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Development of microstructure during late stage sintering of Ni powder compacts
ture Review EFFECT OF CRYOMECHANICAL TREATMENT ON SINTERING OF Cu POWDER COMPACTS Y I Boiko, et al, Poroskovaya Metallurgia, 1990, No 2, 18-23, in Russian. Dilatometric effects during sintering of Cu compacts, previously subjected to mechanical treatment at 77 K, are studied. It is shown that considerable strain hardening and a curved shape of particles affect kinetics, rate and dilatation in sintering compacts. Effects attributed to relaxation of redundant elastic energy. MECHANISM OF REACTION OF Ti-Ni POWDER COMPACT BY EXOTHERMIC REACTION Y Suzuki, et al, J Japan Soc. Powder and Powder Metallurgy, Vol 37, No 3, 1990, 433--438, in Japanese. The role of gases in the exothermic self-sintering of Ni-Ti is discussed. Evolution of H2 from Ni-Ti compacts heated in vacuo is reported. S p e c i m e n s were e x a m i n e d microscopically and heat of formation of NiTi measured.
EFFECT OF TIN ON SINTERING OF IRON POWDER COMPACTS S Tanabe, et al, J Japan Soc. Powder and Powder Metallurgy, Vol 37, No 3, 1990, 439-444, in Japanese. EPMA, XRD, dilatometry and microscopy were used to study the sintering of Fe powder compacts c o n t a i n i n g additions of tin. Expansion was observed in the range 633-773 K as molten tin penetrated the interstices between the iron particles. At higher temperatures intermetallic compounds of Sn and Fe formed and decomposed. Above 1223 K fin was found to be dissolved uniformly in the iron. OBSERVATION OF GRAIN SHAPE ACCOMMODATION DURING LIQUID PHASE SINTERING D-D Lee, et al, (Korean Inst of Advanced Science and Technology, Seoul, Korea), Scripta Metall. and Materia., Vol 24, 1990, 927-930.
MPR October 1990
Shape change during liquid phase sintering was studied. Samples containing (1) fine Mo powder and a large concentrationof Ni powder were sintered fully and (2) Mo powder with a small amount of Ni were. partially sintered to retain porosity. Pairs of the two types were sintered together and the change in structure observed as Ni was drawn from one to the other under capillary action from the Ni-rich sample. HOT VEHICLE COMPACTION OF ATOMIZED STAINLESS STEEL POWDER R Watanabe, et al, (Tohoku University, Sendai, Japan), Materials Trans Japan Inst. of Metals, Vol 31, No 2, 1990 152-157. Stainless steel powder, encapsulated in glass, was compacted in a press using alumina granules as a pressure transmitting medium (VIM). Conditions for full densification were established. Microstructural changes were studied. It was found that a fine microstructure formed during recrystallization. Kinetic analysis showed that plastic flow is the dominant mechanism in densification. DEVELOPMENT OF MICROSTRUCTURE DURING LATE STAGE SINTERING OF Ni POWDER COMPACTS R T DeHoff, L Gouquan, (University of Florida, Gainsville, USA), Acta Metall. Sinica B (English Edn), Vol 3, No 2, 1990, 115-124. A stereological method was applied to the study of evolution of mierostructure in the late stages of sintering of Ni powder compacts. The effects of compacting pressure and loose sintering are discussed. EFFECT OF HIGH RATE LOADING ON COMPACTION O V Roman, et al, Poroskovaya Metallurgia, 1989, No 11, 14-19, (in Russian). A physical model of powder behaviour under high energy rate compaction is presented. The t r a n s i t i o n from q u a s i - i s o s t a t i c to non-equilibrium conditions is discussed. Consideration is given to the correlation between compaction mechanisms and production practice using different materials.
PRECISION OF PM PARTS n A SYSTEM PROPERTY F Voilertsen, M Geiger, (Friedrich-Alexander Universit~it, Erlangen-Numberg, Germany), Powder Metallurgy Int., Vol 22, No 3, 1990, 15-20. Factors contributing to dimensional accuracy in PM parts, variation in composition, compacting force, sintering time and temperature are considered. It is shown that green density and amount of liquid phase mainly determine dimensional accuracy. Shape accuracy is mainly determined by friction during compacting and sintering and slumping. Dimensional tolerances are said to be easier to meet than shape accuracy. A method is given to calculate dimensional accuracy from experimental data in order to establish the critical parameters of a given system.
ANALYTICAL STUDY OF POWDER ROLLING A V S t e p a n e n k o , et al, Poroskovaya Metallurgia, 1990, No 2, 13-17, in Russian. An analytical representation of statically admissible fields of stresses in zones of delay and advance, as well as boundaries of the deformation centre under rolling of metallic powders is obtained. The solution of the initial stage of the problem is based on application of the variable, which characterizes the stress intensity variation at the deformation site.
