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Hardness distribution in pack carburised molybdenum alloys
The properties of Cu powder used to make termination terminals for ceramic chip capicitors were evaluated. Particle sizes 0.5mm, 1.0mm and 5.0mm were studied. The Cu powders were incorporated in a paste in which the Cu powder was homogeneously distributed. Shrinkage during processing at 650°C to 850°C was investigated and the smallest powders had the largest shrinkage.
Magnesium Hydriding combustion synthesis of magnesium-nickel-copper hydrogen storage alloys T.Akiyama et al. (Osaka Prefecture University, Sakai, Japan .) Intermetallics, Vo[ lO, 20o2, 927-932. Hydriding combustion synthesis of MgNi-Cu alloys, for H storage applications, was investigated. Mg2Cu was synthesised at 480°C and 525°C in H-Ar without unreacted Mg. The catalytic effect of Ni in promoting hydriding was found in ternary alloys in which there were no binary compounds. The products were examined by scanning electron microscopy which revealed evidence of a eutectic reaction.
Molybdenum Hardness and structure of molybdenum consolidated from nanopowders by plasma pressure compaction T.S.Srivatsan et al. (University of Akron, Ohio, USA.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 3, 2002, 181-186. Consolidation of Mo nanopowders to bulk materials by plasma pressure compaction is reported. Compaction at 1400°C and 48MPa for three min attained 97% density. Agglomerates in the nanopowders affected density and structure. Micron sized powders were also compacted and attained 98.5% at 1650°C. Samples from nanopowders had Vicker's hardness of 2.95GPa and from micron powders 2.16GPa.
Grain growth and annealing textures in dispersion strengthened molybdenum sheets K.Kamihira, T.Fujii. (National Inst. for Materials Sciences, Tsukuba, Japan .) ].Japan Soc. Powder/Powder Metall., Vol 48, No 12, 2ooi, 1132-1138. In Japanese. Grain growth and recrystallisation textures in hot rolled and annealed Mo0.8mol%(TiC or HfC) were investigated. It was found that O was also present in the materials. The dispersed carbides/oxides
metal-powder.net
acted as grain growth inhibitors. The temperature at which recrystallisation started was dependent on the type of dispersed phase present. Textures are described.
Hardness distribution in pack carburised molybdenum aLLoys T.Hoshika et al. (Okayama University of Science, Okayama, Japan.) ].Japan Soc. Powder/Powder Metal[., Vol 49, No 1, 2002, 32-36. In Japanese. Mo and Mo-Ti alloys were pack carburised. Vicker's hardness profiles were measured. The carburised samples were harder than recrystallised samples. The increased hardness in Mo-Ti is attributed to the presence of precipitates. In Mo-Ti these were TiC.
Nickel Effects of process route on structure and properties of nickel base superaUoy W.M.Guo et al. (Central Iron and Steel Research Inst., Beijing, China.) PM Industry, Vo111, No 5, 2001, 7-12. In Chinese. The effects of process route of structure and mechanical properties of a Ni base superalloy, FG H95 were investigated. The preferred process was reported to be hot isostatic pressing.
Tungsten Microstructure and sintering behaviour of tungsten-copper nanocomposite powders J.S.Lee et al. (Hanyang University, Ansan, Korea.) Int. J. Refract. Metals/Hard Mater., Vol 20, No 3, 2002, 201-206.
It is noted that W wire, doped with A1, K and Si also contains small concentrations on impurities. It is usual to determine these by chemical analysis. Excess electrical resistivity can measure concentrations of solute impurities and solution-dissolution processes can be followed. In combination with other electrical properties different solute impurities can be separated. The method allows segregation-desegregation (Fe, Co) and oxidation-reduction, (A1, Si) to be investigated.
Carbide-induced embrittlement in tungsten wires l.Gaal, L.Uray. (Hungarian Academy of Sciences, Budapest, Hungary.) Int. ]. Refract. Metals/Hard Mater., Vol 20, No /4, 2002, 327"333.
It is noted that hard drawn and stress relieved non-sag W wires are brittle at ambient temperature in torsion tests. This is attributed to presence of WC on parts of the surface. This embrittlement can be removed by stress relieving at 1425°C for 15min in an atmosphere with partial pressure of O of 10-4mbar. The material remains brittle after longer times and at O partial pressure of 10-6mbar. This heat treatment reduces the WC on the surface. The WC induced embrittlement is compared with other forma of embrittlement in non-sag W wire.
Ceramic materials Wet batch grinding of alumina hydrate in a stirred bead mill H.B.Fadhe[, C.F rances. ( Laboratory for G~nie Chimique, Toulouse, France.) Powder Technol,, Vo1119, N 0 2-3, 2OOl, 257-268.
Microstructure and sintering of W-20% Cu nanocomposite powder produced by a thermochemical process were investigated. Spray dried powder showed a hollow spherical agglomerate with variation in % Cu. H reduced W-Cu powder was smaller than 200nm and contained a little O which reduced sintered density to 90%. Heat treatment before sintering increased this to 94% which was attributed to reduction of O. Higher annealing temperature reduced sintered density and caused anisotropic shrinkage. It is suggested that this may be due to formation of a strong W skeleton.
Wet batch comminution of alumina hydrate in a stirred bead mill was investigated with reference to material and process parameters, energy and particle size of product. It is shown that there was a limit to the fineness of the product. Morphology of the product particles was characterised and a fragmentation path is identified. The analysis allowed interpretation of the evolution of particle size with time.
Effects of impurities on doped tungsten wires L.Uray. (Hungarian Academy of Sciences, Budapest, Hungary.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 4, 2002, 319-326.
