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Sample records for powder metallurgy compacts

  1. Active Thermography for the Detection of Defects in Powder Metallurgy Compacts

    SciTech Connect

    Benzerrouk, Souheil; Ludwig, Reinhold; Apelian, Diran

    2007-03-21

    Active thermography is an established NDE technique that has become the method of choice in many industrial applications which require non-contact access to the parts under test. Unfortunately, when conducting on-line infrared (IR) inspection of powder metallic compacts, complications can arise due the generally low emissivity of metals and the thermally noisy environment typically encountered in manufacturing plants. In this paper we present results of an investigation that explores the suitability of active IR imaging of powder metallurgy compacts for the detection of surface and sub-surface defects in the pre-sinter state and in an on-line manufacturing setting to ensure complete quality assurance. Additional off-line tests can be carried out for statistical quality analyses. In this research, the IR imaging of sub-surface defects is based on a transient instrumentation approach that relies on an electric control system which synchronizes and monitors the thermal response due to an electrically generated heat source. Preliminary testing reveals that this newly developed pulsed thermography system can be employed for the detection of subsurface defects in green-state parts. Practical measurements agree well with theoretical predictions. The inspection approach being developed can be used for the testing of green-state compacts as they exit the compaction press at speeds of up to 1,000 parts per hour.

  2. Active Thermography for the Detection of Defects in Powder Metallurgy Compacts

    NASA Astrophysics Data System (ADS)

    Benzerrouk, Souheil; Ludwig, Reinhold; Apelian, Diran

    2007-03-01

    Active thermography is an established NDE technique that has become the method of choice in many industrial applications which require non-contact access to the parts under test. Unfortunately, when conducting on-line infrared (IR) inspection of powder metallic compacts, complications can arise due the generally low emissivity of metals and the thermally noisy environment typically encountered in manufacturing plants. In this paper we present results of an investigation that explores the suitability of active IR imaging of powder metallurgy compacts for the detection of surface and sub-surface defects in the pre-sinter state and in an on-line manufacturing setting to ensure complete quality assurance. Additional off-line tests can be carried out for statistical quality analyses. In this research, the IR imaging of sub-surface defects is based on a transient instrumentation approach that relies on an electric control system which synchronizes and monitors the thermal response due to an electrically generated heat source. Preliminary testing reveals that this newly developed pulsed thermography system can be employed for the detection of subsurface defects in green-state parts. Practical measurements agree well with theoretical predictions. The inspection approach being developed can be used for the testing of green-state compacts as they exit the compaction press at speeds of up to 1,000 parts per hour.

  3. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-05

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of ternary mixtures consisting of: Ni powder, Cu powder, and Al powder, Ni powder, Cr powder, and Al powder; Ni powder, W powder and Al powder; Ni powder, V powder, and Al powder; Ni powder, Mo powder, and Al powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  4. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-19

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  5. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-28

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  6. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-05-10

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  7. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-14

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  8. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  9. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-01-25

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  10. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goval, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-06-07

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  11. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  12. Powder metallurgy in 1995

    SciTech Connect

    White, D.G.

    1995-08-01

    The powder metallurgy industry has enjoyed extraordinary growth during the last three years, based on progress in materials, processes, and equipment. Total metal powder shipments increased 18% in 1994 to 426,050 tons. For the first time, North American iron powder shipments went beyond 338,000 tons in 1994, a 17.4% increase over 1993. The copper and copper-base powder markets in 1994 reached 23,000 tons, growing slightly less than 3% over 1993. The parts segment of this market reached 19,670 tons, almost flat with 1993 because of the sharply rising price of copper on world commodity markets. This article will discuss advances in steel powders and processing, the range of iron powder applications, advanced particulate materials, equipment improvements, and standards development.

  13. Aluminum powder metallurgy processing

    NASA Astrophysics Data System (ADS)

    Flumerfelt, Joel Fredrick

    In recent years, the aluminum powder industry has expanded into non-aerospace applications. However, the alumina and aluminum hydroxide in the surface oxide film on aluminum powder require high cost powder processing routes. A driving force for this research is to broaden the knowledge base about aluminum powder metallurgy to provide ideas for fabricating low cost aluminum powder components. The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization commercial inert gas atomization and gas atomization reaction synthesis (GARS). The commercial atomization methods are bench marks of current aluminum powder technology. The GARS process is a laboratory scale inert gas atomization facility. A benefit of using pure aluminum powders is an unambiguous interpretation of the results without considering the effects of alloy elements. A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  14. Modern developments in powder metallurgy

    SciTech Connect

    Aqua, E.N.; Whitman, C.I.

    1984-01-01

    This book presents the papers given at a conference on metal powders. Topics considered at the conference included sintering fundamentals, liquid phase and activated sintering, stainless steels, copper-base powder metallurgy, aluminium alloys, refractory metals, carbides, cutting tools, friction, wear, and powder production.

  15. Densification of powder metallurgy billets by a roll consolidation technique

    NASA Technical Reports Server (NTRS)

    Sellman, W. H.; Weinberger, W. R.

    1973-01-01

    Container design is used to convert partially densified powder metallurgy compacts into fully densified slabs in one processing step. Technique improves product yield, lowers costs and yields great flexibility in process scale-up. Technique is applicable to all types of fabricable metallic materials that are produced from powder metallurgy process.

  16. Metallography of powder metallurgy materials

    SciTech Connect

    Lawley, Alan; Murphy, Thomas F

    2003-12-15

    The primary distinction between the microstructure of an ingot metallurgy/wrought material and one fabricated by the powder metallurgy route of pressing followed by sintering is the presence of porosity in the latter. In its various morphologies, porosity affects the mechanical, physical, chemical, electrical and thermal properties of the material. Thus, it is important to be able to characterize quantitatively the microstructure of powder metallurgy parts and components. Metallographic procedures necessary for the reliable characterization of microstructures in powder metallurgy materials are reviewed, with emphasis on the intrinsic challenges presented by the presence of porosity. To illustrate the utility of these techniques, five case studies are presented involving powder metallurgy materials. These case studies demonstrate problem solving via metallography in diverse situations: failure of a tungsten carbide-coated precipitation hardening stainless steel, failure of a steel pump gear, quantification of the degree of sinter (DOS), simulation of performance of a porous filter using automated image analysis, and analysis of failure in a sinter brazed part assembly.

  17. Electrostatic Detection of Density Variations in Green-State Powder Metallurgy Compacts

    NASA Astrophysics Data System (ADS)

    Leuenberger, Georg; Ludwig, Reinhold

    2003-03-01

    Producing P/M compacts is generally a low-cost, high-volume manufacturing effort with very special quality assurance requirements. When considering the three basic P/M steps of mixing, compacting, and sintering, it is the compaction process producing the green-state parts that offer the highest pay-off for quality control through nondestructive evaluation (NDE) techniques. A detection of compacting-related problems in the green-state samples permits early process intervention, and thus prevents the creation of potentially significant numbers of faulty parts. Work at WPI currently has concentrated on extending the previously developed method for crack detections to measure density variations within the parts. In this paper a physical model and a mathematical formulation are reported that are capable of relating green-state density to electric conductivity for various lubricant concentrations. Electrostatic measurements of cylindrical compacts have so far confirmed the theoretical model assumptions. Specifically, the green-state conductivity increases as the sample density increases up to approximately 6.9 - 7.0 g/ccm. Any further density increase results in a decrease in conductivity. Preliminary measurements with a range of cylindrical samples support the theoretical model.

  18. Aluminum powder metallurgy processing

    SciTech Connect

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  19. Overview of conventional powder metallurgy processing

    SciTech Connect

    Clapp, D.

    1995-08-01

    Powder metallurgy (P/M) offers designers and users a versatile and efficient method of producing parts and components. The process is versatile because it can be used for simple as well as complex shapes, and a full range of chemical, physical, and mechanical properties is possible. P/M is efficient because it produces moderate to high-volume net or near-net shapes, with almost no raw material loss. In general, the process has the potential to improve performance through uniform properties, fine grain structures, and chemical homogeneity. The conventional powder metallurgy process consists of three main steps--powder mixing, compacting, and sintering. These are typically followed by other operations, such as infiltration, coining, or machining.

  20. New developments in powder metallurgy

    SciTech Connect

    1995-09-01

    This article highlights some of the papers presented at the 1995 International Conference on Powder Metallurgy and Particulate Materials sponsored by the Metal Powder Industries Federation May 14--17, 1995, in Seattle. The first truly new process to produce WC-Co powders in the industry`s 70-yr history was described. A new binder with higher resistivity and greater compressibility than earlier binders has improved the performance of microencapsulated powders in both electrical and structural applications. Nitrogen is added under high pressure to some stainless steel alloys to achieve high strength, but this can be expensive because of the equipment required to melt the steel under pressure. A mathematical model was described for the densification of prealloyed powders by supersolidus liquid phase sintering, as a function of process parameters such as temperature, heating rate, liquid-wetting behavior, powder microstructure via liquid nucleation sites, mean liquid film thickness, and grain size. Many secondary processes are used to compress and form powder metal components to full density after sintering. It was suggested that ausforming--forming at temperatures above the martensitic start temperature, but below temperatures that could allow significant diffusion--could produce exceptionally tough, hard surfaces combined with nearly full density. Stainless steels made from prealloyed powders typically have had poor corrosion resistance. It may be that this poor performance is a result of high oxygen content in the stainless steel powders.

  1. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-10-21

    A strengthened, biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed, compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: Ni, Ag, Ag--Cu, Ag--Pd, Ni--Cu, Ni--V, Ni--Mo, Ni--Al, Ni--Cr--Al, Ni--W--Al, Ni--V--Al, Ni--Mo--Al, Ni--Cu--Al; and at least one fine metal oxide powder; the article having a grain size which is fine and homogeneous; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  2. A major advance in powder metallurgy

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; Stiglich, Jacob J., Jr.; Kaplan, Richard B.; Tuffias, Robert H.

    1991-01-01

    Ultramet has developed a process which promises to significantly increase the mechanical properties of powder metallurgy (PM) parts. Current PM technology uses mixed powders of various constituents prior to compaction. The homogeneity and flaw distribution in PM parts depends on the uniformity of mixing and the maintenance of uniformity during compaction. Conventional PM fabrication processes typically result in non-uniform distribution of the matrix, flaw generation due to particle-particle contact when one of the constituents is a brittle material, and grain growth caused by high temperature, long duration compaction processes. Additionally, a significant amount of matrix material is usually necessary to fill voids and create 100 percent dense parts. In Ultramet's process, each individual particle is coated with the matrix material, and compaction is performed by solid state processing. In this program, Ultramet coated 12-micron tungsten particles with approximately 5 wt percent nickel/iron. After compaction, flexure strengths were measured 50 percent higher than those achieved in conventional liquid phase sintered parts (10 wt percent Ni/Fe). Further results and other material combinations are discussed.

  3. Advanced powder metallurgy aluminum alloys and composites

    NASA Technical Reports Server (NTRS)

    Lisagor, W. B.; Stein, B. A.

    1982-01-01

    The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

  4. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  5. Powder-Metallurgy Process And Product

    NASA Technical Reports Server (NTRS)

    Paris, Henry G.

    1988-01-01

    Rapid-solidification processing yields alloys with improved properties. Study undertaken to extend favorable property combinations of I/M 2XXX alloys through recently developed technique of rapid-solidification processing using powder metallurgy(P/M). Rapid-solidification processing involves impingement of molten metal stream onto rapidly-spinning chill block or through gas medium using gas atomization technique.

  6. Powder metallurgy repair of turbine components

    SciTech Connect

    Ellison, K.A.; Lowden, P.; Liburdi, J. )

    1994-01-01

    An advanced powder metallurgy repair process called Liburdi Powder Metallurgy (LPM) has been developed for the repair, overlay or joining of nickel and cobalt-based high-temperature alloys. This process involves mechanical cleaning, followed by the application and consolidation of a filler metal powder, which has substantially the same composition as the base metal, and producer joints with mechanical properties similar to those of the parent material. While previously activated braze or wide-gap'' repair processes have been limited to clearances of approximately 1 mm, the LPM technique has the ability to bridge larger gaps of over 5 mm. In addition, the LPM joints contain significantly lower concentrations of melting point depressants such as silicon and boron than conventional wide-gap repair techniques and exhibit superior microstructural features. The characteristics and typical applications of the LPM process for blade and vane repairs are highlighted and the results of laboratory and engine tests are discussed.

  7. Powder metallurgy design manual, 2nd edition

    SciTech Connect

    1995-12-31

    This book is the most concise and comprehensive book of its kind on powder metallurgy (P/M) technology for both component design and application. Completely updated from the previous edition, this valuable reference gives an entirely new coverage on metal injection molding (MIM) and powder forging (P/F) with applicable case histories. There is revised information on P/M compared with other technologies, prototyping, and properties and characteristics of alloys, powders and P/M materials. In addition there`s expanded data on sintering including liquid phase processing and hardening.

  8. Powder metallurgy technology of NiTi shape memory alloy

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, J. M.; Maziarz, W.; Czeppe, T.; Lityńska, L.; Nowacki, W. K.; Gadaj, S. P.; Luckner, J.; Pieczyska, E. A.

    2008-05-01

    Powder metallurgy technology was elaborated for consolidation of shape memory NiTi powders. The shape memory alloy was compacted from the prealloyed powder delivered by Memry SA. The powder shows Ms = 10°C and As = -34°C as results from DSC measurements. The samples were hot pressed in the as delivered spherical particle's state. The hot compaction was performed in a specially constructed vacuum press, at temperature of 680°C and pressure of 400 MPa. The alloy powder was encapsulated in copper capsules prior to hot pressing to avoid oxidation or carbides formation. The alloy after hot vacuum compaction at 680°C (i.e. within the B2 NiTi stability range) has shown similar transformation range as the powder. The porosity of samples compacted in the as delivered state was only 1%. The samples tested in compression up to ɛ = 0.06 have shown partial superelastic effect due to martensitic reversible transform- ation which started at the stress above 300 MPa and returned back to ɛ = 0.015 after unloading. They have shown also a high ultimate compression strength of 1600 MPa. Measurements of the samples temperature changes during the process allowed to detect the temperature increase above 12°C for the strain rate 10-2 s-1 accompanied the exothermic martensite transformation during loading and the temperature decrease related to the reverse endothermic transformation during unloading.

  9. Evaluation of powder metallurgy superalloy disk materials

    NASA Technical Reports Server (NTRS)

    Evans, D. J.

    1975-01-01

    A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

  10. Volume 7. Copper base powder metallurgy

    SciTech Connect

    Taubenblat, P.W.

    1980-01-01

    This book is based on a series of lectures on copper and copper base P/M materials sponsored by the Metal Powder Industries Federation. It covers recent developments in the fields of copper powder metallurgy and offers a comprehensive survey of copper and copper-base P/M materials. It begins with a chapter on the production of copper and copper alloy powders followed by discussions of specific applications of P/M materials in bronzes and bearings, in brasses and nickel silvers, and in electrically conductive parts. Also discussed are iron composition containing copper, copper-based alloys for infiltration of iron and other special copper-base alloys. It concludes with chapters on consolidation, sintering and review of specifications.

  11. Low-Cobalt Powder-Metallurgy Superalloy

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1986-01-01

    Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

  12. Ti Multicomponent Alloy Bulks by Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Zhang, Kuibao; Wen, Guanjun; Dai, Hongchuan; Teng, Yuancheng; Li, Yuxiang

    2014-10-01

    In this study, CrCuFeMnMo0.5Ti multicomponent alloy bulks were prepared by powder metallurgy of mechanical alloying and sintering. A simple body-centered cubic (bcc) solid solution was prepared after 40 h ball milling of the raw CrCuFeMnMo0.5Ti metallic powder. Particles of the alloyed powder are in microsized structures, which are actually a soft agglomeration of lamellar grains with thicknesses less than 1 μm. Meanwhile, the lamellar granules are consisted of nanosized grains under rigid cold welding. The 80-h ball-milled powder was consolidated by cold pressing and subsequent sintering at 800°C. The observed main phase in the consolidated sample after milling for 80 h is still a bcc solid solution. The solidified sample of 80-h ball-milled powder exhibits a Vickers hardness of 468 HV, which is much higher than 171 HV of the counterpart prepared from the raw metallic powder.

  13. Advances in powder metallurgy - 1991. Vol. 5 - P/M materials; Proceedings of the Powder Metallurgy Conference and Exhibition, Chicago, IL, June 9-12, 1991

    SciTech Connect

    Pease, L.F. III; Sansoucy, R.J.

    1991-01-01

    The present volume powder metallurgy materials discusses the state of the PM industry, a metallurgical evaluation of new steel powders, design criteria for the manufacturing of low-alloy steel powders, and homogenization processing of a PM maraging steel. Attention is given to the corrosion resistance of full density sintered 316 SS, the performance characteristics of a new sinter-hardening low-alloy steel, wear performance of compositions made by low alloy iron/high alloy powder mixtures, and the strengthening of an AISI 1020 steel by aluminum-microalloying during liquid dynamic compaction. Topics addressed include the influence of alloying on the properties of water-atomized copper powders, fundamentals of high pressure gas atomization process control, advanced sensors and process control of gas atomization, and bimetallic tubulars via spray forming. Also discussed are factors affecting the delamination of PM molybdenum during stamping, applications of powder metallurgy molybdenum in the 1990s, and powder processing of high-temperature oxides.

  14. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.

    2001-01-01

    A biaxially textured alloy article comprises Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacted and heat treated, then rapidly recrystallized to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  15. [Hygienic evaluation of risk factors on powder metallurgy production].

    PubMed

    2011-01-01

    Complex hygienic, clinical, sociologic and epidemiologic studies revealed reliable relationship between work conditions and arterial hypertension, locomotory system disorders, monocytosis in powder metallurgy production workers. Findings are more probable cardiovascular and respiratory diseases, digestive tract diseases due to influence of lifestyle factors. PMID:22288182

  16. One step HIP canning of powder metallurgy composites

    NASA Technical Reports Server (NTRS)

    Juhas, John J. (Inventor)

    1990-01-01

    A single step is relied on in the canning process for hot isostatic pressing (HIP) powder metallurgy composites. The binders are totally removed while the HIP can of compatible refractory metal is sealed at high vacuum and temperature. This eliminates outgassing during hot isostatic pressing.

  17. Powder-metallurgy superalloy strengthened by a secondary gamma phase.

    NASA Technical Reports Server (NTRS)

    Kotval, P. S.

    1971-01-01

    Description of experiments in which prealloyed powders of superalloy compositions were consolidated by extrusion after the strengthening by precipitation of a body-centered tetragonal gamma secondary Ni3 Ta phase. Thin foil electron microscopy showed that the mechanical properties of the resultant powder-metallurgy product were correlated with its microstructure. The product exhibited high strength at 1200 F without loss of ductility, after thermomechanical treatment and aging.

  18. Near-Net Shape Powder Metallurgy Rhenium Thruster

    NASA Technical Reports Server (NTRS)

    Leonhardt, Todd; Hamister, Mark; Carlen, Jan C.; Biaglow, James; Reed, Brian

    2001-01-01

    This paper describes the development of a method to produce a near-net shape (NNS) powder metallurgy (PM) rhenium combustion chamber of the size 445 N (100 lbf) used in a high performance liquid apogee engine. These engines are used in low earth Orbit and geostationary orbit for satellite positioning systems. The developments in near-net shape powder metallurgy rhenium combustion chambers reported in this paper will reduce manufacturing cost of the rhenium chambers by 25 percent, and reduce the manufacturing time by 30 to 40 percent. The quantity of rhenium metal powder used to produce a rhenium chamber is reduced by approximately 70 percent and the subsequent reduction in machining schedule and costs is nearly 50 percent.

  19. A powder metallurgy approach for production of innovative radioactive waste forms

    SciTech Connect

    Keiser, D.D. Jr.; Crawford, D.C.; Bhaduri, S.

    1997-07-01

    The feasibility of producing a single metal-matrix composite form rather than two separate forms consisting of a cast metal alloy ingot (such as Type 316SS + Zr) and a ceramic glass-bonded zeolite Na{sub 12}(AlO{sub 2}){sub 12}(SiO{sub 2}){sub 12} has been demonstrated. This powder metallurgy approach consists of mixing the powder of the two separate waste forms together followed by compaction by hot isostatic pressing. Such a radioactive waste form would have the potential advantages of reducing the total waste volume, good thermal conductivity, stability, and surfaces with limited oxide layer formation. 5 refs., 8 figs., 2 tabs.

  20. Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

    NASA Technical Reports Server (NTRS)

    Royster, D. M.; Thomas, J. R.; Singleton, O. R.

    1993-01-01

    Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

  1. Milling and Drilling Evaluation of Stainless Steel Powder Metallurgy Alloys

    SciTech Connect

    Lazarus, L.J.

    2001-12-10

    Near-net-shape components can be made with powder metallurgy (PM) processes. Only secondary operations such as milling and drilling are required to complete these components. In the past and currently production components are made from powder metallurgy (PM) stainless steel alloys. process engineers are unfamiliar with the difference in machining properties of wrought versus PM alloys and have had to make parts to develop the machining parameters. Design engineers are not generally aware that some PM alloy variations can be furnished with machining additives that greatly increase tool life. Specimens from a MANTEC PM alloy property study were made available. This study was undertaken to determine the machining properties of a number of stainless steel wrought and PM alloys under the same conditions so that comparisons of their machining properties could be made and relative tool life determined.

  2. Prediction of Elastic Behavior of Sintered Metal Powder from the Ultrasonic Velocities of Green Compacts

    NASA Astrophysics Data System (ADS)

    Phani, K. K.; Sanyal, Dipayan

    2008-04-01

    A novel procedure for the estimation of the elastic properties of the sintered and compacted metal powders from the ultrasonic velocities of the green compact alone has been proposed in this article. The methodology has been validated for sintered iron powder and copper powder compacts as well as for consolidated silver powder compacts of various processing histories, powder sizes, and pore morphology. The predicted elastic moduli, including the derived modulus (Poisson’s ratio), are found to be in reasonably good agreement with the measured data reported in the literature. The proposed method can be developed as a potent tool for the quantitative nondestructive evaluation (QNDE) of powder metallurgy products.

  3. Advanced powder metallurgy aluminum alloys via rapid solidification technology

    NASA Technical Reports Server (NTRS)

    Ray, R.

    1984-01-01

    Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

  4. Microstructure and Aging of Powder-Metallurgy Al Alloys

    NASA Technical Reports Server (NTRS)

    Blackburn, L. B.

    1987-01-01

    Report describes experimental study of thermal responses and aging behaviors of three new aluminum alloys. Alloys produced from rapidly solidified powders and contain 3.20 to 5.15 percent copper, 0.24 to 1.73 percent magnesium, 0.08 to 0.92 percent iron, and smaller amounts of manganese, nickel, titanium, silicon, and zinc. Peak hardness achieved at lower aging temperatures than with standard ingot-metallurgy alloys. Alloys of interest for automobile, aircraft, and aerospace applications.

  5. Mesoscale Simulations of Powder Compaction

    NASA Astrophysics Data System (ADS)

    Lomov, Ilya.; Fujino, Don; Antoun, Tarabay; Liu, Benjamin

    2009-12-01

    Mesoscale 3D simulations of shock compaction of metal and ceramic powders have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating a well-characterized shock compaction experiment of a porous ductile metal. Simulation results using the Steinberg material model and handbook values for solid 2024 aluminum showed good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not as well studied as metals, so a simple material model for solid ceramic (tungsten carbide) has been calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powders have been performed and showed good agreement with experimental data. The numerical shock wave profile has same character and thickness as that measured experimentally using VISAR. The numerical results show reshock states above the single-shock Hugoniot line as observed in experiments. We found that for good quantitative agreement with experiments 3D simulations are essential.

  6. Shock compaction of molybdenum powder

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.

    1983-01-01

    Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.

  7. Application of superalloy powder metallurgy for aircraft engines

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    In the last decade, Government/Industry programs have advanced powder metallurgy-near-net-shape technology to permit the use of hot isostatic pressed (HIP) turbine disks in the commercial aircraft fleet. These disks offer a 30% savings of input weight and an 8% savings in cost compared in cast-and-wrought disks. Similar savings were demonstrated for other rotating engine components. A compressor rotor fabricated from hot-die-forged-HIP superalloy billets revealed input weight savings of 54% and cost savings of 35% compared to cast-and-wrought parts. Engine components can be produced from compositions such as Rene 95 and Astroloy by conventional casting and forging, by forging of HIP powder billets, or by direct consolidation of powder by HIP. However, each process produces differences in microstructure or introduces different defects in the parts. As a result, their mechanical properties are not necessarily identical. Acceptance methods should be developed which recognize and account for the differences.

  8. Device for preparing combinatorial libraries in powder metallurgy.

    PubMed

    Yang, Shoufeng; Evans, Julian R G

    2004-01-01

    This paper describes a powder-metering, -mixing, and -dispensing mechanism that can be used as a method for producing large numbers of samples for metallurgical evaluation or electrical or mechanical testing from multicomponent metal and cermet powder systems. It is designed to make use of the same commercial powders that are used in powder metallurgy and, therefore, to produce samples that are faithful to the microstructure of finished products. The particle assemblies produced by the device could be consolidated by die pressing, isostatic pressing, laser sintering, or direct melting. The powder metering valve provides both on/off and flow rate control of dry powders in open capillaries using acoustic vibration. The valve is simple and involves no relative movement, avoiding seizure with fine powders. An orchestra of such valves can be arranged on a building platform to prepare multicomponent combinatorial libraries. As with many combinatorial devices, identification and evaluation of sources of mixing error as a function of sample size is mandatory. Such an analysis is presented. PMID:15244416

  9. Properties of porous magnesium prepared by powder metallurgy.

    PubMed

    Čapek, Jaroslav; Vojtěch, Dalibor

    2013-01-01

    Porous magnesium-based materials are biodegradable and promising for use in orthopaedic applications, but their applications are hampered by their difficult fabrication. This work reports the preparation of porous magnesium materials by a powder metallurgy technique using ammonium bicarbonate as spacer particles. The porosity of the materials depended on the amount of ammonium bicarbonate and was found to have strong negative effects on flexural strength and corrosion behaviour. However, the flexural strength of materials with porosities of up to 28 vol.% was higher than the flexural strength of non-metallic biomaterials and comparable with that of natural bone. PMID:25428111

  10. Mesoscale simulations of powder compaction

    NASA Astrophysics Data System (ADS)

    Lomov, Ilya; Antoun, Tarabay; Liu, Benjamin

    2009-06-01

    Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to experimental match compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show evidence of hard-to-explain reshock states above the single-shock Hugoniot line, which have also been observed in the experiments. We found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations, since 2D results tend to underpredict stress levels for high-porosity powders regardless of material properties. We developed a process to extract macroscale information for the simulation which can be directly used in calibration of continuum model for heterogeneous media.

  11. Influence of Sintering under Nitrogen Atmosphere on Microstructures of Powder Metallurgy Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    García, C.; Martin, F.; Blanco, Y.; de Tiedra, M. P.; Aparicio, M. L.

    2009-02-01

    Duplex stainless steels (SS) obtained through powder metallurgy (PM) from austenitic AISI 316L and ferritic AISI 430L powders were mixed in different amounts to obtain a biphasic structure with an austenite/ferrite ratio of 50/50, 65/35, and 85/15. Prepared powders were compacted at 750 MPa and sintered in N2-H2 (95 pct-5 pct) at 1250 °C for 1 hour. Some samples sintered in vacuum were taken as references. Optical metallography, X-ray diffraction, and scanning electron microscopy/energy dispersive analysis of X-rays were used for microstructural characterization. Powder metallurgy base materials, AISI 430L and 316L, showed a single lamellar constituent after sintering in nitrogen. A mixed constituent was identified in PM duplex SS sintered in nitrogen and in vacuum. However, coarse and fine lamellar constituents were only present in PM duplex SS sintered in nitrogen. The effects of annealing solution heat treatment (1150 °C) on microstructures were evaluated. Homogeneous structures were obtained for the PM base materials, while for PM duplex SS, annealing dissolved lamellar constituents but mixed constituent were still present.

  12. Ceramic Inclusions in Powder Metallurgy Disk Alloys: Characterization and Modeling

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.

    2001-01-01

    Powder metallurgy alloys are increasingly used in gas turbine engines, especially in turbine disk applications. Although powder metallurgy materials have many advantages over conventionally cast and wrought alloys (higher strength, higher temperature capability, etc.), they suffer from the rare occurrence of ceramic defects (inclusions) that are inherent to the powder atomization process. These inclusions can have a potentially large detrimental effect on the durability of individual components. An inclusion in a high stress location can act as a site for premature crack initiation and thereby considerably reduce the fatigue life. Because these inclusions are exceedingly rare, they typically do not reveal themselves in the process of characterizing the material for a particular application (the cumulative volume of the test bars in a fatigue life characterization is typically on the order of a single actual component). Ceramic inclusions have, however, been found to be the root cause of a number of catastrophic engine failures. To investigate the effect of these inclusions in detail, we have undertaken a study where known populations of ceramic particles, whose composition and morphology are designed to mimic the "natural" inclusions, are added to the precursor powder. Surface-connected inclusions have been found to have a particularly large detrimental effect on fatigue life; therefore, the quantity of ceramic "seeds" added is calculated to ensure that a minimum number will intersect the surface of the fatigue test bars. Because the ceramic inclusions are irregularly shaped and have a tendency to break up in the process of extrusion and forging, a method of calculating the probability of occurrence and expected intercepted surface area was needed. We have developed a Monte Carlo simulation to determine the distributions of these parameters and have verified the simulated results with observations of ceramic inclusions found in macroscopic slices from extrusions and forgings. Fatigue specimens have been machined from Udimet 720 (a powder metallurgy superalloy) forgings, to determine the effects of the inclusions on fatigue life. The ultimate goal of this study will be to use probabilistic methods to determine the reliability detriment that can be attributed to these ceramic inclusions. This work has been supported by the Ultra Safe and Ultra- Efficient Engine Technologies programs.

  13. DC Plasma Technology Applied to Powder Metallurgy: an Overview

    NASA Astrophysics Data System (ADS)

    N. Klein, A.; P. Cardoso, R.; C. Pavanati, H.; Binder, C.; M. Maliska, A.; Hammes, G.; Fusao, D.; Seeber, A.; F. Brunatto, S.; L. R. Muzart, J.

    2013-01-01

    DC plasma is a very promising technology for processing different materials, and is becoming especially interesting when low environmental impact and high-performance treatments are needed. Some of the intrinsic characteristics of DC plasma technology, which make it suitable for powder metallurgy (PM) and powder injection molding (PIM) parts production, are low-pressure processing and plasma environment high reactivity. Moreover it can be considered as a highly competitive green technology. In this work, an overview of some of the important DC plasma techniques applied to PM and PIM parts processing is presented. Emphasis is given to the descriptions of the main characteristics and the technique potentials of plasma-assisted nitriding, plasma-assisted thermal debinding, plasma-assisted sintering, and simultaneously plasma-assisted sintering and surface alloying. The aspects presented and discussed in this paper indicate that DC plasma processes are promising and competitive techniques for PM and PIM parts processing.

  14. Ceramic Inclusions In Powder Metallurgy Disk Alloys: Characterization and Modeling

    NASA Technical Reports Server (NTRS)

    Bonacuse, Pete; Kantzos, Pete; Telesman, Jack

    2002-01-01

    Powder metallurgy alloys are increasingly used in gas turbine engines, especially as the material chosen for turbine disks. Although powder metallurgy materials have many advantages over conventionally cast and wrought alloys (higher strength, higher temperature capability, etc.), they suffer from the rare occurrence of ceramic defects (inclusions) that arise from the powder atomization process. These inclusions can have potentially large detrimental effect on the durability of individual components. An inclusion in a high stress location can act as a site for premature crack initiation and thereby considerably reduce the fatigue life. Because these inclusions are exceedingly rare, they usually don't reveal themselves in the process of characterizing the material for a particular application (the cumulative volume of the test bars in a fatigue life characterization is typically on the order of a single actual component). Ceramic inclusions have, however, been found to be the root cause of a number of catastrophic engine failures. To investigate the effect of these inclusions in detail, we have undertaken a study where a known population of ceramic particles, whose composition and morphology are designed to mimic the 'natural' inclusions, are added to the precursor powder. Surface connected inclusions have been found to have a particularly large detrimental effect on fatigue life, therefore the volume of ceramic 'seeds' added is calculated to ensure that a minimum number will occur on the surface of the fatigue test bars. Because the ceramic inclusions are irregularly shaped and have a tendency to break up in the process of extrusion and forging, a method of calculating the probability of occurrence and expected intercepted surface and embedded cross-sectional areas were needed. We have developed a Monte Carlo simulation to determine the distributions of these parameters and have verified the simulated results with observations of ceramic inclusions found in macro slices from extrusions and forgings. The ultimate goal of this study will be to use probabilistic methods to determine the reliability detriment that can be attributed to these ceramic inclusions.

  15. Ti matrix syntactic foam fabricated by powder metallurgy: Particle breakage and elastic modulus

    NASA Astrophysics Data System (ADS)

    Xue, Xiaobing; Zhao, Yuyuan

    2011-02-01

    Titanium matrix syntactic foams have potential for orthopedic applications because of their good biocompatibility, corrosion resistance and ability of varying the elastic modulus. This paper studies the fabrication of Ti matrix syntactic foams embedded with ceramic microspheres (CMs) by a powder metallurgy method. The percentage of the crushed CMs during compaction was measured by the volume measurement and water absorption methods, and the elastic modulus of the Ti matrix syntactic foam was measured by compression tests. The effects of the Ti volume percentage and the compaction pressure on the percentage of crushed CMs and the elastic modulus were studied. For a given Ti volume percentage, the percentage of crushed CMs increases with increasing compaction pressure; for a given compaction pressure, the percentage of crushed CMs decreases with increasing Ti volume percentage. At a compaction pressure lower than 100 MPa, the elastic modulus increases with increasing Ti volume percentage and compaction pressure; at a compaction pressure above 100 MPa, further increases in Ti volume percentage and compaction pressure decrease the elastic modulus.

  16. Composite Ferrous Powder Metallurgy Structures: Mechanical Properties and Stress Analysis

    NASA Astrophysics Data System (ADS)

    Ahmed, M. N.; Vedula, M.; Koczak, M. J.

    1990-11-01

    Macrocomposite mechanics modeling is done for asymmetrical triplex structures. Relative parameters are obtained for the location of the centroid and the moment of inertia of triplex structures. The general analysis described can be applied to the special cases of symmetrical sandwich and asymmetrical duplex structures. The stress analysis includes the effect of the residual stress, and residual stress factors are determined for the special case of asymmetricaduplex structures. The rule-of-mixtures yield strength calculation with use of the relative parameters and residual stress factors was found to correlate very well with experimental results for macrocomposite ferrous powder metallurgy (P/M) duplex, 4620 and 4660, structures. The effects of volume fraction and the variations of elastic moduli of the constituents are examined.

  17. On creep behavior in powder metallurgy 6061 Al

    SciTech Connect

    Mohamed, F.A.

    1998-01-06

    There has been a considerable interest in studying the creep characteristics of powder metallurgy (PM) Al alloys such as PM 6061 Al and PM 2124 Al. First, these alloys have been used as matrices in the development of discontinuous SiC-Al composites which have been under consideration as attractive materials for high temperature applications. Second, creep data on these alloys can be used not only to characterize the elevated temperature mechanical behavior of SiC-Al composites in terms of deformation mechanisms but also to provide a close comparison between the creep strength of a composite and its unreinforced matrix alloy. Such a comparison under similar experimental conditions may determine whether the composite is more creep resistant than the alloy. The purpose of this note is to examine the experimental results reported for PM 6061 Al in the light of the advances that have been made in rationalizing the creep behavior of Al-based solid-solution alloys.

  18. N18, powder metallurgy superalloy for disks: Development and applications

    SciTech Connect

    Guedou, J.Y.; Lautridou, J.C.; Honnorat, Y. . Materials and Processes Dept.)

    1993-08-01

    The preliminary industrial development of a powder metallurgy (PM) superalloy, designated N18, for disk applications has been completed. This alloy exhibits good overall mechanical properties after appropriate processing of the material. These properties have been measured on both isothermally forged and extruded billets, as well as on specimens cut from actual parts. The temperature capability of the alloy is about 700 C for long-term applications and approximately 750 C for short-term use because of microstructural instability. Further improvements in creep and crack propagation properties, without significant reduction in tensile strength, are possible through appropriate thermomechanical processing, which results in a large controlled grain size. Spin pit tests on subscale disks have confirmed that the N18 alloy has a higher resistance than PM Astrology and is therefore an excellent alloy for modern turbine disk applications.

  19. Phase Stability of a Powder Metallurgy Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Kantzos, P.; Telesman, Jack; Gang, Anita

    2006-01-01

    Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700 C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing gamma' precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.

  20. Powder metallurgy: Solid and liquid phase sintering of copper

    NASA Technical Reports Server (NTRS)

    Sheldon, Rex; Weiser, Martin W.

    1993-01-01

    Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

  1. Thixoforming of Stellite Powder Compacts

    NASA Astrophysics Data System (ADS)

    Hogg, S. C.; Atkinson, H. V.; Kapranos, P.

    2007-04-01

    Thixoforming involves processing metallic alloys in the semi-solid state. The process requires the microstructure to be spheroidal when part-solid and part-liquid i.e. to consist of solid spheroids surrounded by liquid. The aim of this work was to investigate whether powder compacts can be used as feedstock for thixoforming and whether the consolidating pressure in the thixoformer can be used to remove porosity from the compact. The powder compacts were made from stellite 6 and stellite 21 alloys, cobalt-based alloys widely used for e.g. manufacturing prostheses. Isothermal heat treatments of small samples in the consolidated state showed the optimum thixoforming temperature to be in the range 1340°C-1350°C for both materials. The alloys were thixoformed into graphite dies and flowed easily to fill the die. Porosity in the thixoformed components was lower than in the starting material. Hardness values at various positions along the radius of the thixoformed demonstrator component were above the specification for both alloys.

  2. Thixoforming of Stellite Powder Compacts

    SciTech Connect

    Hogg, S. C.; Atkinson, H. V.; Kapranos, P.

    2007-04-07

    Thixoforming involves processing metallic alloys in the semi-solid state. The process requires the microstructure to be spheroidal when part-solid and part-liquid i.e. to consist of solid spheroids surrounded by liquid. The aim of this work was to investigate whether powder compacts can be used as feedstock for thixoforming and whether the consolidating pressure in the thixoformer can be used to remove porosity from the compact. The powder compacts were made from stellite 6 and stellite 21 alloys, cobalt-based alloys widely used for e.g. manufacturing prostheses. Isothermal heat treatments of small samples in the consolidated state showed the optimum thixoforming temperature to be in the range 1340 deg. C-1350 deg. C for both materials. The alloys were thixoformed into graphite dies and flowed easily to fill the die. Porosity in the thixoformed components was lower than in the starting material. Hardness values at various positions along the radius of the thixoformed demonstrator component were above the specification for both alloys.

  3. Rapid Synthesis of a Near-β Titanium Alloy by Blended Elemental Powder Metallurgy (BEPM) with Induction Sintering

    NASA Astrophysics Data System (ADS)

    Jia, Mingtu; Gabbitas, Brian

    2015-10-01

    A near-β Ti-13V-11Cr-3Al alloy was produced by blended elemental powder metallurgy combining warm compaction and induction sintering. Two Ti-13V-11Cr-3Al powder compacts with different oxygen content were manufactured by mixing PREP and HDH Ti powders with Cr and AlV master alloy powders, respectively. The effect of isothermal holding time, at a sintering temperature of 1573 K (1300 °C), on pore characteristics and compositional homogeneity was investigated in this study. Pore coarsening by Ostwald ripening occurred with an increase in the isothermal holding time and Kirkendall voids were produced by a reaction between Ti and Cr. After an isothermal holding time of 10 minutes, the two sintered powder compacts had a homogeneous composition. Ti/AlV and Ti/Cr diffusion couples were used to predict the distribution of alloying elements, and the binary Ti-V, Ti-Al, and Ti-Cr interdiffusion coefficients were consistent with the distribution of alloying elements after isothermal holding. The mechanical properties of sintered powder compacts, prepared using PREP Ti powder as the raw powder, were optimized by sintered density and pore size.

  4. Method for forming biaxially textured articles by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2002-01-01

    A method of preparing a biaxially textured alloy article comprises the steps of preparing a mixture comprising Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacting the mixture, followed by heat treating and rapidly recrystallizing to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  5. Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique.

    PubMed

    Ryan, Garrett E; Pandit, Abhay S; Apatsidis, Dimitrios P

    2008-09-01

    One of the main issues in orthopaedic implant design is the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. This research reports on a multi-stage rapid prototyping technique that was successfully developed to produce porous titanium scaffolds with fully interconnected pore networks and reproducible porosity and pore size. The scaffolds' porous characteristics were governed by a sacrificial wax template, fabricated using a commercial 3D-printer. Powder metallurgy processes were employed to generate the titanium scaffolds by filling around the wax template with titanium slurry. In the attempt to optimise the powder metallurgy technique, variations in slurry concentration, compaction pressure and sintering temperature were investigated. By altering the wax design template, pore sizes ranging from 200 to 400 microm were achieved. Scaffolds with porosities of 66.8 +/- 3.6% revealed compression strengths of 104.4+/-22.5 MPa in the axial direction and 23.5 +/- 9.6 MPa in the transverse direction demonstrating their anisotropic nature. Scaffold topography was characterised using scanning electron microscopy and microcomputed tomography. Three-dimensional reconstruction enabled the main architectural parameters such as pore size, interconnecting porosity, level of anisotropy and level of structural disorder to be determined. The titanium scaffolds were compared to their intended designs, as governed by their sacrificial wax templates. Although discrepancies in architectural parameters existed between the intended and the actual scaffolds, overall the results indicate that the porous titanium scaffolds have the properties to be potentially employed in orthopaedic applications. PMID:18556060

  6. Effects of carbon and hafnium concentrations in wrought powder-metallurgy superalloys based on NASA 2B-11 alloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.

    1976-01-01

    A candidate alloy for advanced-temperature turbine engine disks, and four modifications of that alloy with various C and Hf concentrations were produced as cross-rolled disks from prealloyed powder that was hot isostatically compacted. The mechanical properties, microstructures, and phase relations of the alloys are discussed in terms of their C and Hf concentrations. A low-C and high-Hf modification of IIB-11 had the best balance of mechanical properties for service below about 750 C. Because of their finer grain sizes, none of the powder-metallurgy alloys produced had the high-temperature rupture strength of conventionally cast and wrought IIB-11.

  7. Manufacture and characterization of aluminium matrix composite using powder metallurgy route

    SciTech Connect

    Huda, D.; El Baradie, M.A.; Hashmi, M.S.J.

    1993-12-31

    The potential of Metal Matrix Composite materials for significant improvements in performance over conventional alloys has been widely recognized. Much work has been carried out in Europe and abroad to manufacture MMC materials using different techniques, e.g. Squeeze casting, Spray Co-deposition, Compocasting and Powder Metallurgy Route. The attraction of Powder Metallurgy is that it permits fabrication of high quality, complex parts to close tolerances in an economical manner. In this study the Powder Metallurgy Route was selected for the manufacture of Aluminium Matrix Composites using Al{sub 2}O{sub 3} particulate as the reinforcement element. The volume fraction of the reinforcement was varied from 10 to 40 percent. Several components were produced, by varying the sintering time and temperature. The results of compression and hardness tests are presented, together with microstructure analysis. Also the mechanical test results for Aluminium Matrix Composite produced through the Powder Metallurgy Route are compared with the results for commercially available composites.

  8. Effect of glow discharge sintering in the properties of a composite material fabricated by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Cardenas, A.; Pineda, Y.; Sarmiento Santos, A.; Vera, E.

    2016-02-01

    Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting materials were mixed in different proportions and compacted to 700MPa. Sintering stage was performed by abnormal glow discharge plasma with direct current in an inert atmosphere of argon. The process was conducted at a temperature of 1200°C±5°C with a heating rate of 100°C/min. This work shows, the effectiveness of plasma sintering process to generate the first contacts between particles and to reduce vacancies. This fact is confirmed by comparing green and sintered density of the material. The results of porosity show a decrease after plasma sintering. Wear tests showed the wear mechanisms, noting that at higher SiC contents, the wear resistance decreases due to poor matrix-reinforcement interaction and by the porosity presence which causes matrix-reinforcement sliding.

  9. Mechanical cycling effects at Fe-Mn-Si-Cr-Ni SMAs obtained by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Comčneci, R. I.; Özkal, B.; Bujoreanu, L. G.

    Specimens from Fe-Mn-Si-Cr-Ni SMA, obtained by powder metallurgy and compacted through hot rolling, were subjected to tensile loading-unloading cycles. The pseudoelastic parameters were determined based on recorded stress-strain curves, and their variation tendency with increasing the number of mechanical cycles was discussed. The gauges of tensile specimens were cut after mechanical cycling and were subjected to structural and dilatometric analysis. The structure was analyzed by XRD and SEM, aiming to reveal mechanical cycling effects. The thermomechanical response on heating, of mechanically cycled specimens, was recorded by dilatometry and revealed a tendency to enhance thermal expansion as an effect of increasing the number of cycles. The microstructural changes, induced by mechanical cycling, consisted in the stress induced formation of α' martensite.

  10. POWDER METALLURGY TiAl ALLOYS: MICROSTRUCTURES AND PROPERTIES

    SciTech Connect

    Hsiung, L

    2006-12-11

    The microstructures and properties of powder metallurgy TiAl alloys fabricated by hot extrusion of gas-atomized powder at different elevated temperatures were investigated. Microstructure of the alloy fabricated at 1150 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains and coarse ordered B2 grains. Particles of ordered hexagonal {omega} phase were also observed in some B2 grains. The alloy containing B2 grains displayed a low-temperature superplastic behavior: a tensile elongation of 310% was measured when the alloy was tested at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. Microstructure of the alloy fabricated at 1250 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains, coarse {alpha}{sub 2} grains, and lamellar ({gamma} + {alpha}{sub 2}) colonies. An observation of stacking faults associated with fine {gamma} lamellae in {alpha}{sub 2} grains reveals that the stacking fault of {alpha}{sub 2} phase plays an important role in the formation of lamellar ({gamma} + {alpha}{sub 2}) colonies. Unlike the alloy fabricated at 1150{sup o}, the alloy fabricated at 1250{sup o} displayed no low-temperature superplasticity, but a tensile elongation of 260% at 1000 C was measured. Microstructure of the alloy fabricated at 1400 C consisted of fully lamellar ({gamma} + {alpha}{sub 2}) colonies with the colony size ranging between 50 {micro}m and 100 {micro}m, in which the width of {gamma} lamella is in a range between 100 nm and 350 nm, and the width of {alpha}{sub 2} lamella is in a range between 10 nm and 50 nm. Creep behavior of the ultrafine lamellar alloy and the effects of alloying addition on the creep resistance of the fully lamellar alloy are also investigated.

  11. Compaction and Sintering of Mo Powders

    SciTech Connect

    Nunn, Stephen D; Kiggans, Jim; Bryan, Chris

    2013-01-01

    To support the development of Mo-99 production by NorthStar Medical Technologies, LLC, Mo metal powders were evaluated for compaction and sintering characteristics as they relate to Mo-100 accelerator target disk fabrication. Powders having a natural isotope distribution and enriched Mo-100 powder were examined. Various powder characteristics are shown to have an effect on both the compaction and sintering behavior. Natural Mo powders could be cold pressed directly to >90% density. All of the powders, including the Mo-100 samples, could be sintered after cold pressing to >90% density. As an example, a compacted Mo-100 disk reached 89.7% density (9.52 g/cm3) after sintering at 1000 C for 1 hr. in flowing Ar/4%H2. Higher sintering temperatures were required for other powder samples. The relationships between processing conditions and the resulting densities of consolidated Mo disks will be presented.

  12. Roller compaction of moist pharmaceutical powders.

    PubMed

    Wu, C-Y; Hung, W-L; Miguélez-Morán, A M; Gururajan, B; Seville, J P K

    2010-05-31

    The compression behaviour of powders during roller compaction is dominated by a number of factors, such as process conditions (roll speed, roll gap, feeding mechanisms and feeding speed) and powder properties (particle size, shape, moisture content). The moisture content affects the powder properties, such as the flowability and cohesion, but it is not clear how the moisture content will influence the powder compression behaviour during roller compaction. In this study, the effect of moisture contents on roller compaction behaviour of microcrystalline cellulose (MCC, Avicel PH102) was investigated experimentally. MCC samples of different moisture contents were prepared by mixing as-received MCC powder with different amount of water that was sprayed onto the powder bed being agitated in a rotary mixer. The flowability of these samples were evaluated in terms of the poured angle of repose and flow functions. The moist powders were then compacted using the instrumented roller compactor developed at the University of Birmingham. The flow and compression behaviour during roller compaction and the properties of produced ribbons were examined. It has been found that, as the moisture content increases, the flowability of moist MCC powders decreases and the powder becomes more cohesive. As a consequence of non-uniform flow of powder into the compaction zone induced by the friction between powder and side cheek plates, all produced ribbons have a higher density in the middle and lower densities at the edges. For the ribbons made of powders with high moisture contents, different hydration states across the ribbon width were also identified from SEM images. Moreover, it was interesting to find that these ribbons were split into two halves. This is attributed to the reduction in the mechanical strength of moist powder compacts with high moisture contents produced at high compression pressures. PMID:20176096

  13. Iron's Role in Aluminum: A Powder Metallurgy and Sustainability Approach

    NASA Astrophysics Data System (ADS)

    Saller, Brandon Dale

    The family of Al-Fe alloys is both scientifically and technologically interesting for several reasons. First, the low equilibrium solid solubility (0.03 at.%) and diffusivity of Fe in Al suggest that the alloys containing these two elements should be thermally stable. Many studies have tried to extend this low solubility value via non-equilibrium processing routes. Second, published results suggest that there is a range of intermetallic phases, including the metastable orthorhombic Al6Fe and the equilibrium monoclinic Al13Fe4, for example, the formation of which depends on solidification and subsequent processing conditions. Third, from a sustainability standpoint, both Al and Fe are present in bauxite (aluminum ore), however up to 40 wt.% Fe-oxide present in bauxite is discarded as a waste product, creating red mud pits. In order to understand the multiple facets and implications of iron's role in aluminum, a systematic investigation was performed into the precipitates that form as a function of thermal exposure and their subsequent effect on the tensile behavior of the alloy. In this study, Al-2at.% Fe and Al-5at.% Fe powders were synthesized via helium gas atomization and argon gas atomization, respectively. Cooling rates upwards of 106 K/s were achieved resulting in an intermetallic-free starting structure. Powders were subsequently severely plastically deformed via either cryomilling or high-pressure torsion to obtain nanostructured/ultrafine-grained powder or a consolidated specimen, respectively. Characterization via electron microscopy established a map of the powder microstructure as a function of atomization cooling rate. In addition, electron backscatter diffraction revealed a large number of low-angle grain boundaries, which influenced nucleation and precipitation of the metastable Al6Fe phase. X-ray diffraction and atom probe tomography results provide the most comprehensive evidence to date of forcing of 2at.% Fe into solution with the Al matrix via cryomilling. With respect to the powder, a differential scanning calorimetry and activation energy analysis elucidated the formation and phase transformation temperatures of the relevant intermetallic phases, and the microstructural factors that influenced them. With an understanding of the fundamental science behind the intermetallic formation in the Al-Fe system, the composition of helium atomized Al-2at.% Fe was chosen combined with high-pressure torsion processing to yield a bulk alloy that demonstrated an ultimate tensile strength of 488 MPa. This strength was achieved via a combination of two mechanisms: grain refinement (Hall-Petch) and dislocation-Al6Fe interactions (Orowan strengthening), with notable thermal stability present up until 450°C. Finally, the potential for Al-Fe as a sustainable alloy was studied and a link established between current environmental literature and metallurgy literature on the potential for incorporation of Fe into Al to create a structural alloy.

  14. Superplasticity in powder metallurgy aluminum alloys and composites

    SciTech Connect

    Mishra, R.S.; Bieler, T.R.; Mukherjee, A.K.

    1995-03-01

    Superplasticity in powder metallurgy Al alloys and composites has been reviewed through a detailed analysis. The stress-strain curves can be put into 4 categories: classical well-behaved type, continuous strain hardening type, continuous strain softening type and complex type. The origin of these different types of is discussed. The microstructural features of the processed material and the role of strain have been reviewed. The role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined. Threshold stresses have been determined and analyzed. The parametric dependencies for superplastic flow in modified conventional aluminum alloys, mechanically alloyed alloys and Al alloy matrix composites is determined to elucidate the superplastic mechanism at high strain rates. The role of incipient melting has been analyzed. A stress exponent of 2, an activation energy equal to that for grain boundary diffusion and a grain size dependence of 2 generally describes superplastic flow in modified conventional Al alloys and mechanically alloyed alloys. The present results agree well with the predictions of grain boundary sliding models. This suggests that the mechanism of high strain rate superplasticity in the above-mentioned alloys is similar to conventional superplasticity. The shift of optimum superplastic strain rates to higher values is a consequence of microstructural refinement. The parametric dependencies for superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of 313 kJ/mol best describes the composites having SiC reinforcements. The role of shape of the reinforcement (particle or whisker) and processing history is addressed. The analysis suggests that the mechanism for superplasticity in composites is interface diffusion controlled grain boundary sliding.

