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High strain rate compression of metal foams produced by PM
Cemented
carbides
EFFECTS OF COBALT PARTICLE SIZE ON PROCESSING AND PROPERTIES OF TUNGSTEN CARBIDE-COBALT J.Harvi, D.F.Carroll. (OMG Americas, USA.) WC-Co alloys were discussed with reference to the use of fine WC powders, down to 0.2 pm. It was noted that processing and properties are influenced by the crystallite size of the Co binder. A summary of the effects of Co particle size on WC-Co made from superfine WC was presented for Co crystallite sizes of 0.4 to 1.5 pm. Suggestions were made for selection of Co particle size. SINTERING AIDS FOR LIQUID PHASE SINTERING OF FINE GRAIN TUNGSTEN CARBIDE-COBALT B.H.Kear et al. (Rutgers University, USA.) A study of sintering aids for WC-Co was described. VC and Cr,C, growth inhibitors were said to be solid solution forming in the Co binder phase. Above 1200°C the liquid phase formed was shown to contain more than one liquid phase and the inhibitor carbides could be uniformly distributed in the liquid at lower temperatures. The phenomenon was exploited in low temperature sintering of WC-Co. ASPECTS OF ULTRAFINE HARDMETAL SINTERING B.Lux et al. (Technical University of Vienna, Vienna, Austria.) The trend to use finer powders in making WC-Co was discussed with reference to rapid growth of WC grains which may occur during liquid phase sintering and the need to use growth inhibitors. Aspects of sintering, outgassing, spread of the binder phase, formation of liquid and liquid phase sintering were reviewed. Limits to WC grain size were assessed and alternative consolidation techniques were discussed. THFRMlT PROCESS FOR PRODUCTION OF TUNGSTEN CARBIDE J.D.Morris, C.J.Terry. (Kennametal Inc, USA.) It was reported that a thermit type process had been used to make WC directly from ore concentrates. The WC was shown to have properties suitable for application in hardfacing, hardmetals and PDC matrix composite powders. INFLUENCE OF BINDER CONSTITUTION ON SHAPE OF TUNGSTEN CARBIDE GRAINS
J.J.Oakes et al. (Teledyne Metalworking Products Inc, USA.) The morphology of WC grains in coarse grained WC-Co, prismatic with sharp edges, was discussed and shown to be dis-advantageous where there is crack initiation and propagation caused by thermal shock. It was reported that the addition of Ni or Cr to the Co binder resulted in more rounded WC grains giving a tougher material more resistant to cracks. Effects of process parameters on WC grain shape were investigated and the results were described. CEMENTED CARBIDES DOPED WITH RARE EARTHS C.Lin et al. (General Research Inst. for Non-Ferrous Metals, Beijing, China.) The addition of rare earths, to improve the performance of cemented carbides in cutting applications, was discussed. The additions were shown to increase tool life due to enhanced mechanical properties. The additions were reported to influence both hard phase and binder and to improve grain boundary structure. The rare earth additions were also shown to avoid the need for grain growth inhibitors even in ultrafine grained materials. A range of properties was described.
Powder production characterization
and
FLUORINATION OF LANTHANUMNICKEL-TIN POWDERS FOR BATTERY ELECTRODES M.L.Anderson, I.E.Anderson. (Iowa State University, Iowa, USA.) It was reported that Ni-La-Sn alloy powders had been treated with NF, in a fluidized bed. This was to improve the performance of Ni-metal hydride batteries by preventing corrosion of the electrodes by formation of a fluoride coating which still allows transfer of H. Structures and performance were evaluated.
comprised Ti-Si solid solution, Ti,Si, and MgO. Mg,Si did not re-form. On heating MA powders Mg,Si and Ti,Si, formed at lower temperatures and at 1100°C there was TiN,,,. The findings were discussed. PRODUCTION OF METAL POWDERS BY IMPULSE ATOMIZATION H.Henein, J.B.Wiskel. (University of Alberta, Canada.) Use of impulse atomization to make powders of known size was reported. The technique was used to make a wide range of alloy powders. The structures were characterized and related to cooling rates with the aid of models for droplet solidification. Melt throughput was analysed from load cell measurements and related to process parameters.
