System (ADS)

    Georgiopoulos, Michael; Hontzopoulos, Elias I.; Fotakis, Costas; Tsipas, D. N.; Floros, T.

    1989-04-01

    Excimer laser (KrF, ArF) radiation has been used for the surface modification of Al - Si and Ni alloys with the aim to improve their corrosion-errosion and hardness properties. A variety of experimental techniques including direct laser surface treatment and laser assisted chemical vapour deposition (CVD) have been employed and the parameters for process optimization have been determined.

  15. Shock-induced transformations in the system NaAlSiO4-SiO2 - A new interpretation

    NASA Technical Reports Server (NTRS)

    Sekine, Toshimori; Ahrens, Thomas J.

    1992-01-01

    New internally consistent interpretations of the phases represented by the high pressure phase shock wave data for an albite-rich rock, jadeite, and nepheline in the system NaAlSiO4-SiO2, are obtained using the results of static high pressure investigations, and the recent discovery of the hollandite phase in a shocked meteorite. We conclude that nepheline transforms directly to the calcium ferrite structure, whereas albite transforms possibly to the hollandite structure. Shock Hugoniots for the other plagioclase and alkali feldspars also indicate that these transform to hollandite structures. The pressure-volume data at high pressure could alternatively represent the compression of an amorphous phase. Moreover, the shock Hugoniot data are expected to reflect the properties of the melt above shock stresses of 60-80 GPa. The third order Birch-Murnaghan equation of state parameters are given for the calcium ferrite type NaAlSiO4 and for albite-rich, orthoclase-rich, and anorthite-rich hollandites.

  16. The microstructure and electrical properties of contacts formed in the Ni/Al/Si system due to rapid thermal processing

    NASA Astrophysics Data System (ADS)

    Katz, A.; Komem, Y.

    1988-06-01

    The microstructure and electrical properties of the contacts formed in the Ni(30 nm)/Al(10 nm)/100-line n-Si system due to rapid thermal processing were studied at temperatures between 300 and 900 C. A melting at the intermediate Al layer was observed already at about 580 C after 2-s heat treatments. This rapid eutectic melting, assumed to initiate at the Al-Si interface, resulted in the formation of a unique contact composed of the Ni(Al/0.5/Si/0.5/)/Al3Ni/Ni(x)Si(y)/n-Si structure with fairly smooth interfaces between the layers. The sheet resistance of the layers and the Schottky barrier height of the contact were measured as a function of the rapid thermal processing temperatures. As a result of the eutectic melting reaction at 580 C, the sheet resistance of the formed layers decreased from 3.2 to 2.6 ohm/unit area, the Schottky barrier height between the layers and Si increased from 0.61-0.76 eV, and the effective electrically active area of the contact increased. These electrical properties are discussed in correlation with the microstructure formed in the Ni/Al/Si system due to the rapid thermal processing.

  17. Effect of water absorption of dielectric underlayers on crystal orientation in Al-Si-Cu/Ti/TiN/Ti metallization

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Hosokawa, Hideki; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1997-05-01

    The influence of the exposure of underlying dielectric (phophosilicate glass and borophosphosilicate glass) films to a humid air ambient on crystallographic orientations in Al-Si-Cu/Ti/TiN/Ti layered structures has been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered structures was found to improve drastically with increasing boron content and exposure time of the dielectric films. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and the average grain size increases as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. The mechanism of the improved Ti(002) orientation was investigated. It was confirmed that the improved orientation is closely related with the surface concentration of the absorbed water in the dielectric films. Further, it was demonstrated that interconnects fabricated from the improved layered structure have excellent electromigration performance.

  18. Preparation of CNT/AlSi10Mg composite powders by high-energy ball milling and their physical properties

    NASA Astrophysics Data System (ADS)

    Wang, Lin-zhi; Liu, Ying; Wei, Wen-hou; An, Xu-guang; Zhang, Tao; Pu, Ya-yun

    2016-03-01

    This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption properties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanning electron microscope, X-ray diffractometer, laser particle size analyzer, high-temperature synchronous thermal analyzer, and UV/VIS/NIR spectrophotometer were used for the analysis of micrographs, phases, granulometric parameters, thermal properties, and laser absorption properties of the composite powders, respectively. The results showed that the powders gradually changed from flake- to granule-like morphology and the average particle size sharply decreased with increases in milling rotational speed and milling time. Moreover, a uniform dispersion of CNTs in AlSi10Mg powders was achieved only for a CNT content of 1.5wt%. Laser absorption values of the composite powders were also observed to gradually increase with the increase of CNT concentration, and different spectra displayed characteristic absorption peaks at a wavelength of approximately 826 nm.

  19. Nanostructured composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  20. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    SciTech Connect

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues for investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.

  1. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    DOE PAGESBeta

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues formore » investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.« less

  2. Effect of Different Al/Si Ratios on the Structure and Energy Storage Properties of Strontium Barium Niobate-Based Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Xiu, Shaomei; Xiao, Shi; Xue, Shuangxi; Shen, Bo; Zhai, Jiwei

    2016-02-01

    Strontium barium niobate-based glass-ceramics (BSN-AS) with various Al/Si ratios have been prepared through melt casting followed by controlled crystallization. The effect of the various Al/Si ratios on the phase evolution, microstructure, dielectric properties, and energy storage density, and the relationship between the breakdown strength properties and the activation energy E a of BSN-AS glass-ceramics, were investigated. The results reveal that the microstructure of BSN-AS glass-ceramics gradually becomes dense and uniform, and the phenomenon of reunited grains is effectively improved in a certain range of Al/Si ratios. With the Al/Si ratios increasing, the breakdown strength increases to a maximum value and then decreases drastically. For the relationship between breakdown strength properties and activation energy E a, it was found that the various trends between breakdown properties and activation energy E a of the BSN-AS glass-ceramics are opposite. In this study, the energy storage densities reach 4.8 J/cm3 by adjusting the Al/Si ratios in the BSN-AS glass-ceramics.

  3. Influence of high temperature annealing on the structure, hardness and tribological properties of diamond-like carbon and TiAlSiCN nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Xie, Z. W.; Wang, L. P.; Wang, X. F.; Huang, L.; Lu, Y.; Yan, J. C.

    2011-11-01

    Diamond-like carbon (DLC) and TiAlSiCN nanocomposite coatings were synthesized and annealed at different temperatures in a vacuum environment. The microstructure, hardness and tribological properties of as-deposited and annealed DLC-TiAlSiCN nanocomposite coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, nano-indentation and friction tests. The TEM results reveal that the as-deposited DLC-TiAlSiCN coating has a unique nanocomposite structure consisting of TiCN nanocrystals embedded in an amorphous matrix consisting of a-Si3N4, a-SiC, a-CN and DLC, and the structure changed little after annealing at 800 °C. However, XPS and Raman results show that an obvious graphitization of the DLC phase occurred during the annealing process and it worsened with annealing temperature. Because of the graphitization, the hardness of the DLC-TiAlSiCN coating after annealing at 800 °C decreased from 45 to 36 GPa. In addition, the DLC-TiAlSiCN coating after annealing at 800 °C has a similar friction coefficient to the as-deposited coating.

  4. Experimental and analytical investigation of the seizure process in aluminum-silicon alloy/steel tribocontacts

    NASA Astrophysics Data System (ADS)

    He, Xiaozhou

    1998-12-01

    This research is an experimental and analytical investigation of the scuffing/seizure mechanism in Al-Si alloy/steel tribocontacts. An analytical model is developed based on analyses and experiments to predict scuffing/seizure failure in Al-Si alloy/steel tribocontacts, which can be applied to tribo-components in engines, refrigerators and air conditioners. The wear and scuffing/seizure experiments have been conducted through a block-on-ring tester for 339 and ESE-M2A137 Al-Si alloys under the dry and boundary lubrication conditions. The experimental research consists of: (a) wear debris generation and EDX analysis, (b) wear surface morphological analysis, (c) scuffing/seizure mechanism and process analysis, (d) scuffing/seizure PV curves under the dry contact and boundary lubrication, and (e) effects of several main factors on scuffing/seizure. The analytical research includes the following: (a) the investigation of the scuffing/seizure mechanisms in the Al-Si alloy/steel tribocontacts, (b) 3-D asperity contact pressures for longitudinal, transverse and isotropic surface roughness profiles, (c) 3-D surface asperity contact temperature rise due to the friction, (d) failure analyses of the various lubricating films, (e) analyses of the temperature dependence of surface tangential traction and shear strength in a surface layer of Al-Si alloy, (f) the scuffing/seizure failure analytical model under dry contact and boundary lubrication. The analytical model is based on the new hypothesis of three defense lines against scuffing/seizure failure: the adsorbed oil film, oxide film and the ratio of surface tangential traction with the shear strength in a surface layer. These two films together with a surface layer itself form three defense lines against scuffing/seizure. The surface tangential traction exceeds the bulk shear strength in a surface layer of Al-Si alloy is the necessary and sufficient condition for the scuffing/seizure occurrence. The analytical model has a

  5. Formation of nanostructured weldments in the Al-Si system using electrospark welding

    NASA Astrophysics Data System (ADS)

    Milligan, J.; Heard, D. W.; Brochu, M.

    2010-04-01

    Electrospark welding (ESW) electrodes were manufactured from three binary aluminum-silicon alloys consisting of 12 and 17 wt% silicon, produced using chill and sand casting. The electrodes were used to assess the feasibility of producing aluminum-silicon weldments consisting of nano-sized silicon particles embedded in nanostructured aluminum matrix, using the ESW process. Line tests were performed to determine the optimal processing parameters resulting in a high quality deposit. X-ray diffraction (XRD) as well as optical and field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) was performed to determine the composition and microstructure of the depositions. It was determined that a capacitance of 110 μF and a voltage of 100 V resulted in the highest quality deposition. Furthermore it was determined that the ESW process was capable of producing a microstructure consisting of an extremely fine-grained silicon phase ranging from ˜6 to 50 nm for the eutectic composition, and 10-200 nm for the hypereutectic compositions. Finally it was determined that the functional thickness limit of the aluminum-silicon deposit produced under these process parameters was 120 μm.

  6. Global Mg/Si and Al/Si Distributions on the Lunar Surface Derived from Chang'E-2 X-ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Dong, Wu-Dong; Zhang, Xiao-Ping; Zhu, Meng-Hua; Xu, Ao-Ao; Tang, Ze-Sheng

    2016-01-01

    The technique of X-ray fluorescence remote sensing plays a significant role in research related to the chemical compositions of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectrometer in detail and present the preliminary results about the first global Mg/Si and Al/Si maps of the lunar surface. Our results show that the distributions of Mg/Si and Al/Si correlate well with terrains on the Moon. The higher Mg/Si ratio corresponds to the mare regions while the lower value corresponds to the highland terrains. The map of the Al/Si ratio shows a reversed distribution compared with the map of the Mg/Si ratio.

  7. Effective work function engineering for a TiN/XO(X = La, Zr, Al)/SiO2 stack structures

    NASA Astrophysics Data System (ADS)

    Lee, Dongjin; Cho, Eunae; Lee, Jieun; Jung, Kyoungho; Jeong, Moonyoung; Yamada, Satoru; Hong, Hyeongsun; Lee, Kyupil; Heo, Sung; Ko, Dongsu; Kim, Yong Su; Kyoung, Yong Koo; Lee, Hyung-Ik; Lee, Hyo Sug; Park, Gyeong-Su; Shin, Jai Kwang

    2016-05-01

    In this study, we demonstrated that work function engineering is possible over a wide range (+200 mV to -430 mV) in a TiN/XO (X = La, Zr, or Al)/SiO2 stack structures. From ab initio simulations, we selected the optimal material for the work function engineering. The work function engineering mechanism was described by metal diffusion into the TiN film and silicate formation in the TiN/SiO2 interface. The metal doping and the silicate formation were confirmed by transmission electron microscopy and energy dispersive spectroscopy line profiling, respectively. In addition, the amount of doped metal in the TiN film depended on the thickness of the insertion layer XO. From the work function engineering technique, which can control a variety of threshold voltages (Vth), an improvement in transistors with different Vth values in the TiN/XO/SiO2 stack structures is expected.

  8. Tuning electronic and magnetic properties of blue phosphorene by doping Al, Si, As and Sb atom: A DFT calculation

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Hao, Yitong; Ren, Qingqiang; Zhao, Yiming; Du, Yanhui; Tang, Wencheng

    2016-09-01

    Using density functional theory computations, we systematically investigated the structural, electronic and magnetic properties of Al, Si, As and Sb doped blue phosphorene. The electronic properties of blue phosphorene can be effectively turned by substitutional doping. Especially, Al and Sb lead to an indirect-to-direct-gap transition. The interaction between the impurity and P atoms should be responsible for the transition. In addition, blue phosphorene can exhibit dilute magnetic semiconductor property with doping of Si impurity. The magnetic moment in Si-substituted blue phosphorene predominantly originates from the hybridization of Si-s pz and P-pz orbitals. These results provide many useful applications of blue phosphorene in electronics, optoelectronics and spintronics.

  9. Annealing tests of in-pile irradiated oxide coated U-Mo/Al-Si dispersed nuclear fuel

    NASA Astrophysics Data System (ADS)

    Zweifel, T.; Valot, Ch.; Pontillon, Y.; Lamontagne, J.; Vermersch, A.; Barrallier, L.; Blay, T.; Petry, W.; Palancher, H.

    2014-09-01

    U-Mo/Al based nuclear fuels have been worldwide considered as a promising high density fuel for the conversion of high flux research reactors from highly enriched uranium to lower enrichment. In this paper, we present the annealing test up to 1800 °C of in-pile irradiated U-Mo/Al-Si fuel plate samples. More than 70% of the fission gases (FGs) are released during two major FG release peaks around 500 °C and 670 °C. Additional characterisations of the samples by XRD, EPMA and SEM suggest that up to 500 °C FGs are released from IDL/matrix interfaces. The second peak at 670 °C representing the main release of FGs originates from the interaction between U-Mo and matrix in the vicinity of the cladding.

  10. Theoretical investigation of superconductivity in ternary silicide NaAlSi with layered diamond-like structure

    NASA Astrophysics Data System (ADS)

    Tütüncü, H. M.; Karaca, Ertuǧrul; Srivastava, G. P.

    2016-04-01

    We have investigated the electronic structure, phonon modes and electron-phonon coupling to understand superconductivity in the ternary silicide NaAlSi with a layered diamond-like structure. Our electronic results, using the density functional theory within a generalized gradient approximation, indicate that the density of states at the Fermi level is mainly governed by Si p states. The largest contributions to the electron-phonon coupling parameter involve Si-related vibrations both in the x-y plane as well as along the z-axis in the x-z plane. Our results indicate that this material is an s-p electron superconductor with a medium level electron-phonon coupling parameter of 0.68. Using the Allen-Dynes modification of the McMillan formula we obtain the superconducting critical temperature of 6.98 K, in excellent agreement with experimentally determined value of 7 K.

  11. Temperature-dependent structural study of microporous CsAlSi{sub 5}O{sub 12}

    SciTech Connect

    Fisch, Martin; Armbruster, Thomas Kolesov, Boris

    2008-03-15

    CsAlSi{sub 5}O{sub 12} crystals were synthesized at high temperature by slow cooling of a vanadium oxide flux. Single-crystal X-ray diffraction structure analysis and electron microprobe analyses yielded the microporous CAS zeolite framework structure of Cs{sub 0.85}Al{sub 0.85}Si{sub 5.15}O{sub 12} composition. High-temperature single-crystal and powder X-ray diffraction studies were utilized to analyze anisotropic thermal expansion. Rietveld refined cell constants from powder diffraction data, measured in steps of 25 deg. C up to 700 deg. C, show a significant decrease in expansion above 500 deg. C. At 500 deg. C, a displacive, static disorder-dynamic disorder-type phase transition from the acentric low-temperature space group Ama2 to centrosymmetric Amam (Cmcm in standard setting) was found. Thermal expansion below the phase transition is governed by rigid-body TO{sub 4} rotations accompanied by stretching of T-O-T angles. Above the phase transition at 500 deg. C all atoms, except one oxygen (O6), are fixed on mirror planes. Temperature-dependent polarized Raman single-crystal spectra between -270 and 300 deg. C and unpolarized spectra between room temperature and 1000 deg. C become increasingly less resolved with rising temperature confirming the disordered static-disordered dynamic type of the phase transition. - Graphical abstract: Temperature-dependent structural evolution of microporous CsAlSi{sub 5}O{sub 12} has been investigated by single-crystal and powder X-ray diffraction, as well as Raman spectroscopy. Results yielded a phase transition of order-disorder type.

