Rolling texture of Pu-Ga alloys as a function of temperature
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and h o m o g e n i z e d a l l o y s i n c r e a s e s with the g a l l i u m c o n c e n t r a t i o n , no change in r o l l i n g t e x t u r e was o b s e r v e d a s a function of g a l l i u m for s p e c i m e n s r o l l e d at r o o m t e m p e r a t u r e . R o l l i n g of t h e s e a l l o y s at t e m p e r a t u r e s down to -196~ c a u s e d a t e x t u r e t r a n s i t i o n s i m i l a r to that o b s e r v e d in copper r o l l e d at low t e m p e r a t u r e s . The stacking fault e n e r g y was e s t i m a t e d to be 30 e r g p e r sq c m . F o r the P u - 3 . 4 at. pct Ga alloy, t h i s t e x t u r e t r a n s i t i o n occ u r r e d at a h i g h e r t e m p e r a t u r e than in the o t h e r two a l l o y s , and it i s known that in this c a s e s o m e a p h a s e was f o r m e d d u r i n g r o l l i n g .
PREVOUS
work 1 has shown the r o o m t e m p e r a t u r e r o l l i n g t e x t u r e of P u - 3 . 4 at. pct Ga to develop quite s i m i l a r l y to that of c o p p e r . The m a i n d i f f e r e n c e s w e r e a n e x a g g e r a t e d 'fl3utterfly" effect in c e r t a i n r e g i o n s ( d e s c r i b e d l a t e r in t h i s work) and an o v e r a l l lower i n t e n s i t y l e v e l , e s p e c i a l l y noted for the (111) poles. Upon i n c r e a s i n g the g a l l i u m c o n c e n t r a t i o n f r o m 3.4 to 6.5 at. pct, the n u m b e r of t w i n s o b s e r v e d in the h o m o g e n i z e d s t r u c t u r e w a s s i g n i f i c a n t l y g r e a t e r . 2 T h i s obs e r v a t i o n s u g g e s t s that the fcc P u - G a a l l o y s might have a c o m p a r a t i v e l y low s t a c k i n g fault e n e r g y (SFE), which might d e c r e a s e a s the g a l l i u m c o n c e n t r a t i o n is i n c r e a s e d , allowing a change in r o l l i n g t e x t u r e , a s in the case of copper a l l o y s , or a s the r o l l i n g t e m p e r a t u r e i s d e c r e a s e d , a s in the case of p u r e c o p p e r . B e c a u s e of the m a n y d i f f i c u l t i e s a s s o c i a t e d with u s i n g a n n e a l i n g twin d e n s i t i e s to e s t i m a t e SFE, no v a l u e s w e r e o b t a i n e d by t h i s method. F o r c e r t a i n c o m p o s i t i o n s in t h i s a l l o y s y s t e m , t h e r e e x i s t s the p o s s i b i l i t y of t r a n s f o r m i n g the fcc 5 p h a s e to the b r i t t l e m o n o c l i n i c a p h a s e at low t e m p e r a t u r e s and u n d e r p r e s s u r e . T h e p u b l i s h e d p h a s e d i a g r a m 3 s h o w s the fcc p h a s e to be s t a b l e at r o o m t e m p e r a t u r e f r o m a p p r o x i m a t e l y 2 at. pct Ga to 8.5 at. pct Ga. Howe v e r , it has b e e n shown that the P u - 2 at. pct Ga alloy i s not s t a b l e u n d e r p r e s s u r e at r o o m t e m p e r a t u r e , and will t r a n s f o r m to the a phase.4 The P u - 3 . 4 at. pct Ga a l l o y r e p o r t e d p r e v i o u s l y 1 was chosen b e c a u s e it r e m a i n e d s t a b l e u n d e r the p r e s s u r e e n c o u n t e r e
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