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RELATIONSHIP BETWEEN INTERNAL FRICTION
AND CREEP RUPTURE BEHAVIOR OF
ALUMINUM ALLOYS
Ting-Chuan Lei
To cite this version:
RELATIONSHIP BETWEEN INTERNAL FRICTION AND CREEP RUPTURE BEHAVIOR
OF
ALUMINUM ALLOYS
Ting-Chuan L e i
Department of Metals and TechnoZogy, Harbin I n s t i t u t e of Technology, Harbin, Repub l i e o f China ABSTRACT I n t e r n a l f r i c t i o n m e a s u r e m e n t s a n d c r e e p r u p t u r e t e s t s w e r e c a r r i e d o u t o n A I - C U , A I - F e a n d A 1 - S i a l l o y s a n d a c o m m e r c i a l A l - C u - X g - S i - F e a l l o y . I t w a s f o u n d t h a t u n d e r c o n d i t i o n s o f t h e s a m e q r a i n s i z e t h e r e l a t i o n s h i p b e t w e e n i n t e r n a l f r i c t i o n 1 ( Q - ) a n d c r e e p r u p t t ~ r e t i m e ( * ) may b e w r i t t e n a s - y = A-t3Q-l. i n w h i c h A a n d B a r e c o n s t a n t s . INTRODdCTION --p- -A l t h o u g h t h e i n t e r n a l f r i c t i o n o f p u r e -A1 a n d i n f l u e n c e o f g r a i n s i z e a n d i m p u r i t i e s o n i t h a v e a l r e a d y b e e n i n v e s t i g a t e d i n d e t a i l ( e . g . ) , b u t t h e r e a r e o n l y f e w w o r k s i n l i t e r a t u r e ' 3 ' 4 ) o n s y s t e m a t i c s t u d y o f t h e e f f e c t o f a l l o y i n g e l e m e n t s w i d e l y ~ ~ s e d i n c o m m e r c i a l A l - a l l o y s , p a r t i c c ~ l a r l y a l l o y s f o r e l e v a t e d t e m p e r a t u r e s . I n e x a m i n i n g t h e s t r t ~ c t ~ r r a l c h a n q e s d u r i n q c r e e p t e s t s o f p o r e . ~ t a l s a n d a l l o y s '5'677' i t w a s f o u n d t h a t t h e i n t e r n a l f r i c t i o n v a l u e s d e c r e a s e d a t t h e l S t , k e p t c o n s t a n t a t t h e ? n d a n d i n c r e a s e s a t t h e 3 r d s t a g e u p t o r u p t u r e . T h e a u t h o r s r ~ l a t e d t h i s p h e n o m e n o n t o v a r i a t i o n s o f t h e d e n s i t y o f m o b i l e d i s l o c a t i o n s . I n s t u d y i n g t h e e f f e c t o f r4g c o n t e n t o n c r e e p b e h a v i o r o f ~ 1 " ' a n d Zn o n Cu (9' t h e i n t e r n a l f r i c t i o n w a s s h o w n a s v a r i e d o p p o s i t e l y w i t h c r e e p r e s i - s t a n c e . T h e r e f o r e , i t s e e m s p o s s i b l e t o e s t a b l i s h f o r m e t a l s a n a a l l o y s s o m e r e l a t i o n s h i p b e t w e e n i n t e r n a l f r i c t i o n v a l u e s a n d c r e e p r u p t u r e c r i t e r i a . T h e a i m o f t h e p r e s e n t p a p e r i s t o e x a m i n e w h a t e v e r r e l a - t i o n s h i p e x i s t s i n t h e c a s e o f a n n e a l e d b i n a r y A 1 - C U , A 1 - F P a n d A 1 - S i a l l o y s a n d a c o m m e r c i a l A I - C L I - M g - S i - F e - a l l o y , i n o r d e r t h a t t h e i n t e r n a l f r i c t i o n m e a s u r e m e n t s , b e i n g a n ~ x t r e m e l v s e n s i t i v e i n d i c a t o r o f a l l o y s t r c t u r ~ , m i g h t h e c ~ t i l i z e d i n p r e d i c t i n g t h e c r e e p r u p t u r e b e h a v i o r o f a l l o y s .