  12. Lunar Resources Using Moderate Spectral Resolution Visible and Near-infrared Spectroscopy: Al/si and Soil Maturity

    NASA Technical Reports Server (NTRS)

    Fischer, Erich M.; Pieters, Carle M.; Head, James W.

    1992-01-01

    Modern visible and near-infrared detectors are critically important for the accurate identification and relative abundance measurement of lunar minerals; however, even a very small number of well-placed visible and near-infrared bandpass channels provide a significant amount of general information about crucial lunar resources. The Galileo Solid State Imaging system (SSI) multispectral data are an important example of this. Al/Si and soil maturity will be discussed as examples of significant general lunar resource information that can be gleaned from moderate spectral resolution visible and near-infrared data with relative ease. Because quantitative-albedo data are necessary for these kinds of analyses, data such as those obtained by Galileo SSI are critical. SSI obtained synoptic digital multispectral image data for both the nearside and farside of the Moon during the first Galileo Earth-Moon encounter in December 1990. The data consist of images through seven filters with bandpasses ranging from 0.40 microns in the ultraviolet to 0.99 microns in the near-infrared. Although these data are of moderate spectral resolution, they still provide information for the following lunar resources: (1) titanium content of mature mare soils based upon the 0.40/0.56-micron (UV/VIS) ratio; (2) mafic mineral abundance based upon the 0.76/0.99-micron ratio; and (3) the maturity or exposure age of the soils based upon the 0.56-0.76-micron continuum and the 0.76/0.99-micron ratio. Within constraints, these moderate spectral resolution visible and near-infrared reflectance data can also provide elemental information such as Al/Si for mature highland soils.

  13. Marangoni motion during melting of a hypermonotectic alloy: Numerical simulations for the D2 experiment IHF04

    NASA Astrophysics Data System (ADS)

    Ratke, L.; Diefenbach, S.; Prinz, B.; Ahlborn, H.; Feuerbacher, Berndt

    1992-08-01

    The scientific objectives, experimental procedure, numerical simulation, and expected results of the D2 experiment IHF-04, in which the Marangoni transport of Bi droplets in an Al-Si melt will be investigated by directional melting of sandwich like samples of Al-Si-Bi alloys, are addressed. The sandwich like samples consist of periodically arranged cylinders of an Al-Si alloy in which 5 wt percent Bi are distributed as droplets and cylinders of an Al-Si-Bi alloy of exact monotectic composition and being thus free of Bi droplets at the processing temperature. Ahead of the melting front there exists a temperature gradient which leads to a motion of the droplets within the Al-Si matrix melt. Bi droplets move from the cylinder with hypermonotectic composition into the droplets free one as soon as the melting front moves into it in a controlled way. At the end of an experiment a large number of droplets will be located within the molten zone. From the spatial arrangement of the droplets and a comparison with computer simulations of the whole process, conclusions are drawn concerning the Marangoni motion of Bi droplets. The investigations are relevant for the improvement of terrestrial industrial casting processes of bearing alloys.

  14. Crystal Growth, Structure, and Physical Properties of LnCu[subscript 2](Al,Si)[subscript 5] (Ln = La and Ce)

    SciTech Connect

    Phelan, W. Adam; Kangas, Michael J.; Drake, Brenton L.; Zhao, Liang L.; Wang, Jiakui K.; DiTusa, J.F.; Morosan, Emilia; Chan, Julia Y.

    2012-03-15

    LnCu{sub 2}(Al,Si){sub 5} (Ln = La and Ce) were synthesized and characterized. These compounds adopt the SrAu{sub 2}Ga{sub 5} structure type and crystallize in the tetragonal space group P4/mmm with unit cell dimensions of a {approx} 4.2 {angstrom} and c {approx} 7.9 {angstrom}. Herein, we report the structure as obtained from single crystal X-ray diffraction. Additionally, we report the magnetic susceptibility, magnetization, resistivity, and specific heat capacity data obtained for polycrystalline samples of LnCu{sub 2}(Al,Si){sub 5} (Ln = La and Ce).

  15. A declaration of independence for Mg/Si. [Al/Si intensity ratio predictive usefulness for Mg/Si intensity ratio in lunar X-ray fluorescence

    NASA Technical Reports Server (NTRS)

    Hubbard, N.; Keith, J. E.

    1978-01-01

    The weak covariation that exists between Al/Si and Mg/Si for large areas of the lunar surface is little, if any, stronger than that forced on a random set of numbers that are subject to closure. The Mg and Al variations implied by the Mg/Si and Al/Si intensity ratio data are qualitatively like those seen in lunar soil sample data. Two petrogenetic provinces are suggested for terra materials; one appears to have 50% higher Mg values than the other. Using the improved data, Mg/Si variations can be studied at a signal-to-noise ratio greater than 5/1.

  16. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    PubMed

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited. PMID:27451619

  17. Theoretical elastic moduli of ferromagnetic bcc Fe alloys.

    PubMed

    Zhang, Hualei; Punkkinen, Marko P J; Johansson, Börje; Vitos, Levente

    2010-07-14

    The polycrystalline elastic parameters of ferromagnetic Fe(1-x)M(x) (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 ≤ x ≤ 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calculated and the available experimental data for the polycrystalline aggregates is satisfactory. All additions considered here decrease the bulk modulus (B) and Poisson's ratio (ν) of bcc Fe. The complex composition dependence of the C(44) single-crystal elastic constant is reflected in the polycrystalline shear modulus (G), Young's modulus (E), and Debye temperature (Θ). The polycrystalline anisotropy of bcc Fe is increased by all additions, and Al, Si, Ni, and Rh yield the largest alloying effects. PMID:21399255

  18. EBSD Study of the Influence of a High Magnetic Field on the Microstructure and Orientation of the Al-Si Eutectic During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-03-01

    The effect of a high magnetic field on the morphology of the Al-Si eutectic was investigated using EBSD technology. The results revealed that the application of the magnetic field modified the morphology of the Al-Si eutectic significantly. Indeed, the magnetic field destroyed the coupled growth of the Al-Si eutectic and caused the formation of the divorced α-Al and Si dendrites at low growth speeds (≤1 μm/s). The magnetic field was also found to refine the eutectic grains and reduce the eutectic spacing at the initial growth stage. Moreover, the magnetic field caused the occurrence of the columnar-to-equiaxed transition of the α-Al phase in the Al-Si eutectic. The abovementioned effects were enhanced as the magnetic field increased. This result should be attributed to the magnetic field restraining the interdiffusion of Si and Al atoms in liquid ahead of the liquid/solid interface and the thermoelectric magnetic force acting on the eutectic lamellae under the magnetic field.

  19. Li3AlSiO5: the first aluminosilicate as a potential deep-ultraviolet nonlinear optical crystal with the quaternary diamond-like structure.

    PubMed

    Chen, Xinglong; Zhang, Fangfang; Liu, Lili; Lei, Bing-Hua; Dong, Xiaoyu; Yang, Zhihua; Li, Hongyi; Pan, Shilie

    2016-02-14

    Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals play a crucial role in modern laser frequency conversion technology. Traditionally, the exploration of deep-UV NLO crystals is mainly focused on borates, while, the use of phosphates recently opened up a novel and promising non-boron pathway for designing new deep-UV NLO crystals. Extending this pathway to aluminosilicates led to the discovery of Li3AlSiO5, the first NLO crystal in this system. It crystallizes in the polar space group Pna21 (no. 33) with a quaternary diamond-like structure composed of LiO4, AlO4 and SiO4 tetrahedral groups. The compound exhibits a deep-UV cut-off edge below 190 nm and is phase matchable with moderate powder second harmonic generation (SHG) intensity (0.8KH2PO4). The band gap calculated using PBE0 is 7.29 eV, indicating that the cut-off edge of the Li3AlSiO5 crystal can be down to 170 nm. In addition, the compound is nonhygroscopic and thermally stable up to ∼1472 K. These results suggest that Li3AlSiO5 is a potential deep-UV NLO crystal. First-principles studies were performed to elucidate the structure-property relationship of Li3AlSiO5. PMID:26788988

  20. EBSD Study of the Influence of a High Magnetic Field on the Microstructure and Orientation of the Al-Si Eutectic During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-06-01

    The effect of a high magnetic field on the morphology of the Al-Si eutectic was investigated using EBSD technology. The results revealed that the application of the magnetic field modified the morphology of the Al-Si eutectic significantly. Indeed, the magnetic field destroyed the coupled growth of the Al-Si eutectic and caused the formation of the divorced α-Al and Si dendrites at low growth speeds (≤1 μm/s). The magnetic field was also found to refine the eutectic grains and reduce the eutectic spacing at the initial growth stage. Moreover, the magnetic field caused the occurrence of the columnar-to-equiaxed transition of the α-Al phase in the Al-Si eutectic. The abovementioned effects were enhanced as the magnetic field increased. This result should be attributed to the magnetic field restraining the interdiffusion of Si and Al atoms in liquid ahead of the liquid/solid interface and the thermoelectric magnetic force acting on the eutectic lamellae under the magnetic field.

  1. Internally consistent thermodynamic data for aqueous species in the system Na-K-Al-Si-O-H-Cl

    NASA Astrophysics Data System (ADS)

    Miron, George D.; Wagner, Thomas; Kulik, Dmitrii A.; Heinrich, Christoph A.

    2016-08-01

    A large amount of critically evaluated experimental data on mineral solubility, covering the entire Na-K-Al-Si-O-H-Cl system over wide ranges in temperature and pressure, was used to simultaneously refine the standard state Gibbs energies of aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers equation of state. The thermodynamic properties of the solubility-controlling minerals were adopted from the internally consistent dataset of Holland and Powell (2002; Thermocalc dataset ds55). The global optimization of Gibbs energies of aqueous species, performed with the GEMSFITS code (Miron et al., 2015), was set up in such a way that the association equilibria for ion pairs and complexes, independently derived from conductance and potentiometric data, are always maintained. This was achieved by introducing reaction constraints into the parameter optimization that adjust Gibbs energies of complexes by their respective Gibbs energy effects of reaction, whenever the Gibbs energies of reactant species (ions) are changed. The optimized thermodynamic dataset is reported with confidence intervals for all parameters evaluated by Monte Carlo trial calculations. The new thermodynamic dataset is shown to reproduce all available fluid-mineral phase equilibria and mineral solubility data with good accuracy and precision over wide ranges in temperature (25-800 °C), pressure (1 bar to 5 kbar) and composition (salt concentrations up to 5 molal). The global data optimization process adopted in this study can be readily repeated any time when extensions to new chemical elements and species are needed, when new experimental data become available, or when a different aqueous activity model or equation of state should be used. This work serves as a proof of concept that our optimization strategy is feasible and successful in generating a thermodynamic dataset reproducing all fluid-mineral and aqueous speciation equilibria in the Na-K-Al-Si-O-H-Cl system within

  2. The stability of sodalite in the system NaAlSiO sub 4 -NaCl

    SciTech Connect

    Sharp, Z.D. ); Helffrich, G.R. ); Bohlen, S.R. ); Essene, E.J. )

    1989-08-01

    The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.

  3. The Effects of Individual Metal Contents on Isochrones for C, N, O, Na, Mg, Al, Si, and Fe

    NASA Astrophysics Data System (ADS)

    Beom, Minje; Na, Chongsam; Ferguson, Jason W.; Kim, Y.-C.

    2016-08-01

    The individual characteristics of C, N, O, Na, Mg, Al, Si, and Fe on isochrones have been investigated in this study. Stellar models have been constructed for various mixtures in which the content of each element is changed up to the extreme value reported in recent studies, and the changes in isochrone shape have been analyzed for the various mixtures. To express the abundance variation of different elements with a single parameter, we have focused on the relative changes in the total number of metal ions. A review of the shape changes revealed that Na, Mg, and Al work the same way in stellar models, similar to the well-known fact that C, N, and O have the same reactions in the stellar interior. In addition, it was found that in high-metallicity conditions the influence of Si and Fe on the red giant branch becomes smaller than that of Na, Mg, and Al closer to the tip. Furthermore, the influence of Fe on the main sequence is larger than that of Na, Mg, Al, and even Si.

  4. Identification of phases in the interaction layer between U-Mo-Zr/Al and U-Mo-Zr/Al-Si

    SciTech Connect

    Varela, C.L. Komar; Arico, S.F.; Mirandou, M.; Balart, S.N.; Gribaudo, L.M.

    2008-07-15

    Out-of-pile diffusion experiments were performed between U-7wt.% Mo-1wt.% Zr and Al or Al A356 (7,1wt.% Si) at 550 deg. C. In this work morphological characterization and phase identification on both interaction layer are presented. They were carried out by the use of different techniques: optical and scanning electron microscopy, X-Ray diffraction and WDS microanalysis. In the interaction layer U-7wt.% Mo-1wt.% Zr/Al, the phases UAl{sub 3}, UAl{sub 4}, Al{sub 20}Mo{sub 2}U and Al{sub 43}Mo{sub 4}U{sub 6} were identified. In the interaction layer U-7wt.% Mo-1wt.% Zr/Al A356, the phases U(Al, Si) with 25at.% Si and Si{sub 5}U{sub 3} were identified. This last phase, with a higher Si concentration, was identified with XRD Synchrotron radiation performed at the National Synchrotron Light Laboratory (LNLS), Campinas, Brasil. (author)

  5. Complex phase compositions in nanostructured coatings as evidenced by photoelectron spectroscopy: The case of Al-Si-N hard coatings

    NASA Astrophysics Data System (ADS)

    Pélisson-Schecker, Aude; Hug, Hans Josef; Patscheider, Jörg

    2010-07-01

    The chemical state evolution of the Al-Si-N thin films at various Si contents is investigated by x-ray photoelectron spectroscopy (XPS). The detailed evolution of the Al 2p, Si 2p, and N 1s photoelectrons line positions and widths are used to identify different chemical environments as the Si content is changed. The results are compared to x-ray diffraction (XRD) data that indicate the formation of a two-phase Al1-xSixN/SiNy composite when the solubility limit of 6 at. % of Si in AlN is exceeded. In contrast to XRD data, no particular effect is observed in the XPS data at the solubility limit of Si. Instead, two compositional regions can be identified that are separated by a distinct change in the evolution of core level binding energy differences and chemical shifts at about 10-15 at. % of Si. This silicon concentration is identified as the onset of the formation of a SiNy intergranular phase that is a few monolayers thick, having a chemical bonding similar to that in bulk silicon nitride. The observed changes in the XPS data coincide well with the structural changes in the material at different silicon contents. The unambiguous identification of phases, especially of minority phases from XPS data, is, however, not possible.

  6. Effect of traveling magnetic field on separation and purification of Si from Al-Si melt during solidification

    NASA Astrophysics Data System (ADS)

    Zou, Q. C.; Jie, J. C.; Liu, S. C.; Wang, T. M.; Yin, G. M.; Li, T. J.

