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Submitted on 1 Jan 1981
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INTERNAL FRICTION DURING STEADY STATE
CREEP OF 25Cr-20Ni AUSTENITIC STAINLESS
STEEL
T. Yamane, Y. Takahashi, K. Hatano
To cite this version:
page C5-481
INTERNAL F R I C T I O N DURING STEADY STATE CREEP OF 2 5 C r - 2 0 N i A U S T E N I T I C STAINLESS STEEL
T. Yamane, Y. Takahashi and K. Hatano
Department o f Materials Science and Engineering, Osaka University, Yamadakami, Suita, Osaka 565, Japan
A b s t r a c t . I n t e r n a l f r i c t i o n was m e a s u r e d t o know t h e c h a n g e s i n t h e d i s l o c a t i o n d e n s i t y a n d l o o p l e n g t h d u r i n g t h e s t e a d y s t a t e c r e e p . Main e x p e r i m e n t a l r e s u l t s a r e ( 1 ) I n t e r n a l f r i c t i o n o f f i n e g r a i n s e c i m e n s (d=30pm) i s c o n s t a n t d u r i n g t h e s t e a d y s t a t e c r e e p . ( 2 7 The d e c r e a s e i n i n t e r n a l f r i c t i o n i s o b s e r v e d i n medium (d=150pm) a n d c o a r s e ( d = 6 0 0 - 8 5 0 p m ) g r a i n s p e c i m e n s , a n d
i t i s r e m a r k a b l e a t h i g h c r e e p
2
t r e s s . The d e c r e a s e i s c o n - s i d e r e d t o c o r r e s p o n d t o t h a t o f A l . 1. I n t r o d u c t i o n . Changes i n t h e d i s l o c a t i o n d i s t r i b u t i o n a n d d e n s i t y d u r i n g c r e e p a r e known by t h e d i r e c t o b s e r v a t i o n o f a n e l e c t r o n m i c r o - s c o p e . No c h a n g e i s i n them a t l o w s t r e s s 1 ) w h e r e t h e v a c a n c y c r e e p o c - c u r s , b u t t h e y a r e c h a n g e d d u r i n g t h e s t e a d y s t a t e c r e e p i n t h e r e g i o n o f t h e power l a w c r e e p ? ) 3 ) T h e s e c h a n g e s c a n b e i n v e s t i g a t e d by t h e m e a s u r e m e n t s of i n t e r n a l f r i c t i o n t o o . D u r i n g d e f o r m a t i o n , t h e i n t e r n a l f r i c t i o n &-l c o r r e s p o n d i n g t o d i s l o c a t i o n s c a n b e e x p r e s s e d4
by t h e f o l l o w i n g e q u a t i o n . U ~ E Ag
8 1 - 1 ~ E b ~ ~w h e r e e a c h symbol means t h a t shown i n T a b l e 1. The f i r s t t e r m i n t h e r i g h t o f E q u a t i o n ( 1 ) i s c o n s t a n t d u r i n g t h e s t e a d y c r e e p f o r c o n s t a n t
G
a n d t h e s e c o n d t e r m c o r r e s p o n d s t o a k i n d o f G r a n a t o - L i i c k e r e l a x - ation!) The e q u a t i o n c a n b e a p p l i e d a t s m a l l s t r a i n a m p l i t u d e a n d i nT a b l e 1 S y n b o l s i n E q u a t i o n ( l ) . -
A : dislocation density , G : line energy B : quasi viscous constant , & : strain rate
1 . average loop length , : frequency
b : Burgers vector , E : elastic modulus
p ' orientation factor , v : activation volume
T : absolute temperature
.
k : Bdtzmann constantt h e l o w e r r e s o n a n c e v i b r a t i o n f r e q u e n c y t h a n kHz. I n t h i s s t u d y , t h e c h a n g e i n A 1 4 d u r - i n g t h e s t e a d y s t a t e c r e e p i s g u e s s e d by t h e m e a s u r e m e n t s o f t h e i n t e r n a l f r i c t i o n .
C5-482 JOURNAL DE PHYSIQUE 2. E x p e r i m e n t a l s . E l e c t r o l y s i s i r o n , n i c k e l a n d chromium w e r e m e l t e d i n t h e vacuum o f 1 0 - ' t o r r . A c a s t i n g o t was h o t - f o r g e d a n d c o l d - d r a w n t o 2mm d i a m e t e r w i r e . The c h e m i c a l c o m p o s i t i o n s o f t h e w i r e a r e C r 2 2 . 7 7 , N i 2 1 . 3 9 , C 0 . 0 0 5 , Mn n i l , S i 0 . 0 2 , P 0 . 0 0 4 a n d F e b a l . i n w e i - g h t $. The g r a i n s i z e o f t h e c r e e p s p e c i m e n s was c o n t r o l l e d by r e c r y - S t a l l i z a t i o n h e a t i n g a t v a r i o u s t e m p e r a t u r e s a n d f o r v a r i o u s t i m e l e n g t h . T h e g a u g e l e n g t h o f t h e c r e e p s p e c i m e n s was 45mm. T h e g r a i n s i z e was m e a s u r e d by t h e g r a i n i n t e r c e p t m e t h o d 6 ) I n t e r n a l f r i c t i o n w a s o b t a i n e d by t h e n a t u r a l d e c a y o f t o r s i o n a l r e s o n a n c e v i b r a t i o n d u - r i n g c r e e p , a n d t h e v i b r a t i o n f r e q u e n c y w a s 0.8-2Hz.
3.
