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User-friendly aspects of compaction modelling
abstracts could bc reduced by up to 70%. The alloy design aspect was to enhance microstructural homogeneity and toughness in finegrained materials. (;rain growth inhibitors, VC and Cr2C3, were used. Mechanical property variations were reduced.
High-performance PM materials Chemical behaviour of tungstenlanthanide composite materials K.Cadoret et al. (Thales Electron Devices, Thonon-les-Bains, France.) Crystallography and chemistry of W-lanthanide composite materials, for use as cathodes in powder grid tubes, was described. High-temperature X-ray diffraction and synchrotron radiation werc used to investigate phase formation and phase transitions in real time during heatmg and carburisation. Phase equilibria were deduced for WO~-La203. The W-lanthanide is shown to have improved stability and chemical homogeneity on cathode surfaces.
Mechanical properties of nickel aluminide made from mechanically alloyed or milled powders Y.D.Kim et al. (Hanyang University, Korea.) Samples of mechanically alloyed NiAI powder and milled Ni-A1 powder mixture were spark-plasma sintered. Densification behaviour and mechanical properties were determined. Densification characteristics were different for the two materials. Mechanically alloyed powder required 800"C to 900°C for densification to 98°/,, and the mixed milled powder started to densifv at 300°C and reached 99%. Structurcs of both were mamly NiA] with Ni~AI as a second phase. Fine grain size was found in the machanically alloyed samples. Mechanical properties were described.
Carburisation of molybdenumlanthanide materials W.Jinshu et al. (Beijing Polytechnic University, Beijing, China.) Carburisation of Mo-La20 ~ cathode materials was investigated by thermal analysis. The process was found be threestage. The first is controlled by chemical reaction, the second by chemical reaction and diffusion and the third bv diffusion alone. Activation energies and rate constants for the process were calculated.
36
February 2003
Preparation of nickel aluminide materials C.D.Vidu et al. (METAV S.A., Bucharest, Romania.) Synthesis of NiA1, five mixes, and Ni~AI, four mixes, from elemental powders was described. Various process parameters were investigated. The consolidated materials were characterised for microstructure and properties that were correlated with process conditions. It was suggested that these materials could replace Ni base alloys in aerospace high-temperature applications.
Shape distortion and dimensional precision in liquid-phase sintering of tungsten heavy alloys R.M.German et al. (Pennsylvania State University, USA.) Densification and shape distortion in liquid phasc sintered W-Ni-Cu alloys was investigated with regard to microstructural parameters. A pore forming agent, ethylene-bissteaaramide, was added, the amount added controlling the porosity and particle size the pore size. The tungsten content was varied and the Ni: Cu ratio was altered to change the dihedral angle. A distortion parameter was obtained by measurements. It was shown that distortion decreases with increase in solid volume, %W, and dihedral anglc. Initial porosity and pore size were found to have no effect on distortion. Suggestions were made for improvements to liquid-phase sintering.
General topics Methods for productionof nanostructured aluminium nitride ceramics P.Kisly et al. (Inst. for Superhard Materials, Kiev, Ukraine.) Sintering nf fine and coarse AIN powders, in tbe range 1000°C to 2000°C, was investigated. Topics discussed were; high rate of densification at small particle sizes and formation of AI oxy-nitride; mechanisms of grain growth recrystallisation at different stages of sintering; phase formation and formation of a polycrystaline microstructure during sintering after shock wave treatment. Formation of grains with high dislocation density was observed.
Preparation and properties of nano-dispersed carbonitrides of transition metals I.Zalite, J.Krastins. (Riga Technical University, Salaspils, Latvia.) It was reported that nano-dispersed carbonitridc powders, 50 to 200nm in size', of
one or more IV to VI transition metals, Ti, Nb, Cr etc, had been prepared by plasmachemical synthesis. Particles were shown to be single crystals with a high concentration of lattice defects. The powders had high chemical activity and sintered rapidly at low sintering temperatures. Examples were given.
Explosive compaction of nano-crystalline alumina powder P.Weimar, R.Pruemmer. (Karlsruhe University, Karlsruhe, Germany.) It was noted that nano-ceramics, grain sizes below 100nm, have special properties: high hardness, low friction and very small pores. This is difficult to retain during conventional processing. It was suggested that this problem could be solved by explosive compaction. Explosive compaction of nano-AI20.3 showed that near-full density could be attained. Electron microscopy showed that phase transitions occurred and sub-grain size diminished.
EURO PM 2001. The following Abstracts are of papers presented at the 2001 European Congress on Powder Metallurgy, which was held in Nice, France, in October 2001.
Compaction modelling Materials characterisation modelling and validation for a multilevel ferrous PM part P.Brewin et al. (EPMA, Shrewsbury, UK.) A case study of compaction of a complex multi-level 'H' shaped ferrous part was described. Yield and friction properties of the powder were characterised., compaction was simulated and parts were produced. Computed and experimental results were compared. Density distribution agreed within 0.3gm/cm -~ to 0.5gm/cm "3 and punch force levels agreed within 20%.