    2015-11-01

    Separation and purification of the Si crystal during solidification process of hypereutectic Al-30Si melt under traveling magnetic field (TMF) were investigated in the present study. The results showed that under a proper condition the Si-rich layer can be formed in the periphery of the ingot while the inner microstructure is mainly the Al-Si eutectic structure. The intense melt flow carries the bulk liquid with higher Si content to promote the growth of the primary Si phase which is first precipitated close to the inner wall of the crucible with a relatively lower temperature, which resulting in the remarkable segregation of the primary Si phase. The impurity contents of the refined Si can be reduced to a very low level. The typical metallic impurities have removal fraction higher than 99.5%. In addition, there is a significant difference in the P contents between the primary and eutectic Si phases, which might be ascribed to the formation of AlP phase that acts as the heterogeneous nucleation sites. Furthermore, a considerable amount of Fe-containing particles with a size about 100-300 nm is found inside the eutectic Si phase, indicating an unintended entrapment of Fe in Si.

  7. Single-crystal structure and Raman spectroscopy of synthetic titanite analog CaAlSiO4F

    NASA Astrophysics Data System (ADS)

    Krüger, Hannes; Többens, Daniel M.; Tropper, Peter; Haefeker, Udo; Kahlenberg, Volker; Fuchs, Martin R.; Olieric, Vincent; Troitzsch, Ulrike

    2015-10-01

    Synthetic CaAlSiO4F, the Al-F analog of titanite, has been investigated using single-crystal synchrotron diffraction experiments at Beamline X06DA (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland) and Raman spectroscopy. The presented structural model with 40 parameters was refined against 506 unique reflections to a final R o b s of 0.026 (space group A2/ a, a = 6.9120(11), b = 8.5010(10), c = 6.435(2) Å, β = 114.670(11)°, and Z = 4) and exhibits less distorted coordination polyhedra than earlier models from powder data. Vibrational spectra were calculated in harmonic approximation at the Γ point from fully relaxed energy optimisations of the crystal structure, using 3D-periodic density functional theory with Gaussian basis sets and the software CRYSTAL06. The lattice parameters of the fully relaxed structure were in good agreement with the experimental values, with the calculated values 0.8 ± 0.4 % too large; the monoclinic angle was calculated 0.4° too large. The agreement of the calculated Raman frequencies with the observed ones was very good, with standard deviation ±3 cm-1 and maximum deviations of ±7 cm-1. Furthermore, a detailed discussion of the atomic displacements associated with each Raman mode is given.

  8. 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.

  9. Effect of alloying elements on the physicomechanical properties of copper and tin bronze

    NASA Astrophysics Data System (ADS)

    Ri, Kh.; Komkov, V. G.; Ri, E. Kh.

    2014-09-01

    The effect of alloying elements (Al, Si, Mn, Zn, Ni, As) on the physicomechanical properties of copper and tin bronze (6 wt % Sn) is studied. These alloying elements are found to increase the hardness and the microhardness of the structural constituents of Cu- X alloys due to hardening the α solid solution and eutectoid, and this effect of alloying elements is most effective in tin bronze. Alloyed copper and tin bronze have a lower thermal conductivity and corrosion resistance as compared to plain copper and tin bronze.

  10. Mechanical Effects of Hafnium and Boron Addition to Aluminum Alloy Films for Submicrometer LSI Interconnects

    NASA Astrophysics Data System (ADS)

    Onoda, Hiroshi; Takahashi, Eishi; Kawai, Yasuaki; Madokoro, Shoji; Fukuyo, Hideaki; Sawada, Susumu

    1993-11-01

    This is the first report on the mechanical properties of hafnium- and boron-added Al-Si-Cu alloy film for LSI interconnects. Two to three hundred ppm of hafnium and boron addition into Al-Si-Cu alloy film does not influence the Al alloy properties for metal lines as LSI interconnects, such as its low resistivity, low ohmic contact resistance with Si, and fine-line patterning feasibility. The mechanical properties of the Al alloy film, however, change greatly. Vertical hillock and lateral hillock formation is considerably suppressed during heat treatments used in LSI fabrication processes. Stress-induced void formation is also reduced during aging test at 125°C. These effects due to hafnium and boron addition are considered to be an impurity precipitation effect ihat was confirmed by X-ray diffraction analysis and electron probe microanalysis.

  11. Effects of Al/Si ordering on feldspar dissolution: Part II. The pH dependence of plagioclases' dissolution rates

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Min, Yujia; Jun, Young-Shin

    2014-02-01

    The rate of mineral dissolution in an aquatic environment is sensitive to the pH of the contacting solution. The pH dependence of mineral dissolution rate has been interpreted by the Transition State Theory-Surface Complexation Model (TST-SCM) formalism in terms of pH-sensitive variability in surface chemistry. In this study, we provide an alternative interpretation for the experimentally observed nonlinear pH dependence of feldspar dissolution rates. The interpretation is based on a new formalism for feldspar dissolution which, while compatible with the TST-SCM formalism, incorporates the effects of both surface chemistry and bulk chemistry on feldspar dissolution into the quantification of dissolution rate. The pH dependence of dissolution rate varies from one feldspar specimen to another because different TOT linkages within one solid matrix can respond differently to the attack of proton. Our results suggest that the pH dependence of feldspar dissolution rate is not a constant in general, and could be affected by pH, substitutional Al/Si ordering, chemical composition of the specimen, and the relative rapidness of linkage hydrolysis according to different mechanisms. The rate law proposed in this study is able to capture the experimentally observed pH dependence of the dissolution rates of a series of plagioclases, including albite, andesine, labradorite, bytownite, and anorthite. The effectiveness of the newly proposed formalism for feldspar dissolution, hence, suggests that dissolution reactions of minerals are combinations of surface renewal and heterogeneous chemical reactions. The currently widely used TST-SCM-based rate laws can be further improved by taking into account the effects of bulk chemistry and surface renewal in the prediction of mineral dissolution rates. An improved formalism for mineral dissolution will be mineral-specific, and will reflect the effects of the temporal decay in the availability of reactive surface sites as well as the

  12. Rutile solubility in H2O-NaAlSi3O8 fluids at High T and P: Implications form HFSE mobility in Subduction zones

    NASA Astrophysics Data System (ADS)

    Antignano, A.; Manning, C. E.

    2005-12-01

    The trace element signatures of arc magmas are characterized by HFSE depletion relative to the LILE. Rutile, a common accessory phase in high-pressure assemblages, is an important reservoir for the HFSE and is often invoked to explain the HFSE depletion of arc magmas. This model is in part based on experimental studies, which show that rutile has very low solubility in pure H2O. However, rutile is also a common accessory to eclogite-facies vein assemblages of albite, paragonite and quartz, which likely precipitated from slab-derived fluids. This observation requires either that fluid fluxes were unrealistically high, or that current estimates of Ti solubility are too low. A possible solution to this problem is that dissolved silicate components can enhance Ti solubility via complexing. To test this, we measured the solubility of rutile in H2O-NaAlSi3O8 (albite) bearing fluids at high T and P. Experiments were conducted using a piston-cylinder apparatus with NaCl-graphite furnaces. A single synthetic rutile crystal was loaded into a 1.6 mm OD Pt inner capsule, which was lightly crimped and then placed in a 3.5 OD Pt outer capsule with ultra pure H2O and powdered Amelia albite. Solubility was determined by the weight loss of the rutile grain after 10 hrs. A time series demonstrates that equilibrium is achieved after 8-10 hrs. Preliminary results at 800°C, 1.0 GPa, show that rutile solubility rises with increasing NaAlSi3O8 concentration from 1.15(12) millimolal at 2.18 wt% NaAlSi3O8 to 3.77(13) at 8.80 wt% NaAlSi3O8. Corundum mats + fluid are observed in 3.4-8.80 wt% NaAlSi3O8 and are interpreted to be the result of incongruent dissolution of albite. Quenched melt spheres where observed in an experiment containing ~15 wt% NaAlSi3O8, but not at 8.80 wt%. At 8.80 wt% NaAlSi3O8, rutile solubility is higher by a factor of 6 relative to that in pure H2O. Our results suggest that TiO2 solubility is increased by complexing with Na-Al-Si-bearing fluid components. It has

  13. Corrosion behavior of TiN, TiAlN, TiAlSiN-coated 316L stainless steel in simulated proton exchange membrane fuel cell environment

    NASA Astrophysics Data System (ADS)

    Nam, Nguyen Dang; Vaka, Mahesh; Tran Hung, Nguyen

    2014-12-01

    To gain high hardness, good thermal stability and corrosion resistance, multicomponent TiAlSiN coating has been developed using different deposition methods. In this study, the influence of Al and Si on the electrochemical properties of TiN-coated 316L stainless steel as bipolar plate (BP) materials has been investigated in simulated proton exchange membrane fuel cell environment. The deposited TiN, TiAlN and TiAlSiN possess high hardness of 23.9, 31.7, 35.0 GPa, respectively. The coating performance of the TiN coating is enhanced by Al and Si addition due to lower corrosion current density and higher Rcoating and Rct values. This result could be attributed to the formation of crystalline-refined TiN(200), which improves the surface roughness, surface resistance, corrosion performance, and decreased passive current density.

  14. Microstructural changes in a mechanically alloyed Al-6.2Zn-2.5Mg-1.7Cu alloy (7010) with and without particulate SiC reinforcement

    SciTech Connect

    Bhaduri, A.; Gopinathan, V.; Ramakrishnan, P.; Miodownik, A.P.

    1996-11-01

    Elemental powders of Al, Zn, Mg, and Cu (corresponding to the composition of 7010 aluminium alloy) were milled in a high-energy attritor with and without additions of SiC particulates. The microstructural changes taking place in the milled powders (which eventually lead to mechanical alloying) are found to be retarded by SiC additions. High-resolution techniques such as electron probe microanalysis (EPMA) and transmission electron microscopy/energy-dispersive X-ray analysis (TEM/EDX) revealed the presence of localized solute-rich regions long after the diffraction line from these solutes had ceased to appear in the X-ray diffractograms. Zinc appears to be more difficult to be mechanically alloyed into aluminum than either Cu or Mg in spite of its comparatively larger diffusivity in aluminum.

  15. A new color correlation method applied to XRF Al/Si ratios and other lunar remote sensing data. [X Ray Fluorescence

    NASA Technical Reports Server (NTRS)

    Clark, P. E.; Andre, C. G.; Adler, I.; Eliason, E.

    1978-01-01

    Orbital X-ray fluorescence Al/Si intensity ratios, corrected for variations in solar activity, are correlated with normal albedo, elevation measurements from laser altimetry data, and gamma ray data in the 2.75-8.60 MeV range. Each of these data sets is placed into a digital array consisting of 1/4 deg latitude by 1/4 deg longitude pixels. Information relative to the correlation of Al/Si ratios with each of the other data sets is presented in the following forms: (1) histograms are given for each data set to show the frequency distribution within the areas of common coverage; (2) density plots are produced from the plot of a two-dimensional array consisting of the Al/Si ratio vs the other parameter value for each pixel; and (3) color correlation maps are produced by placing the two-dimensional array into a 3 x 3 matrix consisting of nine equal subarrays containing an equal number of data points.

  16. Surface engineering of aluminum alloys for automotive engine applications

    NASA Astrophysics Data System (ADS)

    Nayak, S.; Dahotre, Narendra B.; Dahotre, Narendra B.

    2004-01-01

    The modification and refinement of surface and subsurface microstructure in Al-Si-based cast alloys via laser-induced rapid solidification can create a natural topography suitable for engine applications. The differential wear of the soft aluminum phase, hard silicon, and CuAl in the cell, along with the divorced eutectic nanostructure in the intercellular region, is expected to produce and replenish microfluidic channels and pits for efficient oil retention, spreading, and lubrication.

  17. The Role of Alloy Composition and T7 Heat Treatment in Enhancing Thermal Conductivity of Aluminum High Pressure Diecastings

    NASA Astrophysics Data System (ADS)

    Lumley, Roger N.; Deeva, Natalia; Larsen, Robert; Gembarovic, Jozef; Freeman, Joe

    2013-02-01

    The thermal conductivity of some common and experimental high pressure diecasting (HPDC) Al-Si-Cu alloys is evaluated. It is shown that the thermal conductivity of some compositions may be increased by more than 60 pct by utilizing T7 heat treatments. This may have substantial performance and cost benefits for applications where thermal management is a key design parameter.

  18. Influence of mechanical milling on the SiC particulate size in an Al-SiC composite

    NASA Astrophysics Data System (ADS)

    Mujahid, M.; Friska, I.

    2005-02-01

    Particle reinforced aluminum-matrix composites are particularly attractive for the automobile and air-craft industries, due to their light weight, high strength, and good wear resistance. In the present work, silicon carbide (SiC) particulates have been incorporated into a pure Al matrix with the help of mechanical milling in a planetary ball-mill. Composite powders were prepared using both raw as well as premilled SiC powders. The effect of milling time on the SiC particulate size was investigated. Systematic analysis of x-ray diffraction data revealed a reinforcement particle size of about 30 nm in a composite containing 50 vol.% SiC. It has been observed that the size reduction occurs at a faster rate when indirect milling is used.

  19. Effect of Li level, artificial aging, and TiB2 reinforcement on the fracture toughness of Weldalite (tm) 049-type alloys

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Plane strain fracture toughness (K sub IC) was evaluated for Weldalite (tm) 049 with and without TiB2 reinforcement. For the nonreinforced variant, changes in toughness were measured for various aging conditions and lithium levels. Toughness testing was carried out on fatigue precracked compact tension (CT) specimens at 24 C, as per ASTM standard E-399. Toughness was measured as a function of aging time at 160 C for the two Weldalite 049(1.3) heats. The composition of these heats differed only in that 0.03 wt pct. Ti was added to one as an additional grain refiner. Both heats showed a decrease in toughness with increasing aging time, although toughness values for one were significantly higher than for the other. This greater toughness may be due to a subtle change in the grain size resulting for the presence of Ti or, alternatively, to differences in texture or substructure formed during extrusion.

  20. Compared production behavior of borax and unborax premixed SiC reinforcement Al7Si-Mg-TiB alloys composites with semi-solid stir casting method

    NASA Astrophysics Data System (ADS)

    Haryono, M. B.; Sulardjaka, Nugroho, Sri

    2016-04-01

    The present study was aimed to investigate the effect of borax additive on physical and mechanical properties of Al7Si-Mg-TiB with the reinforcement of silicon carbide. In this case, the different weight percentage from the reinforcement of SiC (10, 15, and 20% wt), and the borax additive (ratio 1:4) were homogenously added into the matrix by employing the semi-solid stir casting method at the temperature of 590°C. Al7Si-Mg-TiB melted in an electric resistance furnace at 800°C for 25 minutes and the holding time of 5 minutes; SiC was stirred with borax inside the chamber and heated at the temperature of 250°C for 25 minutes. Then, it melted by lowing the temperature into 590°C. The SiC-borax mixture was added into the electric resistance furnace, and automatically stirred by the stirrer at a constant speed (500 rpm for 3 minutes) in the composite A17Si-Mg-TiB. It melted when heated at 750°C for 17minutes,then, casting was performed on the prepared mould. The characterizations of Al7Si-Mg-TiB-SiC/borax were porosity, hardness, and microstructure on the Al7Si-Mg-TiB-SiC/ borax. The porosity of AMC tended to increase along with the increaseof the wt% SiC (1.4%-3.6%); however, borax additive underwent a decrease in porosity (0.14%-1.3%). Further, hardness tended to improve along with the increase of wt% SiC. The unboraxmixture had 79,6 HRB up to 94 HRB. Whereas, the borax additive mixture had 105,8 HRB up to 121 HRB.

  1. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.

    1980-01-01

    Heats of transformation of eutectic alloys were measured for many binary and ternary systems by differential scanning calorimetry and thermal analysis. Only the relatively cheap and plentiful elements Mg, Al, Si, P, Ca, Cu, Zn were considered. A method for measuring volume change during transformation was developed using x-ray absorption in a confined sample. Thermal expansion coefficients of both solid and liquid states of aluminum and of its eutectics with copper and with silicon also were determined. Preliminary evaluation of containment materials lead to the selection of silicon carbide as the initial material for study. Possible applications of alloy PCMs for heat storage in conventional and solar central power stations, small solar receivers and industrial furnace operations are under consideration.

