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Bismuth-ceramic composites with positive temperature coefficient of electrical resistance
Pokroky Praskove Metal., Vol 37, No 3, 1999,556. (In Czech). Cu-Al,O, composites are reviewed with reference to characteristics of the system and process methods. Structure is considered in terms of spatial distribution of phases and some real materials are taken into account. Mechanical properties at ambient and elevated temperatures are evaluated and a fracture model is proposed. Effects of Also, particles on recrystallization of Cu are discussed.
Electrical
and magnetic
materials BISMUTH-CERAMIC COMPOSITES WITH POSITIVE TEMPERATURE COEFFICIENT OF ELECTRICAL RESISTANCE T.Kanou et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7, 1999,752-756. (In Japanese.) It is reported that Bi-ceramic composite materials, with a positive temperature coefficient of resistance at around the melting point of Bi, 270 “C, were fabricated by hot pressing. An investigation, to determine optimum process conditions and to study electrical property/microstructure relationships, is described. A density of Bi99% was attained in 45mol%SrB,(Ti,,s,, NbO,ss)O,, after hot pressing. MICROSTRUCTURAL CHANGE DURING SYNTHESIS OF BORON SILICIDE AND CHANGES DUE TO PALLADIUM M.Tajima, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7, 1999,757-766. (In English.) Studies of the kinetics of phase formation and microstructures in Mn doped Fe-Si materials, with additions of Pd, are described. Samples were prepared by sintering of powders or by melting/casting. Phases detected were PFeSi,, EFeSi and aFe,Si,. The materials have semi-conducting properties and have thermo-electric applications. SUPERCONDUCTING PROPERTIES OF BISMUTH MATERIALS MADE BY COMPRESSION MOULDING H.Terada et al. (Chubu University, Kasugai, Japan.) J. Jpn sot. PowderlPowder Metall., Vol 46, No 7, 1999,767-771. (In Japanese.) It is reported that an Ag sheathed superconducting Bi2223 tape had been
produced from powder packed into a Ag tube which was cold rolled to consolidate the superconducting oxide powder. Superconducting properties, as a function of tape thickness, are described. INJECTION MOULDING ALLOY MATERIALS
OF SENDUST
H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 8, 1999,858864. (In English.) The effects of powder and process parameters on MIM processing and magnetic properties of Sendust, Fe9.5%Si-5.5%Al, were investigated to determine the potential of this process for this material. Properties depended on the type of powder used and on process conditions and were comparable with those of wrought alloys.
liard materials steels
and tool
MATERIAL DESIGN FOR CEMENTED CARBIDE TOOL WITH FUNCTIONALLY GRADED COATING T.Nomura et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) Int. J. Refract. Metals IHard Mater., Vol 17, No 6,1999,397-404. Studies of cemented carbide cutting tools with functionally graded coatings are described, with the intention of making high performance tools. The coating is required to be a hard, wear resistant cermet containing residual compressive stress. A new method of estimating temperature distribution was used and thermal stresses calculated, the object being to balance thermal and residual stresses. A new material based on a cemented carbide substrate with a graded Ti(C,N) coating is shown to perform well. EFFECT OF NITROGEN ON SUPERSOLIDUS SINTERING SPEED STEEL
OF HIGH
I.Aguirre et al. (University of Navarra, San Sebastian, Spain.) Powder Metall., Vol42, No 4, 1999,353-357. Water atomized M35M high speed steel powders, with (1.8 to 2.5)wt%C, were cold compacted at 700 MPa. Full density was attained on sintering in a N rich gas at 1105 to 1140 “C!. Sintering was correlated with dilatometer experiments and calculated phase diagram data. It is shown that sintering takes place above the solidus temperature in the austenitelcarbidelliquid phase field. N is shown to widen this phase field and to promote sinterability in comparison with vacuum sintered alloys.
