Effect of heat treatment on the creep-rupture properties of T-111
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DISTANCE I0 t NORMAL TO ~ / INTERFACE, o[-
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~o 7% Cu
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-51 -50 (a)
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I 0
I 25
I 50
I 75
I 100
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125
DISTANCE ALONG INTERFACE FROM EDGE OF COPPER,/.L Y
DISTANCE 15 NORMAL TO ^
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void and c o m p a r e s this to the a v e r a g e of the p e n e t r a tion d i s t a n c e s of the group of points f a r t h e r from the void, a d i f f e r e n c e of 5.0/~ is found. The magnitude of the o b s e r v e d shifts is l a r g e enough to affect p e n e t r a t i o n m e a s u r e m e n t s s i g n i f i c a n t l y ; t h e r e f o r e , in o r d e r to be r e p r e s e n t a t i v e of bulk diffusion, m e a s u r e m e n t s of conc e n t r a t i o n g r a d i e n t s should be made at l e a s t 560 ~t f r o m a d i s c o n t i n u i t y as wide as 141/~ and a v e r a g e s of s e v e r a l m e a s u r e m e n t s should be used. This study shows that the p r e s e n c e of d i s c o n t i n u i t i e s such as voids and edges in Cu-Ni diffusion couples can have a s i g n i f i c a n t effect on the m e a s u r e m e n t of c o n c e n t r a t i o n g r a d i e n t s b y use of e l e c t r o n p r o b e m i c r o a n a l y s i s . However, by s e l e c t i v e l y avoiding t h e s e d i s c o n t i n u i t i e s , c o n c e n t r a t i o n g r a d i e n t s r e p r e s e n t a t i v e of bulk diffusion may be obtained.
"b7% Cu
INTERFACE, *J F 5-0 (b)
"'-X I [ I I I I I 0 IO0 200 300 400 500 SO0 700 DISTANCE ALONG INTERFACE FROM EDGE OF VOID, p.
Effect of Heat Treatment on the Creep-Rupture Properties of T-111
Fig. l(a)--Isoconcentration diagram of the distribution of copper in the nickel part of a Cu-Ni diffusion couple near a copper edge. (b) Isoconcentration diagram of the distribution of copper in the nickel part of a Cu-Ni diffusion couple with a 141/a wide void.
i n t e n s i t i e s which have b e e n c o r r e c t e d for a b s o r p t i o n effects. Only the 7 pct c u r v e is shown, although c u r v e s for o t h e r p e r c e n t a g e s had the s a m e shape and w e r e e s s e n t i a l l y p a r a l l e l . P e n e t r a t i o n of the 7 pct Cu diffusion f r o n t into the nickel is 3 bt at the copper edge, while at a p o i n t 100/z f r o m the copper edge the p e n e t r a t i o n d i s t a n c e is 4.5/~. No f u r t h e r change is s e e n in this p e n e t r a t i o n d i s t a n c e at points f u r t h e r than 100 ~t f r o m the copper edge. The p e n e t r a t i o n d i s t a n c e d e c r e a s e s to z e r o on the n i c k e l s u r f a c e 33 ~ f r o m the copper edge. Thus in the case of the copper edge studied, c o n c e n t r a tion g r a d i e n t s should be m e a s u r e d at l e a s t 100/z f r o m the edge to be r e p r e s e n t a t i v e of bulk diffusion. Fig. l(b) is an i s o c o n c e n t r a t i o n d i a g r a m of the d i s t r i b u t i o n of copper in the n i c k e l p a r t of the Cu-Ni d i f fusion couple with a d i f f e r e n t type of d i s c o n t i n u i t y . This couple was f o r m e d by h e a t i n g at 6000C for 24 hr. The c o n f i g u
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