  2. Heat storage in alloy transformations

    NASA Astrophysics Data System (ADS)

    Birchenall, C. E.

    1980-03-01

    Heats of transformation of eutectic alloys were measured for many binary and ternary systems by differential scanning calorimetry and thermal analysis. Only the relatively cheap and plentiful elements Mg, Al, Si, P, Ca, Cu, Zn were considered. A method for measuring volume change during transformation was developed using x-ray absorption in a confined sample. Thermal expansion coefficients of both solid and liquid states of aluminum and of its eutectics with copper and with silicon also were determined. Preliminary evaluation of containment materials lead to the selection of silicon carbide as the initial material for study. Possible applications of alloy PCMs for heat storage in conventional and solar central power stations, small solar receivers and industrial furnace operations are under consideration.

  3. A survey of some metallographic etching reagents for restoration of obliterated engraved marks on aluminium-silicon alloy surfaces.

    PubMed

    Uli, Norjaidi; Kuppuswamy, R; Amran, Mohd Firdaus Che

    2011-05-20

    A brief survey to assess the sensitivity and efficacy of some common etching reagents for revealing obliterated engraved marks on Al-Si alloy surfaces is presented. Experimental observations have recommended use of alternate swabbing of 10% NaOH and 10% HNO(3) on the obliterated surfaces for obtaining the desired results. The NaOH etchant responsible for bringing back the original marks resulted in the deposition of some dark coating that has masked the recovered marks. The coating had been well removed by dissolving it in HNO(3) containing 10-20% acid. However, the above etching procedure was not effective on aluminium (99% purity) and Al-Zn-Mg-Cu alloy surfaces. Also the two reagents (i) immersion in 10% aq. phosphoric acid and (ii) alternate swabbing of 60% HCl and 40% NaOH suggested earlier for high strength Al-Zn-Mg-Cu alloys [23] were quite ineffective on Al-Si alloys. Thus different aluminium alloys needed different etching treatments for successfully restoring the obliterated marks. Al-Si alloys used in casting find wide applications especially in the manufacture of engine blocks of motor vehicles. Hence, the results presented in this paper are of much relevance in serial number restoration problems involving this alloy. PMID:21145675

  4. Fiber glass reinforced structural materials for aerospace application

    NASA Technical Reports Server (NTRS)

    Bartlett, D. H.

    1968-01-01

    Evaluation of fiber glass reinforced plastic materials concludes that fiber glass construction is lighter than aluminum alloy construction. Low thermal conductivity and strength makes the fiber glass material useful in cryogenic tank supports.

  5. Fabrication of TiC-Reinforced Composites by Vacuum Arc Melting: TiC Mode of Reprecipitation in Different Molten Metals and Alloys

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Arni, Z.; Tsirka, K.; Evangelou, A.; Lekatou, A.; Dracopoulos, V.

    2016-06-01

    TiC crystals were developed and grown through a melt dissolution and reprecipitation mechanism, in different alloy matrices (pure Fe, 316L, Fe-22 at.%Al, Ni-25at.%Al, and pure Co) through the use of Vacuum Arc Melting (VAM) process. The TiC surfaces exhibit a characteristic faceted mode of growth which is explained in terms of classic nucleation and crystal growth theories and is related with the well-known Jackson factor of crystal growth. Different morphologies of the finally solidified TiC grains are observed (dendritic, radially grown, isolated blocky crystals, particle clusters), the establishment of which may be most likely related with solidification progress, cooling rate, and melt compositional considerations. An initial, rough and qualitative phase identification shows a variety of compounds, and the attempts to define specific phase crystallographic-orientational relationships led to rather random results.

  6. Effects of reaction layer on interfacial shear properties and strength of fiber in silicon-carbide (SiC) fiber-reinforced titanium alloy composite

    SciTech Connect

    Kagawa, Yutaka; Masuda, Chitoshi; Fujiwara, Chikara; Fukushima, Akira

    1996-12-31

    The effect of the interfacial thickness of the reaction layer on the interfacial shear properties and the tensile strength of double carbon-coated SCS-6 SiC fiber in Ti-15Mo-5Zr-3Al alloy matrix composite was examined. The major reaction layer thickness, that is, titanium-carbide (TiC) layer thickness, varied with heat-exposure temperature and time, respectively, and the resultant mean thickness of the reaction layer of the composite ranged from 0.4 to 1.7 {micro}m. The critical interfacial toughness, G{sub i}{sup c}, and the mean shear sliding resistance, {tau}{sub s}, were evaluated by the thin specimen pushout technique. Tensile strength of the silicon-carbide (SiC) fiber extracted from the titanium alloy matrix before and after the heat exposure was determined in relationship to the thickness of the reaction layer. The critical interface toughness, G{sub i}{sup c}, for the failure of the root of the reaction layer was {approx}4 J/m{sup 2}, and the average shear sliding resistance of the interface, {tau}{sub s}, was 102 to 118 MPa. The interfacial shear mechanical properties were adequate to prevent failure of the fiber due to the stress concentration caused by cracks that formed first in the reaction layer. The results showed that when the growth of reaction layer was within 1.7 {micro}m, the mean strength of the extracted fiber was unaffected by the existence of the reaction layer because of weak bonding between it and the fiber. However, with the increase of the reaction layer thickness, the strength distribution of the extracted fiber tended to Weibull bimodal distribution.

  7. Influence of Sludge Particles on the Tensile Properties of Die-Cast Secondary Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Ferraro, Stefano; Timelli, Giulio

    2015-04-01

    The effects of sludge intermetallic particles on the mechanical properties of a secondary AlSi9Cu3(Fe) die-casting alloy have been studied. Different alloys have been produced by systematically varying the Fe, Mn, and Cr contents within the composition tolerance limits of the standard EN AC-46000 alloy. The microstructure shows primary α-Al x (Fe,Mn,Cr) y Si z sludge particles, with polyhedral and star-like morphologies, although the presence of primary β-Al5FeSi phase is also observed at the highest Fe:Mn ratio. The volume fraction of primary compounds increases as the Fe, Mn, and Cr contents increase and this can be accurately predicts from the Sludge Factor by a linear relationship. The sludge amount seems to not influence the size and the content of porosity in the die-cast material. Furthermore, the sludge factor is not a reliable parameter to describe the mechanical properties of the die-cast AlSi9Cu3(Fe) alloy, because this value does not consider the mutual interaction between the elements. In the analyzed range of composition, the design of experiment methodology and the analysis of variance have been used in order to develop a semi-empirical model that accurately predicts the mechanical properties of the die-cast AlSi9Cu3(Fe) alloys as function of Fe, Mn, and Cr concentrations.

  8. Study on nanocomposite Ti-Al-Si-Cu-N films with various Si contents deposited by cathodic vacuum arc ion plating

    NASA Astrophysics Data System (ADS)

    Shi, J.; Muders, C. M.; Kumar, A.; Jiang, X.; Pei, Z. L.; Gong, J.; Sun, C.

    2012-10-01

    In this study, nanocomposite Ti-Al-Si-Cu-N films were deposited on high speed steel substrates by the vacuum cathode arc ion plating (AIP) technique. By virtue of X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM), the influence of silicon content on the film microstructure and characteristics was investigated systematically, including the chemical composition, crystalline structure as well as cross-section morphologies. With increasing the silicon content, a deterioration of the preferred orientation and a dense globular structure were detected. In the meanwhile, atomic force microscopy (AFM), nano-indentation, Rockwell indenter and reciprocating test were also utilized to analyze the hardness, elastic modulus, H3/E2, friction coefficient, adhesive strength and wear rate of the Ti-Al-Si-Cu-N films. The results showed that an optimal silicon content correlated with the best mechanical and tribological properties of the presented Ti-Al-Si-Cu-N films existed. With increasing the silicon content, the hardness, elastic modulus and the ratio H3/E2 first were improved gradually, and then were impaired sharply again. When the silicon content reached to 6 at.%, the film possessed the highest hardness, elastic modulus and ratio H3/E2 of approximately 24 GPa, 218 GPa and 0.31, respectively. Besides, films containing both 6 at.% and 10 at.% Si contents obtained a relatively low friction coefficient and a good adhesive strength. The wear rate decreased with an increase in hardness, with the highest hardness corresponding to a wear rate around 1.3 × 10-5 mm3/(N m) of the film with 6 at.% Si content. The correlations between hardness and tribological properties for the films were also examined. The essence of above phenomena was attributed to the variations of microstructure and morphologies in the films induced by the increasing silicon content.

  9. Structure of mineral glasses—III. NaAlSi 3O 8 supercooled liquid at 805°C and the effects of thermal history

    NASA Astrophysics Data System (ADS)

    Taylor, Mark; Brown, Gordon E., Jr.; Fenn, Philip M.

    1980-01-01

    The distribution of interatomic distances in amorphous NaAlSi 3O 8 has been determined at 805°C by X-ray radial distribution analysis to investigate structural differences between the glass (T < 763°C) and the supercooled liquid (763°C < T < 1118°C). Except for slight differences attributable to thermal expansion, no significant changes were observed. The sample crystallized during the course of the experiment, but at least one crystal-free data set was obtained. The transition from the inferred six-membered ring structure of the supercooled liquid to the four-membered ring structure of the crystal was clearly visible in radial distribution function (RDF's) determined before and after crystallization. RDF's were also determined at 25°C for two NaAlSi 3O 8 glasses with different histories. The first was derived from a melt that had been cooled slowly from 1600 to 32°C above the melting point ( Tf = 1118° C) to detect possible repolymerization to a more 'crystal-like' structure as the melt approached Tf. The second glass was prepared by holding a single crystal of Amelia albite at 50°C above Tf to see if the crystalline four-membered ring structure was preserved in melts at temperatures just above the liquidus. No significant differences were observed between these two RDF's and one obtained from a glass quenched from 1800°C. These results suggest that in addition to the destruction of formation of a periodic structure, melting and crystallization in NaAlSi 3O 8 also involves a repolymerization of tetrahedra. This would explain the observed kinetic barrier to melting and crystallization in the anhydrous system and the catalytic effect of small amounts of water or alkali oxide.

  10. The structure and properties of single-layer and gradient-layered coatings of the Ti-Al-Si-Cr-Mo-S-N system

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, Stanislav; Pinzhin, Yurii

    2015-10-01

    Using the method of microprobe analysis and transmission electron microscopy, the influence of obtaining conditions upon particular elemental composition and growth structure coatings of Ti-Al-Si-Mo-S-N system was studied. The possibility of formation and characteristics of the structural and elastic-stress state single-layer coatings with nanoscale columnar or equiaxed grains and gradient-layered, combining two types of selected structure, was defined. On the basis of hardness, tribological properties and coating hardness, a conclusion was made about the relative prospects of its use as wear-resistant coatings with a nanocrystalline structure.

  11. A thermodynamic analysis of the system LiAlSiO4-NaAlSiO4-Al2O3-SiO2-H2O based on new heat capacity, thermal expansion, and compressibility data for selected phases

    NASA Astrophysics Data System (ADS)

    Fasshauer, Detlef W.; Chatterjee, Niranjan D.; Cemic, Ladislav

    Heat capacity, thermal expansion, and compressibility data have been obtained for a number of selected phases of the system NaAlSiO4-LiAlSiO4-Al2O3-SiO2-H2O. All Cp measurements have been executed by DSC in the temperature range 133-823K. The data for T>=223K have been fitted to the function Cp(T)=a+cT -2+dT -0.5+fT -3, the fit parameters being The thermal expansion data (up to 525°C) have been fitted to the function V0(T)=V0(T) [1+v1 (T-T0)+v2 (T-T0)2], with T0=298.15K. The room-temperature compressibility data (up to 6 GPa) have been smoothed by the Murnaghan equation of state. The resulting parameters are These data, along with other phase property and reaction reversal data from the literature, have been simultaneously processed by the Bayes method to derive an internally consistent thermodynamic dataset (see Tables 6 and 7) for the NaAlSiO4-LiAlSiO4-Al2O3-SiO2-H2O quinary. Phase diagrams generated from this dataset are compatible with cookeite-, ephesite-, and paragonite-bearing assemblages observed in metabauxites and common metasediments. Phase diagrams obtained from the same database are also in agreement with the cookeite-free, petalite-, spodumene-, eucryptite-, and bikitaite-bearing assemblages known to develop in the subsolidus phase of recrystallization of lithium-bearing pegmatites. It is gratifying to note that the cookeite phase relations predicted earlier by Vidal and Goffé (1991) in the context of the system Li2O-Al2O3-SiO2-H2O agree with our results in a general way.

  12. Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite

    SciTech Connect

    Mandal, Durbadal; Viswanathan, Srinath

    2013-11-15

    The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 °C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of Al–SiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 50–80 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: • The composite was successfully heat treated at 575°C for 1

  13. Development Program for Natural Aging Aluminum Casting Alloys

    SciTech Connect

    Dr. Geoffrey K. Sigworth

    2004-05-14

    A number of 7xx aluminum casting alloys are based on the ternary Al-Zn-Mg system. These alloys age naturally to high strength at room temperature. A high temperature solution and aging treatment is not required. Consequently, these alloys have the potential to deliver properties nearly equivalent to conventional A356-T6 (Al-Si-Mg) castings, with a significant cost saving. An energy savings is also possible. In spite of these advantages, the 7xx casting alloys are seldom used, primarily because of their reputation for poor castibility. This paper describes the results obtained in a DOE-funded research study of these alloys, which is part of the DOE-OIT ''Cast Metals Industries of the Future'' Program. Suggestions for possible commercial use are also given.

  14. Molten pool behaviour and its physical mechanism during selective laser melting of TiC/AlSi10Mg nanocomposites: simulation and experiments

    NASA Astrophysics Data System (ADS)

    Yuan, Pengpeng; Gu, Dongdong

    2015-01-01

    Simulation of temperature evolution and thermal behaviour of the molten pool during selective laser melting (SLM) of TiC/AlSi10Mg nanocomposites was performed, using a finite volume method. Some important physical phenomena, such as a transition from powder to solid, nonlinearities produced by temperature-dependent material properties and fluid flow, were taken into account in the calculation. The effects of Marangoni convection and SLM processing parameters, such as laser power and scan speed, on temperature evolution behaviour, molten pool dimensions and liquid lifetime were thoroughly investigated. The simulation results showed that Marangoni convection played a crucial role in intensifying the convective heat transfer and changing the molten pool geometry. The temperature of laser-powder interaction zone, the molten pool dimensions and liquid lifetime increased with increasing laser power or decreasing scan speed. The maximum temperature gradient within the molten pool increased significantly with increasing the applied laser power, but increased slightly as a higher scan speed was applied. The experimental study on the interlayer bonding and densification behaviour and the surface morphologies and balling effect of the SLM-processed TiC/AlSi10Mg nanocomposites parts was performed. The experimental results validated the thermal behaviour and underlying physical mechanism of the molten pool obtained in the simulations.

  15. Correlation of Al/Si X-ray fluorescence data with other remote sensing data from the Taurus-Littrow area

    NASA Technical Reports Server (NTRS)

    Andre, C. G.; Hallam, M. E.; Weidner, J. R.; Clark, P. E.; Adler, I.; Podwysocki, M. H.; Philpotts, J. A.

    1975-01-01

    Al/Si intensity ratios from the Apollo 15 X-ray fluorescence experiment have been analyzed in conjunction with such other remote-sensing data as visible albedo measurements, color-difference photographs, and relative spectral reflectivity curves for the purpose of defining geochemical units in the Taurus-Littrow area. A geochemical boundary between the dark-mantle unit and the western edge of the Taurus Mountains is indicated by all the remote-sensing techniques considered. The major component of the ejecta from Catena Littrow, located within the dark-mantle unit, is highland-type material. The areal extent of the ejecta determined from the Al/Si data is at least 30 km along the Apollo 15 ground track. The constraint imposed upon depth to high-alumina material at Catena Littrow is 520 m. If the high-alumina material excavated at Catena Littrow is an extension of the Taurus Mountain 'roots', then the maximum slope of the buried highland surface from Catena Littrow to the Taurus Mountains border is less than 2.0 deg

  16. Precipitation of dispersoids in aluminum alloys

    SciTech Connect

    Last, H.R.

