- Email: [email protected]
Production of aluminium powder by atomization
PM
Powder production P R O D U C T I O N OF A L U M I N I U M P O W D E R BY ATOMIZATION
L. Garcia et al. (National Centre for Metallurgical Investigations, Madrid, Spain.) Revista Metall. Madrid, Vol 32, No 6, 1996, 391-396. (In Spanish). It is reported that a pilot scale plant had been used for atomization of A1 powders. The powders were characterized for particle size distribution and used for isothermally sintered parts at a range of temperature and dwell times. N E W T E C H N O L O G Y FOR P R O D U C I N G C O M P O S I T E P O W D E R S BY P O W E R SPUTTERING
K.Kojima et al. (Nisshin Steel, Japan.) Nisshin Steel Tech. Rep., Vol 73, 1996, 44-54. (In Japanese.) Production of composite-coated metal powders by a sputtering technique, which can be used for non-metallic core materials, is reported. The process and equipment are described. Examples, W-coated diamond powder and metal-coated non-metallic powders, are given.
P R E P A R A T I O N OF U L T R A F I N E ALUMINIUM POWDER
H.Yan et al. (Central South University of Technology, Hunan, China.) J. Central South University Technol., Vol 27, No 1, 1996, 65-69. (In Chinese.) Preparation of A1 powder by evaporation/condensation was investigated. Particle size is shown to be controlled by the growth mechanism and can be controlled by changes in process conditions. Spherical or hexagonal powders with mean diameters 0.15 to 0.62 pm were produced. The process could be accelerated by blowing He over the molten A1. Maximum evaporation rate was 8.2 g.min 1. The structure was face-centred cubic. O P E R A T I O N OF THE PLASMA ROTATING E L E C T R O D E P R O C E S S PARTICLE E J E C T I O N
M.Tokizane et al. (Ritsumeikan University, Kasatsu, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 907-912. (In Japanese.)
36 MPR April 1998
LITERATURE
REVIEW
A study of the ejection of droplets from the edge of the molten surface during plasma rotating electrode atomization is described. The force restraining ejection is shown to be surface tension and is affected by local surface shape. At low plasma potential particle size was smaller. Experiments were carried out with different electrodes.
Sintering
wear resistance of the oxide film. While this is intact, wear resistance is high and greater than that conferred by heat treatment or surface hardening. Durability is influenced by alloy composition and is reduced by presence of Cu. F A T I G U E OF H I G H - S T R E N G T H INJECTION MOULDED SINTERED ALLOY S T E E L S
P.E.McHugh, H.Riedel. (Fraunhofer Inst, Freiburg, Germany.) Acta Mater., Vol 45, No 7, 1997, 2995-3003. A model for liquid phase sintering is examined. The model accounts for densification by particle rearrangement and contact flattening, the liquid phase aiding diffusion. The model is applied to sintering of Si3N 4 and WC-Co. Conclusions are drawn concerning the importance of the model in prediction of shape distortions.
T.Baba et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 863867. (In Japanese.) Fatigue properties of MIM 4600 steels, 1.8%Ni-0.5%Mo-0.2%Mn, made from elemental powders, were investigated. The structures are reported to be fine but heterogeneous with segregation of Ni. Higher fatigue strength was found than in conventional sintered steels. This is attributed to higher density and spheroidization of pores. After heat treatment the Ni-rich zones were martensitic or retained austenite in a ferritic matrix.
Aluminium
Molybdenum
D E V E L O P M E N T S OF R A P I D L Y S O L I D I F I E D A L U M I N I U M ALLOYS
F R A C T U R E T O U G H N E S S OF MOLYBDENUM SHEET UNDER DUCTILE-BRITTLE TRANSITION
LIQUID P H A S E S I N T E R I N G MODEL A P P L I C A T I O N TO SILICON NITRIDE AND TUNGSTEN CARBIDE-COBALT
Y.Takeda et al. (Sumitomo Electric Industries, Itami, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 873-878. (In Japanese.) Developments in rapidly solidified (RS) A1 alloys are reported. RS allows refinement of structures and expands alloy composition limits. RS ternary A1-Si-X alloys are shown to have better properties than conventional PM alloys. Powders were processed to near net shape parts. The method used reduced surface films which impede sintering.
Iron and steel T R I B O L O G I C A L B E H A V I O U R OF STEAM-TREATED FERROUS PARTS
A.Molinari, G.Straffelini. (University of Trento, Trento, Italy.) Int. J. Powder Metall., Vol 33, No 5, 1997, 55-62. The tribological properties of steamtreated Fe parts were investigated with respect to wear damage as a function of alloy composition. The concept of surface durability is defined and related to
A.Y.Koval et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Int. J. Refractor)' Metals Hard Mater., Vol 15, No 4, 1997, 223-226. Fracture toughness of Mo sheet was investigated in the range -196 to 300°C. The behaviour in attributed to changes in the crack nucleation mechanism. S E C O N D A R Y GRAIN GROWTH RATE IN M O L Y B D E N U M S H E E T
T.Fujii et al. (National Research Inst. for Metals, Tsukuba, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 879-884. (In Japanese.) Recrystallization of Mo sheet, doped with CaO and MgO was investigated. Orientation relationships are described and activation energies calculated. Temperature dependence of grain growth rate is given. It is shown that growth rates of secondary recrystallized grains are related to the orientation relationships between primary and secondary grains and structures arising from rolling procedures.