ISOTROPIC CARBIDE
GROWTH
IN TUNGSTEN
H.S.Ryoo et al. (Inha University, Incheon, Korea.) J. Korean Inst. MetalslMater., Vol 36, No 11, 1998, 19151921. (In Korean.) Development of triangular prisms and abnormal grain growth in WC were modelled by a modified Monte-Carlo simulation incorporating atomic absorption and coalescence. Grain shape developed by preferential fast growth on certain crystal planes. The model was evaluated against experiments on 0.8 ym or 325mesh WC-25wt%Co, solid state sintered at 1250 “C for 12 hours and liquid phase sintered at 1370 “C! for 72 hours. The alloy made from the finer powder developed prismatic crystals during solid state sintering. FABRICATION OF TOOL INJECTION MOULDING
STEELS
BY
H.Kyogoku et al. (Kinki University, Higashihiroshima, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 8, 1999,853-857. (In English.) Effects of sintering temperature, 1100 to 1210 “C, and tempering temperature, 180 to 530 “C, on mechanical properties of an injection moulded 12%Cr-l%Mo tool steel were investigated. Debinding was at 320 “C!, samples were annealed at 900 “C and quenched from 1020 “C. Density increased with sintering temperature up to 99%. Rockwell hardness declined with increase in tempering temperature, for example 58C at 270 “C. Transverse rupture stress of 3000 MPa was attained irrespective of tempering temperature.
lntermetallic
materials
MICROSTRUCTURE AND HIGH TEMPERATURE BEHAVIOUR OF NICKEL ALUMINIDE-CHROMIUM COMPOSITE J.A.Jimenez et al. (National Centre for Metallurgical Investigations, Madrid, Spain.) Acta Mater., Vol47, No 13,1999, 3655-3662. It is reported that a NiAl-27at%Cr alloy had been made from Ar atomized powders by HIP at 1350 “C and 400 MPa for 4 hours. The structure was a fine grained NiAl with 1.7 pm dispersoids of Cr. Mechanical characteristics were determined at 650 to 1100 “C by tensile strain rate change tests. Analysis of the results showed a transition to a low stress exponent creep regime with decreasing stress and/or increasing temperatures. It is suggested that deformation is associated with dislocation movement.
MPR December
2000 39
Electrical
and magnetic
materials BISMUTH-CERAMIC COMPOSITES WITH POSITIVE TEMPERATURE COEFFICIENT OF ELECTRICAL RESISTANCE T.Kanou et al. (Tohoku University, Sendai, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7, 1999,752-756. (In Japanese.) It is reported that Bi-ceramic composite materials, with a positive temperature coefficient of resistance at around the melting point of Bi, 270 “C, were fabricated by hot pressing. An investigation, to determine optimum process conditions and to study electrical property/microstructure relationships, is described. A density of Bi99% was attained in 45mol%SrB,(Ti,,s,, NbO,ss)O,, after hot pressing. MICROSTRUCTURAL CHANGE DURING SYNTHESIS OF BORON SILICIDE AND CHANGES DUE TO PALLADIUM M.Tajima, K.Hayashi. (University of Tokyo, Tokyo, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7, 1999,757-766. (In English.) Studies of the kinetics of phase formation and microstructures in Mn doped Fe-Si materials, with additions of Pd, are described. Samples were prepared by sintering of powders or by melting/casting. Phases detected were PFeSi,, EFeSi and aFe,Si,. The materials have semi-conducting properties and have thermo-electric applications. SUPERCONDUCTING PROPERTIES OF BISMUTH MATERIALS MADE BY COMPRESSION MOULDING H.Terada et al. (Chubu University, Kasugai, Japan.) J. Jpn sot. PowderlPowder Metall., Vol 46, No 7, 1999,767-771. (In Japanese.) It is reported that an Ag sheathed superconducting Bi2223 tape had been
produced from powder packed into a Ag tube which was cold rolled to consolidate the superconducting oxide powder. Superconducting properties, as a function of tape thickness, are described. INJECTION MOULDING ALLOY MATERIALS
OF SENDUST
H.Miura et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 8, 1999,858864. (In English.) The effects of powder and process parameters on MIM processing and magnetic properties of Sendust, Fe9.5%Si-5.5%Al, were investigated to determine the potential of this process for this material. Properties depended on the type of powder used and on process conditions and were comparable with those of wrought alloys.
