Deformation of a precipitation-hardenable Cr-Cu sintered powder composite
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Deformation of a Precipitation-Hardenable Cr-Cu Sintered Powder Composite G.
G A R M O N G AND
L.A.
S H E P A R D
S O M E past w o r k ~'~ o n s i n t e r e d t u n g s t e n - b a s e d c o m p o s i t e s h a s d e a l t w i t h the i n f l u e n c e of the m a t r i x o n the d e f o r m a t i o n p r o c e s s . T w o e x p e r i m e n t a l t e c h n i q u e s u s e d to s t u d y m a t r i x p e r f o r m a n c e a r e the v a r i a t i o n of m a t r i x m e a n f r e e p a t hI a n d the a d d i t i o n of a l l o y i n g elem e n t s to the m a t r i x . 2 In the p r e s e n t w o r k a t h i r d m e a n s of v a r y i n g m a t r i x s t r e n g t h is d e s c r i b e d : t h e c o p p e r - r i c h m a t r i x of a C r - C u l i q u i d - p h a s e s i n t e r e d c o m p o s i t e is f o u n d to b e h e a t - t r e a t a b l e to v a r i o u s s t r e n g t h s , t h e r e b y a f f o r d i n g the i n v e s t i g a t o r a m e a n s of c h a n g i n g the m a t r i x p r o p e r t i e s in situ. W i t h this t e c h n i q u e , the e f f e c t of m a t r i x s t r e n g t h o n m e c h a n i c a l p r o p e r t i e s m a y b e e v a l u a t e d for g e o m e t r i c a l l y c o m p a r a b l e sintered composites. Starting materials were Universal M i n e r a l s and M e t a t s V M 1 7 0 - 9 0 - i 4 ~ c o p p e r p o w d e r of 99.7 pct purity and U n i o n C a r b i d e -325 m e s h E l c h r o m e L G c h r o m i u m p o w d e r of 99.8 pct p u r i t y . A l e n g t h of O F H C c o p p e r t u b i n g w a s filled w i t h a m i x t u r e of 6 0 pct b y w e i g h t c h r o m i u m p o w d e r a n d 4 0 pct b y w e i g h t c o p p e r p o w d e r , c l o s e d b y c o p p e r p l u g s , a n d s w a g e d to g i v e a r e d u c t i o n in i n s i d e c r o s s - s e c t i o n a l a r e a of 35.2 pct. T h e a s - s w a g e d s p e c i m e n s w i t h the j a c k e t s in p l a c e w e r e s i n t e r e d in p u r i f i e d d r y h y d r o g e n in a c y c l e c o n 1 s i s t i n g of a ~- h r r e d u c i n g t r e a t m e n t at 4 2 5 ° C , a 3 h r liquid-phase s i n t e r i n g at 1 4 1 0 ° C , a 2 h r c o o l i n g to 1 0 4 0 ° C , a n d e i t h e r f u r n a c e c o o l i n g to r o o m t e m p e r a t u r e o r a q u e n c h into w a t e r . A g i n g t r e a t m e n t s w e r e a t 4 7 5 ° C f o r t i m e s o f 15 t o 240 m i n in a r g o n . T h e a s s i n t e r e d composites consisted of continuously conn e c t e d , n e a r l y s p h e r i c a l c h r o m i u m p a r t i c l e s in a c o p perLrich m a t r i x , with s o m e inclusions. Metallographic e x a m i n a t i o n s h o w e d t h e s p e c i m e n s t o be a b o u t 99 p c t d e n s e . T h e v o l u m e fractions o f p h a s e s p r e s e n t were 57.6 p c t C r p a r t i c l e s , 40.8 p c t c o p p e r - r i c h m a t r i x , a n d 1.6 p c t r o u n d e d C r 2 O a i n c l u s i o n s l o c a t e d a t p a r t i c l e m a t r i x i n t e r f a c e s . T e n s i l e s p e c i m e n s of gage d i a m 0.1
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