The effect of zirconium on the strength of thorium
- PDF / 494,474 Bytes
- 5 Pages / 612 x 783.28 pts Page_size
- 1 Downloads / 212 Views
p o s i t i o n s of 0, 4, 8 and 12 at. p c t w e r e m a d e b y a r c m e l t i n g a weighed a m o u n t of z i r c o n i u m with f i R y g of t h o r i u m . T h e s e i n g o t s w e r e t u r n e d and r e m e l t e d four t i m e s to i n s u r e a u n i f o r m z i r c o n i u m d i s t r i b u t i o n . The ingots w e r e s u b s e q u e n t l y cold s w a g e d to 2.46 m m d i a m r o d s and cut into 5.0 c m long s e g m e n t s . The c o m p o s i t i o n s of the a l l o y s w e r e c h e c k e d b y m e a s u r i n g the l a t t i c e p a r a m e t e r s and c o m p a r i n g the v a l u e s with t h o s e r e p o r t e d b y Johnson and H o n e y c o m b . s The X - r a y s a m p l e s w e r e 0.1 m m n e e d l e s p r e p a r e d b y e l e c t r o p o l i s h i n g r o d s of e a c h a l l o y which had b e e n quenched f r o m 900~ The d i f f r a c t i o n p a t t e r n s w e r e r e c o r d e d with a 11.46 c m d i a m e t e r D e b y e - S c h e r r e r c a m e r a u s ing c o p p e r K a r a d i a t i o n . The o b s e r v e d l a t t i c e c o n s t a n t s a r e given in T a b l e H and c o n f i r m the n o m i n a l c o m p o s i t i o n s of t h e s e a l l o y s . The 12 at. p c t a l l o y c o n s i s t e d of an a l p h a p h a s e s o l i d s o l u t i o n p l u s a b o d y c e n t e r e d cubic b e t a p h a s e containing 67 at. p c t z i r c o n i u m . The a l p h a p h a s e l a t t i c e c o n s t a n t i n d i c a t e d a z i r c o n i u m content of 10.5 at. pct. T h i s is s l i g h t l y h i g h e r than the 9.6 at. p c t s o l u b i l i t y l i m i t r e p o r t e d b y Johnson and Honeycomb. s The a l l o y s w e r e f u r t h e r c h a r a c t e r i z e d b y m e a s u r i n g the e l e c t r i c a l r e s i s t i v i t y of s p e c i m e n s quenched f r o m 900~ a t 298, 77 and 4 . 2 K . The r e s u l t s of t h e s e m e a s u r e m e n t s a r e shown in T a b l e H. The t h o r i u m b a s e m e t a l had a r e s i s t a n c e r a t i o of 34.5 and a 294 K r e s i s t i v i t y which a g r e e d w e l l with the m e a s u r e m e n t s of P e t e r s o n e t al 6 on t h o r i u m of c o m p a r a b l e p u r i t y . The 4 and 8 at. p c t a l l o y s b e h a v e d a s n o r m a l r a n d o m s o l i d s o l u t i o n s and showed an i n c r e a s e in r e s i s t i v i t y of 1.4 • 10 -6 o h m - c m p e r at. p c t z i r c o n i u m at e a c h t e m p e r a t u r e . The 12 at. p c t a l l o y , which had o n l y 10.5 at. p c t z i r c o n i u m in solution, had a c o r r e s p o n d i n g i n c r e a s e in r e s i s t i v i t y a t r o o m t e m p e r a t u r e . H o w e v e r , the r e s i s t i v i t y at 4 . 2 K was v e r y low. T h i s was found to b e due to a s u p e r c o n d u c t i n g t r a n s f o r m a t i o n at 6.3 K in the z i r c o n i u m - r i c h b e t a p h a s e in t h i s a l l o y . A 12 at. p c t a l l o y quenched f r o m 1200~ w h e r e it was a l l t h o r i u m r i c h b e t a p h a s e , t r a n s f o r m e d to a s u p e r s a t u r a t
Data Loading...
