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Supersolidus sintering of microcrystalline particles
MANUFACTURE OF IRON ALUMINIDE SHEET BY PM TECHNOLOGY M.Hajaligol et al. (P.Morris (USA), Virginia, USA.) Production of thin Fe aluminide sheets by roll compaction of powders or by tape casting was reported. In roll compaction a binder was used and after debindinn the sheets were sintered at high temperature to less than full density. Cold rolling and heat treatment were used to increase the density. Mechanical properties were described. STUDIES OF DIE WALL LUBRICATION S.Rastogi et al. (Sundram Fasteners Ltd, Hosur, India.) Die wall lubrication was discussed and it was noted that this can attain densities usually requiring a doublepress-double-sinter technique. Production trials were described and results presented. The technique was shown to be cost effective. DENSIFICATION OF PARTICLES UNDER ISOSTATIC COMPACTION A.Eksi, S.Saritas. (Gazi University, Turkey. 1 A study of cold isostatic pressing of Fe, Al and Also, powders, in flexible containers, was described. Pressing was at 100 to 150 MPa and densification was determined. Optical and electron microscopy were used to study deformation of the compressed particles. POWDER FORGING ON FULLY AUTOMATIC MACHINES K.Fey. (Lasco Umformtechnik GmbH, Coburg, Germany.) Use of powder forging for production of automotive parts was noted. Process details for an automatic press line for powder forging were presented. Topics considered included heating, tool positioning, handling and monitoring, and control systems.
Compaction modelling CONSTITUTIVE BEHAVIOUR OF POWDER ASSEMBLY SIMULATION H.Kitahara et al. (Kyoto University, Kyoto, Japan.) Investigations of modelling and simulation of powder compaction in three dimensions were described. Differences between simulated and experimental results were noted in terms of pressure/density relationships. A non-spherical particle model was developed using parts of spherical surfaces. Changes in curvature expressed a variety of shapes, which allowed study of effects of particle rotation on the packing state. The
38 MPR July/August
1999
dependence of interparticle friction on pressure/density relationships of Cu powder was considered in closed die compaction. This was shown to give improved agreement between experiment and theory STUDY OF PART PRESSING WITH USE OF NUMERICAL SIMULATIONS M.A.Haggelblad et al. (Lulea University ofTechnology, Lulea, Sweden.) Behaviour of metal powder, during compaction, was discussed with regard to process kinematics, powder characteristics and friction effects. The need for accurate material models was emphasized. Modelling was shown to depend on results of triaxial and friction tests. Part pressing, under various kinematic conditions, was carried out. A set of process and model parameters was established for the numerical simulations. The analyses were used to evaluate the effects of kinematic conditions on results of compaction tests. MODELLING OF MULTI-LEVEL PARTS DURING COMPACTION AND EJECTION SAshok, R.K.Kumar. (Indian Inst. of Technology, Madras, India.) Occurrence of variations in density of complex shaped PM parts, cracking during loading and ejection, and the value of finite element analysis in design were noted. A finite element package was developed which takes into account deformation effects with voids, friction between die and part, and elastic effects during unloading and ejection. The package was applied to an automotive synchronizer hub.
Sin tering SINTERING KINETICS, PHASE TRANSFORMATIONS AND PROPERTIES OF HIGH SPEED STEEL I.Whitaker et al. (Federal Mogul Sintered Products, Coventry, UK.) It was reported that a process route, involving alloy composition and all process variables, had been developed for mass production of high speed steel parts, at 99% density, for high temperature tribological applications. Dilatometry studies showed a sintering window of 30°C in the range 1140 to 1180°C. Sintering mechanisms were shown to depend on heating rate, being diffusion controlled at low rates and liquid phase controlled at high rates. Studies of cooling rate effects allowed establishment of a continuous cooling transformation diagram for optimization of heat treatment conditions, structure and mechanical properties.
PRESSURELESS NET SHAPE MANUFACTURE OF PM PARTS L.Nyborg et al. (Chalmers University of Technology, Goteborg, Sweden.) Studies of production of Fe-C-P and Fe-C-B parts were described. Effects of P and B on embrittlement, densification, structure and properties were described. A pressureless forming technique, coupled with liquid phase sintering, using melt forming agglomerates and coarse Fe powder, was described. The objective was to facilitate the use of coarse powders to make parts that could not be
made
by
die
pressing
or
Optimization of powder and parameters was discussed.