Porous structures DEVELOPMENT
OF PM STEEL FOAMS
C.J.Yu et al. (Fraunhofer - USA, USA.) It was reported that steel foams, with a density of 3.5 g.cmm3, had been produced with relatively homogeneous and isotropic pore structures. The material was shown to have a high specific stiffness (stiffness:weight ratio). Mechanical properties were evaluated and possible application outlined. POWDER MATERIALS WITH ORIENTED PORE STRUCTURES L.Tuchinsky, R.Loutfy. (MER Corp, USA. 1 A method for production of metallic and ceramic materials, with oriented pores, for which extrusion is used, was described. The pores are in the form of micro-channels parallel to the extrusion direction or others. Channel size is from pm to mm dimensions. The properties are not typical of powders materials and may not be isotopic. Strength may be higher than for conventional PM materials with the same porosity. Applications were outlined.
SYNTHESIS OF LOW DENSITY TITANIUM-MAGNESIUM-SILICON ALLOYS
HIGH STRAIN RATE COMPRESSION OF METAL FOAMS PRODUCED BY PM
F.H.Froes et al. (University of Idaho, USA.) A low density Ti-Mg-Si alloy was prepared from blended elemental powders. Effects of heat treatment or mechanical alloying on phase formation were investigated. On heating to 500°C Si dissolved in the Ti and Mg,Si formed which dissociated at 950°C and Ti,Si, was then synthesized. Mg oxidized at 1100°C. On cooling the structure
I.W.Hall et al. (University of Delaware, USA.) Characteristics of PM metal foams were discussed with regard to stiffness to weight ratio, non-linear deformation behaviour and applications for efficient energy absorption in automobiles. High strain rate deformation properties of foams were investigated to evaluate crash energy absorbtion. Test results were presented for PM Al foams.
MPR September 2000 41
carbides
EFFECTS OF COBALT PARTICLE SIZE ON PROCESSING AND PROPERTIES OF TUNGSTEN CARBIDE-COBALT J.Harvi, D.F.Carroll. (OMG Americas, USA.) WC-Co alloys were discussed with reference to the use of fine WC powders, down to 0.2 pm. It was noted that processing and properties are influenced by the crystallite size of the Co binder. A summary of the effects of Co particle size on WC-Co made from superfine WC was presented for Co crystallite sizes of 0.4 to 1.5 pm. Suggestions were made for selection of Co particle size. SINTERING AIDS FOR LIQUID PHASE SINTERING OF FINE GRAIN TUNGSTEN CARBIDE-COBALT B.H.Kear et al. (Rutgers University, USA.) A study of sintering aids for WC-Co was described. VC and Cr,C, growth inhibitors were said to be solid solution forming in the Co binder phase. Above 1200°C the liquid phase formed was shown to contain more than one liquid phase and the inhibitor carbides could be uniformly distributed in the liquid at lower temperatures. The phenomenon was exploited in low temperature sintering of WC-Co. ASPECTS OF ULTRAFINE HARDMETAL SINTERING B.Lux et al. (Technical University of Vienna, Vienna, Austria.) The trend to use finer powders in making WC-Co was discussed with reference to rapid growth of WC grains which may occur during liquid phase sintering and the need to use growth inhibitors. Aspects of sintering, outgassing, spread of the binder phase, formation of liquid and liquid phase sintering were reviewed. Limits to WC grain size were assessed and alternative consolidation techniques were discussed. THFRMlT PROCESS FOR PRODUCTION OF TUNGSTEN CARBIDE J.D.Morris, C.J.Terry. (Kennametal Inc, USA.) It was reported that a thermit type process had been used to make WC directly from ore concentrates. The WC was shown to have properties suitable for application in hardfacing, hardmetals and PDC matrix composite powders. INFLUENCE OF BINDER CONSTITUTION ON SHAPE OF TUNGSTEN CARBIDE GRAINS
J.J.Oakes et al. (Teledyne Metalworking Products Inc, USA.) The morphology of WC grains in coarse grained WC-Co, prismatic with sharp edges, was discussed and shown to be dis-advantageous where there is crack initiation and propagation caused by thermal shock. It was reported that the addition of Ni or Cr to the Co binder resulted in more rounded WC grains giving a tougher material more resistant to cracks. Effects of process parameters on WC grain shape were investigated and the results were described. CEMENTED CARBIDES DOPED WITH RARE EARTHS C.Lin et al. (General Research Inst. for Non-Ferrous Metals, Beijing, China.) The addition of rare earths, to improve the performance of cemented carbides in cutting applications, was discussed. The additions were shown to increase tool life due to enhanced mechanical properties. The additions were reported to influence both hard phase and binder and to improve grain boundary structure. The rare earth additions were also shown to avoid the need for grain growth inhibitors even in ultrafine grained materials. A range of properties was described.