C5-488 JOURNAL DE PHYSIQUE
MATERIALS AND EXPERIMENTAL PROCEDURE
M a t e r i a l s u s e d i n t h i s i n v e s t i g a t i o n were i a e l t e d w i t h c o m m e r c i a l p u r e A 1 a n d i n t e r m e d i a t e a l l o y s . T h e m e l t s were c a s t i n t o 4 3 5 x 2 5 0 m m i n g o t s , m a c h ' i n e d t o + 2 5 x 5 0 m m r o d s , t h e n h o m o g e n i z e d a n d h o t w o r k e d t o ~ 1 0 x 7 0 m m b a r s . T h e b a r s were c o l d d r a w n b y s e v e r a l p a s s e s t o
4
0 . 8 5 - v 1 . 0 9 m m w i r e s w i t h i n t e r m e d i a t e a n n e a l i n g a t 4 5 0 ~ ~ . Wires w i t h v a r i o u s a l l o y i n g a d d i t o n s w e r e f i n a l l y a n n e a l e d f o r 1 - 4 h o u r s a t 3 5 0 4 8 0 ~ ~ f o r o b t a i n i n g a p p r o x i m a t e l y t h e s a m e g r a i n s i z e i n t h e r a n g e 0 . 0 1-
0 . 0 5 m m . I n t e r n a l f r i c t i o n a n d c r e e p r u p t u r e t i m e f o r e a c h a l l o y # e r e t e s t e d o n s p e c i m e n s c u t f r o m t h e s a m e w i r e . I n t e r n a l f r i c t i o n m e a - A s u r e m e n t s w e r e c a r r i e d o u t i n a K e - t y p e t o r s i o n - p e n d u l u m w i t h a f r e - q u e n c y o f + l Hz a t r o o m t e m p e r a t u r e , w h i l e t h e c r e e p r u p t u r e t i m e s w e r e d e t e m i n e d a t 2 5 0 ~ ~ o n a c r e e p m a c h i n e s p e c i a l l y d e s i g n e d f o r w i r e s p e c i m e n s w i t h d i r e c t l o a d i n g . RESULTS A N D DISCUSSION T h e i n f l u e n c e o f a l l o y i n g a d d i t i o n s o n i n t e r n a l f r i c t i o n c u r v e s f o r a n n e a l e d b i n a r y A 1 - C U , A 1 - F e a n d A 1 - S i a l l o y s a r e show^ o n F i g . 1 . I n c a s e s o f A1-Cu a n d A 1 - F e , u n d e r c o n d i t i o n s o f i d e n t i c a l g r a i n s i z e , t h e i n t e r n a l f r i c t i o n c u r v e a s a w h o l e c o n t i n u o u s l y d e c r e a s e s w i t h i n c r e a s i n q t h e Cu o f F e c o n t e n t . T h e t e m p e r a t u r e p o s i t i o n s o f g r a i n - b o u n d a r y p e a k d o a l m o s t n o t v a r y w i t h i n t h e e x t e n t o f c o n c e n t r a t i o n s i n v e s t i g a t e d a n d t h u s i n d i c a t e s t h a t t h e a d d i t i o n o f Cu a n d F e i n a n n e a l e d A1 a l l o y s , i n f o r m s o f p a r t i c l e s o f s e c o n d a r y p h a s e s Cu A 1 2 a n d F e A 1 3 w i t h p i n n i n g e f f e c t t o i n t e r g r a i n d i s l o c a t i o n s a n d g r a i n - b o u n d a r i e s , d o e s n o t c h a n g e t h e a c t i v a t i o n e n e r g y o f r e l a x a t i c n p r o c e s s e s a n d h e r e w