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A coated powder approach for tungsten alloys
VARIOUS PROCESSES FOR ZiVSZTU FORMATION OF ALUMINIUMALUMINIUM NITRIDE
and intermetallic materials
Y.Takeda et al. (Sumitomo Electric Industries, Koyakita, Japan.) It was noted that the high hardness of SIC or A&O, may render Al matrix composites with these as the reinforcement to be too abrasive for some applications. Al-AlN was suggested as an alternative although these may have poor Al-AlN interface bonding. This could be rectified by forming the AlN in situ. Al-AlN composites were produced by a number of methods, press-and-sinter, powder forging and powder extrusion to near net shape with in situ synthesis of AlN. Applications in wear resistant parts were discussed.
ADVANCED INTERMETALLIC MATERIALS MADE BY MECB.ANICAL ALLOYING AND REACTIVE HIP
SINTERED TITANIUM-TITANIUM CARBIDE COMPOSITES D.Alman. (Albany Research Center, Oregon, USA.) It was reported that Ti-TiC composites, with 2.5, 5, 10, 20 and 40vol%TiC particles had been made by a pressand-sinter route. The tensile properties of the composites and Ti were evaluated. The influence of the TIC concentration on structure and properties was described. LOW COST WEAR RESISTANT METAL MATRIX COMPOSITES E.Ravnborg. (Danish Technological Inst., Taastrup, Denmark.) It was reported that a low cost hard steel with 1.5%C-12%Cr-l%Mo-0.8%V had been prepared from powder. The Vickers hardness was 500 and the structure was a martensitic matrix with a high proportion of carbides. Wear resistance was high. Potential applications were discussed. MECIIANICAL PROPERTIES OF TUNGSTEN CARBIDE-COPPER COMPOSITE MADE BY OSPREY PROCESS of Chile, R.Palma et al. (University Santiago, Chile.) Mechanical properties of copper reinforced with 5 and 20% by volume of tungsten carbide particles with particle sizes of 5 pm and 20 pm were investigated. Preforms were made by the Osprey process and hot rolled or hot extruded. The preforms had coarse structures and medium hardness. Working increased hardness and density and refined the matrix grain structure. Structure and properties were discussed with regard to hardening mechanisms.
40 MPR October 1999
Superalloys
S.van Dyck et al. (Catholic University, Leuven, Heverlee, Belgium.) The potential of Ni,(Si, Ti) for structural applications in aggressive environments with regard to mechanical alloying and PM techniques was investigated. MA with reactive hot isostatic pressing was shown to offer a high degree of microstructural control resulting in superior mechanical properties. The yield strength of the PM alloy was double that of cast alloys and had 5% elongation. MICROSTRUCTURE-PROPERTY RELATIONSHIPS IN HIP STELLITE POWDERS M.Ashworth et al. (University of Birmingham, Birmingham, UK.) Structure and properties of HIP processed stellite were studied in order to establish a database to facilitate materials selection. Attention was given to powder characteristics and their effect on consolidation. Surface compositions were determined by Auger spectroscopy and densification by dilatometry. Compositions and distribution of secondary phases were determined. Effects of HIP process conditions on structure and properties were discussed in terms of optimum process temperature. SINTERING AND HOT ISOSTATIC PRESSING OF NICKEL-TITANIUM ALLOYS FROM ELEMENTAL POWDERS U.van der Crone et al. (Forschungszentrum Julich GmbH, Julich, Germany.) The shape-memory effect in NiTi was discussed. The use of PM to prepare NiTi alloys was considered to be viable and low cost. Pressed elemental powders were sintered at 850 to 1050°C and HIP was used to attain full density. The shape memory effect and mechanical and physical properties of as-sintered and HIP samples were compared. MECHANICAL CIIARACTERIZATION OF NICKEL ALUMINIDE L.Plazanet. (LMCTS, F.Nardou, Limoges, France.) Synthesis of NiAl from powder, by two routes, was investigated. Elemental powders were mixed and pressed. Synthesis was either at low temperature, 58o”C, by self-combustion, or at 1400°C by reactive sintering. In both cases hot pressing was used to attain 98% density. Mechanical
properties were determined. Reactive sir&ring was used to synthesize NiAl-SiC and NiAl-ZrO, composites. ZrO, increased strength and toughness and both reinforcements increased creep properties. FORMATION OF INTERMETALLICS IN IRON-ALUMINIUM DURING REACTIVE SINTERING et J.V.Wood Nottingham Nott~~gha’~n~~sity Of The behaviour of Fe ‘and Al in PM alloys, during synthesis of intermetallic compounds, was investigated using diffusion couples. Samples were heated below and above the temperatures required for reactive sintering. At the low temperatures Al-rich compounds formed only in Fe close to the Fe-Al interface by diffusion of Al into the Fe. Al was deposited in the grain boundaries of the Fe. At higher temperatures, in the presence of a liquid phase, intermetallics formed in both Fe and Al on both sides of the interface.
