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Distortion in a sintered aluminium alloy
A plasticity model for metal powder
forming A.R.KI~oei, R. W.Lewis. (University of Wales, Swansea, UK.) Int. J. Plasticity, Vol 17, No 12, 2001,1659-1692.
A double surface plasticity model for nonlinear behaviour of powders is developed. Yielding, friction, densification strain and geometrical hardening during compaction are considered. Solution yields data on powder displacement and enables establishment of stress state and densification. A hardening rule defines dependence of yield surface on amount of plastic strain. A finite element model is used to simuiate production of a part,
Cold plastic compaction of powders R.M.McMeeking P.R.Heyliger. (Colorado Stare University, USA.) J. M ech. Physics Solids, Vo149, No 9, 2001,2031-2054.
A network model for an aggregate of equal sized p[astic spheres is used to study compaction of powders. The collection of particles is modelled as a network of axial forces, rotated in space, varying in magnitude and updated as new j unctions form and positions of particles change. Response to isostatic and closed die compaction is studied for stress/strain behaviour and to determine the nature of the yield surfiaces.
Mathematical model for cooling and rapid solidification of molten metal droplets U.Fritsching et al. (University of Bremen, Bremen, Germany.) Int. J. Thermal Sciences, Vo139, No l, 2000, 53-62.
Spray forming is described as me]ting, atomization into droplets, rapid cooling and deposition on the substrate. The properties of the deposit are dependent on the state of the droplets at the instant of deposition. Smal[est particles may be solid and larger particles may be liquid or partly solid. A model to describe cooling and solidification of droplets is presented. It is shown that it is possible to calcu[ate temperature and volume fraction of solid in particles related to process parameters and time of flight.
Loading limit design for porous sintered metal machine elements A.G.Mamalis et at. (National Technical University of Athens, Greece.) J. Mater. Process. Technol., Vol 98, 2000, 335-342.
A plasticity theory for porous sintered metals, taking porosity and micro-defects into account, is used to calculate loading limit conditions for elasto-plastic deformation. A new yield function for porous materials is used to simulate consolidation taking porosity at each stage of deformation into account. This is shown to be useful for load limit design and production of parts in porous materials. The model is validated by reference to machine parts.
Aluminium Distortion in a sintered aluminium alloy G.B.Schaffer, S.HHuo. (University of Queensland, Australia.) PowderMetall., Vol 43, No 2, 2000, 163172.
Distortion in 7000 series A1 alloys, made from elemental powders, is discussed and is shown to be due to uneven green density although AI is soft and readily compacted. It is reported that increased compaction pressure, giving more uniform green density, reduces distortion without affecting tensile properties.
Manufacture and metallurgical fundamentals of PM aluminium structural parts C.Lall, W.Heath. (Metal Powder Products Co., Cannel, USA.) lnt J. Powder Metall., Vol 36, No 6, 2000, 4550.
Growth in the use of PM A1 structural parts in automotive applications is discussed and is shown to have induced development ofAl cam caps, made by a press-sinter-repress route. Effects of alloy additions and compositions are reviewed. PM AI is assessed with regard to availability of raw materials, current and potential products and applications.
Mechanical and electropolishing methods were compared for effects on ductility of pure Cr, tested in different environments, vacuum, air and water. Ductility of mechanically polished Cr increased in water but not electropolished metal. This is discussed in terms of surface structures where slip could occur in mechanically polished suffaces.
Iron and steel Electrical conductivity and microstructure of sintered ferrous materials A.Siomchi, H.Danninger. (University of Technology, Vienna, Austria.) Powder Metall., Vol 43, No 3, 2000, 209.218.
Electrical conductivity, as a method of describing microstructure of sintered Fe, was investigated as a function of process temperatures. Relationships between formation of sintering contacts, lubricants and mechanical properties were evaluated by determination of conductivity and load-bearing ability. Porosity, grain growth and sintering temperature were assessed. Conductivity increased during delubrication, it is shown that mechanical properties can be predicted from the conductivity.
Ultra-lightweight aluminium foams for automotive applications
Effects of boron and silicon on liquid phase sintering of PM ferritic stainless steels
T.D.Claar et al. (Fraunhofer USA Centre, Newark, USA.) lnt J. Powder Metall., Vol 36, No 6, 2000, 6173.
H.Horie et al. (Iwate University, Morioka, Japan.) J.Japan Soc. Pow&rlPowderMetalI., Vol 47, No 10, 2000, 1091-1096. InJapanese.
Ultra-lightweight metal foams are reviewed with regard to properties and are considered for automotive applications. Lightness, specific stiffness and energy absorption are considered. Applications in vehicles for weight reduction, deereased fuel consurnption and improved mobility are described.
