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Hot isostatic pressing of boron powder
Density distribution is improved in comparison with compaction at ambient temperatures. Volume change on ejection from the die was evaluated. Reduced permeability to furnace gases has the effect that gases may not penetrate to the core of a warm compacted part and there may be under-sintering. The concept of reduction depth was introduced. It was considered that powders for warm compaction should have low inclusion contents in order to maximize fatigue properties. Process conditions, tools and differences with ambient temperature compaction were reviewed. The need for good design calculation was emphasized. Use of electro-dispersive machining in die making was discussed. HOT ISOSTATIC PRESSING OF BORON POWDER PPerriat et al. (University of Burgundy, France.) Hot isostatic pressing of B powder, in a Ti container, was discussed. Conditions were said to be 150 MPa pressure and temperature above 1300°C for several hours to attain full density. Experimental and modelling studies of the behaviour of B powders were described. The object was to optimize HIP processing of B powders. Both HIP and hot pressing experiments were carried out at 1300 to 1550°C. Density and deformation evolution could be predicted and were compared with experimental results. COST EFFECTIVE HOT ISOSTATIC PRESSING OF STEEL POWDERS J.Westerlund et al. (ABB Pressure Systems, Sweden.) Hot isostatic pressing of powders, in containers, was discussed with reference to use in a wide range of applications and the properties attained. It was noted that the usual method of HIP employed was a hot load-hot unload procedure. It was reported that a cold load-hot unload technique had been used. This was said to reduce costs and scrap rate and to increase production rate and quality of steel parts produced. Application of the technique was discussed. IMPROVEMENT IN DISC ALLOY QUALITY USING POWDER METALLURGY AND HOT ISOSTATIC PRESSING V.A.Zinoviev et al. (All-Russia Inst. of Light Alloys, Russia.) It was reported that the use of high quality Al powders and HIP had allowed production of large discs, up to 0.9 m in diameter. Grain size did not exceed 80 pm. Mechanical properties were superior to those of cast/wrought alloys and were produced at lower costs.
44 MPR June 1999
Advanced particulate materials and processing NON-ISOTHERMAL SINTERING OF DIFFERENT BARIUM TITXNATE POWDERS O.O.Vasylkiv, A.V.Polotay. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Non-isothermal sintering of Ba titanate powders was investigated to determine effects of powder origin and particle size on sinterability. Nano-sized powders densified at 70 to 100°C lower temperatures than coarse, milled, powders. Structure and pore evolution was studied by electron microscopy. Objectives were to avoid discontinuous grain growth and to optimize processing to yield a fine and uniform grain size. PM ALLOYS MADE FROM RAPIDLY SOLIDIFIED MAGNESIUM-CERIUM BASE ALLOYS T.Miyazaki et al. (Nihon University, Japan.) Mg-Ce alloys powders, with and without additions of Zn and Ca, were rapidly solidified and consolidated by hot extrusion. Structures and mechanical properties were determined. Rapid solidification increased the solubility of Ce in Al by a factor of 10 to 5.6wt%Ce. Fine structures of Mg solid solution dendrites, with eutectic cells, were obtained in the powders. The extruded alloys had a fine and uniform dispersion of inter-metallic compounds. Tensile strengths of 550 and 350 MPa were obtained at ambient temperature and 200°C respectively. ROLLING OF METAL POWDERS VNazarenko et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Rolling of metal and alloy powders to a range of sizes and shapes was reviewed with regard to productivity, power consumption and the ability to make pore free products. Production of Ni and Ti foils was discussed in terms of structure and properties. DESIGN OF FACILITIES FOR PROCESSING OF HAZARDOUS PARTICULATES S.P.Abeln, S.Salisbury. (Los Alamos National Laboratory, USA.) Processing and application of Be was discussed with emphasis on health hazards arising from the toxicity of Be, particularly the need to minimize airborne particulates. Design characteristics of new Be processing facilities were described notably for protection of the workforce. Layout, systems to minimize aerosol exposure and spread, ventilation, extraction of particulates at source
and workplace lined.
