Creep properties of PM aluminium alloys SiC reinforced composite

Creep properties of PM aluminium alloys SiC reinforced composite

The effect of Cr on t h e m i c r o s t r u c t u r e a n d properties of RS processed A1-Cr-Mn alloys h a s been investigated by differential scannin...

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The effect of Cr on t h e m i c r o s t r u c t u r e a n d properties of RS processed A1-Cr-Mn alloys h a s been investigated by differential scanning calorimetry (DSC), microh a r d n e s s m e a s u r e m e n t , X-ray diffraction (XRD) and analytical transmission electron microscopy (ATEM). Increase in t h e Cr c o n t e n t of t h e alloy Al-5wt%Mn2.5wt% Cr resulted in loss of s u p e r s a t u r a t i o n during RS a n d extensive p r e c i p i t a t i o n of the 0 phase, Al13Cr 2. The aging p h e n o m e n a were studied a n d A16Mn w a s o b s e r v e d . T h e RS p o w d e r s w e r e consolidated by extrusion. Increase of Cr c o n t e n t increased t h e strength. The highest ductility was n o t e d in t h e alloy A1-5Mn2.5Cr in which A112(Cr,Mn) p r e c i p i t a t e d during extrusion. OXIDATION A N D SURFACE S E G R E G A T I O N IN RAPIDLY S O L I D I F I E D ( R S ) A1 ALLOY POWDERS T~I. Carney, et al, (Dept. of Materials, University of Surrey, Guildford, UK), Int. J. Rapid Solidification, Vol.5, 1990, 189217. Oxide film t h i c k n e s s a n d solute e l e m e n t s e g r e g a t i o n i n RS Al a l l o y p o w d e r s containing a d d i t i o n s of Cr, Cu, Fe, Hf, Li, Mg, Zn a n d Zr, singly, was studied by X-ray p h o t o e l e c t r o n s p e c t r o s c o p y (XPS). The powders were m a d e by high pressure gas a t o m i z a t i o n w i t h He. T h e m e t h o d of m e a s u r i n g oxide film thickness by XPS is described. Very t h i n films, 0.7-2 nm, were always present. Solute e l e m e n t d i s t r i b u t i o n i n t h e A1 w a s i n v e s t i g a t e d . S u r f a c e segregation h a s been quantified by t h e use of a n e n r i c h m e n t factor. Good a g r e e m e n t was found between t h e e n r i c h m e n t factor a n d t h e solute diffusion rates in liquid A1.

D E V E L O P M E N T OF NEAR-NET SHAPE C O M P O N E N T S IN PM P R O D U C E D LIGHT METAL BASED MMC H. Cohrt, U. Muller ( S c h u n k Sintermetalltechnik GmbH, Giessen, Germany), P o w d e r Metallurgy International, Vol.22, No.6, 1990, 43-46. In German. The d e v e l o p m e n t of a process for t h e p r o d u c t i o n of PM A1 b a s e d MMC is described. E m p h a s i s is p l a c e d o n t h e p r o d u c t i o n of n e a r - n e t - s h a p e p a r t s for use in automotive applications. The p h e n o m e n a occurring d u r i n g p r o d u c t i o n of light m e t a l b a s e d MMCs are discussed.

STUDY OF RAPIDLY S O L I D I F I E D ( R S ) A1-Si ALLOY POWDER MADE BY CENTRIFUGAL ATOMIZATION Y. Xianjin, et al, (Tianjin University, China), Powder Metallurgy Technology, Vol.8, No.4, 1990, 206-12. In Chinese. The technological parameters i n f l u e n c i n g p a r t i c l e s h a p e a n d size

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d i s t r i b u t i o n of RS A1-Si alloy powders, m a d e by c e n t r i f u g a l a t o m i z a t i o n , h a v e been investigated. Temperature at the atomizer nozzle a n d disk r o t a t i o n speed were found to have significant effect on particle s h a p e a n d size distribution. A t e m p e r a t u r e of 780°C a n d a r o t a t i o n speed of 36 000 r p m was found to give regularly s h a p e d particles a n d a more even d i s t r i b u t i o n of solid s o l u t i o n a n d fine eutectic in t h e m i c r o s t r u c t u r e t h a n o t h e r conditions. The Si c o n c e n t r a t i o n in t h e solid solution increases with decrease in the particle size a n d increase in t h e cooling rate.