liard materials steels
and tool
MATERIAL DESIGN FOR CEMENTED CARBIDE TOOL WITH FUNCTIONALLY GRADED COATING T.Nomura et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) Int. J. Refract. Metals IHard Mater., Vol 17, No 6,1999,397-404. Studies of cemented carbide cutting tools with functionally graded coatings are described, with the intention of making high performance tools. The coating is required to be a hard, wear resistant cermet containing residual compressive stress. A new method of estimating temperature distribution was used and thermal stresses calculated, the object being to balance thermal and residual stresses. A new material based on a cemented carbide substrate with a graded Ti(C,N) coating is shown to perform well. EFFECT OF NITROGEN ON SUPERSOLIDUS SINTERING SPEED STEEL
OF HIGH
I.Aguirre et al. (University of Navarra, San Sebastian, Spain.) Powder Metall., Vol42, No 4, 1999,353-357. Water atomized M35M high speed steel powders, with (1.8 to 2.5)wt%C, were cold compacted at 700 MPa. Full density was attained on sintering in a N rich gas at 1105 to 1140 “C!. Sintering was correlated with dilatometer experiments and calculated phase diagram data. It is shown that sintering takes place above the solidus temperature in the austenitelcarbidelliquid phase field. N is shown to widen this phase field and to promote sinterability in comparison with vacuum sintered alloys.
ISOTROPIC CARBIDE
GROWTH
IN TUNGSTEN
H.S.Ryoo et al. (Inha University, Incheon, Korea.) J. Korean Inst. MetalslMater., Vol 36, No 11, 1998, 19151921. (In Korean.) Development of triangular prisms and abnormal grain growth in WC were modelled by a modified Monte-Carlo simulation incorporating atomic absorption and coalescence. Grain shape developed by preferential fast growth on certain crystal planes. The model was evaluated against experiments on 0.8 ym or 325mesh WC-25wt%Co, solid state sintered at 1250 “C for 12 hours and liquid phase sintered at 1370 “C! for 72 hours. The alloy made from the finer powder developed prismatic crystals during solid state sintering. FABRICATION OF TOOL INJECTION MOULDING
STEELS
BY
H.Kyogoku et al. (Kinki University, Higashihiroshima, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 8, 1999,853-857. (In English.) Effects of sintering temperature, 1100 to 1210 “C, and tempering temperature, 180 to 530 “C, on mechanical properties of an injection moulded 12%Cr-l%Mo tool steel were investigated. Debinding was at 320 “C!, samples were annealed at 900 “C and quenched from 1020 “C. Density increased with sintering temperature up to 99%. Rockwell hardness declined with increase in tempering temperature, for example 58C at 270 “C. Transverse rupture stress of 3000 MPa was attained irrespective of tempering temperature.
lntermetallic
materials
MICROSTRUCTURE AND HIGH TEMPERATURE BEHAVIOUR OF NICKEL ALUMINIDE-CHROMIUM COMPOSITE J.A.Jimenez et al. (National Centre for Metallurgical Investigations, Madrid, Spain.) Acta Mater., Vol47, No 13,1999, 3655-3662. It is reported that a NiAl-27at%Cr alloy had been made from Ar atomized powders by HIP at 1350 “C and 400 MPa for 4 hours. The structure was a fine grained NiAl with 1.7 pm dispersoids of Cr. Mechanical characteristics were determined at 650 to 1100 “C by tensile strain rate change tests. Analysis of the results showed a transition to a low stress exponent creep regime with decreasing stress and/or increasing temperatures. It is suggested that deformation is associated with dislocation movement.
MPR December
2000 39