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Water atomized fine powder technology
than 20 pm at low flow rates and gas pressures. The process was used to make fine Sn-Pb, Zn and A1 powders for use in solders and paints. Effects of process parameters on particle size distribution, structure and morphology were described. Production rates of 25 kg.h "1 with 90% of powder below 20 pm was reported.
Applications of ultrafine gas atomized metal powders G.Schulz. (Wideflow Metal Powder Production and EngineeringGmbH, Ohrdruf, Germany.) The need for ultrafine metal powders, produced at low cost, was noted. It was shown that a novel process, melt film atomization, can make powders, smaller than 10 pm in size, in a range of alloys. Applications were outlined.
Water atomized fine powder technology J.Hamill, C.Schade. (HoeganaesCorp, USA.) Developments in water atomization, for production of fine powders, were reported. Applications, particularly with binder systems, were reviewed.
Design of large scale powder production equipment M.Hohmann, SD.Pleier. (ALD Vacuum Technologies AG, Erlensee,FRG.) The demand for powders of high quality, with regard to purity, structure and spherical shape, was discussed with regard to bulk production methods. A n investigation of melting methods, vacuum induction melting and electroslag remelting, were used with inert gas atomization. Characteristics of the methods were described. Qualities of powder were compared.
Production of refractory metal powders by explosion of wire M.Umakoshi et al. (Kurume National College of Technology, Fukuoka,Japan,.) It was reported that wires of W, Mo, Nb and Ta had been exploded to powder in air or in Ar. The powders consisted of fine spherical particles of metal or oxide. Oxidation was suppressed in Ar. Particle sizes were 2.4 to 3.7 pm for Mo and 2.5 to 4.6 pm for W. Reduction was required to produce only metal particles.
Composite materials Microstructure and properties of alumina-titanium carbonitride composites K.Hayashi et al. (Universityof Tokyo, Tokyo,Japan.) Microstructure and properties of hot pressed A1203-TI(C,N) were investigated with regard to use as cutting tool materials and for wear
www.meta[-powder.net
resistance. The effects of N:C+N ratio and %TiC were studied. Cutting performance against steel was evaluated with regard to crater and flank wear. Comparison was made with AI203-TiC tool alloys.
be used to reinforce metal matrix composites. The most effective production method was sintering by infiltration of loose powders and hot pressing. Properties of some materials were described.
Tribological properties of aluminasilicon carbide nanocomposites
Synthesis of Ti matrix composites by in situ gas-solid reaction
K.Niihar et al. (Osaka University, Ibaraki,Japan.) A1203-SiC composites were hot pressed and mechanical and wear properties, in air and water, were measured to investigate the effects of SiC. Relationships between mechanical and wear properties were discussed. Worn surfaces were examined by scanning electron microscopy and found to show plastic deformation and trans- and inter-granular fractures.
H .Chunget al. (Ajou University, Kyung~, Korea.) It was reported that Ti matrix composites, reinforced with "13C, had been synthesized in situ by a gas/solid reaction process. Powders, without TiC, were cold pressed, reacted with CH 4 at elevated temperature, vacuum sintered and HIPed to full density. TIC was shown to be uniformly distributed and mechanical properties were said to be high.
Sintered AI-SiC composites for use in semiconductor devices
Fabrication of cubic zirconia composites with oxide and carbide reinforcements
S-I.Yamagata, A.Fukui. (Sumitomo Electric Industries Ltd, Japan.) The properties required for materials to be used as heat sinks in electronic devices - high thermal conductivity and low thermal expansion - were reviewed. It was reported that an A1-SiC material had been developed for this use. How this material meets the requirements was discussed with regard to control of properties by adjustments to composition.
Differential thermal analysis of AI-silicon carbide composites R.Orban et al. (Universityof Cluj-Napoca, Romania.) A1 alloy matrix-carbide composites were discussed with reference to use at elevated temperatures. Results of differential thermal analysis of PM composites were used to evaluate high temperature properties, which were found to be influenced by production conditions.