  15. Corrosion inhibition of powder metallurgy Mg by fluoride treatments.

    PubMed

    Pereda, M D; Alonso, C; Burgos-Asperilla, L; del Valle, J A; Ruano, O A; Perez, P; Fernández Lorenzo de Mele, M A

    2010-05-01

    Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process. PMID:19913114

  16. Testing of electroformed deposited iridium/powder metallurgy rhenium rockets

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Dickerson, Robert

    1996-01-01

    High-temperature, oxidation-resistant chamber materials offer the thermal margin for high performance and extended lifetimes for radiation-cooled rockets. Rhenium (Re) coated with iridium (Ir) allow hours of operation at 2200 C on Earth-storable propellants. One process for manufacturing Ir/Re rocket chambers is the fabrication of Re substrates by powder metallurgy (PM) and the application of Ir coatings by using electroformed deposition (ED). ED Ir coatings, however, have been found to be porous and poorly adherent. The integrity of ED Ir coatings could be improved by densification after the electroforming process. This report summarizes the testing of two 22-N, ED Ir/PM Re rocket chambers that were subjected to post-deposition treatments in an effort to densify the Ir coating. One chamber was vacuum annealed, while the other chamber was subjected to hot isostatic pressure (HIP). The chambers were tested on gaseous oxygen/gaseous hydrogen propellants, at mixture ratios that simulated the oxidizing environments of Earth-storable propellants. ne annealed ED Ir/PM Re chamber was tested for a total of 24 firings and 4.58 hr at a mixture ratio of 4.2. After only 9 firings, the annealed ED Ir coating began to blister and spall upstream of the throat. The blistering and spalling were similar to what had been experienced with unannealed, as-deposited ED Ir coatings. The HIP ED Ir/PM Re chamber was tested for a total of 91 firings and 11.45 hr at mixture ratios of 3.2 and 4.2. The HIP ED Ir coating remained adherent to the Re substrate throughout testing; there were no visible signs of coating degradation. Metallography revealed, however, thinning of the HIP Ir coating and occasional pores in the Re layer upstream of the throat. Pinholes in the Ir coating may have provided a path for oxidation of the Re substrate at these locations. The HIP ED Ir coating proved to be more effective than vacuum annealed and as-deposited ED Ir. Further densification is still required to match the integrity of chemically vapor deposited Ir coatings. Despite this, the successful long duration testing of the HIP ED Ir chamber, in an oxidizing environment comparable to Earth-storable propellants, demonstrated the viability of this Ir/Re rocket fabrication process.

  17. Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Gangloff, Richard P.

    1990-01-01

    Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging may play a role. Fractography showed that microvoid coalescence was the microscopic mode of fracture in FVS0812 under all testing conditions. However, the nature of the microvoids varied with test temperature and loading rate, and is complex for the fine grain and dipersoid sizes of FVS0812.

  18. Investigation of the Environmental Durability of a Powder Metallurgy Material

    NASA Technical Reports Server (NTRS)

    Ward, LaNita D.

    2004-01-01

    PM304 is a NASA-developed composite powder metallurgy material that is being developed for high temperature applications such as bushings in high temperature industrial furnace conveyor systems. My goal this summer was to analyze and evaluate the effects that heat exposure had on the PM304 material at 500 C and 650 C. The material is composed of Ni-Cr, Ag, Cr2O3, and eutectic BaF2-CaF2. PM304 is designed to eliminate the need for oil based lubricants in high temperature applications, while reducing friction and wear. However, further investigation was needed to thoroughly examine the properties of PM304. The effects of heat exposure on PM304 bushings were investigated. This investigation was necessary due to the high temperatures that the material would be exposed to in a typical application. Each bushing was cut into eight sections. The specimens were heated to 500 C or 650 C for time intervals from 1 hr to 5,000 hrs. Control specimens were kept at room temperature. Weight and thickness measurements were taken before and after the bushing sections were exposed to heat. Then the heat treated specimens were mounted and polished side by side with the control specimens. This enabled optical examination of the material's microstructure using a metallograph. The specimens were also examined with a scanning electron microscope (SEM). The microstructures were compared to observe the effects of the heat exposure. Chemical analysis was done to investigate the interactions between Ni-Cr and BaF2-CaF2 and between Cr2O3 and BaF2-CaF2 at high temperature. To observe this, the two compounds that were being analyzed were mixed in a crucible in varied weight percentages and heated to 1100 C in a furnace for approximately two hours. Then the product was allowed to cool and was then analyzed by X-ray diffraction. Interpretation of the results is in progress.

  19. High strength bulk Fe-Co alloys produced by powder metallurgy

    SciTech Connect

    Turgut, Zafer; Huang Meiqing; Horwath, John C.; Fingers, Richard T.

    2008-04-01

    Fe-Co alloys are extensively used in lamination form, but there are certain power generation applications that require Fe-Co rotors in bulk form. Experiencing only a dc magnetic field, these rotors can be as large as 0.5 m in diameter, depending on the size of the generator. The forging of such large pieces of Fe-Co has proven to be difficult. The present study investigates powder metallurgy processing of a gas atomized FeCoNbV alloy through hot isostatic pressing (HIP) for manufacturing large size rotors with improved mechanical strength. Gas atomized FeCoNbV alloy powders with and without ball milling were hot isostatic pressed at temperatures between 675 and 850 deg. C at a fixed pressure of 193 MPa for up to 6 h. Ball milling prior to HIP improved the yield strength. A further improvement in yield strength and in ductility was obtained after a disordering heat treatment at 730 deg. C followed by a rapid quench to room temperature. The optimum HIP and annealing conditions resulted in samples with yield strengths of 870 MPa. The compacts exhibited average coercivity values of 6.4 Oe and maximum permeability values of 1100.

  20. Dynamic compaction of tungsten carbide powder.

    SciTech Connect

    Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

    2005-04-01

    The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

  1. Fabrication of Powder Metallurgy Pure Ti Material by Using Thermal Decomposition of TiH2

    NASA Astrophysics Data System (ADS)

    Mimoto, Takanori; Nakanishi, Nozomi; Umeda, Junko; Kondoh, Katsuyoshi

    Titanium (Ti) and titanium alloys have been interested as an engineering material because they are widely used across various industrial applications, for example, motorcycle, automotive and aerospace industries, due to their light weight, high specific strength and superior corrosion resistance. Ti materials are particularly significant for the aircraft using carbon/carbon (C/C) composites, for example, carbon fiber reinforced plastics (CFRP), because Ti materials are free from the problem of contact corrosion between C/C composites. However, the applications of Ti materials are limited because of their high cost. From a viewpoint of cost reduction, cost effective process to fabricate Ti materials is strongly required. In the present study, the direct consolidation of titanium hydride (TiH2) raw powders in solid-state was employed to fabricate pure Ti bulk materials by using thermal decomposition of TiH2. In general, the production cost of Ti components is expensive due to using commercially pure (CP) Ti powders after dehydrogenation. On the other hand, the novel process using TiH2 powders as starting materials is a promising low cost approach for powder metallurgy (P/M) Ti products. Furthermore, this new process is also attractive from a viewpoint of energy saving because the dehydrogenation is integrated into the sintering process. In this study, TiH2 raw powders were directly consolidated by conventional press technique at 600 MPa to prepare TiH2 powder compacted billets. To thermally decompose TiH2 and obtain sintered pure Ti billets, the TiH2 powder billets were heated in the integrated sintering process including dehydrogenation. The hot-extruded pure Ti material, which was heat treated at 1273 K for 180 min in argon gas atmosphere, showed tensile strength of 701.8 MPa and elongation of 27.1%. These tensile properties satisfied the requirements for JIS Ti Grade 4. The relationship between microstructures, mechanical properties response and heat treatment temperature is discussed in detail.

  2. Shock compaction of molybdenum nitride powder

    NASA Astrophysics Data System (ADS)

    Roberson, S.; Davis, R. F.; Joshi, V. S.; Fienello, D.

    1998-07-01

    Molybdenum nitride has a potential application in multi layer capacitors. Since this material is not readily available in bulk form, molybdenum nitride powder, consisting of a mixture of the nitrides Mo2N and MoN has been compacted to 12 mm circular, 1-2 mm thick discs utilizing shock-compression technique. Powders were packed to 55-67 percent of the crystal density and shock compacted using a plate impact shock recovery system at 1.35 to 1.81 km/s impact velocity. The recovered compacts were characterized by scanning electron microscope, x-ray diffraction and cyclic voltammetry to evaluate its electrochemical stability in sulphuric acid. This paper presents the optimization technique used for compaction and the characteristics of the recovered compacts.

  3. Interfacial reactions and wetting in Al-Mg sintered by powder metallurgy process

    NASA Astrophysics Data System (ADS)

    Faisal, Heny; Darminto, Triwikantoro, Zainuri, M.

    2016-04-01

    Was conducted to analyze the effect of temperature variation on the bonding interface sintered composite Al-Mg and analyze the effect of variations of the density and hardness sinter. Research carried out by the base material powders of Al, Mg powder and solvent n-butanol. The method used in this study is a powder metallurgy, with a composition of 60% volume fraction of Al - 40% Mg. Al-Mg mixing with n-butanol for 1 hour at 500 rpm. Then the emphasis (cold comression) with a size of 1.4 cm in diameter dies and height of 2.8 cm, is pressed with a force of 20 MPa and held for 15 minutes. After the sample into pellets, then sintered at various temperatures 300 °C, 350 °C, 400 °C and 450 °C. Characterization is done by using the testing green density, sintered density, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), vickers microhardness, and press test. XRD data analysis done by using X'Pert High Score Plus (HSP) to determine whether there is a new phase is formed. Test results show that the sintered density increasing sintering temperature, the resulting density is also increasing (shrinkage). However, at a temperature of 450 °C decreased (swelling). With the increased sinter density, interfacial bonding getting Kuta and more compact so that its hardness is also increased. From the test results of SEM / EDX, there Mg into Al in the border area. At temperatures of 300 °C, 350 °C, 400 °C, the phase formed is Al, Mg and MgO. While phase is formed at a temperature of 450 °C is aluminum magnesium (Al3Mg2), Aluminum Magnesium Zinc (AlMg2Zn).

  4. Compaction Stress in Fine Powders

    SciTech Connect

    Hurd, A.J.; Kenkre, V.M.; Pease, E.A.; Scott, J.E.

    1999-04-01

    A vexing feature in granular materials compaction is density extrema interior to a compacted shape. Such inhomogeneities can lead to weaknesses and loss of dimensional control in ceramic parts, unpredictable dissolution of pharmaceuticals, and undesirable stress concentration in load-bearing soil. As an example, the centerline density in a cylindrical compact often does not decrease monotonically from the pressure source but exhibits local maxima and minima. Two lines of thought in the literature predict, respectively, diffusive and wavelike propagation of stress. Here, a general memory function approach has been formulated that unifies these previous treatments as special cases; by analyzing a convenient intermediate case, the telegrapher's equation, one sees that local density maxima arise via semidiffusive stress waves reflecting from the die walls and adding constructively at the centerline.

  5. [Concomitant influence of occupational and social risk factors on health of workers engaged into powder metallurgy].

    PubMed

    Shur, P Z; Zaĭtseva, N V; Kostarev, V G; Lebedeva-Nesevria, N A; Shliapnikov, D M

    2012-01-01

    Results of health risk evaluation in workers engaged into powder metallurgy, using complex of hygienic, medical, epidemiologic and sociologic studies, enable to define priority occupational and social risk factors, to assess degree of their influence on the workers' health and to identify occupationally induced diseases. PMID:23461181

  6. Powder metallurgy approaches to high temperature components for gas turbine engines

    NASA Technical Reports Server (NTRS)

    Probst, H. B.

    1974-01-01

    Research is reported for the tensile strength, ductility, and heat performance characterisitics of powder metallurgy (p/m) superalloys. Oxide dispersion strengthened alloys were also evaluated for their strength during thermal processing. The mechanical attributes evident in both p/m supperalloys and dispersion strengthened alloys are discussed in terms of research into their possible combination.

  7. Powder metallurgy in aerospace structural applications---Current use and future trends

    SciTech Connect

    Froes, F.H.; Rowe, R.G.; Das, S.K.; Stephens, J.J.

    1989-06-09

    The major role played by materials in providing advances in systems performance as we move towards the twenty-first century is reviewed. Specific developments in the powder metallurgy/rapid solidification of alloys, based on aluminum, magnesium, titanium, niobium, and copper are discussed in detail. 47 refs., 12 figs.

  8. Mechanical properties of modified low cobalt powder metallurgy Udimet 700 type alloys

    NASA Technical Reports Server (NTRS)

    Harf, Fredric H.

    1989-01-01

    Eight superalloys derived from Udimet 700 were prepared by powder metallurgy, hot isostatically pressed, heat treated and their tensile and creep rupture properties determined. Several of these alloys displayed properties superior to those of Udimet 700 similarly prepared, in one case exceeding the creep rupture life tenfold. Filter clogging by extracted gamma prime, its measurement and significance are discussed in an appendix.

  9. Advances in the manufacturing of powder metallurgy (PM) parts by hot isostatic pressing

    SciTech Connect

    Conway, J.J.; Rizzo, F.J.; Nickel, C.K.

    1996-12-31

    Several thousand powder metallurgy (P/M) parts, consolidated to full density by hot isostatic pressing (HIP), are produced each year. Recent progress in the areas of shape prediction via computer modeling, can fabrication, vacuum filling of powder into containers and optimizing HIP cycle pressurization and heat-up rates have advanced the technology into new applications. This work summarizes recent production experience with monolithic and bi-metallic clad parts which has taken advantage of these technological advances.

  10. Spray forming and mechanical properties of a new type powder metallurgy superalloy

    NASA Astrophysics Data System (ADS)

    Jia, Chong-Lin; Ge, Chang-Chun; Xia, Min; Gu, Tian-Fu

    2015-11-01

    The deposited billet of a new type powder metallurgy (PM) superalloy FGH4095M for use in turbine disk manufacturing has been fabricated using spray forming technology. The metallurgical quality of the deposited billet was analyzed in terms of density, texture, and grain size. Comparative research was done on the microstructure and mechanical properties between the flat disk preform prepared with hot isostatic pressing (HIP) and the same alloy forgings prepared with HIP followed by isothermal forging (IF). The results show that the density of the spray-formed and nitrogen-atomized deposit billet is above 99% of the theoretical density, indicating a compact structure. The grains are uniform and fine. The billet has weak texture with a random distribution in the spray deposition direction and perpendicular to the direction of deposition. A part of atomizing nitrogen exists in the preform in the form of carbonitride. Nitrogen-induced microporosity causes the density reduction of the preform. Compared with the process of HIP+IF, the superalloy FGH4095M after HIP has better mechanical properties at both room temperature and high temperature. The sizes of the γ‧ phase are finer in microstructure of the preform after HIP in comparison with the forgings after HIP+IF. This work shows that SF+HIP is a viable processing route for FGH4095M as a turbine-disk material. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

  11. Application of superalloy powder metallurgy for aircraft engines

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    The results of the Materials for Advanced Turbine Engines (MATE) program initiated by NASA are presented. Mechanical properties comparisons are made for superalloy parts produced by as-HIP powder consolidation and by forging of HIP consolidated billets. The effect of various defects on the mechanical properties of powder parts are shown.

  12. In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

    PubMed

    Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. PMID:19815098

  13. Investigation of machinability of iron based metal matrix composite (MMC) powder metallurgy parts

    NASA Astrophysics Data System (ADS)

    Szalay, Tibor; Czampa, Miklós; Markos, Sándor; Farkas, Balázs

    2012-09-01

    One of the advantages of powder metallurgy technology is that we may produce the final geometry of the required part saving considerable time and cost. However there are several applications that require parts need additional machining for example when the product contains threads, cross bore or slots. In these cases cutting of the hard and porous material may causes difficulties in manufacturing. The aim of the introduced research is the experimental investigation of the machinability of the iron based MMC powder metallurgy parts, determining the favourable composition of the powder and advantageous process parameters regarding the properties of the machinability. The research try to answer to the challenge of the poorly defined expression: machinability, and after defining the features and methods of the evaluation we develop advises for the proper technology parameters.

  14. Properties of WZ21 (%wt) alloy processed by a powder metallurgy route.

    PubMed

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

    2015-06-01

    Microstructure, mechanical properties and corrosion behaviour of WZ21 (%wt) alloy prepared by a powder metallurgy route from rapidly solidified powders have been studied. Results were compared to those of the same alloy prepared through a conventional route of casting and extrusion. The microstructure of the extruded ingot consisted of α-Mg grains and Mg3Zn3Y2 (W-phase) and LPSO-phase particles located at grain boundaries. Moreover, stacking faults were also observed within α-Mg grains. The alloy processed by the powder metallurgy route exhibited a more homogeneous and finer microstructure, with a grain size of 2 μm. In this case W-phase and Mg24Y5 phase were identified, but not the LPSO-phase. The microstructural refinement induced by the use of rapidly solidified powders strengthened the alloy at room temperature and promoted superplasticity at higher strain rates. Corrosion behaviour in PBS medium evidenced certain physical barrier effect of the almost continuous arrangements of second phases aligned along the extrusion direction in conventionally processed WZ21 alloy, with a stable tendency around 7 mm/year. On the other hand, powder metallurgy processing promoted significant pitting corrosion, inducing accelerated corrosion rate during prolonged immersion times. PMID:25792409

  15. Biaxially textured articles formed by power metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  16. Porous mandrels provide uniform deformation in hydrostatic powder metallurgy

    NASA Technical Reports Server (NTRS)

    Gripshover, P. J.; Hanes, H. D.

    1967-01-01

    Porous copper mandrels prevent uneven deformation of beryllium machining blanks. The beryllium powder is arranged around these mandrels and hot isostatically pressed to form the blanks. The mandrels are then removed by leaching.

  17. Making Self-Lubricating Parts By Powder Metallurgy

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1990-01-01

    Compositions and parameters of powder-metallurgical fabrication processes determined for new class of low-friction, low-wear, self-lubricating materials. Used in oxidizing or reducing atmospheres in bearings and seals, at temperatures from below 25 degrees C to as high as 900 degrees C. Thick parts made with minimal waste.

  18. A Nonvolume Preserving Plasticity Theory with Applications to Powder Metallurgy

    NASA Technical Reports Server (NTRS)

    Cassenti, B. N.

    1983-01-01

    A plasticity theory has been developed to predict the mechanical response of powder metals during hot isostatic pressing. The theory parameters were obtained through an experimental program consisting of hydrostatic pressure tests, uniaxial compression and uniaxial tension tests. A nonlinear finite element code was modified to include the theory and the results of themodified code compared favorably to the results from a verification experiment.

  19. Effect of yttrium addition on mechanical behavior of powder metallurgy TP304 at elevated temperatures

    SciTech Connect

    Isomoto, Tatsuro; Nagai, Hiroshi; Kida, Tadanori

    1997-02-01

    It is well known that oxide dispersion strengthened (ODS) alloys, which are mechanically alloyed with yttria, possess excellent mechanical properties in comparison with conventional ingot metallurgy (IM) materials at elevated temperatures even higher than 1,000 C. However, mechanical alloying may not be desired in view of production cost for the high temperature application where such high strength is not necessarily required. There is not an extensive literature dealing with mechanical properties at above 800 C of the fully dense powder metallurgy (PM) materials without mechanical alloying. In the present study, the melt of TP304 containing yttrium was atomized to form yttria on and in the powder. The effects of such oxide inclusions on high temperature tensile properties and creep rupture strengths are investigated, using TP304 fully dense materials consolidated by hot extrusion.

  20. Preparation of Three-Dimensional Graphene Foams Using Powder Metallurgy Templates.

    PubMed

    Sha, Junwei; Gao, Caitian; Lee, Seoung-Ki; Li, Yilun; Zhao, Naiqin; Tour, James M

    2016-01-26

    A simple and scalable method which combines traditional powder metallurgy and chemical vapor deposition is developed for the synthesis of mesoporous free-standing 3D graphene foams. The powder metallurgy templates for 3D graphene foams (PMT-GFs) consist of particle-like carbon shells which are connected by multilayered graphene that shows high specific surface area (1080 m(2) g(-1)), good crystallization, good electrical conductivity (13.8 S cm(-1)), and a mechanically robust structure. The PMT-GFs did not break under direct flushing with DI water, and they were able to recover after being compressed. These properties indicate promising applications of PMT-GFs for fields requiring 3D carbon frameworks such as in energy-based electrodes and mechanical dampening. PMID:26678869

  1. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder Metallurgy Produced Titanium Alloys

    SciTech Connect

    Muth, Thomas R; Yamamoto, Yukinori; Frederick, David Alan; Contescu, Cristian I; Chen, Wei; Lim, Yong Chae; Peter, William H; Feng, Zhili

    2013-01-01

    ORNL undertook an investigation using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate, to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas forming species. PM-titanium made from revert scrap where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal / minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders, are critical to achieve equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  2. High strain rate superplasticity in powder metallurgy processed Al-16Si-5Fe alloy

    SciTech Connect

    Cho, H.S.; Jeong, H.G.; Kim, M.S.; Yamagata, H.

    2000-01-01

    In the present paper, new additional experimental results for these aluminum alloys with a very fine grain structure are demonstrated over a strain range of 10{sup {minus}4} {approximately} 10{sup {minus}1} s{sup {minus}1} in the temperature range of 673 {approximately} 793 K, to analyze the possible mechanisms of superplasticity at high strain rates in very fine grained aluminum alloys produced by powder metallurgy method.

  3. Hydrogen halide cleaning of powder metallurgy nickel-20 chromium-3 thoria.

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1972-01-01

    The Cr2O3 content of powder metallurgy nickel-20 chromium-3 thoria was reduced with atmospheres consisting of hydrogen plus hydrogen chloride (HCl) or hydrogen bromide (HBr). The nonthoria oxygen content or 'oxygen excess' was reduced from an initial amount of greater than 50,000 ppm to less than 100 ppm. Low temperatures were effective, but lowest oxygen levels were achieved with the highest cleaning temperature of 1200 C.

  4. Microstructures and mechanical properties of hot isostatically pressed powder metallurgy Alloy APK-1

    NASA Astrophysics Data System (ADS)

    Prakash, T. L.; Chari, Y. N.; Rao, E. S. Bhagiradha; Thamburaj, R.

    1983-03-01

    The influence of Hot Isostatic Pressing (HIP) and heat treatment parameters on the microstructure and mechanical properties of powder metallurgy alloy APK-1 (a low carbon modification of Astroloy) has been investigated. Poor mechanical properties result if carbide networks are present along the prior particle boundaries (PPBs). These networks which form during powder consolidation can be avoided by manipulating HIP parameters. Heat treatments which produce a large volume fraction of fine γ’ make this alloy susceptible to environment-assisted tensile embrittlement around 760 °C.

  5. Compacting Plastic-Bonded Explosive Molding Powders to Dense Solids

    SciTech Connect

    B. Olinger

    2005-04-15

    Dense solid high explosives are made by compacting plastic-bonded explosive molding powders with high pressures and temperatures for extended periods of time. The density is influenced by manufacturing processes of the powders, compaction temperature, the magnitude of compaction pressure, pressure duration, and number of repeated applications of pressure. The internal density variation of compacted explosives depends on method of compaction and the material being compacted.

  6. Net-Shape HIP Powder Metallurgy Components for Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bampton, Cliff; Goodin, Wes; VanDaam, Tom; Creeger, Gordon; James, Steve

    2005-01-01

    True net shape consolidation of powder metal (PM) by hot isostatic pressing (HIP) provides opportunities for many cost, performance and life benefits over conventional fabrication processes for large rocket engine structures. Various forms of selectively net-shape PM have been around for thirty years or so. However, it is only recently that major applications have been pursued for rocket engine hardware fabricated in the United States. The method employs sacrificial metallic tooling (HIP capsule and shaped inserts), which is removed from the part after HIP consolidation of the powder, by selective acid dissolution. Full exploitation of net-shape PM requires innovative approaches in both component design and materials and processing details. The benefits include: uniform and homogeneous microstructure with no porosity, irrespective of component shape and size; elimination of welds and the associated quality and life limitations; removal of traditional producibility constraints on design freedom, such as forgeability and machinability, and scale-up to very large, monolithic parts, limited only by the size of existing HIP furnaces. Net-shape PM HIP also enables fabrication of complex configurations providing additional, unique functionalities. The progress made in these areas will be described. Then critical aspects of the technology that still require significant further development and maturation will be discussed from the perspective of an engine systems builder and end-user of the technology.

  7. Powder metallurgy processing and deformation characteristics of bulk multimodal nickel

    SciTech Connect

    Farbaniec, L.; Dirras, G.; Krawczynska, A.; Mompiou, F.; Couque, H.; Naimi, F.; Bernard, F.; Tingaud, D.

    2014-08-15

    Spark plasma sintering was used to process bulk nickel samples from a blend of three powder types. The resulting multimodal microstructure was made of coarse (average size ∼ 135 μm) spherical microcrystalline entities (the core) surrounded by a fine-grained matrix (average grain size ∼ 1.5 μm) or a thick rim (the shell) distinguishable from the matrix. Tensile tests revealed yield strength of ∼ 470 MPa that was accompanied by limited ductility (∼ 2.8% plastic strain). Microstructure observation after testing showed debonding at interfaces between the matrix and the coarse entities, but in many instances, shallow dimples within the rim were observed indicating local ductile events in the shell. Dislocation emission and annihilation at grain boundaries and twinning at crack tip were the main deformation mechanisms taking place within the fine-grained matrix as revealed by in-situ transmission electron microscopy. Estimation of the stress from loop's curvature and dislocation pile-up indicates that dislocation emission from grain boundaries and grain boundary overcoming largely contributes to the flow stress. - Highlights: • Bulk multi-modal Ni was processed by SPS from a powder blend. • Ultrafine-grained matrix or rim observed around spherical microcrystalline entities • Yield strength (470 MPa) and ductility (2.8% plastic strain) were measured. • Debonding was found at the matrix/microcrystalline entity interfaces. • In-situ TEM showed twinning, dislocation emission and annihilation at grain boundaries.

  8. Army P/M research and development overview. Final report. [P/M (powder metallurgy)

    SciTech Connect

    Dowding, R.J.; Wells, M.G.; Crowson, A.

    1993-05-01

    The Army uses of powder metallurgy (P/M) extend from the conventional press and sinter to the more exotic processes of liquid phase sintering of tungsten heavy alloys (WHA) and powder injection molding (PIM). Many of the more advanced high performance applications require extensive research and development (R and D) prior to fielding of the application. Examples arc the intense research into WHA in the last ten years. This research has led to great understanding of these heavy alloys and application into some kinetic energy systems. The Navy has taken great advantage of WHA by employing them iii the phalanx close-in weapon system (CIWS). The Army intends that research will lead to an alloy or composite of tungsten that, when used as a long rod penetrator, will perform as well as, or better than, current depleted uranium (DU) penetrators. This will allow possible replacement of the controversial DU. Powder injection molding of WHA is an area receiving attention because of the potential for producing small and medium caliber projectiles. The drawbacks at this time include the need to develop an alloy that does not require post sinter cold working to develop the strength required for these demanding applications. Other possible problems include producing slender long rod projectiles with desired product straightness. In addition to the work on tungsten alloys, a discussion is underway of other powder metallurgy R and D and is under active investigation within the Army. These topics include aluminum and titanium alloys, intermetallics, and ultrahigh strength steels for structural and propulsion applications, as well as nonequilibrium P/M produced structures.... Powder metallurgy, Tungsten alloys, Aluminum alloys, Titanium alloys, Intermetallic.

  9. Powder metallurgy processing of high strength turbine disk alloys

    NASA Technical Reports Server (NTRS)

    Evans, D. J.

    1976-01-01

    Using vacuum-atomized AF2-1DA and Mar-M432 powders, full-scale gas turbine engine disks were fabricated by hot isostatically pressing (HIP) billets which were then isothermally forged using the Pratt & Whitney Aircraft GATORIZING forging process. While a sound forging was produced in the AF2-1DA, a container leak had occurred in the Mar-M432 billet during HIP. This resulted in billet cracking during forging. In-process control procedures were developed to identify such leaks. The AF2-1DA forging was heat treated and metallographic and mechanical property evaluation was performed. Mechanical properties exceeded those of Astroloy, one of the highest temperature capability turbine disk alloys presently used.

  10. Properties of boride-added powder metallurgy magnesium alloys

    NASA Astrophysics Data System (ADS)

    Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

    2009-06-01

    Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.

  11. High-strength powder metallurgy aluminum alloys in glass-forming Al-Ni-Ce-(Ti or Zr) systems

    SciTech Connect

    Kawamura, Y.; Inoue, A.; Sasamori, K.; Masumoto, T. )

    1993-07-15

    Powder metallurgy (P/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few approaches are considered: the crystallization of an amorphous alloy, the control of cooling rate from melt and the selection of optimum composition for glass-forming alloys. However, these methods are generally attended with a disadvantage for embrittlement. Recently, it has been found that Al-based amorphous alloys exhibiting high tensile strength and good bending ductility form by liquid quenching in the Al-Ln-TM (Ln: lanthanide metal, TM: transition metal) system. Furthermore, the consolidation of the amorphous alloy powders to a bulk amorphous alloy has also been achieved by warm extrusion. The first aim of this paper is to examine the effect of alloy composition on the strength and ductility of crystalline compacts produced by extrusion of rapidly solidified powders in the Al-Ni-Ce-TM(TM:Ti, Mn, Fe, Co, Cu, Zr) systems where an amorphous phase is formed by melt spinning. The second is to investigate whether or not the structural refinement by using glass-forming alloys is useful to develop high-strength P/M aluminum alloys.

  12. Fabrication and characterization of americium, neptunium and curium bearing MOX fuels obtained by powder metallurgy process

    NASA Astrophysics Data System (ADS)

    Lebreton, Florent; Prieur, Damien; Jankowiak, Aurélien; Tribet, Magaly; Leorier, Caroline; Delahaye, Thibaud; Donnet, Louis; Dehaudt, Philippe

    2012-01-01

    MOX fuel pellets containing up to 1.4 wt% of Minor Actinides (MA), i.e. Am, Np and Cm, were fabricated to demonstrate the technical feasibility of powder metallurgy process involving, pelletizing and sintering in controlled atmosphere. The compounds were then characterized using XRD, SEM and EDX/EPMA. Dense pellets were obtained which closed porosity mean size is equal to 7 μm. The results indicate the formation of (U, Pu)O 2 solid solution. However, microstructure contains some isolated UO 2 grains. The distribution of Am and Cm appears to be homogeneous whereas Np was found to be clustered at some locations.

  13. Microstructure and mechanical reliability of powder metallurgy (P/M) ferrous alloys

    SciTech Connect

    Straffelini, G.; Molinari, A.

    1996-02-01

    Because of their macroscopic brittle behavior, porous powder metallurgy (P/M) ferrous alloys are often not considered for structural applications. A statistical approach based on the evaluation and interpretation of the Weibull modulus was thus proposed to evaluate correctly and objectively the intrinsic structural reliability of these materials. In spite of their porosity, P/M ferrous alloys are as reliable as conventional wrought steels, provided that they are correctly produced and, if necessary, heat treated. In addition, the influence of density and the application of the method to the process optimization and control was highlighted. In all cases, the mechanical reliability of the materials was interpreted metallurgically.

  14. Near-transus processing (NTP) of powder metallurgy TiAl-based alloys

    SciTech Connect

    Fuchs, G.E.

    1995-07-01

    Alloys based on the intermetallic compound {gamma}-TiAl are rapidly being developed for elevated temperature structural applications. In order to produce an alloy, by either I/M or P/M techniques, with useful engineering properties, it is necessary to control the microstructure by heat treatment and/or hot working. By combining consolidation with the heat treatment, unique microstructures can be produced in powder metallurgy (P/M) materials. The effect of processing on the microstructures and tensile and creep properties are discussed.

  15. Dose and Dose Risk Caused by Natural Phenomena - Proposed Powder Metallurgy Core Manufacturing Facility

    SciTech Connect

    Holmes, W.G.

    2001-08-16

    The offsite radiological effects from high velocity straight winds, tornadoes, and earthquakes have been estimated for a proposed facility for manufacturing enriched uranium fuel cores by powder metallurgy. Projected doses range up to 30 mrem/event to the maximum offsite individual for high winds and up to 85 mrem/event for very severe earthquakes. Even under conservative assumptions on meteorological conditions, the maximum offsite dose would be about 20 per cent of the DOE limit for accidents involving enriched uranium storage facilities. The total dose risk is low and is dominated by the risk from earthquakes. This report discusses this test.

  16. Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Newman, John A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent.

  17. Electrochemical study of Aluminum-Fly Ash composites obtained by powder metallurgy

    SciTech Connect

    Marin, E.; Lekka, M.; Andreatta, F.; Fedrizzi, L.; Itskos, G.; Koukouzas, N.

    2012-07-15

    In this paper, two different ASTM C 618 Class C fly ashes (FA) were used for the production of aluminum metal matrix composites (MMCs) using powder metallurgy (PM) technology. Calcareous FAs were sampled from the electrostatic precipitators of two different lignite-fired power stations: from Megalopolis, Southern Greece (MFA) and from Kardia, Northen Greece (KFA), under maximum electricity load. FAs were milled in order to reduce the mean particle diameter and Aluminum-FA composites containing 10% and 20% of FA were then prepared and compacted. The green products were sintered for 2 h at 600 Degree-Sign C. Sintered Al-FA MMCs showed increased hardness and wear resistance suggesting their possible use in industrial applications for example in covers, casings, brake rotors or engine blocks. As most possible industrial applications of MMCs not only require wear resistance, but also corrosion resistance in different mild aggressive medias, this paper aims to study the electrochemical behavior of FA MMCs in order to evaluate their corrosion resistance. The morphology and chemical composition of the phases in the Aluminum-FA composite samples were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Moreover, topographic and Volta potential maps were acquired by Scanning Kelvin Probe Force Microscopy (SKP-FM). Volta potential maps provide information about the electrochemical behavior of the different phases in absence of electrolyte. The electrochemical behavior was investigated by Open Circuit Potential measurements and potentiodynamic polarization, while the corrosion mechanisms were studied by SEM observations after different times of immersion in a mild corrosive medium. In all cases it could be stated that the addition of the FA particles into the Al matrix might cause an increase of the hardness and mechanical properties of the pure aluminum but deteriorates the corrosion resistance. The degradation phenomena occurring on the FA containing samples might be related to the following mechanisms: 1) Partial detachment or dissolution of the FA soluble phases, in particular based on Si, Fe and Ca; 2) dissolution of the Al matrix surrounding the FA particles due to crevice corrosion; 3) Al localized dissolution due to galvanic coupling between the Fe-rich intermetallics and the matrix. - Highlights: Black-Right-Pointing-Pointer Aluminum metal matrix composites containing two types of fly ashes have been characterized. Black-Right-Pointing-Pointer The microstructure and the electrochemical behavior have been studied using different techniques. Black-Right-Pointing-Pointer The addition of FA deteriorates the corrosion resistance of the aluminum. Black-Right-Pointing-Pointer Degradation mechanisms: galvanic coupling, crevice corrosion, detachment of FA particles.

  18. Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.; Dreshfield, R. L.

    1980-01-01

    Hot isostatically pressed powder metallurgy Astroloy was obtained which contained 1.4 percent fine porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores averaged about 2 micrometers diameter and 20 micrometers spacing. They did influence fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 micrometers pore in one specimen resulting from a hollow particle did not reduce life by 60 percent. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in sigma sub u/E for the porous material.

  19. Microstructure and mechanical behavior of 6061Al reinforced with silicon nitride particles, processed by powder metallurgy

    SciTech Connect

    Amigo, V.; Ortiz, J.L.; Salvador, M.D.

    2000-01-31

    A critical step in the processing of Metal Matrix Composites (MMCs) reinforced with ceramic particles is the insertion of these particles into the metal matrix alloy. This greatly influences the strength of the composite since it is controlled by the metal-particle interfacial bond strength. Because of the difficulty in wetting ceramic particles with molten metal, the Powder Metallurgy or PM route was developed. Powder Extrusion consolidates the composite to over 98% dense, and can be carried out below the Solidus Temperature of the alloy. The most important aspect of the microstructure is the distribution of the reinforcing particles, and this depends on the processing and fabrication routes involved, as well as the relative size of the matrix and reinforcing particles. Extrusion can homogenize the structure to some extent, but minimizing reinforcement inhomogeneity during initial processing is important to achieve optimum properties.

  20. Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Dreshfield, R. L.

    1980-01-01

    Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 percent porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with data on sound Astroloy. They influenced fatigue crack initiation and produced a more intergranular mode of propagation but fatigue life was not drastically reduced. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was changed little.

  1. Microstructural and mechanical characteristics of porous iron prepared by powder metallurgy.

    PubMed

    Capek, Jaroslav; Vojtěch, Dalibor

    2014-10-01

    The demand for porous biodegradable load-bearing implants has been increasing recently. Based on investigations of biodegradable stents, porous iron may be a suitable material for such applications. In this study, we prepared porous iron samples with porosities of 34-51 vol.% by powder metallurgy using ammonium bicarbonate as a space-holder material. We studied sample microstructure (SEM-EDX and XRD), flexural and compressive behaviors (universal loading machine) and hardness HV5 (hardness tester) of the prepared samples. Sample porosity increased with the amount of spacer in the initial mixtures. Only the pore surfaces had insignificant oxidation and no other contamination was observed. Increasing porosity decreased the mechanical properties of the samples; although, the properties were still comparable with human bone and higher than those of porous non-metallic biomaterials and porous magnesium prepared in a similar way. Based on these results, powder metallurgy appears to be a suitable method for the preparation of porous iron for orthopedic applications. PMID:25175241

  2. Comparison of the creep properties of cast and powder metallurgy-extruded binary NiAl

    SciTech Connect

    Raj, S.V.; Garg, A.; Bieler, T.R.

    1997-12-31

    The current emphasis in developing NiAl-based alloys for use in gas-turbine aircraft engines requires a fundamental understanding of the creep mechanisms dominant in these materials. Here, a comparison of published creep data on binary NiAl showed that there is a discrepancy in the reported magnitudes of the stress exponents, n, which usually vary between about 4.5 and 6.5. In general, a close examination of the data suggested that n {approx} 4.5 for cast materials and 6.5 for powder-metallurgy extruded NiAl. Constant load compression creep tests were conducted on a cast and extruded binary NiAl between 800 and 1,200 K over a wide range of initial applied stresses varying between 4.0 and 200 MPa. The microstructures were characterized by transmission electron microscopy. The observed variations in the creep behavior of the extruded cast and powder-metallurgy NiAl appeared to be due to a grain size effect. Despite similarities in the values of n, no significant substructure was observed in most of the grains in the cast and extruded specimens at 1,100 and 1,200 K in contrast to the PM-extruded alloy, which revealed a wide range of substructural features in the power-law creep region. However, extensive subgrain formation and dislocations were widely observed at lower temperatures and higher stresses in the cast and extruded material.

  3. A probabilistic method for the fatigue life assessment of powder metallurgy parts of aircraft engines

    SciTech Connect

    Krafft, R.; Mosset, S.

    1996-04-01

    This paper will present a probabilistic approach developed in order to assess the fatigue life of aircraft engine parts (turbine disks) obtained by powder metallurgy technique. First of all, the main issues will be pointed out and the theoretical principles of the method will be described. Then the design implications and the experimental correlation will be emphasized. The scale effect is a major concern for the fatigue life assessment of a powder metallurgy part. It no longer allows the designer to evaluate the life of a massive part directly from experimental results based on small specimen fatigue tests as is done in the classical methodology. In order to describe this scale effect correctly, incubation sites (inhomogeneities like ceramic inclusions) must be characterized. The size of these inhomogeneities and their positions in the part appeared to be the most relevant parameters. Hence the methodology developed at SNECMA integrates the scale effect scatter through a binomial probability distribution as well as a temperature and stress-dependent life evaluation for each inhomogeneity size and position. The life calculation of a part implies an analysis of its whole volume and surface. An iterative process determines the number of cycles corresponding to a global reliability level requirement for the part. The complete methodology is then validated by comparing the calculated initiation distribution with experimental results on small specimens and test disks.

  4. Effect of extrusion temperature on the microstructure of a powder metallurgy TiAl-based alloy

    SciTech Connect

    Hsiung, L.M.; Nieh, T.G.; Clemens, D.R.

    1997-01-15

    In order to balance low temperature ductility, fracture toughness and high temperature properties of {gamma}-TiAl aluminide alloys, recent developments of the alloys have focused on refining the {gamma}/{alpha}{sub 2} full lamellar (FL) microstructure through advanced processing such as powder metallurgy (P/M). Resulted from a refined FL microstructure (both smaller lamellar grain size and thinner lamellar interface spacing) in the P/M fabricated titanium aluminide alloys, the mechanical properties of the alloys have been demonstrated to be superior to those of the aluminide alloys fabricated by conventional ingot metallurgy (I/M). However, since the microstructure of rapidly-solidified aluminide powder used in P/M process is not in an equilibrium state, the microstructures of P/M aluminide alloys are expected to be sensitive to the processing history. Accordingly, the optimization of microstructure-property of a P/M alloy through an appropriate P/M process control becomes an important issue. The purpose of this investigation is therefore aiming at understanding the effect of extrusion temperature on the microstructure of a P/M titanium aluminide alloy.

  5. Development of an extra-high strength powder metallurgy nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Kent, W. B.

    1977-01-01

    A program was conducted to optimize the composition of NASA IIb-11, an alloy originally developed as a wrought material, for thermal stability and to determine the feasibility for producing the alloy using powder metallurgy techniques. Seven compositions were melted and atomized, hot isostatically pressed, cross rolled to disks and heat treated. Tensile and stress rupture properties from room temperature to 870 C (1600 F) were determined in addition to thermal stability characteristics. Processing variables included hot isostatic pressing parameters and handling, cross rolling procedures and heat treatment cycles. NASA IIb-11E displayed the best combination of overall properties for service as a 760 C (1400 F) disk material. Its composition is 0.06 C, 8.5 Cr, 9.0 Co, 2.0 Mo, 7.1 W, 6.6 Ta, 4.5 Al, 0.75 Ti, 0.5 V, 0.7 Hf, 0.01 B, 0.05 Zr and balance Ni. While the alloy exhibits the highest 760 C (1400 F) rupture strength reported for any powder metallurgy disk alloy to date, additional studies to further evaluate the effects of heat treatment may be required. The alloy is not susceptible to topologically close-packed phase formation during thermal exposure at 870 C (1600 F) for 1,500 hours, but its mechanical property levels are lowered due to grain boundary carbide formation.

  6. The synthesis and characterization of Mg-Zn-Ca alloy by powder metallurgy process

    NASA Astrophysics Data System (ADS)

    Annur, Dhyah; Franciska P., L.; Erryani, Aprilia; Amal, M. Ikhlasul; Sitorus, Lyandra S.; Kartika, Ika

    2016-04-01

    Known for its biodegradation and biocompatible properties, magnesium alloys have gained many interests to be researched as implant material. In this study, Mg-3Zn-1Ca, Mg-29Zn-1Ca, and Mg-53Zn-4.3Ca (in wt%) were synthesized by means of powder metallurgy method. The compression strength and corrosion resistance of magnesium alloy were thoroughly examined. The microstructures of the alloy were characterized using optical microscopy, Scanning Electron Microscope, and also X-ray diffraction analysis. The corrosion resistance were evaluated using electrochemical analysis. The result indicated that Mg- Zn- Ca alloy could be synthesized using powder metallurgy method. This study showed that Mg-29Zn-1Ca would make the highest mechanical strength up to 159.81 MPa. Strengthening mechanism can be explained by precipitation hardening and grain refinement mechanism. Phase analysis had shown the formation of α Mg, MgO, and intermetallic phases: Mg2Zn11 and also Ca2Mg6Zn3. However, when the composition of Zn reach 53% weight, the mechanical strength will be decreasing. In addition, all of Mg-Zn-Ca alloy studied here had better corrosion resistance (Ecorr around -1.4 VSCE) than previous study of Mg. This study indicated that Mg- 29Zn- 1Ca alloy can be further analyzed to be a biodegradable implant material.

  7. Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

    NASA Astrophysics Data System (ADS)

    Chong-Lin, Jia; Chang-Chun, Ge; Qing-Zhi, Yan

    2016-02-01

    Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

  8. The combination of precipitation and dispersion hardening in powder metallurgy produced Cu-Ti-Si alloy

    SciTech Connect

    Bozic, D.; Dimcic, O.; Dimcic, B. Cvijovic, I.; Rajkovic, V.

    2008-08-15

    Microstructure and microhardness properties of precipitation hardened Cu-Ti and precipitation/dispersion hardened Cu-Ti-Si alloys have been analyzed. Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} (wt.%) atomized powders were characterized before and after consolidation by HIP (Hot Isostatic Pressing). Rapidly solidified powders and HIP-ed compacts were subsequently subjected to thermal treatment in hydrogen at temperatures between 300 and 600 deg. C. Compared to Cu-Ti powder particles and compacts, obtained by the same procedure, the strengthening effect in Cu-1.2Ti-3TiSi{sub 2} powder particles and compacts was much greater. The binary and ternary powders both reveal properties superior to those of Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} compacts. Microhardness analysis as a function of the aging temperature of Cu-1.2Ti-3TiSi{sub 2} alloy shows an interaction between precipitation and dispersion hardening which offers possibilities for an application at elevated temperatures.

  9. Assessment of Low Cycle Fatigue Behavior of Powder Metallurgy Alloy U720

    NASA Technical Reports Server (NTRS)

    Gabb, Tomothy P.; Bonacuse, Peter J.; Ghosn, Louis J.; Sweeney, Joseph W.; Chatterjee, Amit; Green, Kenneth A.

    2000-01-01

    The fatigue lives of modem powder metallurgy disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary as functions of variables the different steps of materials/component processing: powder atomization, consolidation, extrusion, forging, heat treating, and machining. It is important to understand the relationship between the statistical variations in life and these variables, as well as the change in life distribution due to changes in fatigue loading conditions. The objective of this study was to investigate these relationships in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were performed at 538 C (1000 F) at limited sets of test conditions. Analyses were performed to: (1) assess variations of microstructure, mechanical properties, and LCF failure initiation sites as functions of disk processing and loading conditions; and (2) compare mean and minimum fatigue life predictions using different approaches for modeling the data from assorted test conditions. Significant variations in life were observed as functions of the disk processing variables evaluated. However, the lives of all specimens could still be combined and modeled together. The failure initiation sites for tests performed at a strain ratio R(sub epsilon) = epsilon(sub min)/epsilon(sub max) of 0 were different from those in tests at a strain ratio of -1. An approach could still be applied to account for the differences in mean and maximum stresses and strains. This allowed the data in tests of various conditions to be combined for more robust statistical estimates of mean and minimum lives.

  10. Study of Metallic Carbide (MC) in a Ni-Co-Cr-Based Powder Metallurgy Superalloy

    NASA Astrophysics Data System (ADS)

    Ma, Wen-Bin; Liu, Guo-Quan; Hu, Ben-Fu; Hu, Peng-Hui; Zhang, Yi-Wen

    2014-01-01

    The evolution of carbides in a Ni-Cr-Co-based powder metallurgy (PM) superalloy in the as-atomized, as-atomized + annealed, hot isostatic pressed (HIPed) and HIPed + annealed conditions were systematically analyzed to understand the formation of blocky metallic carbide (MC) along the previous particle boundary (PPB). The results show that the carbides both on the powder surfaces and in the bulk of the powder particles are mainly fan-shaped MC whose decomposition temperatures are in the range of 1473 K to 1493 K (1200 C to 1220 C). PPB carbides in the HIPed alloy are mainly block-shaped MC, and the fan-shaped MC densely distributed in the area that have not been consumed by the recrystallized grains. The formation mechanism of PPB carbides can be described as follows: When the powders are HIPed at 1453 K (1180 C), the fan-shaped carbides are decomposed at the migrating boundaries of recrystallized grains, and the preferential precipitation of block-shaped MC at PPB is promoted by the carbide-forming elements released by the fan-shaped carbides. When the HIPed alloy is annealed at 1453 K (1180 C), the area fraction of PPB carbides increases with an increase in annealing time but that of the fan-shaped carbides exhibits opposite behavior. This proves the above formation mechanism of PPB carbides.

  11. Development of Cu-E-Glass Fiber Composites by Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Bhuyan, Pallabi; Singh, Harspreet; Kumar, Lailesh; Sharma, Nidhi; Panda, Deepankar; Verma, Deepanshu; NasmulAlam, Syed

    2016-02-01

    Cu-E glass fiber composites were developed with different vol. % of E-glass fiber (10, 20, 30 and 40 vol. %) by powder metallurgy route. Both as-received Cu and nanostructured Cu developed by milling as-received Cu powder for 20 h were used to develop various Cu-E-glass fiber composites. The effect of using as-received Cu powder and nanostructured Cu powder on the properties of the various Cu-E-glass fiber composites was analysed. The samples were sintered at 900oC for 1 h in inert atmosphere. The results show good bonding between the matrix and the reinforcement and there is homogeneous distribution of the reinforcement in the matrix.. The hardness of the Cu-E-glass fiber composites was found to increase from 0.8GPa to 2.7GPa with increase in vol. % of the glass fiber in case of unmilled and from 1.2GPa to 2.9GPa for the milled Cu-E-glass fiber composites. The as-milled Cu-E- glass fiber composites shows better densification and sinterability compared to the unmilled CuE-glass fiber composites

  12. The stress-corrosion cracking behavior of high-strength aluminum powder metallurgy alloys

    NASA Astrophysics Data System (ADS)

    Pickens, J. R.; Christodoulou, L.

    1987-01-01

    The susceptibility to stress-corrosion cracking (SCC) of rapidly solidified (RS) aluminum powder metallurgy (P/M) alloys 7090 and 7091, mechanically alloyed aluminum P/M alloy IN* 9052, and ingot metallurgy (I/M) alloys of similar compositions was compared using bolt-loaded double cantilever beam specimens. In addition, the effects of aging, grain size, grain boundary segregation, pre-exposure embrittlement, and loading mode on the SCC of 7091 were independently assessed. Finally, the data generated were used to elucidate the mechanisms of SCC in the three P/M alloys. The IN 9052 had the lowest SCC susceptibility of all alloys tested in the peak-strength condition, although no SCC was observed in the two RS alloys in the overaged condition. The susceptibility of the RS alloys was greater in the underaged than the peak-aged temper. We detected no significant differences in susceptibility of 7091 with grain sizes varying from 2 to 300 μm. Most of the crack advance during SCC of 7091 was by hydrogen embrittlement (HE). Furthermore, both RS alloys were found to be susceptible to preexposure embrittlement—also indicative of HE. The P/M alloys were less susceptible to SCC than the I/M alloys in all but one test.

  13. Mechanisms of fatigue crack retardation following single tensile overloads in powder metallurgy aluminum alloys

    NASA Technical Reports Server (NTRS)

    Bray, G. H.; Reynolds, A. P.; Starke, E. A., Jr.

    1992-01-01

    In ingot metallurgy (IM) alloys, the number of delay cycles following a single tensile overload typically increases from a minimum at an intermediate baseline stress intensity range, Delta-K(B), with decreasing Delta-K(B) approaching threshold and increasing Delta-K(B) approaching unstable fracture to produce a characteristic 'U' shaped curve. Two models have been proposed to explain this behavior. One model is based on the interaction between roughness and plasticity-induced closure, while the other model only utilizes plasticity-induced closure. This article examines these models, using experimental results from constant amplitude and single overload fatigue tests performed on two powder metallurgy (PM) aluminum alloys, AL-905XL and AA 8009. The results indicate that the 'U'-shaped curve is primarily due to plasticity-induced closure, and that the plasticity-induced retardation effect is through-thickness in nature, occurring in both the surface and interior regions. However, the retardation effect is greater at the surface, because the increase in plastic strain at the crack tip and overload plastic zone size are larger in the plane-stress surface regions than in the plane-strain interior regions. These results are not entirely consistent with either of the proposed models.

  14. Corrosion Resistance of Powder Metallurgy Processed TiC/316L Composites with Mo Additions

    NASA Astrophysics Data System (ADS)

    Lin, Shaojiang; Xiong, Weihao

    2015-06-01

    To find out the effects of Mo addition on corrosion resistance of TiC/316L stainless steel composites, TiC/316L composites with addition of different contents of Mo were prepared by powder metallurgy. The corrosion resistance of these composites was evaluated by the immersion tests and polarization curves experiments. Results indicated that Mo addition decreased the corrosion rates of TiC/316L composites in H2SO4 solution in the case of Mo content below 2% whereas it displayed an opposite effect when Mo content was above that value. It was found that with an increase in the Mo content, the pitting corrosion resistance increased monotonically for TiC/316L composites in NaCl solution.

