Effects of additives on sintered properties of copper compacts

PM

a n d Ti-A1 alloys is described. Different mechanisms, droplet formation, l i g a m e n t disintegration a n d film disintegration, are shown to operate u n d e r different process conditions. Effects of process variables on particles morphology are d e m o n s t r a t e d .

PRESSING EXPLOSIVE COMPACTION OF ALUMINIUM-SILICON CARBIDE COMPOSITES

I~ Sivakumar et al, (Defence Metallurgical R e s e a r c h Lab, H y d e r a b a d , I n d i a ) . Int. J. Powder Metallurgy Vol 28, No 1, 1992, 63-68. The use of explosive compaction for c o n s o l i d a t i o n of A1-SiC m e t a l m a t r i x composites (MMC) is described. Details a r e given of t h e effects of e x p l o s i v e thickness, i m p a c t energy a n d t h e ratio of explosive to powder. The p r o p e r t i e s of explosively compacted and hot rolled material were r e p o r t e d to be similar to specimens m a d e by a CIP-sinter-hot roll sequence. COLD DIE FORGING OF S I N T E R E D PREFORMS AS AN ALTERNATIVE TO DOUBLE P R E S S I N G

B.A. F r i s c h e t al, ( M a x - P l a n c k I n s t . J. Powder Metallurgy, Vol 28, No 1, 1992, 53-61. An investigation of defect healing d u r i n g sinter-HIP of W-Ni alloys a n d a l u m i n a / g l a s s m i x t u r e s was carried out w i t h regard to d e n s i f i c a t i o n a n d e l i m i n a t i o n of large defects. The defects are m a c r o p o r e s a n d are considered to arise from i n a d e q u a t e powder processing of differential sintering of agglomerated powders. Creep p a r a m e t e r s a n d viscosities were m e a s u r e d by single s p h e r e deformation in a load dilatometer, t h e results are r e p o r t e d to be in good a g r e e m e n t with m e a s u r e m e n t of densities of HIP samples. The suggested m e c h a n i s m of macropore elimination is by m i x e d flow of grains a n d t h e i n t e r g r a n u l a r p h a s e for w h i c h t h e c o n d i t i o n s w e r e determined. The results are discussed as a function of t e m p e r a t u r e , time, pressure a n d grain size. SOLID STATE S l N T E R I N G OF H E T E R O G E N E O U S SYSTEMS WITH UNLIMITED SOLUBILITY OF COMPONENTS

I~ Brand, w. Schatt, (Technical Uni of Dresden, Germany), Neue H~tte, Vol 46, No 9, 1991, 321-325, (In German,) Investigation of the kinetics of shrinkage, changes in defect c o n c e n t r a t i o n a n d degree of homogenization during t h e non-isothermal stage of sintering of Ni-Cu a n d Ni-Co alloys are described. Correlations between the above parameters are discussed.

80 MPR May 1992

LITERATURE

REVIEW

FUNDAMENTALS E F F E C T OF POWDER FILLING FRACTION OF PARTICLE SIZE AND ENERGY CONSUMPTION IN GRINDING

Y. Zeng, E. Forssberg. (Uni of Lulefi, Sweden), Scand. J Metallurgy, Vol 20, 1991, 300-304. The r e l a t i o n s h i p s between particle size d i s t r i b u t i o n a n d process p a r a m e t e r s in ball a n d rod milling are discussed w i t h respect to energy consumption, a b o u t 10% being dissipated in t h e m o t o r a n d 10 to 15% in t h e gears a n d bearings. The particle size d i s t r i b u t i o n is r e p o r t e d to be describable by a parabolic-sine equation_ M a t h e m a t i c a l analysis of t h e r e s u l t s shows t h a t t h e m a x i m u m energy efficiency occurs w h e n t h e powder is 50 or 60% of t h e charge (powder a n d c r u s h i n g bodies) for rod a n d ball mills respectively. ELASTO-PLASTIC FINITE E L E M E N T ANALYSIS OF U P S E T T I N G OF A POROUS METAL CYLINDER

H.S. Kim, D.N. Lee, (Seoul National Uni Korea), J. Korean Inst. of Metals, Vol 29, No 7 11991, 703-708, (In Korean). The use of finite e l e m e n t analysis in t h e study of t h e d e f o r m a t i o n of sintered porous c y l i n d e r s is d e s c r i b e d . Yield s u r f a c e expansion, due to work h a r d e n i n g a n d densification and contraction due to tensile stresses are t a k e n into account. Below a critical density t h e yield surface is a s s u m e d to have a small finite value w i t h a limit of 10 -1°. The m e t h o d h a s been applied to t h e u p s e t t i n g of p o r o u s cylinders. Calculated results are r e p o r t e d to be good a g r e e m e n t with e x p e r i m e n t a l data. Folding a n d c r a c k i n g d u e to b a r r e l l i n g of t h e c o m p a c t s are predicted.

