Mechanical-thermal processing of a beta-titanium alloy
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Mechanical-Thermal Processing of a Beta-Titanium Alloy 9 N E D W. P O L A N A N D D O N A L D H. A V E R Y An i n v e s t i g a t i o n of m e c h a n i c a l - t h e r m a l p r o c e s s i n g of the B - t i t a n i u m alloy, TS6, (Ti: 10 pet Cr, 7 pct V, 3.5 pet Mo, 3 pct A1) h a s b e e n r e c e n t l y r e p o r t e d . 1 The o b s e r v a t i o n s of d r a m a t i c a l l y enhanced s t r e n g t h with the r e t e n t i o n of ductility w e r e a t t r i b u t e d to the f o r m a tion of a v e r y dense d i s l o c a t i o n s u b s t r u c t u r e through heavy cold d e f o r m a t i o n of the m e t a s t a b l e /3 followed by p r e c i p i t a t i o n of a finely d i s p e r s e d second phase d u r i n g l o w - t e m p e r a t u r e aging. In this c o m m u n i c a t i o n we p r e s e n t the r e s u l t s of c o n t i n u i n g r e s e a r c h on TS6 with the i n v e s t i g a t i o n of additional m e c h a n i c a l p r o p e r t i e s . S e v e r a l 500 g ingots of TS6 w e r e p r e p a r e d by t r i p l e v a c u u m arc m e l t i n g . T h e s e w e r e hot forged in a i r , NED W. POLAN is Senior Engineer, WestinghouseElectric Corp., Bettis Atomic Power Laboratory, West Mifflin, PA 15122. DONALD H. AVERY is Professor of Engineering,Brown University,Providence, RI 02912, where Ned W. Polan was formerly Research Associate. Manuscript submitted September 27, 1974. METALLURGICALTRANSACTIONSA
m a c h i n e d to 1.3 c m diam rods, solution t r e a t e d 1 h in vacuo at 850~C and w a t e r quenched, y i e l d i n g a m e t a s t a b l e a11-/3 alloy of about 100 to 150 tx g r a i n s i z e . After swaging or d r a w i n g to a s t r a i n of 0.4 to 0.5, a s t r o n g bee [110] f i b e r t e x t u r e develops, r e s u l t i n g in a slip s y s t e m o r i e n t a t i o n in which continued d e f o r m a t i o n i s a c c o m p l i s h e d in plane s t r a i n r a t h e r than axially s y m m e t r i c flow of i n d i v i d u a l g r a i n s . As in other bcc m a t e r i a l s , c o m p a t i b i l i t y of a d j a c e n t g r a i n s i s m a i n t a i n e d by b e n d i n g of g r a i n s about each o t h e r , z C o n t i n ued r e d u c t i o n f u r t h e r r e f i n e s the s t r u c t u r e . T h i s d e f o r m a t i o n b e h a v i o r has also b e e n o b s e r v e d in heavily d r a w n tungsten, i r o n and niobium, 3 ' 4 T e n s i l e t e s t s w e r e p e r f o r m e d on m a t e r i a l swaged to v a r i o u s r e d u c t i o n s (with i n t e r m e d i a t e a n n e a l s c h o s e n to p r o d u c e s p e c i m e n s a l l of the s a m e finished d i a m e t e r , e l i m i n a t i n g any p o t e n t i a l size effect), t e s t e d both as swaged and after aging at 425~ for 8 h. Yield and f r a c t u r e s t r e n g t h s a r e plotted as f u n c t i o n s of e e/2 in F i g s , l ( a ) and l ( b ) , c o n f i r m i n g the p r e v i o u s r e s u l t s , 1 (The g e o m e t r i c r e d u c t i o n of c e l l size m o d e l / % , - % y ec 1/d */~, p r e d i c t s C r y - a o y cc
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