Factors controlling the strength and ductility of high purity beryllium block
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r e s u l t s to be d e s c r i b e d h e r e a r e p a r t of a continuing e f f o r t at Lockheed M i s s i l e s and Space C o m pany, Inc. to i m p r o v e the m e c h a n i c a l p r o p e r t i e s of b e r y l l i u m . The Influence of p u r i t y and p r o c e s s i n g upon the BeO d i s p e r s i o n s and the r e c r y s t a l l i z a t i o n b e h a v i o r of b e r y l l i u m b l o c k s has b e e n p r e v i o u s l y d i s c u s s e d . 1'2 It was found the I n c r e a s i n g p u r i t y and d e c r e a s i n g hot p r e s s i n g t e m p e r a t u r e r e s u l t e d in d i s p e r s i o n s of BeO with f i n e r p a r t i c l e s i z e . This was r e f l e c t e d a l s o in a l a r g e I n c r e a s e of the r e c r y s t a l l l z a tton t e m p e r a t u r e of the m a t e r i a l which a l l o w e d the u s e of high t e m p e r a t u r e a n n e a l i n g t r e a t m e n t s without m o d i f y i n g the g r a i n s i z e of the b l o c k s . This w o r k d e s c r i b e s the influence of oxide d i s p e r s i o n s and p r o c e s s i n g on the d u c t i l i t y of b e r y l l i u m . T h e s e p a r a m e t e r s a r e r e s p o n s i b l e f o r the a p p a r e n t l y a n o m a l o u s b e h a v i o r of the m a t e r i a l w h e r e g r a i n r e f i n e m e n t and i n c r e a s e d p u r i t y p r o d u c e r e d u c e d d u c t i l ity. I. MATERIALS The m a t e r i a l s used in this i n v e s t i g a t i o n w e r e p r o duced b y hot l s o s t a t t c p r e s s i n g (HIP) at 1675~ (1176 K) under a p r e s s u r e of 15 k s f (103.5 M N / m z) and s t r e s s r e l i e v e d at 1475~ (1075 K) f o r 2 h. Two p o w d e r p u r i t i e s w e r e used, PJ 10 f o r m e d f r o m c o m m e r c i a l p u r i t y m a g n e s i u m r e d u c e d b e a d and P - 1 f r o m Kawecki B e r y l c o I n d u s t r i e s ' e l e c t r o l y t i c flake. In both the above p o w d e r s the i n i t i a l p a r t i c l e s i z e was m i n u s 325 m e s h (< 44 ~tm). With the a i m of p r o d u c i n g f i n e r g r a i n s i z e s , a b l o c k (RR243) was m a d e with P - 1 p o w d e r that had b e e n r o t a r y b a l l m i l l e d and a i r c l a s s i f i e d to obtain a n o m i n a l < 20/~m m a t e r i a l and s i m u l t a n e o u s l y r e m o v e the s u b m i c r o n p a r t i c l e s which c o n t a i n m o s t of the i m p u r i t i e s . The c o m p o s i t i o n of t h i s b l o c k was a l s o m o d i fied by an i r o n addition. The o r i g i n a l P - 1 and P-10 p o w d e r s w e r e f o r m e d Into t u b e s 16 c m o u t s i d e diana b y 18 c m long with a 1.9 c m t h i c k wall. The RR243 lot was a s o l i d b l o c k 14.5 c m d i a m and 14.5 c m long. The c o m p o s i t i o n of the t h r e e b l o c k s is given in Table I. D. WEBSTER is Research Scientist at the Material and Composites Laboratory of Lockheed Missilesand Space Co., Inc., Palo Alto, Calif. 94304. R. L. GREENE and R. W. LAWLEY are Research Specialist and Senior Research Engineer, respectively, in th
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