    1991-01-01

    The influence of alloy composition and preheat treatment on the precipitation of the metastable Al{sub 3}Zr, {beta}{prime}, phase in ternary alloys and the subsequent recrystallization behavior was investigated. The ternary alloys contained zirconium and one of the following elements: copper, manganese, zinc, or silicon. Diffusion couples were constructed and the values for the interdiffusion coefficient for several elements in aluminum were calculated. The calculated values for the interdiffusion coefficients were used in a finite difference model for the prediction of the homogenization of an as-cast microstructure during preheating. {beta}{prime} was observed to precipitate on defects such as dislocations and low-angle boundaries when a critical solute level in all ternary alloys was reached. The critical solute level was system dependent. Homogeneous nucleation of {beta}{prime} occurred in Al-Si-Zr alloys. In Al-Zn-Zr alloys the shape of the {beta}{prime} deviated from its usual spherical shape to a cube shape when the zinc level exceeds approximately 4 wt. %. When compared to other alloying element additions, small amounts of silicon (between 0.25 and 0.5 wt %) had the greatest influence on not only the recrystallization behavior of the alloy, but also the precipitation of {beta}{prime}.

  17. Reinforced Carbon Nanotubes.

    DOEpatents

    Ren, Zhifen; Wen, Jian Guo; Lao, Jing Y.; Li, Wenzhi

    2005-06-28

    The present invention relates generally to reinforced carbon nanotubes, and more particularly to reinforced carbon nanotubes having a plurality of microparticulate carbide or oxide materials formed substantially on the surface of such reinforced carbon nanotubes composite materials. In particular, the present invention provides reinforced carbon nanotubes (CNTs) having a plurality of boron carbide nanolumps formed substantially on a surface of the reinforced CNTs that provide a reinforcing effect on CNTs, enabling their use as effective reinforcing fillers for matrix materials to give high-strength composites. The present invention also provides methods for producing such carbide reinforced CNTs.

  18. Transverse Reinforcement in Reinforced Concrete Columns

    NASA Astrophysics Data System (ADS)

    Gramblička, Štefan; Veróny, Peter

    2013-11-01

    In the article we are dealing with the influence of transverse reinforcement to the resistance of a cross-section of the reinforced concrete columns and also with the effective detailing of the column reinforcement. We are verifying the correctness of design guides for detailing of transverse reinforcement. We are also taking into account the diameter of stirrups and its influence over transverse deformation of column.

  19. High Strength Discontinuously Reinforced Aluminum For Rocket Applications

    NASA Technical Reports Server (NTRS)

    Pandey, A. B.; Shah, S. R.; Shadoan, M.

    2003-01-01

    This study presents results on the development of a new aluminum alloy with very high strength and ductility. Five compositions of Al-Mg-Sc-Gd-Zr alloy were selected for this purpose. These alloys were also reinforced with 15 volume percent silicon-carbide and boron-carbide particles to produce Discontinuously Reinforced Aluminum (DRA) materials. Matrix alloys and DRA were processed using a powder metallurgy process. The helium gas atomization produced very fine powder with cellular-dentritic microstructure. The microstructure of matrix alloys showed fine Al3Sc based precipitate which provides significant strengthening in these alloys. DRA showed uniform distribution of reinforcement in aluminum matrix. DRA materials were tested at -320 F, 75 F in air and 7S F in gaseous hydrogen environments and matrix alloys were tested at 75 F in air. DRA showed high strengths in the range of 89-111 ksi (614-697 MPa) depending on alloy compositions and test environments. Matrix alloys had a good combination of strength, 84-89 ksi (579-621 MPa) and ductility, 4.5-6.5%. The properties of these materials can further be improved by proper control of processing parameters.

  20. Thermal evolution behavior and fluid dynamics during laser additive manufacturing of Al-based nanocomposites: Underlying role of reinforcement weight fraction

    NASA Astrophysics Data System (ADS)

    Gu, Dongdong; Yuan, Pengpeng

    2015-12-01

    In this study, a three-dimensional transient computational fluid dynamics model was established to investigate the influence of reinforcement weight fraction on thermal evolution behavior and fluid dynamics during selective laser melting (SLM) additive manufacturing of TiC/AlSi10Mg nanocomposites. The powder-to-solid transition and nonlinear variation of thermal physical properties of as-used materials were considered in the numerical model, using the Gaussian distributed volumetric heat source. The simulation results showed that the increase of operating temperature and the resultant formation of larger melt pool were caused by the increase of weight fraction of reinforcement. The Marangoni convection was intensified using a larger reinforcement content, accelerating the coupled motion of fluid and solid particles. The circular flows appeared when the TiC content reached 5.0 wt. % and the larger-sized circular flows were present as the reinforcement content increased to 7.5 wt. %. The experimental study on surface morphologies and microstructures on the polished sections of SLM-processed TiC/AlSi10Mg nanocomposite parts was performed. A considerably dense and smooth surface free of any balling effect and pore formation was obtained when the reinforcement content was optimized at 5.0 wt. %, due to the sufficient liquid formation and moderate Marangoni flow. Novel ring-structured reinforcing particulates were tailored because of the combined action of the attractive effect of centripetal force and repulsive force, which was consistent with the simulation results.

  1. Friction and wear of oxide-ceramic sliding against IN-718 nickel base alloy at 25 to 800 C in atmospheric air

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Deadmore, Daniel L.

    1989-01-01

    The friction and wear of oxide-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C were measured. The oxide materials tested were mullite (3Al2O3.2SiO2); lithium aluminum silicate (LiAlSi(x)O(y)); polycrystalline monolithic alpha alumina (alpha-Al2O3); single crystal alpha-Al2O3 (sapphire); zirconia (ZrO2); and silicon carbide (SiC) whisker-reinforced Al2O3 composites. At 25 C the mullite and zirconia had the lowest friction and the polycrystalline monolithic alumina had the lowest wear. At 800 C the Al2O3-8 vol/percent SiC whisker composite had the lowest friction and the Al2O3-25 vol/percent SiC composite had the lowest wear. The friction of the Al2O3-SiC whisker composites increased with increased whisker content while the wear decreased. In general, the wear-resistance of the ceramics improve with their hardness.

  2. Quantitative radiographic analysis of fiber reinforced polymer composites.

    PubMed

    Baidya, K P; Ramakrishna, S; Rahman, M; Ritchie, A

    2001-01-01

    X-ray radiographic examination of the bone fracture healing process is a widely used method in the treatment and management of patients. Medical devices made of metallic alloys reportedly produce considerable artifacts that make the interpretation of radiographs difficult. Fiber reinforced polymer composite materials have been proposed to replace metallic alloys in certain medical devices because of their radiolucency, light weight, and tailorable mechanical properties. The primary objective of this paper is to provide a comparable radiographic analysis of different fiber reinforced polymer composites that are considered suitable for biomedical applications. Composite materials investigated consist of glass, aramid (Kevlar-29), and carbon reinforcement fibers, and epoxy and polyether-ether-ketone (PEEK) matrices. The total mass attenuation coefficient of each material was measured using clinical X-rays (50 kev). The carbon fiber reinforced composites were found to be more radiolucent than the glass and kevlar fiber reinforced composites. PMID:11261603

  3. Effects of vacuum annealing treatment on microstructures and residual stress of AlSi10Mg parts produced by selective laser melting process

    NASA Astrophysics Data System (ADS)

    Chen, Tian; Wang, Linzhi; Tan, Sheng

    2016-07-01

    Selective laser melting (SLM)-fabricated AlSi10Mg parts were heat-treated under vacuum to eliminate the residual stress. Microstructure evolutions and tensile properties of the SLM-fabricated parts before and after vacuum annealing treatment were studied. The results show that the crystalline structure of SLM-fabricated AlSi10Mg part was not modified after the vacuum annealing treatment. Additionally, the grain refinement had occurred after the vacuum annealing treatment. Moreover, with increasing of the vacuum annealing time, the second phase increased and transformed to spheroidization and coarsening. The SLM-produced parts after vacuum annealing at 300∘C for 2 h had the maximum ultimate tensile strength (UTS), yield strength (YS) and elongation, while the elastic modulus decreased significantly. In addition, the tensile residual stress was found in the as-fabricated AlSi10Mg samples by the microindentation method.

  4. Effect of Al-Si Pack Cementation Diffusion Coating on High-Temperature Low-Cycle Fatigue Behavior of Inconel 713LC

    NASA Astrophysics Data System (ADS)

    Mansuri, Mohammadreza; Hadavi, Seyed Mohammad Mehdi; Zare, Esmail

    2016-01-01

    In this research, an Al-Si protective coating was applied on the surface of an IN713LC specimen using pack cementation method. Surface-treated and untreated specimens were exposed to low-cycle fatigue by tension-tension loading under total strain control at 1173 K (900 °C) in air. Based on the obtained results, the hardening/softening, cyclic stress-strain, and fatigue life curves were plotted and analyzed. The results showed that both the single-stage and two-stage coatings improved the fatigue life of the substrate. However, owing to more silicon content of single-stage coating compared to that of two-stage coating, the effect of single-stage coating was superior. The stress response of the treated material was lower compared with the untreated one. Observations of the specimen section and fracture surface examinations were used to analyze fatigue behavior of both coated and uncoated materials.

  5. MAX phase - Alumina composites via elemental and exchange reactions in the Tin+1ACn systems (A=Al, Si, Ga, Ge, In and Sn)

    NASA Astrophysics Data System (ADS)

    Cuskelly, Dylan; Richards, Erin; Kisi, Erich

    2016-05-01

    Extension of the aluminothermal exchange reaction synthesis of Mn+1AXn phases to systems where the element 'A' is not the reducing agent was investigated in systems TiO2-A-Al-C for A=Al, Si, Ga, Ge, In and Sn as well as Cr2O3-Ga-Al-C. MAX phase-Al2O3 composites were made in all systems except those with A=Ga or In. The effectiveness of conversion to MAX phases was generally in the range 63-96% without optimisation of starting ratios. Optimisation in the Ti-Si-C system gave a MAX phase component with >98% Ti3SiC2.

  6. Numerical Analysis of Interfacial Bonding of Al-Si Particle and Mild Steel Substrate by Cold Spray Technique Using the SPH Method

    NASA Astrophysics Data System (ADS)

    Manap, Abreeza; Ogawa, Kazuhiro; Okabe, Tomonaga

    The deposition mechanism of the cold spray (CS) technique is investigated numerically using the smoothed particle hydrodynamics (SPH) method. The CS process is simulated by modeling the impact of a spherical Al-Si powder particle on a mild steel substrate. In this work, the adhesive interaction between the contacting surfaces is described by intersurface forces using the cohesive zone model. Simulation results show that successful bonding is achieved above the critical velocity, but rebound was observed at high velocities. This indicates that optimum deposition is achieved only within a certain range of particle velocities. The simulated deformed particle shape evolution and estimated critical velocity from other sources were compared and good agreement was obtained. The analyses demonstrate the feasibility of the presented SPH methodology and the adhesive interaction model for simulating the deformation behavior of CS particles.

  7. Palus Somni - Anomalies in the correlation of Al/Si X-ray fluorescence intensity ratios and broad-spectrum visible albedos. [lunar surface mineralogy

    NASA Technical Reports Server (NTRS)

    Clark, P. E.; Andre, C. G.; Adler, I.; Weidner, J.; Podwysocki, M.

    1976-01-01

    The positive correlation between Al/Si X-ray fluorescence intensity ratios determined during the Apollo 15 lunar mission and a broad-spectrum visible albedo of the moon is quantitatively established. Linear regression analysis performed on 246 1 degree geographic cells of X-ray fluorescence intensity and visible albedo data points produced a statistically significant correlation coefficient of .78. Three distinct distributions of data were identified as (1) within one standard deviation of the regression line, (2) greater than one standard deviation below the line, and (3) greater than one standard deviation above the line. The latter two distributions of data were found to occupy distinct geographic areas in the Palus Somni region.

  8. First principles study of band line up at defective metal-oxide interface: oxygen point defects at Al/SiO2 interface

    NASA Astrophysics Data System (ADS)

    Tea, Eric; Huang, Jianqiu; Hin, Celine

    2016-03-01

    The dielectric breakdown at metal-oxide interfaces is a critical electronic device failure mechanism. Electronic tunneling through dielectric layers is a well-accepted explanation for this phenomenon. Theoretical band alignment studies, providing information about tunneling, have already been conducted in the literature for metal-oxide interfaces. However, most of the time materials were assumed defect free. Oxygen vacancies being very common in oxides, their effect on band lineup is of prime importance in understanding electron tunneling in realistic materials and devices. This work explores the effect of oxygen vacancy and oxygen di-vacancy at the Al/SiO2 interface on the band line up within Density Functional Theory using PBE0 hybrid exchange and correlation functional. It is found that the presence of defects at the interface, and their charge state, strongly alters the band line up.

  9. First principle study of magnetic and electronic properties of single X (X = Al, Si) atom added to small carbon clusters (C n X, n = 2-10)

    NASA Astrophysics Data System (ADS)

    Afshar, M.; Hoseini, S. S.; Sargolzaei, M.

    2016-07-01

    In this paper, the magnetic and electronic properties of single aluminum and silicon atom added to small carbon clusters (C n X; X = Al, Si; n = 2-10) are studied in the framework of generalized-gradient approximation using density functional theory. The calculations were performed for linear, two dimensional and three dimensional clusters based on full-potential local-orbital (FPLO) method. The total energies, HOMO-LUMO energy gap and total magnetic moments of the most stable structures are presented in this work. The calculations show that C n Si clusters have more stability compared to C n Al clusters. In addition, our magnetic calculations were shown that the C n Al isomers are magnetic objects whereas C n Si clusters are nonmagnetic objects.

  10. Calcic amphibole thermobarometry in metamorphic and igneous rocks: New calibrations based on plagioclase/amphibole Al-Si partitioning and amphibole/liquid Mg partitioning

    NASA Astrophysics Data System (ADS)

    Molina, J. F.; Moreno, J. A.; Castro, A.; Rodríguez, C.; Fershtater, G. B.

    2015-09-01

    Dependencies of plagioclase/amphibole Al-Si partitioning, DAl/Siplg/amp, and amphibole/liquid Mg partitioning, DMgamp/liq, on temperature, pressure and phase compositions are investigated employing robust regression methods based on MM-estimators. A database with 92 amphibole-plagioclase pairs - temperature range: 650-1050 °C; amphibole compositional limits: > 0.02 apfu (23O) Ti and > 0.05 apfu Al - and 148 amphibole-glass pairs - temperature range: 800-1100 °C; amphibole compositional limit: CaM4/(CaM4 + NaM4) > 0.75 - compiled from experiments in the literature was used for the calculations (amphibole normalization scheme: 13-CNK method). Statistical analysis reveals a significant dependence of DAl/Siplg/amp on pressure, temperature, Al fraction in amphibole T1-site, XAlT1, and albite fraction in plagioclase, XAb, leading to the barometric expression:

  11. Photoluminescence of CaAlSiN3:Eu2+-based fine red-emitting phosphors synthesized by carbothermal reduction and nitridation method

    NASA Astrophysics Data System (ADS)

    Li, Shuxing; Peng, Xia; Liu, Xuejian; Huang, Zhengren

    2014-12-01

    In this research, we have presented the synthesis and characterization of the various Ca1-xEuxAl0.76Si1.18N3 (x = 0.01 ∼ 0.1) red-emitting phosphors, which were successfully prepared by carbothermal reduction and nitridation (CTRN) method without the strict needs of high pressure. Here, raw materials were CaCO3, AlN, Si3N4, Eu2O3, and C. In particular, C was considered as efficient and robust reducing agent. The influences of reaction temperature, holding time, C content, and Eu2+ concentration were investigated in the crystal phase compositions and photoluminescence properties of the as-prepared phosphors. Importantly, CaAlSiN3:Eu2+-based red phosphors with interesting properties were obtained with reaction temperature at 1600 °C for 4 h by atmospheric N2-10%H2 pressure, and the C/O ratio of 1.5:1, respectively. The emission peak positions of as-prepared phosphors were red-shifted from 607 nm to 654 nm with Eu2+ concentration from 1 mol% to 10 mol%. Meanwhile the highest luminescence intensity was achieved with 2 mol% of Eu2+ concentration, which showed high external quantum efficiency up to 71%. Combining the phosphor blend of green-emitting β-sialon:Eu2+, yellow-emitting Ca-α-sialon:Eu2+, and red-emitting Ca0.98Eu0.02Al0.76Si1.18N3 with a blue LED (light emitting diodes), warm white LED can be generated, yielding the color rendering index (Ra) of 93 at correlated color temperature (CCT) of 3295 K. These results indicate that CaAlSiN3:Eu2+-based red-emitting phosphors prepared by facile CTRN are highly promising candidates for warm white LEDs.