A low-temperature process route for lithium-manganese spinel M.Arakawa et at. (Kyoto University, Kyoto, Japan.) ].Japan Soc. Powder/Powder Metal[., Vo[ 48, No 12, 2ooi, 1139-1144,. In Japanese.
May ao03
33
Magnesium Hydriding combustion synthesis of magnesium-nickel-copper hydrogen storage alloys T.Akiyama et al. (Osaka Prefecture University, Sakai, Japan .) Intermetallics, Vo[ lO, 20o2, 927-932. Hydriding combustion synthesis of MgNi-Cu alloys, for H storage applications, was investigated. Mg2Cu was synthesised at 480°C and 525°C in H-Ar without unreacted Mg. The catalytic effect of Ni in promoting hydriding was found in ternary alloys in which there were no binary compounds. The products were examined by scanning electron microscopy which revealed evidence of a eutectic reaction.
Molybdenum Hardness and structure of molybdenum consolidated from nanopowders by plasma pressure compaction T.S.Srivatsan et al. (University of Akron, Ohio, USA.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 3, 2002, 181-186. Consolidation of Mo nanopowders to bulk materials by plasma pressure compaction is reported. Compaction at 1400°C and 48MPa for three min attained 97% density. Agglomerates in the nanopowders affected density and structure. Micron sized powders were also compacted and attained 98.5% at 1650°C. Samples from nanopowders had Vicker's hardness of 2.95GPa and from micron powders 2.16GPa.
Grain growth and annealing textures in dispersion strengthened molybdenum sheets K.Kamihira, T.Fujii. (National Inst. for Materials Sciences, Tsukuba, Japan .) ].Japan Soc. Powder/Powder Metall., Vol 48, No 12, 2ooi, 1132-1138. In Japanese. Grain growth and recrystallisation textures in hot rolled and annealed Mo0.8mol%(TiC or HfC) were investigated. It was found that O was also present in the materials. The dispersed carbides/oxides
metal-powder.net
acted as grain growth inhibitors. The temperature at which recrystallisation started was dependent on the type of dispersed phase present. Textures are described.
Hardness distribution in pack carburised molybdenum aLLoys T.Hoshika et al. (Okayama University of Science, Okayama, Japan.) ].Japan Soc. Powder/Powder Metal[., Vol 49, No 1, 2002, 32-36. In Japanese. Mo and Mo-Ti alloys were pack carburised. Vicker's hardness profiles were measured. The carburised samples were harder than recrystallised samples. The increased hardness in Mo-Ti is attributed to the presence of precipitates. In Mo-Ti these were TiC.
Nickel Effects of process route on structure and properties of nickel base superaUoy W.M.Guo et al. (Central Iron and Steel Research Inst., Beijing, China.) PM Industry, Vo111, No 5, 2001, 7-12. In Chinese. The effects of process route of structure and mechanical properties of a Ni base superalloy, FG H95 were investigated. The preferred process was reported to be hot isostatic pressing.
Tungsten Microstructure and sintering behaviour of tungsten-copper nanocomposite powders J.S.Lee et al. (Hanyang University, Ansan, Korea.) Int. J. Refract. Metals/Hard Mater., Vol 20, No 3, 2002, 201-206.
It is noted that W wire, doped with A1, K and Si also contains small concentrations on impurities. It is usual to determine these by chemical analysis. Excess electrical resistivity can measure concentrations of solute impurities and solution-dissolution processes can be followed. In combination with other electrical properties different solute impurities can be separated. The method allows segregation-desegregation (Fe, Co) and oxidation-reduction, (A1, Si) to be investigated.
Carbide-induced embrittlement in tungsten wires l.Gaal, L.Uray. (Hungarian Academy of Sciences, Budapest, Hungary.) Int. ]. Refract. Metals/Hard Mater., Vol 20, No /4, 2002, 327"333.
It is noted that hard drawn and stress relieved non-sag W wires are brittle at ambient temperature in torsion tests. This is attributed to presence of WC on parts of the surface. This embrittlement can be removed by stress relieving at 1425°C for 15min in an atmosphere with partial pressure of O of 10-4mbar. The material remains brittle after longer times and at O partial pressure of 10-6mbar. This heat treatment reduces the WC on the surface. The WC induced embrittlement is compared with other forma of embrittlement in non-sag W wire.
Ceramic materials Wet batch grinding of alumina hydrate in a stirred bead mill H.B.Fadhe[, C.F rances. ( Laboratory for G~nie Chimique, Toulouse, France.) Powder Technol,, Vo1119, N 0 2-3, 2OOl, 257-268.
Microstructure and sintering of W-20% Cu nanocomposite powder produced by a thermochemical process were investigated. Spray dried powder showed a hollow spherical agglomerate with variation in % Cu. H reduced W-Cu powder was smaller than 200nm and contained a little O which reduced sintered density to 90%. Heat treatment before sintering increased this to 94% which was attributed to reduction of O. Higher annealing temperature reduced sintered density and caused anisotropic shrinkage. It is suggested that this may be due to formation of a strong W skeleton.
Wet batch comminution of alumina hydrate in a stirred bead mill was investigated with reference to material and process parameters, energy and particle size of product. It is shown that there was a limit to the fineness of the product. Morphology of the product particles was characterised and a fragmentation path is identified. The analysis allowed interpretation of the evolution of particle size with time.
Effects of impurities on doped tungsten wires L.Uray. (Hungarian Academy of Sciences, Budapest, Hungary.) Int. J. Refract. Metals/Hard Mater., Vol 2o, No 4, 2002, 319-326.
A low-temperature process route for lithium-manganese spinel M.Arakawa et at. (Kyoto University, Kyoto, Japan.) ].Japan Soc. Powder/Powder Metal[., Vo[ 48, No 12, 2ooi, 1139-1144,. In Japanese.
May ao03
33