Structure-property relationships in aluminium matrix composites B.V.R.Bhat et al. (Defence Metallurgical Research Laboratory, Hyderabad, India.) A1 alloy matrix composites were reviewed with regard to effects of process conditions. A n investigation of 2124A1 alloy, reinforced with SiC particles, of different sizes, processed by vacuum hot pressing and hot extrusion, was described. Effects of material and process parameters on structure and properties were studied. Increased extrusion ratio was shown to increase mechanical properties, attributed to refinement and alignment of particles. Extruded flat samples showed anisotropy.
Ni base matrix composites reinforced with fused WC particles R.L.Orban et al. (Universityof Cluj-Napoca, Romania.) Fused tungsten carbide was shown to be a quasi-eutectoid of W C and W2C. This has higher hardness and toughness than W C alone. It was suggested that fused W C could
J.Hojo et al. (Kyushu University,Japan.) Development of cubic ZrO 2 composites reinforced with Ta203, La203, A1203 or SiC was described. Sintering was at 1600 °C in air. Second phases were formed by reaction between oxide additions and ZrO 2. Effects on mechanical properties were said to be beneficial.
Sintering Anisotropy of shrinkage in consolidation of powders E.Olevsky. (CaliforniaState University,San Diego, USA.) Anisotropy of shrinkage during deformation processing of powders was reviewed. The study considered shape change non-uniformity due to structure, morphology, gravity, the effect of container in isostatic pressing and pressure transmitting medium in quasi-isostatic pressing. Modelling based on continuum theory was used. Technological recommendations related to compact green shape and spatial density distributions were made.
Effect of milling on densification of molybdenum disilicide Y.D.Kim et al. (HanyangUniversity, Seoul, Korea.) Effects of milling on sintering of MoSi 2 powder, by spark plasma sintering, were investigated. Milling reduced powder from 10 pm to <1 pm in size. Sintering was at 1200- 1500 °C, heated at 20-200 °C.min "1 and held at temperature for 15 min. Structural evolution and densification were correlated with process conditions. Compacts sintered from milled powder had lower densities, 94-98%, than samples made from un-milled powder. This was attributed to contamination by O during milling, forming SiO 2 which dissociated, giving a gaseous phase during sintering.
MPR October 2OOl
47
Applications of ultrafine gas atomized metal powders G.Schulz. (Wideflow Metal Powder Production and EngineeringGmbH, Ohrdruf, Germany.) The need for ultrafine metal powders, produced at low cost, was noted. It was shown that a novel process, melt film atomization, can make powders, smaller than 10 pm in size, in a range of alloys. Applications were outlined.
Water atomized fine powder technology J.Hamill, C.Schade. (HoeganaesCorp, USA.) Developments in water atomization, for production of fine powders, were reported. Applications, particularly with binder systems, were reviewed.
Design of large scale powder production equipment M.Hohmann, SD.Pleier. (ALD Vacuum Technologies AG, Erlensee,FRG.) The demand for powders of high quality, with regard to purity, structure and spherical shape, was discussed with regard to bulk production methods. A n investigation of melting methods, vacuum induction melting and electroslag remelting, were used with inert gas atomization. Characteristics of the methods were described. Qualities of powder were compared.
Production of refractory metal powders by explosion of wire M.Umakoshi et al. (Kurume National College of Technology, Fukuoka,Japan,.) It was reported that wires of W, Mo, Nb and Ta had been exploded to powder in air or in Ar. The powders consisted of fine spherical particles of metal or oxide. Oxidation was suppressed in Ar. Particle sizes were 2.4 to 3.7 pm for Mo and 2.5 to 4.6 pm for W. Reduction was required to produce only metal particles.
Composite materials Microstructure and properties of alumina-titanium carbonitride composites K.Hayashi et al. (Universityof Tokyo, Tokyo,Japan.) Microstructure and properties of hot pressed A1203-TI(C,N) were investigated with regard to use as cutting tool materials and for wear
www.meta[-powder.net
resistance. The effects of N:C+N ratio and %TiC were studied. Cutting performance against steel was evaluated with regard to crater and flank wear. Comparison was made with AI203-TiC tool alloys.
be used to reinforce metal matrix composites. The most effective production method was sintering by infiltration of loose powders and hot pressing. Properties of some materials were described.
