The titanium-rich end of the Ti-Cd phase diagram

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EXPERIMENTAL The m a t e r i a l s used w e r e c a d m i u m shot which was 99.999 pct p u r e and c o m m e r c i a l l y p u r e t i t a n i u m in the f o r m of s h e e t 0.025 cm thick. The b o i l i n g point of c a d m i u m is 765~ which is well below the m e l t i n g point of t i t a n i u m , 1668~ T h e r e f o r e it is not p o s s i b l e to f o r m alloys by the c o n v e n t i o n a l method of m e l t i n g the 2 m e t a l s t o g e t h e r . Alloys w e r e p r e p a r e d by diffusing c a d m i u m into the solid t i t a n i u m f r o m the vapor p h a s e . Weighed a m o u n t s of c a d m i u m and t i t a n i u m (total weight about 1.5 g) w e r e s e a l e d in evacuated q u a r t z c a p s u l e s and heated for p e r i o d s of 24 to 48 hr in the t e m p e r a t u r e r a n g e of 1000 ~ to 1050 ~ D u r i n g heating p a r t of the c a d m i u m d i s s o l v e d in the t i t a n i u m , while the r e m a i n d e r was p r e s e n t in the vapor p h a s e . On c o o l ing this vapor c o n d e n s e d to s m a l l g l o b u l e s , d e p o s i t i n g on the alloy and v a r i o u s p a r t s of the q u a r t z c a p s u l e . B e c a u s e of this c o n d e n s a t i o n , the p o s t - h e a t i n g weights of alloy and c a d m i u m could be u s e d only for a v e r y a p p r o x i m a t e e s t i m a t e of alloy c o m p o s i t i o n . P o r t i o n s of these s a m p l e s w e r e r e s e a l e d u n d e r v a c u u m in q u a r t z and heated at v a r i o u s lower t e m p e r a t u r e s for p e r i o d s s u f f i c i e n t to obtain the e q u i l i b r i u m p h a s e s at these t e m p e r a t u r e s , and then quenched to r o o m t e m p e r a t u r e . V a r i o u s a n n e a l i n g t i m e s v a r y i n g f r o m 1 hr to 48 hr

w e r e used; the phase r e l a t i o n s w e r e i n d e p e n d e n t of a n n e a l i n g time for p e r i o d s l o n g e r than about 2 h r . The s a m p l e s w e r e e x a m i n e d m e t a l l o g r a p h i c a l l y to d e t e r m i n e the p h a s e s that had b e e n p r e s e n t at the a n n e a l i n g t e m p e r a t u r e . Some s a m p l e s w e r e e x a m i n e d by s t a n d a r d X - r a y powder methods to obtain d i f f r a c t i o n p a t t e r n s of the p h a s e s p r e s e n t after q u e n c h i n g , and p a r t i c u l a r l y to d e t e r m i n e which i n t e r m e t a l l i c compounds w e r e p r e s e n t . After the m e t a l l o g r a p h i c and X - r a y e x a m i n a t i o n s the s a m p l e s w e r e c h e m i c a l l y a n a l y z e d by p o l a r o g r a p h i c methods to d e t e r m i n e the c a d m i u m c o n tent of the a l l o y s . RESULTS The r e s u l t s of the p r e s e n t study a r e s u m m a r i z e d in F i g . 1, which is a plot of the t i t a n i u m - r i c h end of the T i - C d p h a s e d i a g r a m . The e s s e n t i a l f e a t u r e s of this d i a g r a m a r e as follows. C a d m i u m d i s s o l v e s in both the bcc /3 phase and the hcp ~ phase of t i t a n i u m . D i s solve

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