  15. Abnormal magnetic behaviour of powder metallurgy austenitic stainless steels sintered in nitrogen

    NASA Astrophysics Data System (ADS)

    García, C.; Martin, F.; Blanco, Y.

    2009-10-01

    The magnetic response of AISI 304L and AISI 316L obtained through powder metallurgy and sintered in nitrogen were studied. AISI 304L sintered in nitrogen showed a ferromagnetic behaviour in as-sintered state while AISI 316L was paramagnetic. After solution annealing both were paramagnetic. Magnetic behaviour was analysed by using a vibrating sample magnetometer, a magnetic ferritscope and magnetic etching. A microstructural characterization was performed by means of optical metallography, X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDS). Some samples when needed were submitted to aged heat treatments at 675 and 875 °C for 90 min, 4, 6, 8 or 48 h. The main microstructural feature found was the presence of a lamellar constituent formed by nitride precipitates and an interlamellar matrix of austenite and/or ferrite. The abnormal magnetic response was explained based on this.

  16. Crack Formation in Powder Metallurgy Carbon Nanotube (CNT)/Al Composites During Post Heat-Treatment

    NASA Astrophysics Data System (ADS)

    Chen, Biao; Imai, Hisashi; Li, Shufeng; Jia, Lei; Umeda, Junko; Kondoh, Katsuyoshi

    2015-12-01

    After the post heat-treatment (PHT) process of powder metallurgy carbon nanotubes (CNT)/Al composites, micro-cracks were observed in the composites, leading to greatly degraded mechanical properties. To understand and suppress the crack formation, an in situ observation of CNT/Al composites was performed at elevated temperatures. PHT was also applied to various bulk pure Al and CNT/Al composites fabricated under different processes. It was observed that the composites consolidated by hot-extrusion might form micro-cracks, but those consolidated by spark plasma sintering (SPS) showed no crack after PHT. A high-temperature SPS process before hot-extrusion was effective to prevent crack formation. The release of residual stress in severe plastic deformed (SPD) materials was responsible for the cracking phenomena during the PHT process. Furthermore, a good particle bonding was essential and effective to suppress cracks for SPD materials in the PHT process.

  17. Particles into 410L Stainless Steel by a Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Zeybek, A.; Barroso, S. Pirfo; Chong, K. B.; Edwards, L.; Fitzpatrick, M. E.

    2014-06-01

    Addition of yttria to steels has been proposed for the fabrication of oxide-dispersion-strengthened materials for nuclear power applications. We have investigated materials prepared from 12 Cr martensitic stainless steel, AISI 410L, produced by powder metallurgy. Materials were produced with and without yttria addition, and two different sizes of yttria were used, 0.9 m and 50 nm. Tensile and mini-creep tests were performed to determine mechanical properties. Optical microscopy, SEM, TEM, and EDX analysis were used to investigate the microstructures and deformation mechanisms and to obtain information about non-metallic inclusion particles. SiO2, MnS, and Y2Si2O7 inclusion particles were observed. An SiO2 and Y2O3 interaction was seen to have occurred during the ball milling, which impaired the final mechanical properties. Small-angle neutron scattering experiments showed that the matrix chemistry prevented effective dissolution of the yttria.

  18. Artificial two-phase Nb-Ti nanostructures using powder metallurgy techniques

    SciTech Connect

    Jablonski, P.D.; Lee, P.J.; Larbalestier, D.C. )

    1994-08-08

    Several techniques to form artifical high critical current density superconducting Nb-Ti nanostructures have been reported. A drawback to virtually all of these techniques is that they require fabrication strains of 30 or more to reduce the second phase pinning center to the optimum 1--10 nm size at which critical current densities of 10[sup 3]--10[sup 4] A/mm[sup 2] are obtained. Here we describe a powder metallurgy process that yields 6020 A/mm[sup 2] at 2 T and 1470 A/mm[sup 2] at 5 T for an alloy with an upper critical field of [similar to]8 T within the same strain space ([similar to]13) employed in the conventional Nb-Ti fabrication process.

  19. The effect of thermal cycle on the microstructural development of a powder metallurgy superalloy braze material

    SciTech Connect

    Iacocca, R.G.

    1996-01-01

    This investigation examines the effect of thermal cycle on the microstructural development in a powder metallurgy (P/M) superalloy braze material. Using a vertical quench furnace, samples were quenched at various stages within the heat treatment. Microstructures were analyzed using optical microscopy and an electron microprobe. The results show that borides having a blocky morphology are stable at all temperatures, both compositionally and morphologically. Script phase undergoes a drastic change in chemistry; however, it remains morphologically stable throughout. The chemical analysis of the microstructure supports the conclusion that the extended heat treatment, which is employed in industry to homogenize the microstructure and dissolve detrimental phases, does not have a significant effect in preventing these phases from forming. By using shorter times at elevated temperatures, similar microstructures can be produced.

  20. Development of coarse grain structures in a powder metallurgy nickel base superalloy N18

    SciTech Connect

    Soucail, M.; Marty, M.; Octor, H.

    1996-02-15

    N18 is a new nickel base superalloy produced by powder metallurgy and specifically designed for high temperature turbine disk applications. The goal of the present work is to understand the conditions under which very large grains can grow in PM nickel base superalloy N18 and to identify the mechanisms responsible for this growth. Abnormal grain growth, defined as the growth of a few grains to very large sizes and possibly the elimination of the surrounding smaller grains, is studied under two different conditions. The first one refers to the growth observed in annealing materials that have been deformed in tension at elevated temperature. The second one refers to the growth consecutive to some particular time and temperature conditions of the final heat treatment.

  1. Microstructure and mechanical properties of P/M (powder metallurgy) Fe sub 3 Al alloys

    SciTech Connect

    Knibloe, J.R.; Wright, R.N. ); Sikka, V.K. )

    1990-01-01

    Alloys based on Fe{sub 3}Al have an equilibrium DO{sub 3} structure at low temperatures and transform to a B2 structure above about 550{degree}C. The influence of different rates of quenching from the B2 region to room temperature on the microstructure and mechanical properties of powder metallurgy (P/M) alloys with two different Cr contents has been examined. By optimizing the processing to maximize the amount of B2 order, room temperature ductility approaching 20% has been achieved although the fracture mode is primarily brittle cleavage. The refined microstructure resulting from P/M processing contributes to enhanced yield strength compared to ingot processed materials with similar ductility. Increasing the Cr content from 2 to 5% has little effect on mechanical properties. 8 refs., 12 figs., 2 tabs.

  2. Metallurgical variables influencing the corrosion susceptibility of a powder metallurgy SiCw/Al composite

    SciTech Connect

    Paciej, R.C.; Agarwala, V.S.

    1986-12-01

    Corrosion studies of a powder metallurgy SiC whisker (SiCw)/Al 7091 composite were performed. The plate material, heat treated to T-6 and T-7 tempers, exhibited preferential corrosion of the surface layers. The regions of corrosion susceptibility resulted from improper processing and thermal treatments. Cold-worked regions resulting from extrusion were not completely removed by the conventional solution treatment and thus appeared as more corrosion susceptible. Large void volume fraction and excessive segregation of SiCw was also noted. Electrochemical, microscopic, and analytical techniques were used in these investigations. Attempts were made to remove the cold-worked regions and study the corrosion properties. A comparative analysis of the results is discussed.

  3. Microstructure Evolution during Supersolvus Heat Treatment of a Powder Metallurgy Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; McClary, K. E.; Rollett, A. D.; Roberts, C. G.; Payton, E. J.; Zhang, F.; Gabb, T. P.

    2012-05-01

    Microstructure evolution during the supersolvus heat treatment of a powder-metallurgy, low-solvus, high-refractory (LSHR) superalloy was established. For this purpose, three lots of LSHR with varying initial carbon/boron composition and thermomechanical history were subjected to a series of short-time (induction) and long-time (furnace) heat treatments followed by scanning electron microscopy/electron backscatter diffraction and quantitative metallography. The size of the (pinned) gamma grains exhibited a limited dependence on heating rate and soak time at peak temperature, and it was generally smaller than the predictions based on the classic Smith-Zener model. The differences were rationalized in terms of stereological and pinning-particle location effects. Observations of limited coarsening of the carbide/boride pinning particles were interpreted in the context of prior experimental observations and a modified Lifshitz-Slyosov-Wagner model applied previously for the coarsening of compound phases in steels.

  4. Accelerated Threshold Fatigue Crack Growth Effect-Powder Metallurgy Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Piascik, R. S.; Newman, J. A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low (Delta) K, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = K(sub min)/K(sub max)). The near threshold accelerated FCG rates are exacerbated by increased levels of K(sub max) (K(sub max) = 0.4 K(sub IC)). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and K(sub max) influenced accelerated crack growth is time and temperature dependent.

  5. Shock Compaction of Exchange-Coupled Nanocomposite Magnetic Powders

    NASA Astrophysics Data System (ADS)

    Jin, Z. Q.; Chen, K. H.; Li, J.; Zeng, H.; Liu, P.; Wang, Z. L.; Thadhani, N. N.

    2004-07-01

    Shock compaction was used to consolidate exchange-coupled R2Fe14B/α-Fe (R=Nd, Pr) hard/soft phase nanocomposite powders using a three-capsule plate-impact gas-gun loading system. Design of the consolidation fixture, densification conditions, and starting powder properties allowed control of the final density and microstructure of the shock-compacted samples. Highly dense compacts (˜99% of full density) with minimal interparticle melted/re-solidified zones and free from macrocracks were obtained under optimum consolidation conditions, in which case a laminar microstructure of the ribbon-shaped powders was observed. TEM characterization revealed complete retention of the nanostructure of the hard and soft phases, which grain sizes were within 20-25 nm in the final shock-compacted composite magnets. Retention of nanostructure ensured exchange coupling between the hard and soft phases, resulting in magnetic properties in the shock consolidated compacts similar to those of starting powders.

  6. Effect of porosity on the thermal conductivity of copper processed by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Vincent, C.; Silvain, J. F.; Heintz, J. M.; Chandra, N.

    2012-03-01

    Powder metallurgy is a preferred method of processing copper-carbon composites due to the non-wetting nature of these materials. Porosities are inherently introduced in these material systems, and adversely affect the thermal conductivity of the composite material, among other factors including interfaces and reinforcement distribution. In this work, we focus on the matrix material of pure copper and systematically analyzed the effect of volume fraction of porosities on the thermal conductivity. Spherical and dendritic copper powder materials were processed and it was found that the surface chemistry and morphology of particles affected the thermal conductivity apart from the porosity values. In order to study the effect of porosities alone, dentritic powder was used in the study. The thermal conductivity vs. porosity behavior showed three distinct domains. In all the domains the thermal conductivity decreases as volume fraction of porosities increases; however, in domain II, the decrease was much steeper than the other two. We are able to explain the variation based on the presence of interconnected and open pores in domain III to closed pores in domain I, and the transition occurring in domain II. None of the existing models capture the overall behavior. However, if we specifically account for the variation of number of grain boundaries with sintering, then the modified EMT model can match the experimental data.

  7. Applied mechanics modeling of granulated ceramic powder compaction

    SciTech Connect

    Mahoney, F.M.; Readey, M.J.

    1995-08-01

    In ceramic manufacturing processes such as dry-pressing, correlations between applied compacting pressure and resultant powder compact density are essential for defining reliable process conditions for ceramic components. Pressure-density diagrams have been developed as a tool for both process control and for understanding the compaction behavior of different powders. These types of diagrams, however, pertain only to the averag@ properties of a powder compact and do not address a significant issue in powder compaction processes: the formation of density gradients within the compact. Continuum-based mechanics models of varying complexity have addressed the influence of frictional forces acting at the powder-die wall interface which dissipate the applied pressure throughout the compact. Resulting pressure distribution models are then typically coupled with empirical functions relating pressure and density to obtain a green density distribution in the compact. All of these models predict similar trends; however, none predict the distribution with sufficient accuracy to be considered as a design tool for industrial applications.

  8. Stress-strain behavior and shape memory effect in powder metallurgy TiNi alloys

    SciTech Connect

    Kato, H.; Koyari, T.; Miura, S. . Dept. of Engineering Science); Tokizane, M. . Dept. of Mechanical Engineering)

    1994-04-01

    The shape memory properties of the TiNi alloy produced by a powder metallurgical method have been evaluated from tensile stress-strain curves. The contamination of the powders during atomization can be suppressed by applying the Plasma Rotating Electrode Process (P-REP), so that the compact made by Hot Isostatic Pressing (HIP) is expected to exhibit the shape memory effect identical to the typical alloy grown from melt. The fracture behavior of the P/M alloy is also studied, and the improvement of fracture strength of the P/M alloy is attempted.

  9. Starch Consolidation as a New Process for Manufacturing Powder Metallurgy High-Speed Steels

    NASA Astrophysics Data System (ADS)

    Romano, P.; Velasco, F. J.; Torralba, J. M.

    2007-01-01

    The development of a new method called “starch consolidation,” suitable for the production of powder metallurgy (P/M) high-speed steel (HSS) components has been studied. Samples have been consolidated using 1.5, 3.5, and 5vol pct starch and up to 60vol pct powder. The high solid loading was achieved by stabilizing the repulsive forces with a small addition (0.01wt pct) of a dispersant (polyacrylic acid) that resulted in accurate fluidity and consolidation of the prepared slurries. After shaping of the samples, the bending strength of the green bodies was evaluated. Debinding cycles were optimized by comparing carbon and oxygen content in argon, in N2-5H2, and in pure hydrogen. The three atmospheres showed no significant differences in carbon elimination. To determine the influence of H2 in a nitrogen-rich atmosphere during sintering, tests were performed at 1230°C in a N2-5H2 and in a nitrogen atmosphere. Pure nitrogen resulted in a microstructure formed by smaller carbides. Heat treatments were performed on the samples with the compositions that gave the best combination of properties. A hardness of 800HV and a bending strength of 1475MPa were obtained.

  10. Niobium-titanium superconductors produced by powder metallurgy having artificial flux pinning centers

    DOEpatents

    Jablonski, Paul D.; Larbalestier, David C.

    1993-01-01

    Superconductors formed by powder metallurgy have a matrix of niobium-titanium alloy with discrete pinning centers distributed therein which are formed of a compatible metal. The artificial pinning centers in the Nb-Ti matrix are reduced in size by processing steps to sizes on the order of the coherence length, typically in the range of 1 to 10 nm. To produce the superconductor, powders of body centered cubic Nb-Ti alloy and the second phase flux pinning material, such as Nb, are mixed in the desired percentages. The mixture is then isostatically pressed, sintered at a selected temperature and selected time to produce a cohesive structure having desired characteristics without undue chemical reaction, the sintered billet is reduced in size by deformation, such as by swaging, the swaged sample receives heat treatment and recrystallization and additional swaging, if necessary, and is then sheathed in a normal conducting sheath, and the sheathed material is drawn into a wire. The resulting superconducting wire has second phase flux pinning centers distributed therein which provide enhanced J.sub.ct due to the flux pinning effects.

  11. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    DOE PAGESBeta

    Harp, Jason Michael; Lessing, Paul Alan; Hoggan, Rita Elaine

    2015-06-21

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinationsmore » that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ±0.06 g/cm3. Additional characterization of the pellets by scaning electron microscopy and X-ray diffraction has also been performed. As a result, pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon.« less

  12. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    NASA Astrophysics Data System (ADS)

    Harp, Jason M.; Lessing, Paul A.; Hoggan, Rita E.

    2015-11-01

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ± 0.06 g/cm3. Additional characterization of the pellets by scanning electron microscopy and X-ray diffraction has also been performed. Pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon.

  13. Characterization and mechanical properties of ultrahigh boron steels produced by powder metallurgy

    SciTech Connect

    Jimenez, J.A.; Gonzalez-Doncel, G.; Ruano, O.A.

    1996-07-01

    The present work is part of an investigation into the use of rapid solidification and powder metallurgy techniques to obtain iron-boron alloys with good mechanical properties. Two Fe-B binary alloys and two ultrahigh boron tool steels were gas atomized and consolidated by hot isostatic pressing (HIP) at temperatures ranging from 700 C to 1,100 C to have a fine microstructure. Optimum properties were achieved for the binary alloys at low consolidation temperatures, since the solidification microstructure from the original powders is eliminated and, at the same time, fine microstructures and low porosity are obtained in the alloys. At high temperatures and low strain rates, three of the four alloys exhibited low stress exponents, but only the Fe-2.2 pct B alloy showed tensile elongations higher than 100 pct. At low temperatures, only the Fe-2.2 pct B alloy deformed plastically. This alloy showed values of tensile elongation and ultimate tensile strength that were strongly dependent on testing and consolidation temperatures.

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

    PubMed

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

    2015-04-01

    Titanium and its alloys are characterized by an exceptional combination of properties like high strength, good corrosion resistance and biocompatibility which makes them suitable materials for biomedical prosthesis and devices. The wrought Ti-6Al-4V alloy is generally favored in comparison to other metallic biomaterials due to its relatively low elastic modulus and it has been long used to obtain products for biomedical applications. In this work an alternative route to fabricate biomedical implants made out of the Ti-6Al-4V alloy is investigated. Specifically, the feasibility of the conventional powder metallurgy route of cold uniaxial pressing and sintering is addressed by considering two types of powders (i.e. blended elemental and prealloyed). The characterization of physical properties, chemical analysis, mechanical behavior and microstructural analysis is carried out in-depth and the properties are correlated among them. On the base of the results found, the produced alloys are promising materials for biomedical applications as well as cheaper surgical devices and tools. PMID:25686965

  15. Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Xu, Shenghang; Wang, Xin; Li, Kaiyang; Liu, Bin; Wu, Hong; Tang, Huiping

    2016-03-01

    Ultra-high strength and ductile powder metallurgy (PM) binary Ti-20at.%Ta alloy has been fabricated via sintering from elemental Ti and Ta powders and subsequent hot swaging and annealing. The microstructural evolution and mechanical properties in each stage were evaluated. Results show that inhomogeneous microstructures with Ti-rich and Ta-rich areas formed in the as-sintered Ti-Ta alloys due to limited diffusion of Ta. In addition, Kirkendall porosity was observed as a result of the insufficient diffusion of Ta. Annealing at 1000°C for up to 24 h failed to eliminate the pores. Hot swaging eliminated the residual sintering porosity and created a lamellar microstructure, consisting of aligned Ta-enriched and Ti-enriched phases. The hot-swaged and annealed PM Ti-20Ta alloy achieved an ultimate tensile strength of 1600 MPa and tensile elongation of more than 25%, due to its unique lamellar microstructure including the high toughness of Ta-enriched phases, the formation of α phase in the β matrix and the refined lamellae.

  16. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    SciTech Connect

    Harp, Jason Michael; Lessing, Paul Alan; Hoggan, Rita Elaine

    2015-06-21

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ±0.06 g/cm3. Additional characterization of the pellets by scaning electron microscopy and X-ray diffraction has also been performed. As a result, pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon.

  17. An investigation of wear behaviors of different Monel alloys produced by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Esgin, U.; Özyürek, D.; Kaya, H.

    2016-04-01

    In the present study, wear behaviors of Monel 400, Monel 404, Monel R-405 and Monel K-500 alloys produced by Powder Metallurgy (P/M) method were investigated. These compounds prepared from elemental powders were cold-pressed (600 MPa) and then, sintered at 1150°C for 2 hours and cooled down to the room temperature in furnace environment. Monel alloys produced by the P/M method were characterized through scanning electron microscope (SEM+EDS), X-ray diffraction (XRD), hardness and density measurements. In wear tests, standard pin-on-disk type device was used. Specimens produced within four different Monel Alloys were tested under 1ms-1 sliding speed, under three different loads (20N, 30N and 40N) and five different sliding distances (400-2000 m). The results show that Monel Alloys have γ matrix and that Al0,9Ni4,22 intermetallic phase was formed in the structure. Also, the highest hardness value was measured with the Monel K-500 alloy. In wear tests, the maximum weight loss according to the sliding distance, was observed in Monel 400 and Monel 404 alloys while the minimum weight loss was achieved by the Monel K-500 alloy.

  18. Linking compaction dynamics to the flow properties of powders

    NASA Astrophysics Data System (ADS)

    Lumay, G.; Vandewalle, N.; Bodson, C.; Delattre, L.; Gerasimov, O.

    2006-08-01

    The authors have investigated the flow properties of powders by using two classical techniques based on the shear stress measurements and the count of intermittent avalanches, respectively. Results are compared with measurements of the compaction dynamics. Strong correlations are evidenced between compaction relaxation parameters and free flow characteristics. Those correlations are given by semiempirical laws based on physical arguments. This work opens perspectives in powder technology and the knowledge on granular matter.

  19. Shock compaction of magnet powder using underwater shock wave

    SciTech Connect

    Kubota, Shiro; Fujita, Masahiro; Itoh, Shigeru

    1996-12-31

    In order to get a high plug density (over 90%), the authors tried a direct consolidation of the magnet powder using the converging underwater shock wave created by the underwater explosion of explosives. The processes of the consolidation of the magnet powder were investigated by numerical calculation. They obtained the parameters of the EOS (Petrie-Page model) for Magnet powder using quasi-static loading experiments. Moreover, the characteristics of the shock compaction assembly were also verified.

  20. PREPARATION OF METAL POWDER COMPACTS PRIOR TO PRESSING

    DOEpatents

    Mansfield, H.

    1958-08-26

    A method of fabricating uranium by a powder metallurgical technique is described. It consists in introducing powdered uranium hydride into a receptacle shaped to coincide with the coatour of the die cavity and heating the hydride so that it decomposes to uranium metal. The metal particles cohere in the shapw of the receptacle and thereafter the prefurmed metal powder is pressed and sintered to obtain a dense compact.

  1. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder-Metallurgy-Produced Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Muth, T. R.; Yamamoto, Y.; Frederick, D. A.; Contescu, C. I.; Chen, W.; Lim, Y. C.; Peter, W. H.; Feng, Z.

    2013-05-01

    An investigation was undertaken using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas-forming species. PM-titanium made from revert scrap, where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal and minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders are critical for achieving equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  2. Precipitation in cold-rolled Al–Sc–Zr and Al–Mn–Sc–Zr alloys prepared by powder metallurgy

    SciTech Connect

    Vlach, M.; Stulikova, I.; Smola, B.; Kekule, T.; Kudrnova, H.; Danis, S.; Gemma, R.; Ocenasek, V.; Malek, J.; Tanprayoon, D.; Neubert, V.

    2013-12-15

    The effects of cold-rolling on thermal, mechanical and electrical properties, microstructure and recrystallization behaviour of the AlScZr and AlMnScZr alloys prepared by powder metallurgy were studied. The powder was produced by atomising in argon with 1% oxygen and then consolidated by hot extrusion at 350 °C. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission and scanning electron microscopy, X-ray diffraction and electron backscatter diffraction. Fine (sub)grain structure developed and fine coherent Al{sub 3}Sc and/or Al{sub 3}(Sc,Zr) particles precipitated during extrusion at 350 °C in the alloys studied. Additional precipitation of the Al{sub 3}Sc and/or Al{sub 3}(Sc,Zr) particles and/or their coarsening was slightly facilitated by the previous cold rolling. The presence of Sc,Zr-containing particles has a significant antirecrystallization effect that prevents recrystallization at temperatures minimally up to 420 °C. The precipitation of the Al{sub 6}Mn- and/or Al{sub 6}(Mn,Fe) particles of a size ∼ 1.0 μm at subgrain boundaries has also an essential antirecrystallization effect and totally suppresses recrystallization during 32 h long annealing at 550 °C. The texture development of the alloys seems to be affected by high solid solution strengthening by Mn. The precipitation of the Mn-containing alloy is highly enhanced by a cold rolling. The apparent activation energy of the Al{sub 3}Sc particles formation and/or coarsening and that of the Al{sub 6}Mn and/or Al{sub 6}(Mn,Fe) particle precipitation in the powder and in the compacted alloys were determined. The cold deformation has no effect on the apparent activation energy values of the Al{sub 3}Sc-phase and the Al{sub 6}Mn-phase precipitation. - Highlights: • The Mn, Sc and Zr additions to Al totally suppresses recrystallization at 550 °C. • The Sc,Zr-containing particle precipitation is slightly facilitated by cold rolling. • The Mn-containing particle precipitation is highly enhanced by cold rolling. • Cold rolling has no effect on activation energy of the Al{sub 3}Sc and Al{sub 6}Mn precipitation. • The texture development is affected by high solid solution strengthening by Mn.

  3. Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel

    SciTech Connect

    Godec, Matjaz; Batic, Barbara Setina; Mandrino, Djordje; Nagode, Ales; Leskovsek, Vojteh; Skapin, Sreco D.; Jenko, Monika

    2010-04-15

    A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbides were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.

  4. Copper-Carbon and Aluminum-Carbon Composites Fabricated by Powder Metallurgy Processes

    NASA Astrophysics Data System (ADS)

    Silvain, Jean-François; Veillère, Amélie; Lu, Yongfeng

    2014-07-01

    The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials, with high thermal conductivity and thermal- expansion coefficient compatible with chip materials still ensuring the reliability of the power modules. In this context, metal matrix composites: carbon fibers and diamond-reinforced copper and aluminum matrix composites among them are considered very promising as a next generation of thermal-management materials in power electronic packages. These composites exhibit enhanced thermal properties compared to pure copper combined with lower density. This article presents the fabrication techniques of copper/carbon fibers and copper/diamond and aluminum/carbon fibers composite films by powder metallurgy and hot pressing. The thermal analyses clearly indicate that interfacial treatments are required in these composites to achieve high thermomechanical properties. Interfaces (through novel chemical and processing methods), when selected carefully and processed properly will form the right chemical/mechanical link between metal and carbon, enhancing all the desired thermal properties while minimizing the deleterious effect.

  5. Analysis of Load Transfer Mechanism in Cu Reinforced with Carbon Nanotubes Fabricated by Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Akbarpour, Mohammad Reza

    2016-04-01

    Abstract: In this research, ductile and high-strength Cu-carbon nanotube (Cu-CNT) composites with different volume fractions of CNTs were fabricated using powder metallurgy route including mechanical milling and hot pressing and microstructure and tensile properties of the resulting materials were studied. Microstructural characterization through scanning electron microscope and quantifying the CNT agglomeration revealed that uniform dispersion of CNTs in Cu matrix decreases with increasing CNT volume fraction. In case of the higher volume fraction of CNTs (i.e., 8 vol.%), ~ 40% of CNTs were observed as agglomerates in the microstructure. Compared to unreinforced Cu, the yield and ultimate tensile strengths increased considerably (about 33% and 12%, respectively) with incorporation of CNTs up to 4 vol.%, but remained constant afterward. Meanwhile, the elongation decreased from 15.6% for Cu to 6.9% for Cu with 8 vol.% CNT. The relationship between the change in yield strength of the composite and the microstructure was investigated using analytical models. The results showed good consistency between calculated and measured data when the negative effect of CNT agglomerates in the models were taken into account.

  6. Superplastic behavior in a powder-metallurgy TiAl alloy with a metastable microstructure

    SciTech Connect

    Nieh, T.G.; Hsiung, L.M.; Wadsworth, J.

    1997-12-01

    Superplasticity in a powder-metallurgy TiAl alloy (Ti-47Al-2Cr-2Nb) with a metastable microstructure has been studied. Samples were tested at temperatures ranging from 650 to 1100{degrees}C, and at strain rate ranging from 10{sup -6} to 10{sup -4} s{sup -1}. An elongation value of over 300 obtained at a strain rate of 2 x 10{sup -5} s{sup -1} and at a temperature as lo as 800{degrees}C, which is close to the ductile-to-brittle-transition temperature. This is in contrast to the prior major observations of superplastic behaviors in TiAl in which typical temperatures of 1000{degrees}C have usually been required for superplasticity. It is proposed that the occurrence of superplasticity at 8000{degrees}C in the present alloy is caused by the presence of a B2 phase. During superplastic deformation (grain boundary sliding), the soft P grains accommodate sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process. The final microstructure consists of stable, equiaxed y+a{sub 2} grains.

  7. Creep behavior of an aluminum 2024 alloy produced by powder metallurgy

    SciTech Connect

    Kloc, L.; Spigarelli, S.; Cerri, E.; Evangelista, E.; Langdon, T.G.

    1997-02-01

    Creep tests were conducted over a range of temperatures from 523 to 603 K on an unreinforced 2024 Al alloy fabricated by powder metallurgy processing. The creep curves under all testing conditions exhibit a brief quasi-steady-state condition and then a very extended tertiary stage leading to failure. A logarithmic plot of the minimum creep rate against the applied stress leads to a high and variable stress exponent and a high apparent activation energy. Prior to creep testing, the specimens contained large particles identified as Al{sub 2}Cu and Al{sub 2}CuMg. A precipitation of fine particles occurred during testing; this was especially evident in the long-term tests at the highest testing temperature. An analysis of the creep data is developed based on incorporating a threshold stress into the creep equation and using measurements of particle densities in order to include the influence of continuous precipitation during testing. The significance of the threshold stress is examined, and it is shown that the analysis leads to a stress exponent of 5 and an activation energy approximately equal to the value for lattice self-diffusion in pure aluminum.

  8. Application of powder metallurgy techniques to produce improved bearing elements for liquid rocket engines

    NASA Technical Reports Server (NTRS)

    Moracz, D. J.; Shipley, R. J.; Moxson, V. S.; Killman, R. J.; Munson, H. E.

    1992-01-01

    The objective was to apply powder metallurgy techniques for the production of improved bearing elements, specifically balls and races, for advanced cryogenic turbopump bearings. The materials and fabrication techniques evaluated were judged on the basis of their ability to improve fatigue life, wear resistance, and corrosion resistance of Space Shuttle Main Engine (SSME) propellant bearings over the currently used 440C. An extensive list of candidate bearing alloys in five different categories was considered: tool/die steels, through hardened stainless steels, cobalt-base alloys, and gear steels. Testing of alloys for final consideration included hardness, rolling contact fatigue, cross cylinder wear, elevated temperature wear, room and cryogenic fracture toughness, stress corrosion cracking, and five-ball (rolling-sliding element) testing. Results of the program indicated two alloys that showed promise for improved bearing elements. These alloys were MRC-2001 and X-405. 57mm bearings were fabricated from the MRC-2001 alloy for further actual hardware rig testing by NASA-MSFC.

  9. A Novel Ni-Containing Powder Metallurgy Steel with Ultrahigh Impact, Fatigue, and Tensile Properties

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Wei; Shu, Guo-Jiun; Chang, Shih-Ying; Lin, Bing-Hao

    2014-08-01

    The impact toughness of powder metallurgy (PM) steel is typically inferior, and it is further impaired when the microstructure is strengthened. To formulate a versatile PM steel with superior impact, fatigue, and tensile properties, the influences of various microstructures, including ferrite, pearlite, bainite, and Ni-rich areas, were identified. The correlations between impact toughness with other mechanical properties were also studied. The results demonstrated that ferrite provides more resistance to impact loading than Ni-rich martensite, followed by bainite and pearlite. However, Ni-rich martensite presents the highest transverse rupture strength (TRS), fatigue strength, tensile strength, and hardness, followed by bainite, pearlite, and ferrite. With 74 pct Ni-rich martensite and 14 pct bainite, Fe-3Cr-0.5Mo-4Ni-0.5C steel achieves the optimal combination of impact energy (39 J), TRS (2170 MPa), bending fatigue strength at 2 × 106 cycles (770 MPa), tensile strength (1323 MPa), and apparent hardness (38 HRC). The impact energy of Fe-3Cr-0.5Mo-4Ni-0.5C steel is twice as high as those of the ordinary high-strength PM steels. These findings demonstrate that a high-strength PM steel with high-toughness can be produced by optimized alloy design and microstructure.

  10. Analysis of Load Transfer Mechanism in Cu Reinforced with Carbon Nanotubes Fabricated by Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Akbarpour, Mohammad Reza

    2016-05-01

    In this research, ductile and high-strength Cu-carbon nanotube (Cu-CNT) composites with different volume fractions of CNTs were fabricated using powder metallurgy route including mechanical milling and hot pressing and microstructure and tensile properties of the resulting materials were studied. Microstructural characterization through scanning electron microscope and quantifying the CNT agglomeration revealed that uniform dispersion of CNTs in Cu matrix decreases with increasing CNT volume fraction. In case of the higher volume fraction of CNTs (i.e., 8 vol.%), ~ 40% of CNTs were observed as agglomerates in the microstructure. Compared to unreinforced Cu, the yield and ultimate tensile strengths increased considerably (about 33% and 12%, respectively) with incorporation of CNTs up to 4 vol.%, but remained constant afterward. Meanwhile, the elongation decreased from 15.6% for Cu to 6.9% for Cu with 8 vol.% CNT. The relationship between the change in yield strength of the composite and the microstructure was investigated using analytical models. The results showed good consistency between calculated and measured data when the negative effect of CNT agglomerates in the models were taken into account.

  11. Tribological properties of PM212 - A high temperature, self-lubricating, powder metallurgy composite

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Sliney, Harold E.

    1990-01-01

    This paper describes a research program to develop and evaluate a new high temperature, self-lubricating powder metallurgy composite, PM212. PM212 has the same composition as the plasma-sprayed coating, PS212, which contains 70 wt percent metal-bonded chromium carbide, 15 wt percent silver and 15 wt percent barium fluoride/calcium fluoride eutectic. The carbide acts as a wear resistant matrix and the silver and fluorides act as low and high temperature lubricants, respectively. The material is prepared by sequential cold press, cold isostatic pressing and sintering techniques. In this study, hemispherically tipped wear pins of PM212 were prepared and slid against superalloy disks at temperatures from 25 to 850 C in air in a pin-on-disk tribometer. Friction coefficients range from 0.29 to 0.38 and the wear of both the composite pins and superalloy disks was moderate to low in the 10(exp -5) to 10(exp -6) cubic mm/N-m range. Preliminary tests indicate that the material has a compressive strength of at least 130 MPa over the entire temperature range of 25 to 900 C. This material has promise for use as seal inserts, bushings, small inside diameter parts and other applications where plasma-sprayed coatings are impractical or too costly.

  12. Tribological properties of PM212: A high-temperature, self-lubricating, powder metallurgy composite

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Sliney, Harold E.

    1989-01-01

    This paper describes a research program to develop and evaluate a new high temperature, self-lubricating powder metallurgy composite, PM212. PM212 has the same composition as the plasma-sprayed coating, PS212, which contains 70 wt percent metal-bonded chromium carbide, 15 wt percent silver and 15 wt percent barium fluoride/calcium fluoride eutectic. The carbide acts as a wear resistant matrix and the silver and fluorides act as low and high temperature lubricants, respectively. The material is prepared by sequential cold press, cold isostatic pressing and sintering techniques. In this study, hemispherically tipped wear pins of PM212 were prepared and slid against superalloy disks at temperatures from 25 to 850 C in air in a pin-on-disk tribometer. Friction coefficients range from 0.29 to 0.38 and the wear of both the composite pins and superalloy disks was moderate to low in the 10(exp -5) to 10(exp -6) cubic mm/N-m range. Preliminary tests indicate that the material has a compressive strength of at least 130 MPa over the entire temperature range of 25 to 900 C. This material has promise for use as seal inserts, bushings, small inside diameter parts and other applications where plasma-sprayed coatings are impractical or too costly.

  13. The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloys

    NASA Astrophysics Data System (ADS)

    Harf, Fredric H.

    1985-06-01

    Nickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of γ' particles in a γ matrix. The higher cobalt-content alloys contained larger amounts of the finest γ' particles, and had the lowest γ-γ' lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650°C, the rupture lives at 650 and 760°C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the γ' particle size distribution and the γ-γ' mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.

  14. Development and Processing of Novel Aluminum Powder Metallurgy Materials for Heat Sink Applications

    NASA Astrophysics Data System (ADS)

    Smith, L. J. B.; Corbin, S. F.; Hexemer, R. L.; Donaldson, I. W.; Bishop, Donald Paul

    2014-02-01

    The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacturing. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research, the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In the second, the thermal properties of sintered products were studied in detail. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity, and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99 pct theoretical density and exhibited thermal conductivity that ranged from 179 to 225 W/m K. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and, in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061.

  15. Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

    2011-01-01

    The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

  16. The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloys

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1985-01-01

    Nickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of gamma-prime particles in a gamma matrix. The higher cobalt-content alloys contained larger amounts of the finest gamma-prime particles, and had the lowest gamma-gamma-prime lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650 gamma C, the rupture lives at 650 and 760 C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the gamma-prime particle size distribution and the gamma-gamma-prime mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.

  17. Application of powder metallurgy technique to produce improved bearing elements for cryogenic aerospace engine turbopumps

    NASA Technical Reports Server (NTRS)

    Moxson, V. S.; Moracz, D. J.; Bhat, B. N.; Dolan, F. J.; Thom, R.

    1987-01-01

    Traditionally, vacuum melted 440C stainless steel is used for high performance bearings for aerospace cryogenic systems where corrosion due to condensation is a major concern. For the Space Shuttle Main Engine (SSME), however, 440C performance in the high-pressure turbopumps has been marginal. A basic assumption of this study was that powder metallurgy, rather than cast/wrought, processing would provide the finest, most homogeneous bearing alloy structure. Preliminary testing of P/M alloys (hardness, corrosion resistance, wear resistance, fatigue resistance, and fracture toughness) was used to 'de-select' alloys which did perform as well as baseline 440C. Five out of eleven candidate materials (14-4/6V, X-405, MRC-2001, T-440V, and D-5) based on preliminary screening were selected for the actual rolling-sliding five-ball testing. The results of this test were compared with high-performance vacuum-melted M50 bearing steel. The results of the testing indicated outstanding performance of two P/M alloys, X-405 and MRC-2001, which eventually will be further evaluated by full-scale bearing testing.

  18. Characterisation of titanium-titanium boride composites processed by powder metallurgy techniques

    SciTech Connect

    Selva Kumar, M.; Chandrasekar, P.; Chandramohan, P.; Mohanraj, M.

    2012-11-15

    In this work, a detailed characterisation of titanium-titanium boride composites processed by three powder metallurgy techniques, namely, hot isostatic pressing, spark plasma sintering and vacuum sintering, was conducted. Two composites with different volume percents of titanium boride reinforcement were used for the investigation. One was titanium with 20% titanium boride, and the other was titanium with 40% titanium boride (by volume). Characterisation was performed using X-ray diffraction, electron probe micro analysis - energy dispersive spectroscopy and wavelength dispersive spectroscopy, image analysis and scanning electron microscopy. The characterisation results confirm the completion of the titanium boride reaction. The results reveal the presence of titanium boride reinforcement in different morphologies such as needle-shaped whiskers, short agglomerated whiskers and fine plates. The paper also discusses how mechanical properties such as microhardness, elastic modulus and Poisson's ratio are influenced by the processing techniques as well as the volume fraction of the titanium boride reinforcement. - Highlights: Black-Right-Pointing-Pointer Ti-TiB composites were processed by HIP, SPS and vacuum sintering. Black-Right-Pointing-Pointer The completion of Ti-TiB{sub 2} reaction was confirmed by XRD, SEM and EPMA studies. Black-Right-Pointing-Pointer Hardness and elastic properties of Ti-TiB composites were discussed. Black-Right-Pointing-Pointer Processing techniques were compared with respect to their microstructure.

  19. Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

    NASA Technical Reports Server (NTRS)

    Telesman, J.; Gabb, T. P.; Yamada, Y.; Ghosn, L. J.; Jayaraman, N.

    2012-01-01

    A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

  20. Dense and Homogeneous Compaction of Fine Ceramic and Metallic Powders: High-Speed Centrifugal Compaction Process

    SciTech Connect

    Suzuki, Hiroyuki Y.

    2008-02-15

    High-Speed Centrifugal Compaction Process (HCP) is a variation of colloidal compacting method, in which the powders sediment under huge centrifugal force. Compacting mechanism of HCP differs from conventional colloidal process such as slip casting. The unique compacting mechanism of HCP leads to a number of characteristics such as a higher compacting speed, wide applicability for net shape formation, flawless microstructure of the green compacts, etc. However, HCP also has several deteriorative characteristics that must be overcome to fully realize this process' full potential.

  1. Effects of porosity on corrosion resistance of Mg alloy foam produced by powder metallurgy technology

    SciTech Connect

    Aghion, E. Perez, Y.

    2014-10-15

    Magnesium alloy foams have the potential to serve as structural material for regular light-weight applications as well as for biodegradable scaffold implants. However, their main disadvantage relates to the high reactivity of magnesium and consequently their natural tendency to corrode in regular service conditions and in physiological environments. The present study aims at evaluating the effect of porosity on the corrosion resistance of MRI 201S magnesium alloy foams in 0.9% NaCl solution and in phosphate buffer saline solution as a simulated physiological electrolyte. The magnesium foams were produced by powder metallurgy technology using space-holding particles to control the porosity content. Machined chips were used as raw material for the production of Mg alloy powder by milling process. The microstructure of the foams was examined using optical and scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis. The corrosion behavior was evaluated by immersion test and potentiodynamic polarization analysis. The results obtained clearly demonstrate that the porosity has a significant effect on the corrosion resistance of the tested foams. Foams with 14–19% porosity have a corrosion rate of 4–10 mcd and 7–15 mcd in NaCl and phosphate buffer saline solution, respectively, compared to only 0.10 mcd for the same alloy in as cast conditions. This increased corrosion degradation of the Mg foams by more than one order of magnitude compared to the cast alloy may limit their potential application in regular and physiological environments. - Highlights: • Porosity has a detrimental effect on corrosion resistance of MRI 201S Mg foams. • 14–19% porosity increases the corrosion rate by more than one order of magnitude. • Accelerated corrosion limits the use of foams in regular/physiological environments.

  2. Structure investigations of ferromagnetic Co-Ni-Al alloys obtained by powder metallurgy.

    PubMed

    Maziarz, W; Dutkiewicz, J; Lityńska-Dobrzyńska, L; Santamarta, R; Cesari, E

    2010-03-01

    Elemental powders of Co, Ni and Al in the proper amounts to obtain Co(35)Ni(40)Al(25) and Co(40)Ni(35)Al(25) nominal compositions were ball milled in a high-energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X-ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat-treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered gamma phase (gamma'), often appearing as twins, and a small amount of the L1(0) ordered martensite. PMID:20500399

  3. Distribution of Inclusion-Initiated Fatigue Cracking in Powder Metallurgy Udimet 720 Characterized

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kantzos, Pete T.; Barrie, Robert; Telesman, Jack; Ghosn, Louis J.; Gabb, Timothy P.

    2004-01-01

    In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the distribution of intrinsic defects. In powder metallurgy (PM) alloys, relatively large defects occur rarely enough that a typical characterization with a limited number of small volume fatigue test specimens will not adequately sample inclusion-initiated damage. Counterintuitively, inclusion-initiated failure has a greater impact on the distribution in PM alloy fatigue lives because they tend to have fewer defects than their cast and wrought counterparts. Although the relative paucity of defects in PM alloys leads to higher mean fatigue lives, the distribution in observed lives tends to be broader. In order to study this important failure initiation mechanism without expending an inordinate number of specimens, a study was undertaken at the NASA Glenn Research Center where known populations of artificial inclusions (seeds) were introduced to production powder. Fatigue specimens were machined from forgings produced from the seeded powder. Considerable effort has been expended in characterizing the crack growth rate from inclusion-initiated cracks in seeded PM alloys. A rotating and translating positioning system, with associated software, was devised to map the surface inclusions in low-cycle fatigue (LCF) test bars and to monitor the crack growth from these inclusions. The preceding graph illustrates the measured extension in fatigue cracks from inclusions on a seeded LCF test bar subjected to cyclic loading at a strain range of 0.8 percent and a strain ratio (max/min) of zero. Notice that the observed inclusions fall into three categories: some do not propagate at all (arrest), some propagate with a decreasing crack growth rate, and a few propagate at increasing rates that can be modeled by fracture mechanics. The following graph shows the measured inclusion-initiated crack growth rates from 10 interrupted LCF tests plotted against stress intensities calculated for semi-elliptical cracks with the observed surface lengths. The expected scatter in the crack growth rates for stress intensity ranges near threshold is observed. These data will be used to help determine the distribution in growth rates of cracks emanating from inclusions as well as the proportion of cracks that arrest under various loading conditions.

  4. Microwave Heating, Isothermal Sintering, and Mechanical Properties of Powder Metallurgy Titanium and Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Luo, S. D.; Guan, C. L.; Yang, Y. F.; Schaffer, G. B.; Qian, M.

    2013-04-01

    This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ≥1573 K (1300 °C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from -100 mesh hydride-dehydride (HDH) Ti powder to ~95.0 pct theoretical density (TD) at 1573 K (1300 °C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al2O3-SiC insulation-susceptor package, despite the high vacuum used (≤4.0 × 10-3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing.

  5. Powder Metallurgy of Uranium Alloy Fuels for TRU-Burning Reactors Final Technical Report

    SciTech Connect

    Sean M. McDeavitt

    2011-04-29

    Overview Fast reactors were evaluated to enable the transmutation of transuranic isotopes generated by nuclear energy systems. The motivation for this was that TRU isotopes have high radiotoxicity and relatively long half-lives, making them unattractive for disposal in a long-term geologic repository. Fast reactors provide an efficient means to utilize the energy content of the TRUs while destroying them. An enabling technology that requires research and development is the fabrication metallic fuel containing TRU isotopes using powder metallurgy methods. This project focused upon developing a powder metallurgical fabrication method to produce U-Zr-transuranic (TRU) alloys at relatively low processing temperatures (500ºC to 600ºC) using either hot extrusion or alpha-phase sintering for charecterization. Researchers quantified the fundamental aspects of both processing methods using surrogate metals to simulate the TRU elements. The process produced novel solutions to some of the issues relating to metallic fuels, such as fuel-cladding chemical interactions, fuel swelling, volatility losses during casting, and casting mold material losses. Workscope There were two primary tasks associated with this project: 1. Hot working fabrication using mechanical alloying and extrusion • Design, fabricate, and assemble extrusion equipment • Extrusion database on DU metal • Extrusion database on U-10Zr alloys • Extrusion database on U-20xx-10Zr alloys • Evaluation and testing of tube sheath metals 2. Low-temperature sintering of U alloys • Design, fabricate, and assemble equipment • Sintering database on DU metal • Sintering database on U-10Zr alloys • Liquid assisted phase sintering on U-20xx-10Zr alloys Appendices Outline Appendix A contains a Fuel Cycle Research & Development (FCR&D) poster and contact presentation where TAMU made primary contributions. Appendix B contains MSNE theses and final defense presentations by David Garnetti and Grant Helmreich outlining the beginning of the materials processing setup. Also included within this section is a thesis proposal by Jeff Hausaman. Appendix C contains the public papers and presentations introduced at the 2010 American Nuclear Society Winter Meeting. Appendix A—MSNE theses of David Garnetti and Grant Helmreich and proposal by Jeff Hausaman A.1 December 2009 Thesis by David Garnetti entitled “Uranium Powder Production Via Hydride Formation and Alpha Phase Sintering of Uranium and Uranium-Zirconium Alloys for Advanced Nuclear Fuel Applications” A.2 September 2009 Presentation by David Garnetti (same title as document in Appendix B.1) A.3 December 2010 Thesis by Grant Helmreich entitled “Characterization of Alpha-Phase Sintering of Uranium and Uranium-Zirconium Alloys for Advanced Nuclear Fuel Applications” A.4 October 2010 Presentation by Grant Helmreich (same title as document in Appendix B.3) A.5 Thesis Proposal by Jeffrey Hausaman entitled “Hot Extrusion of Alpha Phase Uranium-Zirconium Alloys for TRU Burning Fast Reactors” Appendix B—External presentations introduced at the 2010 ANS Winter Meeting B.1 J.S. Hausaman, D.J. Garnetti, and S.M. McDeavitt, “Powder Metallurgy of Alpha Phase Uranium Alloys for TRU Burning Fast Reactors,” Proceedings of 2010 ANS Winter Meeting, Las Vegas, Nevada, USA, November 7-10, 2010 B.2 PowerPoint Presentation Slides from C.1 B.3 G.W. Helmreich, W.J. Sames, D.J. Garnetti, and S.M. McDeavitt, “Uranium Powder Production Using a Hydride-Dehydride Process,” Proceedings of 2010 ANS Winter Meeting, Las Vegas, Nevada, USA, November 7-10, 2010 B.4. PowerPoint Presentation Slides from C.3 B.5 Poster Presentation from C.3 Appendix C—Fuel cycle research and development undergraduate materials and poster presentation C.1 Poster entitled “Characterization of Alpha-Phase Sintering of Uranium and Uranium-Zirconium Alloys” presented at the Fuel Cycle Technologies Program Annual Meeting C.2 April 2011 Honors Undergraduate Thesis by William Sames, Research Fellow, entitled “Uranium Metal Powder Production, Particle Distribution Analysis, and Reaction Rate Studies of a Hydride-Dehydride Process”  

  6. Rapidly solidified powder metallurgy of Al-Ti-Fe-X alloys

    SciTech Connect

    Kawamura, Yoshihito; Inoue, Akihisa; Takagi, Makoto; Ohta, Hidenobu; Imura, Toru; Masumoto, Tsuyoshi

    1999-04-23

    Mechanical properties of powder metallurgy (P/M) aluminum alloys have been improved through a rapid solidification (RS) technique. High-strength RS P/M aluminum alloys were recently developed in Al-Ni-(Y or Ce)-(Co, Ti or Zr) systems containing from 89 to 91 at% Al. The alloy systems have a glass-forming ability, resulting in easy attainment of nanocrystalline structure. Recently, the authors have reported that Al{sub 93}Ti{sub 3.5}Fe{sub 3.5}RS P/M alloys exhibited tensile strength of 786 MPa, plastic elongation of 3.2%, high thermal stability up to 600 K, low density of 2.90 gcm{sup {minus}3}, high Young`s modulus of 91 GPa and low coefficient of thermal expansion of 20.2 {times} 10{sup {minus}6} K{sup {minus}1}. The Al-Ti-Fe P/M alloys are expected to be applied as elevated-temperature materials such as Al-Fe-Ce, Al-Fe-Mo, Al-Fe-V-Si and Al-Cr-Zr RS P/M alloys, because the Ti and Fe elements exhibit limited solid solubility and low diffusivity in aluminum. The transition metals of V, Cr, Mo and Zr have low diffusivity in aluminum. The addition of these elements to the Al-Ti-Fe alloys is expected to improve its thermal stability and elevated-temperature strength. The purpose of this paper is to report the synthesis of elevated-temperature Al-Ti-Fe-X (X = V, Cr, Mo and Zr) RS P/M alloys.

  7. Processing and development of aluminum-silicon powder metallurgy alloys for hot forging technologies

    NASA Astrophysics Data System (ADS)

    Mosher, Winston G. E.

    The growing field of aluminum powder metallurgy (PM) brings promise to an economical and environmental demand for the production of high strength, light weight aluminum engine components. To tackle the limited selection of readily available light alloy blends, an experimental hypoeutectic AlSi alloy was chosen for study. The optimal processing route for this alloy was determined and the mechanical properties were examined. In an effort to further enhance the mechanical properties of the alloys, post sinter forging was investigated. This body of work consists of an introduction to relevant topics in PM, aluminum alloys, and forging followed by three sections of results and discussion. Each represents an accepted or submitted Journal Manuscript intended for journal publication. These sections deliver detailed experimental procedures, results and discussion for the development of the experimental PM alloy Al-65i, a comparison of hot deformation behaviours of Al-65i and Alumix-231 Al5i PM alloys, and their mechanical properties observed upon hot densification. A final section was added to summarize the important findings from each experiment. In the development of Al-65i, the alloy was able to achieve a high sintered density approaching 98%, and a yield strength of 232 MPa in the T6 condition. Upon hot upset forging, the experimental alloy achieved an average density of 99.6% (+/- 0.2%) while the commercial alloy (Alumix-231) achieved 98.3% (+/- 0.6%) of its theoretical density. It was found that the experimentally obtained peak flow stresses for each material studied could be very closely approximated using the semi-empirical Zener-Hollomon models. Upon hot densification it was found that all the mechanical properties of the Al-65i alloy were significantly enhanced. However, due to the fracturing of 5i particles during deformation, Alumix-231 experienced a reduction in density and UT5, while making improvements in ductility.

  8. Liquid Phase Sintering of Boron-Containing Powder Metallurgy Steel with Chromium and Carbon

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Wei; Fan, Yu-Chi; Huang, Her-Yueh; Cai, Wen-Zhang

    2015-11-01

    Liquid phase sintering is an effective method to improve the densification of powder metallurgy materials. Boron is an excellent alloying element for liquid phase sintering of Fe-based materials. However, the roles of chromium and carbon, and particularly that of the former, on liquid phase sintering are still undetermined. This study demonstrated the effects of chromium and carbon on the microstructure, elemental distribution, boride structure, liquid formation, and densification of Fe-B-Cr and Fe-B-Cr-C steels during liquid phase sintering. The results showed that steels with 0.5 wt pct C densify faster than those without 0.5 wt pct C. Moreover, although only one liquid phase forms in Fe-B-Cr steel, adding 0.5 wt pct C reduces the formation temperature of the liquid phase by about 50 K (°C) and facilitates the formation of an additional liquid, resulting in better densification at 1473 K (1200 °C). In both Fe-B-Cr and Fe-B-Cr-C steels, increasing the chromium content from 1.5 to 3 wt pct raises the temperature of liquid formation by about 10 K (°C). Thermodynamic simulations and experimental results demonstrated that carbon atoms dissolved in austenite facilitate the eutectic reaction and reduce the formation temperature of the liquid phase. In contrast, both chromium and molybdenum atoms dissolved in austenite delay the eutectic reaction. Furthermore, the 3Cr-0.5Mo additive in the Fe-0.4B steel does not change the typical boride structure of M2B. With the addition of 0.5 wt pct C, the crystal structure is completely transformed from M2B boride to M3(B,C) boro-carbide.

