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1. P. J. Foplano,M. B. Bever,and B. L. Averbach:Trans. Quart.ASM, 1969,vol. 62, p. 324. 2. P. J. Foplanoand C. F. Hickey,Jr.: TheScience, Technology, and Applications of Titanium, p. 793, PergamonPress, 1969. 3. J. Moulin,R. Molinier,and R. Syre: TheScience, Technology, and Applications of Titanium, PergamonPress, 1969. 4. L. D. Jaffe. AIME Trans., 1955, vol. 203,pp. 1241-44.

--a' (martensite)--~ +~ - - ~ (Widmanstaetten) + Since the h a r d n e s s v a l u e s of the a s - q u e n c h e d s p e c i m e n continue to i n c r e a s e up to the -~ to ~ - i n . d i s t a n c e , the a ' t r a n s f o r m a t i o n m e c h a n i s m p r e d o m i n a t e s up to this d i s t a n c e . Beyond the -~-in. d i s t a n c e , the h a r d n e s s v a l u e s in the a s - q u e n c h e d b a r d e c r e a s e and the a m o u n t of W - - a i n c r e a s e s u n t i l it p r e d o m i n a t e s at the 1- to 1 89 d i s t a n c e , Fig. 2(c). In the J o m i n y b a r aged at 900~ the h a r d n e s s v a l u e s also d e c r e a s e beyond ~ in. Since 3 hr a t 900~ p r o d u c e s m a x i m u m h a r d e n i n g without o v e r a g i n g , these h a r d n e s s data also suggest that the amount of W---~ is i n c r e a s i n g c o n t i n u o u s l y b e y o n d the -~-ln. d i s t a n c e . While our J o m i n y data a r e s i m i l a r to those p r e s e n t e d by Moulin et a l . 3 at the I n t e r n a t i o n a l C o n f e r ence on T i t a n i u m in London in 1968, we differ in the m i c r o s t r u c t u r a l i n t e r p r e t a t i o n s . Moulin et a l . state that the ~ phase is r e t a i n e d d u r i n g the quench up to a d i s t a n c e of 10 m m (-~ in.) from the quenched end of the J o m i n y b a r . B a s e d upon X - r a y and m i c r o s t r u c r u r a l o b s e r v a t i o n s , we conclude that v e r y little /3 is r e t a i n e d d u r i n g the quench and that the ~ phase t r a n s f o r m s e s s e n t i a l l y c o m p l e t e l y to m a r t e n s i t i c a ' at the quenched end. T h e s e a u t h o r s also suggest that the p r e c i p i t a t i o n of w a c c o u n t s for the i n c r e a s e i n h a r d n e s s between 10 and 30 m m (-~ to 1~ in.). T h e r e is no evidence in the open l i t e r a t u r e for the f o r m a t i o n of w in this alloy for the heat t r e a t m e n t p r o c e d u r e s they u s e d (solution t r e a t e d at 1580~ and aged at 1076~ F i n a l l y , Moulin et al. contend that the /3 phase t r a n s f o r m s m a r t e n s i t i c a l l y to ol' in the r a n g e f r o m 30 to S0 m m (1-~ to 2 in.) w h e r e we feel that W - - a is the p r e d o m i n a n t s t r u c t u r e at a distance of 1~ in. f r o m the quenched end. In s u m m a r y , there a r e two competing r e a c t i o n s which occur in this alloy d u r i n g the J o m i n y quench. The /3 phase at e q u i l i b r i u m at the solution t e m p e r a t u r e e i t h e r t r a n s f o r m s to m a r t e n s i t i c a ' or to Widm a n s t a e t t e n a d u r i n g the quench. The m a r t e n s i t i c a ' r e a c t