HAL Id: jpa-00225343
https://hal.archives-ouvertes.fr/jpa-00225343
Submitted on 1 Jan 1985
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of
sci-entific research documents, whether they are
pub-lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
MARTENSITIC TRANSFORMATION IN CuZnAl
ALLOYS
Gui Jianian, Feng Jiwen, Wang Zixiao
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C10, suppl6ment au n012, Tome 46, dgcembre 1985 page C10-629
MARTENSITIC TRANSFORMATION IN CuZnAl ALLOYS
GUI JIANIAN, FENG JIWEN AND WANG ZIXIAO
D e p a r t m e n t
of
P h y s i c s ,Wuhan
U n i v e r s i t y , C h i n aA b s t r a c t
-
The e f f e c t s o f t h e r a t e o f h e a t i n g and c o o l i n g . frequency and s t r a i n a m p l i t u d e on i n t e r n a l f r i c t i o n ( I F ) r e l a t e d t o t h e m a r t e n s i t i c t r a n s f o r m a t i o n i n CuZnAl a1 l o y s were i n v e s t i g a t e d . The e f f e c t s o f h e a t - t r e a t m e n t on t r a n s i t i o n and r e l a t e d s t a b i l i z a t i o n were a l s o s t u d i e d b y I F and X-ray.I
-
INTRODUCTIONCuZnAl a l l o y s have n o t o n l y t h e shape memory e f f e c t , b u t a l s o a h i g h damping c h a r a c t e r . I t s damping c a p a c i t y depends on c o m p o s i t i o n , s t r u c t u r e , s t r e s s and t h e r m a l h i s t o r y o f t h e a l l o y . De Jonghe e t a l . /1/ f i r s t r e p o r t e d t h e i r r e s u l t s on t h e I F of CuZnAl a l l o y s i n 1975 and e s t a b l i s h e d t h e De Jonghe model of t h e m a r t e n s i t i c t r a n s f o r m a t i o n /2/. Recently, Koshimizu e t a l . /3/ Humbeeck e t a l . /4/, M o r i n e t a l . /5/ and Jassen e t a l . /6/ a l s o s t u d i e d t h e c h a r a c t e r o f I F o f t h e t r a n s i t i o n and t h e o r i g i n o f h i g h damping. I n t h i s paper we r e p o r t t h e l o w frequency I F o f t h e d i r e c t and r e v e r s e t r a n s f o r m a t i o n i n CuZnAl a l l o y s by means of t o r s i o n a l pendulum and t h e e f f e c t s of t h e r a t e of t e m p e r a t u r e change, frequency. s t r a i n a m p l i t u d e and h e a t t r e a t m e n t on I F b e h a v i o r . The s t a b i l i z a t i o n of
m a r t e n s i t e was s t u d i e d .by measurements of frequency. e l e c t r i c r e s i s t a n c e , a c o u s t i c e m i s s i o n and X-ray d i f f r a c t i o n .
I 1
-
SPECIMENSThe specimens were p r e p a r e d f r o m commercial p u r e copper, z i n c and aluminium. The c o m p o s i t i o n o f #5 and #1 a r e Cu-14.68wtx Zn-7.75wt% A1 (Ms
-
100°C) and Cu-20.4 wt% Zn-6.2wt% A1 (Ms-
48OC) r e s p e c t i v e l y .I 1 1
-
EXPERIMENTAL RESULTS AND DISCUSSION1. F i g u r e 1 shows t h e I F spectrum o b t a i n e d on h e a t i n g a h o t - r o l l e d specimen #1, i n which an asymmetric peak appears a t 40°C, w i t h a c o r r e s p o n d i n g frequency minimum presumably due t o s o f t e n i n g o f t h e phonon mode. F i g u r e 2 shows t h e change o f a c o u s t i c c o u n t i n g r a t e o f a s i m i l a r specimen as t h e above, t h e shape o f w h i c h resembles i t s I F curve. The t e m p e r a t u r e o f t h e maximum i s a l s o 42OC. F i g u r e 2 i s o b t a i n e d f r o m X-ray d i f f r a c t i o n measurement, which shows t h e maximum r a t e o f phase
C10-630 JOURNAL
DE
PHYSIQUEt r a n s f o r m a t i o n i n t h e range o f 40
-
48°C.2. No e f f e c t s o f change o f f r e q u e n c y ( f = 0.2
-
1 Hz) and r a t e o f h e a t i n g and c o o l i n g ( v = 2-
8"C/min) on t h e t e m p e r a t u r e o f I F maximum a r e observed b u t t h e h e i g h t o f t h e peak v a r i e s l i n e a r l y w i t h v / f . These r e s u l t s can be e x p l a i n e d w i t h t h e f i r s t t e r m i n t h e De Jonghe model. i.e. t h e I F i s p r o p o r t i o n a l t o t h e amount o f t r a n s f o r m e d phase d u r i n g one v i b r a t i o n a l p e r i o d . The I F may be a t t r i b u t e d t o t h e m o t i o n o f i n t e r f a c e d i s l o c a t i o n s . The s t r a i n a m p l i t u d e a l s o has an e f f e c t on t h e I F o f t r a n s f o r m a t i o n .The e x p e r i m e n t a l r e s u l t s show t h a t t h e I F of t h e m a r t e n s i t i c phase i s n o t always h i g h e r t h a n t h a t o f t h e p a r e n t . The I F o f m a r t e n s i t e i s a p p r o x i m a t e l y equal t o t h e I F o f t h e p a r e n t
06
s l i g h t l y l e s s t h a n t h e I F o f t h e p a r e n t when t h e s t r a i n a m p l i t u d e i s about 10-.