  12. Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope. Thesis

    NASA Technical Reports Server (NTRS)

    Justi, S.

    1985-01-01

    It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

  13. Grain growth in Al alloy conductors as a result of rapid annealing

    NASA Astrophysics Data System (ADS)

    Towner, Janet M.; van de Ven, Evert P.; Hopkins, Craig G.

    1984-01-01

    Aluminum and aluminum alloy thin films were rapidly annealed using high intensity visible light. Under suitable conditions, substantial grain growth was achieved in the Al-Cu and Al-Si-Cu conductors and this grain growth had a beneficial effect on electromigration. Unfortunately, this growth did not occur uniformily across the wafer. A second phenomenon, which resulted from thermal cycling, was the solid phase reduction of SiO2 by the overlying Al film.

  14. Solidification, growth mechanisms, and associated properties of aluminum-silicon and magnesium lightweight casting alloys

    NASA Astrophysics Data System (ADS)

    Hosch, Timothy Al

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  15. Wettability of Molten Aluminum-Silicon Alloys on Graphite and Surface Tension of Those Alloys at 1273 K (1000 °C)

    NASA Astrophysics Data System (ADS)

    Mao, Weiji; Noji, Takayasu; Teshima, Kenichiro; Shinozaki, Nobuya

    2016-06-01

    The wettability of molten aluminum-silicon alloys with silicon contents of 0, 6, 10, and 20 mass pct on graphite substrates by changing the placing sequence of aluminum and silicon and the surface tension of those alloys were investigated at 1273 K (1000 °C) using the sessile drop method under vacuum. The results showed that the wetting was not affected by changing the placing sequence of the Al-Si alloys on the graphite substrates. The wettability was not improved significantly upon increasing the Si content from 0 to 10 mass pct, whereas a notable decrease of 22 deg in the contact angle was observed when increasing the Si content from 10 to 20 mass pct. This was attributed to the transformation of the interfacial reaction product from Al4C3 into SiC, provided the addition of Si to Al was sufficient. It was verified that the liquid Al can wet the SiC substrate very well in nature, which might explain why the occurrence of SiC would improve the wettability of the Al-20 mass pct Si alloy on the graphite substrate. The results also showed that the surface tension values of the molten Al-Si alloys decreased monotonously with an increase in Si content, being 875, 801, 770, and 744 mN/m for molten Al, Al-6 mass pct Si, Al-10 mass pct Si, and Al-20 mass pct Si alloys, respectively.

  16. On the Production of He, Ne, and AR Isotopes from Mg, Al, Si, Ca, Fe, and NI in an Artificially Irradiated Meteoroid

    NASA Astrophysics Data System (ADS)

    Wieler, R.; Signet, P.; Rosel, R.; Herpers, U.; Lupke, M.; Lange, H.-J.; Michel, R.

    1992-07-01

    The production of He, Ne, and Ar isotopes from their main target elements was investigated in an experiment (1) by irradiating a 50-cm-diameter gabbro sphere isotropically with 1.6 GeV protons. The model meteoroid contained, among a large number of other targets, pure element foils of Mg, Al, Si, Fe, and Ni at 10 different depths and wollastonite targets at 3 different depths in central bores. After the irradiation, radionuclide production in these targets was measured by gamma spectrometry. Stable He, Ne, and Ar isotopes were measured in statically operated mass spectrometers. Here, we report the results for stable He, Ne, and Ar isotopes and for ^22Na. The production depth profiles vary widely, ranging from profiles with near-surface production 15% higher than in the center (^22Na from Fe) to such profiles with production in the center 45% higher than near the surface (^20Ne from Mg). The isotope ratios ^3He/^4He and ^3He/^21Ne in Mg, Al, Si and ^22Ne/^21Ne in Mg all decrease significantly with increasing shielding. The production rates of He, Ne, and ^22Na from Mg, Al, and Si in the 1600-MeV simulation experiment are 1.5 to 3 times higher than in the model meteoroid of similar size but irradiated earlier with 600 MeV protons (2). This increase is attributed to the increase of the production of secondary neutrons with primary energies rising from 600 to 1600 MeV. This effect also causes the depth dependences of isotope ratios observed in the 1600-MeV simulation that was not seen in the 600-MeV experiment. Model calculations of the production of He, Ne, and Ar isotopes and of ^22Na were performed for the artificial meteorites of the 600- and 1600 MeV-exposures as well as for real meteoroids. Production rates were calculated from depth-dependent p- and n- spectra, which were derived by Monte Carlo techniques using the HERMES code system (3), and from cross sections for the relevant nuclear reactions as described earlier (4). The cross section database for p

  17. A novel yellow-emitting SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

    SciTech Connect

    Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

    2013-12-15

    Ce{sup 3+}-doped and Ce{sup 3+}/Li{sup +}-codoped SrAlSi{sub 4}N{sub 7} phosphors were synthesized by gas pressure sintering of powder mixtures of Sr{sub 3}N{sub 2}, AlN, α-Si{sub 3}N{sub 4}, CeN and Li{sub 3}N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi{sub 4}N{sub 7}:Ce{sup 3+}(Ce{sup 3+}/Li{sup +}) were investigated in this work. The band structure calculated by the DMol{sup 3} code shows that SrAlSi{sub 4}N{sub 7} has a direct band gap of 3.87 eV. The single crystal analysis of Ce{sup 3+}-doped SrAlSi{sub 4}N{sub 7} indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi{sub 4}N{sub 7} was identified as a major phase of the fired powders, and Sr{sub 5}Al{sub 5}Si{sub 21}N{sub 35}O{sub 2} and AlN as minor phases. Both Ce{sup 3+} and Ce{sup 3+}/Li{sup +} doped SrAlSi{sub 4}N{sub 7} phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce{sup 3+}/Li{sup +}-doped SrAlSi{sub 4}N{sub 7} (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr{sub 0.97}Al{sub 1.03}Si{sub 3.997}N/94/maccounttest14=t0005{sub 1}8193 {sub 7}:Ce{sup 3+}{sub 0.03} with a commercial blue InGaN chip. It indicates that SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} is a promising yellow emitting down-conversion phosphor for white LEDs. - Graphical abstract: One-phosphor converted white light-emitting diode (LED) was fabricated by combining a blue LED chip and a yellow-emitting SrAlSi4N7:Ce{sup 3+} phosphor (see inset), which has the color rendering index of 78 and color temperature of 6300 K. - Highlights: • We reported a new yellow nitride phosphor suitable for solid state lighting. • We solved the crystal structure and evidenced a disordered Si/Al distribution. • We fabricated a high color rendering

  18. Magnesium-lithium casting alloys

    NASA Technical Reports Server (NTRS)

    Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.

    1974-01-01

    The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.

  19. Thermodynamics, Diffusion, and Structure of Liquid NaAlSi3O8 at Elevated Temperature and Pressure from Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Neilson, R.; Spera, F. J.; Ghiorso, M. S.

    2014-12-01

    Thermodynamic properties of silicate melts at high temperature (T) and pressure (P) are crucial to understanding Earth accretion, magma oceans, petrogenesis, and crustal growth. However, equations of state for silicate liquids at mantle conditions are scarce, due to experimental challenges. Molecular Dynamics (MD) simulations allow investigation of thermodynamic and transport properties of silicate melts at high P and T and enable the correlation of liquid structure with computed properties. Using classical MD, we studied liquid NaAlSi3O8 in the range 0-42 GPa and 3000-5137 K. Density ranged from 2.2 to 3.6 g/cm3, and all simulations were performed in the microcanonical (NEV) ensemble using the potential from Matsui (1998). An equation of state with internal energy E(V,T) was developed using the RT scaling-Vinet formulation (Ghiorso et al., 2009). From thermodynamic relationships, the Grüneisen parameter, isobaric expansivity, isothermal compressibility, heat capacity, and other functions are computed over the P-T range of the MD simulations. Diffusion coefficients (D) range from 1.5×10-9 to 5.9×10-8 m2/s and typically order Na>Al>O>Si at a given state point. Generally, D decreases with P and increases with T except for a low P anomalous region along the 3065 K isotherm. Anomalous diffusion for Al, Si, and O is congruent with laboratory experiments at P<10 GPa (e.g., Shimizu and Kushiro, 1984; Poe et al., 1997; Tinker and Lesher, 2001; Tinker et al., 2003). Activation energy for Na is on the order of -75.3 kJ/mol with activation volume -1.74 cm3/mol. The anomalous peak in diffusivity for Si and O occurs at ~3 GPa, which marks a subtle increase in the average coordination number (CN) for O around O from 9.35 to 10.31. The average CN for O around O generally increases with P, but it systematically drops at 8, 15, and 20 GPa for 3065, 3944, and 5137 K, respectively. The concentrations of AlO5 and SiO5 polyhedra maximize near 16 and 35 GPa, respectively.

  20. Processes for fabricating composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2015-11-24

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  1. Quantifying Uncertainties in the Thermo-Mechanical Properties of Particulate Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Mital, Subodh K.; Murthy, Pappu L. N.

    1999-01-01

    The present paper reports results from a computational simulation of probabilistic particulate reinforced composite behavior. The approach consists use of simplified micromechanics of particulate reinforced composites together with a Fast Probability Integration (FPI) technique. Sample results are presented for a Al/SiC(sub p)(silicon carbide particles in aluminum matrix) composite. The probability density functions for composite moduli, thermal expansion coefficient and thermal conductivities along with their sensitivity factors are computed. The effect of different assumed distributions and the effect of reducing scatter in constituent properties on the thermal expansion coefficient are also evaluated. The variations in the constituent properties that directly effect these composite properties are accounted for by assumed probabilistic distributions. The results show that the present technique provides valuable information about the scatter in composite properties and sensitivity factors, which are useful to test or design engineers.

  2. The processing and properties of discontinuously reinforced aluminum composites

    SciTech Connect

    Geiger, A.L.; Walker, J.A. )

    1991-08-01

    Discontinuously-reinforced aluminum (DRA) SiC whisker or particle-reinforced Al-alloy matrix composites produced by P/M methods have progressed toward commercial applications, supported by growing data bases and large-scale production facilities. Attention is presently given to the elastic modulus, plastic, ductile, and toughness characteristics of representative DRA formulations, as well as to the DRAs commercially available in the forms of sheets, extrusions, and optical and instrument grade structures able to supplant beryllium. 36 refs.

  3. Y 3-xMg 2AlSi 2O 12: Cex3+ phosphors - prospective for warm-white light emitting diodes

    NASA Astrophysics Data System (ADS)

    Katelnikovas, Arturas; Bareika, Tomas; Vitta, Pranciškus; Jüstel, Thomas; Winkler, Holger; Kareiva, Aivaras; Žukauskas, Artūras; Tamulaitis, Gintautas

    2010-07-01

    Y 3-xMg 2AlSi 2O 12: Cex3+ (YMASG:Ce) phosphors were synthesized by sol-gel combustion technique at different temperatures from 1400 to 1550 °C. Samples with x = 0.015, 0.03, 0.045, and 0.06 were fabricated and characterized using powder X-ray diffraction (XRD), photoluminescence spectroscopy, and fluorescence lifetime measurements in frequency domain. XRD patterns confirmed single-phase garnet crystal structure for all the samples independently of their substitutional level and annealing temperature. In respect to Y 3Al 5O 12:Ce 3+ (YAG:Ce) phosphor, which was synthesized for comparison by a different sol-gel procedure, the photoluminescence band of these garnets is red shifted, indicating a prospective for application of this novel phosphor in warm-white light emitting diodes (LEDs). The luminescence decays bi-exponentially. The main component has a characteristic decay time decreasing from 72 to of 50 ns with increasing sintering temperature and cerium content, while ˜2% of the excitation decays with a characteristic decay time of ˜8 ns.

  4. Ab initio geometry optimization and ground state properties of layered ternary carbides Ti3MC2 (M = Al, Si and Ge)

    NASA Astrophysics Data System (ADS)

    Zhou, Yanchun; Sun, Zhimei; Wang, Xiaohui; Chen, Shengqi

    2001-11-01

    The crystal structures of all layered ternary carbides called '312' phases including Ti3AlC2, Ti3SiC2 and Ti3GeC2 have been fully optimized by means of ab initio total-energy calculations. The equilibrium lattice parameters, the atomic positions in the unit cell and interatomic distances have been determined. The differences between the calculated and the measured lattice constants are generally less than 1%. It is also shown that c/a of the hexagonal lattices decreases from Ti3AlC2 to Ti3GeC2. The calculated bulk moduli are 190 GPa for Ti3AlC2, 202 GPa for Ti3SiC2 and 198 GPa for Ti3GeC2, respectively, which are comparable to that of TiC. The electronic structures reveal that the Ti(1, 2) and C atoms form a strong Ti(2)-C-Ti(1)-C-Ti(2) covalent bond chain, while the bonding between Ti(2) and M (M = Al, Si, Ge) is relatively weak. The strong Ti(2)-C-Ti(1)-C-Ti(2) covalent bond chain corresponds to the high strength and modulus, while the metallic bond corresponds to the metallic conductivity of these ternaries.

  5. Some new members of MAX family including light-elements: Nanolayered Hf2XY (X= Al, Si, P and Y=B, C, N)

    NASA Astrophysics Data System (ADS)

    Aydin, Sezgin; Tatar, Aynur; Ciftci, Yasemin Oztekin

    2016-03-01

    The structural, electronic, mechanical and dynamical properties of new members of MAX family (Hf2XY, X=Al, Si, P and Y= B, C, N compounds) with Cr2AlC-type structure have been investigated by first-principles density functional plane-wave pseudopotential calculations within generalized gradient approximation. From calculated cohesive energies, all compounds are energetically stable. And, from calculated elastic constants and phonon dispersion curves, it is shown that all compounds are mechanically stable, while the boron including ones are dynamically unstable except for Hf2PB. At the same time, related mechanical properties such as bulk and shear moduli are calculated. For further mechanical characterization, hardnesses of the compounds are determined theoretically. It is observed from electronic structure calculations including band structure and partial density of states, all stable compounds are metallic. Additionally, bonding nature of the compounds are analyzed by using 3D and 2D electron density maps, Mulliken atomic charges and bond overlap populations.

  6. Band alignment study on Al/SiO2 and Cu/SiO2 metal-oxide interface with the presence of point defect

    NASA Astrophysics Data System (ADS)

    Huang, Jianqiu; Tea, Eric; Hin, Celine

    Metal-Oxide interface has a wide use in electronic devices. Currently, technological development is aiming on the shrinkage of electronic devices' size. Based on the knowledge of electron tunneling effect, the reduction of dielectric thickness would cause an exponential increase on electron tunneling probability which contributes to current leakage. It might cause dielectric breakdown, which could make a severe and irreversible damage to the devices. Therefore, the main purpose of this study is to explore the possible factors that can lead to dielectric breakdown at metal-oxide interface. Density functional theory ab initio calculation has been applied to study the Al/SiO2and Cu/SiO2 metal-oxide interface. Results on oxygen (di)vacancies at the interface will be presented and compared with the defect free model. The band alignment has been constructed to describe the variation of potential barrier height due to defect at interface. Results show the oxygen (di)vacancies at interface might trap electron and reduce potential barrier height. Moreover, the potential barrier height has a significant dependence on defects charge states. Supported by Air Force.

