Plastic deformation of titanium at elevated temperatures
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AND W. A. BACKOFEN
The d e f o r m a t i o n of iodide t i t a n i u m s i n g l e c r y s t a l s c o n t a i n i n g 200 to 250 ppm O, was s t u d i e d in c o m p r e s s i o n at t e m p e r a t u r e s f r o m 25 ~ to 800~ Reduction of about 5 pct along the c axis was a c c o m m o d a t e d a l m o s t e n t i r e l y by {1122} t w i n n i n g f r o m 25 ~ to 300~ and above 400~ by {10il} t w i n n i n g in c o m b i n a t i o n with c + a slip. The s t r e s s for {1152} twinning i n c r e a s e d with i n c r e a s i n g t e m p e r a t u r e , and twin f o r m a t i o n was a c c o m p a n i e d b y a load drop, while the s t r e s s for {10il} t w i n n i n g d e c r e a s e d with i n c r e a s i n g t e m p e r a t u r e and twinning was not a c c o m p a n i e d by a load drop. C r y s t a l s r e d u c e d n o r m a l to the c axis d e f o r m e d by a c o m b i n a t i o n of p r i s m slip and {10i2} twinnir,g at 25~ and by p r i s m slip alone above 500~ T H E p l a s t i c a n i s o t r o p y of p o l y c r y s t a l l i n e hop m e t a l s is a r e f l e c t i o n of w e l l - d e v e l o p e d d e f o r m a t i o n t e x t u r e s . The t e x t u r e s , in t u r n , r e s u l t f r o m the l i m i t e d n u m b e r of slip s y s t e m s and the o p e r a t i o n of twinning as a p r o m i n e n t d e f o r m a t i o n m e c h a n i s m . To u n d e r s t a n d t e x t u r e d e v e l o p m e n t and a n i s o t r o p y in any detail r e q u i r e s i n f o r m a t i o n about the v a r i o u s s h e a r p r o c e s s e s c o n t r i b u t i n g to d e f o r m a t i o n at d i f f e r e n t t e m p e r a t u r e s . This p a p e r d e s c r i b e s the r e s u l t s of a s y s t e m a t i c q u a n t i t a t i v e i n v e s t i g a t i o n of t h e s e s h e a r p r o c e s s e s . At r o o m t e m p e r a t u r e and below, t i t a n i u m s l i p s along (1120) on {1010}, (0001) and {1011} p l a n e s ~ by the m o t i o n of 1/3(1120), o r a d i s l o c a t i o n s . A change in length along the c a x i s is not p o s s i b l e with (1120) slip alone, but r e q u i r e s a slip d i r e c t i o n lying out of the b a s a l plane. Such slip h a s not been o b s e r v e d in high p u r i t y t i t a n i u m , but has b e e n r e p o r t e d in c o m m e r c i a l l y p u r e t i t a n i u m and in Ti-A1 a l l o y s 2,a to r e s u l t f r o m the motion of 1/3(1123), or c + a d i s l o c a t i o n s . Slip along (1123) has also been r e p o r t e d in c a d m i u m a and zinc 4 at r o o m t e m p e r a t u r e , and in b e r y l l i u m at elevated t e m p e r a t u r e . 5-~ A length change along the c axis can also be a c c o m p l i s h e d by twinning. In t i t a n i u m , {10i2}, {1121}, and {1123} t w i n s allow an e x t e n s i o n along the c axis, while {1122}, {11~.4},a'9 and {10il} ~~twins p e r m i t a r e d u c t i o n . Twinning g e n e r a l l y b e c o m e s l e s s i m p o r t a n t as t e m p e r a t u r e i n c r e a s e s . In t i t a n i u m , Rosi et al. a o b s e r v e d n
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