Crystal chemistry of higher tungsten oxides

Crystal chemistry of higher tungsten oxides

and Powder MetaIIurgy, Vol 41, No 2, 1994, 162-165. (In Japanese). The processing and properties of hot pressed Al with additions of up to 5Ovol%Al b...

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and Powder MetaIIurgy, Vol 41, No 2, 1994,

162-165. (In Japanese). The processing and properties of hot pressed Al with additions of up to 5Ovol%Al boride and up to 30% Mg boride were investigated. It is reported that well dispersed borides increased the mechanical properties including wear resistance. This is attributed to a dispersoid strengthening mechanism.

Copper EFFECT OF TEMPERATURE ON MECHANICAL PROPERTIES OF COPPER WITH ALUMINA DISPERSOIDS M.Besterci et al (Ustav Materialoveho Vyskumu SAV, Kosice, Slovakia), Polu+o& Baskove

Metalurgie, No 2-3, 1994, 22-28.

(In Czech). The mechanical properties of sintered Cu-5vol%AlzOs at 20 to 700°C and a strain rate of 4.5xlO*sec-’ were investigated. At 500 to 600°C there was a peak of plasticity showing high elongation. This is attributed to grain boundary slip and dynamic polygonization. The existence of superplasticity is predicted. EFFECTS OF ATOMIZATION PARAMETERS ON PROPERTIES OF COPPER POWDERS J. Dziemianko et al (Inst. Metal. Niezelaznych, Gliwice, Poland), Metal. Proszkoy Vol 27, No 3/4, 1994, 2-7. (In Polish). A study of high pressure atomization of Cu powders is described. Particle size distribution and yield of fine powder, as a function of water pressure, were determined. Gas and water atomized powders are compared and differences in particle sizes and morphologies described. Green strength of compacts made from water atomized powders is reported to be satisfactory. USE OF PARTICLE SURFACE AREA IN DIMENSIONAL CONTROL OF SINTERING A STEEL A. Griffo, R.M. German. (Pennsylvania State University, Pennsylvania, USA), Znt. J. Powder Metallurgy, Vol 30, No 4, 1994, 399-407. Production of PM parts to close dimensional tolerances is discussed. It is noted that swelling occurs in Fe-Cu-C and this is attributed to wetting of Fe particles by Cu and forcing apart of the particles. Efforts to limit this, by modification of particle surfaces, are described. This was accomplished by using powders made by different methods, atomized, carbonyl and sponge Fe. Mixtures which sintered without dimensional change were Cu infiltrated which improved the mechanical properties.

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SINTERING OF GAS AND WATER ATOMIZED COPPER POWDERS J. Piszcek. (Inst. Metal. Niezelaznych, Gliwice, Poland), Metal. Proszkow, Vol 27, No 3/4, 1994, 8-13. (In Polish). A comparative study of green and sintered Cu compacts made from gas and water atomized powders is described. The effects of powder characteristics and sintering conditions on density, shrinkage, electrical properties and depth of eddy current penetration were determined. Optimum process time as a function of powder size and shape were determined.

Iron and steel PROPERTIES OF HIGH DENSITY POWDER FORGED IRON BASED ALLOY M.C. Wang. (National Kaohsiung Inst. of Technology, Kaohsiung, Taiwan), Powder MetaZlur& Vol 37, No 3, 1994, 201-205. An experimental comparison of powder forged and sintered steels is described. Process conditions are considered. It is reported that a 2%Ni-2%Cu-0.5%C powder forged steel reached an density of 6.78 gm.cmm3and a Rockwell hardness of 95B compared with 65B for the sintered steel. Powder forging at 1000°C and 490 MPa gave a tensile strength of 600 MPa. DESULPHURIZATION OF STAINLESS STEEL CONTAINING MANGANESE SULPHIDE DURING SINTERING K.S. Hwang, C.H. Chiou. (National University, Taipei, Taiwan), Znt. J. Powder Metallurgr: Vol 30, No 4, 1994, 409-412. Desulphurization of 316L stainless steel, with MnS added to improve machinability, was investigated during sintering in H, Ar, vacuum or N/H. 91% of the S was removed in H at 1200°C for 1 hour, which is attributed to a catalytic effct. It is emphasized that the atmosphere must be carefully selected so as to avoid desulphurizarion. CHARACTERIZATION OF STEELS SINTERED FROM PREALLOYED IRONMOLYBDENUM POWDERS J.M. Torralba et al (Polytechnic University of Madrid, Madrid, Spain), Revista de Matall, Vol 31, No 1, 1995, 14-22. (In Spanish). The effects of composition on the properties of sintered steels, with additions of MO, Cu and Ni and a fixed %C, were investigated. Prealloyed Fe1.5%Mo powders and commercial sintering conditions were used in the study.

Magnesium MECHANICAL PROPERTIES OF MAGNESIUM COMPOSITES WITH DISPERSED BORON OR BORIDES K. Nishiyama et al (Science University of Tokyo, Tokyo, Japan,) J. Japan Sot. Powder and Powder Metallurm Vol 41, No 2,1994, 156-161. (In Japanese). The processing and properties of hot pressed Mg with additions of Al or Mg boride or amorphous B were investigated. It is reported that 15vol%Al boride increased the tensile strength to 405MPa due to a dispersion strengthening mechnism.

Tungsten CRYSTALLIZATION AND PROCESSING OF AMMONIUM PARATUNGSTATE J.W., van Put. (Union Miniere, Olen, Belgium), Znt. J. Refractory Metals and Hard Materials, Vol 13, No l/3, 1995, 61-76. An outline of the chemmistry of W compounds in aqueous solution is presented. Aspects of the crystallization of APT are discussed. the chemistry of conversion of APT into W oxide bronze, as the first pyrometallurgical stage in production of non-sag W, is described. Thermal decomposition of APT in air, N and reducing atmospheres is discussed. CHEMISTRY OF TUNGSTEN OXIDE BRONZES L. Bartha et al (Hungarian Academy of Sciences, Budapest, Hungary), Znt. J. Refractory Metals and Hard Materials, Vol 13, No l/3, 1995, 77-91. The chemistry of W bronzes and incorporation of dopants, which confer non-sag properties on W, are discussed. The complexity of W bronzes, due to formation of transient non-stoichiometric compounds during decomposition of Al?‘, is noted. The bronzes are thermally reduced to W by H. The structures of W oxide bronzes are described. CRYSTAL CHEMISTRY OF HIGHER TUNGSTEN OXIDES R.J.D. Tilley. (University College of Wales, Cardiff, UK), Znt. JReli-actory Metals and Hard Materials, Vol 13, No l/3, 1995, 93-109. The crystallography and chemistry of W oxides, some non-stoichiometric, with compositions from WOa to W03, are reviewed with reduced and fully oxidized analogues taken into account. Linkages between atoms in the structures are emphasized. Tetragonal and high temperature hexagonal W bronzes, intergrown phases and W phosphate bronze are considered.