High temperature creep behavior of class I and class II solid solution alloys
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e, sec"1
eo
8.3" 10"s 8.3" 10-4 8.3" 10-3
17 18 20
b, 10-~ 9 ~ 2.3 1.8 1.6
T,~ 300 573 673 773
A,seca
a
18 15 14 11.5
0.08 0.13 0.15 0.15
Co and b and of the t e m p e r a t u r e dependent c o n s t a n t s A and a a r e g i v e n in T a b l e II. T h e s e c o n s t a n t s could be useful when g e n e r a l i z i n g r e s u l t s on the d o u b l e - n b e h a v i o r of p o l y c r y s t a l l i n e ~ - F e with low contents of i n t e r s t i t i a l a t o m s to o t h e r t e m p e r a t u r e s and s t r a i n -
High Temperature Creep Behavior of Class I and Class II Solid Solution Alloys W. R OGE R CANNON AND O L E G D. SHERBY
U N T I L r e c e n t l y the high t e m p e r a t u r e c r e e p b e h a v i o r of m e t a l l i c s o l i d solution a l l o y s was c o n s i d e r e d to be d i f f e r e n t f r o m that of pure m e t a l s . Sherby and Bu r k e 1 have pointed out, h o w e v e r , that a g r e a t n u m b e r of a l l o y s b e h a v e s i m i l a r l y to pure m e t a l s at a l l c o n c e n t r a tions a c r o s s the phase d i a g r a m and p r o p o s e d that s o l i d solution a l l o y s be d i v i d e d into two c a t e g o r i e s . Th o s e a l l o y s whose b e h a v i o r is d i f f e r e n t f r o m pure m e t a l s w e r e d e s i g n a t e d a s C l a s s I a l l o y s and those a l l o y s which behave s i m i l a r l y to pure m e t a l s as C l a s s II a l l o y s . E v i d e n c e h a s b e e n a c c u m u l a t e d to show that e a c h type of s o l i d solution a l l o y has c e r t a i n c r e e p c h a r a c t e r i s t i c s . T h u s , C l a s s I a l l o y s e x h ib it a p o w e r law dependence of c r e e p r a t e w h e r e the s t r e s s e x ponent n, is about t h r e e ; t h e s e a l l o y s do not show s i g n i f i c a n t p r i m a r y c r e e p and a r e not i n f l u e n c e d by s t a c k i n g fault e n e r g y or s u b g r a i n s i z e changes. On the o t h e r hand C l a s s II a l l o y s e x h i b i t a p o w e r law d e pendence of c r e e p r a t e w h e r e n e q u a l s five; t h e s e a l l o y s show l a r g e p r i m a r y c r e e p c h a r a c t e r i s t i c s and a r e i n f l u e n c e d by c h a n g e s in s t a c k i n g fault e n e r g y and subgrain size. In c o n s i d e r i n g C l a s s I s o l i d solution a l l o y s , W e e r t man 2 d e r i v e d the following e q u a t i o n f o r the s t e a d y st at e r a t e , Es, of a glide c o n t r o l l e d p r o c e s s which, when b a s e d on C o t t r e l l l o c k i n g , is given by (y3 ds = g ~ [1] with cr b ei n g the a p p l ie d s t r e s s , G the s h e a r m o d u l u s , and K an i n t e r a c t i o n c o n s t a n t given as W. ROGER CANNON and OLEG D. SHERBY are Graduate Research Assistant and Professor of Materials Science, respectively, Department of Materials Science, Stanford University, Stanford, Calif. Manuscript submitted July 21, 1969. 1030-VOLUME 1,APRIL 1970
r a t e s than those u s e d in a p a r t i c u l a r i n v e s t i g a t i o n . The c o
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