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Flexible control of high speed mechanical alloying for bulk amorphous materials
DENSIFICATION AND ALLOY FORMATION DURING SINTERING OF HETEROGENEOUS CONSTITUENTS B. Kieback et al (Technical University of Dresden, dresden, Germany). Diffusion and the formation of new phases during sintering of heterogeneous systems were discussed. The paper analysed the interaction of shrinkage and homogenization in miscible systems Ni-Co and Ni-Cu and reasons for swelling during reactive sintering of Ti-Al. CHEMICAL EQUILIBRIA IN TITANIUMBORON NITRIDE J. Benko (University of Technology, Cracow, Poland). A calculation of chemical equilibria in ‘fi-BN at 27 to 2527°C and pressures of l.l~lO-~ to lo7 for two Ti-BN molar ratios, 1:l and 1:2, was presented. Formation of TiBz and TiN by reaction between Ni and BN were found to be strongly influenced by temperature and pressure. Good agreement between prediction and experiment was reported. MONITORING OF LIQUID PHASE DURING SINTERING OF SAMARIUMCOBALT C. Barthet et al (URA du CRNS, ENSEEG, St. Martin d’Heres, France). A study of sintering of Sm-20.5at% Co was described. Phases detected were SmCoa and SmzCoir. Densification was monitored by dilatometry and porosity. It was shown that there are stages of liquid phase sintering and of phase formation in the solid state. The shrinkage depended on the amount of liquid present and its lifetime. REACTIVE SINTERING OF A CERMET CONTAINING NICKEL CHROMIUM MOLYBDENUM AND BORON M. Komai et al (Toyo Kohan Co Ltd, Kudamatsu, Japan). Sintering of a cermet was investigated for Cr-58.&vt%Mo-25.4%Ni-6%B, made from a mixture of Ni, MO, Cr and MOB powders. The cermet had a Ni matrix with a line dispersion of (Mo,Cr,Ni)BBz. The mechanism included solid phase, liquid phase and reactive sintering. A transitional orthorhombic phase was formed which transfromed to a tetragonal phase. A eutectic was formed between Ni and the ternary boride. Structures were described. SUPERSOLIDUS SINTERING OF HIGH SPEED STEELS - COMPUTER AIDED DESIGN OF ALLOYS C.S. Wright et al (University of Bradford, Bradford, UK).
38
MPR July/August
1995
Phase diagrams, calculated from thermodynamic data, were used to suggest high speed steels with compositions suitable for vacuum sintering. MO base alloys with sintering windows of 20 to 3O”C, compared with 5 to 10°C for current HSS grades, and which sinter to full density at temperatures lower by 40 to 150°C were identified.
powders containing non-equilibrium phases, had been developed. Data logging proceedures were used to enable control of the process. Forced cooling was employed to maintain low temperatures.
Reactive synthesis
M. Abdellaoui, E. Galfet (Inst. Polytechnique de Sevenans, Belfort, France). Studies of MA, in a planetary ball mill, of Ni-Zr powders were described. It was shown that neither the impact frequency nor energy, taken separately, determine the characteristics of the product. Conditions for amorphization or formation of crystaine phases were outlined.
STRENGTH SINTERING TEMPERATURE AND REACTION TEMPERATURE BETWEEN ALUMINIUM AND IRON M.M. Rebbeck (Bradford University, Bradford, UK). It was pointed out the the sintering of Al alloys with Fe requires careful control of conditions due to the reaction between Al and Fe forming FeA13.Differential thermal analysis was used to study the formation of FeAla under a range of consolidation conditions. Activation energies were estimated and possible interpretations were suggested, namely, effect of thermal conductivity at low pressures, diffusion through oxide film at intermediate presssures and diffusion and direct metal interaction at high pressures. FORMATION OF MECHANICALLY ALLOYED IRON SOLID SOLUTIONS WITH COPPER OR COBALT J.F. Dinhut et al (University of Poitiers, Poitiers, France). Mechanical alloying phenomena in FeCo, with high solid solubility, and Fe-Cu, with low solubility, were compared by use of X-ray diffraction and electron microscopy. Mossbauer spectroscopy allowed deduction of the local environment of Fe atoms. EFFECT OF COMPACTION DENSITY ON COMBUSTION SYNTHESIS OF TITANIUM ALUMINIDE Y.D. Hahn, I.H. Song. (Inst. for Machinery and Metals, Kyung Nam, Korea). The effects of green density on synthesis of TiAl by thermal explosion was investigated. Initiation of synthesis was not affected by green density. The peak temperature attained increased with increased density. Both TiAl and TiAls were formed. Swelling of the compacts was observed and this increased with density. FLEXIBLE CONTROL OF HIGH SPEED MECHANICAL ALLOYING FOR BULK AMORPHOUS MATERIALS T. Aizawa et al (University of Tokyo, Tokyo, Japan j . It was reported that a mechanometallurgical processing technique, which was described, for mechanical alloying for the production of amorphous powders and
KINEMATIC APPROACH TO PHYSICS OF MECHANICAL ALLOYING IN PLANETARY BALL AND ROD MILLS
MICROSTRUCTURAL CHANGES IN ELEMENTAL POWDERS DURING MECHANICAL ALLOYING A.P. Miodownik et al (University of Surrey, Guildford, Surrey, UK). A study of MA of elemental powders corresponding to Al alloy 7010 was described. Effects were monitored by microstructure, layer thickness and microhardness. It was shown that there was a fine dispersion of alumina particles in the matrix and that Mg, Zn and Cu were in elemental form. The matrix nature could not be determined by X-ray diffraction but the dislocation density indicated a high level of residual stress. DETERMINATION OF REACTION KINETICS DURING MECHANICAL ALLOYING G.B. Schaffer, J.S. Forrester (University of Queensland, Australia). The kinetics of double displacement reactions, induced by MA, was investigated by thermal analysis. The effect of a solid reducing agent on Cu oxide was evaluated. Activation energy, which decreases with increase in milling time, reached a steady value before the onset of a combustion reaction. This was considered to be rate controlling. ENHANCEMENT OF METAL DISPERSION BY BALL MILLING WITH ALUMINA A. van Neste et al (Lava1 University, Quebec, Canada). The use of MA to produce nanocrystalline Ni-Ru alloy powders, with regard to composition and application as catalysts, was discussed. The specific surface was shown to normally too small for the powders to be effective catalysts. The effect of adding alumina on adsorption and desorption of H was determined. REACTIVE MECHANICAL ALLOYS E. Ivanov (TOSCH Ohio, USA).