SURFACE MORPHOLOGY OF ULTRADISPERSED Fe POWDERS V D P a r k h o m e n k o , et al, Poroskovaya Metallurgia, 1990, No 2, 86-89, in Russian. Mossbauer spectroscopy has been used to study the composition of ultra dispersed Fe powders produced by decomposition of Fe-pentacarbonyl. Ferro- and para-magnetic modifications of the iron are observed. The iron powder particles are found to be coated with Fe203.
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EFFECT OF TIN ON SINTERING OF IRON POWDER COMPACTS S Tanabe, et al, J Japan Soc. Powder and Powder Metallurgy, Vol 37, No 3, 1990, 439-444, in Japanese. EPMA, XRD, dilatometry and microscopy were used to study the sintering of Fe powder compacts c o n t a i n i n g additions of tin. Expansion was observed in the range 633-773 K as molten tin penetrated the interstices between the iron particles. At higher temperatures intermetallic compounds of Sn and Fe formed and decomposed. Above 1223 K fin was found to be dissolved uniformly in the iron. OBSERVATION OF GRAIN SHAPE ACCOMMODATION DURING LIQUID PHASE SINTERING D-D Lee, et al, (Korean Inst of Advanced Science and Technology, Seoul, Korea), Scripta Metall. and Materia., Vol 24, 1990, 927-930.
MPR October 1990
Shape change during liquid phase sintering was studied. Samples containing (1) fine Mo powder and a large concentrationof Ni powder were sintered fully and (2) Mo powder with a small amount of Ni were. partially sintered to retain porosity. Pairs of the two types were sintered together and the change in structure observed as Ni was drawn from one to the other under capillary action from the Ni-rich sample. HOT VEHICLE COMPACTION OF ATOMIZED STAINLESS STEEL POWDER R Watanabe, et al, (Tohoku University, Sendai, Japan), Materials Trans Japan Inst. of Metals, Vol 31, No 2, 1990 152-157. Stainless steel powder, encapsulated in glass, was compacted in a press using alumina granules as a pressure transmitting medium (VIM). Conditions for full densification were established. Microstructural changes were studied. It was found that a fine microstructure formed during recrystallization. Kinetic analysis showed that plastic flow is the dominant mechanism in densification. DEVELOPMENT OF MICROSTRUCTURE DURING LATE STAGE SINTERING OF Ni POWDER COMPACTS R T DeHoff, L Gouquan, (University of Florida, Gainsville, USA), Acta Metall. Sinica B (English Edn), Vol 3, No 2, 1990, 115-124. A stereological method was applied to the study of evolution of mierostructure in the late stages of sintering of Ni powder compacts. The effects of compacting pressure and loose sintering are discussed. EFFECT OF HIGH RATE LOADING ON COMPACTION O V Roman, et al, Poroskovaya Metallurgia, 1989, No 11, 14-19, (in Russian). A physical model of powder behaviour under high energy rate compaction is presented. The t r a n s i t i o n from q u a s i - i s o s t a t i c to non-equilibrium conditions is discussed. Consideration is given to the correlation between compaction mechanisms and production practice using different materials.
PRECISION OF PM PARTS n A SYSTEM PROPERTY F Voilertsen, M Geiger, (Friedrich-Alexander Universit~it, Erlangen-Numberg, Germany), Powder Metallurgy Int., Vol 22, No 3, 1990, 15-20. Factors contributing to dimensional accuracy in PM parts, variation in composition, compacting force, sintering time and temperature are considered. It is shown that green density and amount of liquid phase mainly determine dimensional accuracy. Shape accuracy is mainly determined by friction during compacting and sintering and slumping. Dimensional tolerances are said to be easier to meet than shape accuracy. A method is given to calculate dimensional accuracy from experimental data in order to establish the critical parameters of a given system.
ANALYTICAL STUDY OF POWDER ROLLING A V S t e p a n e n k o , et al, Poroskovaya Metallurgia, 1990, No 2, 13-17, in Russian. An analytical representation of statically admissible fields of stresses in zones of delay and advance, as well as boundaries of the deformation centre under rolling of metallic powders is obtained. The solution of the initial stage of the problem is based on application of the variable, which characterizes the stress intensity variation at the deformation site.
SURFACE MORPHOLOGY OF ULTRADISPERSED Fe POWDERS V D P a r k h o m e n k o , et al, Poroskovaya Metallurgia, 1990, No 2, 86-89, in Russian. Mossbauer spectroscopy has been used to study the composition of ultra dispersed Fe powders produced by decomposition of Fe-pentacarbonyl. Ferro- and para-magnetic modifications of the iron are observed. The iron powder particles are found to be coated with Fe203.
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