properties are explained in terms of the impurities and non-uniform distribution within the particles. CHARACTERISTICS OF A Ni BASE HEAT RESISTANT ALLOY AFTER LIQUID PHASE SINTERING
A.P. Gulyaev, et al, Metalloved, Term Obrab, Met, No 8, 1990, 51-56. In Russian. The effects of liquid phase sintering and HIP on the structure and properties of a PM Ni alloy, Ni-10%Co-16%Cr-12%A1-2%Ti2%Mo-2%W-l%Nb, were investigated. The powder structure was 100% 7 phase. After processing Ni3A1, 7' phase, carbides and nitrides were detected in t h e microstructure and the mechanical properties were reduced. Heat treatment restored the mechanical properties. APPLICATION OF COMBUSTION SYNTHESIS TO PRODUCTION OF INTERMETALLIC SHAPE MEMORY ALLOYS (SMA) IN Ni-Ti
JZ. Moore, H.C. Yi, (University of Auckland, New Zealand), Materials Science Forum, 1990, 56-58 and 637-642. Combustion synthesis makes use of the exothermie heat of reaction to make certain intermetaUic compounds and has been applied to produce NiTi shape memory alloys from equiatomic mixtures of Ni and Ti powders. The alloys were completely fused during combustion and could be r e a d i l y f a b r i c a t e d by r o l l i n g . T h e advantage of the technique lies in the ability to co n t ro l c o m p o s i t i o n more accurately than is possible with ingot technology. The effect of Ni particle size on SMA temperatures which were in the range 20 to 100°C, was studied. It was also found possible to control SMA temperature by additions of a third element to the alloy.
EFFECTS OF DOPING ON HIGH TEMPERATURE STRENGTH OF PM TUNGSTEN WIRES
K. Tanoue, et al, (Kyushi Institute of Technology, Kitaktushu, Japan), J. Japan Inst. of Metals, Vol 54, No 9, 1990, 991-998. In Japanese. The c h a r a c t e r i s t i c s of s e c o n d a r y recrystallized grains grown in W wire with and without doping agents have been studied at different heating rates. The creep strength has been measured with respect to the secondary recwstailization. Doped wire with large grain size shows transgranular fracture but in the nondoped wire the fracture is intergranular. Creep stress exponents were calculated. It is suggested that bubbles may be present in the doped wire and that the configuration of the grains affects the creep stress exponent. It was shown that the presence
74 MPR May 1991
of elongated grains in wire suppresses creep strain at high temperatures. PRODUCTION OF FINE W AND WC POWDERS BY VAPOUR PHASE REACTION
G.Y. Zhao, et al, (State University of New York, USA), J. Less Common Metals, Vol. 163, No 2, 1990, 269-280. Vapour phase reactions to produce ultrafine powders of refractory metals and compounds are described. W and WC have been produced on a laboratory scale. The powders were found to be spherical in shape, free from pores and with a narrow size distribution range. The characteristics of the powders have been correlated with process parameters.
Electrical and Magnetic Materials PM MATERIALS WITH PRESCRIBED ELECTRICAL AND MAGNETIC PROPERTIES FOR APPLICATION IN ELECTRIC INDUCTION MOTOR COMPONENTS
E.A. Anisimova, et al, Poroshkavaya Metallurgiya, No 9, 1990, 87-91. In Russian. The production of PM metal/ceramic components, for electrical machines, with specified electrical and magnetic properties, is described with respect to production parameters. Parts have been tested in experimental machines. MEASUREMENT OF ELECTRICAL CONDUCTIVITY OF SiC POWDERS BY ELECTRON PARAMAGNETIC RESONANCE
A.S. Kheifets, et al, P o r o s h k a v a y a Metailurgiya, No 9, 1990, 95-99. In Russian. Electrical properties of SiC powders were measured by electron paramagnetic resonance with regard to additives used in manufacture. The electrical conductivity was found to be closely related to the concentration of additives used. The effect of N2 on conductivity of SiC was measured. EFFECT OF SUBSTITUTION OF OTHER ELEMENTS FOR Nd ON MAGNETIC PROPERTIES OF NdFeB SINTERED MAGNETS
M. Leonowicz, (Polytechnic of Warsaw, Poland), Archives of Metallurgy, Vol 35, No 3, 1990, 475-480. The effects of elements added in partial substitution for Nd on the magnetic properties of 16%(Nd +X)77%(85%Fe+15%Co)-7%B sintered magnets have been studied. (X = Ga, Nb, Zr, Ti, Cr, Mo or Dy). Remenance and coercive force were reduced and the d e c l i n e in m a g n e t i c p r o p e r t i e s is a t t r i b u t e d to decrease in anisotropy,
saturation magnetization and the presence of magnetically soft precipitates in the structure.
Hard Materials and Tool Steels EFFECT OF EXTENDED HEATING ON OXIDATION OF TITANIUM CARBIDE ALLOYS
V.B. Voitovich, et al, Poroshkavaya MetaUurgiya, No 9, 1990, 41-46. In Russian. The oxidation of TiC has been studied during long exposure to air at 1000°C. A two layer scale was formed and was examined by scanning electron microscopy with microanalysis facilities used to determine impurity (Fe, Co, Cr and Si) distribution. The outer layer of the scale was found to be enriched in impurities. The impurities were also found to be effective in the promotion of sintering. STRENGTH OF A DIAMOND BEARING COMPOSITE LAYER ON A TUNGSTEN CARBIDE SUBSTRATE
D.K. Bronshtein, et al, Poroshkavaya Metallurgiya, No 9, 1990, 64-68. In Russian. A diamond bearing hard material has been applied to a high temperature WC substrate by hot compaction, and physical and mechanical properties measured. Improvements in crack resistance and bend strength, in comparison with low t e m p e r a t u r e WC, w i t h a s u p e r h a r d coating, are reported. Reduced thermal expansion is also reported. ELECTRON STRUCTURE OF NONSTOICHIOMETRIC TUNGSTEN CARBIDES W2Cx
O.Y. Khizhun, et al, P o r o s h k a v a y a MetaUurgiya, No 9, 1990, 77-83. In Russian. Th e e l e c t r o n s t r u c t u r e of n o n stoichiometric tungsten carbide has been determined by photoelectron spectroscopy and X-ray e m i s s i o n and a b s o r p t i o n spectroscopy. Hybridization of electron states was observed. Reduction of %C r e s u l t s in l i n e b r o a d e n i n g in t h e photoelectron spectra. Charge transfer from W atoms to C atoms was detected. MANUFACTURE OF TOOL STEELS FOR PLASTICS INJECTION MOULDING MACHINE DIES
H. Esaka, et al, (Kobe Steel, Japan), Kobelco Technology Review, No 9, 1990, 19-23. The production of injection moulding machine dies in two tool steels, Fe-2%C18%Cr-2%Mo-l%V and Fe-l%C-18%Crl%Mo-l%V, is described. Gas atomized powders and HIP processing were used. The alloys were reported to have good mechanical properties, high wear and