  9. Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride Powder

    NASA Astrophysics Data System (ADS)

    Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

    2007-06-01

    Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is in contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from input and propagated manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The hardness measurements throughout the bulk of the shock compacted titanium diboride are discussed.

  10. Effects of copper content on the shell characteristics of hollow steel spheres manufactured using an advanced powder metallurgy technique

    NASA Astrophysics Data System (ADS)

    Sazegaran, Hamid; Kiani-Rashid, Ali-Reza; Khaki, Jalil Vahdati

    2016-04-01

    Metallic hollow spheres are used as base materials in the manufacture of hollow sphere structures and metallic foams. In this study, steel hollow spheres were successfully manufactured using an advanced powder metallurgy technique. The spheres' shells were characterized by optical microscopy in conjunction with microstructural image analysis software, scanning electron microscopy (SEM), energy- dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The microscopic evaluations revealed that the shells consist of sintered iron powder, sintered copper powder, sodium silicate, and porosity regions. In addition, the effects of copper content on various parameters such as shell defects, microcracks, thickness, and porosities were investigated. The results indicated that increasing the copper content results in decreases in the surface fraction of shell porosities and the number of microcracks and an increase in shell thickness.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. Effect of coating time on corrosion behavior of electroless nickel-phosphorus coated powder metallurgy iron specimens

    SciTech Connect

    Singh, D.; Balasubramaniam, R.; Dube, R.K.

    1995-08-01

    Powder metallurgy iron specimens with porosities in the range 0% to 2% were electroless coated with nickel-phosphorus alloy from baths containing sodium hypophosphite (NaH{sub 2}PO{sub 2}{center_dot}H{sub 2}O). The effect of coating time on thickness and phosphorus content of the deposit was analyzed. The free corrosion potentials and corrosion rates of the coated specimens were obtained by the Tafel extrapolation method in 1.0 M hydrochloric acid (HCl) solution. Corrosion rates of the coated specimens after heat treatment also were studied. The observed corrosion characteristics were explained by the mixed-potential theory.

  13. Study of alumina-trichite reinforcement of a nickel-based matric by means of powder metallurgy

    NASA Technical Reports Server (NTRS)

    Walder, A.; Hivert, A.

    1982-01-01

    Research was conducted on reinforcing nickel based matrices with alumina trichites by using powder metallurgy. Alumina trichites previously coated with nickel are magnetically aligned. The felt obtained is then sintered under a light pressure at a temperature just below the melting point of nickel. The halogenated atmosphere technique makes it possible to incorporate a large number of additive elements such as chromium, titanium, zirconium, tantalum, niobium, aluminum, etc. It does not appear that going from laboratory scale to a semi-industrial scale in production would create any major problems.

  14. Fatigue behavior of highly porous titanium produced by powder metallurgy with temporary space holders.

    PubMed

    Özbilen, Sedat; Liebert, Daniela; Beck, Tilmann; Bram, Martin

    2016-03-01

    Porous titanium cylinders were produced with a constant amount of temporary space holder (70 vol.%). Different interstitial contents were achieved by varying the starting powders (HDH vs. gas atomized) and manufacturing method (cold compaction without organic binders vs. warm compaction of MIM feedstocks). Interstitial contents (O, C, and N) as a function of manufacturing were measured by chemical analysis. Samples contained 0.34-0.58 wt.% oxygen, which was found to have the greatest effect on mechanical properties. Quasi-static mechanical tests under compression at low strain rate were used for reference and to define parameters for cyclic compression tests. Not unexpectedly, increased oxygen content increased the yield strength of the porous titanium. Cyclic compression fatigue tests were conducted using sinusoidal loading in a servo-hydraulic testing machine. Increased oxygen content was concomitant with embrittlement of the titanium matrix, resulting in significant reduction of compression cycles before failure. For samples with 0.34 wt.% oxygen, R, σ(min) and σ(max) were varied systematically to estimate the fatigue limit (~4 million cycles). Microstructural changes induced by cyclic loading were then characterized by optical microscopy, SEM and EBSD. PMID:26706551

  15. Preparation of Cu and Fly Ash Composite by Powder Metallurgy Technique

    SciTech Connect

    Chew, P. Y.; Lim, P. S.; Ng, M. C.; Zahi, S.; You, A. H.

    2011-03-30

    Cu and Fly Ash (FA) mixtures with different weight percentages were prepared. Pellets of the mixture powder were produced with the dimension of 17.7 mm in diameter and 10-15 mm in height. These different composites were compacted at a constant pressure of 280 MPa. One of the selected weight percentages was then compacted to form into pellet and sintered at different temperatures which were at 900, 950 and 1000 deg. C respectively for 2 hours. Density of green pellet was measured before sintered in furnace. After sintering, all the pellets with different temperatures were re-weighed and sintered density were calculated. The densification of the green and sintered pellets was required to be measured as one of the parameter in selection of the best material properties. Porosity of the pellet shall not be ignored in order to analyze the close-packed particles stacking in the pellet. SEM micrograph had been captured to observe the presence of pores and agglomeration of particles in the sample produced.

  16. Compact, Non-Pneumatic Rock-Powder Samplers

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Bar-Cohen, Yoseph; Badescu, Mircea; Bao, Xiaoqi; Chang, Zensheu; Jones, Christopher; Aldrich, Jack

    2008-01-01

    Tool bits that automatically collect powdered rock, permafrost, or other hard material generated in repeated hammering action have been invented. The present invention pertains to the special case in which it is desired to collect samples in powder form for analysis by x-ray diffraction and possibly other techniques. The present invention eliminates the need for both the mechanical collection equipment and the crushing chamber and the pneumatic collection equipment of prior approaches, so that it becomes possible to make the overall sample-acquisition apparatus more compact.

  17. Effect of sintering conditions on the microstructural and mechanical characteristics of porous magnesium materials prepared by powder metallurgy.

    PubMed

    Čapek, Jaroslav; Vojtěch, Dalibor

    2014-02-01

    There has recently been an increased demand for porous magnesium materials in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such materials. Many works have dealt with the preparation of porous magnesium; however, the effect of sintering conditions on material properties has rarely been investigated. In this work, we investigated porous magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of porous magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of porous magnesium. PMID:24411347

  18. Laser photothermal non-destructive metrology of cracks in un-sintered powder metallurgy manufactured automotive transmission sprockets

    NASA Astrophysics Data System (ADS)

    Tolev, J.; Mandelis, A.

    2010-03-01

    A non-contact and non-intrusive method of revealing crack presence in un-sintered (green) automotive transmission parts (sprockets), manufactured by means of a powder metallurgy technology based on analysis of photo-thermal radiometric (PTR) signals and their statistical analysis was developed. The inspection methodology relies on the interaction of a modulated laser generated thermal wave with the potential crack and the resulting change in amplitude and phase of the detected signal [1-5]. The crack existence at points in high stress regions of a group of green (unsintered) sprockets was evaluated through frequency scans. The results were validated by independent destructive cross-sectioning of the sprockets following sintering and polishing. Examination of the sectioned sprockets under a microscope at the locations where signal changes was used for correlation with the PTR signals. Statistical analysis confirmed the capabilities of the method to detect the presence of hairline cracks (~5 - 10 μm size) with excellent sensitivity (91%) and good accuracy (78%) and specificity (61%). This measurement technique and the associated statistical analysis can be used as a simple and reliable on-line inspection methodology of industrial powder metallurgy manufactured steel products for non-destructive quality and feedback control of the parts forming process.

  19. Effects of powder characteristics on impact initiated combustion in aluminum powder compacts

    NASA Astrophysics Data System (ADS)

    Breidenich, Jennifer; Thadhani, Naresh

    2015-06-01

    The processes leading to the initiation of impact induced combustion in aluminum powder compacts under uniaxial stress loading are investigated as a function of different powder characteristics. The mechanistic processes leading to reaction initiation in the Al samples are investigated via high speed and IR imaging of light associated with the reaction. Compacts composed of larger size particles of aluminum (approximately 70(μm) are shown to be more sensitive to impact initiated combustion than those composed of smaller particle sizes. Mechanical pre-activation by high energy ball milling (HEBM) of the Al powders shows increased reactivity. Images captured during compaction and deformation, revealing light emission, are correlated with CTH simulations indicating areas of localized strain and heating during deformation of the particles. These observations are used to explain the impact-initiated combustion sensitivity of Al powders as a function of powder characteristics and to understand the processes leading to reaction initiation. This work is supported by DTRA Project No. HDTRA-1-12-1-0052.

  20. Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Telesman, J.; Kantzos, P. T.; Bonacuse, P. J.; Barrie, R. L.

    2002-01-01

    The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.

  1. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

    PubMed Central

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-01-01

    Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240–260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180–210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time. PMID:26837848

  2. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

    NASA Astrophysics Data System (ADS)

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-02-01

    Stereocomplexation between enantiomeric poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time.

  3. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency.

    PubMed

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-01-01

    Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time. PMID:26837848

  4. Processing and microstructural evolution of powder metallurgy Zn-22 Pct Al eutectoid alloy containing nanoscale dispersion particles

    NASA Astrophysics Data System (ADS)

    Xun, Y.; Rodriguez, R.; Lavernia, E. J.; Mohamed, F. A.

    2005-10-01

    The present article deals with the processing and microstructural evolution of powder metallurgy (PM) Zn-22Al pct eutectoid alloy. The powder material was produced through inert gas atomization and then cryomilled in liquid nitrogen. The milled powder particles were consolidated by hot isostatic pressing (“hipping”) followed by thermomechanical treatment, resulting in a two-phase microstructure. The microstructures were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The principal processing factors and microstructural characteristics associated with the major processing steps, including spray atomization, mechanical milling (MM), consolidation, and heat treatment, were evaluated and discussed. Hot isostatic pressing and extrusion followed by heat treatment to produce the superplastic structure (Al-rich phase and Zn-rich phase) are effective in elimination porosity. A TEM examination of the microstructure of the alloy after processing reveals the presence of nanodispersion particles that are not uniformly distributed. The formation of the dispersions was attributed to the interaction between the powder material (primarily Al phase) and environmental elements such as oxygen and nitrogen during milling. Moreover, the size and distribution of the dispersions present in the bulk material met the anticipated requirements for serving as inhibitors for grain growth and barriers for dislocation movement. The TEM observations on crept specimens reveal extensive dislocation/dispersion interactions.

  5. The roles of rare earth dispersoids and process route on the low cycle fatigue behavior of a rapidly solidified powder metallurgy titanium alloy

    SciTech Connect

    Gigliotti, M.F.X. ); Woodfield, A.P. )

    1993-08-01

    Low cycle fatigue tests were conducted at 482C (900F) on forgings and extrusions of a rapidly solidified powder metallurgy titanium base alloy with and without rare earth additions. The variables studied were process temperature and heat treatment. Rare earth dispersions reduced fatigue life, and fracture surfaces indicated internal fatigue crack initiation at rare earth particles.

  6. Shape memory characteristics of powder metallurgy processed Ti50Ni50 alloy

    NASA Astrophysics Data System (ADS)

    Kim, Yeon-wook; Jeon, Kyung-su

    Ti50Ni50 shape memory alloy powders were prepared by inert gas atomization and the powders were consolidated by spark plasma sintering (SPS) to fabricated dense bulk samples. Martensitic transformation temperatures and microstructures of the asatomized powders and the consolidated disks were investigated. DSC and XRD analysis showed that the B2-B19' martensitic transformation occurred in the powders and the disks. The martensitic transformation start temperature (Ms) of the powders was 22.9∘ C. However, the Ms of the SPS disk was 65.9∘ C. It is considered that this increase in transformation temperature is ascribed to the microstructural change during SPS processing.

  7. Corrosion properties in a simulated body fluid of Mg/β-TCP composites prepared by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Wu, Ze-hong; Zhou, Hong; Liao, Zhi-dong; Zhang, Heng-fei

    2012-11-01

    Magnesium matrix composites (MMC) reinforced with 5wt% tricalcium phosphate (TCP) particles were prepared by powder metallurgy. Pure magnesium (CP-Mg) was fabricated by the same procedure for comparison. Scanning electron microscopy and energy- dispersive X-ray spectroscopy analyses revealed that TCP particles were distributed homogeneously in the MMC. In order to investigate the corrosion properties, MMC samples were immersed in a simulated body fluid (SBF) at 310±0.5 K for 72 h. The mass loss of the samples in SBF and the pH values of the SBF were evaluated. Moreover, electrochemical measurements were conducted in the SBF. It was shown that the corrosion rate of the MMC decreased with the addition of TCP compared with CP-Mg. Hydroxyapatite was formed on the surface of MMC samples after immersion in the SBF for 72 h but not on the surface of CP-Mg.

  8. Influence of cold rolling and strain rate on plastic response of powder metallurgy and chemical vapor deposition rhenium

    SciTech Connect

    Koeppel, B.J.; Subhash, G.

    1999-10-01

    The plastic response of two kinds of rhenium processed via powder metallurgy (PM) and chemical vapor deposition (CVD) were investigated under uniaxial compression over a range of strain rates. The PM rhenium, further cold rolled to 50 and 80 pct of the original thickness, was also investigated to assess the influence of cold work on the plastic behavior. A strong basal texture was detected in all the preceding materials as a result of processing and cold work. Both CVD and PM rhenium exhibited an increase in yield strength and flow stress with increasing strain rate. In PM rhenium, cold work resulted in an increase in hardness and yield strength and a decrease in the work hardening rate. The deformed microstructures revealed extensive twinning in CVD rhenium. At large strains, inhomogeneous deformation mode in the form of classical cup and cone fracture was noticed.

  9. Mechanical strength and thermophysical properties of PM212: A high temperature self-lubricating powder metallurgy composite

    NASA Technical Reports Server (NTRS)

    Edwards, Phillip M.; Sliney, Harold E.; Dellacorte, Christopher; Whittenberger, J. Daniel; Martineau, Robert R.

    1990-01-01

    A powder metallurgy composite, PM212, composed of metal bonded chromium carbide and solid lubricants is shown to be self-lubricating to a maximum application temperature of 900 C. The high temperature compressive strength, tensile strength, thermal expansion and thermal conductivity data needed to design PM212 sliding contact bearings and seals are reported for sintered and isostatically pressed (HIPed) versions of PM212. Other properties presented are room temperature density, hardness, and elastic modulus. In general, both versions appear to have adequate strength to be considered as sliding contact bearing materials, but the HIPed version, which is fully dense, is much stronger than the sintered version which contains about 20 percent pore volume. The sintered material is less costly to make, but the HIPed version is better where high compressive strength is important.

  10. The wear properties of in-situ 7075 Al-Ti composites produced by powder metallurgy route

    NASA Astrophysics Data System (ADS)

    Ay, H.; Özyurek, D.; Yıldırım, M.; Bostan, B.

    2016-04-01

    In this study, the wear properties of in-situ 7075 Al-Ti composites produced by powder metallurgy route were investigated. Different amount of Ti (2, 4, 6 %) added to gas atomized 7075 Al alloy powders and they were mixed in turbula with 47rpm for 45 minutes. Then the mixed powders were pre-shaped by press under 600 MPa pressure. The samples were cooled in the furnace after sintered at 580 °C for 4 hours in the atmosphere controlled furnace. Standard metallographic process such as grinding, polishing and etching were applied to sintered samples. The hardness values were measured. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) examines were carried out. The wear tests were performed in a pin-on disc type wear apparatus with 1 ms-1 sliding speed at six different sliding distance (500-3000 m) under 30 N loads. As a result of studies, hardness values were increased with increasing Ti content, in addition the weight losses were decreased with increasing Ti amount.

  11. Sintering stress and microstructure in ceramic powder compacts

    SciTech Connect

    Chu, May-Ying California Univ., Berkeley, CA . Dept. of Materials Science and Mineral Engineering)

    1990-08-01

    The behavior of the sintering stress and microstructure during sintering is studied under various thermal and physical conditions. Specifically, the study includes sintering under isothermal or constant heating rate conditions; and altering the starting compact structure by pre-coarsening to increase the particle size, or by compaction to increase the starting density. Loading dilatometry is used to measure the ratio of the densification strain rate to the creep strain rate and the continuous shrinkage history of the systems. The data show that the ratio of the densification to the creep strain rate is remarkably constant within a wide temperature range for densification, from the earliest stages of densification to at least the onset of the final stage. As a consequence, the sintering stress, which is proportional to the strain rate ratio, is nearly independent of sintered density or of temperature. Analysis leads to a simple method for determining the simultaneous densification strain rate over the creep strain rate ratio. A rigorous densification strain rate equation is derived for a model system. The constant sintering stress allows progress on formulating a sintering equation to predict the densification behavior of powder compacts. Analysis of dilatometry data from compacts sintered at various heating rates, and of numerical computations, indicate the need to include separate coarsening processes with different activation energies. The same model is used to describe the differences in pore spacing evolution between pre-coarsened and as-received systems.

  12. Analysis of the Cold Compaction Behavior of Titanium Powders: A Comprehensive Inter-model Comparison Study of Compaction Equations

    NASA Astrophysics Data System (ADS)

    Machaka, Ronald; Chikwanda, Hilda K.

    2015-09-01

    A brief background to compaction equations and their application to titanium powder is presented. The behavior and mechanisms of densification in selected titanium powders is critically analyzed by means of a comprehensive inter-model comparison of existing compaction equations. The results are discussed in terms of the comparative evaluation of cold uniaxial compaction tests of sponge Ti, CP TiH2, CP Grade 2 Ti, and TiH2-SS316L nanocomposite powder samples, which were conducted at applied compaction pressures of up to 1250 MPa.

  13. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the Compendex database). Published Search

    SciTech Connect

    Not Available

    1993-06-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 250 citations and includes a subject term index and title list.)

  14. Effect of Cu addition on the martensitic transformation of powder metallurgy processed Ti–Ni alloys

    SciTech Connect

    Kim, Yeon-wook; Choi, Eunsoo

    2014-10-15

    Highlights: • M{sub s} of Ti{sub 50}Ni{sub 50} powders is 22 °C, while M{sub s} of SPS-sintered porous bulk increases up to 50 °C. • M{sub s} of Ti{sub 50}Ni{sub 40}Cu{sub 20} porous bulk is only 2 °C higher than that of the powders. • Recovered stain of porous TiNi and TiNiCu alloy is more than 1.5%. - Abstract: Ti{sub 50}Ni{sub 50} and Ti{sub 50}Ni{sub 30}Cu{sub 20} powders were prepared by gas atomization and their transformation behaviors were examined by means of differential scanning calorimetry and X-ray diffraction. One-step B2–B19’ transformation occurred in Ti{sub 50}Ni{sub 50} powders, while Ti{sub 50}Ni{sub 30}Cu{sub 20} powders showed B2–B19 transformation behavior. Porous bulks with 24% porosity were fabricated by spark plasma sintering. The martensitic transformation start temperature (50 °C) of Ti{sub 50}Ni{sub 50} porous bulk is much higher than that (22 °C) of the as-solidified powders. However, the martensitic transformation start temperature (35 °C) of Ti{sub 50}Ni{sub 30}Cu{sub 20} porous bulk is almost the same as that (33 °C) of the powders. When the specimens were compressed to the strain of 8% and then unloaded, the residual strains of Ti{sub 50}Ni{sub 50} and Ti{sub 50}Ni{sub 30}Cu{sub 20} alloy bulks were 3.95 and 3.7%, respectively. However, these residual strains were recovered up to 1.7% after heating by the shape memory phenomenon.

  15. A compact high-resolution X-ray powder diffractometer

    PubMed Central

    Fewster, Paul F.; Trout, David R. D.

    2013-01-01

    A new powder diffractometer operating in transmission mode is described. It can work as a rapid very compact instrument or as a high-resolution instrument, and the sample preparation is simplified. The incident beam optics create pure Cu K?1 radiation, giving rise to peak widths of ?0.1 in 2? in compact form with a sample-to-detector minimum radius of 55?mm, reducing to peak widths of <0.05 in high-resolution mode by increasing the detector radius to 240?mm. The resolution of the diffractometer is shown to be governed by a complex mixture of angular divergence, sample size, diffraction effects and the dimensions of the detector pixels. The data can be collected instantaneously, which combined with trivial sample preparation and no sample alignment, makes it a suitable method for very rapid phase identification. As the detector is moved further from the sample, the angular step from the pixel dimension is reduced and the resolution improves significantly for very detailed studies, including structure determination and analysis of the microstructure. The advantage of this geometry is that the resolution of the diffractometer can be calculated precisely and the instrumental artefacts can be analysed easily without a sample present. The performance is demonstrated with LaB6 and paracetamol, and a critical appraisal of the uncertainties in the measurements is presented. The instantaneous data collection offers possibilities in dynamic experiments. PMID:24282331

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

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.

    2016-03-01

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

  17. Physical chemistry of the powder metallurgy of beryllium: Chemical characterization of the powder in relation to its granularity

    NASA Astrophysics Data System (ADS)

    Bracconi, Pierre; Buisson, Laurent; Bonnet, Christian

    1996-02-01

    Combining the systematic quantitative chemical analysis of the light impurities H, C, N, and O, the quantitative thermal desorption of molecular H2O and H2, and X ray diffractometry of various size fractions of a commercial Be powder (SP-65 grade from Brush-Wellman) allowed the precise de-termination of the mean composition and equivalent mean thickness of the surface impurity phases in the passivation-contamination layer on the surface of the particles. The overall surface stoichi-ometry is as follows: 0.2 BeOcrystallized, 0.8 [BeO - 0.59 H2O]amorphous, 0.14 H2Oads The result of the elemental analysis by X-ray photoelectron spectroscopy of the unetched surface of a powder pellet is compared. Analysis of the metallic impurities reveals increased concentrations of Mg, Ca, Ti, and Cr in the finest fraction, presumably due to the liberation of fine particles of intermetallic phases by attrition.

  18. Physical chemistry of the powder metallurgy of beryllium: Chemical characterization of the powder in relation to its granularity

    SciTech Connect

    Bracconi, P.; Buisson, L.; Bonnet, C.

    1996-02-01

    Combining the systematic quantitative chemical analysis of the light impurities H, C, N, and O, the quantitative thermal desorption of molecular H{sub 2}O and H{sub 2}, and X-ray diffractometry of various size fractions of a commercial Be powder (SP-65 grade from Brush-Wellman) allowed the precise determination of the mean composition and equivalent mean thickness of the surface impurity phases in the passivation-contamination layer on the surface of the particles. The overall surface stoichiometry is as follows: 0.2 BeO{sub crystallized}, 0.8 [BeO {minus} 0.59 H{sub 2}O]{sub amorphous}, 0.14 H{sub 2}O{sub ads}. The result of the elemental analysis by X-ray photoelectron spectroscopy of the unetched surface of a powder pellet is compared. Analysis of the metallic impurities reveals increased concentrations of Mg, Ca, Ti, and Cr in the finest fraction, presumably due to the liberation of fine particles of intermetallic phases by attrition

  19. Investigation of Die Stress Profiles during Powder Compaction using Instrumented Die

    SciTech Connect

    Hong, Sung-tae; Hovanski, Yuri; Lavender, Curt A.; Weil, K. Scott

    2008-06-01

    The radial stress profile in a cylindrical die during compaction of titanium (Ti) powder was investigated by experiments. The concept of an instrumented die was extended to design an enhanced instrumented die. Custom-made strain gage pins were used to measure the radial stress during powder compaction. The test fixture was designed to simulate double-action pressing. The measured die stress profile for Ti powder was compared with that for a commercially available iron (Fe) powder. The stress history shows that an appreciable residual stress remains in the die in the radial direction after the axial compaction stress is removed from the powder. Furthermore, the radial stress profile in the die, while under maximum axial compaction stress, is more uniform across the height of the Fe compact than that of the Ti compact. In addition, the residual stress profile in the die in the radial direction reduces symmetrically in both directions beyond the height of the compact for both powders. Finally, the Ti powder shows a significantly higher frictional coefficient at the maximum axial compaction stress, and consequently a higher maximum axial ejection stress than the Fe powder.

  20. Analysis of tablet compaction. I. Characterization of mechanical behavior of powder and powder/tooling friction.

    PubMed

    Cunningham, J C; Sinka, I C; Zavaliangos, A

    2004-08-01

    In this first of two articles on the modeling of tablet compaction, the experimental inputs related to the constitutive model of the powder and the powder/tooling friction are determined. The continuum-based analysis of tableting makes use of an elasto-plastic model, which incorporates the elements of yield, plastic flow potential, and hardening, to describe the mechanical behavior of microcrystalline cellulose over the range of densities experienced during tableting. Specifically, a modified Drucker-Prager/cap plasticity model, which includes material parameters such as cohesion, internal friction, and hydrostatic yield pressure that evolve with the internal state variable relative density, was applied. Linear elasticity is assumed with the elastic parameters, Young's modulus, and Poisson's ratio dependent on the relative density. The calibration techniques were developed based on a series of simple mechanical tests including diametrical compression, simple compression, and die compaction using an instrumented die. The friction behavior is measured using an instrumented die and the experimental data are analyzed using the method of differential slices. The constitutive model and frictional properties are essential experimental inputs to the finite element-based model described in the companion article. PMID:15236452

  1. Kinetic Analysis of Solid-State Formation of Mg2Si by Powder Metallurgy Process

    NASA Astrophysics Data System (ADS)

    Sun, Bin; Li, Shufeng; Imai, Hisashi; Umeda, Junko; Kondoh, Katsuyoshi

    The synthesis kinetics of Mg2Si intermetallic compounds (IMC) from the elemental mixture of Mg-Si powders was studied by using differential thermal analysis (DTA). The exothermic peaks were at 818 K, which indicated the synthesis reaction of 2Mg+Si → Mg2Si. The synthesis kinetics of Mg2Si was evaluated by the Ozawa method and KAS method. The activation energy of Mg2Si was calculated as 376.0 kJ/mol by using the data from DTA curves. The bulky materials of Mg-Mg2Si composite were prepared through solid-state reaction by using SPS consolidation process. From the results of XRD and SEM-EDS analysis, it was known that Mg and Si powders never react completely at low temperatures of 813 K and 833 K, and the suitable temperature of solid-state synthesis by SPS should be about 853 K.

  2. Development of superalloys by powder metallurgy for use at 1000 - 1400 F

    NASA Technical Reports Server (NTRS)

    Calhoun, C. D.

    1971-01-01

    Consolidated powders of four nickel-base superalloys were studied for potential application as compressor and turbine discs in jet engines. All of the alloys were based on the Rene' 95 chemistry. Three of these had variations in carbon and A12O3 contents, and the fourth alloy was chemically modified to a higher volume fraction. The A12O3 was added by preoxidation of the powders prior to extrusion. Various levels of four experimental factors (1) alloy composition, (2) grain size, (3) thermomechanical processing, and (4) room temperature deformation plus final age were evaluated by tensile and stress rupture testing at 1200 F. Various levels of the four factors were assumed in order to construct the statistically-designed experiment, but the actual levels investigated were established in preliminary studies that preceded the statistical process development study.

  3. Development of Rare-Earth Free Mn-Al Permanent Magnet Employing Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Singh, N.; Shyam, R.; Upadhyay, N. K.; Dhar, A.

    2015-02-01

    Most widely used high-performance permanent magnets are currently based on intermetallics of rare-earths in combination with Fe and Co. Rare-earth elements required for these magnets are getting expensive by the day. Consequently, there is a thrust worldwide to develop economical rare-earth free permanent magnets. It is acknowledged that the phase in Mn-Al alloys possesses magnetic properties without the presence of ferromagnetic elements such as Fe, Co, and Ni. In the present study, we report the synthesis of magnetic phase of Mn54Al46 alloy synthesized using mechanical alloying followed by solutionizing and annealing to obtain the desired magnetic phase. It is well known that Al dissolves partially in Mn matrix hence supersaturated solid solution of Mn54Al46 alloy powder was obtained by mechanical alloying using a planetary high-energy ball mill. For this purpose elemental Mn and Al powders were ball-milled in Argon atmosphere at 400 rpm using stainless steel bowl with ball to powder ratio of 15:1. These mechanically alloyed Mn54Al46 powders were then consolidated using spark plasma sintering at 550°C for 20 min. followed by solution treatment at 1050°C for 5 hrs and then water quenched to retain high temperature phase. Subsequently, the Mn54Al46 samples were annealed in the temperature range 450°C-650°C to obtain the magnetic phase. These samples were characterized by XRD and SEM and the magnetic properties were measured using a vibrating sample magnetometer (VSM). It was observed that the magnetization and coercivity of MnAl magnets exhibited strong dependence on annealing temperature and annealing time.

  4. Niobium-titanium superconductors produced by powder metallurgy having artificial flux pinning centers

    SciTech Connect

    Jablonski, P.D.; Larbalestier, D.C.

    1993-07-13

    A superconducting wire structure is described comprising: a matrix comprising body centered cubic niobium-titanium alloy with a second phase of discrete metal inclusions compatible with niobium-titanium providing artificial pinning centers distributed therein, at least some second phase inclusions having sizes in the range of 1 to 10 nm, the second phase comprising between 5 to 50% by volume of the total matrix and second phase, wherein the second phase is selected from the group consisting of niobium, vanadium, tantalum, hafnium, zirconium, titanium, tungsten, molybdenum, chromium, copper, silver, gold and alloys thereof, and wherein the wire structure is formed by deforming and drawing a billet comprising a mixture of a first phase powder comprising the body centered cubic niobium-titanium alloy with a second phase powder of the metal compatible with niobium-titanium, the second phase comprising from 5% to 50% by volume of the mixture, the mixture pressed and sintered to provide a bond between the powder particles without significant diffusion of the second phase into the first phase or significant diffusion of the first phase into the second phase.

  5. Toughness enhancement of powder metallurgy zirconium containing aluminum-lithium alloys through degassing

    SciTech Connect

    LaSalle, J.C.; Raybould, D.; Das, S.K.; Limoncelli, E.V.

    1993-07-06

    In a method for producing a consolidated article from a rapidly solidified, zirconium containing aluminum lithium alloy powder, the improvement is described comprising the step of: degassing said powder in a vacuum at a temperature of at least about 450 C, said powder consisting essentially of the formula Al[sub bal]Li[sub a]Cu[sub b]Mg[sub c]Zr[sub d], where a' ranges from about 2.4 to 2.8 wt%, b' ranges from about 0.5 to 2.0 wt%, c' ranges from 0.2 to 2.0 wt% and d' ranges from greater than about 0.8 to 1.0 wt%, the balance being aluminum and said article having an ultimate tensile strength ranging from 75 to 80 ksi, a tensile elongation ranging from about 5 to 8% and a T-L notched impact toughness ranging from about 100 to 150 in-lb/in[sup 2].

  6. The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; Shank, J. M.; Shiveley, A. R.; Saurber, W. M.; Gaussa, E. F.; Pilchak, A. L.

    2014-12-01

    The effect of subsolvus forging temperature and strain rate on the grain size developed during final supersolvus heat treatment (SSHT) of two powder-metallurgy, gamma-gamma prime superalloys, IN-100 and LSHR, was established. For this purpose, isothermal, hot compression tests were performed at temperatures ranging from 1144 K (871 °C) and 22 K (22 °C) below the respective gamma-prime solvus temperatures ( T γ') and strain rates between 0.0003 and 10 s-1. Deformed samples were then heat treated 20 K (20 °C) above the solvus for 1 h with selected additional samples exposed for shorter and longer times. For both alloys, the grain size developed during SSHT was in the range of 15 to 30 μm, except for those processing conditions consisting of pre-deformation at the highest temperature, i.e., T γ'—22 K ( T γ'—22 °C), and strain rates in the range of ~0.001 to 0.1 s-1. In these latter instances, the heat-treated grain size was approx. four times as large. The observations were interpreted in terms of the mechanisms of deformation during hot working and their effect on the driving forces for grain-boundary migration which controls the evolution of the gamma-grain size.

  7. Closure-affected fatigue crack propagation behaviors of powder metallurgy-processed Al-Li alloys in various environments

    SciTech Connect

    Kim, S.S.; Shin, K.S.

    1999-08-01

    The environment-affected fatigue crack propagation (FCP) behavior of rapid solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (RSP 644-B) and mechanically alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.8O{sub 2} (MA 905-XL) were examined in air, in vacuum, and in an aqueous 3.5 pct NaCl solution at R = 0.1 and a sinusoidal frequency of 20 Hz. The emphasis was placed on the effect of environment-sensitive crack closure on the FCP behavior of the fine-grain-sized powder metallurgy (P/M)-processed Al-Li alloys. The present study suggests that closure is extremely sensitive to environmental factors and significantly alters the environment-affected da/dN-{Delta}K relationships for both alloys. In the submicron grain-sized MA 905-XL, for example, increased corrosion product-induced closure in aqueous NaCl appeared to overwhelm the detrimental environmental effects in low- and intermediate-{Delta}K regimes. The environment-sensitive closure contribution alone, however, cannot completely explain the FCP behavior of P/M-processed Al-Li alloys. The intrinsic environmental effects also need to be considered for further understanding of this behavior.

  8. Processing, characterization, and in vitro/in vivo evaluations of powder metallurgy processed Ti-13Nb-13Zr alloys.

    PubMed

    Bottino, Marco C; Coelho, Paulo G; Henriques, Vinicius A R; Higa, Olga Z; Bressiani, Ana H A; Bressiani, José C

    2009-03-01

    This article presents details of processing, characterization and in vitro as well as in vivo evaluations of powder metallurgy processed Ti-13Nb-13Zr samples with different levels of porosity. Sintered samples were characterized for density, crystalline phases (XRD), and microstructure (SEM and EDX). Samples sintered at 1000 degrees C showed the highest porosity level ( approximately 30%), featuring open and interconnected pores ranging from 50 to 100 mum in diameter but incomplete densification. In contrast, samples sintered at 1300 and 1500 degrees C demonstrated high densification with 10% porosity level distributed in a homogeneous microstructure. The different sintering conditions used in this study demonstrated a coherent trend that is increase in temperature lead to higher sample densification, even though densification represents a drawback for bone ingrowth. Cytotoxicity tests did not reveal any toxic effects of the starting and processed materials on surviving cell percentage. After an 8-week healing period in rabbit tibias, the implants were retrieved, processed for nondecalcified histological evaluation, and then assessed by backscattered electron images (BSEI-SEM) and EDX. Bone growth into the microstructure was observed only in samples sintered at 1000 degrees C. Overall, a close relation between newly formed bone and all processed samples was observed. PMID:18335528

  9. Modeling the Constitutive Relationship of Powder Metallurgy Ti-47Al-2Nb-2Cr Alloy During Hot Deformation

    NASA Astrophysics Data System (ADS)

    Sun, Yu; Hu, Lianxi; Ren, Junshuai

    2015-03-01

    In the present work, the isothermal compression tests of PM alloy Ti-47Al-2Nb-2Cr were carried out in the temperature range of 950-1200 °C. A Gleeble 1500D thermosimulation machine was used, and samples were tested at strain rates ranging from 10-3 to 10-1 s-1. Based on the obtained flow stress curves, the hot deformation behavior was presented. The constitutive relationship of powder metallurgy (PM) Ti-47Al-2Nb-2Cr alloy was developed using an Arrhenius-type constitutive model that involves strain compensation in addition to an artificial neural network model. The accuracy and reliability of the developed models were quantified in terms of statistical parameters such as correlation coefficient and absolute value of relative error. It was found that deformation temperature and strain rate have obvious effects on the flow characteristics, and the flow stress increases with the increasing strain rate and the decreasing temperature. Moreover, the proposed models possess excellent prediction capability of flow stresses for the present alloy during hot deformation. Compared with the traditional Arrhenius-type model, the backpropagation neural network model is more accurate when presenting the isothermal compressing deformation behavior at elevated temperatures for PM Ti-47Al-2Nb-2Cr alloy.

  10. Investigation of thin layers deposited by two PVD techniques on high speed steel produced by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Jakubczyov, D.; Hvizdo, P.; Seleck, M.

    2012-04-01

    This study was intended to investigate the properties and cutting performance with thin layers applied by two PVD techniques. PVD techniques ARC and LARC were used for the deposition of thin coatings onto cutting tools prepared by powder metallurgy. Advanced types of layers - monolayer AlTiCrN and nanocomposite type of nc-AlTiN/Si3N4 layer - were analyzed by standard techniques for surface status and quality assessment - roughness, hardness, layer thickness, chemical composition by GDOES, tribological properties at room and elevated temperature. Durability testing of the cutting tools was carried out according to the standard ISO 3685-1999. The nanocomposite nc-AlTiN/Si3N4 layer achieved lower roughness when compared to monolayer AlTiCrN which leads to the achievement of higher hardness and better layer quality. The HV0.5 hardness values were ?26 GPa. The results showed a 2-3-times longer durability of the cutting tools in comparison with equivalent uncoated PM and traditional materials. The deposited coatings contributed to the improvement of their durability.

  11. Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Harrell, Tammy J.; Topping, Troy D.; Wen, Haiming; Hu, Tao; Schoenung, Julie M.; Lavernia, Enrique J.

    2014-12-01

    Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure ( e.g., 100's nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 μm apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

  12. Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Harrell, Tammy J.; Topping, Troy D.; Wen, Haiming; Hu, Tao; Schoenung, Julie M.; Lavernia, Enrique J.

    2014-09-01

    Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 μm apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

  13. Microstructure and Strengthening Mechanisms in an Ultrafine Grained Al-Mg-Sc Alloy Produced by Powder Metallurgy

    SciTech Connect

    Tammy J. Harrell; Troy D. Topping; Haiming Wen; Tao Hu; JULIE M. SCHOENUNG; ENRIQUE J. LAVERNIA

    2014-12-01

    Additions of Sc to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc significantly increases the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultrafine-grained (UFG) microstructure (e.g., 100’s nm). Accordingly, we investigated the microstructural evolution and mechanical behavior of a cryomilled ultrafine grained Al-5Mg-0.4Sc (wt pct) and compared the results to those of an equivalent fine-grained material (FG) produced by powder metallurgy. Experimental materials were consolidated by hot isostatic pressing (HIP’ing) followed by extrusion or dual mode dynamic forging. Under identical processing conditions, UFG materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 to 3 µm apart, while precipitates in the FG materials have a diameter of 24 nm and are spaced 50 to 200 nm apart. The strengthening mechanisms are calculated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are Mg-O/N dispersion strengthening and precipitate strengthening, respectively.

  14. An Investigation of High-Temperature Precipitation in Powder-Metallurgy, Gamma/Gamma-Prime Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; Kim, S.-L.; Zhang, F.; Tiley, J. S.

    2015-04-01

    The high-temperature-precipitation behavior of a typical powder-metallurgy, gamma-gamma-prime, nickel-base superalloy (LSHR) was determined and used to develop and validate a quantitative fast-acting model. To this end, a series of experiments comprising supersolvus solution treatment followed by continuous cooling at rates typical of those experienced during the manufacture of full-scale components was conducted for LSHR. The nucleation and growth of secondary-gamma-prime precipitates were deduced via metallography on samples water quenched at various temperatures during the cooling cycle. Further insight on nucleation and the extent of retained supersaturation during cooling was obtained from in situ synchrotron (X-ray diffraction) experiments involving cooling of LSHR samples at identical rates with or without a hold time at an intermediate temperature. The observations were interpreted using a fast-acting (spreadsheet) model which incorporated the important aspects of classical, homogeneous-nucleation theory and growth by bulk diffusion. In this regard, particular attention was paid to the determination of model input parameters such as the composition, free energy of formation, and surface energy of precipitates, and an effective diffusivity; the values so determined contrasted with those from existing thermodynamic and diffusion databases. It was demonstrated that fast-acting-model calculations based on a nickel-chromium pseudo-binary system gave good agreement with measurements of the evolution of precipitate volume fraction, number density, and size during continuous cooling.

  15. Tungsten and tungsten-alloy powder metallurgy. (Latest citations from the NTIS data base). Published Search

    SciTech Connect

    Not Available

    1992-10-01

    The bibliography contains citations concerning the processing and fabrication of tungsten, tungsten alloys, and tungsten composites. Compacting, pressing, sintering, extruding, and rolling are among the methods described. Infiltration of porous tungsten shapes is included, as well as mechanical properties, thermal properties, and microstructure of end products. Applications include rocket nozzles, nuclear reactor materials, and porous ionizers. (Contains a minimum of 116 citations and includes a subject term index and title list.)

  16. Technological Aspects of High Speed Direct Laser Deposition Based on Heterophase Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Turichin, G. A.; Klimova, O. G.; Zemlyakov, E. V.; Babkin, K. D.; Kolodyazhnyy, D. Yu.; Shamray, F. A.; Travyanov, A. Ya.; Petrovskiy, P. V.

    The article deals with physical peculiarities and technology of high speed processes of direct laser deposition. On the base of theoretic research and computer modeling the powder transfer has been optimized, increasing process stability and productivity. Principles of nozzles design also have been developed in accordance with technological needs. An influence of process mode on product properties and material structure was defined for heat resisted Ni-based superalloys. Developed technology provided the mechanic properties of products on the level of rolled material and allows avoid heat treatment and HIP in production process. Possible ways for increasing process performance and economic efficiency also have been discussed.

  17. Effect of reduced cobalt contents on hot isostatically pressed powder metallurgy U-700 alloys

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1982-01-01

    The effect of reducing the cobalt content of prealloyed powders of UDIMET 700 (U-700) alloys to 12.7, 8.6, 4.3, and 0% was examined. The powders were hot isostatically pressed into billets, which were given heat treatments appropriate for turbine disks, namely partial solutioning at temperatures below the gamma prime solvus and four step aging treatments. Chemical analyses, metallographic examinations, and X-ray diffraction measurements were performed on the materials. Minor effects on gamma prime content and on room temperature and 650 C tensile properties were observed. Creep rupture lives at 650 C reached a maximum at the 8.4% concentration, while at 760 C a maximum in life was reached at the 4.3% cobalt level. Minimum creep rates increased with decreasing cobalt content at both test temperatures. Extended exposures at 760 and 815 C resulted in decreased tensile strengths and rupture lives for all alloys. Evidence of sigma phase formation was also found.

  18. Dynamic compaction of Ni and Al micron powder blends in cylindrical recovery scheme

    NASA Astrophysics Data System (ADS)

    Ananev, S. Yu; Deribas, A. A.; Drozdov, A. A.; Dolgoborodov, A. Yu; Morozov, A. E.; Povarova, K. B.; Yankovsky, B. D.

    2015-11-01

    The experiments on explosive compaction of Ni and Al micron powders mixtures in cylindrical recovery assemblies are reported. Synthesized NiAl compacts were characterized by optical microscopy and x-ray diffraction. The found porosity of the compacts was decreasing with dynamic pressure growth. The geometry of dendrite NiAl grains was associated with the dynamics of pressure waves inside the assembly.

  19. Mechanical behavior of saturated, consolidated, alumina powder compacts

    NASA Astrophysics Data System (ADS)

    Franks, George Vincent, Jr.

    Alumina slurries were prepared with three differing particle pair potentials produced by adjusting pH and salt concentration. The three pair potentials investigated were repulsive, strongly attractive and weakly attractive. Bodies were consolidated by pressure filtration, at applied pressures between 0.25 MPa and 150 MPa. The mechanical properties of these bodies were investigated by uniaxial compressive loading. High consolidation pressures lead to high forces at particle contacts which can push the particles together to form a strong touching network even when the particles are separated by a potential barrier in the slurry state. When particles are pushed into adhesive contact, the saturated, consolidated powder compacts are brittle. When a short ranged repulsive interparticle potential persists after consolidation, the specimens are plastic. Saturated bodies formed from strongly attractive slurries (flocculated at the isoelectric point pH 9) were plastic at low relative densities but were brittle at higher relative densities. Bodies formed from the repulsive slurries (dispersed at pH 4) were always brittle. Bodies consolidated from weakly attractive slurries (coagulated at pH 4, 5, 6, or 12 with additions of salt) were plastic at low consolidation pressures but became brittle at high consolidation pressures. This plastic-to-brittle transition depends on the shape of the pair potential, the size and morphology of the powder. The plastic specimens had stress-strain behavior characterized by a peak stress, followed by a lower flow stress. The peak stress reduced to the flow stress upon several reloading cycles. The effect of the slope of the repulsive potential barrier on the plastic-to-brittle transition was investigated. Alumina slurries coagulated at pH 12 with 0.5 M of Lisp+, Cssp+ and tetraethylammoniumsp+ chlorides were consolidated by pressure filtration. Consolidation pressures required to push particles together were greater for smaller counterions. The effect of particle size and morphology on the consolidation behavior and the plastic-to-brittle transition of saturated alumina powder compacts was investigated. Large particles pack to higher relative densities than small particles. Blocky particles pack to lower relative densities than particles with rounded surfaces. Consolidated bodies of large particles become brittle at lower consolidation pressures. The effects of pair potential, particle size and strain rate on the flow stress was also investigated. Bodies consolidated from slurries of particles that reside in attractive minima have flow stresses and relaxed (yield) stresses that increase with the depth of the attractive minima. Bodies consolidated from slurries of larger particles possess lower flow stresses than bodies made of small particles. Flow stress for certain bodies formed from the coagulated slurry had a nearly identical flow stress as measured for a commercial, throwing clay. The strain rate sensitivity is greater for bodies that have relative densities approaching the maximum. (Abstract shortened by UMI.)

  20. Chloride-induced stress corrosion cracking of powder metallurgy duplex stainless steels

    SciTech Connect

    Laitinen, A.; Haenninen, H.

    1996-04-01

    The chloride-induced stress corrosion cracking (SCC) resistance of nitrogen-alloyed, powder metallurgically (P/M) produced and hot isostatically pressed (HIP) duplex stainless steels (DSS) was investigated and compared to the SCC resistance of two commercial wrought (forged) DSS. Constant-strain (deflection) SCC tests with four-point, loaded-bend specimens were performed in aerated 50 wt% calcium chloride solution at 100 C with pH = 6.5 to 7.0. The pitting corrosion resistance index value (PREN) was not a suitable parameter to predict SCC resistance of the investigated DSS. Instead of pitting corrosion, selective corrosion of the austenite or ferrite phases seemed to determine the SCC resistance of each material. Selective corrosion was not the primary cause for failure, but it assisted the initiation and growth of stress corrosion cracks. Selective corrosion was noticed in all of the investigated DSS. The corroding phase, austenite or ferrite, was dependent on the material. High copper content in the specific material slightly lowered the stress limit at which stress corrosion cracks started to grow in the used test solution. The SCC resistance of P/M-HIP DSS was as good as the SCC resistance of forged DSS. The banded microstructure of forged DSS led to a directional selective corrosion attack. The corrosion grooves were ideal sites for initiation of SCC. Because of this phenomenon, the homogeneous microstructure of P/M-HIP DSS showed clear advantages over the banded microstructure of forged DSS.

  1. The properties of aluminum alloys containing nickel, produced using powder metallurgy method

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Jamaludin Shamsul, B.; Ahmad, Khairel R.; Hussein, Wan M. H.

    2015-05-01

    In this paper, the effects of nickel on the microstructure and mechanical properties of experimental an Al-Zn-Mg-Cu PM alloys under the impacts of the retrogression and re-aging treatment was investigated. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered samples subjected to the homogenizing condition at 470°C for 1.5 hours then aging at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Characterization's results indicate that the microstructures of an Al-Zn-Mg-Cu-Ni PM alloys presented an intermetallics compound in the aluminum's matrix, identified as the AlNi and Al3Ni2 phases besides the MgZn and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloys.

  2. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    NASA Technical Reports Server (NTRS)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  3. Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

    2012-01-01

    Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a transgranular initiation typical to that observed in unexposed specimens.

  4. Characterization of Plastic Flow Pertinent to the Evolution of Bulk Residual Stress in Powder-Metallurgy, Nickel-Base Superalloys

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; Fagin, P. N.; Goetz, R. L.; Furrer, D. U.; Dutton, R. E.

    2015-09-01

    The plastic-flow behavior which controls the formation of bulk residual stresses during final heat treatment of powder-metallurgy (PM), nickel-base superalloys was quantified using conventional (isothermal) stress-relaxation (SR) tests and a novel approach which simulates concurrent temperature and strain transients during cooling following solution treatment. The concurrent cooling/straining test involves characterization of the thermal compliance of the test sample. In turn, this information is used to program the ram-displacement- vs-time profile to impose a constant plastic strain rate during cooling. To demonstrate the efficacy of the new approach, SR tests (in both tension and compression) and concurrent cooling/tension-straining experiments were performed on two PM superalloys, LSHR and IN-100. The isothermal SR experiments were conducted at a series of temperatures between 1144 K and 1436 K (871 °C and 1163 °C) on samples that had been supersolvus solution treated and cooled slowly or rapidly to produce starting microstructures comprising coarse gamma grains and coarse or fine secondary gamma-prime precipitates, respectively. The concurrent cooling/straining tests comprised supersolvus solution treatment and various combinations of subsequent cooling rate and plastic strain rate. Comparison of flow-stress data from the SR and concurrent cooling/straining tests showed some similarities and some differences which were explained in the context of the size of the gamma-prime precipitates and the evolution of dislocation substructure. The magnitude of the effect of concurrent deformation during cooling on gamma-prime precipitation was also quantified experimentally and theoretically.

  5. A discrete finite element modelling and measurements for powder compaction

    NASA Astrophysics Data System (ADS)

    Choi, J. L.; Gethin, D. T.

    2009-04-01

    An experimental investigation into friction between powder and a target surface together with numerical modelling of compaction and friction processes at a micro-scale are presented in this paper. The experimental work explores friction mechanisms by using an extended sliding plate apparatus operating at low load while sliding over a long distance. Tests were conducted for copper and 316 steel with variation in loads, surface finish and its orientation. The behaviours of the static and dynamic friction were identified highlighting the important influence of particle size, particle shape, material response and surface topography. The results also highlighted that under light loading the friction coefficient remains at a level lower than that derived from experiments on equipment having a wider dynamic range and this is attributed to the enhanced sensitivity of the measurement equipment. The results also suggest that friction variation with sliding distance is a consequence of damage, rather than presentation of an uncontaminated target sliding surface. The complete experimental cycle was modelled numerically using a combined discrete and finite element scheme enabling exploration of mechanisms that are defined at the particle level. Using compaction as the starting point, a number of simulation factors and process parameters were investigated. Comparisons were made with previously published work, showing reasonable agreement and the simulations were then used to explore the process response to the range of particle scale factors. Models comprising regular packing of round particles exhibited stiff response with high initial density. Models with random packing were explored and were found to reflect trends that are more closely aligned with experimental observation, including rearrangement, followed by compaction under a regime of elastic then plastic deformation. Numerical modelling of the compaction stage was extended to account for the shearing stage of the extended sliding plate experiment. This allowed micro-scale simulations of the friction mechanisms seen within the experimental programme. The frictional response with similar stress level in the normal direction as reported for the experiment was first emulated and explored and qualitative agreement was achieved showing a similar pattern. The factors identified from the experiments were investigated on smooth and rough surfaces highlighting each effect. It was confirmed that the rough surface clearly leads to higher friction coefficient since it accounts for both plain friction and topographical effects and the average stress distribution increased against the restraining die wall when the rough surface was introduced for the model with round regular packing of particles. Random packed models again showed a better reflection of the experimental conditions. A wider distribution of stress was observed because of the further rearrangements. Interlocking was observed for the models with irregularly shaped particles on a rough surface, which led to an increase in normal stress on the top punch. This would lead to dilation in the case where a punch was force level controlled as for the experiment.

  6. Mechanical properties and fracture mechanism of Ni[sub 3]Al intermetallic produced by powder metallurgy and standard melting and casting processes

    SciTech Connect

    Jovanovic, M.; Bozic, D.; Ilic, N.; Mitkov, M. ); Drobnjak, D. . Faculty of Technology)

    1994-03-01

    The room and high-temperature compression strength and ductility, microstructure, and fracture mechanism of Ni[sub 3]Al base intermetallic doped with boron have been investigated. Ni[sub 3]Al was produced by powder metallurgy (gas atomization and hot pressing), and vacuum melting and casting process. The strength of the material exhibits a positive temperature dependence with a maximum at approximately 700 C and then begins to decrease. The ductility remains practically unchanged up to 700 C and then increases significantly as the temperature increases. The ductility of Ni[sub 3]Al cannot be correlated with fracture mechanism.