PREVENTION OF COMPACT SWELLING D U R I N G LIQUID PHASE S I N T E R I N G OF A1-Cu ALLOYS

MECHANICAL P R O P E R T I E S OF PM AI ALLOYS R E I N F O R C E D WITH SiC WHISKERS

A G I N G E F F E C T S ON T H E WEAR BEHAVIOUR OF PM SiC R E I N F O R C E D ALUMINIUM ALLOYS

I. Imazu, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol.37, No.7, 1990, 987-

Y.M. Pan, et al, (Northwestern University, Evanston, USA), Scripta MetaUurgica & Materialia, Vol.24, No.7, 1990, 1341-1345. The wear b e h a v i o u r of a PM 2124 A1 alloy reinforced w i t h 20vo1% S i C particulates of average size 17 ~ m was i n v e s t i g a t e d by m e a n s of block-on-ring tests. The m a t e r i a l h a d b e e n extruded, solution treated and was aged under different conditions. The tests were carried o u t u n d e r a load of 168 N a n d a sliding speed of 2 m / s with a m i n e r a l oil lubricant. Wear was assessed by weight loss a n d t h e worn surfaces were e x a m i n e d by s c a n n i n g electron microscopy. Wear of t h e steel disk was measured by surface profile measurements.

990. In Japanese. The effects of whisker d i a m e t e r a n d s t r e n g t h of t h e b o n d between m a t r i x a n d reinforcement on t h e mechanical properties of PM SiC whisker reinforced A1 alloys were investigated. For whiskers 1.1 I~m a n d 0.5 ~tm in d i a m e t e r little difference in properties of t h e composite was found. Where t h e fibres were coated with C, p r i o r to fabrication, t h e m a t r i x / w h i s k e r s t r e n g t h was reduced a n d t h e tensile s t r e n g t h was lower.

FATIGUE S T R E N G T H OF PM AI ALLOY R E I N F O R C E D WITH SiC F I B R E S H. Sunada, et al, J. Japan Soc. Powder and Powder Metallurgy, Vol. 37, No.7, 1990, 991-994. In Japanese. W o h l e r f a t i g u e t e s t s w e r e u s e d to m e a s u r e t h e fatigue p r o p e r t i e s of SiC r e i n f o r c e d A1 alloys f a b r i c a t e d by PM. I n c r e a s e in t h e c o n c e n t r a t i o n of fibre r e i n f o r c e m e n t w a s f o u n d to i n c r e a s e fatigue a n d t e n s i l e s t r e n g t h s a t r o o m temperature. Increased temperature reduced t h e tensile strength.

RAPIDLY S O L I D I F I E D ( R S ) A1 ALLOYS K. Shibue, ( S u m i t o m o Light Metal Industries, J a p a n ) , J. Japan Inst. Light Metals, Vol.39, No.l 1, 1989, 850-862. In Japanese. The characteristics of RS are reviewed with regard to the process and the properties of t h e products. The various m e t h o d s of RS p o w d e r m a k i n g a r e considered. It is n o t e d t h a t t h e solubilities of alloy e l e m e n t s increase in RS A1 a n d t h a t it is p o s s i b l e for RS to give rise to a m o r p h o u s alloys. By t h e u s e of RS powders it h a s been possible to develop materials w i t h high strength, low density, high elasticity a n d good h e a t a n d a b r a s i o n resistance.

A.P. Savitskii, G.N. Romanov, ( S i b e r i a n B r a n c h , USSR A c a d e m y of S c i e n c e s , T o m s k , U S S R ) , Science of Sintering, Vol.22, No.2, 1990, 73-77. The p a p e r shows t h a t t h e s h r i n k a g e observed d u r i n g t h e liquid p h a s e sintering of diffusionally interacting Cu-A1 alloys can be associated w i t h t h e generation of t h e liquid phase. It is f u r t h e r shown t h a t this can be used to s u p p r e s s t h e swelling usually observed a t t h i s stage of t h e s i n t e r i n g process.

C R E E P P R O P E R T I E S OF PM ALUMINIUM ALLOYS SiC R E I N F O R C E D COMPOSITE A_B. Pandey, et al, (Defence Metallurgical L a b o r a t o r y , H y d e r a b a d , I n d i a ) , Scripta Metallurgica & Materialia, Vol.24, No.8, 1990, 1565-1570. The t e n s i l e a n d c o m p r e s s i v e c r e e p b e h a v i o u r of a n A1 alloy reinforced with 10%vol of SiC particles was studied. Steady s t a t e creep h a s b e e n analysed with regard to t h e operative m e c h a n i s m s . The creep fracture aspect a n d t h e role of cavitation are discussed. METALLOGRAPHY OF A N AI-Mg ALLOY D I S P E R S I O N S T R E N G T H E N E D WITH ALUMINIUM CARBIDE A. Orlova, et al, (Czechoslovak Academy of Sciences, Brno, Czechoslovakia), Practical Metallography, No.10, 1990, 514-523. In G e r m a n a n d English. The d e v e l o p m e n t of m e t a l l o g r a p h i c techniques for the examination of d i s p e r s i o n s t r e n g t h e n e d m a t e r i a l s is described. Mechanical alloying was used to produce A1-Mg alloys s t r e n g t h e n e d by t h e presence of A14Ca a n d Al2Oa. The powders were consolidated by e x t r u s i o n a n d HIP.