The I F o f m a r t e n s i t e i n c r e a s e s w i t h s t r a i n a m p l i t u d e , b u t i t s I F i s n o t a l i n e a r f u n c t i o n o f s t r a i n amplitude. The change of I F o f t h e p a r e n t phase w i t h s t r a i n a m p l i t u d e i s n o t obvious. Large numbers o f s t a c k i n g f a u l t s a r e observed i n m a r t e n s i t e by TEM, t h e - - p a r t i a l d i s l o c a t i o n s b e l o n g i n g t o t h e s e f a u l t s e i t h e r e n d i n g a t t h e i n t e r f a c e between t h e m a r t e n s i t i c p l a t e s o r e n d i n g i n s i d e a m a r t e n s i t i c p l a t e . It i s suggested t h a t t h e h i g h damping c a p a c i t y o f m a r t e n s i t e s may be due t o t h e m o t i o n o f i m p e r f e c t d i s l o c a t i o n s and l o c a l change o f t h e o r d e r of s t a c k i n g f a u l t s .3. M a r t e n s i t i c t r a n s f o r m a t i o n i n CuZnAl a l l o y s i s v e r y s e n s i t i v e t o h e a t
t r e a t m e n t s /7,8/. F o r t h e specimen h a v i n g h i g h e r Ms ( f o r example #5), a f t e r i t i s quenched below Ms f r o m t h e t e m p e r a t u r e o f s o l i d s o l u t i o n , no I F peak i s observed on subsequent h e a t i n g . The measurements o f e l e c t r i c r e s i s t a n c e and X-ray
d i f f r a c t i o n w i t h t e m p e r a t u r e changing a l s o show t h a t no r e v e r s e m a r t e n s i t i c t r a n s f o r m a t i o n occurs. The m a r t e n s i t e s a r e t h u s s t a b i l i z e d by t h i s t r e a t m e n t . The I F i n c r e a s e s s l i g h t l y f r o m 150°C t o 250°C on h e a t i n g and t h e r e s u l t o f X-ray d i f f r a c t i o n i n d i c a t e s t h a t i n t h i s t e m p e r a t u r e range, t h e p a r t i a l p a i r s o f d i f f r a c t i o n l i n e s such as (1,2,2) and (2,0,2), (1,2,4) and (2,0,4), (0,4,0) and (3,2?0) e t c . a r e c l o s e t o each o t h e r g r a d u a l l y w i t h a t e m p e r a t u r e i n c r e a s e . T h a t i m p l i e s t h e atoms i n t h e b a s a l p l a n e o f m a r t e n s i t e t e n d t o a r r a n g e i n t o t h e hexagonal s t r u c t u r e .
F o r t h e s t a b i l i z e d m a r t e n s i t e mentioned above. when i t i s up-quenched t o 300°C i n s a l t - s o l u t i o n and h e l d t h e r e f o r 30 seconds, a s i g n i f i c a n t I F peak and f r e q u e n c y minimum a r e observed d u r i n g subsequent c y c l e s . Thus t h e s t a b i l i z e d m a r t e n s i t e r e c o v e r s w i t h t h e r m a l e l a s t i c i t y . I f t h e up-quenching t e m p e r a t u r e i s l o w e r (such as 140°C, 180°C) o r i f t h e specimen i s heated a t a l o w e r r a t e , t h e subsequent up- quenching does n o t r e s u l t i n s t a b i l i z e d m a r t e n s i t e t o r e c o v e r i t s t h e r m a l
e l a s t i c i t y .
When t h e specimen isL,quenched t o a s u i t a b l e t e m p e r a t u r e above Ms from s o l i d s o l u t i o n and remains a t t h i s t e m p e r a t u r e f o r a few minutes, s i g n i f i c a n t I F peaks a r e observed d u r i n g subsequent c y c l e s .