SMD, Grove
City,
38
MPR July/August
1995
Phase diagrams, calculated from thermodynamic data, were used to suggest high speed steels with compositions suitable for vacuum sintering. MO base alloys with sintering windows of 20 to 3O”C, compared with 5 to 10°C for current HSS grades, and which sinter to full density at temperatures lower by 40 to 150°C were identified.
powders containing non-equilibrium phases, had been developed. Data logging proceedures were used to enable control of the process. Forced cooling was employed to maintain low temperatures.
Reactive synthesis
M. Abdellaoui, E. Galfet (Inst. Polytechnique de Sevenans, Belfort, France). Studies of MA, in a planetary ball mill, of Ni-Zr powders were described. It was shown that neither the impact frequency nor energy, taken separately, determine the characteristics of the product. Conditions for amorphization or formation of crystaine phases were outlined.
STRENGTH SINTERING TEMPERATURE AND REACTION TEMPERATURE BETWEEN ALUMINIUM AND IRON M.M. Rebbeck (Bradford University, Bradford, UK). It was pointed out the the sintering of Al alloys with Fe requires careful control of conditions due to the reaction between Al and Fe forming FeA13.Differential thermal analysis was used to study the formation of FeAla under a range of consolidation conditions. Activation energies were estimated and possible interpretations were suggested, namely, effect of thermal conductivity at low pressures, diffusion through oxide film at intermediate presssures and diffusion and direct metal interaction at high pressures. FORMATION OF MECHANICALLY ALLOYED IRON SOLID SOLUTIONS WITH COPPER OR COBALT J.F. Dinhut et al (University of Poitiers, Poitiers, France). Mechanical alloying phenomena in FeCo, with high solid solubility, and Fe-Cu, with low solubility, were compared by use of X-ray diffraction and electron microscopy. Mossbauer spectroscopy allowed deduction of the local environment of Fe atoms. EFFECT OF COMPACTION DENSITY ON COMBUSTION SYNTHESIS OF TITANIUM ALUMINIDE Y.D. Hahn, I.H. Song. (Inst. for Machinery and Metals, Kyung Nam, Korea). The effects of green density on synthesis of TiAl by thermal explosion was investigated. Initiation of synthesis was not affected by green density. The peak temperature attained increased with increased density. Both TiAl and TiAls were formed. Swelling of the compacts was observed and this increased with density. FLEXIBLE CONTROL OF HIGH SPEED MECHANICAL ALLOYING FOR BULK AMORPHOUS MATERIALS T. Aizawa et al (University of Tokyo, Tokyo, Japan j . It was reported that a mechanometallurgical processing technique, which was described, for mechanical alloying for the production of amorphous powders and
KINEMATIC APPROACH TO PHYSICS OF MECHANICAL ALLOYING IN PLANETARY BALL AND ROD MILLS
MICROSTRUCTURAL CHANGES IN ELEMENTAL POWDERS DURING MECHANICAL ALLOYING A.P. Miodownik et al (University of Surrey, Guildford, Surrey, UK). A study of MA of elemental powders corresponding to Al alloy 7010 was described. Effects were monitored by microstructure, layer thickness and microhardness. It was shown that there was a fine dispersion of alumina particles in the matrix and that Mg, Zn and Cu were in elemental form. The matrix nature could not be determined by X-ray diffraction but the dislocation density indicated a high level of residual stress. DETERMINATION OF REACTION KINETICS DURING MECHANICAL ALLOYING G.B. Schaffer, J.S. Forrester (University of Queensland, Australia). The kinetics of double displacement reactions, induced by MA, was investigated by thermal analysis. The effect of a solid reducing agent on Cu oxide was evaluated. Activation energy, which decreases with increase in milling time, reached a steady value before the onset of a combustion reaction. This was considered to be rate controlling. ENHANCEMENT OF METAL DISPERSION BY BALL MILLING WITH ALUMINA A. van Neste et al (Lava1 University, Quebec, Canada). The use of MA to produce nanocrystalline Ni-Ru alloy powders, with regard to composition and application as catalysts, was discussed. The specific surface was shown to normally too small for the powders to be effective catalysts. The effect of adding alumina on adsorption and desorption of H was determined. REACTIVE MECHANICAL ALLOYS E. Ivanov (TOSCH Ohio, USA).
SMD, Grove
City,