Powder production characterization
and
FLUORINATION OF LANTHANUMNICKEL-TIN POWDERS FOR BATTERY ELECTRODES M.L.Anderson, I.E.Anderson. (Iowa State University, Iowa, USA.) It was reported that Ni-La-Sn alloy powders had been treated with NF, in a fluidized bed. This was to improve the performance of Ni-metal hydride batteries by preventing corrosion of the electrodes by formation of a fluoride coating which still allows transfer of H. Structures and performance were evaluated.
comprised Ti-Si solid solution, Ti,Si, and MgO. Mg,Si did not re-form. On heating MA powders Mg,Si and Ti,Si, formed at lower temperatures and at 1100°C there was TiN,,,. The findings were discussed. PRODUCTION OF METAL POWDERS BY IMPULSE ATOMIZATION H.Henein, J.B.Wiskel. (University of Alberta, Canada.) Use of impulse atomization to make powders of known size was reported. The technique was used to make a wide range of alloy powders. The structures were characterized and related to cooling rates with the aid of models for droplet solidification. Melt throughput was analysed from load cell measurements and related to process parameters.
Porous structures DEVELOPMENT
OF PM STEEL FOAMS
C.J.Yu et al. (Fraunhofer - USA, USA.) It was reported that steel foams, with a density of 3.5 g.cmm3, had been produced with relatively homogeneous and isotropic pore structures. The material was shown to have a high specific stiffness (stiffness:weight ratio). Mechanical properties were evaluated and possible application outlined. POWDER MATERIALS WITH ORIENTED PORE STRUCTURES L.Tuchinsky, R.Loutfy. (MER Corp, USA. 1 A method for production of metallic and ceramic materials, with oriented pores, for which extrusion is used, was described. The pores are in the form of micro-channels parallel to the extrusion direction or others. Channel size is from pm to mm dimensions. The properties are not typical of powders materials and may not be isotopic. Strength may be higher than for conventional PM materials with the same porosity. Applications were outlined.
SYNTHESIS OF LOW DENSITY TITANIUM-MAGNESIUM-SILICON ALLOYS
HIGH STRAIN RATE COMPRESSION OF METAL FOAMS PRODUCED BY PM
F.H.Froes et al. (University of Idaho, USA.) A low density Ti-Mg-Si alloy was prepared from blended elemental powders. Effects of heat treatment or mechanical alloying on phase formation were investigated. On heating to 500°C Si dissolved in the Ti and Mg,Si formed which dissociated at 950°C and Ti,Si, was then synthesized. Mg oxidized at 1100°C. On cooling the structure
I.W.Hall et al. (University of Delaware, USA.) Characteristics of PM metal foams were discussed with regard to stiffness to weight ratio, non-linear deformation behaviour and applications for efficient energy absorption in automobiles. High strain rate deformation properties of foams were investigated to evaluate crash energy absorbtion. Test results were presented for PM Al foams.
MPR September 2000 41