When t h e specimen h a v i n g t h e r m a l - e l a s t i c i t y i s heated t o a much h i g h e r t e m p e r a t u r e t h a n A f b u t l o w e r t h a n t h e t e m p e r a t u r e a t which t h e phase can p r e c i p i t a t e ( f o r example #5 b e i n g heated t o 250°C), t h e maximum v a l u e o f I F peak decreases n o t i c e a b l y on subsequent c y c l e s , Ms and/or As a l s o decreases. X-ray d i f f r a c t i o n w i t h t e m p e r a t u r e changing shows t h a t a p a r t i a l p a r e n t phase i s s t a h i l i z e d .
When t h e t e m p e r a t u r e Ms o f t h e specimen i s c l o s e t o room t e m p e r a t u r e and quenched below Mf f r o m t h e t e m p e r a t u r e o f s o l i d s o l u t i o n ( f o r example i n # I ) , i t e x h i b i t s a broad and l o w I F peak on t h e f i r s t h e a t i n g c y c l e . On t h e second and t h i r d h e a t i n g c y c l e s , a r e l a t i v e l y l o w peak w i t h a s m a l l e r t e m p e r a t u r e range i s observed. An a i r - c o o l e d specimen e x h i b i t s a v e r y sharp and much h i g h e r I F peak. These r e s u l t s i n d i c a t e t h a t t h e s t a b i l i z a t i o n due t o quenching below Mf may have been e l i m i n a t e d p a r t i a l l y b y t h e r m a l c y c l e s . An a i r - c o o l e d specimen has a good t h e r m a l
e l a s t i c i t y .
i n t e r a c t i o n between t h e i n t e r f a c e and excess vacancies which a r e produced by quenching. t h e n d i f f u s e t o t h e i n t e r f a c e and p i n it. D u r i n g up-quenching, vacancies and t h e i r c l u s t e r s d i f f u s e away from t h e i n t e r f a c e o r a r e a n n i h i l a t e d p a r t i a l l y so t h a t t h e p i n n i n g e f f e c t o f t h e i n t e r f a c e i s d i m i n i s h e d , l e a d i n g t o r e c o v e r y o f m a r t e n s i t i c t h e r m a l e l a s t i c i t y . When t h e specimen i s up-quenched t o a l o w e r t e m p e r a t u r e o r up-quenched a f t e r b e i n g heated t o a s u f f i c i e n t l y h i g h
t e m p e r a t u r e s l o w l y , t h e c l u s t e r s of vacancies may crumble i n t o a d i s l o c a t i o n l o o p t o p i n t h e i n t e r f a c e t i g h t l y . This t y p e o f d e f e c t cannot be e l i m i n a t e d by up- quenching. t h u s t h e t h e r m a l e l a s t i c i t y o f m a r t e n s i t e cannot he recovered. F o r t h e m a t e r i a l h a v i n g l o w e r Ms, when i t i s c o o l e d f r o m t h e temperature o f s o l i d
s o l u t i o n , p a r t of t h e vacancies a r e a n n i h i l a t e d above
M
,
and cannot aggregate a t t h e i n t e r f a c e and p i n i t s t r o n g l y . Thus, t h e thermal e f a s t i c i t y may be recoveredby subsequent c y c l e s .
JOURNAL DE PHYSIQUE
ACKNOWLEDGEMENT
The a u t h o r s wish t o t h a n k P r o f . Tsao Mingshen f o r h i s g e n e r o s i t y i n s u p p l y i n g t h e CuZnAl samples.
REFERENCES
W. De Jonghe, R. De B a t i s t , L. Delaey and M. De Bonte, i n Sha e Memory
E f f e c t s i n A l l o y s . ed.. J. Perkins, Plenum Press, 1975. -1
W. De Jonghe, R. De B a t i s t and L. Delacy, S c r i p t a M e t a l l . 10 (1976) 1125. S. Koshimizu and W. Benoit. J. de Physique, Colloque C4, S F p l e m e n t No. 12, 43 (1982) C4-679.
J. Van Humbeeck and L. Delaev. J. de Phvsiaue. C o l l o a u e C4. S u ~ o l e m e n t No.
" .
" , .-
, .12,
43
(1982) 691.M. Morin, 6. Guenin and P. F. C o l i n , J. de Physique. C o l l o q u e C4, Supplement No. 12, 43 (1982) 685.
R. G o t t h a r d t , J. de Physique, C o l l o q u e C4, Supplement No. 12, 43 (1982) 667.
A. Abu aArab and Ahlers, J. de Physique, Colloque C4, Supplement No. 17,
43
(1982) 709.
