The transformation on annealing of the metastable electrodeposit, NiSn x , to its equilibrium phases
- PDF / 1,980,605 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 111 Downloads / 189 Views
o
1) E X P E R I M E N T A L DETAILS Thin f o i l s of NiSn x w e r e e l e c t r o d e p o s i t e d to the s a m e t h i c k n e s s for both e l e c t r o n m i c r o s c o p y and c a l o r i m e t r y . F o i l s 4000A t h i c k w e r e e l e c t r o d e p o s i t e d on the e l e c t r o p o l i s h e d , flat, (111) s u r f a c e of a c o p p e r single c r y s t a l . M a t e r i a l wSth any c o m p o s i t i o n within the NiSn x s i n g l e B. E. WYNNE, J. W. EDINGTON, and G. P. ROTHWELL are Research Student and Assistant Directors of Research, respectively, Department of Metallurgy, University of Cambridge, Cambridge, England. Manuscript submitted March 22, 1971. METALLURGICAL TRANSACTIONS
phase c o m p o s i t i o n r a n g e could be p r o d u c e d by v a r y i n g the p l a t i n g bath c o m p o s i t i o n , t e m p e r a t u r e , and cathodic c u r r e n t d e n s i t y , s F o i l s w e r e s t r i p p e d f r o m the s u b s t r a t e u s i n g a m m o n i a c a l h y d r o g e n p e r o x i d e solution and p a r t s of s p e c i m e n s w e r e c h e m i c a l l y a n a l y z e d , both b e f o r e and a f t e r a n n e a l i n g t r e a t m e n t s . Electron Microscopy The thin foil s p e c i m e n s w e r e s i m u l t a n e o u s l y h e a t e d and o b s e r v e d using a s t a n d a r d P h i l i p s EM300 e l e c t r o n m i c r o s c o p e h o t - s t a g e . The t e m p e r a t u r e m e a s u r e m e n t w a s c a l i b r a t e d to within +5~ f o r the slow h e a t i n g r a t e s used. T h e thin f o i l s w e r e h e a t e d u n d e r c o n t r o l l e d conditions of two t y p e s , n a m e l y : Type I , r a i s i n g the t e m p e r a t u r e at 10~ p e r min, with p a u s e s of 30 min at i n t e r v a l s of 50~ Type II, r a i s i n g the t e m p e r a t u r e a t 400~ p e r rain to 350~ holding for 1 h r , then r a i s i n g a t the s a m e r a t e to 450~ Calorimetry T h e s e s t u d i e s w e r e p e r f o r m e d u s i n g the s c a n n i n g c a l o r i m e t e r of a Du Pont DTA 900 d i f f e r e n t i a l t h e r m a l a n a l y z e r . Thin foil s a m p l e s of b e t w e e n 10 to 50 mg w e r e u s e d . M e a s u r e m e n t s of a c t i v a t i o n e n e r g y , Q, and e n t h a l p y change, AH, of r e a c t i o n s w e r e m a d e in t h e c o n v e n t i o n a l w a y 7 on two c o m p o s i t i o n s of m a t e r i a l , one containing 35.2 wt pct Ni, and the o t h e r 42.8 wt pct Ni. H e a t i n g w a s p e r f o r m e d u n d e r an a r g o n a t m o s p h e r e at r a t e s b e t w e e n 5 ~ and 40~ p e r m i n f r o m a s t a r t i n g t e m p e r a t u r e of -50~ R e s i s t i v i t y and M i c r o h a r d n e s s In a d d i t i o n to the above e x p e r i m e n t a l t e c h n i q u e s , both e l e c t r i c a l r e s i s t i v i t y and m i c r o h a r d n e s s w e r e m e a s u r e d a s a function of t e m p e r a t u r e in the r a n g e 20 ~ to 300~ In both c a s e s the s p e c i m e n s w e r e 100 ~m t h i c k and c o n t a i n e d e i t h
Data Loading...
