Kinetics of the phase transformation in a Ti-15Mo-5Zr-3AI alloy as studied by X-ray diffraction
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u l t i m a t e t e n s i l e s t r e n g t h of B o r s i c / T i b a s e a l l o y c o m p o s i t e s i s a d v e r s e l y a f f e c t e d by i n t e r f a c e r e a c t i o n s at temperatures above 650°C. This t h e r m a l degradation correlates with the formation of s i l i c i d e s o r b o r i d e s a t t h e f i l a m e n t / m a t r i x i n t e r f a c e . It h a s b e e n s u g g e s t e d that t h e p r o p e r a l l o y a d d i t i o n s t o t h e T i b a s e m a t r i x m i g h t r e d u c e the r e a c t i o n r a t e t o a t o l e r a b l e l e v e l . T h e e l e m e n t s A1, M o , Z r a n d V r e d u c e t h e r e a c t i o n r a t e i n t h e o r d e r g i v e n1 w i t h A1 b e ing l e a s t effective and V most effective. When more than o n e of t h e s e e l e m e n t s i s p r e s e n t , t h e i r i n f l u e n c e is a p p r o x i m a t e l y additive. A n a l l o y c o n t a i n i n g T i 1 5 M o - 5 Z r - 3 A 1 w a s d e v e l o p e d by K o b e S t e e l , L t d . * a s *This was supplied by Kobe Steel, Ltd., 3-18, I Chome, Wakinohama-Cho, Fukiai-Ku, Kobe, Japan. a p o t e n t i a l c o m m e r c i a l ; 3 - a l l o y . S i n c e it c o n t a i n s t h e d e s i r e d e l e m e n t s w h i c h r e d u c e the i n t e r r a c i a l r e a c t i o n r a t e a n d i t w a s r e p o r t e d that t h e a l l o y h a s e x c e l l e n t f o r m a b i l i t y , high s t r e n g t h a n d weldability,2 it bec a m e a logical candidate as a m a t r i x material. Very l i t t l e d a t a w e r e a v a i l a b l e o n t h e t h e r m a l s t a b i l i t y of this metastable fl-alloy. Consequently, X - r a y s t u d i e s were i n i t i a t e d to d e t e r m i n e t i m e - t e m p e r a t u r e - t r a n s f o r m a t i o n c u r v e s . T h e s e d a t a a i d e d in t h e f a b r i c a t i o n of c o m p o s i t e p a n e l s a n d i n the u n d e r s t a n d i n g o f c h a n g e s in m e c h a n i c a l p r o p e r t i e s a f t e r t h e r m a l t r e a t ment. T h e p u r p o s e o f t h i s p a p e r is t o m a k e t h e T - T - T diagram generally available a n d to d e s c r i b e t h e X - r a y m e t h o d s u s e d t o d e t e r m i n e t h e f r a c t i o n of t r a n s f o r m e d p h a s e . T h e s h e e t m a t e r i a l u s e d f o r t h i s s t u d y w a s not i d e a l f o r a n X - r a y s t u d y b e c a u s e of b o t h a r o i l i n g a n d a n n e a l i n g t e x t u r e a s well as g r a i n size p r o b l e m s . T h e s e difficulties were o v e r c o m e u s i n g s p e c i a l techn i q u e s a n d a r e d e s c r i b e d in a two p a p e r sequence. T h e f i r s t t e c h n i q u e m a k e s u s e o f a r a t i o of i n t e g r a t e d i n tensities a n d p r e s e n t s systematic T - T - T d a t a while t h e s e c o n dp a p e r d e s c r i b e s an approach b a s e d upon the u s e of i n c o m p l e t e p o l e f i g u r e d a t a . T h i s l a t t e r a p p r o a c h p r o v i d e s a r e l i a b l e c h e c k o n the f i r s t w h i c h i s approximate
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