  7. Finite Element Modeling on the Compaction of Copper Powder Under Different Conditions

    NASA Astrophysics Data System (ADS)

    An, Xizhong; Zhang, Yilei; Zhang, Yuxi; Yang, Shuo

    2015-08-01

    Single-action die compaction of copper powders with initial loose natural packing and vibrated random dense packing structures was carried out numerically by finite element method and physically for validation. Furthermore, the compaction under various cyclic loadings was modeled to identify its effects on the compact properties. The results were analyzed and compared between compacts formed at different initial packing structures and different forming conditions, which indicate that at the same pressure, single-action die compaction on the dense uniform initial packing can produce compacts with high relative density, uniform density and stress distributions, which implies the necessity to improve initial packing density and uniformity in forming high performance compacts. Meanwhile, by using cyclic loading on such dense initial packing structures, compacts with higher packing density and more uniform density and stress distributions can be created. The numerical and physical results are comparable and in good agreement with the proposed double logarithmic equation.

  8. High strain rate superplasticity of a powder metallurgy SiC particulate reinforced 6061 Al composite (6061/SiC/17. 5p)

    SciTech Connect

    Nieh, T.G.; Wadsworth, J. ); Imai, T. ); Kojima, S. )

    1994-12-15

    One of the major drawbacks of conventional superplastic forming is that the phenomenon is only found at relatively low strain rates, typically about 10[sup [minus]4] to 10[sup [minus]3] s[sup [minus]1]. Recent studies have demonstrated that superlasticity can exist at considerably higher strain rates than 10[sup [minus]3] s[sup [minus]1]. This high-strain-rate superplasticity (HSRS) phenomenon has now been observed principally in metal matrix composites and mechanically alloyed materials, but it has also been observed in more conventionally produced metallic alloys. Metal matrix composites can be fabricated by various techniques, e.g., squeeze casting, vortex methods, compocasting, powder metallurgical (PM) methods, and spray deposition. However, metal matrix composites that show HSRS are fabricated primarily by PM methods. Recently, Hikosaka et al. demonstrated that an ingot metallurgy (IM) 20 vol% SiC[sub p]-reinforced 6061 Al can also exhibit the HSRS phenomenon. The purpose of this study is to investigate the HSRS behavior of a SiC particulate-reinforced 6061 Al prepared by a powder metallurgy method and to compared its behavior with that of the composites produced by IM methods. The effect of thermomechanical processing and testing temperature will be discussed.

  9. Characterization by X-ray tomography of granulated alumina powder during in situ die compaction

    SciTech Connect

    Cottrino, Sandrine; Jorand, Yves Maire, Eric; Adrien, Jérôme

    2013-07-15

    Compaction process, the aim of which being to obtain green bodies with low porosity and small size, is often used before sintering treatment. Prior to die filling, the ceramic powder is generally granulated to improve flowability. However during compaction, density heterogeneity and critical size defects may appear due to intergranule and granule-die wall frictions. In this work, the influence of granule formulation on the compact morphology has been studied. To do so, a compaction setup was installed inside an X-ray tomography equipment so that the evolution of the compact morphology could be analysed during the whole compaction process. We have demonstrated that high humidity rate and the addition of binder in the granule formulation increase density heterogeneity and generate larger defects. - Highlights: • An original compaction set up was installed inside an X-Ray tomography equipment. • The compaction process of granulated ceramic powder is imaged. • The compact green microstructure is quantified and related to the compaction stages. • The most detrimental defects of dry-pressed parts are caused by hollow granules. • Formulations without binder allow a reduction of the number of large defects.

  10. Cold Compaction of Copper Powders Under Mechanical Vibration and Uniaxial Compression

    NASA Astrophysics Data System (ADS)

    An, Xizhong; Xing, Zhitao; Jia, Chengchang

    2014-04-01

    Physical experiments were carried out to study the cold compaction of copper powders under uniaxial compression using our self-designed equipment. Two kinds of copper powders with different particle sizes and distributions were considered. One-dimensional vibrations were utilized before compaction to systematically study the effect of parameters such as vibration frequency ω, amplitude A, and vibration intensity Г on the initial packing density. The macro-property and corresponding microstructures of compacts obtained from initial packings with and without vibrations were compared and analyzed. The results show that higher packing density can be obtained in the compaction of coarse powders with broad size distribution when other experimental conditions are fixed. For each powder, the evolution of packing density vs pressure takes on exponential correlation with high R 2 value. Much denser and more uniform compacts can be realized with the aid of vibration which can improve the particle rearrangement and result in the filling of macro pores formed in initial packing, and the characterization on the microstructure identifies that the particles inside the compact become polyhedrons with regular shape and uniformly distributed.

  11. Nanostructured bulk MnBi magnets fabricated by hot compaction of cryomilled powders

    NASA Astrophysics Data System (ADS)

    Rama Rao, N. V.; Gabay, A. M.; Li, W. F.; Hadjipanayis, G. C.

    2013-07-01

    Cryomilling was employed for Mn50+xBi50-x (x = 0,5) alloys to synthesize nanocrystalline powders with particle size of 400-500 nm without much increase of the unwanted secondary Bi phase. At room temperature, the cryomilled powders showed large coercivity (Hc) values of 18.5 kOe and 20.7 kOe for Mn50Bi50 and Mn55Bi45, respectively. Cryomilled powders were hot compacted to form a bulk nanostructured MnBi magnet. The Mn50Bi50 hot compacted magnet exhibits Hc of 12.9 kOe with remanence value of 26 emu g-1 at room temperature. The microstructure of hot compacted magnet illustrates uniform grains with an average size of 40 nm. Furthermore, the magnet shows a large positive temperature coefficient of Hc which reaches a value of more than 30 kOe above 450 K.

  12. Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure

    NASA Astrophysics Data System (ADS)

    Rojek, Jerzy; Nosewicz, Szymon; Jurczak, Kamila; Chmielewski, Marcin; Bochenek, Kamil; Pietrzak, Katarzyna

    2015-12-01

    This paper presents numerical studies of powder compaction in cold uniaxial pressing. The powder compaction in this work is considered as an initial stage of a hot pressing process so it is realized with relatively low pressure (up to 50 MPa). Hence the attention has been focused on the densification mechanisms at this range of pressure and models suitable for these conditions. The discrete element method employing spherical particles has been used in the numerical studies. Numerical simulations have been performed for two different contact modelsthe elastic Hertz-Mindlin-Deresiewicz model and the plastic Storkers model. Numerical results have been compared with the results of laboratory tests of the die compaction of the NiAl powder. Comparisons have shown that the discrete element method is capable to represent properly the densification mechanisms by the particle rearrangement and particle deformation.

  13. Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, P. J.; Lederich, R. J.; Oneal, J. E.; Pao, P. S.

    1985-01-01

    The effects of alloy chemistry and particulate morphology on consolidation behavior and consolidated product properties in rapid solidification processed, powder-metallurgical Al-3Li-1.5Cu-1Mg-0.5Co-0.2Zr and Al-4.4Cu-1.5Mg-Fe-Ni-0.2Zr extrusions and forgings were studied. Microstructures and mechanical properties of both alloys are largely unaffected by particulate production method (vacuum atomization, ultrasonic atomization, or twin-roller quenching) and by particulate solidification rates between 1000 and 100,000 K/s. Consolidation processing by canning, cold compaction, degassing, and hot extrusion is sufficient to yield mechanical properties in the non-Li-containing alloy extrusions which are similar to those of 7075-Al, but ductilities and fracture toughnesses are inferior owing to poor interparticle bonding caused by lack of a vacuum-hot-pressing step during consolidation. Mechanical properties of extrusions are superior to those of forgings owing to the stronger textures produced by the more severe hot working during extrusion. The effects on mechanical properties of dispersoid size and volume fraction, substructural refinement, solid solution strengthening by Mg, and precipitate size and distribution are elucidated for both alloy types.

  14. Surface Area, and Oxidation Effects on Nitridation Kinetics of Silicon Powder Compacts

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Palczer, A. R.

    1998-01-01

    Commercially available silicon powders were wet-attrition-milled from 2 to 48 hr to achieve surface areas (SA's) ranging from 1.3 to 70 sq m/g. The surface area effects on the nitridation kinetics of silicon powder compacts were determined at 1250 or 1350 C for 4 hr. In addition, the influence of nitridation environment, and preoxidation on nitridation kinetics of a silicon powder of high surface area (approximately equals 63 sq m/g) was investigated. As the surface area increased, so did the percentage nitridation after 4 hr in N2 at 1250 or 1350 C. Silicon powders of high surface area (greater than 40 sq m/g) can be nitrided to greater than 70% at 1250 C in 4 hr. The nitridation kinetics of the high-surface-area powder compacts were significantly delayed by preoxidation treatment. Conversely, the nitridation environment had no significant influence on the nitridation kinetics of the same powder. Impurities present in the starting powder, and those accumulated during attrition milling, appeared to react with the silica layer on the surface of silicon particles to form a molten silicate layer, which provided a path for rapid diffusion of nitrogen and enhanced the nitridation kinetics of high surface area silicon powder.

  15. Experiments and modelling of dynamic powder compaction in the scope of deflagration to detonation transition studies

    NASA Astrophysics Data System (ADS)

    Bodard, Sebastien; Lapebie, Emmanuel; Saurel, Richard; Daniel, Eric; Tosello, Robert; Lafontaine, Eric

    2015-06-01

    Understanding DDT in granular media is of prime interest for ammunition safety. However, the mechanisms involved are multiphasic, granular and multi-scale. To progress in DDT understanding it is thus necessary to focus on some mechanisms. As compaction plays a prominent role in DDT it is important to accurately model this phenomenon. In this communication, dynamic compaction of inert powder is studied to focus on the mechanical effects taking place in early stages of DDT. Both experimental and modelling aspects are considered. A novel experimental setup is designed to generate a dynamic 1D compaction. It consists in a container filled with powder and closed by a piston. A projectile launched with a gas gun impacts the piston rod to compress the powder. High-speed cameras with grain-scale resolution record the test. The velocity field is determined with image correlation. A multiphase compaction model (Saurel et al., 2010) has been implemented. Granular effects are taken into account with a granular equation of state, determined by quasi-static compaction. With additional features such as wall friction, good agreement between experiments and computations is found. The experimental apparatus is then used to study reactive powders. This work is supported by DGA.

  16. Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder

    SciTech Connect

    Jonsen, P.; Haeggblad, H.-A.

    2007-05-17

    In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and uniform density. High velocity compaction (HVC) using a hydraulic operated hammer is a production method to form powder utilizing a shock wave. Pre-alloyed water atomised iron powder has been HVC-formed into circular discs with high densities. The diametral compression test also called the Brazilian disc test is an established method to measure tensile strength in low strength material like e.g. rock, concrete, polymers and ceramics. During the test a thin disc is compressed across the diameter to failure. The compression induces a tensile stress perpendicular to the compressed diameter. In this study the test have been used to study crack initiation and the tensile fracture process of HVC-formed metal powder discs with a relative density of 99%. A fictitious crack model controlled by a stress versus crack-width relationship is utilized to model green body cracking. Tensile strength is used as a failure condition and limits the stress in the fracture interface. The softening rate of the model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic Cap model. The characteristics of the tensile fracture development of the central crack in a diametrically loaded specimen is numerically studied with a three dimensional finite element simulation. Results from the finite element simulation of the diametral compression test shows that it is possible to simulate fracturing of HVC-formed powder. Results from the simulation agree reasonably with experiments.

  17. Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual-Phase, Precipitation-Hardened, Powder Metallurgy Stainless Steels

    NASA Astrophysics Data System (ADS)

    Stewart, J. L.; Williams, J. J.; Chawla, N.

    2012-01-01

    The effects of thermal aging on the microstructure and mechanical behavior of dual-phase, precipitation-hardened, powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels, and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 811 K (538 °C) in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite nanohardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties.

  18. Critical current densities of Jelly-Roll and powder metallurgy Nb{sub 3}Al wires as a function of temperature and magnetic field

    SciTech Connect

    Thieme, C.L.H.; Kim, J.B.; Takayasu, M.

    1997-06-01

    Critical current densities of multi-filamentary Nb{sub 3}Al wire made with the Jelly-Roll process (JR) and mono-core powder metallurgy process (PM) wire were measured as a function of temperature and magnetic field. The temperature dependence of the resistive critical field B{sub c2} was measured in PM wires. There is a significant difference between these resistive B{sub c2} values and the ones determined by Kramer plots. The field dependence of the critical current depends on the manufacturing method. In general, it follows a relationship that falls between pure Kramer and one where the pinning force is inversely proportional with B{sup 2}. In contrast with Nb{sub 3}Sn no maximum in the bulk pinning force is observed down to 3 T (0.15MxB{sub c2}).

  19. Continuum-based FEM modeling of ceramic powder compaction using a cap-plasticity constitutive model

    SciTech Connect

    ARGUELLO JR.,JOSE G.; FOSSUM,ARLO F.; ZEUCH,DAVID H.; EWSUK,KEVIN G.

    2000-01-25

    Common ceramic component manufacturing typically involves the processing of the raw materials in powder form. Granulated powder is formed into a green body of the desired size and shape by consolidation, often by simply pressing nominally dry powder. Ceramic powders are commonly pressed in steel dies or rubber bags with the aim of producing a near-net-shape green body for subsequent sintering. Density gradients in these compacts, introduced during the pressing operation, are often severe enough to cause distortions in the shape of the part during sintering due to nonuniform shrinkage. In such cases, green machining or diamond grinding operations may be needed to obtain the desired final shape and size part. In severe cases, nonuniform shrinkage may even cause fracture in the parts during sintering. Likewise, density gradients can result in green bodies that break during ejection from the die or that are too fragile to be handled during subsequent processing. Empirical relationships currently exist to describe powder compaction but provide little understanding of how to control die design or compaction parameters to minimize density gradients thereby forcing the designer to use expensive and time consuming trial and error procedures. For this reason, interest has grown in developing computational tools to address this problem (Aydin et al., 1996 and Coube, 1998). The goal of the present work was to develop a general continuum-based finite element model for ceramic powder compaction that can be used to aid and guide the design and pressing of ceramic powders. Such a model can be used to improve both part and die/bag pressing design, resulting in more efficient and cost effective ways to make better parts.

  20. Investigation of compaction and sintering behavior of SiC powder after ultra-fine treatment.

    PubMed

    Guo, Xing-Zhong; Yang, Hui

    2004-08-01

    Silicon carbide ceramics were prepared with SiC powder treated by the fluidized bed opposed jet mill as raw materials, and the effects of the ultra-fine treatment mechanism on the compaction and sintering behavior of SiC ceramics were investigated. The results showed that the compacts had higher density and microstructure homogeneity when the sintering temperature of the compact was decreased; and that the surface microstructure, densification and mechanical properties of the sintered body could be ameliorated obviously. PMID:15236481

  1. High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

    SciTech Connect

    Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

    2000-05-10

    The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.

  2. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 250 citations and includes a subject term index and title list.)

  3. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    Not Available

    1994-12-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 250 citations and includes a subject term index and title list.)

  4. Decoupling of paramagnetic and ferrimagnetic AMS development during the experimental chemical compaction of illite shale powder

    NASA Astrophysics Data System (ADS)

    Bruijn, Rolf H. C.; Almqvist, Bjarne S. G.; Hirt, Ann M.; Benson, Philip M.

    2013-03-01

    Inclination shallowing of detrital remanent magnetization in sedimentary strata has solely been constrained for the mechanical processes associated with mud deposition and shallow compaction of clay-rich sediment, even though a significant part of mud diagenesis involves chemical compaction. Here we report, for the first time, on the laboratory simulation of magnetic assemblage development in a chemically compacting illite shale powder of natural origin. The experimental procedure comprised three compaction stages that, when combined, simulate the diagenesis and low-grade metamorphism of illite mud. First, the full extent of load-sensitive mechanical compaction is simulated by room temperature dry axial compression. Subsequently, temperature controlled chemical compaction is initiated by exposing the sample in two stages to amphibolite or granulite facies conditions (temperature is 490 to 750°C and confining pressure is 170 or 300 MPa) both in the absence (confining pressure only) and presence of a deformation stress field (axial compression or confined torsion). Thermodynamic equilibrium in the last two compaction stages was not reached, but illite and mica dehydroxylation initiated, thus providing a wet environment. Magnetic properties were characterized by magnetic susceptibility and its anisotropy (AMS) in both high- and low-applied field. Acquisition of isothermal remanent magnetization (IRM), stepwise three-component thermal de-magnetization of IRM and first-order reversal curves were used to characterize the remanence-bearing minerals. During the chemical compaction experiments ferrimagnetic iron-sulphides formed after reduction of magnetite and detrital pyrite in a low sulphur fugacity environment. The degree of low-field AMS is unaffected by porosity reduction from 15 to ˜1 per cent, regardless of operating conditions and compaction history. High-field paramagnetic AMS increases with compaction for all employed stress regimes and conditions, and is attributed to illite transformation to iron-bearing mica. AMS of authigenic iron-sulphide minerals remained constant during compaction indicating an independence of ferrimagnetic fabric development to chemical compaction in illite shale powder. The decoupling of paramagnetic and ferrimagnetic AMS development during chemical compaction of pelite contrasts with findings from mechanical compaction studies.

  5. Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

    1971-01-01

    Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

  6. A new titanium based alloy Ti-27Nb-13Zr produced by powder metallurgy with biomimetic coating for use as a biomaterial.

    PubMed

    Mendes, Marcio W D; Ágreda, Carola G; Bressiani, Ana H A; Bressiani, José C

    2016-06-01

    Titanium alloys are widely used in biomedical applications due to their excellent properties such as high strength, good corrosion resistance and biocompatibility. Titanium alloys with alloying elements such as Nb and Zr are biocompatible and have Young's modulus close to that of human bone. To increase the bioactivity of titanium alloy surfaces is used chemical treatment with NaOH followed by immersion in simulated body fluid (SBF). The purpose of this study was to produce the alloy Ti-27Nb-13Zr with low Young's modulus by powder metallurgy using powders produced by the HDH process. The formation of biomimetic coatings on samples immersed in SBF for 3, 7, 11 and 15days was evaluated. Characterization of the coating was performed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and scanning electron microscope. The microstructure and composition of the alloy were determined using SEM and XRD, while the mechanical properties were evaluated by determining the elastic modulus and the Vickers microhardness. The sintered alloys were composed of α and β phases, equiaxed grains and with density around 97.8% of its theoretical density. The Vickers microhardness and elasticity modulus of the alloy were determined and their values indicate that this alloy can be used as a biomaterial. Analysis of the coating revealed the presence of calcium phosphate layers on samples immersed for >3days in the SBF solution. PMID:27040264

  7. Phase composition, microstructure, and mechanical properties of porous Ti-Nb-Zr alloys prepared by a two-step foaming powder metallurgy method.

    PubMed

    Rao, X; Chu, C L; Zheng, Y Y

    2014-06-01

    Porous Ti-Nb-Zr alloys with different porosities from 6.06 to 62.8% are prepared by a two-step foaming powder metallurgy method using TiH2, Nb, and Zr powders together with 0 to 50wt% of NH4HCO3. The effects of the amounts of Nb and Zr as well as the sintering temperature (1473 to 1673K) on their phase composition, porosity, morphology, and mechanical characteristics are investigated. By controlling the porosity, Nb and Zr concentrations as well as the sintering temperature, porous Ti-Nb-Zr alloys with different mechanical properties can be obtained, for example, the hardness between 290 and 63HV, the compressive strength between 1530.5 and 73.4MPa, and the elastic modulus between 10.8 and 1.2GPa. The mechanical properties of the sintered porous Ti-Nb-Zr alloys can be tailored to match different requirements for the human bones and are thus potentially useful in the hard tissue implants. PMID:24556322

  8. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    1995-11-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  9. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    1998-03-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  10. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Cmpendex*plus database). Published Search

    SciTech Connect

    1997-03-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  11. Modelling of the mechanical behaviour of two pure PTFE powders during their compaction at room temperature

    NASA Astrophysics Data System (ADS)

    Frdy, Carole; Canto, Rodrigo B.; Schmitt, Nicolas; Roux, Stphane; Billardon, Ren

    2013-06-01

    Since PolyTetraFluoroEthylene (PTFE) is not melt processible because of its very high melt viscosity, parts made of this material are generally manufactured by cold compaction of powder material followed by sintering of the green compact. The aim of this study is to identify 3-D constitutive equations suitable for the finite element analysis of PTFE powder compaction. To exhibit the influence of their geometrical aspect on their mechanical behaviour, two pure PTFE resins were tested, viz. a free flowing pelletized resin and a granular fine cut resin. To study the behaviour of these powders during their compaction along different loading paths, a novel triaxial device has been designed and installed on a six-actuator triaxial testing machine. The results obtained for hydrostatic loading were favourably compared with results obtained by isostatic pressing. Various complex loading paths were also investigated. Full 3D elasto-viscoplastic non-associated constitutive equations, viz. a non-linear Drucker-Prager/cap type model, could be identified.

  12. A comparison of different powder compaction processes adopted for synthesis of lead-free piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Mahesh, M. L. V.; Bhanu Prasad, V. V.; James, A. R.

    2016-04-01

    Barium zirconium titanate, Ba(Zr0.15Ti0.85)O3 nano-crystalline powders were synthesized using high energy ball milling. The calcined powders were compacted adopting two different approaches viz. the conventional uniaxial pressing and cold-isostatic pressing (CIP) and the compacts were sintered at 1350 °C. A single phase perovskite structure was observed in both cases. BZT ceramics compacted using CIP technique exhibited enhanced dielectric and ferroelectric properties compared to ceramics compacted by uniaxial pressing. The polarization current peaks have been used in this paper as an experimental evidence to prove the existence of ferroelectricity in the BZT ceramics under study. The peak polarization current was found to be ~700% higher in case of cold iso-statically compacted ceramics. Similarly electric field induces strain showed a maximum strain ( S max) of 0.08% at an electric field of 28 kV/cm. The dielectric and ferroelectric properties observed are comparable to single crystals of the same material.

  13. Oxidation behavior in reaction-bonded aluminum-silicon alloy/alumina powder compacts

    SciTech Connect

    Yokota, S.H.

    1992-12-01

    Goal of this research is to determine the feasibility of producing low-shrinkage mullite/alumina composites by applying the reaction-bonded alumina (RBAO) process to an aluminum-silicon alloy/alumina system. Mirostructural and compositional changes during heat treatment were studied by removing samples from the furnace at different steps in the heating schedule and then using optical and scanning electron microscopy, EDS and XRD to characterize the powder compacts. Results suggest that the oxidation behavior of the alloy compact is different from the model proposed for the pure Al/alumina system.

  14. Shape memory characteristics and mechanical properties of powder metallurgy processed Ti50Ni40Cu10 alloy.

    PubMed

    Kim, Yeon-Wook

    2014-10-01

    Ti-Ni-Cu alloy powders were prepared by gas atomization and porous bulk specimens were fabricated by spark plasma sintering (SPS). The microstructure of as-solidified powders exhibited a cellular structure and they contained a high density of nano-sized porosities which were located in the intercellular regions. XRD analysis showed that one-step martensitic transformation of B2-B19 occurred in all alloy powders and SPS specimens. When the martensitic transformation start temperature (M(s)) and austenite transformation finish temperature (A(f)) were determined in order to analyze the dependence of powder size on transformation temperatures, the M(s) increased slightly from -17.5 degrees C to - 14.6 degrees C as increasing the powder size ranging from between 25 and 50 μm to ranging between 100 and 150 μm. However, the M(s) and A(f) of the as-atomized powders is much smaller than those of SPS specimens and the M(s) of porous specimen was about 10.9 degrees C. Loading-unloading compressive tests were carried out to investigate the mechanical properties of porous Ti-Ni-Cu specimen. The specimen was compressed to the strain of 6% at a temperature higher than A,. After unloading, the residual strain was 2.1%. After the compressed specimen was heated to 60 degrees C and held for 30 minutes and then cooled to room temperature, the changes in the length of the specimens were measured. Then it was found that the recovered strain ascribed to shape memory effect was 1.5%. PMID:25942923

  15. Consolidation processing parameters and alternative processing methods for powder metallurgy Al-Cu-Mg-X-X alloys

    NASA Technical Reports Server (NTRS)

    Sankaran, K. K.

    1987-01-01

    The effects of varying the vacuum degassing parameters on the microstructure and properties of Al-4Cu-1Mg-X-X (X-X = 1.5Li-0.2Zr or 1.5Fe-0.75Ce) alloys processed from either prealloyed (PA) or mechanically alloyed (M) powder, and consolidated by either using sealed aluminum containers or containerless vacuum hot pressing were studied. The consolidated billets were hot extruded to evaluate microstructure and properties. The MA Li-containing alloy did not include Zr, and the MA Fe- and Ce-containing alloy was made from both elemental and partially prealloyed powder. The alloys were vacuum degassed both above and below the solution heat treatment temperature. While vacuum degassing lowered the hydrogen content of these alloys, the range over which the vacuum degassing parameters were varied was not large enough to cause significant changes in degassing efficiency, and the observed variations in the mechanical properties of the heat treated alloys were attributed to varying contributions to strengthening by the sub-structure and the dispersoids. Mechanical alloying increased the strength over that of alloys of similar composition made from PA powder. The inferior properties in the transverse orientation, especially in the Li-containing alloys, suggested deficiencies in degassing. Among all of the alloys processed for this study, the Fe- and Ce-containing alloys made from MA powder possessed better combinations of strength and toughness.

  16. The equal channel angular pressing of magnesium and magnesium alloy powders

    NASA Astrophysics Data System (ADS)

    Moss, M.; Lapovok, R.; Bettles, C. J.

    2007-08-01

    Applications for magnesium powders have generally been restricted to the area of pyrotechnology, but with improved safety measures and novel processing technologies there are now more opportunities opening up for magnesium powder metallurgy components. Conventional powder metallurgy involving liquid phase sintering may not be a viable option, however, due to the high reactivity of molten magnesium in air. Solid-state consolidation processes are therefore desirable, with direct powder extrusion and equal channel angular pressing (ECAP) offering real alternatives to the conventional press/sinter routes. With this move toward purely solid-state metallurgy come opportunities for alternative alloy design strategies, potentially leading to microstructures not readily achieved through traditional casting routes. This paper will discuss the suitability of the ECAP route for magnesium powder compaction and explore the novel alloying strategies that become available with the success of these solid-state powder metallurgical processes.

  17. Heat-Treatment Effects on the Microstructure and Tensile Properties of Powder Metallurgy Ti-6Al-4V Alloys Modified with Boron

    NASA Astrophysics Data System (ADS)

    McEldowney, Dale J.; Tamirisakandala, Seshacharyulu; Miracle, Daniel B.

    2010-04-01

    The Ti-6Al-4V (Ti-64) alloys modified with two levels of boron (1B and 1.7B (wt pct)) representing hypoeutectic and hypereutectic compositions, produced via a prealloyed powder metallurgy approach, were subjected to various standard heat treatments of Ti-64 to study the microstructural evolution and its influence on tensile properties. Boron-modified Ti-64 (Ti-64B) alloys exhibited differences in microstructural response to heat treatment compared to that of Ti-64 due to variations in constituent phase fractions and the influence of TiB on the beta-to-alpha phase transformation kinetics. The tensile elastic modulus of Ti-64B alloys increased nearly linearly with the boron content (or TiB volume fraction) and the increase could be satisfactorily predicted with an isostrain rule of mixtures (ROMs) and the Halpin-Tsai model. The Ti-64-1B possessed a good combination of tensile strength (1200 to1370 MPa) and ductility (10 to 13 pct), while Ti-64-1.7B exhibited high strength (1300 to 1695 MPa) and modest ductility (2 to 3.5 pct). Coarse primary TiB particles present in Ti-64-1.7B were found to initiate premature failure. Strength modeling revealed that load sharing by the micron-sized TiB whiskers provides the major contribution for the increase in yield strength.

  18. Influence of pre-heating on the surface modification of powder-metallurgy processed cold-work tool steel during laser surface melting

    NASA Astrophysics Data System (ADS)

    Šturm, Roman; Štefanikova, Maria; Steiner Petrovič, Darja

    2015-01-01

    In this study we determine the optimal parameters for surface modification using the laser surface melting of powder-metallurgy processed, vanadium-rich, cold-work tool steel. A combination of steel pre-heating, laser surface melting and a subsequent heat treatment creates a hardened and morphologically modified surface of the selected high-alloy tool steel. The pre-heating of the steel prior to the laser surface melting ensures a crack- and pore-free modified surface. Using a pre-heating temperature of 350 °C, the extremely fine microstructure, which typically evolves during the laser-melting, became slightly coarser and the volume fraction of retained austenite was reduced. In the laser-melted layer the highest values of microhardness were achieved in the specimens where a subsequent heat treatment at 550 °C was applied. The performed thermodynamic calculations were able to provide a very valuable assessment of the liquidus temperature and, especially, a prediction of the chemical composition as well as the precipitation and dissolution sequence for the carbides.

  19. Effect of Extrusion Temperature on the Microstructural Development of Powder Metallurgy Ti-47A1-2Cr-1Nb-1Ta Alloy

    SciTech Connect

    Hsiung, L.; Nieh, T.G.

    2000-06-29

    Effect of extrusion temperatures on the microstructural development of a powder metallurgy (PM) Ti-47Al-2Cr-1Nb-1Ta (at. %) alloy has been investigated. Microstructure of the PM alloy extruded at 1150 C consists of a fine-grained ({gamma} + {alpha}{sub 2}) two-phase structure in association with coarse grains of metastable B2 (ordered bcc) phase. In addition, fine {omega} (ordered hexagonal) particles are also found within some B2 grains. The PM alloy containing the metastable B2 grains displays a low-temperature superplastic behavior, in which a tensile elongation of 310% is obtained at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. It is suggested that the decomposition of metastable B2 phase and microstructural evolution during the deformation play a crucial role in the low-temperature superplasticity of the PM TiAl alloy. A refined fully-lamellar (FL) microstructure with alternating {gamma} and {alpha}{sub 2} lamellae is developed within the PM alloy extruded at 1400 C. The creep resistance of the refined FL-TiAl alloy is found to be superior to those of the TiAl alloys fabricated by conventional processing techniques. Creep mechanisms for the PM alloy with a refined FL microstructure are critically discussed according to TEM examination of deformation substructure.

  20. The Influences of Carbon and Molybdenum on the Progress of Liquid Phase Sintering and the Microstructure of Boron-Containing Powder Metallurgy Steel

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Wei

    2015-01-01

    Boron is an optimal alloying element for liquid phase sintering (LPS) of powder metallurgy (PM) Fe-based materials. However, the influences of various alloying elements on the progress of LPS are still undetermined. The aim of this study was to clarify the effects of carbon and molybdenum on the LPS and microstructure of boron-containing PM steel. The results showed that adding 0.5 wt pct C and 1.5 wt pct Mo, and particularly the former, promotes the LPS and increases the sintered density. With the addition of 0.5 wt pct C, liquid can be generated in two distinct regions, and the secondary liquid improves the densification. After 1523 K (1250 °C) sintering, the increases in sintered densities of Fe-0.4B, Fe-0.4B-1.5Mo, Fe-0.4B-0.5C, and Fe-0.4B-1.5Mo-0.5C steels were 0.33, 0.47, 0.56, and 0.64 g/cm3, respectively. Thermodynamic simulation also demonstrated that the increases in sintered densities were correlated with the liquid volumes formed at 1523 K (1250 °C). In conclusion, adding 0.5 wt pct C to B-containing PM steels facilitates the formation of a secondary liquid phase and higher liquid volume, resulting in better densification.

  1. Ni{sub 3}Al intermetallic particles as wear-resistant reinforcement for Al-base composites processed by powder metallurgy

    SciTech Connect

    Diaz, C.; Gonzalez-Carrasco, J.L.; Caruana, G.; Lieblich, M.

    1996-10-01

    The suitability of Ni{sub 3}Al intermetallics as reinforcement for Al-base materials for tribological applications has been investigated. For this purpose, an Al/Ni{sub 3}Al (5 vol pct) composite was prepared by powder metallurgy and tested in air against steel counterfaces at the load range of 45 to 178 N. For comparison, unreinforced Al specimens were processed and tested under the same conditions. Tribological behavior was evaluated by microstructural examination of wear-affected zones and weight-loss measurements of specimens and counterfaces. It was found that a significant amount of Fe-rich oxide particles become incorporated into the Al matrix during wear, forming a cracked tribolayer. The wear behavior of Al/Ni{sub 3}Al composite as a function of the applied load was not accurately reflected by the weight loss of worn specimens. Results highlight the role of Ni{sub 3}Al particles as load-bearing elements due to their excellent bonding to the Al matrix, their interfaces withstanding the wear stresses even at the highest applied load. Moreover, Ni{sub 3}Al particles limited the incorporation of wear debris to the Al matrix and reduced wear damage occasioned to the steel counterfaces compared to that of pure aluminum specimens.

  2. Effects of tantalum addition on hysteresis losses and critical current densities of powder-metallurgy processed Nb{sub 3}Sn superconducting wires

    SciTech Connect

    Matsukura, N.; Fukumoto, Y.; Miyazaki, T.

    1997-06-01

    Powder-metallurgy processed (PMP) multifilamentary Nb{sub 3}Sn superconducting wires have been fabricated. The critical current densities and hysteresis losses of the wires are measured and the effects of tantalum addition to niobium on them are investigated. Although tantalum addition decreases both the critical current densities and the hysteresis losses, the reduction of the hysteresis loss is more pronounced. As a result, the effective filament diameter is diminished. The critical current density of the PMP Nb{sub 3}Sn wire may depend on the combination of the bridging among Nb{sub 3}Sn filaments and the supernormal interface pinning centers. This wire includes 3721 composite cores which consist of copper and Nb{sub 3}Sn. The non-homogeneous deformation of filaments is reduced by tantalum additions. Both the bridging among Nb{sub 3}Sn filaments and the super-normal interface pinning center energies may be reduced by tantalum additions, and therefore depressing the critical current density. Tantalum additions also depress the sausage-like deformation of composite cores, suggesting that both bridging and coupling among the composite cores is suppressed. Consequently both the hysteresis loss and the effective filament diameter are decreased.

  3. Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel

    NASA Astrophysics Data System (ADS)

    Yao, Jun; Qu, Xuan-hui; He, Xin-bo; Zhang, Lin

    2012-07-01

    The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30 ?m prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPam1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

  4. Study of the mechanical stability and bioactivity of Bioglass(®) based glass-ceramic scaffolds produced via powder metallurgy-inspired technology.

    PubMed

    Boccardi, Elena; Melli, Virginia; Catignoli, Gabriele; Altomare, Lina; Jahromi, Maryam Tavafoghi; Cerruti, Marta; Lefebvre, Louis-Philippe; De Nardo, Luigi

    2016-02-01

    Large bone defects are challenging to heal, and often require an osteoconductive and stable support to help the repair of damaged tissue. Bioglass-based scaffolds are particularly promising for this purpose due to their ability to stimulate bone regeneration. However, processing technologies adopted so far do not allow for the synthesis of scaffolds with suitable mechanical properties. Also, conventional sintering processes result in glass de-vitrification, which generates concerns about bioactivity. In this work, we studied the bioactivity and the mechanical properties of Bioglass(®) based scaffolds, produced via a powder technology inspired process. The scaffolds showed compressive strengths in the range of 5-40 MPa, i.e. in the upper range of values reported so far for these materials, had tunable porosity, in the range between 55 and 77%, and pore sizes that are optimal for bone tissue regeneration (100-500 μm). We immersed the scaffolds in simulated body fluid (SBF) for 28 d and analyzed the evolution of the scaffold mechanical properties and microstructure. Even if, after sintering, partial de-vitrification occurred, immersion in SBF caused ion release and the formation of a Ca-P coating within 2 d, which reached a thickness of 10-15 μm after 28 d. This coating contained both hydroxyapatite and an amorphous background, indicating microstructural amorphization of the base material. Scaffolds retained a good compressive strength and structural integrity also after 28 d of immersion (6 MPa compressive strength). The decrease in mechanical properties was mainly related to the increase in porosity, caused by its dissolution, rather than to the amorphization process and the formation of a Ca-P coating. These results suggest that Bioglass(®) based scaffolds produced via powder metallurgy-inspired technique are excellent candidates for bone regeneration applications. PMID:26836444

  5. Ductilization of a powder metallurgy Al-17 wt pct Cu by means of channel-die compression and extrusion

    SciTech Connect

    Maire, E.; Wilkinson, D.S.; Embury, J.D.; Henein, H.

    1998-10-01

    Metal powders always contain a surface oxide layer, which is particularly tenacious in aluminum alloys. After hot pressing, this oxide coats the particle boundaries and reduces the ductility. In this article, a study of the Al-17 wt pct Cu alloy densified from rapidly solidified powder is presented. Different thermomechanical treatments were investigated to improve the ductility of this material. Channel-die (CD) forging was performed at two temperatures (430 C and 500 C). Eight compression runs were applied to the samples in each CD treatment. At 430 C, three strain values per run were investigated (35, 50 and 70 pct). A bar was also extruded with a 40:1 ratio. Because of the small size of the samples, the ductility was assessed by means of the ring expansion test and analyzed by post mortem (fracture surface and cross section) observations. No ductility was measured after CD compression at 430 C, although it appears from the fracture surface observations that increasing the strain per tun has a beneficial effect. The CD compression at 500 C and extrusion were both successful at promoting ductility, extrusion being more effective.

  6. Tensile creep deformation and fracture behaviors of the lamellar TiAl alloy of elemental powder metallurgy

    SciTech Connect

    Cho, H.S.; Nam, S.W.; Hwang, S.K.; Kim, N.J.

    1997-06-01

    The creep behaviors of the lamellar structured gamma TiAl alloys processed by castings, wrought and P/M using pre-alloyed powder have been reported. However, so far there has been no report on the creep behaviors of the gamma TiAl alloy processed by a hot extrusion of a blended elemental powder mixture. As such, the need to examine the creep behavior of this alloy has prompted the current research. The creep deformation mechanism based on the activation energy and stress exponent is discussed. In addition, the results of microstructural observations with TEM and optical microscope in the condition of beginning of secondary stage and creep fracture are also presented. Under the basis of the measured apparent activation energy and TEM observation for the dislocation structure, the creep deformation of the EPM alloy under the conditions of 150--250 MPa/775--900 C is assumed to be progressed by the dislocation glide in the {gamma} lath but is considered to be controlled by the dislocation climb. However, in condition of 100--150 MPa/800 C, it is suggested that the diffusional creep dominates the creep deformation rather than dislocation motion. Pore formation and coalescence at the lamellar grain boundaries having the normal direction to the tensile stress axis are observed to be the cause of the creep fracture.

  7. Tailoring the microstructure and the mechanical properties of ultrafine grained high strength ferritic steels by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Mouawad, B.; Boulnat, X.; Fabrègue, D.; Perez, M.; de Carlan, Y.

    2015-10-01

    Three model powder materials (i) atomized, (ii) atomized + milled, and, (iii) atomized + milled + alloyed with yttria (Y2O3) and titanium were consolidated within Spark Plasma Sintering device at 850, 950 and 1050°C. Depending on the materials, nanostructured, or even bimodal grain size distribution can be observed. These structures lead to a wide range of mechanical behavior: the tensile strength at room temperature can be tailored from 500 to 1200 MPa with total elongation from 8 to 35%. The bimodal grain size distribution is believed to provide both good yield stress and ductility. Finally, a yield stress model based on the effect of solute atoms, dislocations, grains boundaries and precipitates is presented and it permits to predict accurately the experimental values for all specimens and conditions.

  8. Effects of C and Hf concentration on phase relations and microstructure of a wrought powder-metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.

    1977-01-01

    NASA IIB-11, a candidate alloy for advanced temperature turbine engine disks, and four modifications with varying C and Hf concentrations were produced from prealloyed powders. Several notable effects of C and Hf concentration in the alloys were observed. Both the amount of the gamma-prime phase and its solvus temperature increased with decreasing C, but only the gamma-prime solvus was affected by Hf, increasing with increasing Hf. Hf also promoted a cellular gamma-prime precipitation. Hf was, however, about equally distributed between gamma-prime and gamma. Hf and C both affected the carbides formed. Increasing both promoted formation of an MC relative to that of an M6C.

  9. Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-02-01

    The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains a minimum of 115 citations and includes a subject term index and title list.)

  10. Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent database). Published Search

    SciTech Connect

    Not Available

    1993-05-01

    The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains a minimum of 97 citations and includes a subject term index and title list.)

  11. Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. (Contains a minimum of 109 citations and includes a subject term index and title list.)

  12. Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1997-01-01

    The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  13. Tungsten and tungsten alloy powder metallurgy: Powder production and applications excluding lamps. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-12-01

    The bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys, including applications of these materials. The hydrogen reduction of tungsten compounds together with alloying element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  14. Microstructures, Mechanical Properties, and Shape Memory Characteristics of Powder Metallurgy Ti51Ni49 Modified with Boron

    NASA Astrophysics Data System (ADS)

    Yen, Fu-Cheng; Hwang, Kuen-Shyang

    2012-02-01

    Ti51Ni49 compacts consolidated with persistent liquid-phase sintering usually contain Ti2Ni networks at the grain boundaries, which cause adverse effects on mechanical properties. With 0.5 and 1.0 at pct B additions, fine TiB forms during heating and sintering and acts as a nucleation site for Ti2Ni to precipitate within the grain during cooling. The resultant uniform distribution of TiB and Ti2Ni impedes grain growth and prevents the formation of continuous Ti2Ni precipitates at grain boundaries. As a result, a significant increase in tensile elongation, and not a decrease, as in most as-cast titanium alloys, is obtained because of these changes. The tensile strength also increases, without deterioration of the shape memory characteristics. The tensile strength and elongation are close to those of wrought TiNi alloys.

  15. Characterization techniques to validate models of density variations in pressed powder compacts

    SciTech Connect

    Garino, T.; Mahoney, M.; Readey, M.; Ewsuk, K.; Gieske, J.; Stoker, G.; Min, S.

    1995-07-01

    Techniques for characterizing density gradients generated during typical powder compaction processes are reviewed and several are evaluated. The techniques reviewed are ultrasonic velocity measurements, laser ultrasonic velocity measurements, x-ray radiography, autoradiography, computer tomography (CT), magnetic resonance imaging (MRI), and simple image analysis of polished cross-sections. Experimental results are reported for all of these techniques except autoradiography, CT and MRI. The test specimens examined were right circular cylinders of a high length/diameter ratio (to ensure significant density variation) pressed from commercial spray-dried alumina powders. Although the density gradients could be detected with all four techniques, ultrasonic velocity measurements gave the best contour map of gradients and is therefore most suitable for model validation. On the other hand, it was concluded that x-ray radiography is preferable in situations where cost and/or number of samples are more important that high resolution.

  16. Roller compaction: Effect of morphology and amorphous content of lactose powder on product quality.

    PubMed

    Omar, Chalak S; Dhenge, Ranjit M; Osborne, James D; Althaus, Tim O; Palzer, Stefan; Hounslow, Michael J; Salman, Agba D

    2015-12-30

    The effect of morphology and amorphous content, of three types of lactose, on the properties of ribbon produced using roller compaction was investigated. The three types of lactose powders were; anhydrous SuperTab21AN, α-lactose monohydrate 200 M, and spray dried lactose SuperTab11SD. The morphology of the primary particles was identified using scanning electron microscopy (SEM) and the powder amorphous content was quantified using NIR technique. SEM images showed that 21AN and SD are agglomerated type of lactose whereas the 200 M is a non-agglomerated type. During ribbon production, an online thermal imaging technique was used to monitor the surface temperature of the ribbon. It was found that the morphology and the amorphous content of lactose powders have significant effects on the roller compaction behaviour and on ribbon properties. The agglomerated types of lactose produced ribbon with higher surface temperature and tensile strength, larger fragment size, lower porosity and lesser fines percentages than the non-agglomerated type of lactose. The lactose powder with the highest amorphous content showed to result in a better binding ability between the primary particles. This type of lactose produced ribbons with the highest temperature and tensile strength, and the lowest porosity and amount of fines in the product. It also produced ribbon with more smooth surfaces in comparison to the other two types of lactose. It was noticed that there is a relationship between the surface temperature of the ribbon during production and the tensile strength of the ribbon; the higher the temperature of the ribbon during production the higher the tensile strength of the ribbon. PMID:26117279

  17. αTCP ceramic doped with dicalcium silicate for bone regeneration applications prepared by powder metallurgy method: in vitro and in vivo studies.

    PubMed

    Velasquez, Pablo; Luklinska, Zofia B; Meseguer-Olmo, Luis; Mate-Sanchez de Val, Jose E; Delgado-Ruiz, Rafael A; Calvo-Guirado, Jose L; Ramirez-Fernandez, Ma P; de Aza, Piedad N

    2013-07-01

    This study reports on the in vitro and in vivo behavior of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 or 3.0 wt % of dicalcium silicate (C2 S). The ceramics were successfully prepared by powder metallurgy method combined with homogenization and heat treatment procedures. All materials were composed of a single-phase, αTCP in the case of a pure material, or solid solution of C2 S in αTCP for the doped αTCP, which were stable at room temperature. The ceramics were tested for bioactivity in simulated body fluid, cell culture medium containing adult mesenchymal stem cells of human origin, and in animals. Analytical scanning electron microscopy combined with chemical elemental analysis was used and Fourier transform infrared and conventional histology methods. The in vivo behavior of the ceramics matched the in vitro results, independently of the C2 S content in αTCP. Carbonated hydroxyapatite (CHA) layer was formed on the surface and within the inner parts of the specimens in all cases. A fully mineralized new bone growing in direct contact with the implants was found under the in vivo conditions. The bioactivity and biocompatibility of the implants increased with the C2 S content in αTCP. The C2 S doped ceramics also favoured a phase transformation of αTCP into CHA, important for full implant integration during the natural bone healing processes. αTCP ceramic doped with 3.0 wt % C2 S showed the best bioactive in vitro and in vivo properties of all the compositions and hence could be of interest in specific applications for bone restorative purposes. PMID:23225787

  18. Correlations between the in vitro and in vivo bioactivity of the Ti/HA composites fabricated by a powder metallurgy method.

    PubMed

    Ning, Congqin; Zhou, Yu

    2008-11-01

    Ti/HA composites were successfully prepared by a powder metallurgy method and the effect of phase composition on the in vitro and in vivo bioactivity of the Ti/HA composites was investigated in the present study. The correlations between the in vitro and in vivo biological behaviors were highlighted. The results showed that the in vitro and in vivo bioactivity of the Ti/HA composites was dependent on their phase composition. The in vitro bioactivity of the Ti/HA composites was evaluated in simulated body fluid with ion concentrations similar to those of human plasma. After immersion in the simulated body fluid for a certain time, apatite precipitations formed on the surface of the composites with an initial titanium content of 50 and 70 wt.%, and no apatite was found on the surface of the composite with 30% titanium. Ti(2)O was responsible for the apatite formation on the surfaces of the composites. For in vivo analysis, Ti/HA cylinders were implanted in the metaphases of the rabbit femur. At the early stage of implantation, the new bone formed on the surface of the composite with 30% titanium was much less than that on the surfaces of the composites with 50% and 70% titanium. All the Ti/HA composites formed a chemical bone-bonding interface with the host bone by 6 months after implantation. The Ti/HA composites formed the bone-bonding interface with the surrounding bone through an apatite layer. The results in the present study suggested that the in vivo results agreed well with the in vitro results. PMID:18502711

  19. The Influence of Sc and Zr Additions on the Microstructure and Mechanical Behavior of Ultrafine Grained Al-Mg Alloys Processed by Powder Metallurgy

    NASA Astrophysics Data System (ADS)

    Harrell, Tammy Jeanne

    Additions of Sc and Zr to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc and Zr significantly increase the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultra-fine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigate the microstructural evolution and mechanical behavior of four powder metallurgy UFG Al-Mg-Sc-(Zr) compositions and compared the results to those of equivalent fine-grained (FG) compositions - Al-5Mg-0.1Sc, Al-3Mg-0.5Sc, Al-5Mg-0.4Sc and Al-5Mg-0.2Sc-0.2Zr (wt.%). Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic (DMD) forging. Under identical processing conditions, UFG ternary Al-5Mg-0.4Sc materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 - 3 μm apart, while precipitates in the FG materials have an average diameter of 24 nm and are spaced 50 - 200 nm apart. The strengthening mechanisms are quantitatively evaluated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are dispersion strengthening due to the presence of Mg-rich oxides/nitrides and precipitate strengthening, respectively. Preliminary results suggest that replacing 0.2 wt% Sc with Zr results in higher strength, lower ductility and a change in precipitate distribution.

  20. 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.

  1. A Numerical Study of Material Parameter Sensitivity in the Production of Hard Metal Components Using Powder Compaction

    NASA Astrophysics Data System (ADS)

    Andersson, Daniel C.; Lindskog, Per; Staf, Hjalmar; Larsson, Per-Lennart

    2014-06-01

    Modeling of hard metal powder inserts is analyzed based on a continuum mechanics approach. In particular, one commonly used cutting insert geometry is studied. For a given advanced constitutive description of the powder material, the material parameter space required to accurately model the mechanical behavior is determined. These findings are then compared with the corresponding parameter space that can possibly be determined from a combined numerical/experimental analysis of uniaxial die powder compaction utilizing inverse modeling. The analysis is pertinent to a particular WC/Co powder and the finite element method is used in the numerical investigations of the mechanical behavior of the cutting insert.

  2. Microstructures and Tensile Mechanical Properties of Titanium Rods Made by Powder Compact Extrusion of a Titanium Hydride Powder

    NASA Astrophysics Data System (ADS)

    Zheng, Yifeng; Yao, Xun; Liang, Jiamiao; Zhang, Deliang

    2016-04-01

    Nearly fully dense titanium with good mechanical properties was fabricated rapidly by induction heating, holding, and hot extrusion of the TiH2 powder compacts. The dehydrogenation and consolidation processes took less than 15 minutes in total. The microstructures, contents of interstitial elements (H, O), tensile mechanical properties, and fracture behaviors of titanium samples made with different holding and extrusion temperatures [1273 K, 1373 K, and 1473 K (1000 °C, 1100 °C, and 1200 °C)] were investigated. The results showed that the hydrogen content in the extruded rods was around 0.09 wt pct when the holding and extrusion temperature was 1373 K or 1473 K (1100 °C or 1200 °C), with almost all of the TiH2 phase being transformed into Ti phase during the heating, holding, and extrusion process steps. The extruded Ti samples had a lamellar structure consisting of fine α lamellae with random orientations in different lamellar colonies and the relative density of all the extruded samples exceeded 99.5 pct. The residual TiH2 phase can reduce the ductility of extruded rods. The sample extruded at 1373 K (1100 °C) has the best elongation to fracture of 21.0 pct, and its average yield strength and ultimate tensile strength reached 536.8 and 691.8 MPa, respectively.

  3. High temperature mechanical properties of Ti-47Al-2Cr (at %) alloy produced using powder compact forging of a mechanically milled powder

    NASA Astrophysics Data System (ADS)

    Nadakuduru, V. N.; Zhang, D. L.; Cao, P.; Gabbitas, B.

    2009-08-01

    Ultrafine grained (UFG) Ti-47Al-2Cr (at %) alloy was prepared using a combination of high energy ball milling of a mixture of elemental powders to produce a Ti/Al/Cr composite powder and forging of compacts of this composite powder. The microstucture of the powder forged alloy was found to be dependent on the initial condition of the powder. The alloy produced by this method has demonstrated good formability, both in tensile and compression testings at elevated temperatures. A ductility of 80-165% in tension has been observed, while in a compression plastic strain of ~ 50% was found to be easily achievable, without causing cracking. The deformation behaviour of the particular alloy in tension and compression at elevated temperature has been discussed in detail. The results from the present investigation indicate that UFG Ti-47Al-2Cr (at %) alloy produced using powder compact forging has good formability, and is suitable precursor for near-net shaping using thermomechanical processes such as forging and superplastic forming.

  4. History of ``NANO''-Scale VERY EARLY Solid-State (and Liquid-State) Physics/Chemistry/Metallurgy/ Ceramics; Interstitial-Alloys Carbides/Nitrides/Borides/...Powders and Cermets, Rock Shocks, ...

    NASA Astrophysics Data System (ADS)

    Maiden, Colin; Siegel, Edward

    History of ``NANO'': Siegel-Matsubara-Vest-Gregson[Mtls. Sci. and Eng. 8, 6, 323(`71); Physica Status Solidi (a)11,45(`72)] VERY EARLY carbides/nitrides/borides powders/cermets solid-state physics/chemistry/metallurgy/ ceramics FIRST-EVER EXPERIMENTAL NANO-physics/chemistry[1968 ->Physica Status Solidi (a)11,45(`72); and EARLY NANO-``physics''/NANO-``chemistry'' THEORY(after: Kubo(`62)-Matsubara(`60s-`70s)-Fulde (`65) [ref.: Sugano[Microcluster-Physics, Springer('82 `98)

  5. Shock Compaction of MnAs1-xSbx Powder Using Underwater Shock Wave

    NASA Astrophysics Data System (ADS)

    Kim, Y. K.; Wada, H.; Itoh, S.

