Deformation kinetics of the Ti-6Al-4V alloy at low temperatures
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r e c e n t y e a r s the m e c h a n i c a l b e h a v i o r of unalloyed alpha (CPH) t i t a n i u m at t e m p e r a t u r e s below about 0.4 of the m e l t i n g t e m p e r a t u r e has b e e n studied e x t e n s i v e l y b y C o n r a d and his c o w o r k e r s , l-s A r e v i e w of the e a r l i e r work is p r e s e n t e d in Ref. 1, while m o r e r e c e n t s t u d i e s a r e found in Refs. 2 to 5. T h e s e s t u d i e s i n d i cate that the r a t e - c o n t r o l l i n g d i s l o c a t i o n m e c h a n i s m d u r i n g the low t e m p e r a t u r e d e f o r m a t i o n of alpha t i t a n i u m is t h e r m a l l y a c t i v a t e d o v e r c o m i n g of i n t e r s t i t i a l solute o b s t a c l e s by d i s l o c a t i o n s gliding on the f i r s t o r d e r p r i s m p l a n e s . Other s t u d i e s 6'7 on the d e f o r m a tion of an a i l - a l p h a (CPH) T i - 7 . 4 at. pct A1 alloy e s t a b l i s h e d that the d e f o r m a t i o n k i n e t i c s for this a l l o y a r e the s a m e as for unalloyed t i t a n i u m . This was also found to be the c a s e s for the data b y F r e d e r i c k and Hanna 8 on the c o m m e r c i a l a l l - a l p h a a l l o y T i - 5 A1-2.5 Sn. F u r t h e r m o r e , a n i n v e s t i g a t i o ns of the low t e m p e r a t u r e p l a s t i c flow of an a l l - b e t a (BCC) T i - 1 2 . 5 at. pct Mo a l l o y i n d i c a t e d that the r a t e - c o n t r o l l i n g m e c h a n i s m for this a l l o y is s i m i l a r to that of unalloyed t i t a n i u m . Hence, it a p p e a r s that i n t e r s t i t i a l s c o n t r o l the motion of d i s l o c a t i o n s in t i t a n i u m at low t e m p e r a t u r e s r e l a t i v e l y independent of s u b s t i t u t i o n a l s o l u t e s and of the crystal structure. Some of the i m p o r t a n t t e c h n o l o g i c a l alloys of t i t a n i um c o n s i s t of a m i x t u r e of the alpha (CPH) and the beta (BCC) p h a s e s . It is t h e r e f o r e d e s i r a b l e to c h a r a c t e r ize the d i s l o c a t i o n m e c h a n i s m ( s ) and r a t e - c o n t r o l l i n g i n t e r a c t i o n ( s ) in such c a s e s . Hence, this is the o b j e c tive of the p r e s e n t i n v e s t i g a t i o n . Special a t t e n t i o n is given to a s c e r t a i n i n g whether or not the r a t e - c o n t r o l ling d i s l o c a t i o n m e c h a n i s m for p l a s t i c flow in such a l loys is also the t h e r m a l l y a c t i v a t e d o v e r c o m i n g of i n t e r s t i t i a l solute o b s t a c l e s . The a +~ a l l o y c h o s e n for this study was T i - 6 A1-4 V b e c a u s e of its c o m m e r c i a l importance. B. de MEESTER is a former Graduate Student, Metallurgical Engineering and Materials Science Department, University of Kentucky. M, DONER, formerly Research Associate, Metallurgical Engineering and Materials Science Department, University of Kentucky, is now Senior Research Engineer, General Motors Corp., Indianapolis, Ind. 46206. H. CONRAD is Professor and Chairman,
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