Effects of Si and B on liquid phase sintering of 430L stainless sted were investigated at 1200°C, 1250°C and 1300°C. Samples with 0.2%b and 2%Si, sintered at 130(Y»C had an increase in strength to 508MPa and 97% density without increase in ductility. These are attributed to eutectic reaction between matrix and borides and solid solution hardening of the matrix by Si. Corrosion resistance was enhanced by sintering at 1300°C but not at 1250°C.
Chromium Study of carbothermal reduction of chromium oxide L.M. Berger et al. (Fraunhofer Inst. Ceramics and Sintered Mater., Dresden, Gert~~any.) Int. J. Refract. Metals/Hard Mater., Vo119, No 2, 2001, 109-121.
Reduction of Cr20 3, in stoichiometric proportions to make Cr3C 2, by three types of C, was investigated. Evolution of CO was raonitored and products were characterised. Cr3C 2 and Cr2C3, with Cr7C 3 and Cr23C 6 at intermediate stages, were detected in the products. C black was the most effective reductant. There was substantial grain growth above 1200°C,
Near net shaping of mechanically alloyed iron-chromium K.Kobayashi et al. (National lndustrial Resear«h lnsz., Nagoya, Japan.) J.Japan Soc. PowderlPowderMetall., Vol 47, No 10, 2000, 1097-1101. ln Japanese.
Elemental Fe-48wt%Cr powders were mechanically alloyed for 5 hours and are shown to be Fe-Cr solid solution. Powder was sintered by pulsed current sintering at 800°C for live minutes. The sintered al[oy was Fe-Cr solid solution with a grain size of lmm. Tensile strength was 870MPa with 20% elongation.
Effects of surface polishing and environment on ductility of chromium
Manufacture of silicon carbide reinforced steels by spray forming
Y.Matsumoto et aI. (Oita National CoIlege of TechnoIogy, Oita, Japan.) lnt. J. Refract. Metals/Hard Mater., Vol 19, No 2, 2001, 123-129.
J .Banhart, H .Grützner. (Fraunhofer lnst. Manuf./Advanced Mater., Bremen, Germany.) PM Science/Technol. Briefs, Vol 2, No 3, 2000, 5-8.
www.metal-powder.net
MPR March 2002 i
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forming A.R.KI~oei, R. W.Lewis. (University of Wales, Swansea, UK.) Int. J. Plasticity, Vol 17, No 12, 2001,1659-1692.
A double surface plasticity model for nonlinear behaviour of powders is developed. Yielding, friction, densification strain and geometrical hardening during compaction are considered. Solution yields data on powder displacement and enables establishment of stress state and densification. A hardening rule defines dependence of yield surface on amount of plastic strain. A finite element model is used to simuiate production of a part,
Cold plastic compaction of powders R.M.McMeeking P.R.Heyliger. (Colorado Stare University, USA.) J. M ech. Physics Solids, Vo149, No 9, 2001,2031-2054.
A network model for an aggregate of equal sized p[astic spheres is used to study compaction of powders. The collection of particles is modelled as a network of axial forces, rotated in space, varying in magnitude and updated as new j unctions form and positions of particles change. Response to isostatic and closed die compaction is studied for stress/strain behaviour and to determine the nature of the yield surfiaces.
Mathematical model for cooling and rapid solidification of molten metal droplets U.Fritsching et al. (University of Bremen, Bremen, Germany.) Int. J. Thermal Sciences, Vo139, No l, 2000, 53-62.
Spray forming is described as me]ting, atomization into droplets, rapid cooling and deposition on the substrate. The properties of the deposit are dependent on the state of the droplets at the instant of deposition. Smal[est particles may be solid and larger particles may be liquid or partly solid. A model to describe cooling and solidification of droplets is presented. It is shown that it is possible to calcu[ate temperature and volume fraction of solid in particles related to process parameters and time of flight.
Loading limit design for porous sintered metal machine elements A.G.Mamalis et at. (National Technical University of Athens, Greece.) J. Mater. Process. Technol., Vol 98, 2000, 335-342.
A plasticity theory for porous sintered metals, taking porosity and micro-defects into account, is used to calculate loading limit conditions for elasto-plastic deformation. A new yield function for porous materials is used to simulate consolidation taking porosity at each stage of deformation into account. This is shown to be useful for load limit design and production of parts in porous materials. The model is validated by reference to machine parts.
Aluminium Distortion in a sintered aluminium alloy G.B.Schaffer, S.HHuo. (University of Queensland, Australia.) PowderMetall., Vol 43, No 2, 2000, 163172.