Refractory
metals
A COATED POWDER APPROACH FOR TUNGSTEN ALLOYS A.Bose et al. (Powermet Inc, Petaluma, USA.) Preparation of W heavy alloys and WC-Co was reviewed with regard to press and liquid phase sinter routes, problems of grain growth, lack of homogeneity and high contiguity. It was reported that these problems can be minimized by use of coated powders. The benefits of using W powder, coated by CVD were discussed. EFFECTS OF MANGANESE ON STRUCTURE OF TUNGSTENNICKEL-IRON HEAVY ALLOY E.P.Kim et al. (Agency for Defence Development, Taejon, Korea.) The effects of adding Mn to W heavy alloys, with 94 and 97at%W and a Ni:Fe ratio of 8:2, were investigated. Mn was added by infiltration at 1485°C in dry H. Mn initially resulted in increased W grain growth, which was later reduced. The alloy with 97%W had the larger grain size. Changes in grain growth rates were attributed to solution/precipitation and diffusion effects. MORPHOLOGICAL EFFECT OF GRAINS ON DEFORMATION MECBANISM MAPS OF FINE TUNGSTEN WIRE K.Tanoue. (Kyushu Inst. of Technology, Kitakyushu, Japan.) Deformation maps, which link stress, temperature and strain rate for fine W wires were reviewed and the
and intermetallic materials
Y.Takeda et al. (Sumitomo Electric Industries, Koyakita, Japan.) It was noted that the high hardness of SIC or A&O, may render Al matrix composites with these as the reinforcement to be too abrasive for some applications. Al-AlN was suggested as an alternative although these may have poor Al-AlN interface bonding. This could be rectified by forming the AlN in situ. Al-AlN composites were produced by a number of methods, press-and-sinter, powder forging and powder extrusion to near net shape with in situ synthesis of AlN. Applications in wear resistant parts were discussed.
ADVANCED INTERMETALLIC MATERIALS MADE BY MECB.ANICAL ALLOYING AND REACTIVE HIP
SINTERED TITANIUM-TITANIUM CARBIDE COMPOSITES D.Alman. (Albany Research Center, Oregon, USA.) It was reported that Ti-TiC composites, with 2.5, 5, 10, 20 and 40vol%TiC particles had been made by a pressand-sinter route. The tensile properties of the composites and Ti were evaluated. The influence of the TIC concentration on structure and properties was described. LOW COST WEAR RESISTANT METAL MATRIX COMPOSITES E.Ravnborg. (Danish Technological Inst., Taastrup, Denmark.) It was reported that a low cost hard steel with 1.5%C-12%Cr-l%Mo-0.8%V had been prepared from powder. The Vickers hardness was 500 and the structure was a martensitic matrix with a high proportion of carbides. Wear resistance was high. Potential applications were discussed. MECIIANICAL PROPERTIES OF TUNGSTEN CARBIDE-COPPER COMPOSITE MADE BY OSPREY PROCESS of Chile, R.Palma et al. (University Santiago, Chile.) Mechanical properties of copper reinforced with 5 and 20% by volume of tungsten carbide particles with particle sizes of 5 pm and 20 pm were investigated. Preforms were made by the Osprey process and hot rolled or hot extruded. The preforms had coarse structures and medium hardness. Working increased hardness and density and refined the matrix grain structure. Structure and properties were discussed with regard to hardening mechanisms.