    2007-12-01

    MnAs1-xSbx material is one of the ferromagnets which can contribute to a magnetic refrigeration system that is useable at room temperature. The consolidation experiments of MnAs1-xSbx (x = 0.068, 0.073) powder are carried out by a shock compaction method using underwater shock wave with shock pressure of 16 GPa. The magnetic entropy change, ΔSmag, of annealed sample (x = 0.073) after press caused by a magnetic field of 1 T is 27.8 J/Kkg at the maximum value, and the sample annealed after press undergoes a first-order ferromagnetic to paramagnetic transition at 304.05 K.

  6. EXPLOSIVE COMPACTION OF CLAD GRAPHITE POWDERS AND OBTAINING OF COATINGS ON THEIR BASE

    SciTech Connect

    A. B. PEIKRISHIVILI; ET AL

    2000-11-01

    In order to consolidate graphite based powders and in order to obtain coatings with density values near to the theoretical ones clad graphite powders of the C{sub graphite} - Ni (C{sub g} - Ni) compositions were explosively compacted under different loading conditions. Theoretical calculations revealed that for assessing the stress-deformed state of C{sub g} - Ni compositions and computing the normal and tangent stress components (when V{sub D} < C{sub longitudinal} and V{sub D} < C{sub transversal}) it is recommended to apply the dynamic problem's solution model while the pressure impulse P = f(x) is being uniformly spread with constant rate along the boundary of a semi-infinite elastic body. The results of our experiments showed that it is possible to obtain high dense coatings from C{sub g}-Ni compositions bonded by an intermediate layer to the substrate material. The structure and properties of the coatings depends on the intensity of the shock loading and temperature. The effect of the shock loading conditions (temperature, loading intensity) on the structure, properties and structure/properties relationships for the C{sub g} - Ni coatings are discussed.

  7. Plutonium Metallurgy

    SciTech Connect

    Freibert, Franz J.

    2012-08-09

    Due to its nuclear properties, Pu will remain a material of global interest well into the future. Processing, Structure, Properties and Performance remains a good framework for discussion of Pu materials science Self-irradiation and aging effects continue to be central in discussions of Pu metallurgy Pu in its elemental form is extremely unstable, but alloying helps to stabilize Pu; but, questions remain as to how and why this stabilization occurs. Which is true Pu-Ga binary phase diagram: US or Russian? Metallurgical issues such as solute coring, phase instability, crystallographic texture, etc. result in challenges to casting, processing, and properties modeling and experiments. For Ga alloyed FCC stabilized Pu, temperature and pressure remain as variables impacting phase stability.

  8. Experimental studies and modeling of the roller compaction of pharmaceutical powders

    NASA Astrophysics Data System (ADS)

    Cunningham, John C.

    During roller compaction in the pharmaceutical industry, mixtures of active and inert powders are fed via a screw to counter-rotating rolls, drawn into the nip and compacted under hydrostatic and shear stresses. Experimental studies were conducted using microcrystalline cellulose on a roller compactor that measured feed force, surface roll pressure and shear stress. The following observations were made: densification correlated with maximum roll pressure; increasing feed force increased roll gap; and significant variation in roll pressure and shear stress exists in the transverse and rolling directions. A slab model highlighted the importance of roll friction, feed stress and entry angle on pre-densification in the feed zone. 2-D and 3-D explicit finite element models with adaptive meshing and arbitrary Eulerian-Lagrangian capabilities were developed. A Drucker-Prager/cap model was calibrated using diametrical and simple compression and die compaction tests. The roll friction was estimated using a die instrumented to measure radial stress. The effects of roll friction, feed stress, roll gap to diameter and entry angle on roll force, torque, profiles of roll pressure and roll shear stress, nip angle, neutral angle, and relative density were evaluated. The results indicated increasing entry angle, decreasing roll gap to diameter, increasing feed stress and/or increasing roll friction lead to higher maximum roll surface pressure and attendant relative density at the exit. The results may be explained by the nip angle and amount of pre-densification. Simulations with pressure-dependent frictional coefficients indicated significant difference in densification. Oscillating feed stress conditions revealed periodic variations in roll pressures and relative densities. Variations in the through-the-thickness were significant in the slip region and diminished in the nip region. The 3-D model predicted lower roll pressure and densities near the edges due to side seal friction. In addition, variable inflow of material along the roll width was related to variation in roll pressure. Overall, the model predictions followed experimental trends. Microcrystalline cellulose experienced higher expansion on release than predicted---related to its non-linear elastic behavior. Various combinations of boundary conditions and geometrical parameters resulted in similar roll pressure profiles and densification thus accurate experimental inputs are essential for model verification.

  9. Investigation of the potential for direct compaction of a fine ibuprofen powder dry-coated with magnesium stearate.

    PubMed

    Qu, Li; Zhou, Qi Tony; Gengenbach, Thomas; Denman, John A; Stewart, Peter J; Hapgood, Karen P; Gamlen, Michael; Morton, David A V

    2015-05-01

    Intensive dry powder coating (mechanofusion) with tablet lubricants has previously been shown to give substantial powder flow improvement. This study explores whether the mechanofusion of magnesium stearate (MgSt), on a fine drug powder can substantially improve flow, without preventing the powder from being directly compacted into tablets. A fine ibuprofen powder, which is both cohesive and possesses a low-melting point, was dry coated via mechanofusion with between 0.1% and 5% (w/w) MgSt. Traditional low-shear blending was also employed as a comparison. No significant difference in particle size or shape was measured following mechanofusion. For the low-shear blended powders, only marginal improvement in flowability was obtained. However, after mechanofusion, substantial improvements in the flow properties were demonstrated. Both XPS and ToF-SIMS demonstrated high degrees of a nano-scale coating coverage of MgSt on the particle surfaces from optimized mechanofusion. The study showed that robust tablets were produced from the selected mechanofused powders, at high-dose concentration and tablet tensile strength was further optimized via addition of a Polyvinylpyrrolidone (PVP) binder (10% w/w). The tablets with the mechanofused powder (with or without PVP) also exhibited significantly lower ejection stress than those made of the raw powder, demonstrating good lubrication. Surprisingly, the release rate of drug from the tablets made with the mechanofused powder was not retarded. This is the first study to demonstrate such a single-step dry coating of model drug with MgSt, with promising flow improvement, flow-aid and lubrication effects, tabletability and also non-inhibited dissolution rate. PMID:24738790

  10. 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.

  11. Investigation of thermal conductivity and microstructure of the α-Al 2O 3 particulate reinforced aluminum composites (Al/Al 2O 3-MMC) by powder metallurgy method

    NASA Astrophysics Data System (ADS)

    Tatar, C.; Özdemir, N.

    2010-02-01

    The thermal conductivity of the α-Al 2O 3 particulate reinforced aluminum composites (Al/Al 2O 3-MMC) prepared by powder metallurgy method have been investigated. The thermal conductivity shows linear dependence on temperature in the investigated range. The increase in the thermal conductivity of the composites with decreasing Al 2O 3 particles size could be due to greater stability of the thermal conductive paths for smaller Al 2O 3 particles. In addition, when composites are heated, the heat will tend to flow through the Al particles and electric charge flows where resistance is lowest. It is seen that the thermal conductivity decrease with increasing Al 2O 3 volume fraction.

  12. Compaction of TiH sub 1. 65 /KClO sub 4 pyrotechnic powder during confined burn

    SciTech Connect

    Hingorani-Norenberg, S.L. ); Razani, A.; Shahinpoor, M. . Dept. of Mechanical Engineering)

    1990-01-01

    The burning behavior of titanium subhydride potassium perchlorate (TiH{sub 1.65}/KClO{sub 4}) is currently under investigation. The research is presently aimed at studying the dynamic compaction of the material as a confined cylindrical charge of the pyrotechnic burns. Flash radiography equipment, optical fibers, and piezoelectric pressure transducers are used to study this phenomenon. The length to diameter ratio of the test charge is thirty and it is pressed in increments, which have a length to diameter ratio of one, into a cylindrical fixture consisting of an epoxy liner in a stainless steel housing. The housing has a series of radial holes to allow optical monitoring, through the transparent liner, of the ignition-front. Lead disks, placed between increments of powder, serve as x-ray tracers. Three 300 kilovolt x-ray heads are pulsed during each experiment, providing information regarding the state of compaction of the powder at three different times during the burn. Fiber optics are used to monitor the location of the ignition front. Pressure transducers monitor the pressure history inside the closed bomb. Tests have been performed with the powder at different initial densities and the data indicate that a significant amount of compaction occurs as the charge burns. 7 refs., 6 figs.

  13. Pressing device for producing compacts from source material in powder form in particular pulverized nuclear reactor fuel

    SciTech Connect

    Heller, G.; Adelmann, M.; Konigs, W.; Wendorf, W.

    1984-04-17

    Pressing device for producing compacts from source material in powder form, in particular pulverized nuclear reactor fuel having a die-plate contained in platen and a bore associated with a ram, for receiving source material powder, a filling shoe, and a reservoir for powder connected by a hose to the filling shoe. The device is characterized by a passing wheel in the filling shoe as filling aid means; a tube containing a feedscrew disposed between the reservoir and hose as metering means; the reservoir having a bottom part with a can type place-on part with an opening eccentric to the axis; a coupling part and a cover part are placed on the open part of the can, these parts are also provided with a passageway to the feedscrew eccentric to the longitudinal axis.

  14. Components of the core losses under low frequency magnetic field of the bulk Ni-Fe compacted powder material

    NASA Astrophysics Data System (ADS)

    Olekšáková, Denisa; Füzer, Ján; Kollár, Peter; Roth, S.

    2013-05-01

    Permalloy is the name of nickel-iron alloys, which after heat treatment have an initial permeability much larger than that one of pure iron and are produced usually in the form of thin sheet. Therefore it is logical to attempt to prepare such material in more "bulk" form, for example in the form of a cylinder or a ring, which would be more convenient for some industrial applications. The aim of this work was to investigate the influence of the powder size on ac and dc magnetic properties of the bulk samples prepared by a hot compaction of the powder. By analysis of the contributions of the hysteresis losses, the eddy current losses and the anomalous losses to the core losses we obtained that the fraction of all contributions strongly depends on the particle size of the powder used for preparation of the bulk material.

  15. Improved compaction of ZnO nano-powder triggered by the presence of acetate and its effect on sintering

    NASA Astrophysics Data System (ADS)

    Dargatz, Benjamin; Gonzalez-Julian, Jesus; Guillon, Olivier

    2015-04-01

    The retention of nanocrystallinity in dense ceramic materials is still a challenge, even with the application of external pressure during sintering. The compaction behavior of high purity and acetate enriched zinc oxide (ZnO) nano-powders was investigated. It was found that acetate in combination with water plays a key role during the compaction into green bodies at moderate temperatures. Application of constant pressure resulted in a homogeneous green body with superior packing density (86% of theoretical value) at moderate temperature (85 °C) in the presence of water. In contrast, no improvement in density could be achieved if pure ZnO powder was used. This compaction behavior offers superior packing of the particles, resulting in a high relative density of the consolidated compact with negligible coarsening. Dissolution accompanying creep diffusion based matter transport is suggested to strongly support reorientation of ZnO particles towards densities beyond the theoretical limit for packing of ideal monosized spheres. Finally, the sintering trajectory reveals that grain growth is retarded compared to conventional processing up to 90% of theoretical density. Moreover, nearly no radial shrinkage was observed after sinter-forging for bodies performed with this advanced processing method.

  16. Massing in high shear wet granulation can simultaneously improve powder flow and deteriorate powder compaction: a double-edged sword.

    PubMed

    Shi, Limin; Feng, Yushi; Sun, Changquan Calvin

    2011-05-18

    The influence of massing during high shear wet granulation (HSWG) process on granule properties and performance was investigated using microcrystalline cellulose (MCC). Massing time varied from 0 to 40 min while other factors were fixed. Granule physical properties, including morphology, size, porosity, and specific surface area (SSA), were characterized. Changes in powder properties were profound in the first 10 min of massing but negligible beyond 10 min. With 10 min of massing, granule tabletability decreased by 75% while flowability increased by 75%. The significantly deteriorated tabletability and improved flowability resulted from dramatic changes in granule morphology, porosity, and SSA. The results confirm that massing time is a key process parameter in HSWG, and it must be carefully evaluated and controlled during process development, scale up, and manufacturing. PMID:21443948

  17. Formation and magnetic properties of the L10 phase in bulk, powder and hot compacted Mn-Ga alloys

    NASA Astrophysics Data System (ADS)

    Mix, T.; Mller, K.-H.; Schultz, L.; Woodcock, T. G.

    2015-10-01

    The formation and stability of the L10 phase in Mn-Ga binary alloys with compositions in the range 50-75 at% Mn (in steps of 5 at%) has been studied. Of these, single-phase L10 structure was successfully produced in the 55, 60 and 65 at% Mn alloys by annealing the high temperature phases, which had been retained to room temperature following arc melting. Further annealing and thermal analysis were used to determine the phase transformation temperatures in the alloys and the results were used to guide further processing. The saturation magnetisation, Ms, and the anisotropy field, Ha, were determined in applied fields up to 14 T. For Mn55Ga45, ?0Ms=0.807 T and ?0Ha=4.4 T were observed. Mechanically milled Mn55Ga45 powder had coercivity of ?0Hc=0.393 T, which was a twentyfold increase compared to the bulk material but the magnetisation was reduced (cf. powder: ?0M5 T=0.576 T, bulk: ?0M5 T=0.780 T). Annealing the powder at 400 C led to recovery of the magnetisation but reduced the coercivity, which was still 10 times as high as the bulk value. A degree of texture of 0.45 was achieved by magnetic alignment of the powder particles, leading to a remanence of 0.526 T. Furthermore, isotropic hot compacts of powders were produced with packing density from 83% to 99%, in which the improved coercivity of the powders was partially retained.

  18. Shock compaction of rapidly solidified nickel based Mo--Al--W alloy powders with pressure up to 1. 2 mbar

    SciTech Connect

    Staudhammer, K.P.

    1988-01-01

    The alloy described in this paper is a high strength nickel alloy containing 10 wt% Mo, 6.8 wt% Al, and 6 wt% W. It cannot be easily prepared by conventional casting methods without gross segregation occurring in the form of massive dendrites. Gas atomization to form fine powders reduces the dendrite size and therefore, the segregation. The spacing of the secondary dendrite arm has been used to estimate the cooling rate of this powder. The experimental investigation of shock compaction is based in part on mach stem lens formation work. One of the fortuitous aspects of the cylindrical explosion design is its suitability as a screening tool with its very high success rate of recovery. Use of the radial implosion design has allowed for the determination of optimum pressures required for consolidation of RSR Ni--10Mo--6.8Al--6W alloy powders as a function of initial packing density. These sets of experiments are in line with previous work on other shock consolidated powders showed that an increase of initial density decreased the melt zone, and only required a slight increase in the pressure to consolidate. 4 refs., 8 figs.

  19. Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.

    PubMed

    Nouri, A; Hodgson, P D; Wen, C E

    2010-04-01

    The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product. PMID:19815096

  20. A homogenization approach to the yield strength of spherical powder compacts

    NASA Astrophysics Data System (ADS)

    Benabbes, A.; Siad, L.; Dormieux, L.; Liu, W. K.

    2010-06-01

    Optimal external estimates of the macroscopic strength criteria of a hexagonal array of identical spherical grains, under isostatic and closed die compaction, have been obtained through the use of the kinematic approach of the yield design homogenization method. Two appropriate unit cells, one for each stage compaction (I and II), and eight relevant failure mechanisms are considered. For comparison purposes, numerical simulations based on FEA similar to those of Ogbana and Fleck [1] have also been carried out. The shapes and sizes of the macroscopic yield surfaces are determined at various stages of compaction and it has been found in particular that they depend upon the loading history as well as the relative density of the compact.

  1. High strength-high conductivity Cu-Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, J.D.; Spitzig, W.A.; Gibson, E.D.; Anderson, I.E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an ''in-situ'' Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite. 5 figures.

  2. High strength-high conductivity Cu--Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, John D.; Spitzig, William A.; Gibson, Edwin D.; Anderson, Iver E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an "in-situ" Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite.

  3. Cryo-SEM method for the observation of entrapped bubbles and degree of water filling in large wet powder compacts.

    PubMed

    Mouzon, J; Bhuiyan, I U; Forsmo, S P E; Hedlund, J

    2011-05-01

    There are generally two problems associated with cryogenic scanning electron microscopy (cryo-SEM) observations of large wet powder compacts. First, because water cannot be vitrified in such samples, formation of artefacts is unavoidable. Second, large frozen samples are difficult to fracture but also to machine into regular pieces which fit in standard holders, especially if made of hard materials like ceramics. In this article, we first describe a simple method for planning hard cryo-samples and a low-cost technique for cryo-fracture and transfer of large specimens. Subsequently, after applying the entire procedure to green pellets of iron ore produced by balling, we compare the influence of plunge- and unidirectional freezing on large entrapped bubbles throughout the samples as well as the degree of water filling at the outer surface of the pellets. By carefully investigating the presence of artefacts in large areas of the samples and by controlling the orientation of the sample during freezing and preparation, we demonstrate that unidirectional freezing enables the observation of large entrapped bubbles with minimum formation of artefacts, whereas plunge freezing is preferable for the characterization of the degree of water filling at the outer surface of wet powder compacts. The minimum formation of artefacts was due to the high packing density of the iron ore particles in the matrix. PMID:21118249

  4. Fabrication of fully dense nanostructured MnBi magnet by hot compaction of cryo-milled powders

    NASA Astrophysics Data System (ADS)

    Hadjipanayis, George; Neelam, Venkata; Gabay, Alex; Li, Wang

    2013-03-01

    Recently, rare-earth-free permanent magnets (REFPMs) have attracted much attention globally owing to rare-earth metal crisis and high cost. Among the REFPMs, MnBi is a potential candidate due to its unusual large magnetocrystalline anisotropy (K ~ 107 erg/cc) and positive temperature of coefficient of coercivity. In this work, we report for the first time a novel processing method that combines the cryo-milling with hot compaction to produce fully dense bulk nanostructured MnBi magnet. The effect of cryo-milling on particle size, phase formation, and magnetic properties of MnBi has been studied in detail. Also, the microstructural and magnetic properties of bulk nanostructured MnBi magnet were investigated. Adoption of cryo-milling results in nanocrystalline powders with particle size of 400-500 nm. Large coercivity (Hc) values of 18.5 kOe, and 12.9 kOe were obtained in cryo-milled powders and hot compacted magnet respectively. The MnBi magnet shows a large positive temperature coefficient of Hc and the Hc reaches a value of more than 30 kOe above 450 K. The work was supported by Siemens.

  5. Processing and properties of FeAl sheets obtained by roll compaction and sintering of water atomized powder

    SciTech Connect

    Deevi, S.C.; Hajaligol, M.R.; Sikka, V.K.; McKernon, J.; Scorey, C.R.

    1999-07-01

    The low ductilities of FeAl alloys led us to explore powder metallurgical processing technology to obtain sheets of 0.2mm thickness as opposed to manufacturing processes based on hot rolling of cast FeAl alloys. In their approach, water atomized FeAl powders were roll compacted to 0.66mm with a polymeric binder using two counter rotating rolls to a green density of 3.1 g/cc. Roll compacted green sheets were then de-bindered in nitrogen in the temperature range of 300 to 600 C for several hours prior to sintering the sheets in vacuum. Sintered sheets were rolled down from 0.66 to 0.20 mm in three different stages resulting in a total reduction of 69%. Vacuum annealing of the sheets was carried out between each stage of the reduction process to eliminate edge cracking associated with the work hardening of the FeAl. The properties of the FeAl sheets depend on the Al content, annealing temperature and time in a vacuum furnace. The fine microstructure of FeAl sheets led to tensile elongations of 4 to 6%. The sheets are formable at room temperature, and possess excellent mechanical properties both at room and high temperatures.

  6. Microwave Heating and Pre-sintering of Copper Powder Metal Compacts in Separated Electric and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Martin, Kelly; Johnson, Earnie; Ma, Junkun; Miskovsky, Nicholas; Weisel, Gary; Weiss, Brock; Zimmerman, Darin

    2006-03-01

    We present results of microwave heating and pre-sintering of pure copper metal powder compacts. Using a 2.45GHz, WR284 microwave system operating in TE102 single mode resonance, we have systematically studied the microwave heating and pre-sintering behavior of various copper powder metal compacts as a function of particle size and green density. Cylindrical samples (0.25in by 0.25in) were positioned in either the magnetic-- or electric--field antinode, allowing the study of the separate effects of the two fields. The results show significant differences in heating rates and sample microstructure (SEM) even when average sample temperatures are below half the melting point of bulk copper. Numerical simulations of the absorption and heating have been developed to check the consistency of the experimental results. We acknowledge the additional work of undergraduate students John Diehl, John Rea, Charles Smith, and Devin Spratt, who assisted in the setup of experimental apparatus, sample preparation, and data acquisition.

  7. Wear-resistant coatings produced by shock-wave compaction of powders

    SciTech Connect

    Kiiski, A.A.; Ruuskanen, P.R.; Rubin, J.B.

    1996-08-01

    Wear-resistant metal-matrix composite coatings with a thickness of 1.5 mm were fabricated on low-alloy steel substrates by explosively generated shock waves. Starting materials were equivolume mixtures of WC or Cr{sub 3}C{sub 2} powder mixed with either titanium or cobalt powder as a binder phase. Three different planar geometries were used, with powder layer thicknesses varying from 1 to 3 mm. Microstructural examination showed that fully dense, crack-free coatings could be produced with a uniform distribution of the carbides within the metallic binder phase. Shear strengths in excess of 40 MPa were measured for coatings composed of equivolume powder mixtures of (Cr{sub 3}C{sub 2} + Ti) and (WC + Ti). The weight loss of a coating produced from an equivolume (WC + Co) powder mixture measured from a two-body abrasive wear test was significantly lower than that measured for a wear-resistant tool steel used as a reference material.

  8. Piezochromic Phenomena of Nanometer Voids Formed by Mono-Dispersed Nanometer Powders Compacting Process

    PubMed Central

    Su, Lihong; Wan, Caixia; Zhou, Jianren; Wang, Yiguang; Wang, Liang; Ai, Yanling; Zhao, Xu

    2013-01-01

    Piezochromism describes a tendency of certain materials changing colors when they are subjected to various pressure levels. It occurs particularly in some polymers or inorganic materials, such as in palladium complexes. However, piezochromism is generally believed to work at high pressure range of 0.1–10 GPa. This research work focused on unique piezochromism responses of the nanometer voids formed by the 5–20 nm inorganic ISOH nanometer powders. It was discovered that microstructures of the nanometer voids could change color at very low pressures of only 0.002–0.01 GPa; its sensitivity to pressure was increased by tens of times. It is believed that the uniform microstructures of nanometer powders contributed to the material's high sensitivity of piezochromic phenomena. One factor which quantum optical change caused by nanometer voids affected the quantum confinement effect; another is surface Plasmon Resonance of great difference dielectric property between conductive ITO powder and insulation hydroxide. PMID:24115999

  9. Piezochromic phenomena of nanometer voids formed by mono-dispersed nanometer powders compacting process.

    PubMed

    Su, Lihong; Wan, Caixia; Zhou, Jianren; Wang, Yiguang; Wang, Liang; Ai, Yanling; Zhao, Xu

    2013-01-01

    Piezochromism describes a tendency of certain materials changing colors when they are subjected to various pressure levels. It occurs particularly in some polymers or inorganic materials, such as in palladium complexes. However, piezochromism is generally believed to work at high pressure range of 0.1-10 GPa. This research work focused on unique piezochromism responses of the nanometer voids formed by the 5-20 nm inorganic ISOH nanometer powders. It was discovered that microstructures of the nanometer voids could change color at very low pressures of only 0.002-0.01 GPa; its sensitivity to pressure was increased by tens of times. It is believed that the uniform microstructures of nanometer powders contributed to the material's high sensitivity of piezochromic phenomena. One factor which quantum optical change caused by nanometer voids affected the quantum confinement effect; another is surface Plasmon Resonance of great difference dielectric property between conductive ITO powder and insulation hydroxide. PMID:24115999

  10. Use of limestone powder during incorporation of Pb-containing cathode ray tube waste in self-compacting concrete.

    PubMed

    Sua-iam, Gritsada; Makul, Natt

    2013-10-15

    For several decades, cathode ray tubes (CRTs) were the primary display component of televisions and computers. The CRT glass envelope contains sufficient levels of lead oxide (PbO) to be considered hazardous, and there is a need for effective methods of permanently encapsulating this material during waste disposal. We examined the effect of adding limestone powder (LS) on the fresh and cured properties of self-compacting concrete (SCC) mixtures containing waste CRT glass. The SCC mixtures were prepared using Type 1 Portland cement at a constant cement content of 600 kg/m(3) and a water-to-cement ratio (w/c) of 0.38. CRT glass waste cullet was blended with river sand in proportions of 20 or 40% by weight. To suppress potential viscosity effects limestone powder was added at levels of 5, 10, or 15% by weight. The slump flow time, slump flow diameter, V-funnel flow time, Marsh cone flow time, and setting time of the fresh concrete were tested, as well as the compressive strength and ultrasonic pulse velocity of the hardened concrete. Addition of limestone powder improved the fresh and hardened properties. Pb leaching levels from the cured concrete were within US EPA allowable limits. PMID:23892134

  11. Interaction of Tournemire argillite (Aveyron, France) with hyperalkaline fluids: Batch experiments performed with powdered and/or compact materials

    NASA Astrophysics Data System (ADS)

    Devol-Brown, I.; Tinseau, E.; Bartier, D.; Mifsud, A.; Stammose, D.

    Argillaceous rocks and concrete matrix are considered as potential host rocks and engineered barrier, respectively for radioactive waste repositories. The concrete matrix could react with the groundwater of the geological site, inducing a drastic change in its chemical composition and pH. Consequently, the physico-chemical properties of the rock in contact with this hyperalkaline fluid may be modified. Therefore, an experimental programme has been developed for examining the physico-chemical changes of claystone in contact with alkaline fluids: batch experiments undertaken as a preliminary step followed by diffusion and percolation experiments in order to describe and to assess the physico-chemical phenomena observed under repository conditions. The first series of batch experiments are carried out in order to study the degradation of the Tournemire argillite properties caused by a fluid resulting from a contact with fresh concrete, considered as the most aggressive in relation to its hyper alkaline pH (≈13). Thus, the influence of several parameters is tested, such as liquid/rock ratio (L/R 3-30 g/g), contact time (1-3 months), temperature (25-70 °C) and oxygen concentration. To compare the effect of the concrete maturity on the argillite physico-chemical damage, the second series of batch experiments are performed with a fluid resulting from a contact with moderately degraded concrete. Experiments are carried out on powdered and compact samples in order to identify structural and geochemical modifications. Before and after contact with simplified concrete fluids, powdered solids were mainly characterised by XRD (with measurements of specific surface area and SEM observations for a selection of samples) whereas compact materials were only observed by SEM. The chemical composition of the recovered solutions was also determined for their major anions and cations with their carbon content and pH values. Interpretations are based on solid analyses and aqueous chemistry. The comparison of results obtained with powdered and compact solids is only feasible for short time experiments. Aqueous chemistry and solid analyses indicate the dissolution of pyrite, dolomite and organic carbon with the precipitation of calcite. Precipitations of zeolites and K-feldspars occur sometimes and are only evidenced by SEM analyses. Nevertheless, silicates dissolution or precipitation is unclear through XRD analyses. Experimental conditions influence widely the intensity/nature of processes and prevent the transposition of data obtained in given conditions to other ones.

  12. Improving sintered NdFeB permanent magnets by powder compaction in a 9 T superconducting solenoid

    NASA Astrophysics Data System (ADS)

    Mulcahy, T. M.; Hull, J. R.; Rozendaal, E.; Wise, J. H.; Turner, L. R.

    2003-05-01

    Commercial-grade magnet powder (Magnequench UG) was axial die pressed in the 76.2 mm warm bore of a 9 T superconducting solenoid. Otherwise, processing was performed as part of normal factory operations. This pressing was done to improve the alignment of the anisotropic single-crystal particles of the compact and, thus, the remanent magnetization of the sintered cylindrical permanent magnets (12.7 mm diameter). Although the press was operated in batch mode for this proof-of-concept study, its design enables automated production. Improvements of up to 8% in magnetization and 16% in energy products were obtained, as the alignment field H was increased above the 2 T maximum field of electromagnets used in industry. The greatest improvements were obtained for magnets with the smallest length-to-diameter ratios, L/D<0.5. The production of quality magnets in this near-final-shape size range is currently being pursued by industry to eliminate expensive machining steps. To understand the potential for 2-8 T alignment fields to overcome the distortions created in the otherwise uniform field by the self-field of short compacts, electromagnetic code (Opera) calculations were made. A simple material model was used to predict the distortions. The trends in the predicted field-line inclinations, with L/D and H, compare to trends in the improvement of the magnetic properties.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  15. VIBRATION COMPACTION

    DOEpatents

    Hauth, J.J.

    1962-07-01

    A method of compacting a powder in a metal container is described including the steps of vibrating the container at above and below the resonant frequency and also sweeping the frequency of vibration across the resonant frequency several times thereby following the change in resonant frequency caused by compaction of the powder. (AEC)

  16. Developments in Die Pressing Strategies for Low-Cost Titanium Powders

    SciTech Connect

    Hovanski, Yuri; Weil, K. Scott; Lavender, Curt A.

    2009-05-01

    Recent developments in the production of low-cost titanium powders have rejuvenated interest in manufacturing titanium powder metallurgy components by direct press and sinter techniques. However excessive friction typically observed during titanium powder pressing operations leads to numerous problems ranging from non-homogeneous green densities of the compacted powder to excessive part ejection forces and reduced die life due to wear and galling. An instrumented double-acting die press was developed to both investigate the mechanics of titanium powder pressing (particularly for the new low-cost powder morphologies) and to screen potential lubricants that could reduce frictional effects. As will be discussed, the instrument was used to determine friction coefficients and to evaluate a number of candidate lubricants. These results were then used to optimize the lubricant system to reduce die-wall stresses and improve part density uniformity.

  17. NON-MELT PROCESSING OF "LOW-COST", ARMSTRONG TITANIUM AND TITANIUM ALLOY POWDERS

    SciTech Connect

    Peter, William H; Blue, Craig A; Clive, Scorey; Ernst, Bill; McKernan, John; Kiggans, Jim; Rivard, John D; Yu, Dr. Charlie

    2007-01-01

    In the last decade, a considerable effort has been made to develop new methods for producing low cost titanium and titanium powders. The Armstrong process is a new method of producing titanium powder via reducing TiCl4 vapor in molten sodium. The process is scalable, and can be used to produce pre-alloyed powders. Non-melt processing and powder metallurgy approaches are economically viable with the commercially pure powders. In this investigation, several non-melt processing technologies, including vacuum hot pressing, extrusion, roll compaction, and forging techniques, will be evaluated using the Armstrong titanium powders. The metallurgical, chemical, and mechanical properties of the processed titanium samples will be discussed.

  18. Diffusion and swelling measurements in pharmaceutical powder compacts using terahertz pulsed imaging.

    PubMed

    Yassin, Samy; Su, Ke; Lin, Hungyen; Gladden, Lynn F; Zeitler, J Axel

    2015-05-01

    Tablet dissolution is strongly affected by swelling and solvent penetration into its matrix. A terahertz-pulsed imaging (TPI) technique, in reflection mode, is introduced as a new tool to measure one-dimensional swelling and solvent ingress in flat-faced pharmaceutical compacts exposed to dissolution medium from one face of the tablet. The technique was demonstrated on three tableting excipients: hydroxypropylmethyl cellulose (HPMC), Eudragit RSPO, and lactose. Upon contact with water, HPMC initially shrinks to up to 13% of its original thickness before undergoing expansion. HPMC and lactose were shown to expand to up to 20% and 47% of their original size in 24 h and 13 min, respectively, whereas Eudragit does not undergo dimensional change. The TPI technique was used to measure the ingress of water into HPMC tablets over a period of 24 h and it was observed that water penetrates into the tablet by anomalous diffusion. X-ray microtomography was used to measure tablet porosity alongside helium pycnometry and was linked to the results obtained by TPI. Our results highlight a new application area of TPI in the pharmaceutical sciences that could be of interest in the development and quality testing of advanced drug delivery systems as well as immediate release formulations. PMID:25645509

  19. Diffusion and Swelling Measurements in Pharmaceutical Powder Compacts Using Terahertz Pulsed Imaging

    PubMed Central

    Yassin, Samy; Su, Ke; Lin, Hungyen; Gladden, Lynn F; Zeitler, J Axel

    2015-01-01

    Tablet dissolution is strongly affected by swelling and solvent penetration into its matrix. A terahertz-pulsed imaging (TPI) technique, in reflection mode, is introduced as a new tool to measure one-dimensional swelling and solvent ingress in flat-faced pharmaceutical compacts exposed to dissolution medium from one face of the tablet. The technique was demonstrated on three tableting excipients: hydroxypropylmethyl cellulose (HPMC), Eudragit RSPO, and lactose. Upon contact with water, HPMC initially shrinks to up to 13% of its original thickness before undergoing expansion. HPMC and lactose were shown to expand to up to 20% and 47% of their original size in 24 h and 13 min, respectively, whereas Eudragit does not undergo dimensional change. The TPI technique was used to measure the ingress of water into HPMC tablets over a period of 24 h and it was observed that water penetrates into the tablet by anomalous diffusion. X-ray microtomography was used to measure tablet porosity alongside helium pycnometry and was linked to the results obtained by TPI. Our results highlight a new application area of TPI in the pharmaceutical sciences that could be of interest in the development and quality testing of advanced drug delivery systems as well as immediate release formulations. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1658–1667, 2015 PMID:25645509

  20. Tungsten and tungsten-alloy powder metallurgy: Powder production and applications-excluding lamps. November 1971-July 1989 (Citations from the US Patent data base). Report for November 1971-July 1989

    SciTech Connect

    Not Available

    1989-10-01

    This bibliography contains citations of selected patents concerning the preparation of metallic and ceramic powders of tungsten and tungsten alloys including various applications of these materials. The hydrogen reduction of tungsten compounds together with alloying-element compounds produce forms with characteristics of high density, hardness, wear resistance, high melting points, and abrasiveness. Topics include production of various cathodes, heaters, filament wires, electrical contacts, acoustic absorbers, high-density sheets and coatings, hard penetrators, and tungsten carbide and metallized ceramics. Tungsten halogen lamps are examined in a separate bibliography. (Contains 60 citations fully indexed and including a title list.)

  1. Metallurgy and properties of plasma spray formed materials

    NASA Technical Reports Server (NTRS)

    Mckechnie, T. N.; Liaw, Y. K.; Zimmerman, F. R.; Poorman, R. M.

    1992-01-01

    Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure.

  2. The Role of Oxygen Transfer in Sintering of Low Alloy Steel Powder Compacts: A Review of the "Internal Getter" Effect

    NASA Astrophysics Data System (ADS)

    Gierl-Mayer, Christian; de Oro Calderon, Raquel; Danninger, Herbert

    2016-03-01

    The chemical aspects of sintering have to be considered, in particular the role of oxygen. For sintered alloy steels used for highly stressed components, traditional alloy elements have been Cu, Ni and Mo, which in their oxygen affinity are very similar to the base constituent iron. Advanced alloying systems however contain Cr, Mn and/or Si. In the present study it is shown that one of the principal aspects of sintering to be considered is oxygen transfer from the base iron oxides to the alloy elements, which then form oxides that are more difficult to reduce. This process, defined as "internal gettering", occurs both in mixed powder compacts and in prealloyed materials, although through different mechanisms. The effect can at least be alleviated by presintering in H2 in the 400°C range, part of the oxygen being removed as H2O before internal gettering becomes kinetically effective. However, in industrial practice, this collides with delubricaton. Furthermore for both alloy variants high temperature sintering is advantageous because it enhances reduction of the more stable oxides, thus eliminating the effects of internal gettering.

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

    NASA Astrophysics Data System (ADS)

    Yang, Fei; Gabbitas, Brian

    2015-03-01

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

  4. Superplasticity in a powder metallurgy magnesium composite

    SciTech Connect

    Nieh, T.G.; Wadsworth, J.

    1995-04-15

    Metal-matrix composites (MMC) have great potential to be used in high-performance aerospace and automobile applications. It is important, therefore, to develop secondary processing for MMCs which can effectively produce complex engineering components directly from wrought products. Many studies now have been performed that demonstrate superplasticity can be developed in MMCs. Superplasticity has been reported in some Mg alloys, including ZK60, AZ31, AZ61, and Mg-Li alloys. But, none of these alloys showed superplasticity at high strain rates. Although HSRS has been extensively demonstrated in Al-base MMCs, both in PM and IM products, neither conventional superplasticity nor HSRS has yet been shown in any Mg-base composite. The purpose of this paper is to present, for the first time, the observation of HSRS in a 17 vol% SiC particulate-reinforced ZK60A magnesium composite (ZK60/SiC/17p).

  5. Special Features of the Mechanical Characteristics of Al-Al2O3 Composites Produced By Explosive Compaction of Powders Under Shock-Wave Deformation

    NASA Astrophysics Data System (ADS)

    Zhukov, I. A.; Garkushin, G. V.; Vorozhtsov, S. A.; Khrustalyov, A. P.; Razorenov, S. V.; Kvetinskaya, A. V.; Promakhov, V. V.; Zhukov, A. S.

    2016-01-01

    The results obtained from investigations into the special features inherent in the mechanical characteristics (Hugoniot elastic limit and spall strength) observed under shock-wave loading of Al-Al2O3 composite samples produced by an explosive powder compaction technique are presented. Embedding 10 wt.% of aluminum oxide in the aluminum matrix has been found to increase the Hugoniot elastic limit as opposed to the commercialgrade AD1(Al 1013) aluminum alloy.

  6. A novel microwave sensor for real-time online monitoring of roll compacts of pharmaceutical powders online--a comparative case study with NIR.

    PubMed

    Gupta, Anshu; Austin, John; Davis, Sierra; Harris, Michael; Reklaitis, Gintaras

    2015-05-01

    Control of particulate processes is hard to achieve because of the ease with which powders tend to segregate. Thus, proper sensing methods must be employed to ensure content uniformity during operation. The role of sensing schemes becomes even more critical while operating the process continuously as measurements are essential for implementation of feedback control (Austin et al. 2013. J Pharm Sci 102(6):1895-1904; Austin et al. 2014. Anal Chim Acta 819:82-93). A microwave sensor was developed and shown to be effective in online measurement of active pharmaceutical ingredient (API) concentration in a powder blend. During powder transport and hopper storage before processing, powder blends may segregate and cause quality deviations in the subsequent tableting operation. Therefore, it is critical to know the API concentration in the ribbons as the content uniformity is fixed once the ribbon is processed. In this study, a novel microwave sensor was developed that could provide measurement of a roller compacted ribbon's API concentration online, along with its density and moisture content. The results indicate that this microwave sensor is capable of increased accuracy compared with a commercially available near-IR probe for the determination of content uniformity and density in roller compacted ribbons online. PMID:25754185

  7. Influence of Powder Particle Size on the Compaction Behavior and Mechanical Properties of a High-Alloy Austenitic CrMnNi TRIP Steel During Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Decker, S.; Martin, S.; Krüger, L.

    2016-01-01

    In this study, varying powder particle size fractions (<25, 25 to 45, 45 to 63 µm) of a TRIP steel powder were compacted by spark plasma sintering (SPS). Densification initiated at a slightly lower temperature with decreasing particle size due to increasing green density. With decreasing powder particle size fraction, the as-sintered materials exhibited smaller grain sizes. Compression tests revealed a slight decrease of the compressive yield strength with increasing particle size and, accordingly, larger grain size. A few large deformation bands formed in bigger grains, while many thin deformation bands were formed in smaller grains. α'-Martensite nuclei formed successively inside the deformation bands, reducing the mean free path of (partial) dislocation slip. Due to the size of the deformation bands, α'-martensite formation started at lower strains with increasing particle size. When α'-martensite formation was initiated, work hardening was influenced more by α'-martensite formation than by the grain size of the steel matrix. Hence, work hardening increased with increasing particle size.

  8. Power metallurgy approaches to high temperature components for gas turbine engines

    NASA Technical Reports Server (NTRS)

    Probst, H. B.

    1974-01-01

    Work conducted by NASA and NASA contractors on prealloyed superalloy powders and materials strengthened by oxide dispersion is reviewed. Fabrication, tensile strength, superplasticity, grain growth control, stress rupture life, and grain-size and dispersion-level effects are covered. Distinct strength advantages of powder metallurgy superalloys over conventional wrought alloys are noted.

  9. Steric stabilization of nonaqueous silicon slips. I - Control of particle agglomeration and packing. II - Pressure casting of powder compacts

    NASA Technical Reports Server (NTRS)

    Kerkar, Awdhoot V.; Henderson, Robert J. M.; Feke, Donald L.

    1990-01-01

    The application of steric stabilization to control particle agglomeration and packing of silicon powder in benzene and trichloroethylene is reported. The results provide useful guidelines for controlling unfavorable particle-particle interactions during nonaqueous processing of silicon-based ceramic materials. The application of steric stabilization to the control and improvement of green processing of nonaqueous silicon slips in pressure consolidation is also demonstrated.

  10. Metallurgy Beyond Iron

    NASA Astrophysics Data System (ADS)

    Gallino, Isabella; Busch, Ralf

    2009-08-01

    Metallurgy is one of the oldest sciences. Its history can be traced back to 6000 BCE with the discovery of Gold, and each new discovery - Copper, Silver, Lead, Tin, Iron and Mercury - marked the beginning of a new era of civilization. Currently there are 86 known metals, but until the end of the 17th century, only 12 of these were known. Steel (Fe-C alloy) was discovered in the 11th century BCE; however, it took until 1709 CE before we mastered the smelting of pig-iron by using coke instead of charcoal and started the industrial revolution. The metallurgy of nowadays is mainly about discovering better materials with superior properties to fulfil the increasing demand of the global market. Promising are the Glassy Metals or Bulk Metallic Glasses (BMGs) - discovered at first in the late 50s at the California Institute of Technology - which are several times stronger than the best industrial steels and 10-times springier. The unusual structure that lacks crystalline grains makes BMGs so promising. They have a liquid-like structure that means they melt at lower temperatures, can be moulded nearly as easily as plastics, and can be shaped into features just 10 nm across. The best BMG formers are based on Zr, Pd, Pt, Ca, Au and, recently discovered, also Fe. They have typically three to five components with large atomic size mismatch and a composition close to a deep eutectic. Packing in such liquids is very dense, with a low content of free volume, resulting in viscosities that are several orders of magnitude higher than in pure metal melts.

  11. Enery Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications

    SciTech Connect

    Thomas Zwitter; Phillip Nash; Xiaoyan Xu; Chadwick Johnson

    2011-03-31

    This is the final technical report for the Department of Energy NETL project NT01931 Energy Efficient Press and Sinter of Titanium Powder for Low-Cost Components in Vehicle Applications. Titanium has been identified as one of the key materials with the required strength that can reduce the weight of automotive components and thereby reduce fuel consumption. Working with newly developed sources of titanium powder, Webster-Hoff will develop the processing technology to manufacture low cost vehicle components using the single press/single sinter techniques developed for iron based powder metallurgy today. Working with an automotive or truck manufacturer, Webster-Hoff will demonstrate the feasibility of manufacturing a press and sinter titanium component for a vehicle application. The project objective is two-fold, to develop the technology for manufacturing press and sinter titanium components, and to demonstrate the feasibility of producing a titanium component for a vehicle application. The lowest cost method for converting metal powder into a net shape part is the Powder Metallurgy Press and Sinter Process. The method involves compaction of the metal powder in a tool (usually a die and punches, upper and lower) at a high pressure (up to 60 TSI or 827 MPa) to form a green compact with the net shape of the final component. The powder in the green compact is held together by the compression bonds between the powder particles. The sinter process then converts the green compact to a metallurgically bonded net shape part through the process of solid state diffusion. The goal of this project is to expand the understanding and application of press and sinter technology to Titanium Powder applications, developing techniques to manufacture net shape Titanium components via the press and sinter process. In addition, working with a vehicle manufacturer, demonstrate the feasibility of producing a titanium component for a vehicle. This is not a research program, but rather a project to develop a process for press and sinter of net shape Titanium components. All of these project objectives have been successfully completed.

  12. Use of Cation Exchange Resins for Production of U{sub 3}O{sub 8} Suitable for the Al-U{sub 3}O{sub 8} Powder Metallurgy Process

    SciTech Connect

    Mosley, W.C.

    2001-09-17

    This report describes the production of U{sub 3}O{sub 8} powders from three types of cation exchange resins: Dowex 50W, a strong acid, sulfonate resin; AG MP-50, a macroporous form of sulfonate resin; and Bio-Rex 70, a weak acid, carboxylic resin.

  13. The use of net analyte signal orthogonalization in the separation of multi-component diffraction patterns obtained from X-ray powder diffraction of intact compacts.

    PubMed

    Moore, Michael D; Cogdill, Robert P; Short, Steven M; Hair, Colleen R; Wildfong, Peter L D

    2008-06-01

    X-ray powder diffraction (XRPD) analysis of intact multi-component consolidated mixtures has significant potential owing to the ability to non-destructively quantify and discriminate between solid phases in composite bodies with minimal sample preparation. There are, however, limitations to the quantitative power using traditional univariate methods on diffraction data containing features from all components in the system. The ability to separate multi-component diffraction data into patterns representing single constituents allows both composition as well as physical phenomena associated with the individual components of complex systems to be probed. Intact, four-component compacts, consisting of two crystalline and two amorphous constituents were analyzed using XRPD configured in both traditional Bragg-Brentano reflectance geometry and parallel-beam transmission geometry. Two empirical, model-based methods consisting of a multiple step net analyte signal (NAS) orthogonalization are presented as ways to separate multi-component XRPD patterns into single constituent patterns. Multivariate figures of merit (FOM) were calculated for each of the isolated constituents to compare method-specific parameters such as sensitivity, selectivity, and signal-to-noise, enabling quantitative comparisons between the two modes of XRPD analysis. PMID:18294800

  14. Combustibility of titanium powders

    NASA Technical Reports Server (NTRS)

    Popov, Ye. I.; Poyarkov, V. G.; Finayev, Yu. A.

    1989-01-01

    The combustion of compact samples was studied; the mechanism of autoignition is defined. Several studies are made of the combustibility of titanium using 50 samples. The data provide a clear idea of the combustibility of titanium powders.

  15. Recent trends in extractive metallurgy

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Metallurgists and solution geochemists are joining forces to develop processes for extraction of metals from low-grade ores. The processes, which come under the name hydrometallurgy, include several new applications of solvent extraction techniques. Aqueous solutions are employed, leaching metals from ores, mine waste dumps, and even from deposits still in the ground. It was notable, for example, that Chemical and Engineering News (Feb. 8, 1982) recently featured the subject of hydrometallurgy in a special report. They noted that ‘recovering metals by use of aqueous solutions at relatively low temperatures increasingly is competing with dry, high-temperature pyrometallurgical methods.’ The relatively new techniques have caused a revolution, of sorts, in engineering programs of university metallurgy departments. The challenge of developing selective metal dissolution processes is drawing upon the best national talent in the fields of solution geochemistry and metallurgy.

  16. METHOD OF FORMING ELONGATED COMPACTS

    DOEpatents

    Larson, H.F.

    1959-05-01

    A powder compacting procedure and apparatus which produces elongated compacts of Be is described. The powdered metal is placed in a thin metal tube which is chemically compatible to lubricant, powder, atmosphere, and die material and will undergo a high degree of plastic deformation and have intermediate hardness. The tube is capped and placed in the die, and punches are applied to the ends. During the compacting stroke the powder seizes the tube and a thickening and shortening of the tube occurs. The tube is easily removed from the die, split, and peeled from the compact. (T.R.H.)

  17. Sintering titanium powders

    SciTech Connect

    Gerdemann, Stephen J.; Alman, David E.

    2005-09-01

    Recently, there has been renewed interest in low-cost titanium. Near-net-shape powder metallurgy offers the potential of manufacturing titanium articles without costly and difficult forming and machining operations; hence, processing methods such as conventional press-and-sinter, powder forging and powder injection molding are of interest. The sintering behavior of a variety of commercial and experimental titanium powders was studied. Commercial powders were acquired that were produced different routes: (i) sponge fines from the primary titanium processing; (ii) via the hydride-dehydride process; and (iii) gas atomization. The influence of vacuum sintering time (0.5 to 32 hrs) and temperature (1200, 1275 or 1350°C) on the microstructure (porosity present) of cold pressed powders was studied. The results are discussed in terms of the difference in powder characteristics, with the aim of identify the characteristics required for full density via press-and-sinter processing. Near-net-shape tensile bars were consolidated via cold pressed and sintered. After sintering, a sub-set of the tensile bars was hot-isostatic pressed (HIPed). The microstructure and properties of the bars were compared in the sintered and HIPed conditions.

  18. The imaging performance of compact Lu{sub 2}O{sub 3}:Eu powdered phosphor screens: Monte Carlo simulation for applications in mammography

    SciTech Connect

    Liaparinos, P. F.; Kandarakis, I. S.

    2009-06-15

    In medical mammographic imaging systems, one type of detector configuration, often referred to as indirect detectors, is based on a scintillator layer (phosphor screen) that converts the x-ray radiation into optical signal. The indirect detector performance may be optimized either by improving the structural parameters of the screen or by employing new phosphor materials with improved physical characteristics (e.g., x-ray absorption efficiency, intrinsic conversion efficiency, emitted light spectrum). Lu{sub 2}O{sub 3}:Eu is a relatively new phosphor material that exhibits improved scintillating properties indicating a promising material for mammographic applications. In this article, a custom validated Monte Carlo program was used in order to examine the performance of compact Lu{sub 2}O{sub 3}:Eu powdered phosphor screens under diagnostic mammography conditions (x-ray spectra: 28 kV Mo, 0.030 mm Mo and 32 kV W, 0.050 mm Rh). Lu{sub 2}O{sub 3}:Eu screens of coating weight in the range between 20 and 40 mg/cm{sup 2} were examined. The Monte Carlo code was based on a model using Mie-scattering theory for the description of light propagation within the phosphor. The overall performance of Lu{sub 2}O{sub 3}:Eu powdered phosphor screens was investigated in terms of the (i) quantum detection efficiency, (ii) luminescence efficiency, (iii) compatibility with optical sensors, (iv) modulation transfer function, (v) the Swank factor, and (vi) zero-frequency detective quantum efficiency. Results were compared to the traditional rare-earth Gd{sub 2}O{sub 2}S:Tb phosphor material. The increased packing density and therefore the light extinction properties of Lu{sub 2}O{sub 3}:Eu phosphor were found to improve the x-ray absorption (approximately up to 21% and 16% at 40 mg/cm{sup 2} for Mo and W x-ray spectra, respectively), the spatial resolution (approximately 2.6 and 2.4 cycles/mm at 40 mg/cm{sup 2} for Mo and W x-ray spectra, respectively), as well as the zero-frequency detective quantum efficiency (approximately up to 8% and 18% at 20 mg/cm{sup 2} for Mo and W x-ray spectra, respectively) of the screens in comparison to the Gd{sub 2}O{sub 2}S:Tb screens. Data obtained by the simulations indicate that certain optical properties of Lu{sub 2}O{sub 3}:Eu make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray mammography imagers.

  19. Silicon solar cells: Physical metallurgy principles

    NASA Astrophysics Data System (ADS)

    Mauk, Michael G.

    2003-05-01

    This article reviews the physical metallurgy aspects of silicon solar cells. The production of silicon solar cells relies on principles of thermochemical extractive metallurgy, phase equilibria, solidification, and kinetics. The issues related to these processes and their impact on solar cell performance and cost are discussed.

  20. Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy

    NASA Astrophysics Data System (ADS)

    Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

    2014-09-01

    Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

  1. The Rules of Ferrous Metallurgy

    PubMed Central

    2010-01-01

    The ways in which the sciences have been delineated and categorized throughout history provide insights into the formation, stabilization, and establishment of scientific systems of knowledge. The Dresdener school’s approach for explaining and categorizing the genesis of the engineering disciplines is still valid, but needs to be complemented by further-reaching methodological and theoretical reflections. Pierre Bourdieu’s theory of social practice is applied to the question of how individual agents succeed in influencing decisively a discipline’s changing object orientation, institutionalisation and self-reproduction. Through the accumulation of social, cultural and economic capital, they succeed in realising their own organisational ideas and scientific programs. Key concepts for the analysis include the struggle for power and resources, monopolies of interpretation, and the degree of autonomy. A case study from the Aachener Technische Hochschule shows that the consolidation of ferrous metallurgy can be conceived as a symbolical struggle between Fritz Wüst, professor for ferrous metallurgy, and the German Iron and Steel Institute, leading to a construction of a system of differences in which scientists accepted being scientists rather than entrepreneurs, and entrepreneurs accepted becoming entrepreneurs and renounced science.

  2. Methods of increasing the erosion resistance of powder metallurgy steel

    SciTech Connect

    Kulu, P.A.