User-friendly aspects of compaction modelling R.Maassen et al. (GKN Sinter Metals Service GmbH, Radevormwald, Germany.) It was noted that pressing of complex parts can be difficult, faults include undesired density variations and cracks in green compacts. Development of process modelling allows simulation of die compaction including prediction of density variations
metal-powder.net
High-performance PM materials Chemical behaviour of tungstenlanthanide composite materials K.Cadoret et al. (Thales Electron Devices, Thonon-les-Bains, France.) Crystallography and chemistry of W-lanthanide composite materials, for use as cathodes in powder grid tubes, was described. High-temperature X-ray diffraction and synchrotron radiation werc used to investigate phase formation and phase transitions in real time during heatmg and carburisation. Phase equilibria were deduced for WO~-La203. The W-lanthanide is shown to have improved stability and chemical homogeneity on cathode surfaces.
Mechanical properties of nickel aluminide made from mechanically alloyed or milled powders Y.D.Kim et al. (Hanyang University, Korea.) Samples of mechanically alloyed NiAI powder and milled Ni-A1 powder mixture were spark-plasma sintered. Densification behaviour and mechanical properties were determined. Densification characteristics were different for the two materials. Mechanically alloyed powder required 800"C to 900°C for densification to 98°/,, and the mixed milled powder started to densifv at 300°C and reached 99%. Structurcs of both were mamly NiA] with Ni~AI as a second phase. Fine grain size was found in the machanically alloyed samples. Mechanical properties were described.
Carburisation of molybdenumlanthanide materials W.Jinshu et al. (Beijing Polytechnic University, Beijing, China.) Carburisation of Mo-La20 ~ cathode materials was investigated by thermal analysis. The process was found be threestage. The first is controlled by chemical reaction, the second by chemical reaction and diffusion and the third bv diffusion alone. Activation energies and rate constants for the process were calculated.
36
February 2003
Preparation of nickel aluminide materials C.D.Vidu et al. (METAV S.A., Bucharest, Romania.) Synthesis of NiA1, five mixes, and Ni~AI, four mixes, from elemental powders was described. Various process parameters were investigated. The consolidated materials were characterised for microstructure and properties that were correlated with process conditions. It was suggested that these materials could replace Ni base alloys in aerospace high-temperature applications.
Shape distortion and dimensional precision in liquid-phase sintering of tungsten heavy alloys R.M.German et al. (Pennsylvania State University, USA.) Densification and shape distortion in liquid phasc sintered W-Ni-Cu alloys was investigated with regard to microstructural parameters. A pore forming agent, ethylene-bissteaaramide, was added, the amount added controlling the porosity and particle size the pore size. The tungsten content was varied and the Ni: Cu ratio was altered to change the dihedral angle. A distortion parameter was obtained by measurements. It was shown that distortion decreases with increase in solid volume, %W, and dihedral anglc. Initial porosity and pore size were found to have no effect on distortion. Suggestions were made for improvements to liquid-phase sintering.
General topics Methods for productionof nanostructured aluminium nitride ceramics P.Kisly et al. (Inst. for Superhard Materials, Kiev, Ukraine.) Sintering nf fine and coarse AIN powders, in tbe range 1000°C to 2000°C, was investigated. Topics discussed were; high rate of densification at small particle sizes and formation of AI oxy-nitride; mechanisms of grain growth recrystallisation at different stages of sintering; phase formation and formation of a polycrystaline microstructure during sintering after shock wave treatment. Formation of grains with high dislocation density was observed.
Preparation and properties of nano-dispersed carbonitrides of transition metals I.Zalite, J.Krastins. (Riga Technical University, Salaspils, Latvia.) It was reported that nano-dispersed carbonitridc powders, 50 to 200nm in size', of
one or more IV to VI transition metals, Ti, Nb, Cr etc, had been prepared by plasmachemical synthesis. Particles were shown to be single crystals with a high concentration of lattice defects. The powders had high chemical activity and sintered rapidly at low sintering temperatures. Examples were given.
Explosive compaction of nano-crystalline alumina powder P.Weimar, R.Pruemmer. (Karlsruhe University, Karlsruhe, Germany.) It was noted that nano-ceramics, grain sizes below 100nm, have special properties: high hardness, low friction and very small pores. This is difficult to retain during conventional processing. It was suggested that this problem could be solved by explosive compaction. Explosive compaction of nano-AI20.3 showed that near-full density could be attained. Electron microscopy showed that phase transitions occurred and sub-grain size diminished.
EURO PM 2001. The following Abstracts are of papers presented at the 2001 European Congress on Powder Metallurgy, which was held in Nice, France, in October 2001.
Compaction modelling Materials characterisation modelling and validation for a multilevel ferrous PM part P.Brewin et al. (EPMA, Shrewsbury, UK.) A case study of compaction of a complex multi-level 'H' shaped ferrous part was described. Yield and friction properties of the powder were characterised., compaction was simulated and parts were produced. Computed and experimental results were compared. Density distribution agreed within 0.3gm/cm -~ to 0.5gm/cm "3 and punch force levels agreed within 20%.
User-friendly aspects of compaction modelling R.Maassen et al. (GKN Sinter Metals Service GmbH, Radevormwald, Germany.) It was noted that pressing of complex parts can be difficult, faults include undesired density variations and cracks in green compacts. Development of process modelling allows simulation of die compaction including prediction of density variations
metal-powder.net