PRODUCTS" Aluminium E F F E C T S OF IRON AND NICKEL A D D I T I O N S ON THE P R O P E R T I E S OF RAPIDLY SOLIDIFIED ALUMINIUM ALLOYS

S-G, Lim et

al,

(Nihon

Uni, J a p a n ) ,

J. Japan Inst, Light Metals, Vol 41, No 4, 1991, 251-257, (In J a p a n e s e ) . The p r o d u c t i o n of flake form A1 alloys, with Ni a n d Fe additions, by atomization a n d s p l a t c o o l i n g is d e s c r i b e d . T h e consolidated powders were found to have high h a r d n e s s due to a fine dispersion of FeNiA10 after p r e c i p i t a t i o n hardening. MICROSTRUCTURE AND P R O P E R T I E S OF MECHANICALLY ALLOYED ALUMINIUM-TITANIUM ALLOY

Y.S. Lim, KS. Lee, (Hanyang Uni, Seoul, Korea), J. Korean Inst. of Metals, Vol 29,

No 7, 1991, 749-758, (In Korean). A study of mechanically alloyed (MA) powder a n d h o t e x t r u d e d Al-10wt%Ti is r e p o r t e d AlaTi is formed at 260°C during degassing a n d is found to be t h e r m a l l y stable at 300, 400 a n d 500°C for 1-40 hours. The tensile p r o p e r t i e s are r e p o r t e d to be superior to alloys 2014-T6 a n d 2219-T81 a n d t h i s is a t t r i b u t e d to greater h o m o g e n e i t y a n d f i e n d d i s p e r s i o n s of AIaT6 a n d carbide inclusions. Increase in %Ti increases t h e s t r e n g t h b u t reduces t h e ductility. PRODUCTION OF ALUMINIUM-IRONC E R I U M ALLOY POWDER AND P R O P E R T I E S OF HOT P R E S S E D PRODUCTS

H_ Yamaguchi et al, (Tohoku Uni, J a p a n ) . Science Reports Tohoku Uni, Vol 36, No 1, 1991, 78-88. Powders of al-4at%Fe-l%Ce alloys, smaller t h a n 25 I~m were p r o d u c e d by high pressure gas atomization. The s u p e r s a t u r a t e d s t r u c t u r e was r e t a i n e d after h o t pressing at 440°C to a fully d e n s e condition. The Vicker's h a r d n e s s was r e p o r t e d to be 200 at room t e m p e r a t u r e a n d 140 at 300°C. The alloy a n d m e t h o d used are considered to be useful for p r o d u c t i o n of m a t e r i a l s w i t h good high t e m p e r a t u r e r e t e n t i o n of properties.

Copper E F F E C T S OF ADDITIVES ON S l N T E R E D P R O P E R T I E S OF COPPER COMPACTS

MA. Dombroski et al, (M-CAP Technology Int, "Wilmington, Delaware, USA). Int. J. Powder Metallurgy, Vol 28, No 1 1992 4151. A t t e n t i o n is drawn to t h e fact t h a t density gradients and corresponding variations in electrical conductivity exist in s i n t e r e d m a t e r i a l s a n d limit t h e use of Cu base materials for electrical applications. The source of t h e p r o b l e m is s t a t e d to arise from t h e r e d u c t i o n of occluded oxides by H a n d this may result in gas e n t r a p m e n t . The effect of additions of prealloyed Cu-A1 powder was investigated with reference to the ability of A1 to reduce t h e oxides a n d p r e v e n t gas e n t r a p m e n t . Sintered density, electrical conductivity a n d m i c r o s t r u c t u r e were d e t e r m i n e d . It was found t h a t t h e presence of A1 increased the density b u t reduced t h e conductivity a n d t h a t t h e c o m b i n e d effects of AI a n d Li s t e a r a t e was less t h a n either additive alone. PRODUCTION OF AMORPHOUS COPPER-TANTALUM POWDERS BY MECHANICAL ALLOYING

G. Veltl et al, ( F r a u n h o f e r Institut, Bremen, Germany), Metall, Vol 45, No 11, 1991, 1131-1133, (In G e r m a n ) .