MIM. process
SIMULATION OF 2-DIMENSIONAL MICROSTRUCTURES DURING LIQUID PHASE SINTERING V.V.Kartuzov, I.V.Krassikov. (Inst. for Problems of Materials Science, Kiev, Ukraine. ) It was noted that the modelling of structural evolution can be done by modelling diffusional field and solution/precipitation reactions in liquid/ solid systems. 2D modelling of structures during liquid phase sintering (LPS) was described. The computed generated microstructures could be used to study the effects of elemental mechanisms during sintering, including grain growth and liquid/solid boundary migration and gravity effects. SUPERSOLIDUS SINTERING OF MICROCRYSTALLINE PARTICLES MSerov et al. (K. Tsiolkovsky Aviation Technology Inst., Moscow, Russia.) Use of powders made by melt spraying was discussed with reference to morphology and difficulties in attaining high density. It was shown that the latter can be overcome by use of supersolidus LPS. Experiments using spherical sprayed powders and acicular powders made by melt extraction were described. Sintering kinetics and structural evolution were investigated. Mechanisms of grain growth and means of controlling this were described. SOLID PHASE SINTERING OF TUNGSTEN BASE ALLOY F.Nardou et al. (University of Limoges, Limoges, France.) Liquid phase sintering of W alloys was discussed with regard to structural evolution and densification. Solid state sintering, without formation of any liquid phase, of a W-Fe-Ni-Co alloy was investigated. X-ray diffraction, Mossbauer and Exafs spectroscopic techniques were used to gain information short range order as temperature
Compaction modelling CONSTITUTIVE BEHAVIOUR OF POWDER ASSEMBLY SIMULATION H.Kitahara et al. (Kyoto University, Kyoto, Japan.) Investigations of modelling and simulation of powder compaction in three dimensions were described. Differences between simulated and experimental results were noted in terms of pressure/density relationships. A non-spherical particle model was developed using parts of spherical surfaces. Changes in curvature expressed a variety of shapes, which allowed study of effects of particle rotation on the packing state. The
38 MPR July/August
1999
dependence of interparticle friction on pressure/density relationships of Cu powder was considered in closed die compaction. This was shown to give improved agreement between experiment and theory STUDY OF PART PRESSING WITH USE OF NUMERICAL SIMULATIONS M.A.Haggelblad et al. (Lulea University ofTechnology, Lulea, Sweden.) Behaviour of metal powder, during compaction, was discussed with regard to process kinematics, powder characteristics and friction effects. The need for accurate material models was emphasized. Modelling was shown to depend on results of triaxial and friction tests. Part pressing, under various kinematic conditions, was carried out. A set of process and model parameters was established for the numerical simulations. The analyses were used to evaluate the effects of kinematic conditions on results of compaction tests. MODELLING OF MULTI-LEVEL PARTS DURING COMPACTION AND EJECTION SAshok, R.K.Kumar. (Indian Inst. of Technology, Madras, India.) Occurrence of variations in density of complex shaped PM parts, cracking during loading and ejection, and the value of finite element analysis in design were noted. A finite element package was developed which takes into account deformation effects with voids, friction between die and part, and elastic effects during unloading and ejection. The package was applied to an automotive synchronizer hub.
Sin tering SINTERING KINETICS, PHASE TRANSFORMATIONS AND PROPERTIES OF HIGH SPEED STEEL I.Whitaker et al. (Federal Mogul Sintered Products, Coventry, UK.) It was reported that a process route, involving alloy composition and all process variables, had been developed for mass production of high speed steel parts, at 99% density, for high temperature tribological applications. Dilatometry studies showed a sintering window of 30°C in the range 1140 to 1180°C. Sintering mechanisms were shown to depend on heating rate, being diffusion controlled at low rates and liquid phase controlled at high rates. Studies of cooling rate effects allowed establishment of a continuous cooling transformation diagram for optimization of heat treatment conditions, structure and mechanical properties.
PRESSURELESS NET SHAPE MANUFACTURE OF PM PARTS L.Nyborg et al. (Chalmers University of Technology, Goteborg, Sweden.) Studies of production of Fe-C-P and Fe-C-B parts were described. Effects of P and B on embrittlement, densification, structure and properties were described. A pressureless forming technique, coupled with liquid phase sintering, using melt forming agglomerates and coarse Fe powder, was described. The objective was to facilitate the use of coarse powders to make parts that could not be
made
by
die
pressing
or
Optimization of powder and parameters was discussed.
MIM. process
SIMULATION OF 2-DIMENSIONAL MICROSTRUCTURES DURING LIQUID PHASE SINTERING V.V.Kartuzov, I.V.Krassikov. (Inst. for Problems of Materials Science, Kiev, Ukraine. ) It was noted that the modelling of structural evolution can be done by modelling diffusional field and solution/precipitation reactions in liquid/ solid systems. 2D modelling of structures during liquid phase sintering (LPS) was described. The computed generated microstructures could be used to study the effects of elemental mechanisms during sintering, including grain growth and liquid/solid boundary migration and gravity effects. SUPERSOLIDUS SINTERING OF MICROCRYSTALLINE PARTICLES MSerov et al. (K. Tsiolkovsky Aviation Technology Inst., Moscow, Russia.) Use of powders made by melt spraying was discussed with reference to morphology and difficulties in attaining high density. It was shown that the latter can be overcome by use of supersolidus LPS. Experiments using spherical sprayed powders and acicular powders made by melt extraction were described. Sintering kinetics and structural evolution were investigated. Mechanisms of grain growth and means of controlling this were described. SOLID PHASE SINTERING OF TUNGSTEN BASE ALLOY F.Nardou et al. (University of Limoges, Limoges, France.) Liquid phase sintering of W alloys was discussed with regard to structural evolution and densification. Solid state sintering, without formation of any liquid phase, of a W-Fe-Ni-Co alloy was investigated. X-ray diffraction, Mossbauer and Exafs spectroscopic techniques were used to gain information short range order as temperature