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Hot explosive compaction of molybdenum-titanium powders
Pressing SIMULATION AND COMPARISON WITH EXPERIMENT OF COMPACTION OF A MULTI-STEPPED PART P.Mosbah et al. (University of Wales, Swansea, UK.) J. Jpn Sot. Powder I Powder Metall., Vol 46, No 7, 1999, 696-704. (In English.) It is reported that compaction of a multi-level axi-symmetric part had been simulated using data for Fe powder and a modified Cam-Clay model. Details of constitutive relationships are discussed. Phenomena during compaction and ejection are reviewed with consideration of defects. Comparison is made with experiment. EFFECT OF PUNCH SHAPE ON DYNAMICALLY COMPACTED POWDERS N.Sukegawa et aZ. (Chiba Inst. of Technology, Narashino, Japan.) J. Jpn Sot. Powder/Powder Metall., Vol 46, No 7,1999,735-741. (In Japanese.) Forming of films of pure 37 pm Al powder by an ambient temperature dynamic technique was investigated with respect to effects of process parameters on structure and properties. The method used electro-magnetic means. Punches with a straight shape and with abrupt changes in section were used. Densities of 90 to 97% were attained. The punch with the change of section gave materials with the higher bend strength. FULL DENSITY NET SHAPE CONSOLIDATION USING DYNAMIC MAGNETIC PULSED PRESSURES B.Chelluri, J.P.Barber. J. of Metals, (JOM), Vol51, No 7,1999,36-37. Advantages of pressing to full density and net shape are identified. It is noted that conventional pressing only attains low green densities. It is reported that dynamic magnetic pulsed pressing can attain full density without lubricants or binders. HOT EXPLOSIVE COMPACTION OF MOLYBDENUM-TITANIUM POWDERS L.J.Kecskes. (US Army Research Laboratory, MD, USA.) Metal. /Mater. Tram A, Vol30A, No 9,1999,2483-2489. It is reported that a hot explosive compaction technique had been applied to Mo-Ti powder. The Mo-Ti powder is enclosed in a highly exothermic Ti-C
mixture that heats the powder, which is then compacted to full density by an explosive charge. The compacted alloy was characterized for microstructure.
Fundamentals BREAKAGE INDUCED BY A GRINDING BALL DROPPED ONTO A RANDOMLY PACRED PARTICLE BED A.V.Potapov, C.S.Campbell. (University of S.California, Los Angeles, USA.) Powder Tech., Vol107, No 1/2,2000,108-117. Computer simulations of particle breakage caused by impact of a single ball falling on to a particle bed, for a range of conditions, are described. The relevance is to ball milling. Particles in the bed are either fractured or scattered by the impacts. The results showed the role of friction in which much energy is dissipated. Increase in friction increases energy loss but friction holds the particle bed together, increasing breakage. Energy for fracture of particles is considered to come from the kinetic energy of scattered fragments. DYNAMIC PACKING
SIMULATION OF RANDOM OF SPHERICAL PARTICLES
S.J.Guo et al. (University of Science and Technology, Beijing, China.) Powder Tech., Vol 107, No l/2,2000,123-130. Two-dimensional computer simulations of packing of mono-sized spherical particles are described. Forces acting on particles are identified as gravity, contact force, friction and van der Waals forces. Packing densities were determined as functions of friction. For small particles, van der Waals forces are considered since clustering can reduce packing density. A distinct element technique was used and the results are considered to validate the method. EFFECT OF PARTICLE SHAPE ON ANGLE OF INTERNAL FRICTION BY TRIAXIAL COMPRESSION TEST K.Shinohara et al. (Hokkaido University, Sapporo, Japan.) Powder Tech., Vol107, No l/2,2000,131-136. Effects of particle shape on friction of fine particles were investigated by triaxial compression of angular stainless steel powders, which had been processed towards sphericity. The angle of internal friction increased with increasing angularity of the particles.