R e s u l t s . F i g s . 1 a n d 2 show e x a m p l e s o f c r e e p c u r v e s a n d i n t e r n a l f r i c t i o n m e a s u r e d d u r i n g c r e e p . T h e s e s p e c i m e n s h a v e t h e a v e r a g e g r a i n s i z e o f 3 0 a n d 850mv r e s p e c t i v e l y . C h a n g e s i n i n t e r n a l f r i c t i o n a r e summed u p i n F i g s .3
a n dL .
From t h e s e f i g u r e s , f o l l o w i n g r e s u l t s cand = 30 p m o T=l133K 6 a = 1 L ? M P a 1133K 2 L 5 M P a A 1173K 1 9 . 6 M P a A 1173K 21. 5 M P a X )A.;\ i'?,d-...., s t e a d y s t a t e c r e e p Ta 'A, - A -A.., r e g i o n ,A *..---L.- A . .-A - . .A -. .A - - -A-. - A - ?\& - - .A -- -A-- - -- - - - 7 - *..- 0 . * - . - - * - - - ~ ~ ' ~ . o ~ o ~ o ~ o ~ G - - -
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n a l f r i c t i o n . (d=RSOurn, n,=34.3 MPa ) G - C. . 0 X 5 '0 L 3 F i g .3
C h a n g e s i n i n t e r n a l f r i c t i o n d u r i n g c r e e p . *\., 1173K 0 *\ ' 0 . 0- '--a- o.~'*.. ,-.-.-steady state creep
C5-484 JOURNAL DE PHYSIQUE
7 - T r l l 3 3 K , d = l 5 O y m
0 0 14.7 MPa
a
,
Z L . S MPa\A A 3 L . 3 MPa
5
-
,.o, A',.: b--.A__ ;-.-steady stale creep region*\*.
0-*-.* -A . L - : L..* -*-m-.-. 7 F i g . 4 C h a n g e s i n i n t e r n a l f r i c t i o n d u r i n g c r e e p ....-
T = l l 3 3 ~ , O a = 3 L 3MPa - 0 3 0 p m t i o n c o r r e s p o n d s t o t h e d i s l o c a t i o n c r e e p r e g i o n a s shown i n F i g . 5 1 ) A t t h e i n i t i a l s t a g e o f t h e c r e e p , t h e r e i s a f o l l o w i n g r e l a t i o n b e t - ween 1 a n d h , 1I
- 1 2- - -
( 2 ) a n d AI' h-' c a n b e i n t r o d u c e d . T h i s m e a n s i n t e r n a l f r i c t i o n d e c r e a s e s w i t h d i s l o c a t i o n d e n s i t y d u r i n g o n l y i c i t i a l c r e e p ? ) A f t e r t h e m i d d l e s t a g e o f t h e t r a n s i t i o n c r e e p , t h e a n n i h i l a t i o n a n d r e a r r a n g e - m e n t s o f d i s l o c a t i o n s a n d t h e f o r m a t i o n o f s u b s t r u c t u r e s m u s t b e c o n - s i d e r e d ? ) * ) but t h e m a i n c a u s e o f t h e d e c r e a s e o f t h e i n t e r n a l f r i c - t i o n may owe t,o t h a t o f5 C o n c l u s i o n . I n t e r n a l f r i c t i o n c o r r e s p o n i n g t o h14 was m e a s u r e d i n t h e s t , e a d y s t a t e c r e e p r e g i o n w h e r e t,he c r e e p i s c o n t r o l l e d by t h e d i s l o c a t i o n - r e c o v e r y . The m a i n e x p e r i m e n t a l r e s u l t s o b t a i n e d a r e a s f o l l o w s , ( 1 ) I n t e r n a l f r i c t i o n o f t h e f i n e g r a i n s p e c i m e n s (30um) i s c o n s t a n t d u r i n g t h e s t ~ a d ; y s t , a t , e c r e e p .
( R ~
r e g i o n i n F i g . 5 ) ( 2 ) The medium ( 1 5 0 ~ m ) a n d c o a r s e ( 6 0 0 - 8 5 0 v m ) g r a i n s p e c i m e n s h a v e N * 150 p m A 850 y m:-+steady state creep regiwl
s t e a d y s t a t e c r e e p . o: c r e e p s t r e s s G : s h e a r m o d u l u s d : g r a i n s i z e b: B u r g e r s v e c t o r T: c r e e p t e m p e r - a t u r e T m : s o l i d u s tem- p e r a t u r e
d l b
io5
10" 1o7 t h e d e c r e a s e i n i n t e r n a l f r i c t i o n . ( R 2 r e g i o n i n F i g . 5 )6.
R e f e r e n c e s . 1 ) F . R . B e c k i t t , T.M.Banks a n d T.Glaman: C r e e p S t r e n g t h i n S t e e l a n d H i g h - t e m p e r a t u r e A l l o y s , ( 1 9 7 4 ) 71, M e t a l s S o c i e t y , London. 2 ) 0 . D . S h e r b y a n d P. M.Burke: " P r o g . M a t e r . S c i ? u ( 1 9 6 6 ) 3 2 5 , P e r g a - mon P r e s s , London.3 )
A . O r l o v a , M.Pahutova and J . C a d e k : P h i l . Mag. a ( 1 9 7 2 ) 8 6 5 ,4 )
G . K a i s e r a n d W.Pechhold: A c t . Met. l 7 ( 1 9 6 9 ) 527,5 ) A . G r a n a t o a n d K.Lucke: J . Appl. Phys. a ( 1 9 5 6 ) 583.
6 ) P . S h a h i n i a n a n d J . R . Lane: T r a n s . A m e r . S o c . Met. G ( 1 9 5 J ) 1 7 7 . 7 ) Y . T a k a h a s h i a n d T.Yamane: J. M a t e r . S c i . To be p u b l i s h e d . 8 ) 0 . A j a j a a n d A . J . A r d e l 1 : P h i l . Mag. A a ( 1 9 7 9 ) 65.
