Nickel Abnormal particles in nickel superalloy powder Y Zhang et al. (Central Iron and Steel Research Inst., Beijing, China.) Powder Metall. Industry, Vol lO, No 6, 2000, 7-13. (In Chinese.) A n investigation of the causes of abnormal particles in Ni-base superalloy powder, made by the plasma rotating electrode process, is described. The abnormal particles were characterized in an attempt to avoid their formation.
Vanadium Vanadium alloys for fusion reactor applications D.L.Smith et al. (Argonne National Laboratory, Argonne, USA.) Int. J. Refract. Metals Hard Mater., Vo118, No 4-5, 2000, 213-224. It was noted that V alloys had been identified for possible use as first-walls in fusion reactors. Properties for this were discussed. Current researches were concentrated on V-(3 to 9)wt%Cr and V-(3 to 10)%Ti which were compared with V-4%Cr-4%Ti. Developments in V alloys are reviewed and future issues considered.
Reduction of impurity levels in V alloys for fusion reactor uses T.Muroga, T.Nagasaka. (National Inst. for Fusion Science, Gifu, Japan.) Int. J. Refract. Metals Hard Mater., Vo118, No 4.5, 2000, 225-230. The need for low interstitial impurity levels, C, O and N, in V alloys for fusion reactor uses was emphasized. Researches aimed at reducing impurity levels in V-4%Cr-4%Ti were reported.
Laser welding of vanadium-chromium-titanium D.L.Smith et al. (Argonne National Laboratory, Argonne, USA.) Int. J. Refract. Metals Hard Mater., Vo118. No 4-5, 2000, 231.236. An investigation of laser welding for fabrication of V-4%Cr-4%Ti alloys is described. A 1.6 kW pulsed Nd-YAG laser was used. Effects of process parameters on weld quality are evaluated with metallurgical characterization. It is reported that welds with deep penetration, free from defects and O contamination, had been made.
Ceramics Dense amorphous bulk silicon-carbon-nitrogen ceramics S.Ishihara, F.Wakai. (Tokyo Inst. of Technology,Yokohama, Japan.) J. Jpn Soc. Powder/Powder Metall., Vo147, No 4, 2000, 381-385. (In Japanese.) Si-C-N ceramics were prepared by HIP from polymeric precursors to investigate
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densification behaviour. As-pyrolysed the ceramics were porous and deformed several % in compression at 1400 °C. HIP at 980 MPa and 1600 °C resulted in significant densification but residual pores were larger. Dense Si-CN-B ceramics were also made.
Coatings An anti-bacterial metal coating W.Urushihara et al. (Kobe Steel Co Ltd, Kobe, Japan.) Kobe Steel Engineering Rep., Vo150, No 2, 2000, 3437. (In Japanese.) It is reported that a metallic anti-bacterial coating, applicable to A1, Ti, stainless steel and other materials, had been developed. It is shown that the anti-bacterial, anti-fungal and anti-algal properties of the coating are superior to conventional inorganic materials. Examples of applications are presented.
Composite materials Optimization and fabrication of nickel-alumina-nickel compositionally graded material A.Kawasaki et al. (Tohoku University, Sendai, Japan.) J. Jpn Soc. Powder/Powder Metall., Vol 47, No 4, 2000, 347-352. (In Japanese.) It is reported that a compliant pad, serving as an electrode and a thermal conductor, had been fabricated for use between a heat source and a cooling duct, in an electronic device. The pad consisted of a sandwich of two layers of Ni with A120 3 and compositionally graded layers separating Ni from A120 3. The requirements of the part are described. The part structure was optimized for analysis of stress and thermal conduction, densification of powders and processing.
Thermal expansion of titanium carbide-nickel cermets X.Zhang et al. (Harbin Inst. of Technology, Harbin, China.) PM Technology,Vo118, No 4, 2000, 243-246. (In Chinese.) TiC-Ni composites were made by compaction and self-propagating high temperature synthesis. Relationships between thermal expansion and temperature were investigated. It is shown that the temperature coefficient of expansion increases with increase in temperature and with increase in %Ni at the same temperatures.
Thermal stability of aluminium matrix composites by hot forging Y.Li et al. (Central South University of Technology, Changsha, China.) PM Technology,Vol 18, No 4, 2000, 247-251. (In Chinese.) A n investigation of processing of an AI-FeV-Si-SiC heat resistant composite is described. It is showp that strength and wear resistance is improved by the SiC particles. Wear properties
were studied at elevated temperatures and were found to improve above 300 °C.
Fabrication of copper-alumina composites by internal oxidation Y.Yu et al. (Northwestern Polytechnical University, Xi'an, China.) PM Technology,Vo118, No 4, 2000, 252-265. (In Chinese.) It is reported that a Cu-AI20 3 composite had been produced by an internal oxidation method. Effects of process conditions, in O at 300 Pa pressure, on the size of particles, were studied in terms of possible reduction in size for improvement in properties.
Electrical and magnetic materials Mechanical properties of piezo-electric ceramics with nanoparticles K.Niihara et al. (Osaka University, Ibaraki, Japan.) J. Jpn Soc. Powder/Powder Metall., Vol 47, No 4, 2000, 391-395. (In English.) It is reported that Pb zirconate-titanate piezo-electric ceramics, with additions of nanosized MgO or AlzO 3 particles, had been prepared by pressing and sintering. The additions increased fracture strength with little effect on piezo-electric properties.
Hard materials and tool steels Morphology changes during heating of silicon nitride-boron nitride J.Hojo et al. (Kyushu University, Fukuoka, Japan.) J. Jpn Soc. Powder/PowderMetall., Vo147, No 4, 2000, 396399. (In English.) Amorphous Si3N4-BN materials were produced by vapour phase reaction in SiCI4-BC13H2-NH 3 mixtures. Y203-A1203 was added to aid sintering. Si3N 4 alone showed grain growth and this was inhibited by BN. The composite remained amorphous up to 1600 °C. Phase separation occurred above 1600 °C, BN crystals forming on Si3N 4.
Intermetallic materials Preparation of iron silicide by mechanical alloying and spark plasma sintering M.Naka et al. (Osaka University, Osaka, Japan.) J. Jpn Soc. Powder/Powder Metall., Vo147, No 4, 2000, 369374. (In Japanese.) It is reported that ]SFeSi2 had been made from elemental powders by mechanical alloying and spark plasma sintering for up to four hours at 800 °C. The sintering time required to synthesize FeSi 2 depended on milling time. Density of 90% up to 97.4% was attained by 1200 minutes milling and 10 minutes sintering.