Powder production P R O D U C T I O N OF A L U M I N I U M P O W D E R BY ATOMIZATION
L. Garcia et al. (National Centre for Metallurgical Investigations, Madrid, Spain.) Revista Metall. Madrid, Vol 32, No 6, 1996, 391-396. (In Spanish). It is reported that a pilot scale plant had been used for atomization of A1 powders. The powders were characterized for particle size distribution and used for isothermally sintered parts at a range of temperature and dwell times. N E W T E C H N O L O G Y FOR P R O D U C I N G C O M P O S I T E P O W D E R S BY P O W E R SPUTTERING
K.Kojima et al. (Nisshin Steel, Japan.) Nisshin Steel Tech. Rep., Vol 73, 1996, 44-54. (In Japanese.) Production of composite-coated metal powders by a sputtering technique, which can be used for non-metallic core materials, is reported. The process and equipment are described. Examples, W-coated diamond powder and metal-coated non-metallic powders, are given.
P R E P A R A T I O N OF U L T R A F I N E ALUMINIUM POWDER
H.Yan et al. (Central South University of Technology, Hunan, China.) J. Central South University Technol., Vol 27, No 1, 1996, 65-69. (In Chinese.) Preparation of A1 powder by evaporation/condensation was investigated. Particle size is shown to be controlled by the growth mechanism and can be controlled by changes in process conditions. Spherical or hexagonal powders with mean diameters 0.15 to 0.62 pm were produced. The process could be accelerated by blowing He over the molten A1. Maximum evaporation rate was 8.2 g.min 1. The structure was face-centred cubic. O P E R A T I O N OF THE PLASMA ROTATING E L E C T R O D E P R O C E S S PARTICLE E J E C T I O N
M.Tokizane et al. (Ritsumeikan University, Kasatsu, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 907-912. (In Japanese.)
36 MPR April 1998
LITERATURE
REVIEW
A study of the ejection of droplets from the edge of the molten surface during plasma rotating electrode atomization is described. The force restraining ejection is shown to be surface tension and is affected by local surface shape. At low plasma potential particle size was smaller. Experiments were carried out with different electrodes.
Sintering
wear resistance of the oxide film. While this is intact, wear resistance is high and greater than that conferred by heat treatment or surface hardening. Durability is influenced by alloy composition and is reduced by presence of Cu. F A T I G U E OF H I G H - S T R E N G T H INJECTION MOULDED SINTERED ALLOY S T E E L S
P.E.McHugh, H.Riedel. (Fraunhofer Inst, Freiburg, Germany.) Acta Mater., Vol 45, No 7, 1997, 2995-3003. A model for liquid phase sintering is examined. The model accounts for densification by particle rearrangement and contact flattening, the liquid phase aiding diffusion. The model is applied to sintering of Si3N 4 and WC-Co. Conclusions are drawn concerning the importance of the model in prediction of shape distortions.
T.Baba et al. (Kumamoto University, Kumamoto, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 863867. (In Japanese.) Fatigue properties of MIM 4600 steels, 1.8%Ni-0.5%Mo-0.2%Mn, made from elemental powders, were investigated. The structures are reported to be fine but heterogeneous with segregation of Ni. Higher fatigue strength was found than in conventional sintered steels. This is attributed to higher density and spheroidization of pores. After heat treatment the Ni-rich zones were martensitic or retained austenite in a ferritic matrix.
Aluminium
Molybdenum
D E V E L O P M E N T S OF R A P I D L Y S O L I D I F I E D A L U M I N I U M ALLOYS
F R A C T U R E T O U G H N E S S OF MOLYBDENUM SHEET UNDER DUCTILE-BRITTLE TRANSITION
LIQUID P H A S E S I N T E R I N G MODEL A P P L I C A T I O N TO SILICON NITRIDE AND TUNGSTEN CARBIDE-COBALT
Y.Takeda et al. (Sumitomo Electric Industries, Itami, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 873-878. (In Japanese.) Developments in rapidly solidified (RS) A1 alloys are reported. RS allows refinement of structures and expands alloy composition limits. RS ternary A1-Si-X alloys are shown to have better properties than conventional PM alloys. Powders were processed to near net shape parts. The method used reduced surface films which impede sintering.
Iron and steel T R I B O L O G I C A L B E H A V I O U R OF STEAM-TREATED FERROUS PARTS
A.Molinari, G.Straffelini. (University of Trento, Trento, Italy.) Int. J. Powder Metall., Vol 33, No 5, 1997, 55-62. The tribological properties of steamtreated Fe parts were investigated with respect to wear damage as a function of alloy composition. The concept of surface durability is defined and related to
A.Y.Koval et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Int. J. Refractor)' Metals Hard Mater., Vol 15, No 4, 1997, 223-226. Fracture toughness of Mo sheet was investigated in the range -196 to 300°C. The behaviour in attributed to changes in the crack nucleation mechanism. S E C O N D A R Y GRAIN GROWTH RATE IN M O L Y B D E N U M S H E E T
T.Fujii et al. (National Research Inst. for Metals, Tsukuba, Japan.) J. Jpn. Soc. Powder Powder Metall., Vol 43, No 7, 1996, 879-884. (In Japanese.) Recrystallization of Mo sheet, doped with CaO and MgO was investigated. Orientation relationships are described and activation energies calculated. Temperature dependence of grain growth rate is given. It is shown that growth rates of secondary recrystallized grains are related to the orientation relationships between primary and secondary grains and structures arising from rolling procedures.