Distortion in 7000 series A1 alloys, made from elemental powders, is discussed and is shown to be due to uneven green density although AI is soft and readily compacted. It is reported that increased compaction pressure, giving more uniform green density, reduces distortion without affecting tensile properties.
Manufacture and metallurgical fundamentals of PM aluminium structural parts C.Lall, W.Heath. (Metal Powder Products Co., Cannel, USA.) lnt J. Powder Metall., Vol 36, No 6, 2000, 4550.
Growth in the use of PM A1 structural parts in automotive applications is discussed and is shown to have induced development ofAl cam caps, made by a press-sinter-repress route. Effects of alloy additions and compositions are reviewed. PM AI is assessed with regard to availability of raw materials, current and potential products and applications.
Mechanical and electropolishing methods were compared for effects on ductility of pure Cr, tested in different environments, vacuum, air and water. Ductility of mechanically polished Cr increased in water but not electropolished metal. This is discussed in terms of surface structures where slip could occur in mechanically polished suffaces.
Iron and steel Electrical conductivity and microstructure of sintered ferrous materials A.Siomchi, H.Danninger. (University of Technology, Vienna, Austria.) Powder Metall., Vol 43, No 3, 2000, 209.218.
Electrical conductivity, as a method of describing microstructure of sintered Fe, was investigated as a function of process temperatures. Relationships between formation of sintering contacts, lubricants and mechanical properties were evaluated by determination of conductivity and load-bearing ability. Porosity, grain growth and sintering temperature were assessed. Conductivity increased during delubrication, it is shown that mechanical properties can be predicted from the conductivity.
Ultra-lightweight aluminium foams for automotive applications
Effects of boron and silicon on liquid phase sintering of PM ferritic stainless steels
T.D.Claar et al. (Fraunhofer USA Centre, Newark, USA.) lnt J. Powder Metall., Vol 36, No 6, 2000, 6173.
H.Horie et al. (Iwate University, Morioka, Japan.) J.Japan Soc. Pow&rlPowderMetalI., Vol 47, No 10, 2000, 1091-1096. InJapanese.
Ultra-lightweight metal foams are reviewed with regard to properties and are considered for automotive applications. Lightness, specific stiffness and energy absorption are considered. Applications in vehicles for weight reduction, deereased fuel consurnption and improved mobility are described.
Effects of Si and B on liquid phase sintering of 430L stainless sted were investigated at 1200°C, 1250°C and 1300°C. Samples with 0.2%b and 2%Si, sintered at 130(Y»C had an increase in strength to 508MPa and 97% density without increase in ductility. These are attributed to eutectic reaction between matrix and borides and solid solution hardening of the matrix by Si. Corrosion resistance was enhanced by sintering at 1300°C but not at 1250°C.
Chromium Study of carbothermal reduction of chromium oxide L.M. Berger et al. (Fraunhofer Inst. Ceramics and Sintered Mater., Dresden, Gert~~any.) Int. J. Refract. Metals/Hard Mater., Vo119, No 2, 2001, 109-121.
Reduction of Cr20 3, in stoichiometric proportions to make Cr3C 2, by three types of C, was investigated. Evolution of CO was raonitored and products were characterised. Cr3C 2 and Cr2C3, with Cr7C 3 and Cr23C 6 at intermediate stages, were detected in the products. C black was the most effective reductant. There was substantial grain growth above 1200°C,
Near net shaping of mechanically alloyed iron-chromium K.Kobayashi et al. (National lndustrial Resear«h lnsz., Nagoya, Japan.) J.Japan Soc. PowderlPowderMetall., Vol 47, No 10, 2000, 1097-1101. ln Japanese.
Elemental Fe-48wt%Cr powders were mechanically alloyed for 5 hours and are shown to be Fe-Cr solid solution. Powder was sintered by pulsed current sintering at 800°C for live minutes. The sintered al[oy was Fe-Cr solid solution with a grain size of lmm. Tensile strength was 870MPa with 20% elongation.
Effects of surface polishing and environment on ductility of chromium
Manufacture of silicon carbide reinforced steels by spray forming
Y.Matsumoto et aI. (Oita National CoIlege of TechnoIogy, Oita, Japan.) lnt. J. Refract. Metals/Hard Mater., Vol 19, No 2, 2001, 123-129.
J .Banhart, H .Grützner. (Fraunhofer lnst. Manuf./Advanced Mater., Bremen, Germany.) PM Science/Technol. Briefs, Vol 2, No 3, 2000, 5-8.
www.metal-powder.net
MPR March 2002 i
nu
i
53