40 MPR October 1999
Superalloys
S.van Dyck et al. (Catholic University, Leuven, Heverlee, Belgium.) The potential of Ni,(Si, Ti) for structural applications in aggressive environments with regard to mechanical alloying and PM techniques was investigated. MA with reactive hot isostatic pressing was shown to offer a high degree of microstructural control resulting in superior mechanical properties. The yield strength of the PM alloy was double that of cast alloys and had 5% elongation. MICROSTRUCTURE-PROPERTY RELATIONSHIPS IN HIP STELLITE POWDERS M.Ashworth et al. (University of Birmingham, Birmingham, UK.) Structure and properties of HIP processed stellite were studied in order to establish a database to facilitate materials selection. Attention was given to powder characteristics and their effect on consolidation. Surface compositions were determined by Auger spectroscopy and densification by dilatometry. Compositions and distribution of secondary phases were determined. Effects of HIP process conditions on structure and properties were discussed in terms of optimum process temperature. SINTERING AND HOT ISOSTATIC PRESSING OF NICKEL-TITANIUM ALLOYS FROM ELEMENTAL POWDERS U.van der Crone et al. (Forschungszentrum Julich GmbH, Julich, Germany.) The shape-memory effect in NiTi was discussed. The use of PM to prepare NiTi alloys was considered to be viable and low cost. Pressed elemental powders were sintered at 850 to 1050°C and HIP was used to attain full density. The shape memory effect and mechanical and physical properties of as-sintered and HIP samples were compared. MECHANICAL CIIARACTERIZATION OF NICKEL ALUMINIDE L.Plazanet. (LMCTS, F.Nardou, Limoges, France.) Synthesis of NiAl from powder, by two routes, was investigated. Elemental powders were mixed and pressed. Synthesis was either at low temperature, 58o”C, by self-combustion, or at 1400°C by reactive sintering. In both cases hot pressing was used to attain 98% density. Mechanical
properties were determined. Reactive sir&ring was used to synthesize NiAl-SiC and NiAl-ZrO, composites. ZrO, increased strength and toughness and both reinforcements increased creep properties. FORMATION OF INTERMETALLICS IN IRON-ALUMINIUM DURING REACTIVE SINTERING et J.V.Wood Nottingham Nott~~gha’~n~~sity Of The behaviour of Fe ‘and Al in PM alloys, during synthesis of intermetallic compounds, was investigated using diffusion couples. Samples were heated below and above the temperatures required for reactive sintering. At the low temperatures Al-rich compounds formed only in Fe close to the Fe-Al interface by diffusion of Al into the Fe. Al was deposited in the grain boundaries of the Fe. At higher temperatures, in the presence of a liquid phase, intermetallics formed in both Fe and Al on both sides of the interface.
Refractory
metals
A COATED POWDER APPROACH FOR TUNGSTEN ALLOYS A.Bose et al. (Powermet Inc, Petaluma, USA.) Preparation of W heavy alloys and WC-Co was reviewed with regard to press and liquid phase sinter routes, problems of grain growth, lack of homogeneity and high contiguity. It was reported that these problems can be minimized by use of coated powders. The benefits of using W powder, coated by CVD were discussed. EFFECTS OF MANGANESE ON STRUCTURE OF TUNGSTENNICKEL-IRON HEAVY ALLOY E.P.Kim et al. (Agency for Defence Development, Taejon, Korea.) The effects of adding Mn to W heavy alloys, with 94 and 97at%W and a Ni:Fe ratio of 8:2, were investigated. Mn was added by infiltration at 1485°C in dry H. Mn initially resulted in increased W grain growth, which was later reduced. The alloy with 97%W had the larger grain size. Changes in grain growth rates were attributed to solution/precipitation and diffusion effects. MORPHOLOGICAL EFFECT OF GRAINS ON DEFORMATION MECBANISM MAPS OF FINE TUNGSTEN WIRE K.Tanoue. (Kyushu Inst. of Technology, Kitakyushu, Japan.) Deformation maps, which link stress, temperature and strain rate for fine W wires were reviewed and the