Stress corrosion cracking of alpha brass in a nontarnishing ammoniacal environment:fractography and chemical analysis
- PDF / 1,031,017 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 31 Downloads / 176 Views
t= 1/2tl)
+ A / i s o ( a t 935~
t= 1/2tt)
f r o m Al total g i v e s ~ l trans. A c c o r d i n g to t h i s p r o c e d u r e , the s h r i n k a g e c a u s e d by t r a n s f o r m a t i o n w a s c a l c u l a t e d and p l o t t e d a g a i n s t the n u m b e r of c y c l e s in F i g . 4. The d a t a p o i n t s e x c e p t for the e a r l y s t a g e of s i n t e r i n g fit to a line, which can be r e p r e s e n t e d b y an e q u a t i o n of the f o r m S =AN
[3]
w h e r e S i s the s h r i n k a g e c a u s e d by t r a n s f o r m a t i o n , N, t h e n u m b e r of c y c l e s , and A , a c o n s t a n t . Eq. [1] c o r r e s p o n d s to Eq. [3] when n = 1. It i s m e a n t by t h i s equation t h a t the s h r i n k a g e c a u s e d by t r a n s f o r m a t i o n s h o u l d b e about the s a m e at e v e r y c y c l e . Two p o s s i b l e r e a s o n s can be c o n s i d e r e d about the a c c e l e r a t i n g effect of r e p e a t e d t r a n s f o r m a t i o n on s i n t e r i n g r a t e . The one i s t h e e n h a n c e m e n t of s e l f d i f f u s i o n of i r o n by t r a n s f o r m a t i o n and the o t h e r , the a b n o r m a l softening t h a t o c c u r s d u r i n g t r a n s f o r m a tion, %7 that i s , s u p e r p l a s t i c i t y , s E x p e r i m e n t s with a w i r e m o d e l w e r e c a r r i e d out to r e v e a l the m e c h a n i s m of a c c e l e r a t i o n of s i n t e r i n g r a t e . The s p e c i m e n shown in F i g . 5 c o n s i s t s of w i r e s of 0.5 m m in d i a m s e t in a r r a y in a h o l d e r of p u r e i r o n and a weight p l a c e d on t h e w i r e s . The s p e c i m e n s w e r e s i n t e r e d with the s a m e conditions a s s i n t e r i n g of p o w d e r c o m p a c t s . F i g . 6 shows the c r o s s - s e c t i o n s of the s p e c i m e n a f t e r
Stress Corrosion Cracking of Alpha Brass in a Nontarnishing Ammoniacal Environment: Fractography and Chemical Analysis T . R. PINCHBACK, S. P . CLOUGH, AND L . A . HELDT A n n e a l e d a l p h a b r a s s i s s u s c e p t i b l e to s t r e s s c o r r o s i o n c r a c k i n g (SCC) in both t a r n i s h i n g and nont a r n i s h i n g a m m o n i a c a l e n v i r o n m e n t s . In a r e c e n t p u b l i c a t i o n 1 we d e s c r i b e d the f r a c t o g r a p h y and c h e m i c a l c o m p o s i t i o n of i n t e r g r a n u l a r f r a c t u r e s u r f a c e s r e s u l t i n g f r o m SCC of a l p h a b r a s s in t a r n i s h i n g a m moniacal solutions. The Auger Electron Spectroscopy (AES) r e s u l t s i n d i c a t e d that a thin o x i d i z e d l a y e r p e n e t r a t e d to the l e a d i n g e d g e of the s t r e s s c o r r o s i o n c r a c k ; f o r m a t i o n of the t h i c k e r t a r n i s h f i l m t r a i l e d w e l l behind the l e a d i n g edge and thus p l a y s no a p p a r e n t r o l e in c r a c k p r o p a g a t i o n . No e v i d e n c e was found f o r d i s c o n t i n u o u s c r a c k p r o p a g a t i o n . The p r e s e n t
Data Loading...