cleanliness
were
out-
PRODUCTION OF UNIFORM SPHERICAL METAL POWDER AND EFFECT ON PART MAKING C.P.Brown. (Uniform Metal Technologies L.L.C., USA.) A new process for production of metal powder was described. A stream of molten metal is broken up by forced vibration into uniform spheres. Process parameters, particle size and size distribution were discussed. It was reported that a variance of 3% for mean particle size could be attained. Comparison was made between filters made from this powder and other powders, Effects of lot-to-lot variations on PM processes, including MIM and rapid prototyping were discussed. PM’98.The following Abstracts are of papers that were presented at the
Mechanical
alloying
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALUMINIUM-CHROMIUM-IRON ALLOYS K.K.Hwan, B.S.Chun. (Rasom, Taejon, Korea.) Al-Cr-Fe alloy powders were prepared by atomization and mechanical alloying to extend the solid solution range and to refine oxides and intermetallic constituents and consolidated by extrusion. The alloys were reported to have good thermal stability, good strength and creep properties making them suitable for high temperature service in aerospace parts. Structures and properties were described. SYNTHESIS AND CIIARACTERIZATION OF PM ALUMINIUM-LANTHANIDE ALLOYS T.Tianen et al. (Tampere University of Technology, Tampere, Finland.) Al-Gat%Mn-2%Ce and Al-3%Crl%Ti-l%Ce-l.S%Co alloys were mechanically alloyed from elemental powders and hot extruded. The objective of the study was to establish optimum process conditions and to investigate effects of heat treatment on structures. The mechanically alloyed powder consisted of a nanocrystalline solid solution with a mean grain size of 20 to 30 nm. In the asextruded materials the nanocrystalline grains were elongated in the extrusion direction. CeO, particles were detected and were shown to hinder growth of inter-metallic compound particles.
44 MPR June 1999
Advanced particulate materials and processing NON-ISOTHERMAL SINTERING OF DIFFERENT BARIUM TITXNATE POWDERS O.O.Vasylkiv, A.V.Polotay. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Non-isothermal sintering of Ba titanate powders was investigated to determine effects of powder origin and particle size on sinterability. Nano-sized powders densified at 70 to 100°C lower temperatures than coarse, milled, powders. Structure and pore evolution was studied by electron microscopy. Objectives were to avoid discontinuous grain growth and to optimize processing to yield a fine and uniform grain size. PM ALLOYS MADE FROM RAPIDLY SOLIDIFIED MAGNESIUM-CERIUM BASE ALLOYS T.Miyazaki et al. (Nihon University, Japan.) Mg-Ce alloys powders, with and without additions of Zn and Ca, were rapidly solidified and consolidated by hot extrusion. Structures and mechanical properties were determined. Rapid solidification increased the solubility of Ce in Al by a factor of 10 to 5.6wt%Ce. Fine structures of Mg solid solution dendrites, with eutectic cells, were obtained in the powders. The extruded alloys had a fine and uniform dispersion of inter-metallic compounds. Tensile strengths of 550 and 350 MPa were obtained at ambient temperature and 200°C respectively. ROLLING OF METAL POWDERS VNazarenko et al. (Inst. for Problems of Materials Science, Kiev, Ukraine.) Rolling of metal and alloy powders to a range of sizes and shapes was reviewed with regard to productivity, power consumption and the ability to make pore free products. Production of Ni and Ti foils was discussed in terms of structure and properties. DESIGN OF FACILITIES FOR PROCESSING OF HAZARDOUS PARTICULATES S.P.Abeln, S.Salisbury. (Los Alamos National Laboratory, USA.) Processing and application of Be was discussed with emphasis on health hazards arising from the toxicity of Be, particularly the need to minimize airborne particulates. Design characteristics of new Be processing facilities were described notably for protection of the workforce. Layout, systems to minimize aerosol exposure and spread, ventilation, extraction of particulates at source
and workplace lined.
cleanliness
were
out-
PRODUCTION OF UNIFORM SPHERICAL METAL POWDER AND EFFECT ON PART MAKING C.P.Brown. (Uniform Metal Technologies L.L.C., USA.) A new process for production of metal powder was described. A stream of molten metal is broken up by forced vibration into uniform spheres. Process parameters, particle size and size distribution were discussed. It was reported that a variance of 3% for mean particle size could be attained. Comparison was made between filters made from this powder and other powders, Effects of lot-to-lot variations on PM processes, including MIM and rapid prototyping were discussed. PM’98.The following Abstracts are of papers that were presented at the
Mechanical
alloying
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALUMINIUM-CHROMIUM-IRON ALLOYS K.K.Hwan, B.S.Chun. (Rasom, Taejon, Korea.) Al-Cr-Fe alloy powders were prepared by atomization and mechanical alloying to extend the solid solution range and to refine oxides and intermetallic constituents and consolidated by extrusion. The alloys were reported to have good thermal stability, good strength and creep properties making them suitable for high temperature service in aerospace parts. Structures and properties were described. SYNTHESIS AND CIIARACTERIZATION OF PM ALUMINIUM-LANTHANIDE ALLOYS T.Tianen et al. (Tampere University of Technology, Tampere, Finland.) Al-Gat%Mn-2%Ce and Al-3%Crl%Ti-l%Ce-l.S%Co alloys were mechanically alloyed from elemental powders and hot extruded. The objective of the study was to establish optimum process conditions and to investigate effects of heat treatment on structures. The mechanically alloyed powder consisted of a nanocrystalline solid solution with a mean grain size of 20 to 30 nm. In the asextruded materials the nanocrystalline grains were elongated in the extrusion direction. CeO, particles were detected and were shown to hinder growth of inter-metallic compound particles.