ener~' of the milled powder was found to be lower than the free energy of mixing of supercooled liquid Cu-Pb alloy and is insufficient to give complete amorphization. SINTERING OF LEAD BRONZE CONTAINING TIN S. Kumar et al (Indian Inst of Technology, Kanpur, India), J Materials Engineering, Vol 13, No 3, 1991 237-242. The sintering of leaded bronze with 0 to 4 wt%Sn is described. Two types of powder were used, one was partially prealloyed and the other was a mechanical mixture. Compacts were sintered in that 800°C for 20, 40 and 60 minutes and dimensional changes, porosity, hardness, electrical conductivity and crushing strength were measured. The prealloyed powder is reported to show the higher sintered density and the crushing strength of the compacts made from the mixed powder was higher.
Iron and steel Illlll
MECHANISM OF ENHANCEMENT OF ALLOYING AND SINTERING IN IRONSILICON COMPACTS WITH FLUXES X. Qu and J~L Lund, (University of British Columbia, Canada), J. Central South Inst. Mining and Metallurgy (China), Vol 21, No 4, 1990, 420-426. It is reported that the addition of small amounts of Na or K carbonates enhances the sintering and alloying of Fe-Si alloys. This is attributed to the removal of oxides from the surfaces of the Si particles and the formation of a liquid silicate glass in the pores of the compact. The s i n t e r i n g s h r i n k a g e shown by Fe-Si alloys is reported to involve a directional inter d i f f u s i o n p h e n o m e n o n which, it is suggested, is related to, the activated sintering by the glass-like phase. MECHANICAL ALLOYING OF IRON AND TUNGSTEN P.F. Relushko et al, (Academy of Sciences of Russia, Moscow, Russia), Zh. ~ z , tOzim, Vol 64, No 10, 1990, 2858-2864. (In Russian). A description is given of the structures developed in mechanically alloyed Fe-W mixtures. It is reported that the powders consists of paramagnetic Fe with interfaces close to those in Fe. The disordered phases Fe7We and Fe2W were also detected. STUDY OF THE CHEMICAL REDUCTION PREPARATION CONDITIONS OF A M O i ~ H O U S IRONBORON ALLOY POWDERS J. Jiang et al, (University of Saarlandes, Saarbrucken, Germany), J. Non-Crystalline
Solids, Vol 124, No 2-3, :1990;~.~3~144. It was reported t h a t u i ~ n ~ F e , B powders had been produced by chemical reaction in aqueous solutions. An account is given of the effects of process conditions on the structure and properties of the powder. Optimum process conditions were determined. WEAR RESISTANCE STUDIES ON IRONCOPPER SINTERED PREFORMS T.K. Das et al, (Visakhapatnam Steel Plant, Agra, India), Powder Metallurgy Science and Technology, Voi 3, No 1, 1991, 35-42. Studies of abrasive wear of Fe and Fe-Cu alloys, with and without graphite additions and with a ceramic coating, were carried out. The wear tests used a corundum disk at different loads and sliding speeds. It is shown that there is a linear relationship between wear rate (weight loss) and time, Graphite, seen in the microstructure, acts as a lubricant. INFLUENCE OF PHOSPHORUS ADDITIONS ON THE MECHANICAL PROPERTIES OF STAINLESS STEEL M. Nakamura et al, (Iwate University, Ueda Morioka, Japan), J.Japan Soc. Powder and Powder Metallurgy, Vol 39, No 1, 1992, 2427. (In Japanese). The effects of sintering temperatures and the additions of up to 1 wt%P on the mechanical properties of PM austenitic stainless steel were investigated. It is reported t h a t high values of tensile s t r e n g t h , over 550 MPa w i t h 40% elongation, and impact strength, 250 J/ cm 2, were obtained with additions of 0.2 to 0.5 wt%P and sintering range 1350 to 1440°C. The mechanism by which a high sintered density was obtained was a eutectic reaction between the Fe phase and (Fe, Cr)3P. EFFECTS OF GRAPHITE CONTENT ON DIFFUSION BONDING OF IRON POWDER COMPACTS WITH APPLIED PRESSURE H. Iwasaki and E. Shorakui, (Himeji Inst, of Technology, Shosha Himeji, J a p a n ) , J.
J a p a n Soc. P o w d e r a n d P o w d e r Metallurgy, Vol 39, No 1, 1992, 33-38. (In Japanese). The effects of temperature, pressure and graphite content on the diffusion bonding of Fe powder compacts were studied. It is reported that the maximum value of shear strength of the diffusion bonded joint was found at 0.2%C when bonded at 700 to 1000°C and 10 to 60 M I ~ Subsequent s i n t e r i n g at 1100°C for 1 hour and i n c r e a s e d C c o n t e n t were f o u n d to increase the shear strength of the joint. For 100% j o i n t efficiency a b o n d i n g t e m p e r a t u r e of 800 to 900°C a n d pressures of 20 to 40 MPa were required for a %C up to 0.8%.
Nbqmmm POWDER PROCESSING AND FABRICATION OF RHENIUM B.D. Bryskin and F.C. Danek, J. of Metals, Vol 43, No 7, 1991, 24-26. Properties and applications of Re and alloys of Re with other refractory metals are discussed. In particular high temperature applications are considered. It is suggested that Re has considerable application potential.
FATIGUE PROPERTY ENHANCEMENT OF TITANIUM ALLOYS BY USE OF BLENDED ELEMENTAL POWDERS M. Hagiwara et al, (National Research Inst, for Metals, Tokyo, Japan), Iron and Steel Inst, of Japan Int., Vol 31, No 8, 1991, 922930. The p a p e r d e s c r i b e s a t t e m p t s to improve the fatigue properties of Ti-6%AI4%V by the use of blended elemental powder, the Ti powder having an extra low CI content. The effects of process conditions on microstructure and fatigue properties are described and several microstructure are reported to have been obtained. Fatigue initiation mechanisms are correlated with microstructure.
Mtermetm///e m a t e r M / s IIII
INTERMETALLIC COMPOUNDS: AN UPDATE I. Baker and E.P. George, (Dartmouth College, Hanover, New Hampshire, USA), Metals and Materials, Vol 8, No 6, 1992, 318-323. The factors influencing the ductility of intermetallic compounds are described and discussed. The factors are classified as extrinsic, environmental conditions, impurities, surface finish, 'pest' (grain b o u n d a r y s e g r e g a t i o n of i n t e r s t i t i a l impurities) and cooling rate effects, and i n t r i n s i c factors, nucleation, grain boundaries, mechanisms of deformation and notch sensitivity. The improvement of ductility and the industrial applications of i n t e r m e t a l l i c s a r e d i s c u s s e d . The intermetallic materials of current interest include the aluminides and silicide of Ni, Ti, Zr, Nb, Fe, Mo and Ti. SYNTHESIS OF TITANIUM ALUMINIDE BY MECHANICAL ALLOYING I(. Kobayashi et al, (Government Industrial Research Inst, Nagoya, Japan), Reports of
Government Industrial Research Inst. Nagoya, Vol 39, No 11, 1990, 433-438. (In
MPR September 1992 39