Dependence of fatigue life of 5052 aluminum in aqueous NaCl on specimen polarization
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a
c
Co-5 pct Fe
2.510A
8.178A
3.258
Co-2 pct Fe
2.512A
8.162A
3.249
c/a
T h e s e w e r e d e t e r m i n e d by l e a s t - s q u a r e s a n a l y s i s o f t h e sin s 0 v a l u e s r e g r e s s e d a s a f u n c t i o n o f t h e i n d i c e s and the Nelson-Riley extrapolation function. T h e latter f u n c t i o n w a s a l s o i n c o r p o r a t e d into t h e c a l c u l a t e d d s p a c i n g s in t h e t a b l e . N o t e that t h e r e a r e f i v e r e f l e c t i o n s due t o t h e p h a s e a l o n e in t h e a l l o y w i t h 5 p c t F e . T h e o n l y o t h e r p o s s i b l e r e f l e c t i o n of t h i s s o r t o v e r t h e r a n g e c o v e r e d (4.1 t o 0.93.~) i s the (107) l i n e a t 1 . 0 3 A . In a r a n d o m l y o r i e n t e d c o n d i t i o n it w o u l d h a v e a b o u t t h e s a m e i n t e n s i t y a s ( 2 0 3 ) , but s i n c e (107) m a k e s a s m a l l a n g l e w i t h t h e b a s a l p l a n e , i t s a b s e n c e is a t t r i b u t a b l e to t h e n o n r a n d o m c o n d i t i o n , w h i c h , as n o t e d a b o v e , t e n d s to a v o i d the b a s a l plane. T h e a l l o y with 2 pct Fe contains l e s s ~? p h a s e , a n d o n l y t h e t w o s t r o n g e s t r e f l e c t i o n s o f this sort a p p e a r . T h e a l l o y w i t h 15 p c t F e r e m a i n e d f c c a f t e r e r o s i o n . T h e 7/ s t r u c t u r e i s a n a l l o t r o p i c f o r m o f t h e e l e m e n t s Ce, La, Nd, P r , and A m , and its stacking se-
Dependence of Fatigue Life of 5052 Aluminum in Aqueous NaCI on
q u e n c e is f o u n d in s e v e r a l A B 3 - t y p e o r d e r e d , c l o s e p a c k e d i n t e r m e t a l l i c c o m p o u n d s . 1~ S i n c e t h e b e s t k n o w n c o m p o u n d of t h i s t y p e , N i 3 T i , i s d e s i g n a t e d a s 0 p h a s e , we p r o p o s e t o u s e t h i s s y m b o l u n i v e r s a l l y f o r f o u r - l a y e r e d c l o s e - p a c k e d s t r u c t u r e s , a s e is used a l m o s t universally for t h e two-layered f o r m . Metallographic examination of sectioned s p e c i m e n s r e v e a l e d a p h a s e with a distinctive morphology located a d j a c e n t t o the e r o d e d s u r f a c e i n t h e a l l o y s c o n t a i n i n g 2 a n d 5 pct F e . F i g . 1 s h o w s t h i s p h a s e w h i c h h a s a blocky form often with a saw-tooth interphase on the side r e m o t e f r o m t h e e r o d e d s u r f a c e . T h e m o r p h o l ogy c o n t r a s t s with t h e characteristic t r a n s f o r m a t i o n m a r k i n g s in t h e m a t r i x . W e b e l i e v e t h i s p h a s e is t h e i d e n t i f i e d by X - r a y d i f f r a c t i o n . 1. J. B. Hess and C.S. Barrett: Trans. AIME, 1952, vol. 194, p l 645. 2 . R. D. Heidenreich andW. Shockley: inStrength in Solids, 1948, (Rep. on the Conf., Univ. of Bristol, July, 1947) The Physical Society, London, p . 57. 3. T. Ericsson: ActaMet., 1966, vol. 14, p . 853. 4 . H. Derow andH. E. Bleil: NASA Rep., No. Cr-1590, 1970. 5. A. H. Graham: Trans
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