Tribological properties of aluminasilicon carbide nanocomposites
Synthesis of Ti matrix composites by in situ gas-solid reaction
K.Niihar et al. (Osaka University, Ibaraki,Japan.) A1203-SiC composites were hot pressed and mechanical and wear properties, in air and water, were measured to investigate the effects of SiC. Relationships between mechanical and wear properties were discussed. Worn surfaces were examined by scanning electron microscopy and found to show plastic deformation and trans- and inter-granular fractures.
H .Chunget al. (Ajou University, Kyung~, Korea.) It was reported that Ti matrix composites, reinforced with "13C, had been synthesized in situ by a gas/solid reaction process. Powders, without TiC, were cold pressed, reacted with CH 4 at elevated temperature, vacuum sintered and HIPed to full density. TIC was shown to be uniformly distributed and mechanical properties were said to be high.
Sintered AI-SiC composites for use in semiconductor devices
Fabrication of cubic zirconia composites with oxide and carbide reinforcements
S-I.Yamagata, A.Fukui. (Sumitomo Electric Industries Ltd, Japan.) The properties required for materials to be used as heat sinks in electronic devices - high thermal conductivity and low thermal expansion - were reviewed. It was reported that an A1-SiC material had been developed for this use. How this material meets the requirements was discussed with regard to control of properties by adjustments to composition.
Differential thermal analysis of AI-silicon carbide composites R.Orban et al. (Universityof Cluj-Napoca, Romania.) A1 alloy matrix-carbide composites were discussed with reference to use at elevated temperatures. Results of differential thermal analysis of PM composites were used to evaluate high temperature properties, which were found to be influenced by production conditions.
Structure-property relationships in aluminium matrix composites B.V.R.Bhat et al. (Defence Metallurgical Research Laboratory, Hyderabad, India.) A1 alloy matrix composites were reviewed with regard to effects of process conditions. A n investigation of 2124A1 alloy, reinforced with SiC particles, of different sizes, processed by vacuum hot pressing and hot extrusion, was described. Effects of material and process parameters on structure and properties were studied. Increased extrusion ratio was shown to increase mechanical properties, attributed to refinement and alignment of particles. Extruded flat samples showed anisotropy.
Ni base matrix composites reinforced with fused WC particles R.L.Orban et al. (Universityof Cluj-Napoca, Romania.) Fused tungsten carbide was shown to be a quasi-eutectoid of W C and W2C. This has higher hardness and toughness than W C alone. It was suggested that fused W C could
J.Hojo et al. (Kyushu University,Japan.) Development of cubic ZrO 2 composites reinforced with Ta203, La203, A1203 or SiC was described. Sintering was at 1600 °C in air. Second phases were formed by reaction between oxide additions and ZrO 2. Effects on mechanical properties were said to be beneficial.
Sintering Anisotropy of shrinkage in consolidation of powders E.Olevsky. (CaliforniaState University,San Diego, USA.) Anisotropy of shrinkage during deformation processing of powders was reviewed. The study considered shape change non-uniformity due to structure, morphology, gravity, the effect of container in isostatic pressing and pressure transmitting medium in quasi-isostatic pressing. Modelling based on continuum theory was used. Technological recommendations related to compact green shape and spatial density distributions were made.
Effect of milling on densification of molybdenum disilicide Y.D.Kim et al. (HanyangUniversity, Seoul, Korea.) Effects of milling on sintering of MoSi 2 powder, by spark plasma sintering, were investigated. Milling reduced powder from 10 pm to <1 pm in size. Sintering was at 1200- 1500 °C, heated at 20-200 °C.min "1 and held at temperature for 15 min. Structural evolution and densification were correlated with process conditions. Compacts sintered from milled powder had lower densities, 94-98%, than samples made from un-milled powder. This was attributed to contamination by O during milling, forming SiO 2 which dissociated, giving a gaseous phase during sintering.
MPR October 2OOl
47