Electron-optical investigation of hydrogen-induced deformation in nickel single-crystal foils
- PDF / 3,513,308 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 87 Downloads / 185 Views
1. INTRODUCTION H Y D R O G E N in n i c k e l , n i c k e l a l l o y s , and a u s t e n i t i c s t e e l s is known to have d e l e t e r i o u s effects on the m e c h a n i c a l p r o p e r t i e s of t h e s e m a t e r i a l s , e s p e c i a l l y f r a c t u r e b e h a v i o r . I n a r e c e n t r e v i e w of t h e s e effects, M c L e l l a n and H a r k i n s 1 pointed out that e l e m e n t a l n i c k e l is m o r e s u s c e p t i b l e to these than n i c k e l a l l o y s o r a u s t e n i t i c s t e e l s , and that m o r e d e t a i l e d m i c r o s t r u c t u r a l d e s c r i p t i o n s of h y d r o g e n induced s t r u c t u r a l changes than can be obtained by optical m e t a l l o g r a p h i c t e c h n i q u e s a r e not g e n e r a l l y a v a i l a b l e . H y d r o g e n is u s u a l l y added to s p e c i m e n s b e f o r e t e s t i n g by cathodic charging and quite high c o n c e n t r a t i o n s a r e common; sufficient h y d r o g e n can be added to n i c k e l to f o r m h y d r i d e s , even though n i c k e l h y d r i d e s a r e u n s t a b l e at s t a n d a r d t e m p e r a t u r e and p r e s s u r e . New, m o r e subtle effects of hydrogen a b s o r p t i o n i n n i c k e l a l l o y s and a u s t e n i t i c s t e e l have b e e n found by B u s w e l l and F i s h e r ; 2 they concluded on the b a s i s of e l e c t r o n damage e x p e r i m e n t s in a high voltage e l e c t r o n m i croscope that for c e r t a i n conditions of e l e c t r o p o l i s h ing h y d r o g e n a b s o r p t i o n o c c u r r e d d u r i n g p r e p a r a tion of t r a n s m i s s i o n e l e c t r o n m i c r o s c o p e s p e c i m e n s . The h y d r o g e n a b s o r b e d by the s p e c i m e n s i n c r e a s e d the p r o p e n s i t y for e l e c t r o n induced void f o r m a t i o n . T h e i r e l e c t r o n m i c r o s c o p e e x a m i n a t i o n of s p e c i m e n s thinned u n d e r conditions f a v o r a b l e for h y d r o g e n a b s o r p t i o n did not r e v e a l a c h a r a c t e r i s t i c d e f o r m a t i o n s u b s t r u c t u r e a s s o c i a t e d with the a b s o r p t i o n , so it m u s t be a s s u m e d that h y d r o g e n r e m a i n e d in s o l u t i o n . The r e s u l t s above m a y be c o n s i d e r e d e x t r e m e s of hydrogen a b s o r p t i o n . Heavy cathodic c h a r g i n g of a hydrogen r e a c t i v e m a t e r i a l such as n i c k e l can r e s u l t in complete s a t u r a t i o n and compound f o r m a t i o n . E l e c t r o p o l i s h i n g , d u r i n g which hydrogen contained in the R. W. CARPENTER,is a member of Research Staff REMAG, Metals and CeramicsDivision, Oak Ridge National Laboratory, P. O. Box X, Oak Ridge, TN 37830. G. S. BAUER, is a member of Research Staff Institiit fiir FestkSrperforschung, Kernforschungsanlage,Jfilich, D-517 Julich Federal Republic of Germany. Manuscript submitted January 19, 1978. METALLURGICALTRANSACTIONSA
v i s c o u s anodic f i l m e n t e r s the s p e c i m e n
Data Loading...