    1987-09-01

    The authors comparatively assess the effects of a variety of surface hardening methods--including carburizing, boriding, chromizing, and carbochromizing, as well as the flame, plasma arc, and detonation spraying of nickel and molybdenum coatings--on the wear, corrosion resistance, and pore structure of steel 45, and outline testing procedures used to arrive at their results.

  3. Aluminum base alloy powder metallurgy process and product

    NASA Technical Reports Server (NTRS)

    Paris, Henry G. (Inventor)

    1986-01-01

    A metallurgical method including cooling molten aluminum particles and consolidating resulting solidified particles into a multiparticle body, wherein the improvement comprises the provision of greater than 0.15% of a metal which diffuses in the aluminum solid state at a rate less than that of Mn. Aluminum containing greater than 0.15% of a metal which diffuses in the aluminum solid state at a rate less than that of Mn.

  4. Powder metallurgy Rene 95 rotating turbine engine parts, volume 2

    NASA Technical Reports Server (NTRS)

    Wilbers, L. G.; Redden, T. K.

    1981-01-01

    A Rene 95 alloy as-HIP high pressure turbine aft shaft in the CF6-50 engine and a HIP plus forged Rene 95 compressor disk in the CFM56 engine were tested. The CF6-50 engine test was conducted for 1000 C cycles and the CFM56 test for 2000 C cycles. Post test evaluation and analysis of the CF6-50 shaft and the CFM56 compressor disk included visual, fluorescent penetrant, and dimensional inspections. No defects or otherwise discrepant conditions were found. These parts were judged to have performed satisfactorily.

  5. Dual-Alloy Disks are Formed by Powder Metallurgy

    NASA Technical Reports Server (NTRS)

    Harf, F. H.; Miner, R. V.; Kortovich, C. S.; Marder, J. M.

    1982-01-01

    High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

  6. PROCESS OF FORMING POWDERED MATERIAL

    DOEpatents

    Glatter, J.; Schaner, B.E.

    1961-07-14

    A process of forming high-density compacts of a powdered ceramic material is described by agglomerating the powdered ceramic material with a heat- decompossble binder, adding a heat-decompossble lubricant to the agglomerated material, placing a quantity of the material into a die cavity, pressing the material to form a compact, pretreating the compacts in a nonoxidizing atmosphere to remove the binder and lubricant, and sintering the compacts. When this process is used for making nuclear reactor fuel elements, the ceramic material is an oxide powder of a fissionsble material and after forming, the compacts are placed in a cladding tube which is closed at its ends by vapor tight end caps, so that the sintered compacts are held in close contact with each other and with the interior wall of the cladding tube.

  7. Identification of the fragmentation of brittle particles during compaction process by the acoustic emission technique.

    PubMed

    Favretto-Cristini, Nathalie; Hégron, Lise; Sornay, Philippe

    2016-04-01

    Some nuclear fuels are currently manufactured by a powder metallurgy process that consists of three main steps, namely preparation of the powders, powder compaction, and sintering of the compact. An optimum between size, shape and cohesion of the particles of the nuclear fuels must be sought in order to obtain a compact with a sufficient mechanical strength, and to facilitate the release of helium and fission gases during irradiation through pores connected to the outside of the pellet after sintering. Being simple to adapt to nuclear-oriented purposes, the Acoustic Emission (AE) technique is used to control the microstructure of the compact by monitoring the compaction of brittle Uranium Dioxide (UO2) particles of a few hundred micrometers. The objective is to identify in situ the mechanisms that occur during the UO2 compaction, and more specifically the particle fragmentation that is linked to the open porosity of the nuclear matter. Three zones of acoustic activity, strongly related to the applied stress, can be clearly defined from analysis of the continuous signals recorded during the compaction process. They correspond to particle rearrangement and/or fragmentation. The end of the noteworthy fragmentation process is clearly defined as the end of the significant process that increases the compactness of the material. Despite the fact that the wave propagation strongly evolves during the compaction process, the acoustic signature of the fragmentation of a single UO2 particle and a bed of UO2 particles under compaction is well identified. The waveform, with a short rise time and an exponential-like decay of the signal envelope, is the most reliable descriptor. The impact of the particle size and cohesion on the AE activity, and then on the fragmentation domain, is analyzed through the discrete AE signals. The maximum amplitude of the burst signals, as well as the mean stress corresponding to the end of the recorded AE, increase with increasing mean diameter of the particles. Moreover, the maximum burst amplitude increases with increasing particle cohesion. PMID:26742631

  8. [Respiratory diseases in metallurgy production workers].

    PubMed

    Shliapnikov, D M; Vlasova, E M; Ponomareva, T A

    2012-01-01

    The authors identified features of respiratory diseases in workers of various metallurgy workshops. Cause-effect relationships are defined between occupational risk factors and respiratory diseases, with determining the affection level. PMID:23461183

  9. Powder and particulate production of metallic alloys

    NASA Technical Reports Server (NTRS)

    Grant, N. J.

    1982-01-01

    Developments of particulate metallurgy of alloyed materials where the final products is a fully dense body are discussed. Particulates are defined as powders, flakes, foils, silvers, ribbons and strip. Because rapid solidification is an important factor in particulate metallurgy, all of the particulates must have at least one dimension which is very fine, sometimes as fine as 10 to 50 microns, but move typically up to several hundred microns, provided that the dimension permits a minimum solidification rate of at least 100 K/s.

  10. Materials for Advanced Turbine Engines. Volume 1; Power Metallurgy Rene 95 Rotating Turbine Engine Parts

    NASA Technical Reports Server (NTRS)

    Pfouts, W. R.; Shamblen, C. E.; Mosier, J. S.; Peebles, R. E.; Gorsler, R. W.

    1979-01-01

    An attempt was made to improve methods for producing powder metallurgy aircraft gas turbine engine parts from the nickel base superalloy known as Rene 95. The parts produced were the high pressure turbine aft shaft for the CF6-50 engine and the stages 5 through 9 compressor disk forgings for the CFM56/F101 engines. A 50% cost reduction was achieved as compared to conventional cast and wrought processing practices. An integrated effort involving several powder producers and a major forging source were included.

  11. Better metallurgy for process equipment

    SciTech Connect

    Rayner, R.E.

    1994-01-01

    Metallurgy choices have expanded significantly for process equipment and pumps used for handling difficult corrosive fluids. If they have been specifying the austenitic AISI types 316, 316L, 317, 317L or the newer first generation alloy 329 in their pumps, there is a strong message in recent literature. Based on tests and experience there are better, often less costly alternatives. In the case of CD[sub 4]MCu, N08020 and 904L, there are lower-cost material alternatives for many applications. For SA S31254 and SA N08367, there are some less aggressive can be substituted. These alternatives are the new second generation duplex steels. The lower cost of the duplex alloys is a result of the reduced nickel content, which is about half that of the standard austenitics. Also, their carbon content is low; the same as 316L and 317L for most alloys, including S31803. The second generation duplex alloys offer significant value improvement in a vast majority of applications over the common austenitics and ferritics. Further, their improved resistance to corrosion and improved physical properties relative to the expensive. and in many cases proprietary, highly corrosion-resistant, super-ferritics and super-austenitics, means that they can and should be considered as an alternative for applications where those materials are now overqualified. Strength, toughness and wide corrosion resistance are all-important properties and considerations for process pump materials. Combine these with competitive cost and there is an opportunity that must be investigated.

  12. Sintering of sponge and hydride-dehydride titanium powders

    SciTech Connect

    Alman, David E.; Gerdemann, Stephen J.

    2004-04-01

    The sintering behavior of compacts produced from sponge and hydride-dehydride (HDH) Ti powders was examined. Compacts were vacuum sintered at 1200 or 1300 deg C for 30, 60, 120, 240, 480 or 960 minutes. The porosity decreased with sintering time and/or temperature in compacts produced from the HDH powders. Compacts produced from these powders could be sintered to essentially full density. However, the sintering condition did not influence the amount of porosity present in compacts produced from the sponge powders. These samples could only be sintered to a density of 97% theoretical. The sintering behavior was attributed to the chemical impurities in the powders.

  13. Real time monitoring of powder blend bulk density for coupled feed-forward/feed-back control of a continuous direct compaction tablet manufacturing process.

    PubMed

    Singh, Ravendra; Román-Ospino, Andrés D; Romañach, Rodolfo J; Ierapetritou, Marianthi; Ramachandran, Rohit

    2015-11-10

    The pharmaceutical industry is strictly regulated, where precise and accurate control of the end product quality is necessary to ensure the effectiveness of the drug products. For such control, the process and raw materials variability ideally need to be fed-forward in real time into an automatic control system so that a proactive action can be taken before it can affect the end product quality. Variations in raw material properties (e.g., particle size), feeder hopper level, amount of lubrication, milling and blending action, applied shear in different processing stages can affect the blend density significantly and thereby tablet weight, hardness and dissolution. Therefore, real time monitoring of powder bulk density variability and its incorporation into the automatic control system so that its effect can be mitigated proactively and efficiently is highly desired. However, real time monitoring of powder bulk density is still a challenging task because of different level of complexities. In this work, powder bulk density which has a significant effect on the critical quality attributes (CQA's) has been monitored in real time in a pilot-plant facility, using a NIR sensor. The sensitivity of the powder bulk density on critical process parameters (CPP's) and CQA's has been analyzed and thereby feed-forward controller has been designed. The measured signal can be used for feed-forward control so that the corrective actions on the density variations can be taken before they can influence the product quality. The coupled feed-forward/feed-back control system demonstrates improved control performance and improvements in the final product quality in the presence of process and raw material variations. PMID:26386140

  14. Mound powder loader, Mod 1

    SciTech Connect

    Gress, A.V. Jr.

    1985-08-21

    At the investigation of Sandia Albuquerque, a semiautomatic powder loader was designed and fabricated for pyrotechnics devices. The basic functions of the system were to load a precise, measured amount of powder into a charge holder and to compact the mixture to a specified density. This report documents the history, rationale, design, and performance of the Mod 1 loader.

  15. Welding Metallurgy and Weldability of Stainless Steels

    NASA Astrophysics Data System (ADS)

    Lippold, John C.; Kotecki, Damian J.

    2005-03-01

    Welding Metallurgy and Weldability of Stainless Steels, the first book in over twenty years to address welding metallurgy and weldability issues associated with stainless steel, offers the most up-to-date and comprehensive treatment of these topics currently available. The authors emphasize fundamental metallurgical principles governing microstructure evolution and property development of stainless steels, including martensistic, ferric, austenitic, duplex, and precipitation hardening grades. They present a logical and well-organized look at the history, evolution, and primary uses of each stainless steel, including detailed descriptions of the associated weldability issues.

  16. Fabrication of metal matrix composite by semi-solid powder processing

    SciTech Connect

    Wu, Yufeng

    2012-11-28

    Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the fabrication of MMCs were explored. An analytical model was developed to understand the deformation mechanism of the powder compact in the semi-solid state. The densification behavior of the Al6061 and SiC powder mixtures was investigated with different liquid fractions and SiC volume fractions. The limits of SPP were analyzed in terms of reinforcement phase loading and its impact on the composite microstructure. To explore adoption of new materials, carbon nanotube (CNT) was investigated as a reinforcing material in aluminum matrix using SPP. The process was successfully modeled for the mono-phase powder (Al6061) compaction and the density and density distribution were predicted. The deformation mechanism at low and high liquid fractions was discussed. In addition, the compaction behavior of the ceramic-metal powder mixture was understood, and the SiC loading limit was identified by parametric study. For the fabrication of CNT reinforced Al6061 composite, the mechanical alloying of Al6061-CNT powders was first investigated. A mathematical model was developed to predict the CNT length change during the mechanical alloying process. The effects of mechanical alloying time and processing temperature during SPP were studied on the mechanical, microstructural and compositional properties of the Al6061-CNT composites. A shear lag model was applied to predict the mechanical property (hardness) of the composite. This work demonstrated the promising potential of SPP in the fabrication of particle/fiber (nanotube) reinforced MMCs.

  17. Powder-Metallurgical Bearings For Turbopumps

    NASA Technical Reports Server (NTRS)

    Bhat, B. N.; Humphries, T. S.; Thom, R. L.; Moxson, V.; Friedman, G. I.; Dolan, F. J.; Shipley, R. J.

    1993-01-01

    Bearings fabricated by powder metallurgy developed for use in machines subjected to extremes of temperature, rolling-contact cyclic stresses, and oxidizing or otherwise corrosive fluids. Bearings also extend operating lives of other machines in which bearings required to resist extreme thermal, mechanical, and chemical stresses. One alloy exhibiting outstanding properties was MRC-2001. Resistance to fatigue, stress corrosion cracking, and wear found superior to that of 440C stainless steel.

  18. Characterization and Control of Powder Properties for Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Strondl, A.; Lyckfeldt, O.; Brodin, H.; Ackelid, U.

    2015-03-01

    Powder characterization and handling in powder metallurgy are important issues and the required powder properties will vary between different component manufacturing processes. By understanding and controlling these, the final material properties for different applications can be improved and become more reliable. In this study, the metal powders used in additive manufacturing (AM) in terms of electron beam melting and selective laser melting have been investigated regarding particle size and shape using dynamic image analysis. In parallel, powder flow characteristics have been evaluated with a powder rheometer. Correlations within the results have been found between particle shape and powder flow characteristics that could explain certain effects of the powder processing in the AM processes. The impact, however, in the processing performance as well as in ultimate material properties was found to be limited.

  19. PREPARATION OF COMPACTS MADE FROM URANIUM AND BERYLLIUM BY SINTERING

    DOEpatents

    Angier, R.P.

    1961-04-11

    A powder metallurgical method for making high-density compacts of uranium and beryllium is reported. Powdered UBe/sub 9/ and powdered Be are blended, compacted, and then sintered by rapidly heating to a temperature of approximately 1220 to 1280 deg C in an inert atmosphere.

  20. The effect of high density electric pulses on sintered aluminum 201AB silicon carbide MMC PM compacts during plastic deformation

    NASA Astrophysics Data System (ADS)

    Dariavach, Nader Guseinovich

    The effect of high-density electrical pulses on mechanical and structural properties of sintered aluminum SiC metal-matrix composites, fabricated by standard powder-metallurgy compaction and sintering, was investigated. Three types of phenomena where investigated during transverse rupture testing of the samples: a consolidation effect (increasing of the transverse rupture strength (TRS)), an electroplastic effect (decreasing of the flow stresses), and an increasing of the stress intensity factor by electric pulse application. It was observed, that an increase in the TRS strength of sintered powder metallurgy (PM) aluminum and aluminum metal matrix composite (MMC) compacts is a result of the electric pulse consolidation effect due to non-uniform temperature distribution around the grain boundaries. Three analytical models of the thermal effect of electric pulses on aluminum samples where considered: total temperature change of the sample due to a one electric pulse, one-dimensional steady state model and transient 2D thermal analysis of the temperature distribution around the grain boundary. The 2D transient analysis shows that the temperature rise in the grain boundary of a sintered PM aluminum sample due to an electric pulse can exceed the melting point. At the same time the temperature of the bulk material has an insignificant (<28°C) change. It was found that the electroplastic effect, due to electric pulse application, can account for up to a 40% load drop in aluminum MMC PM compacts. Reduction of flow stresses during plastic deformation could reduce the risk of structural damage, micro-cracks, SiC particle fracture and delamination of the aluminum MMC. These results may find practical application for manufacturing processes such as forging, extrusion, rolling, which involve plastic deformation. It was experimentally proven that a non-uniform temperature distribution around the crack could re-melt the crack tip and increase the strength of the damaged material. The experimental study shows an increase in the stress intensity factor up to 76% for sintered aluminum PM compacts and up to 116% for sintered aluminum MMC PM compacts due to application of high-density electric pulses during transverse rapture testing.

  1. Properties of alloy steel powders produced by the method of diffusion impregnation (review)

    SciTech Connect

    Napara-Volgina, S.G.

    1985-06-01

    In their review of research on the properties of alloy steel powders produced by the method of diffusion impregnation, the authors systematize their data into three charts, one on the characteristics of charges and the recommended areas of use of powders, one on the chemical and particle size compositions and technological properties of the powders, and one on the fine crystalline structure of alloy powders of different compositions. The authors recommend the use of such powders, especially powder metallurgy constructional steels, produced by hot stamping and other methods providing high density.

  2. Physical Metallurgy of High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Yeh, Jien-Wei

    2015-08-01

    Two definitions of high-entropy alloys (HEAs), based on composition and entropy, are reviewed. Four core effects, i.e., high entropy, sluggish diffusion, severe lattice distortion, and cocktail effects, are mentioned to show the uniqueness of HEAs. The current state of physical metallurgy is discussed. As the compositions of HEAs are entirely different from that of conventional alloys, physical metallurgy principles might need to be modified for HEAs. The thermodynamics, kinetics, structure, and properties of HEAs are briefly discussed relating with the four core effects of HEAs. Among these, a severe lattice distortion effect is particularly emphasized because it exerts direct and indirect influences on many aspects of microstructure and properties. Because a constituent phase in HEAs can be regarded as a whole-solute matrix, every lattice site in the matrix has atomic-scale lattice distortion. In such a distorted lattice, point defects, line defects, and planar defects are different from those in conventional matrices in terms of atomic configuration, defect energy, and dynamic behavior. As a result, mechanical and physical properties are significantly influenced by such a distortion. Suitable mechanisms and theories correlating composition, microstructure, and properties for HEAs are required to be built in the future. Only these understandings make it possible to complete the physical metallurgy of the alloy world.

  3. Compaction of Ductile and Fragile Grains

    NASA Astrophysics Data System (ADS)

    Creissac, S.; Pouliquen, O.; Dalloz-Dubrujeaud, B.

    2009-06-01

    The compaction of powders into tablets is widely used in several industries (cosmetics, food, pharmaceutics…). In all these industries, the composition of the initial powder is complex, and the behaviour under compaction is not well known, also the mechanical behaviour of the tablets. The aim of this paper is to understand the behaviour (pressure vs density) of a simplified media made of fragile and ductile powders, varying the relative ratio of each powder. Some compaction experiments were carried out with glass beads (fragile) and Polyethylen Glycol powder (ductile). We observe two typical behaviours, depending on the relative volumic fraction of each component. A transition is pointed out, observing the evolution of the slope of the curve pressure/density. This transition is explained by geometrical considerations during compaction. A model is proposed, based on the assumption that the studied media can be compare to a diphasic material with a continuous phase (the ductile powder) and a discrete phase (the fragile powder). The result of this model is compare to the experimental results of compaction, and give a good prediction of the behaviour of the different mixing, knowing the behaviour of the ductile and the fragile phase separately. These results were also interpreted in terms of Heckel parameter which characterizes the ability of the powder to deform plastically under compaction. Some mechanical tests were also performed to compare the mechanical resitance of the obtained tablets.

  4. Compaction properties of isomalt.

    PubMed

    Bolhuis, Gerad K; Engelhart, Jeffrey J P; Eissens, Anko C

    2009-08-01

    Although other polyols have been described extensively as filler-binders in direct compaction of tablets, the polyol isomalt is rather unknown as pharmaceutical excipient, in spite of its description in all the main pharmacopoeias. In this paper the compaction properties of different types of ispomalt were studied. The types used were the standard product sieved isomalt, milled isomalt and two types of agglomerated isomalt with a different ratio between 6-O-alpha-d-glucopyranosyl-d-sorbitol (GPS) and 1-O-alpha-d-glucopyranosyl-d-mannitol dihydrate (GPM). Powder flow properties, specific surface area and densities of the different types were investigated. Compactibility was investigated by compression of the tablets on a compaction simulator, simulating the compression on high-speed tabletting machines. Lubricant sensitivity was measured by compressing unlubricated tablets and tablets lubricated with 1% magnesium stearate on an instrumented hydraulic press. Sieved isomalt had excellent flow properties but the compactibility was found to be poor whereas the lubricant sensitivity was high. Milling resulted in both a strong increase in compactibility as an effect of the higher surface area for bonding and a decrease in lubricant sensitivity as an effect of the higher surface area to be coated with magnesium stearate. However, the flow properties of milled isomalt were too bad for use as filler-binder in direct compaction. Just as could be expected, agglomeration of milled isomalt by fluid bed agglomeration improved flowability. The good compaction properties and the low lubricant sensitivity were maintained. This effect is caused by an early fragmentation of the agglomerated material during the compaction process, producing clean, lubricant-free particles and a high surface for bonding. The different GPS/GPM ratios of the agglomerated isomalt types studied had no significant effect on the compaction properties. PMID:19327398

  5. Metallurgy and Heat Treating. Welding Module 7. Instructor's Guide.

    ERIC Educational Resources Information Center

    Missouri Univ., Columbia. Instructional Materials Lab.

    This guide is intended to assist vocational educators in teaching a three-unit module in metallurgy and heat treating. The module is part of a welding curriculum that has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The basic principles of metallurgy and heat treatment and techniques for…

  6. Discrete element modeling of powder consolidation and the formation of titanium-matrix composites from powder-fiber monotapes

    NASA Astrophysics Data System (ADS)

    Newell, Kenneth James

    A three year research effort is completed with the development of the Discrete Element Consolidation Analyzer (DECA) for process modeling the formation of titanium composites from powder-fiber monotapes. The primary goal of the DECA process model is to provide a statistically realistic analysis of the various physical processes necessary to achieve higher quality composites from the powder-fiber technique. Over the course of this effort, research and code development was conducted in three distinct stages. The first stage focused on the simulation of initial geometry of the powder and fibers as well as the evolution of tape configuration during the pre-consolidation processing steps. The second stage developed the mechanics of the discrete element powder consolidation and the material characterization methods necessary to model the viscoplastic response of the powder to transient thermal and mechanical boundary conditions. The final stage incorporated the presence of fibers to evaluate the interaction mechanics and possible fibers damage resulting from discrete powder-fiber contacts. As a conclusion to the research, DECA model predictions of density versus time for various consolidation profiles are directly compared to actual consolidation test results and a DECA prescribed process profile is used to fabricate a 6sp{''} × 6sp{''} composite panel of Ti-6242/SCS-6. In completing this research, the discrete element modeling technique has proven to be a powerful tool for the analysis and simulation of metal powder consolidation as well as the consolidation of metal matrix composites. The DECA code orchestrates the use of particle kinetics, some simple aspects of gas dynamics, elasticity, plasticity, creep and various innovative material characterization methods to produce a seamless analysis for powder metallurgy processing of composites. Through the application of the DECA capability, many aspects of the processing stages have been elucidated for further investigation and possibly for optimization to in the end provide the underlying goal of increasing quality and reduce cost of producing composites from the powder-fiber monotape method. As a minimum, it was desired that the resulting code provide an accurate prediction of relative density as a function of applied pressure, temperature, and time. This goal was achieved. However, it was later realized that under specific conditions of pre-heat and unidirectional compaction, the rate change in relative density could be determined by the rate of applied load. With the appropriate control and load capacity, densification by plasticity and transient creep mechanisms can achieve complete void removal. Unfortunately, the real world doesn't work with 1sp{''} × 1sp{''} samples and the pressurization rates attained by most HIP units are several orders of magnitude below those specific conditions in which it is possible to essentially "hammer" the voids out of the composite. As a result, it was learned that under certain conditions Ti-6242/SCS-6 monotape (temperature between 1650sp°F and beta-transus with a loading rate greater than 10 kips/min.), it is possible to consolidate Ti-6242/SCS-6 monotape composite in a matter of minutes without damaging fibers. (Abstract shortened by UMI.)

  7. Ancient metallurgy and nuclear waste containment

    SciTech Connect

    Goodway, M.

    1993-12-31

    Archaeological artifacts of glass, ceramic, and metal provide examples of long term durability and as such have been surveyed by the nuclear agencies of several countries as a possible guide to choices of materials for the containment of nuclear waste. In the case of metals evaluation is difficult because of the loss of many artifacts to recycling and corrosion processes, as well as by uncertainty as to the environmental history under which the remainder survived. More recently the study of ancient metallurgy has expanded to included other materials associated with metals processing. It is suggested that an impermeable ceramic composite used in ancient metals processing installations should be reproduced and tested for its resistance to radiation damage. This material was synthesized more than two millennia ago and has a proven record of durability. These installations have had no maintenance but are intact, some still holding water.

  8. METHOD OF PRODUCING SHAPED BODIES FROM POWDERED METALS

    DOEpatents

    Blainey, A.

    1960-05-31

    A method is given for enclosing a body of uranium in a sheath of compacted beryllium or zirconium powder and comprises enveloping the body with uncompacted powder and pressing at a temperature above the beta - gamma transition point of uranium, thereby causing the uranium to flow and isotropically compress the powder.

  9. Fluidized reduction of oxides on fine metal powders without sintering

    NASA Technical Reports Server (NTRS)

    Hayashi, T.

    1985-01-01

    In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.

  10. Looking North into Lab Metallurgy Testing Area and Enrichment Motor ...

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

    Looking North into Lab Metallurgy Testing Area and Enrichment Motor within Recycle Recovery Building - Hematite Fuel Fabrication Facility, Recycle Recovery Building, 3300 State Road P, Festus, Jefferson County, MO

  11. 1. Photocopy from J. L. Bray, The Principles of Metallurgy, ...

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

    1. Photocopy from J. L. Bray, The Principles of Metallurgy, Ginn & Company, New York, 1929 - International Smelting & Refining Company, Tooele Smelter, Sinter Plant, State Route 178, Tooele, Tooele County, UT

  12. Development of a power metallurgy superalloy for use at 1800-2000 F (980-1090 C)

    NASA Technical Reports Server (NTRS)

    Kortovich, C. S.

    1973-01-01

    A program was conducted to develop a powder metallurgy nickel-base superalloy for 1800-2000 F (980-1090 C) temperature applications. The feasibility of a unique concept for alloying carbon into a superalloy powder matrix and achieving both grain growth and a discrete particle grain boundary carbide precipitation was demonstrated. The process consisted of blending metastable carbides with a carbon free base alloy and consolidating this blend by hot extrusion. This was followed by heat treatment to grow a desired ASTM No. 2-3 grain size and to solution the metastable carbides to allow precipitation of discrete particle grain boundary carbides during subsequent aging heat treatments. The best alloy developed during this program was hydrogen-atomized, thermal-mechanically processed, modified MAR-M246 base alloy plus VC (0.28 w/o C). Although below those for cast MAR-M246, the mechanical properties exhibited by this alloy represent the best combination offered by conventional powder metallurgy processing to date.

  13. Fatigue-crack propagation in aluminum-lithium alloys processed by power and ingot metallurgy

    SciTech Connect

    Venkateswara Rao, K.T.; Ritchie, R.O. ); Kim, N.J. ); Pizzo, P.P. )

    1990-04-01

    Fatigue-crack propagation behavior in powder-metallurgy (P/M) aluminum-lithium alloys, namely, mechanically-alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.80{sub 2} (Inco 905-XL) and rapid-solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (Allied 644-B) extrusions, has been studied, and results compared with data on an equivalent ingot-metallurgy (I/M) Al-Li alloy, 2090-T81 plate. Fatigue-crack growth resistance of the RSP Al-Li alloy is found to be comparable to the I/M Al-Li alloy; in contrast, crack velocities in MA 905-XL extrusions are nearly three orders of magnitude faster. Growth-rate response in both P/M Al-Li alloys, however, is high anisotropic. Results are interpreted in terms of the microstructural influence of strengthening mechanism, slip mode, grain morphology and texture on the development of crack-tip shielding from crack-path deflection and crack closure. 14 refs., 7 figs., 2 tabs.

  14. Explosive compaction of WC+Co mixture by axisymmetric scheme

    NASA Astrophysics Data System (ADS)

    Buzyurkin, A. E.; Kraus, E. I.; Lukyanov, Ya L.

    2015-11-01

    This paper is devoted to the problem of development and optimization of schemes for explosive compaction of mixtures of solid powder materials with metal bond. For this purpose, experiments were conducted on explosive compaction of mixtures of tungsten carbide (WC) and cobalt (Co) using a simple cylindrical compaction system. In addition, a numerical simulation of shock waves propagation in two-phase porous medium WC+Co was carried out. Based on experimental and numerical studies of shock wave propagation, the optimal modes of explosive compaction of two-phase powder media, representing mixtures of solid powder materials with metal bond, were found. It is shown that the most preferable compaction mode for obtaining a uniform durable compact of a mixture of powders WC+Co with ratio 9:1 by volume in axially symmetric scheme with central mandrel corresponds to the detonation velocity of 4.6 km/s followed by sintering.

  15. Ceramic compaction models: Useful design tools or simple trend indicators?

    SciTech Connect

    Mahoney, F.M.; Readey, M.J.

    1995-08-01

    It is well-known that dry pressing of ceramic powders leads to density gradients in a ceramic compact resulting in non-uniform shrinkage during densification. This necessitates diamond grinding to final dimensions which, in addition to being an extra processing step, greatly increases the manufacturing cost of ceramic components. To develop methods to control and thus mitigate density variations in compacted powders, it has been an objective of researchers to better understand the mechanics of the compaction process and the underlying material and tooling effects on the formation of density gradients. This paper presents a review of models existing in the literature related to the compaction behavior of ceramic powders. In particular, this paper focuses on several well-known compaction models that predict pressure and density variations in powder compacts.

  16. Influence of consolidation method on structure/properties of rapidly solidified Type 304 SS powders

    SciTech Connect

    Flinn, J.E.; Korth, G.E.; Wright, R.N.

    1988-01-01

    The structure/properties of consolidated, centrifugally atomized (CA) Type 304 SS powders containing approx.8 appM helium entrapped during powder processing were evaluated. Three powder consolidation methods were used in the study: hot extrusion, hot isostatic pressing (HIPping), and dynamic (using explosives). In addition, cold-rolled 50% HIPped material was included in the evaluation. The four forms of consolidated powders were fully dense and possessed good bond strengths. The bond strength of the HIPped powders was the lowest. The consolidated materials were subjected to 1 h heat treatments and their grain growth, tensile, and creep behaviors were compared with those of wrought ingot metallurgy Type 304 SS materials. Grain growth of the CA Type 304 SS consolidated powders was substantially lower than for the wrought material. Similarly, significant strengthening was observed for the powder materials. The apparent microstructure stability and strengthening observed for the consolidated powder materials is attributed to the entrapped helium. 5 figs., 4 tabs.

  17. Powder diffraction

    SciTech Connect

    Hart, M.

    1995-12-31

    the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940`s, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments.

  18. Compact Storage

    After a detailed inventory is completed and published on the web, processed materials are stored in compact shelving in the Field Records Collection. Collections are organized by scientist and project....

  19. Consolidation of Nanocrystalline Si and Ge Powders by Shock Waves

    NASA Astrophysics Data System (ADS)

    Chikhradze, M.; Godibadze, B.; Bochorishvili, N.

    2011-12-01

    Pure nano sized (50 nm) Si and coarse Si0,7Ge0,3 powders (≤20 micron) were compacted near theoretical density by shock-compaction technology. The powder was placed in a steel container and explosively compacted by explosively induced shock waves of cylindrical symmetry. Ammonium nitride based industrial explosives and electrical detonators were used for the generation of shock waves. Explosive compaction experiments were performed in range of pressure impulses of 5-10 Gpa. This process occurs in a combination of two stages. The first is the preliminary densification by static pressure to a container with pure elemental Si and Si0.68Ge0.32 powder, and is followed by the second stage, shock-wave compaction. The relationships between the compacting conditions, the precursor particle sizes, and the consolidation and properties of this new ultra high performance alloy are discussed in the paper.

  20. Face powder poisoning

    MedlinePlus

    Face powder poisoning occurs when someone swallows or breathes in this substance. This article is for information ... The ingredients in face powder that can be harmful are: Baking soda Talcum powder Many other types of powder

  1. Synthesis and processing of monosized oxide powders

    DOEpatents

    Barringer, E.A.; Fegley, M.B. Jr.; Bowen, H.K.

    1985-09-24

    Uniform-size, high-purity, spherical oxide powders are formed by hydrolysis of alkoxide precursors in dilute alcoholic solutions. Under controlled conditions (concentrations of 0.03 to 0.2 M alkoxide and 0.2 to 1.5 M water, for example) oxide particles on the order of about 0.05 to 0.7 microns can be produced. Methods of doping such powders and forming sinterable compacts are also disclosed. 6 figs.

  2. Synthesis and processing of monosized oxide powders

    DOEpatents

    Barringer, Eric A.; Fegley, Jr., M. Bruce; Bowen, H. Kent

    1985-01-01

    Uniform-size, high-purity, spherical oxide powders are formed by hydrolysis of alkoxide precursors in dilute alcoholic solutions. Under controlled conditions (concentrations of 0.03 to 0.2 M alkoxide and 0.2 to 1.5 M water, for example) oxide particles on the order of about 0.05 to 0.7 micron can be produced. Methods of doping such powders and forming sinterable compacts are also disclosed.

  3. Study of Underwater Shock Compaction Device for Compaction of Titanium Diboride

    NASA Astrophysics Data System (ADS)

    Kennedy, G. B.; Kim, Y. K.; Hokamoto, K.; Itoh, S.

    2007-12-01

    Shock compaction for powders has been used to study bulk consolidation of powder materials. Shock compaction has the advantage of processing at low temperatures and short duration to limit effects of high temperatures for long times, such as increased grain size and high energy cost. Many methods of shock loading of powders have been employed: direct contact with explosive, explosively driven flyer plates, and flyer plates launched with light gas or propellant gun. Another method, using explosives to create a shockwave in water that is then contact with a powder container, has been used extensively at Kumamoto University. This work presents a study of the development of the underwater shockwave device and investigates the water container geometry for control of parameters for shockwave peak pressure, duration, and distribution through the powder compaction process. Results of simulations for optimization of shock compaction properties are presented along with measurements from manganin gauge pressure measurements obtained from underwater shock compaction of titanium diboride. The goal of this work is to develop a better understanding of the entire compaction process to utilize the in-situ data to modify numerical simulations to predict performance.

  4. Why materials science and engineering is good for metallurgy

    NASA Astrophysics Data System (ADS)

    Flemings, Merton C.

    2001-04-01

    Metallurgy/materials education will continue to evolve to encompass, in an intellectually unified way, the full range of structural and functional materials. Computation, information, and other advanced sciences and technologies will assume increasing roles in materials education, as will distance and continuing education. The advantages of the changes will be many ... to the graduates, to emerging industries, and to the traditional metallurgical industries seeking productive, creative young engineers as employees. The need for continuing change in our metallurgy/materials departments is now no less if we are to attract the best young people into our field in the numbers and to best serve the needs of industry.

  5. Why materials science and engineering is good for metallurgy

    NASA Astrophysics Data System (ADS)

    Flemings, Merton C.

    2001-04-01

    Metallurgy/materials education will continue to evolve to encompass, in an intellectually unified way, the full range of structural and functional materials. Computation, information, and other advanced sciences and technologies will assume increasing roles in materials education, as will distance and continuing education. The advantages of the changes will be many … to the graduates, to emerging industries, and to the traditional metallurgical industries seeking productive, creative young engineers as employees. The need for continuing change in our metallurgy/materials departments is now no less if we are to attract the best young people into our field in the numbers needed and to best serve the needs of industry.

  6. Tantalum powder consolidation, modeling and properties

    SciTech Connect

    Bingert, S.R.; Vargas, V.D.; Sheinberg, H.C.

    1996-10-01

    A systematic approach was taken to investigate the consolidation of tantalum powders. The effects of sinter time, temperature and ramp rate; hot isostatic pressing (HIP) temperature and time; and powder oxygen content on consolidation density, kinetics, microstructure, crystallographic texture, and mechanical properties have been evaluated. In general, higher temperatures and longer hold times resulted in higher density compacts with larger grain sizes for both sintering and HIP`ing. HIP`ed compacts were consistently higher in density than sintered products. The higher oxygen content powders resulted in finer grained, higher density HIP`ed products than the low oxygen powders. Texture analysis showed that the isostatically processed powder products demonstrated a near random texture. This resulted in isotropic properties in the final product. Mechanical testing results showed that the HIP`ed powder products had consistently higher flow stresses than conventionally produced plates, and the sintered compacts were comparable to the plate material. A micromechanics model (Ashby HIP model) has been employed to predict the mechanisms active in the consolidation processes of cold isostatic pressing (CIP), HIP and sintering. This model also predicts the density of the end product and whether grain growth should be expected under the applied processing conditions.

  7. Roller compaction of different pseudopolymorphic forms of theophylline: Effect on compressibility and tablet properties.

    PubMed

    Hadzović, Ervina; Betz, Gabriele; Hadzidedić, Seherzada; El-Arini, Silvia Kocova; Leuenberger, Hans

    2010-08-30

    The effect of roller compaction on disintegration time, dissolution rate and compressibility of tablets prepared from theophylline anhydrate powder, theophylline anhydrate fine powder and theophylline monohydrate was studied. In addition, the influence of adding microcrystalline cellulose, a commonly used excipient, in mixtures with these materials was investigated. Theophylline anhydrate powder was used as a model drug to investigate the influence of different compaction pressures on the tablet properties. Tablets with same porosity were prepared by direct compaction and by roller compaction/re-compaction. Compressibility was characterized by Heckel and modified Heckel equations. Due to the property of polymorphic materials to change their form during milling and compression, X-ray diffraction analysis of theophylline anhydrate powder, theophylline anhydrate fine powder and theophylline monohydrate powders and granules was carried out. After roller compaction the disintegration time and the dissolution rate of the tablets were significantly improved. Compressibility of theophylline anhydrate powder and theophylline anhydrate fine powder was decreased, while theophylline monohydrate showed higher compressibility after roller compaction. Microcrystalline cellulose affected compressibility of theophylline anhydrate powder, theophylline anhydrate fine powder and theophylline monohydrate whereby the binary mixtures showed higher compressibility than the individual materials. X-ray diffraction analyses confirmed that there were no polymorphic/pseudopolymorphic changes after roller compaction. PMID:20600735

  8. A laboratory means to produce tough aluminum sheet from powder

    NASA Technical Reports Server (NTRS)

    Singleton, O. R.; Royster, D. M.; Thomas, J. R.

    1990-01-01

    The rapid solidification of aluminum alloys as powder and the subsequent fabrication processes can be used to develop and tailor alloys to satisfy specific aerospace design requirements, including high strength and toughness. Laboratory procedures to produce aluminum powder-metallurgy (PM) materials are efficient but require evidence that the laboratory methods used can produce a product with superior properties. This paper describes laboratory equipment and procedures which can be used to produce tough aluminum PM sheet. The processing of a 2124 + 0.9 percent Zr aluminum alloy powder is used as an example. The fully hardened sheet product is evaluated in terms of properties and microstructure. The key features of the vacuum hot press pressing operation used to consolidate the powder are described. The 2124 + 0.9 percent Zr - T8 temper aluminum sheet produced was both strong (460-490 MPa yield strength) and tough (Kahn Tear unit-propagation- energy values over three times those typical for ingot metallurgy 2024-T81). Both the longitudinal and longitudinal-transverse directions of the sheet were tested. The microstructure was well refined with subgrains of one or two micrometers. Fine dispersoids of Al3Zr in the precipitate free regions adjacent to boundaries are believed to contribute to the improved toughness.

  9. Energetic powder

    DOEpatents

    Jorgensen, Betty S.; Danen, Wayne C.

    2003-12-23

    Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

  10. Ceramic Powders

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

  11. Pipeline failure: The roles played by corrosion, flow and metallurgy

    SciTech Connect

    Paisley, D.; Barrett, N.; Wilson, O.

    1999-11-01

    Carbon dioxide corrosion has been widely studied in the field and laboratory. It is recognized that flow regime and metallurgy are important factors that influence in-situ corrosion rates but there are relatively few documented case studies that are able to separate the individual contributions of corrosion, flow regime and metallurgy on the observed corrosion damage. This paper deals with failure of a pipeline where high quality inspection data together with comprehensive as-built records and stable production conditions allowed the separate influences of flow and metallurgy on corrosion to be studied. The flow regimes in the pipeline ranged from low velocity, stratified flow to high velocity, slug flow. The inspection data showed that the affect of turbulent flow was to increase the frequency of corrosion pits and, in the case of weld corrosion, the mean corrosion rate. The pipeline was constructed from two grades of steel and welded using two types of welding consumable. One grade of pipeline steel corroded at a significantly higher rate and with a higher frequency of corrosion pits than another, apparently similar steel. However, no significant relationship was found between weld metallurgy and corrosion rate or frequency.

  12. Chemical and Metallurgy Research (CMR) Sample Tracking System Design Document

    SciTech Connect

    Bargelski, C. J.; Berrett, D. E.

    1998-09-01

    The purpose of this document is to describe the system architecture of the Chemical and Metallurgy Research (CMR) Sample Tracking System at Los Alamos National Laboratory. During the course of the document observations are made concerning the objectives, constraints and limitations, technical approaches, and the technical deliverables.

  13. 39. GENERAL VIEW LOOKING NORTH, SHOWING BUILDING NO. 318, METALLURGY ...

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

    39. GENERAL VIEW LOOKING NORTH, SHOWING BUILDING NO. 318, METALLURGY LAB, ON RIGHT, BUILDING NO. 319, GENERAL PURPOSE ADMINISTRATION BUILDING, ON LEFT AND BUILDING NO. 355, ADMINISTRATION BUILDING, RESEARCH & DEVELOPMENT, IN BACKGROUND LEFT. - Picatinny Arsenal, State Route 15 near I-80, Dover, Morris County, NJ

  14. NSF: A "Populist" Pattern in Metallurgy, Materials Research?

    ERIC Educational Resources Information Center

    Shapley, Deborah

    1975-01-01

    Describes the testimony of a University of Virginia professor of applied science, who charged that the National Science Foundation grants disproportionately small funds to the best university departments in the field of metallurgy and materials, while preferentially funding middle-ranked departments. (MLH)

  15. Iron Metallurgy: Technical Terminology Bulletin. Terminotech, Vol. 2, No. 7.

    ERIC Educational Resources Information Center

    General Electric Co. of Canada, Ltd., Montreal, Quebec.

    This issue of a bulletin of technological terminology is devoted to iron metallurgy. Various aspects of iron production are described in both French and English. An English-French dictionary of terms comprises the bulk of the document. Explanatory illustrations are appended. (JB)

  16. Wet powder seal for gas containment

    DOEpatents

    Stang, L.G.

    1979-08-29

    A gas seal is formed by a compact layer of an insoluble powder and liquid filling the fine interstices of that layer. The smaller the particle size of the selected powder, such as sand or talc, the finer will be the interstices or capillary spaces in the layer and the greater will be the resulting sealing capacity, i.e., the gas pressure differential which the wet powder layer can withstand. Such wet powder seal is useful in constructing underground gas reservoirs or storage cavities for nuclear wastes as well as stopping leaks in gas mains buried under ground or situated under water. The sealing capacity of the wet powder seal can be augmented by the hydrostatic head of a liquid body established over the seal.

  17. Wet powder seal for gas containment

    DOEpatents

    Stang, Louis G.

    1982-01-01

    A gas seal is formed by a compact layer of an insoluble powder and liquid filling the fine interstices of that layer. The smaller the particle size of the selected powder, such as sand or talc, the finer will be the interstices or capillary spaces in the layer and the greater will be the resulting sealing capacity, i.e., the gas pressure differential which the wet powder layer can withstand. Such wet powder seal is useful in constructing underground gas reservoirs or storage cavities for nuclear wastes as well as stopping leaks in gas mains buried under ground or situated under water. The sealing capacity of the wet powder seal can be augmented by the hydrostatic head of a liquid body established over the seal.

  18. Mesoscale Simulations of Power Compaction

    SciTech Connect

    Lomov, I; Fujino, D; Antoun, T; Liu, B

    2009-08-06

    Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show reshock states above the single-shock Hugoniot line also observed in experiments. They found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations.

  19. Fragmentation and constitutive response of tailored mesostructured aluminum compacts

    NASA Astrophysics Data System (ADS)

    Marquez, Andrew M.; Braithwaite, Christopher H.; Weihs, Timothy P.; Krywopusk, Nicholas M.; Gibbins, David J.; Vecchio, Kenneth S.; Meyers, Marc A.

    2016-04-01

    The fragmentation and constitutive response of aluminum-based compacts were examined under dynamic conditions using mesostructured powder compacts in which the interfaces between the powders (sizes of 40, 100, and 400 μm) were tailored during the swaging fabrication process. Fragmentation was induced in ring samples of this material through explosive loading and was examined through high speed photography, laser interferometry, and soft capture of fragments. Fragment velocities of around 100 m/s were recorded. The fragment mass distributions obtained correlated in general with the interfacial strength of the compacts as well as with the powder size. Experimental results are compared with fragmentation theories to characterize the behavior of reactive powders based on the material's mesostructure by introducing the fracture toughness of the compacts. The mean fragment size is calculated using a modified form of Mott's theory and successfully compared with experimental results.

  20. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  1. Usage Of Polyacetal Powders As Laser Ablation Propulsion Propellants

    NASA Astrophysics Data System (ADS)

    Sasoh, Akihiro; Ogita, Naoya; Sinko, John E.

    2010-05-01

    We examined impulse characteristics of polyoxymeythylene (POM) powders under irradiation by a TEA (Transversely-Excited at Atmospheric pressure) CO2 laser pulse. The impulse performance exhibited large scatter due to splashing particles. When the powder was hydraulically compacted to form a disk, the momentum coupling coefficient became comparable with that for bulk material, but the mass consumption was increased by several times.

  2. A comparison of the sintering of various titanium powders

    SciTech Connect

    Gerdemann, Stephen J.; Alman, David E.

    2005-02-01

    Recently, there has been renewed interest in low-cost titanium. Near-net-shape powder metallurgy offers the potential of manufacturing titanium articles without costly and difficult forming and machining operations; hence, processing methods such as conventional press- and-sinter, powder forging and powder injection molding are of interest. The sintering behavior of a variety of commercial and experimental titanium powders was studied. Commercial powders were acquired that were produced different routes: (i) sponge fines from the primary titanium processing; (ii) via the hydride-dehydride process; and (iii) gas atomization. The influence of vacuum sintering time (0.5 to 32 hrs) and temperature (1200, 1275 or 1350°C) on the microstructure (porosity present) of cold pressed powders was studied. The results are discussed in terms of the difference in powder characteristics; with the aim of identify the characteristics required for full density via press-and-sinter processing. Near-net-shape tensile bars were consolidated via cold pressed and sintered. After sintering, a sub-set of the tensile bars was hot-isostatic pressed (HIPed). The microstructure and properties of the bars were compared in the sintered and HIPed conditions.

  3. Development of powder metallurgy 2XXX series Al alloys for high temperature aircraft structural applications

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1984-01-01

    The objective of the present investigation was to improve the strength and fracture toughness combination of P/M 2124 Al alloys in accordance with NASA program goals for damage tolerance and fatigue resistance. Two (2) P/M compositions based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.12 and 0.60 wt. pct. Zr were selected for investigation. The rapid solidification rates produced by atomization were observed to prohibit the precipitation of coarse, primary Al3Zr in both alloys. A major portion of the Zr precipitated as finely distributed, coherent Al3Zr phases during vacuum preheating and solution heat treatment. The proper balance between Cu and Mg contents eliminated undissolved, soluble constituents such as Al2CuMg and Al2Cu during atomization. The resultant extruded microstructures produced a unique combination of strength and fracture toughness. An increase in the volume fraction of coherent Al3Zr, unlike incoherent Al20Cu2Mn3 dispersoids, strengthened the P/M Al base alloy either directly by dislocation-precipitate interactions, indirectly by a retardation of recrystallization, or a combination of both mechanisms. Furthermore, coherent Al3Zr does not appear to degrade toughness to the extent that incoherent Al20Cu2Mn3 does. Consequently, the addition of 0.60 wt. pct. Zr to the base alloy, incorporated with a 774K (935 F) solution heat treatment temperature, produces an alloy which exceeds all tensile property and fracture toughness goals for damage tolerant and fatigue resistant applications in the naturally aged condition.

  4. Metals for bone implants. Part 1. Powder metallurgy and implant rendering.

    PubMed

    Andani, Mohsen Taheri; Shayesteh Moghaddam, Narges; Haberland, Christoph; Dean, David; Miller, Michael J; Elahinia, Mohammad

    2014-10-01

    New metal alloys and metal fabrication strategies are likely to benefit future skeletal implant strategies. These metals and fabrication strategies were looked at from the point of view of standard-of-care implants for the mandible. These implants are used as part of the treatment for segmental resection due to oropharyngeal cancer, injury or correction of deformity due to pathology or congenital defect. The focus of this two-part review is the issues associated with the failure of existing mandibular implants that are due to mismatched material properties. Potential directions for future research are also studied. To mitigate these issues, the use of low-stiffness metallic alloys has been highlighted. To this end, the development, processing and biocompatibility of superelastic NiTi as well as resorbable magnesium-based alloys are discussed. Additionally, engineered porosity is reviewed as it can be an effective way of matching the stiffness of an implant with the surrounding tissue. These porosities and the overall geometry of the implant can be optimized for strain transduction and with a tailored stiffness profile. Rendering patient-specific, site-specific, morphology-specific and function-specific implants can now be achieved using these and other metals with bone-like material properties by additive manufacturing. The biocompatibility of implants prepared from superelastic and resorbable alloys is also reviewed. PMID:24956564

  5. Effects of temperature on the superplastic characteristics of a powder metallurgy pure aluminum

    SciTech Connect

    Imai, T; Kojima, S.; L`Esperance, G.; Hong, B.D.; Jiang, D.; Nieh, T.G.

    1996-11-15

    High Strain Rate Superplasticity (HSRS) is expected to establish an efficient near-net shape forming process for metal matrix composites and mechanically alloyed(MA) aluminum alloys. It is of interest to clarify the deformation mechanism, because the optimum strain rate at which a maximum elongation of 300--600% is obtained is larger by 10--1,000 times than that of conventional superplastic aluminum alloys. Thus, the deformation mechanism of HSRS materials is thought to be different from that of conventional alloys. The purpose of this study is to develop a thermomechanical process to produce superplasticity at high strain rate (HSRS) for 1N90 pure aluminum, and also to examine the deformation mechanism of the HSRS.

  6. Evaluation of powder metallurgy plates made by Sylvania Electric Products, Inc.

    SciTech Connect

    Not Available

    1994-09-01

    These plates, numbered 13129, 13130, 13133, 13137, and 13146 were fabricated by Sylvania Electric Products, Inc., and were received at the Savannah plant in February, 1956. All of the plates were of the wide, ribless design. A summary of the data obtained by Sylvania on these and on {open_quotes}companion{close_quotes} plates is given in Table I, and a summary of the data obtained upon examining the plates at the Savannah River Laboratory is contained in Table II.

  7. Grain-shape parameters for high-temperature creep resistance in powder metallurgy tungsten fine wires

    SciTech Connect

    Tanoue, K.

    1998-02-01

    Three grain-shape parameters, f{sub 1}, f{sub 2}, and f{sub 3}, are defined to clarify the morphological effect of grains on the high-temperature creep resistance under the condition that no grain boundary cavitation occurs. The parameter f{sub 1} is characteristic of complicated grain shapes, suggesting that it can be a measure of the interlocking grain structure. The parameter f{sub 2} is an important parameter when torsional stresses are imposed on coiled wires, and f{sub 3} is characteristic of the short-range roughness of grain boundaries only when f{sub 1} is not greatly changed. The minimum creep rate decreases as the grain aspect ratio, R, increases for R < 30, and the creep rate increases as R increases for R > 30. The parameter f{sub 1}, as well as Raj and Ashby`s model, gives a satisfactory explanation for the former behavior. On the other hand, it is proven that their model must be modified using f{sub 3} to explain the latter behavior because of the highly elongated grain configuration that is associated with R > 30.

  8. Ductilization of Mo-Si solid solutions manufactured by powder metallurgy

    SciTech Connect

    Saage, H.; Krueger, M.; Sturm, D.; Heilmaier, M.; Schneibel, J H; George, Easo P; Heatherly Jr, Lee; Somsen, Ch.; Eggeler, G.; Yang, Ying

    2009-01-01

    Mo-1.5 at.% Si alloys with additions of either Y{sub 2}O{sub 3} or Zr were manufactured by mechanical alloying. The Y{sub 2}O{sub 3} particles reduced the grain size and increased the room temperature strength, but did not alleviate the brittleness of previously investigated Mo-1.5 at.% Si without Y{sub 2}O{sub 3}. Additions of Zr, on the other hand, resulted not only in a fine grain size and an extremely high bend strength ({approx}2 GPa), but also in limited bend ductility at room temperature. Zr additions are seen to be beneficial for three reasons. First, Zr reduces the grain size. Second, Zr getters detrimental oxygen by forming ZrO{sub 2} particles (which in turn help to pin the grain boundaries). Third, in situ Auger analysis shows that Zr reduces the concentration of Si segregated at the grain boundaries. This is thought to enhance the grain boundary cohesive strength and thus leads to the observed ductility.