  7. Band alignment study on Al/SiO2and Cu/SiO2 metal-oxide interface with the presence of point defect

    NASA Astrophysics Data System (ADS)

    Huang, Jianqiu; Tea, Eric; Hin, Celine

    Metal-Oxide interface has a wide use in electronic devices. Currently, technological development is aiming on the shrinkage of electronic devices' size. Based on the knowledge of electron tunneling effect, the reduction of dielectric thickness would cause an exponential increase on electron tunneling probability which contributes to current leakage. It might cause dielectric breakdown, which could make a severe and irreversible damage to the devices. Therefore, the main purpose of this study is to explore the possible factors that can lead to dielectric breakdown at metal-oxide interface. Density functional theory ab initio calculation has been applied to study the Al/SiO2and Cu/SiO2 metal-oxide interface. Results on oxygen (di)vacancies at the interface will be presented and compared with the defect free model. The band alignment has been constructed to describe the variation of potential barrier height due to defect at interface. Results show the oxygen (di)vacancies at interface might trap electron and reduce potential barrier height. Moreover, the potential barrier height has a significant dependence on defects charge states. Supported by Air Force.

  8. Stress generation in Al-Si-Cu metallization resulting from thermal cycling between -196 °C and 250 °C

    NASA Astrophysics Data System (ADS)

    Baldwin, Frank; Holloway, Paul H.; Bordelon, Mark; Watkins, Thomas R.

    1996-06-01

    The effects of thermally cycling Al-Si-Cu VLSI metallization down to -196 °C have been studied in unpatterned and patterned films with and without surface passivation using wafer curvature and x-ray diffraction techniques. Both passivated and unpassivated unpatterned metallization showed development of compressive stresses in the thin film after cooling to -196 °C and warming to 22 °C. This was attributed to plastic deformation at -196 °C leading to a reversal of stress from tensile to compressive upon warming to room temperature. The relaxation of this compressive stress was characterized at room temperature immediately after warming from -196 °C and after cooling from anneals between 50 °C and 250 °C. The stress in patterned (1 to 2 μm line widths) thin films with passivation remained tensile, and this was attributed to a reduction in grain boundary area and inhibition of grain boundary diffusion. Therefore, the tensile stress was maintained even after thermal cycling several times between -196 °C and 22 °C. Higher stress levels were observed on smaller line widths, and lower tensile stresses were observed on metal lines that exhibited stress voids.

  9. Structural and electronic properties of AB- and AA-stacking bilayer-graphene intercalated by Li, Na, Ca, B, Al, Si, Ge, Ag, and Au atoms

    NASA Astrophysics Data System (ADS)

    Tayran, Ceren; Aydin, Sezgin; Çakmak, Mehmet; Ellialtıoğlu, Şinasi

    2016-04-01

    The structural and electronic properties of X (=Li, Na, Ca, B, Al, Si, Ge, Ag, and Au)-intercalated AB- and AA-stacking bilayer-graphene have been investigated by using ab initio density functional theory. It is shown that Boron (Lithium)-intercalated system is energetically more stable than the others for the AB (AA) stacking bilayer-graphene systems. The structural parameters, electronic band structures, and orbital nature of actual interactions are studied for the relaxed stable geometries. It is seen that the higher the binding energy, the smaller is the distance between the layers, in these systems. The electronic band structures for these systems show that different intercalated atoms can change the properties of bilayer-graphene differently. For qualitative description of the electronic properties, the metallicities of the systems are also calculated and compared with each other. The Mulliken analysis and electron density maps clearly indicate that the interactions inside a single layer (intralayer interactions) are strong and highly covalent, while the interactions between the two layers (interlayer interactions) are much weaker.

  10. Improved understanding of thermally activated structural changes in Al/SiOx/p-Si tunnel diodes by means of infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Bierhals, Andreas; Aberle, Armin G.; Hezel, Rudolf

    1998-02-01

    Thermal treatment at temperatures well above 100 °C is known to lead to a degradation of the current-voltage (I-V) characteristics of Al/SiOx/p-Si metal-insulator-semiconductor (MIS) tunnel diodes. In the present work, the structural changes caused in these devices by annealing at temperatures around 300 °C are investigated by means of grazing internal reflection (GIR) infrared spectroscopy, I-V measurements, and scanning electron microscopy. While all previous studies attributed the structural changes to a single chemical process, we show that at least three different processes occur: the reduction of SiOx by Al, the diffusion of aluminum or oxygen through the tunnel insulator, and the formation of Al spikes through the tunnel insulator. The first two processes lead to significant changes in the Al-O and Si-O bond concentrations in the tunnel insulator, but the impact on the I-V characteristics of the MIS tunnel diode is negligible. In contrast, the third process leads to a drop of the baseline of the GIR spectra and to a significant degradation or even a complete destruction of the diode characteristics.

  11. Vibrational spectroscopic study of the copper silicate mineral ajoite (K,Na)Cu7AlSi9O24(OH)6·3H2O

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Xi, Yunfei

    2012-06-01

    Ajoite (K,Na)Cu7AlSi9O24(OH)6·3H2O is a mineral named after the Ajo district of Arizona. Raman and infrared spectroscopy were used to characterise the molecular structure of ajoite. The structure of the mineral shows disorder which is reflected in the difficulty of obtaining quality Raman spectra. The Raman spectrum is characterised by a broad spectral profile with a band at 1048 cm-1 assigned to the ν1 (A1g) symmetric stretching vibration. Strong bands at 962, 1015 and 1139 cm-1 are assigned to the ν3 SiO4 antisymmetric stretching vibrations. Multiple ν4 SiO4 vibrational modes indicate strong distortion of the SiO4 tetrahedra. Multiple AlO and CuO stretching bands are observed. Raman spectroscopy and confirmed by infrared spectroscopy clearly shows that hydroxyl units are involved in the ajoite structure. Based upon the infrared spectra, water is involved in the ajoite structure, probably as zeolitic water.

  12. Site Preference of Ternary Alloying Additions to AuTi

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    Atomistic modeling of the site substitution behavior of several alloying additions, namely. Na, Mg, Al, Si. Sc, V, Cr, Mn. Fe, Co, Ni, Cu, Zn, Y, Zr. Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, and Pt in B2 TiAu is reported. The 30 elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice. Results of large scale simulations are also presented, distinguishing between additions that remain in solution from those that precipitate a second phase.

  13. NASA-UVA Light Aerospace Alloy and Structures Technology program (LA2ST)

    NASA Technical Reports Server (NTRS)

    Starke, Edgar A., Jr.; Gangloff, Richard P.; Herakovich, Carl T.; Scully, John R.; Shiflet, Gary J.; Stoner, Glenn E.; Wert, John A.

    1995-01-01

    The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. The general aim is to produce relevant data and basic understanding of material mechanical response, environment/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated students for aerospace technologies. Specific technical objectives are presented for each of the following research projects: time-temperature dependent fracture in advanced wrought ingot metallurgy, and spray deposited aluminum alloys; cryogenic temperature effects on the deformation and fracture of Al-Li-Cu-In alloys; effects of aging and temperature on the ductile fracture of AA2095 and AA2195; mechanisms of localized corrosion in alloys 2090 and 2095; hydrogen interactions in aluminum-lithium alloys 2090 and selected model alloys; mechanisms of deformation and fracture in high strength titanium alloys (effects of temperature and hydrogen and effects of temperature and microstructure); evaluations of wide-panel aluminum alloy extrusions; Al-Si-Ge alloy development; effects of texture and precipitates on mechanical property anisotropy of Al-Cu-Mg-X alloys; damage evolution in polymeric composites; and environmental effects in fatigue life prediction - modeling crack propagation in light aerospace alloys.

  14. Complete Al-SI Order in Scapolite Me[subscript 37.5], Ideally Ca[subscript 3]Na[subscript 5][Al[subscript 8]Si[subscript 16]O[subscript 48

    SciTech Connect

    Antao, Sytle M.; Hassan, Ishmael

    2011-09-06

    The structure of an intermediate scapolite (Me{sub 36.6}) from Lake Clear, Ontario, was obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinement in space group P4{sub 2}/n. The chemical formula obtained by electron microprobe is Na{sub 2.19}Ca{sub 1.35}K{sub 0.16}[Al{sub 3.95}Si{sub 8.05}O{sub 24}]Cl{sub 0.55}(CO{sub 3}){sub 0.41}(SO{sub 4}){sub 0.04}, equivalent to Me{sub 36.6}. The unit-cell parameters are a 12.07899(1), c 7.583467(9) {angstrom}, and V 1106.443(2) {angstrom}{sup 3}. The average distances are = 1.617(1) {angstrom}, = 1.744(1) {angstrom}, and = 1.601(1) {angstrom}. Therefore, the T1 and T3 sites contain only Si atoms, and the T2 site contains only Al atoms, so the Al and Si atoms are completely ordered. Complete Al-Si order was predicted for Me{sub 37.5}, ideally Ca{sub 3}Na{sub 5}[Al{sub 8}Si{sub 16}O{sub 48}]Cl(CO{sub 3}), and is confirmed in this study. Antiphase domain boundaries (APBs) in scapolite cannot arise from Al-Si order because the average distances indicate complete Al-Si order in Me{sub 36.6}. If APBs were to arise from Al-Si order, switching of the T sites across the APBs will occur, and complete Al-Si order cannot be observed. Therefore, Al-Si order, which is present to various extents across the scapolite series, can be ruled out as the cause for the APBs. Order involving Cl and CO{sub 3} is the cause for the APBs in scapolite.

  15. The investigation on the stratification phenomenon of aluminum rear alloyed layer in silicon solar cells

    NASA Astrophysics Data System (ADS)

    Xi, Xi; Chen, Xiaojing; Zhang, Song; Shi, Zhengrong; Li, Guohua

    2015-06-01

    A stratification phenomenon of aluminum rear alloyed layer was found in the study of aluminum rear emitter N-type solar cells. It is related to the composition of the paste. The outer aluminum alloyed layer can be called as aluminum doped emitter, and it gives the contribution to the junction formation. The inner layer is only the Al/Si mixed layer. The aluminum atoms in this layer are not bonded with silicon atoms. This inner layer will ruin the quality of the rear junction. The shunt resistance, reverse current density and the junction electric leakage value are getting worse when the thickness of the inner layer increases. The thickness of the inner Al/Si mixed layer increases with the increasing of firing temperature, while the depth of the aluminum doped emitter almost does not change. From the analyses, the inner Al/Si mixed layer is redundant and deleterious. Only a single deep aluminum doped rear emitter is needed for N-type solar cells. The highest power conversion efficiency of 19.93% for aluminum rear emitter N-type cells without the stratification phenomenon has been obtained.

  16. Production of aluminum-silicon alloy and ferrosilicon and commercial purity aluminum by the direct reduction process. Third interim technical report, Phase C for the period 1980 July 1-1980 September 30

    SciTech Connect

    Bruno, M.J.

    1980-10-01

    Pilot reactor VSR-3 operation in the third quarter was directed to tapping molten alloy product. Modifications to the hearth region included a tapping furnace to maintain taphole temperature, a graphite ring filter to separate carbides from matal and an alumina liner to eliminate carbiding from reaction of alloy with the graphite hearth walls. Tapping was not successful, however, due to high alloy viscosity from a large concentration of carbides. Three runs were made on the pilot crystallizer to determine the effects of alloy composition, cooling rate, tamping rate, remelt temperature and rate on eutectic Al-Si yield.

  17. K -shell ionization cross sections of Al, Si, S, Ca, and Zn for oxygen ions in the energy range 1. 1--8 MeV

    SciTech Connect

    Geretschlaeger, M. ); Smit, Z. ); Steinbauer, E. )

    1992-03-01

    {ital K}-shell ionization cross sections induced by 1.1--8-MeV oxygen ions in Al, Si, S, Ca, and Zn were measured using different target thicknesses. The cross sections for vanishingly thin and for charge-equilibrium targets were obtained by extrapolation. The experimental results are compared to the perturbed stationary-state approximation with energy-loss, Coulomb, and relativistic corrections (ECPSSR) cross sections (Brandt and Lapicki, Phys. Rev. A 23, 1717 (1981)), to the modification of the ECPSSR theory (MECPSSR) (Benka, Geretschlaeger, and Paul, J. Phys. (Paris) Colloq. Suppl. 12, C9-251 (1987)), to the theory for direct Coulomb ionization of the 1{ital s}{sigma} molecular orbital (Montenegro and Sigaud, J. Phys. B 18, 299 (1985)), and to several semiclassical approximation codes using either the united atom binding procedure or the variational approach of Andersen {ital et} {ital al}. (Nucl. Instrum. Methods 192, 79 (1982)). The cross sections were also compared to the statistical molecular-orbital theory of inner-shell ionization for (nearly) symmetric atomic collisions (Mittelman and Wilets, Phys. Rev. 154, 12 (1967)). For fast collisions ({xi}{similar to}1), the ionization cross sections are well reproduced by theories for direct Coulomb ionization. For slower collisions ({xi}{lt}1), the experimental cross sections are systematically higher than the direct-ionization values, but they agree satisfactorily with the summed cross sections for direct Coulomb ionization and for molecular-orbital ionization. Best agreement (within a factor of 2) was found for the sums of MECPSSR and statistical cross sections.

  18. Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Hemingway, B.S.; Westrum, E.F., Jr.; Metz, G.W.; Essene, E.J.

    1987-01-01

    The heat capacity of cryolite (Na3AlF6) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S0298 = 238.5 J/mol KS0T-S0298 = 145.114 ln T+ 193.009*10-3T- 10.366* 105 T2- 872.89 J/mol K (273-836.5 K)??STrans = 9.9J/mol KS0T-S0298 =198.414 ln T+73.203* 10-3T-63.814* 105 T2-1113.11 J/mol K (836.5-1153 K) with the transition temperature between ??- and ??-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system NaFeAlSiOF. The resultant phase diagrams allow constraints to be placed on the fO2, fF2, aSiO2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log fO2 is approximately -19.2, log fF2 is -31.9 to -33.2, and aSiO2 is -1.06 at assumed P T conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland. ?? 1987.

  19. Observation of current polarity effect in stressing as-formed sub-micron Al-Si-Cu/TiW/TiSi 2 contacts

    NASA Astrophysics Data System (ADS)

    Chen, Li-Zen; Hsu, Klaus Y.-J.

    1999-06-01

    Formation of good silicide contacts becomes more important but difficult as the contact size continues shrinking toward the deep sub-micron regime. At the same time, higher current density, which may easily appear in small regions, could pose strong impact to the long-term reliability of sub-micron contacts. In this work, high current density stress experiments were conducted on the Al-Si-Cu/TiW/TiSi 2 contacts with the size ranging from 0.5×0.5 μm 2 down to 0.25×0.25 μm 2. The self-aligned silicide contacts were formed by using collimated sputtering, E-beam lithography, RTA, and RIE techniques. The silicide contacts were sintered at 400°C for 30 min. Cross-bridge Kelvin resistor structures were formed for electrical stressing and contact resistance measurement. One-way and two-way stressings were performed at high current density (˜10 7 A/cm 2) and the contact resistance was measured periodically at low current density during the stressing to monitor the evolution. It was found that the initial resistance of as-formed contacts was higher than expected. This is probably due to the difficulty of forming good interfaces in the small contact region by sputtering and that the sintering temperature may not be high enough to smear out the imperfection. The stressing was found to anneal the contacts. With electrons flowing from metal layer into the contact window, the contact resistance was reduced more efficiently than with reverse current of the same density. Stressed first by reverse current then by normal current, the resistance showed a two-step reduction with a significant transition at the switch of current polarity. For prolonged stressing, the contacts were gradually degraded and the reverse current induced more severe damage. These observations indicate strong electromigration effect at the small contacts.