i t h t h e s t r u c t u r e o f q r a i n - b o u n d a r i e s b u t m e c h a n i - c a l l y i n f l u e n c e s o n a b i l i t y o f g r a i n - b o u n d a r y s l i d i n g a n d m o b i l i t y o f d i s l o c a t i o n s . T h e r e i s a n o p p o s i t e s i t u a t i o n i n t h e c a s e o f A 1 - S i . T h e i n t e r n a l f r i c t i o n c u r v e s r i s e u p w a r d a n d t h e t e m p e r a t u r e p o s i t i o n o f t h e g r a i n - b o u n d a r y p e a k m o v e s s l i g h t l y t o t h e l o w e r t e m p e r a t u r e s i d e w i t h i n - c r e a s i n g S i c o n t e n t . A l t h o u g h t h e t r u e c a u s e s b y w h i c h t h e a b o v e m e n - t i o n e d b e h a v i o r o f A 1 - S i a l l o y s s t a n d s a r e u n k n o w n , i t s e e m s b e l i - e v a b l e t h a t t h e s t r u c t u r e s o f A 1 - S i a l l o y s a r e l e s s s t a b l e t h a n t h o s e o f p u r e A 1 u n d e r c o n d i t i o n s o f t h e s a m e g r a i n s i z e . When t h e e x p e r i m e n t a l r e s u l t s o f b o t h i n t e r n a l f r i c t i o n m e a s u r e --
l t n e n t a t 2 5 0 ~ ~ ( Q28,,-) a n d t h e c o r r e s p o n d i n g c r e e p r u p t u r e t i m e a t t h e s a m e t e m p e r a t u r e (qa500)
a r e p l o t t e d s i m u l t a n o t l s l y a g a i n s t c o n c e n -trations of alloying elements, as was shown in Fig. 2, a strong impres- sion imnediately arises that the Q-' and T values vary in opposite
a05 a04 a 4
QOJ 0
Temperature'% Temperature 'C Temperature 'C
1 - A I ; 2-Al+O.O9%Cu g l - A1
+
0,07%Fe; l - AI;3 - A l t 0.39%Cu, 2-A1+0.31%Fe; 2 -A1 t 0.27 % S i ;
4 - A l c 0 . 9 5 C u 3 3 - A 1 + 0 . 4 7 % F e g 3- A1+0.55%Si3
5
-
A l + 3.08XCu 4 - A 1 -t l.O%Fe 4 - A l . 1.1756SiGrain size 0.05 mm Grain size O.0lmm Grain size 0.05mm
Fig. 1 Internal friction curves of annealed AI-CU
,
AI-Fe and Al-Si alloysC
Fig. 2 Creep rupture time (at
U = Zkg/mmZ. f o r AI-Cu
,
U = lkg/mm2 am.z
f o r AI-Fe and AI-Si ) and internalfriction value of alloys a t 250.C
e
U o
n t 44 0s m do j.2 L+ rs
InternnI f r i c t i o n
17ig.3 Crccp rnpL1cl.c timc v s . i ~ i l c r n a l friction data l o r A I - C u , AI-Fc and AI-Si alloys a t 2 5 0 ~ V 1 nlcrnal friclion
-
Internal f r i c t i o n U 50 l n t c r n a l f r i c t i o n I 0 20 JO 40 50Deformation % Fig..S Creep rupture time
Fig.4 Crccp ~.uplul.c t i n ~ c ; ~ t 2 6 0 , ~ ~ ( a t U = 6 - 3 3 kg/mm2) vs. internal G . : i 3 k e / m m ~ a n d jotcrna] fric.ion a t friction data f o r the Cu :!20,250, atid 270°C f o r thc A I - . l . 0 5 ~ : , ~ -1.27 -1.27 Mg-0.7,Si-O.4Fc alloy a t blg-0.7Si-O.dPc alloy wit11 1.cspcc1 10 deg1.c~ 250°C