Aluminium EFFECTS OF COOLING RATE ON STRUCTURE AND STABILITY OF RAPIDLY SOLIDIFIED ALUMINIUM ALLOY AKalkani, SAngi. (Middle East Technical University, Ankara, Turkey.) Powder Metall., Vol42, No 4,1999,359-365. An investigation of structure and thermal stability of rapidly solidified Al46.8 to 7.8)wt%Fe-(1 to 3)%V-(1.6 to 2.2)%Si alloys, made by atomization and melt spinning, is described. Powders and ribbons both had a cellular structure containing various dispersoids, including i phase particles. Proportions of phases present depended on section thickness and cooling rate. More of the i phase was found in ribbons and coarse powders. Heat treatment at 300 to 500 “C caused growth of dispersoids by 2-3 times. DAMPING PROPERTIES OF POWDER FORGED ALUMINIUM-SILICON ALLOYS K.Kondoh et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7,1999,715-721. (In Japanese.) Effects of %Si and Si particle size on damping properties of powder forged AlSi alloys were investigated. It is shown that the damping capacity, 5, depends on the mean diameter of Si crystallites and is highest for fine Si particles. EFFECTS OF BINDER ON CHARACTERISTICS OF WET GRANULATED ALLMINTUM ALLOY POWDER K.Kondoh, Y.Takeda. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7,1999,772-779. (In Japanese.) It is reported that Al-lBwt%Si-B%Nil%Mn-0.2%Fe alloy powders had been wet granulated in a fluidized bed with a PVA binder. The granulated powder is said to be 75 to 100 ,um in size and spherical in shape with good flow properties and dimensional tolerances compared with the raw powder. COMPACTION GRANULATED POWDER K.Kondoh Industries
BEHAS’IOUR ALUMINIUM
OF WET ALLOY
et al. (Sumitomo Electric Ltd, Itami, Japan.) J. Jpn
MPR December
2000 37
mixture that heats the powder, which is then compacted to full density by an explosive charge. The compacted alloy was characterized for microstructure.
Fundamentals BREAKAGE INDUCED BY A GRINDING BALL DROPPED ONTO A RANDOMLY PACRED PARTICLE BED A.V.Potapov, C.S.Campbell. (University of S.California, Los Angeles, USA.) Powder Tech., Vol107, No 1/2,2000,108-117. Computer simulations of particle breakage caused by impact of a single ball falling on to a particle bed, for a range of conditions, are described. The relevance is to ball milling. Particles in the bed are either fractured or scattered by the impacts. The results showed the role of friction in which much energy is dissipated. Increase in friction increases energy loss but friction holds the particle bed together, increasing breakage. Energy for fracture of particles is considered to come from the kinetic energy of scattered fragments. DYNAMIC PACKING
SIMULATION OF RANDOM OF SPHERICAL PARTICLES
S.J.Guo et al. (University of Science and Technology, Beijing, China.) Powder Tech., Vol 107, No l/2,2000,123-130. Two-dimensional computer simulations of packing of mono-sized spherical particles are described. Forces acting on particles are identified as gravity, contact force, friction and van der Waals forces. Packing densities were determined as functions of friction. For small particles, van der Waals forces are considered since clustering can reduce packing density. A distinct element technique was used and the results are considered to validate the method. EFFECT OF PARTICLE SHAPE ON ANGLE OF INTERNAL FRICTION BY TRIAXIAL COMPRESSION TEST K.Shinohara et al. (Hokkaido University, Sapporo, Japan.) Powder Tech., Vol107, No l/2,2000,131-136. Effects of particle shape on friction of fine particles were investigated by triaxial compression of angular stainless steel powders, which had been processed towards sphericity. The angle of internal friction increased with increasing angularity of the particles.
Aluminium EFFECTS OF COOLING RATE ON STRUCTURE AND STABILITY OF RAPIDLY SOLIDIFIED ALUMINIUM ALLOY AKalkani, SAngi. (Middle East Technical University, Ankara, Turkey.) Powder Metall., Vol42, No 4,1999,359-365. An investigation of structure and thermal stability of rapidly solidified Al46.8 to 7.8)wt%Fe-(1 to 3)%V-(1.6 to 2.2)%Si alloys, made by atomization and melt spinning, is described. Powders and ribbons both had a cellular structure containing various dispersoids, including i phase particles. Proportions of phases present depended on section thickness and cooling rate. More of the i phase was found in ribbons and coarse powders. Heat treatment at 300 to 500 “C caused growth of dispersoids by 2-3 times. DAMPING PROPERTIES OF POWDER FORGED ALUMINIUM-SILICON ALLOYS K.Kondoh et al. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7,1999,715-721. (In Japanese.) Effects of %Si and Si particle size on damping properties of powder forged AlSi alloys were investigated. It is shown that the damping capacity, 5, depends on the mean diameter of Si crystallites and is highest for fine Si particles. EFFECTS OF BINDER ON CHARACTERISTICS OF WET GRANULATED ALLMINTUM ALLOY POWDER K.Kondoh, Y.Takeda. (Sumitomo Electric Industries Ltd, Itami, Japan.) J. Jpn Sot. PowderlPowder Metall., Vol 46, No 7,1999,772-779. (In Japanese.) It is reported that Al-lBwt%Si-B%Nil%Mn-0.2%Fe alloy powders had been wet granulated in a fluidized bed with a PVA binder. The granulated powder is said to be 75 to 100 ,um in size and spherical in shape with good flow properties and dimensional tolerances compared with the raw powder. COMPACTION GRANULATED POWDER K.Kondoh Industries
BEHAS’IOUR ALUMINIUM
OF WET ALLOY
et al. (Sumitomo Electric Ltd, Itami, Japan.) J. Jpn
MPR December
2000 37