  20. Habituation of reinforcer effectiveness.

    PubMed

    Lloyd, David R; Medina, Douglas J; Hawk, Larry W; Fosco, Whitney D; Richards, Jerry B

    2014-01-01

    In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE) that links behavioral- and neural-based explanations of reinforcement. We argue that HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009; Rankin etal., 2009). We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow) normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect "accelerated-HRE." Consideration of HRE is important for the development of effective reinforcement-based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior. PMID:24409128

  1. Magnetic and half-metallic properties of the full-Heusler alloys Co2TiX(X=Al,Ga;Si,Ge,Sn;Sb)

    NASA Astrophysics Data System (ADS)

    Lee, S. C.; Lee, T. D.; Blaha, P.; Schwarz, K.

    2005-05-01

    The electronic structure and magnetic properties of the full-Heusler alloys Co2TiX (X element from groups III, IV and V) were studied by first principle calculations. Previous calculations found Co2TiAl and Co2TiSn not to be half metallic. In this paper, however, it will be shown that the alloys with X =Al,Si,Ge,Sn are half metallic and ferromagnetic. The effect of atomic disorder in the Ti-Al sublattices reduces the half metallicity of the Co2TiAl Heusler alloy.

  2. On the Development of MMCS Containing Copper with Silicon Carbide Reinforcement using Nanomaterials and Dynamic Compaction

    SciTech Connect

    Popov, V A; Lesuer, D R; Kotov, I A; Ivanov, V V; Smirnov, O M; Marmulev, A V; Zayats, S V; Beketov, I V

    2002-04-10

    Metal matrix composites (MMCs) are promising engineering materials for a wide spectrum of applications. There are many possible matrix-reinforcement combinations including MMCs containing copper or copper alloy matrices [1-3]. The present study is concerned with copper reinforced with SiC particles. The materials studied here were processed from nano-scale matrix powders and consolidated using dynamic compaction.

  3. Microstructure and magnetic properties of nanostructured (Fe0.8Al0.2)100-xSix alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Boukherroub, N.; Guittoum, A.; Laggoun, A.; Hemmous, M.; Martínez-Blanco, D.; Blanco, J. A.; Souami, N.; Gorria, P.; Bourzami, A.; Lenoble, O.

    2015-07-01

    We report on how the microstructure and the silicon content of nanocrystalline ternary (Fe0.8Al0.2)100-xSix powders (x=0, 5, 10, 15 and 20 at%) elaborated by high energy ball milling affect the magnetic properties of these alloys. The formation of a single-phase alloy with body centred cubic (bcc) crystal structure is completed after 72 h of milling time for all the compositions. This bcc phase is in fact a disordered Fe(Al,Si) solid solution with a lattice parameter that reduces its value almost linearly as the Si content is increased, from about 2.9 Å in the binary Fe80Al20 alloy to 2.85 Å in the powder with x=20. The average nanocrystalline grain size also decreases linearly down to 10 nm for x=20, being roughly half of the value for the binary alloy, while the microstrain is somewhat enlarged. Mössbauer spectra show a sextet thus suggesting that the disordered Fe(Al,Si) solid solution is ferromagnetic at room temperature. However, the average hyperfine field diminishes from 27 T (x=0) to 16 T (x=20), and a paramagnetic doublet is observed for the powders with higher Si content. These results together with the evolution of both the saturation magnetization and the coercive field are discussed in terms of intrinsic and extrinsic properties.

  4. NDE Elastic Properties of Fiber-Reinforced Composite Materials

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.

    1995-01-01

    Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

  5. High-Temperature Creep Behavior Of Fiber-Reinforced Niobium

    NASA Technical Reports Server (NTRS)

    Petrasek, Donald W.; Titran, Robert H.

    1990-01-01

    Study conducted to determine feasibility of using composite materials in advanced space power systems, described in 22-page report. Tungsten fibers reduce creep and mass in advanced power systems. Reinforcing niobium alloys with tungsten fibers increases their resistances to creep by factors of as much as 10.

  6. Constraints on Titanite Acitvity in the System CaTiSiO4O-CaAlSiO4F: Implications for Thermobarometry in Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Tropper, P.; Manning, C. E.; Essene, E. J.

    2006-12-01

    Titanite is a common accessory mineral that could be used reliably in phase equilibrium calculations, if activity-composition relations in Al-F titanites were known. Troitzsch and Ellis (2001, CMP, 142, 543) and Tropper et al. (2002, JPet., 43, 1787) gave non-ideal mixing models along the join CaTiSiO4O- CaAlSiO4F. Tropper et al. (2002) derived a negative interaction parameter W, whereas Troitzsch and Ellis (2001) derived a regular model with both positive and negative W, but favored positive values. These differences strongly influence calculated CaTiSiO4O activity (attn). Although more experiments are needed, our result that γttn<1 at high T indicates a large degree of non-ideal behavior, even at >900°C, which in turn will affect thermobarometry. Comparing available activity models shows that at these T, attn is substantially underestimated by the fully ionic model used by Manning and Bohlen (1991, CMP, 109, 1), in which attn = XCaXTiXSi(XO)5. This model assumes independent mixing of Al for Ti and random mixing of F and O on all O sites. However, F substitutes only in one O site (O1; Oberti et al., 1991, EJM, 3, 777). A fully ionic model should therefore be recast as attn = XCaXTiXSiXO, where XO indicates the mole fraction of O on the (O1) site. The substitution of F on the O1 site is coupled with Al, so it is called the ideal coupled model. Unlike the regular model, the prefered ionic model departs strongly from ideality at ≤600°C, consistent with independent constraints. However, experimentally determined attn is approximated by an ideal molecular model (XTi) at ≥900°C, so this model is recommended for thermobarometry in high- T metamorphic rocks until more data are available. Recalculation of the P recorded by the three eclogites from Manning and Bohlen (1991) using the different activity models discussed here yields differences that may be as high as 2.0 GPa.

  7. Reinforced plastics durability

    SciTech Connect

    Pritchard, G.

    1999-01-01

    Written especially for first-time users of reinforced plastics. The book offers substantial introductory information with key concepts. Chapters examine the long-term threats to the integrity of reinforced plastics: outdoor weathering, solvent/water attack, high temperatures, and repetitive stress.

  8. Interdiffusion and Reaction between Zr and Al Alloys from 425 degrees to 625 degrees C

    SciTech Connect

    J. Dickson; L. Zhou; A. Ewh; M. Fu; D. D. Keiser, Jr.; Y. H. Sohn; A. Paz y Puente

    2014-06-01

    Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo nuclear fuels and Al cladding alloys. Interdiffusion and reactions between Zr and Al, Al-2 wt.% Si, Al-5 wt.% Si or AA6061 were investigated using solid-to-solid diffusion couples annealed in the temperature range of 425 degrees to 625 degrees C. In the binary Al and Zr system, the Al3Zr and Al2Zr phases were identified, and the activation energy for the growth of the Al3Zr phase was determined to be 347 kJ/mol. Negligible diffusional interactions were observed for diffusion couples between Zr vs. Al-2 wt.% Si, Al-5 wt.% Si and AA6061 annealed at or below 475 degrees C. In diffusion couples with the binary Al–Si alloys at 560 degrees C, a significant variation in the development of the phase constituents was observed including the thick t1 (Al5SiZr2) with Si content up to 12 at.%, and thin layers of (Si,Al)2Zr, (Al,Si)3Zr, Al3SiZr2 and Al2Zr phases. The use of AA6061 as a terminal alloy resulted in the development of both T1 (Al5SiZr2) and (Al,Si)3Zr phases with a very thin layer of (Al,Si)2Zr. At 560 degrees C, with increasing Si content in the Al–Si alloy, an increase in the overall rate of diffusional interaction was observed; however, the diffusional interaction of Zr in contact with multicomponent AA6061 with 0.4–0.8 wt.% Si was most rapid.

  9. Composite Intersection Reinforcement

    NASA Technical Reports Server (NTRS)

    Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

    2013-01-01

    An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

  10. Composite intersection reinforcement

    NASA Technical Reports Server (NTRS)

    Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

    2010-01-01

    An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

  11. Separating Effect of a Novel Combined Magnetic Field on Inclusions in Molten Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    He, Yanjie; Li, Qiulin; Liu, Wei

    2012-10-01

    The feasibility and effectiveness of a novel combined magnetic field (CMF) on the removal of inclusions with a density smaller than the surrounding melt were investigated. The experiment of the separating effect of CMF was conducted on a laboratory-scale apparatus by the simultaneous application of a rotating magnetic field (RMF) and a downward traveling magnetic field (TMF). Primary silicon particles precipitating from the solidification process of Al-Si-Cu alloy were regarded as the inclusions in a molten aluminum alloy. It was found that a CMF consisting of both a RMF and a downward TMF was able to separate silicon particles from the molten Al-Si-Cu alloy by making these particles migrate vertically toward the upper part of the samples. Compared with downward TMF or RMF, CMF improved the separating effectiveness substantially. It was proposed that this type of CMF was approved to be highly effective at eliminating the inclusions with a density smaller than the surrounding molten alloy. A tentative mechanism for the high separating effect of CMF was discussed.

  12. TiC reinforced cast Cr steels

    SciTech Connect

    Dogan, O.N.; Hawk, J.A.; Schrems, K.K.

    2006-06-01

    A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5–4.5Ti, and 1–1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.

  13. Substitution of Nickel by Combined Addition of Cobalt and Zirconium in Alloy A 332

    NASA Astrophysics Data System (ADS)

    Wüstenhagen, Andreas; Tonn, Babette

    2011-01-01

    Due to the increasing international competition and the resulting pricing pressure it is imperative to avoid the use of expensive alloying elements during the production of aluminium castings. The piston alloy A 332 shows an optimum combination of mechanical and casting properties and an attractive cost-performance ratio whereas nickel is the most expensive alloying element. A substitution of nickel by a combined addition of low contents of cobalt and zirconium has the potential capacitiy to increase the mechanical properties and reduce the costs of the alloy. At Clausthal University of Technology Thermo-Calc simulations and casting experiments were carried out to investigate the effect of the nickel subtitution. Thermo-Calc-simulations were made to analyze the intermetallic phases in these alloys. These simulations were evaluated by observations under optical microscope and SEM of specimens poured into permanent moulds. The size and morphology of the intermetallic phases and the primary silicon was analyzed by the use of image analysis software. The mechanical properties of the alloys were determined by tensile tests at room temperature, 250° C and 350° C. The tensile specimens were tested in as-cast and pre-aged condition. The effect on the castability was characterized by determining the flow length and the susceptibility to form shrinkages and hot cracks. The standard alloy A 332 and the new piston alloy with cobalt and zirconium were compared. The new alloy AlSi12,6Cu1Mg1CoZr exhibits a yield strength of 115 MPa and a tensile strength of 171 MPa at 250° C in pre-aged condition (250° C/100 h). At 350° C the new alloy displays a yield strength of 57 MPa and a tensile strength of 85 MPa in pre-aged condition (350° C/100h). Compared to the reference alloy AlSi12,6Cu1Ni1Mg1 the yield strength at 250° C was improved about 25% and the yield strength at 350° C about 7%. The favorable castability of the reference alloy is not affected by the substitution of

  14. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  15. Reinforced concrete offshore platform

    SciTech Connect

    Martyshenko, J.P.; Martyshenko, S.J.; Kotelnikov, J.S.; Kutukhtin, E.G.; Petrosian, M.S.; Ilyasova, N.I.; Volkov, J.S.; Vardanian, A.M.

    1987-10-20

    A reinforced concrete offshore platform is described comprising a honeycomb foundation (A), a supporting structure (B) and an above-surface section (C) carrying appropriate equipment. The honeycomb foundation (A) and the supporting structure (B) are made of prefabricated reinforced concrete elements which are polyhedral hollow prisms arranged with gaps between the external sides thereof and joined by a system of prestressed vertical diaphragm walls and horizontal diaphragm walls formed by pre-tensioning reinforcing bars placed in the gaps between the faces of the prisms and casting in-situ the gaps later on.

  16. Tungsten fiber reinforced superalloys - A status review

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Signorelli, R. A.

    1981-01-01

    After a review of refractory metal fiber/alloy matrix composite development, a discussion is presented of the fabrication techniques used in production of tungsten fiber reinforced superalloys (TFRS), their most significant properties, and their potential applications in the hot section components of gas turbine engines. Emphasis is given the development of airfoil-fabrication technology, with a view to the production of TFRS turbine blades, and attention is given the first-generation TFRS material, a tungsten alloy fiber/FeCrAlY composite currently under evaluation. Detailed properties, design criteria and cost data are presented for this material. Among the properties covered are stress-rupture strength, high and low cycle fatigue, thermal fatigue, impact strength, oxidation and corrosion and thermal conductivity.

  17. Fracture Analysis of Particulate Reinforced Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Min, James B.; Cornie, James A.

    2013-01-01

    A fracture analysis of highly loaded particulate reinforced composites was performed using laser moire interferometry to measure the displacements within the plastic zone at the tip of an advancing crack. Ten castings were made of five different particulate reinforcement-aluminum alloy combinations. Each casting included net-shape specimens which were used for the evaluation of fracture toughness, tensile properties, and flexure properties resulting in an extensive materials properties data. Measured fracture toughness range from 14.1 MPa for an alumina reinforced 356 aluminum alloy to 23.9 MPa for a silicon carbide reinforced 2214 aluminum alloy. For the combination of these K(sub Ic) values and the measured tensile strengths, the compact tension specimens were too thin to yield true plane strain K(sub Ic) values. All materials exhibited brittle behavior characterized by very small tensile ductility suggesting that successful application of these materials requires that the design stresses be below the elastic limit. Probabilistic design principles similar to those used with ceramics are recommended when using these materials. Such principles would include the use of experimentally determined design allowables. In the absence of thorough testing, a design allowable stress of 60 percent of the measured ultimate tensile stress is recommended.

  18. Fibre-reinforced materials.

    PubMed

    Brown, D

    2000-11-01

    This paper considers the role of fibres in the reinforcement of composite materials, and the significance of the form the fibre takes and the material from which it is made. The current dental applications of fibre reinforcement, including dental cements and splints, fibres made into structures for use in composites, denture bases and the contemporary use of fibres in fixed partial dentures, are reviewed. Their role in biomedical implants is surveyed and their future forecast. PMID:11218597

  19. Reinforcement learning in scheduling

    NASA Technical Reports Server (NTRS)

    Dietterich, Tom G.; Ok, Dokyeong; Zhang, Wei; Tadepalli, Prasad

    1994-01-01

    The goal of this research is to apply reinforcement learning methods to real-world problems like scheduling. In this preliminary paper, we show that learning to solve scheduling problems such as the Space Shuttle Payload Processing and the Automatic Guided Vehicle (AGV) scheduling can be usefully studied in the reinforcement learning framework. We discuss some of the special challenges posed by the scheduling domain to these methods and propose some possible solutions we plan to implement.

  20. The substitutability of reinforcers

    PubMed Central

    Green, Leonard; Freed, Debra E.

    1993-01-01

    Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportion. At the center of the continuum are reinforcers that are independent with respect to each other; consumption of one has no influence on consumption of another. Psychological research and analyses in terms of substitutability employ standard operant conditioning paradigms in which humans and nonhumans choose between alternative reinforcers. The range of reinforcer interactions found in these studies is more readily accommodated and predicted when behavior-analytic models of choice consider issues of substitutability. New insights are gained into such areas as eating and drinking, electrical brain stimulation, temporal separation of choice alternatives, behavior therapy, drug use, and addictions. Moreover, the generalized matching law (Baum, 1974) gains greater explanatory power and comprehensiveness when measures of substitutability are included. PMID:16812696