  9. Superplastic behavior at high strain rate of rapidly solidified powder metallurgy Al-Li alloy

    SciTech Connect

    Zhongqi Cui; Wang Zhong; Qingbin Wei . Dept. of Metals and Technology)

    1994-01-01

    A number of studies which reveal that superplasticity can sometimes occur at an extremely high strain rate (> 10[sup [minus]1]s[sup [minus]1]) have been reported in several classes of materials, including metal-matrix composites and mechanically-alloyed (MA) materials. Since multiphase aluminum alloys processed by rapid solidification techniques can have fine stable grains, the interest in the superplastic behavior of these alloys increased sharply. Some tests indicated that rapid solidification processed (RSP) aluminum alloys can exhibit superplastic behavior, but nearly all optimum strain rate in above experiments are relatively low. In this paper, high strain rate superplasticity of rapid solidification processed Al-Li alloy has been researched. It is demonstrated that a maximum elongation of 250% is obtained at a high strain rate of 1.4 [times] 10[sup [minus]1]s[sup [minus]1] at 570 C, which is above the solidus temperature of 562 C.

  10. Development of BCC/BCC (matrix/fiber) nanostructures by powder metallurgy techniques

    SciTech Connect

    Jablonski, P.D.; Lee, P.J.; Larbalestier, D.C.

    1994-12-31

    It is well known that FCC/BCC and FCC/FCC composites develop anomalous strength upon the application of large deformation strains, well beyond that predicted by the rule of mixtures. These results have been interpreted in terms of the fine-scale microstructures that are produced, normally from mutually insoluble components. Recently the authors have developed a process for creating artificial two-phase nanostructures from materials which are soluble in both the liquid and solid states. They discuss the process and relate the microstructure to the composite hardness as the structure is refined from the micrometer through manometer scales. The dependence of the hardening rate on the amount of second phase is described.

  11. SiC particle cracking in powder metallurgy processed aluminum matrix composite materials

    SciTech Connect

    Wang, B.; Janowski, G.M.; Patterson, B.R.

    1995-09-01

    Particle cracking is one of the key elements in the fracture process of particulate-reinforced metal-matrix composite (MMC) materials. The present study quantitatively examined the amount of new surface are created by particle cracking and the number fraction of cracked particles in a series of SiC-reinforced aluminum-matrix composite materials. These composite materials were fabricated by liquid-phase sintering and contained 9 vol pct of 23, 63, or 142 {micro}m SiC. The matrix properties were varied by heat treating to either an underaged or peak-aged condition. In general, the new surface area created by particle cracking (S{sub V}) and the number fraction of cracked particles (F{sub no}) were linearly dependent on the local strain along the tensile specimen. Multiple cracks were frequently observed in the composites containing large particles. It was found that the new surface area created by particle cracking per unit strain was higher for the case of high-strength matrices and was not systematically affected by particle size within the range studied. The number fraction of cracked particles was affected by both particle size and matrix strength. A higher number fraction of particles cracked in the composites reinforced with large particles and with high matrix yield strengths. These results are interpreted in terms of the size of the particle defects, which is a function of particle size, and the critical flaw size necessary to crack a given particle, which is a function of the stress on the particle. The new surface area created by cracking and the fraction of cracked particles were related and are in good agreement for the large and medium sized particles.

  12. Effect of thermally induced porosity on an as-HIP powder metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1979-01-01

    The impact of thermally induced porosity on the mechanical properties of an as-hot-isostatically-pressed and heat treated pressing made from low carbon Astroloy was determined. Porosity in the disk-shape pressing studied ranged from 2.6 percent at the bore to 1.4 percent at the rim. Tensile, yield strength, ductility, and rupture life of the rim of the porous pressing was only slightly inferior to the rim of sound pressings. The strength, ductility, and rupture life of the bore of the porous pressing was severely degraded compared to sound pressings. At strain ranges typical of commercial jet engine designs, the rim of the porous pressing had slightly inferior fatigue life to sound pressings.

  13. Development of powder metallurgy Al alloys for high temperature aircraft structural applications, phase 2

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1982-01-01

    In this continuing study, the development of mechanically alloyed heat resistant aluminum alloys for aircraft were studied to develop higher strength targets and higher service temperatures. The use of higher alloy additions to MA Al-Fe-Co alloys, employment of prealloyed starting materials, and higher extrusion temperatures were investigated. While the MA Al-Fe-Co alloys exhibited good retention of strength and ductility properties at elevated temperatures and excellent stability of properties after 1000 hour exposure at elevated temperatures, a sensitivity of this system to low extrusion strain rates adversely affected the level of strength achieved. MA alloys in the Al-Li family showed excellent notched toughness and property stability after long time exposures at elevated temperatures. A loss of Li during processing and the higher extrusion temperature 482 K (900 F) resulted in low mechanical strengths. Subsequent hot and cold working of the MA Al-Li had only a mild influence on properties.

  14. Application of powder metallurgy techniques for the development of non-toxic ammunition. Final CRADA report

    SciTech Connect

    Lowden, R.; Kelly, R.

    1997-05-30

    The purpose of the Cooperative Research and Development Agreement (CRADA) between Martin Marietta Energy Systems, Inc., and Delta Frangible Ammunition (DFA), was to identify and evaluate composite materials for the development of small arms ammunition. Currently available small arms ammunition utilizes lead as the major component of the projectile. The introduction of lead into the environment by these projectiles when they are expended is a rapidly increasing environmental problem. At certain levels, lead is a toxic metal to the environment and a continual health and safety concern for firearm users as well as those who must conduct lead recovery operations from the environment. DFA is a leading supplier of high-density mixtures, which will be used to replace lead-based ammunition in specific applications. Current non-lead ammunition has several limitations that prevent it from replacing lead-based ammunition in many applications (such as applications that require ballistics, weapon recoil, and weapon function identical to that of lead-based ammunition). The purpose of the CRADA was to perform the research and development to identify cost-effective materials to be used in small arms ammunition that eventually will be used in commercially viable, environmentally conscious, non-lead, frangible and/or non-frangible, ammunition.

  15. Aging of powder metallurgy N14K7M5T2 maraging steel

    SciTech Connect

    Antsiferov, V.N.; Grevnov, L.M.; Maslenikov, N.N.

    1985-04-01

    The authors study the aging process of sintered N14K7M5T2 marging steel at temperatures of 460-590 C with an isothermal hold of 40 min to 10 h. Electron microscopy was used. The purpose of the investigations was establishment of the type of precipitated phases and their size, form, and kinetics of growth in relation to the aging cycles. An analysis of the electrondiffraction patterns of specimens aged under different conditions made it possible to identify Ni/sub 3/ Ti as the hardening phase.

  16. Effect of the Machining Processes on Low Cycle Fatigue Behavior of a Powder Metallurgy Disk

    NASA Technical Reports Server (NTRS)

    Telesman, J.; Kantzos, P.; Gabb, T. P.; Ghosn, L. J.

    2010-01-01

    A study has been performed to investigate the effect of various machining processes on fatigue life of configured low cycle fatigue specimens machined out of a NASA developed LSHR P/M nickel based disk alloy. Two types of configured specimen geometries were employed in the study. To evaluate a broach machining processes a double notch geometry was used with both notches machined using broach tooling. EDM machined notched specimens of the same configuration were tested for comparison purposes. Honing finishing process was evaluated by using a center hole specimen geometry. Comparison testing was again done using EDM machined specimens of the same geometry. The effect of these machining processes on the resulting surface roughness, residual stress distribution and microstructural damage were characterized and used in attempt to explain the low cycle fatigue results.

  17. Utilization of Space Shuttle External Tank materials by melting and powder metallurgy

    NASA Technical Reports Server (NTRS)

    Chern, T. S.

    1985-01-01

    The Crucible Melt Extraction Process was demonstrated to convert scraps of aluminum alloy 2219, used in the Space Shuttle External Tank, into fibers. The cast fibers were then consolidated by cold welding. The X-ray diffraction test of the cast fibers was done to examine the crystallinity and oxide content of the fibers. The compressive stress-strain behavior of the consolidated materials was also examined. Two conceptual schemes which would adapt the as-developed Crucible Melt Extraction Process to the microgravity condition in space were finally proposed.

  18. Stress corrosion evaluation of powder metallurgy aluminum alloy 7091 with the breaking load test method

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.

    1987-01-01

    The stress corrosion behavior of the P/M aluminum alloy 7091 is evaluated in two overaged heat treatment conditions, T7E69 and T7E70, using an accelerated test technique known as the breaking load test method. The breaking load data obtained in this study indicate that P/M 7091 alloy is highly resistant to stress corrosion in both longitudinal and transverse orientations at stress levels up to 90 percent of the material yield strength. The reduction in mean breaking stress as a result of corrosive attack is smallest for the more overaged T7E70 condition. Details of the test procedure are included.

  19. Effects of thermally induced porosity on an as-HIP powder metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Miner, R. V., Jr.

    1980-01-01

    The effect of thermally induced porosity on the mechanical properties of an as-hot-isostatically pressed and heat-treated pressing made from low carbon Astroloy is examined. Tensile, stress-rupture, creep, and low cycle fatigue tests were performed and the results were compared with industrial acceptance criteria. It is shown that the porous pressing has a porosity gradient from the rim to the bore with the bore having 1-1/2% greater porosity. Mechanical properties of the test ring below acceptance level are tensile reduction in area at room temperature and 538 C and time for 0.1% creep at 704 C. It is also found that the strength, ductility, and rupture life of the rim are slightly inferior to those of the rim of the sound pressings, while those of the bore are generally below the acceptable level. At strain ranges typical of commercial aircraft engines, the low cycle fatigue life of the rim of the porous pressings is slightly lower than that of the sound pressings.

  20. Electrochemical cell with powdered electrically insulative material as a separator

    DOEpatents

    Mathers, James P.; Olszanski, Theodore W.; Boquist, Carl W.

    1978-01-01

    A secondary electrochemical cell includes electrodes separated by a layer of electrically insulative powder. The powder includes refractory materials selected from the oxides and nitrides of metals and metaloids. The powdered refractory material, blended with electrolyte particles, can be compacted in layers with electrode materials to form an integral electrode structure or separately assembled into the cell. The assembled cell is heated to operating temperature leaving porous layers of electrically insulative, refractory particles, containing molten electrolyte between the electrodes.

  1. Powder lubrication of faults by powder rolls in gouge zones

    NASA Astrophysics Data System (ADS)

    Chen, X.; Madden, A. S.; Reches, Z.

    2013-12-01

    Powder-lubrication by fault gouge can be an effective mechanism of dynamic weakening of faults (Reches & Lockner, 2010); however, the physical mechanisms of this lubrication are poorly understood. While the flow of coarse-grained (> 100 ?m) materials, e.g. glass beads or quartz sand, was extensively studied, the flow of fine-grained (< 1 ?m) powders, e.g., fault-gouge and nano-powders, have remained enigmatic. We report here experimental results of a new efficient mechanism for powder lubrication. We conducted friction tests on high-velocity rotary shear apparatus (Reches & Lockner, 2010). Two types of experimental faults were tested: (1) faults made of solid, igneous rocks (granite, tonalite and diorite); and (2) fault-zones made of 2-3 mm thick layer of granular materials (oolites, calcite or gypsum) sheared in a confined cell. We performed 21 runs with total slip of 0.14-13 m, normal stress of 1.2-14.5 MPa, slip velocity of 0.012-0.97 m/s. The ultra-microscopic (SEM and AFM) analysis of the experimental slip surfaces revealed two outstanding features in 17 out of the 21 experiments: (1) localized fault-slip along Principal Slip Zones (PSZs) that are composed of a dense, shiny, cohesive crust, 0.5-1 micron thick, that overlaid a porous substrate, and (2) elongated rolls composed of gouge-powder into three-dimensional structures of closely-packed powder grains, (20-50 nm in size). The rolls are cylindrical, 0.75-1.4 micron wide, and 1.7-30 micron long, with smooth outer surface, and laminated, concentric layers of compacted grains. The rolls were exclusively found on the PSZs. Many rolls were destroyed fracturing and smearing on the PSZ, suggesting that the rolls underwent a life cycle of formation and destruction. Significant macroscopic friction reduction was measured in experiments with observed rolls, and no (or minor) friction reduction in the four experiments without rolls. The final, reduced friction coefficients have a general reciprocal relation to the rolls surface coverage, suggesting that increased development of rolls (= increasing surface coverage) enhanced fault weakening. We applied the Eldredge and Tabor (1955) model for rolling friction to the AFM observed morphology of the rolls and PSZs, and found good agreement between measured and modeled friction coefficients. We conclude that the measured friction reduction reflects a transition from sliding-dominated slip to rolling-dominated slip due to the presence and density of powder rolls. We further argue that powder rolling is an effective mechanism of powder lubrication, and that spontaneous growth of such rolls along crustal faults is likely to control earthquake weakening.

  2. Improved compaction of dried tannery wastewater sludge.

    PubMed

    Della Zassa, M; Zerlottin, M; Refosco, D; Santomaso, A C; Canu, P

    2015-12-01

    We quantitatively studied the advantages of improving the compaction of a powder waste by several techniques, including its pelletization. The goal is increasing the mass storage capacity in a given storage volume, and reducing the permeability of air and moisture, that may trigger exothermic spontaneous reactions in organic waste, particularly as powders. The study is based on dried sludges from a wastewater treatment, mainly from tanneries, but the indications are valid and useful for any waste in the form of powder, suitable to pelletization. Measurements of bulk density have been carried out at the industrial and laboratory scale, using different packing procedures, amenable to industrial processes. Waste as powder, pellets and their mixtures have been considered. The bulk density of waste as powder increases from 0.64 t/m(3) (simply poured) to 0.74 t/m(3) (tapped) and finally to 0.82 t/m(3) by a suitable, yet simple, packing procedure that we called dispersion filling, with a net gain of 28% in the compaction by simply modifying the collection procedure. Pelletization increases compaction by definition, but the packing of pellets is relatively coarse. Some increase in bulk density of pellets can be achieved by tapping; vibration and dispersion filling are not efficient with pellets. Mixtures of powder and pellets is the optimal packing policy. The best compaction result was achieved by controlled vibration of a 30/70 wt% mixture of powders and pellets, leading to a final bulk density of 1t/m(3), i.e. an improvement of compaction by more than 54% with respect to simply poured powders, but also larger than 35% compared to just pellets. That means increasing the mass storage capacity by a factor of 1.56. Interestingly, vibration can be the most or the least effective procedure to improve compaction of mixtures, depending on characteristics of vibration. The optimal packing (30/70 wt% powders/pellets) proved to effectively mitigate the onset of smouldering, leading to self-heating, according to standard tests, whereas the pure pelletization totally removes the self-heating hazard. PMID:26337963

  3. Powder treatment process

    DOEpatents

    Weyand, John D.

    1988-01-01

    (1) A process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder.

  4. Powder treatment process

    DOEpatents

    Weyand, J.D.

    1988-02-09

    Disclosed are: (1) a process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder. 2 figs.

  5. Compact magnetograph

    NASA Technical Reports Server (NTRS)

    Title, A. M.; Gillespie, B. A.; Mosher, J. W.

    1982-01-01

    A compact magnetograph system based on solid Fabry-Perot interferometers as the spectral isolation elements was studied. The theory of operation of several Fabry-Perot systems, the suitability of various magnetic lines, signal levels expected for different modes of operation, and the optimal detector systems were investigated. The requirements that the lack of a polarization modulator placed upon the electronic signal chain was emphasized. The PLZT modulator was chosen as a satisfactory component with both high reliability and elatively low voltage requirements. Thermal control, line centering and velocity offset problems were solved by a Fabry-Perot configuration.

  6. Canning Of Powdered Metal For Hot Isostatic Pressing

    NASA Technical Reports Server (NTRS)

    Juhas, John J.

    1989-01-01

    Quality of specimen enhanced by improved canning process. Method developed for canning specimens for hot isostatic pressing. Specimen placed inside refractory-metal ring, then sandwiched between two refractory-metal face sheets. Assembly placed inside die, then positioned in vacuum hot press. Heated to set temperature at prescribed vacuum to burn off all of binder in specimen. Advantages: powder-metallurgy composite totally purged of binder sealed in can in single operation, maintains size, shape, and uniformity of specimen. Weld region does not recrystallize, and little possibility of cracking.

  7. Plasma preparation and low-temperature sintering of spherical TiC-Fe composite powder

    NASA Astrophysics Data System (ADS)

    Wang, Jian-jun; Hao, Jun-jie; Guo, Zhi-meng; Wang, Song

    2015-12-01

    A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced using a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense structure, and the fine sub-micron TiC particles were homogeneously distributed in the α-Fe matrix. A TiC-Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature; the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

  8. Direct measurements of temperature-dependent laser absorptivity of metal powders.

    PubMed

    Rubenchik, A; Wu, S; Mitchell, S; Golosker, I; LeBlanc, M; Peterson, N

    2015-08-20

    A compact system is developed to measure laser absorptivity for a variety of powder materials (metals, ceramics, etc.) with different powder size distributions and thicknesses. The measured results for several metal powders are presented. The results are consistent with those from ray tracing calculations. PMID:26368757

  9. Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior.

    PubMed

    Xu, J L; Khor, K A; Gu, Y W; Kumar, R; Cheang, P

    2005-05-01

    The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results showed that the HA feedstock decomposed after rf plasma processing. Crystalline HA, alpha-tri-calcium phosphate (alpha-TCP), tetra-calcium phosphate (TTCP) and calcium oxide (CaO) were detected in the plasma-spheroidized powders. Raman spectra results indicated strong presence of amorphous calcium phosphate (ACP) in the spheroidized powders. The particle size distribution and specific surface area were influenced through the rf plasma working plate power levels. The sintering behavior of the rf plasma synthesized powders was analyzed through the SPS process and the results indicated that the spheroidized powders commence sintering at approximately 900 degrees C and through to 1150 degrees C. After sintering above 1100 degrees C for 3min, the relative densities of the SPS compacts reached 96% of the theoretical value. The SPS compacts were immersed in simulated body fluids (SBF) for different durations and the results confirmed their bioactivities. PMID:15585221

  10. The physical metallurgy of mechanically-alloyed, dispersion-strengthened Al-Li-Mg and Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Gilman, P. S.

    1984-01-01

    Powder processing of Al-Li-Mg and Al-Li-Cu alloys by mechanical alloying (MA) is described, with a discussion of physical and mechanical properties of early experimental alloys of these compositions. The experimental samples were mechanically alloyed in a Szegvari attritor, extruded at 343 and 427 C, and some were solution-treated at 520 and 566 C and naturally, as well as artificially, aged at 170, 190, and 210 C for times of up to 1000 hours. All alloys exhibited maximum hardness after being aged at 170 C; lower hardness corresponds to the solution treatment at 566 C than to that at 520 C. A comparison with ingot metallurgy alloys of the same composition shows the MA material to be stronger and more ductile. It is also noted that properly aged MA alloys can develop a better combination of yield strength and notched toughness at lower alloying levels.

  11. Preparation of metal diboride powders

    DOEpatents

    Brynestad, J.; Bamberger, C.E.

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group of consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  12. Preparation of titanium diboride powder

    SciTech Connect

    Brynestad, J.; Bamberger, C.E.

    1985-03-05

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  13. Preparation of titanium diboride powder

    DOEpatents

    Brynestad, Jorulf; Bamberger, Carlos E.

    1985-01-01

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  14. Polymer quenched prealloyed metal powder

    DOEpatents

    Hajaligol, Mohammad R.; Fleischhauer, Grier; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3 % Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  15. Contrasting lead speciation in forest and tilled soils heavily polluted by lead metallurgy.

    PubMed

    Ettler, Vojtech; Vanek, Ales; Mihaljevic, Martin; Bezdicka, Petr

    2005-03-01

    The concentration trends and chemical fractionation of Pb was studied in eight tilled and forest soil profiles heavily polluted by Pb metallurgy in the Pribram district, Czech Republic. The highest Pb concentrations were observed in surface and subsurface horizons attaining 35,300 mg kg-1 in forest soils and 1233 mg kg-1 in tilled soils. Total Pb concentrations were one order of magnitude lower in tilled soil due to intensive ploughing and annual crop off-take. The results of the Tessier sequential extraction procedure showed the preferential binding of Pb in forest soils to operationally-defined exchangeable positions and soil organic matter (oxidisable fraction). The Pb exchangeable fraction is thought to correspond to weak electrostatic binding on the functional groups of organic matter. In tilled soil, Pb is predominantly bound to operationally-defined Fe and Mn oxides (reducible fraction). A comparison with the background Pb concentration values showed a strong contamination even in mineral horizons IIC and confirmed a strong vertical mobility of Pb within the soil profiles. The calculated mobility factors (MF) showed that up to 72% of Pb is mobile and bioavailable in forest soils. In contrast, the bioavailability of Pb in tilled soils was significantly lower as the MF accounted for up to 30%. In the most polluted horizon of forest soil profile, the X-ray powder diffraction (XRPD) analysis confirmed the presence of anglesite (PbSO4), derived likely from the smelter emissions. PMID:15686764

  16. Technology Selections for Cylindrical Compact Fabrication

    SciTech Connect

    Jeffrey A. Phillips

    2010-10-01

    A variety of process approaches are available and have been used historically for manufacture of cylindrical fuel compacts. The jet milling, fluid bed overcoating, and hot press compacting approach being adopted in the U.S. AGR Fuel Development Program for scale-up of the compacting process involves significant paradigm shifts from historical approaches. New methods are being pursued because of distinct advantages in simplicity, yield, and elimination of process mixed waste. Recent advances in jet milling technology allow simplified dry matrix powder preparation. The matrix preparation method is well matched with patented fluid bed powder overcoating technology recently developed for the pharmaceutical industry and directly usable for high density fuel particle matrix overcoating. High density overcoating places fuel particles as close as possible to their final position in the compact and is matched with hot press compacting which fully fluidizes matrix resin to achieve die fill at low compacting pressures and without matrix end caps. Overall the revised methodology provides a simpler process that should provide very high yields, improve homogeneity, further reduce defect fractions, eliminate intermediate grading and QC steps, and allow further increases in fuel packing fractions.

  17. Process for synthesizing compounds from elemental powders and product

    DOEpatents

    Rabin, Barry H.; Wright, Richard N.

    1993-01-01

    A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe.sub.3 Al and FeAl.

  18. Compact Reactor

    SciTech Connect

    Williams, Pharis E.

    2007-01-30

    Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date.

  19. Strength, acoustic evaluation and metallurgy of diffusion bonds

    SciTech Connect

    Buck, O.; Ojard, G.C.

    1993-10-01

    This paper discusses our efforts on two model systems to determine the bond strength, its correlation to acoustic NDE and the metallurgy involved in the process. Results indicate that the total acoustic energy, reflected from the original interface, can differentiate between the various bond strengths achieved. However, depending on types of materials to be joined, the atomistic processes, leading to a variety of microstructures in the bond planes, can become quite complex and strongly dominate the mechanical properties of such bonds. Origin of failure initiating defects is discussed.

  20. Welding Metallurgy and Processing Issues for Joining of Power Sources

    SciTech Connect

    Lienert, Thomas J.; Reardon, Patrick T.

    2012-08-14

    Weldability issues with the pertinent alloys have been reviewed and preliminary results of our work on Haynes 25 have been presented. Further results on the mechanical properties and metallography on the EB welds are imminent. Hot-ductility experiments will commence within a few weeks. Aging studies on the effects of heat treatment using the Gleeble are also planned. MST-6 has extensive background in the welding metallurgy of the pertinent alloys. We also have considerable experience with the various welding processes to be used.

  1. NanoComposite Stainless Steel Powder Technologies

    SciTech Connect

    DeHoff, R.; Glasgow, C.

    2012-07-25

    Oak Ridge National Laboratory has been investigating a new class of Fe-based amorphous material stemming from a DARPA, Defense Advanced Research Projects Agency initiative in structural amorphous metals. Further engineering of the original SAM materials such as chemistry modifications and manufacturing processes, has led to the development of a class of Fe based amorphous materials that upon processing, devitrify into a nearly homogeneous distribution of nano sized complex metal carbides and borides. The powder material is produced through the gas atomization process and subsequently utilized by several methods; laser fusing as a coating to existing components or bulk consolidated into new components through various powder metallurgy techniques (vacuum hot pressing, Dynaforge, and hot isostatic pressing). The unique fine scale distribution of microstructural features yields a material with high hardness and wear resistance compared to material produced through conventional processing techniques such as casting while maintaining adequate fracture toughness. Several compositions have been examined including those specifically designed for high hardness and wear resistance and a composition specifically tailored to devitrify into an austenitic matrix (similar to a stainless steel) which poses improved corrosion behavior.

  2. 78 FR 8202 - Meeting of the Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-05

    ... ACRS meetings were published in the Federal Register on October 18, 2012, (77 FR 64146- 64147... Hydraulic Phenomena and Materials, Metallurgy and Reactor Fuels; Notice of Meeting The Joint ACRS Subcommittees on Thermal Hydraulic Phenomena and Materials, Metallurgy and Reactor Fuels will hold a meeting...

  3. 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.

  4. Composite powder particles

    NASA Technical Reports Server (NTRS)

    Parker, Donald S. (Inventor); MacDowell, Louis G. (Inventor)

    2009-01-01

    A liquid coating composition including a coating vehicle and composite powder particles disposed within the coating vehicle. Each composite powder particle may include a magnesium component, a zinc component, and an indium component.

  5. Precision powder feeder

    DOEpatents

    Schlienger, M. Eric; Schmale, David T.; Oliver, Michael S.

    2001-07-10

    A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

  6. A DEM contact model for history-dependent powder flows

    NASA Astrophysics Data System (ADS)

    Hashibon, Adham; Schubert, Raphael; Breinlinger, Thomas; Kraft, Torsten

    2016-01-01

    Die filling is an important part of the powder handling process chain that greatly influences the characteristic structure and properties of the final part. Predictive modelling and simulation of the die-filling process can greatly contribute to the optimization of the part and the whole production procedure, e.g. by predicting the resulting powder compaction structure as a function of filling process parameters. The rheology of powders can be very difficult to model especially if heterogeneous agglomeration or time-dependent consolidation effects occur. We present a new discrete element contact force model that enables modelling complex powder flow characteristics including direct time-dependent consolidation effects and load history-dependent cohesion to describe the filling process of complex, difficult to handle powders. The model is demonstrated for simple flow and an industrial powder flow.

  7. Amorphous powders of Al-Hf prepared by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

    1988-01-01

    We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

  8. Hydroxyapatite ceramics from hydrothermally prepared powders

    SciTech Connect

    Lin, C.H.; Huang, C.W.; Chang, S.C.

    1994-12-31

    Hydroxyapatite (Ca{sub 5}(PO{sub 4}){sub 3}(OH)) is an effective material for artificial human bone production. Hydroxyapatite powders were hydrothermally produced in this work by reacting Ca(OH){sub 2} with Na{sub 3}PO{sub 4}{center_dot}12H{sub 2}O in an autoclave at various temperature and for various times. The particle size of hydroxyapatite was observed to be very fine, uniform, around 50 nm, as well as independent of reaction time. The hydroxyapatite powders were compacted and sintered at various temperatures for 2 hrs. The density, grain size, and hardness of the hydroxyapatite ceramics were measured and compared with those of the hydroxyapatite ceramics produced by the powders from the commercial source. The hydroxyapatite ceramics from the hydrothermal powders were found to have a higher density, smaller grain size, and higher hardness. After the hydroxyapatite ceramics were dipped in a simulated biological body liquid for 10 days, the density and hardness of the hydroxyapatite ceramics from the hydrothermal powders were less deteriorated than those of the hydroxyapatite ceramics from the commercial powder.

  9. The mysterious world of plutonium metallurgy: Past and future

    SciTech Connect

    Hecker, S.S.; Hammel, E.F.

    1998-12-31

    The first atomic bomb detonated at the Trinity Site in New Mexico on July 16, 1945, used plutonium, a man-made element discovered < 5 yr earlier. The story of how Manhattan Project scientists and engineers tackled the mysteries of this element and fabricated it into the first atomic bomb is one of the most fascinating in the history of metallurgy and materials. The authors are currently trying to generate renewed interest in plutonium metallurgy because of the challenge posed by President Clinton, i.e., to keep the nuclear stockpile of weapons safe and reliable without nuclear testing. The stockpile stewardship challenge requires either a lifetime extension of the plutonium components or a remanufacture--neither of which can be verified by testing. In turn, this requires that one achieve a better fundamental understanding of plutonium. Of special interest is the effect of self-irradiation on the properties and on the long-term stability of plutonium and its alloys. Additional challenges arise from long-term concerns about disposing of plutonium and dealing with its environmental legacy. It is imperative to interest the next generation of students in these plutonium challenges.

  10. SGC Tests for Influence of Material Composition on Compaction Characteristic of Asphalt Mixtures

    PubMed Central

    Chen, Qun

    2013-01-01

    Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture) was studied using Superpave gyratory compactor (SGC) simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes. PMID:23818830

  11. SGC tests for influence of material composition on compaction characteristic of asphalt mixtures.

    PubMed

    Chen, Qun; Li, Yuzhi

    2013-01-01

    Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture) was studied using Superpave gyratory compactor (SGC) simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes. PMID:23818830

  12. Compaction by impact of unconsolidated lunar fines

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.

    1975-01-01

    An investigation was conducted concerning the macroscopic irreversible partial compaction of terrestrial or lunar fines. A sample material (70051), assumed to be typical of the fines in the unconsolidated material of the lunar regolith, was used in the experiments. Tests were also carried out with powdered Vacaville basalt. Release adiabate and Hugoniot measurements were conducted. It was found that the dynamic stresses required for irreversible compaction of lunar fines on the moon are significantly lower than the values inferred from the shock recovery experiments conducted by Christie et al. (1973).

  13. Agglomeration of food powder and applications.

    PubMed

    Dhanalakshmi, K; Ghosal, S; Bhattacharya, S

    2011-05-01

    Agglomeration has many applications in food processing and major applications include easy flow table salt, dispersible milk powder and soup mix, instant chocolate mix, beverage powder, compacted cubes for nutritional-intervention program, health bars using expanded/puffed cereals, etc. The main purpose of agglomeration is to improve certain physical properties of food powders such as bulk density, flowability, dispersability, and stability. Agglomerated products are easy to use by the consumers and hence are preferred over the traditional non-agglomerated products that are usually non-flowable in nature. The properties of food agglomerates and the process of agglomeration like employing pressure, extrusion, rewetting, spray-bed drying, steam jet, heat/sintering, and binders have been reviewed. The physical and instant properties of agglomerated food products have also been discussed. PMID:21491268

  14. Effects of physical properties for starch acetate powders on tableting.

    PubMed

    Korhonen, Ossi; Pohja, Seppo; Peltonen, Soili; Suihko, Eero; Vidgren, Mika; Paronen, Petteri; Ketolainen, Jarkko

    2002-01-01

    The aim of the study was to investigate particle and powder properties of various starch acetate powders, to study the effect of these properties on direct compression characteristics, and to evaluate the modification opportunity of physical properties for starch acetate powders by using various drying methods. At the end of the production phase of starch acetate, the slurry of starch acetate was dried using various techniques. Particle, powder, and tableting properties of end products were investigated. Particle size, circularity, surface texture, water content and specific surface area varied according to the particular drying method of choice. However, all powders were freely flowing. Bulk and tapped densities of powders varied in the range of 0.29 to 0.44 g/cm3 and 0.39 to 0.56 g/cm3, respectively. Compaction characteristics revealed that all powders were easily deformed under compression, having yield pressure values of less than 66 MPa according to Heckel analysis. All powders possessed a significant interparticulate bond-forming capacity during compaction. The tensile strength values of tablets varied between 10 and 18 MPa. In conclusion, physical properties of starch acetate could be affected by various drying techniques. A large specific surface area and water content above 4% were favorable properties by direct compression, especially for small, irregular, and rough particles. PMID:12916928

  15. Usage Of Polyacetal Powders As Laser Ablation Propulsion Propellants

    SciTech Connect

    Sasoh, Akihiro; Ogita, Naoya; Sinko, John E.

    2010-05-06

    We examined impulse characteristics of polyoxymeythylene (POM) powders under irradiation by a TEA (Transversely-Excited at Atmospheric pressure)CO{sub 2} laser pulse. The impulse performance exhibited large scatter due to splashing particles. When the powder was hydraulically compacted to form a disk, the momentum coupling coefficient became comparable with that for bulk material, but the mass consumption was increased by several times.

  16. Processing of PZT ceramics: aqueous mixing procedures for powder consolidation

    SciTech Connect

    Bunker, B.C.; Lamppa, D.L.; Moore, R.H.

    1986-02-01

    Inhomogeneities in chemical compositions and microstructures can result in lot-to-lot variations in the charge release characteristics of ferroelectric lead-zirconate-titanate ceramics. One source of inhomogeneity is agglomeration and selective sedimentation which occurs during aqueous mixing of the constituent oxides. Procedures using electrostatic and steric stabilization of oxide powders were developed for fabricating homogeneous powder compacts. Use of lead carbonate instead of lead oxide minimizes problems encountered using various slurry stabilization techniques.

  17. Mechanical properties and shear failure surfaces of two alumina powders in triaxial compression

    SciTech Connect

    ZEUCH,DAVID H.; GRAZIER,J. MARK; ARGUELLO JR.,JOSE G.; EWSUK,KEVIN G.

    2000-04-24

    In the manufacture of ceramic components, near-net-shape parts are commonly formed by uniaxially pressing granulated powders in rigid dies. Density gradients that are introduced into a powder compact during press-forming often increase the cost of manufacturing, and can degrade the performance and reliability of the finished part. Finite element method (FEM) modeling can be used to predict powder compaction response, and can provide insight into the causes of density gradients in green powder compacts; however, accurate numerical simulations require accurate material properties and realistic constitutive laws. To support an effort to implement an advanced cap plasticity model within the finite element framework to realistically simulate powder compaction, the authors have undertaken a project to directly measure as many of the requisite powder properties for modeling as possible. A soil mechanics approach has been refined and used to measure the pressure dependent properties of ceramic powders up to 68.9 MPa (10,000 psi). Due to the large strains associated with compacting low bulk density ceramic powders, a two-stage process was developed to accurately determine the pressure-density relationship of a ceramic powder in hydrostatic compression, and the properties of that same powder compact under deviatoric loading at the same specific pressures. Using this approach, the seven parameters that are required for application of a modified Drucker-Prager cap plasticity model were determined directly. The details of the experimental techniques used to obtain the modeling parameters and the results for two different granulated alumina powders are presented.

  18. Low temperature fabrication from nano-size ceramic powders

    SciTech Connect

    Gonzalez, E.J.; Piermarini, G.J.; Hockey, B.

    1995-06-01

    The objective of the compaction process is to produce a dense green-state compact from a nanosize powder that subsequently can be sintered at high temperatures to form a dense ceramic piece. High density in the green-state after pressing is of primary importance for achieving high densities after sintering. Investigation of the compaction behavior of ceramic powders, therefore, is an important part of characterization of raw ceramic powders and evaluation of their compaction behavior, analysis of interaction between particles, and the study of microstructure of green body (unsintered) during pressure-forming processes. The compaction of nanosize ceramic particles into high density green bodies is very difficult. For the nanosize materials used in this study (amorphous Si{sub 3}N{sub 4} and {gamma} Al{sub 2}O{sub 3}), there is no evidence by TEM of partial sintering after synthesis. Nevertheless, strong aggregation forces, such as the van der Waals surface forces of attraction, exist and result in moderate precursor particle agglomeration. More importantly, these attractive surface forces, which increase in magnitude with decreasing particle size, inhibit interparticle sliding necessary for particle rearrangement to denser bodies during subsequent compaction. Attempts to produce high density green body compacts of nanosize particles, therefore, generally have been focused on overcoming these surface forces of attraction by using either dispersive fluids or high pressures with or without lubricating liquids. In the present work, the use of high pressure has been employed as a means of compacting nanosize powders to relatively high green densities.

  19. Fe-based nanocrystalline powder cores with ultra-low core loss

    NASA Astrophysics Data System (ADS)

    Wang, Xiangyue; Lu, Zhichao; Lu, Caowei; Li, Deren

    2013-12-01

    Melt-spun amorphous Fe73.5Cu1Nb3Si15.5B7 alloy strip was crushed to make flake-shaped fine powders. The passivated powders by phosphoric acid were mixed with organic and inorganic binder, followed by cold compaction to form toroid-shaped bonded powder-metallurgical magnets. The powder cores were heat-treated to crystallize the amorphous structure and to control the nano-grain structure. Well-coated phosphate-oxide insulation layer on the powder surface decreased the the core loss with the insulation of each powder. FeCuNbSiB nanocrystalline alloy powder core prepared from the powder having phosphate-oxide layer exhibits a stable permeability up to high frequency range over 2 MHz. Especially, the core loss could be reduced remarkably. At the other hand, the softened inorganic binder in the annealing process could effectively improve the intensity of powder cores.

  20. Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders

    SciTech Connect

    Asit Biswas Andrew J. Sherman

    2006-09-25

    This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

  1. Grain growth behavior of extrusion consolidated centrifugally atomized Type 304 stainless steel powder

    SciTech Connect

    Flinn, J.E.; Wright, R.N.; Korth, G.E.

    1987-11-01

    A study was performed to assess the role of entrapped helium in stabilizing the microstructure. Type 304 stainless steel powders produced by centrifugal atomization (CA) were consolidated by hot extrusion. The powders contain approx.7 appM He which was retained during extrusion. Isothermal heat treatments were performed on the CA 304 SS extruded powder as well as on the attached wrought ingot metallurgy (I/M) can and a filler plug of Type 304 SS for comparisons. Compared with the wrought I/M Type 304 SS, the CA Type 304 SS extruded powder exhibited considerable grain growth retardation. Grain growth was shown to be independent of the means used for powder consolidation, including hot isostatic pressing and dynamic consolidation. Also, other CA consolidated alloy powders exhibited grain growth resistance equal to the CA Type 304 SS extruded powder. Results indicate that the entrapped helium in the CA consolidated powder materials plays a significant role in retarding grain growth. 23 figs., 5 tabs.

  2. Wrought processing of ingot-metallurgy gamma titanium aluminide alloys

    SciTech Connect

    Semiatin, S.L.

    1995-12-31

    The wrought processing of ingot-metallurgy, gamma titanium aluminide alloys is reviewed. Attention is focused on five major areas in the development of thermomechanical processes for these materials: (1) ingot structure and homogenization, (2) ingot breakdown via existing techniques, (3) novel processes for ingot breakdown, (4) secondary processing, and (5) process scaleup considerations. The nature of the cast microstructure and the influence of composition and ingot size on grain size and segregation are described. The design of existing processes for ingot breakdown deals with the selection of process variables and the design of cans for nonisothermal metalworking techniques. Novel breakdown processes, including smart forging, alpha forging, controlled dwell extrusion, and equal channel angular extrusion, are reviewed. In the area of secondary processing, developments related to pack rolling of sheet, superplastic sheet forming, and isothermal, closed-die forging are summarized. Lastly, scaleup considerations such as thermal cracking during ingot production are addressed.

  3. The welding metallurgy of Custom Age 625 PLUS alloy

    SciTech Connect

    Cieslak, M.J.; Headley, T.J. ); Frank, R.B. )

    1989-12-01

    The authors discuss the welding metallurgy (solidification behavior, mechanical properties of weld metal, and susceptibility to fusion zone hot cracking) of Carpenter Custom Age 625 PLUS alloy. This alloy solidifies to a nickel austenitic matrix with the formation of a Nb-rich {gamma}/Laves terminal solidification constituent. The low Si and C concentrations in combination with a lower Nb content (3.4wt-%) in this alloy result in a relatively small volume fraction of eutectic constituent relative to that previously observed in Alloy 718. Because of the low volume fraction of eutectic constituent, this alloy has better weldability than Alloy 718. In addition to Laves phase, {gamma} was observed adjacent to Laves phase {gamma} was observed adjacent to Laves in the fusion zone microstructure of the new alloy. Weld metal strengths approximately equal to aged wrought product can be achieved by direct aging of welds.

  4. Physical and mechanical metallurgy of high purity Nb accelerator cavities.

    SciTech Connect

    Wright, N. T.; Bieler, T. R.; Pourgoghart , F.; Compton, C.; Hartwig, K. T.; Baars, D.; Zamiri, A.; Chandrasekaran, S.; Darbandi, P.; Jiang, H.; Skoug, E.; Balachandran, S.; Ice, G. E.; Liu, W.; Michigan State Univ.; Texas A & M Univ.; ORNL

    2010-01-01

    In the past decade, high Q values have been achieved in high purity Nb superconducting radio frequency (SRF) cavities. Fundamental understanding of the physical metallurgy of Nb that enables these achievements is beginning to reveal what challenges remain to establish reproducible and cost-effective production of high performance SRF cavities. Recent studies of dislocation substructure development and effects of recrystallization arising from welding and heat treatments and their correlations with cavity performance are considered. With better fundamental understanding of the effects of dislocation substructure evolution and recrystallization on electron and phonon conduction, as well as the interior and surface states, it will be possible to design optimal processing paths for cost-effective performance using approaches such as hydroforming, which minimizes or eliminates welds in a cavity.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1997-06-01

    Zircon, ZrSiO4, 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 reactionsintering. Reinforcing the hypereutectic Al-Si alloy with 15 vol% zircon particles (size < 200 µm) 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.

  7. Implications of elastic wave velocities for Apollo 17 rock powders

    NASA Technical Reports Server (NTRS)

    Talwani, P.; Nur, A.; Kovach, R. L.

    1974-01-01

    Ultrasonic P- and S-wave velocities of lunar rock powders 172701, 172161, 170051, and 175081 were measured at room temperature and to 2.5 kb confining pressure. The results compare well with those of terrestrial volcanic ash and powdered basalt. P-wave velocity values up to pressures corresponding to a lunar depth of 1.4 km preclude cold compaction alone as an explanation for the observed seismic velocity structure at the Apollo 17 site. Application of small amounts of heat with simultaneous application of pressure causes rock powders to achieve equivalence of seismic velocities for competent rocks.

  8. Cow dung powder poisoning.

    PubMed

    Sherfudeen, Khaja Mohideen; Kaliannan, Senthil Kumar; Dammalapati, Pavan Kumar

    2015-11-01

    Cow dung, which has germicidal property, was used in ancient days to clean living premises in South India. Nowadays, people are using commercially available synthetic cow dung powder. It is locally known as "saani powder" in Tamil Nadu. It is freely available in homes and is sometimes accidentally consumed by children. It is available in two colors - yellow and green. Cow dung powder poisoning is common in districts of Tamil Nadu such as Coimbatore, Tirupur, and Erode. We report two cases of yellow cow dung powder poisoning from our hospital. PMID:26730123

  9. Powder Crystallography on Macromolecules

    SciTech Connect

    Margiolaki,I.; Wright, J.

    2008-01-01

    Following the seminal work of Von Dreele, powder X-ray diffraction studies on proteins are being established as a valuable complementary technique to single-crystal measurements. A wide range of small proteins have been found to give synchrotron powder diffraction profiles where the peak widths are essentially limited only by the instrumental resolution. The rich information contained in these profiles, combined with developments in data analysis, has stimulated research and development to apply the powder technique to microcrystalline protein samples. In the present work, progress in using powder diffraction for macromolecular crystallography is reported.

  10. Sol-spray preparation, particulate characteristics, and sintering of alumina powders

    SciTech Connect

    Varma, H.K.; Mani, T.V.; Damodaran, A.D.; Warrier, K.G.K.; Balachandran, U.

    1993-07-01

    Fine alumina powders of spherical morphology and narrow particle-size distribution have been synthesized by a technique that uses precipitation/peptization/spray drying of boehmite sol prepared from aluminum nitrate. The spray-dried powder was further washed with solvents of varying polarities, such as acetone, isopropanol, and tert-butanol. This post-spray-drying treatment changed the powder`s particle-size distribution, morphology, density, and compaction characteristics. Microstructure, dielectric properties, and effect of post-treatment on the boehmite-sol-derived alumina powders in reducing agglomeration are discussed.

  11. Chem-Prep PZT 95/5 for Neutron Generator Applications: Powder Fractionation Study of Production-Scale Powders

    SciTech Connect

    MOORE, DIANA L.; VOIGT, JAMES A.; WATSON, CHAD S.; MCKENZIE, BONNIE B.; MOORE, ROGER H.; HUTCHINSON, MICHAEL A.; LOCKWOOD, STEVEN J.; RODMAN-GONZALES, EMILY D.

    2003-06-01

    The Materials Chemistry Department 1846 has developed a lab-scale chem-prep process for the synthesis of PNZT 95/5, referred to as the ''SP'' process (Sandia Process). This process (TSP) has been successfully transferred to and scaled-up by Department 14192 (Ceramics and Glass Department), producing the larger quantities of PZT powder required to meet the future supply needs of Sandia for neutron generator production. The particle size distributions of TSP powders routinely have been found to contain a large particle size fraction that was absent in development (SP) powders. This SAND report documents experimental studies focused on characterizing these particles and assessing their potential impact on material performance. To characterize these larger particles, fractionation of several TSP powders was performed. The ''large particle size fractions'' obtained were characterized by particle size analysis, SEM, and ICP analysis and incorporated into compacts and sintered. Large particles were found to be very similar in structure and composition as the bulk of the powder. Studies showed that the large-size fractions of the powders behave similarly to the non-fractionated powder with respect to the types of microstructural features once sintered. Powders were also compared that were prepared using different post-synthesis processing (i.e. differences in precipitate drying). Results showed that these powders contained different amounts and sizes of porous inclusions when sintered. How this affects the functional performance of the PZT 95/5 material is the subject of future investigations.

  12. Near Net Shape Manufacturing of New Titanium Powders for Industry

    SciTech Connect

    2009-05-01

    This factsheet describes a research project whose goal is to develop a manufacturing technology to process new titanium powders into fully consolidated near net shape components for industrial applications. This will be achieved using various technologies, including press and sinter, pneumatic isostatic forging (PIF), hot isostatic pressing (HIP), and adiabatic compaction.

  13. Method of preparing a powdered, electrically insulative separator for use in an electrochemical cell

    DOEpatents

    Cooper, Tom O.; Miller, William E.

    1978-01-01

    A secondary electrochemical cell includes electrodes separated by a layer of electrically insulative powder. The powder includes refractory materials selected from the oxides and nitrides of metals and metaloids. The powdered refractory material, blended with electrolyte particles, is compacted as layers onto an electrode to form an integral electrode structure and assembled into the cell. The assembled cell is heated to its operating temperature leaving porous layers of electrically insulative, refractory particles, containing molten electrolyte between the electrodes.

  14. Iron-carbon compacts and process for making them

    DOEpatents

    Sheinberg, Haskell

    2000-01-01

    The present invention includes iron-carbon compacts and a process for making them. The process includes preparing a slurry comprising iron powder, furfuryl alcohol, and a polymerization catalyst for initiating the polymerization of the furfuryl alcohol into a resin, and heating the slurry to convert the alcohol into the resin. The resulting mixture is pressed into a green body and heated to form the iron-carbon compact. The compact can be used as, or machined into, a magnetic flux concentrator for an induction heating apparatus.

  15. Iron-carbon compacts and process for making them

    SciTech Connect

    Sheinberg, H.

    2000-07-25

    The present invention includes iron-carbon compacts and a process for making them. The process includes preparing a slurry comprising iron powder, furfuryl alcohol, and a polymerization catalyst for initiating the polymerization of the furfuryl alcohol into a resin, and heating the slurry to convert the alcohol into the resin. The resulting mixture is pressed into a green body and heated to form the iron-carbon compact. The compact can be used as, or machined into, a magnetic flux concentrator for an induction heating apparatus.

  16. Counterintuitive compaction behavior of clopidogrel bisulfate polymorphs.

    PubMed

    Khomane, Kailas S; More, Parth K; Bansal, Arvind K

    2012-07-01

    Being a density violator, clopidogrel bisulfate (CLP) polymorphic system (forms I and II) allows us to study individually the impact of molecular packing (true density) and thermodynamic properties such as heat of fusion on the compaction behavior. These two polymorphs of CLP were investigated for in-die and out-of-die compaction behavior using CTC profile, Heckel, and Walker equations. Compaction studies were performed on a fully instrumented rotary tabletting machine. Detailed examinations of the molecular packing of each form revealed that arrangement of the sulfate anion differs significantly in both crystal forms, thus conferring different compaction behavior to two forms. Close cluster packing of molecules in form I offers a rigid structure, which has poor compressibility and hence resists deformation under compaction pressure. This results into lower densification, higher yield strength, and mean yield pressure, as compared with form II at a given pressure. However, by virtue of higher bonding strength, form I showed superior tabletability, despite its poor compressibility and deformation behavior. Form I, having higher true density and lower heat of fusion showed higher bonding strength. Hence, true density and not heat of fusion can be considered predictor of bonding strength of the pharmaceutical powders. PMID:22488254

  17. Determination of cerium in materials of ferrous metallurgy

    SciTech Connect

    Popkova, G.N.; Fedorova, N.D.; Zubritskaya, L.D.

    1994-06-01

    The determination of low contents of cerium in highly alloyed steels and alloys involves a long and laborious separation from accompanying components. A method of separation by adsorption of cerium fluoride in silicon dioxide, previously used in analytical laboratories of the rare-metal industry in the analysis of mineral raw materials and technological solution, has been used to increase the selectivity and rapidity of the separation of cerium. The purpose of this work was to study the possibility of using this method of separation of cerium in the analysis of highly alloyed steels and alloys. The degree of precipitation of cerium fluoride in the presence of iron (the basis of materials of ferrous metallurgy), which has virtually no effect on the adsorption process, was studied. The degree of adsorption is also 95-100% in the presence of 1 g of iron. After cerium was separated from accompanying components, it was determined by amperometric and photometric methods (the latter with arsenazo III) and by inversion voltammetry. Thus, the proposed method of separation from accompanying elements in alloyed steels is selective and rapid and permits the determination of microgram quantities of cerium with the requisite accuracy.

  18. [Possible health effects associated with Pre-Columbian metallurgy].

    PubMed

    Idrovo, Alvaro Javier

    2005-09-01

    In the Old World, several researchers have indicated that adverse health effects were associated with exposure to arsenic, and that this influenced a change in the use of copper-arsenic alloys to others less toxic. This hypothesis was evaluated for three Pre-Columbian metallurgy traditions: Central Andes, Intermediate Area, and West Mexico. The metal artifacts from the Central Andes showed arsenic concentrations similar to those in the Old World (0.5%-1.0%). In the Intermediate Area the values were smallest; however, in West Mexico the arsenic content was very high (7%-25%). In Central Andes arsenical bronze was used initially, but copper-tin alloys when introduced were preferred and distributed throughout the Inca Empire. Osteological and artistic evidences of foot amputations among Moche individuals from Central Andes support the presence of "black foot disease" (a condition associated with arsenic poisoning) among Pre-Columbian populations. In conclusion, the adverse effects of arsenic have been observed in the New World, and that these effects promoted a change toward the use of less toxic alloys. PMID:16276677

  19. Macromolecular metallurgy of binary mesocrystals via designed multiblock terpolymers.

    PubMed

    Xie, Nan; Liu, Meijiao; Deng, Hanlin; Li, Weihua; Qiu, Feng; Shi, An-Chang

    2014-02-26

    Self-assembling block copolymers provide access to the fabrication of various ordered phases. In particular, the ordered spherical phases can be used to engineer soft mesocrystals with domain size at the 5-100 nm scales. Simple block copolymers, such as diblock copolymers, form a limited number of mesocrystals. However multiblock copolymers are capable to form more complex mesocrystals. We demonstrate that designed B1AB2CB3 multiblock terpolymers, in which the A- and C-blocks form spherical domains and the packing of these spheres can be controlled by changing the lengths of the middle and terminal B-blocks, self-assemble into various binary mesocrystals with space group symmetries of a large number of binary ionic crystals, including NaCl, CsCl, ZnS, α-BN, AlB2, CaF2, TiO2, ReO3, Li3Bi, Nb3Sn(A15), and α-Al2O3. This approach can be generalized to other terpolymers as well as to tetrapolymers to obtain ternary mesocrystals. Our study provides a new concept of macromolecular metallurgy for producing crystal phases in a mesoscale and thus makes multiblock copolymers a robust platform for the engineering of functional materials. PMID:24528160

  20. Welding metallurgy of nickel alloys in gas turbine components

    SciTech Connect

    Lingenfelter, A. C., LLNL

    1997-05-21

    Materials for gas turbine engines are required to meet a wide range of temperature and stress application requirements. These alloys exhibit a combination of creep resistance, creep rupture strength, yield and tensile strength over a wide temperature range, resistance to environmental attack (including oxidation, nitridation, sulphidation and carburization), fatigue and thermal fatigue resistance, metallurgical stability and useful thermal expansion characteristics. These properties are exhibited by a series of solid-solution-strengthened and precipitation-hardened nickel, iron and cobalt alloys. The properties needed to meet the turbine engine requirements have been achieved by specific alloy additions, by heat treatment and by thermal mechanical processing. A thorough understanding of the metallurgy and metallurgical processing of these materials is imperative in order to successfully fusion weld them. This same basic understanding is required for repair of a component with the added dimension of the potential effects of thermal cycling and environmental exposure the component will have endured in service. This article will explore the potential problems in joining and repair welding these materials.