HAL Id: jpa-00225338
https://hal.archives-ouvertes.fr/jpa-00225338
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.
INTERNAL FRICTION DUE TO dHCP-FCC
TRANSFORMATION OF LANTHANUM
Pan Zhengliang, Li Guangyi, Wang Xiaowei, Xiao Jinquan
To cite this version:
INTERNAL FRICTION DUE TO dHCP-FCC TRANSFORMATION OF LANTHANUM
PAN ZHENGLIANG, LI GUANGYI, WANG XIAOWEI AND XIAO JINQUAN
I n s t i t u t e
of
M e t a l R e s e a r c h , Academia S i n i c a , S h e n y a n g , C h i n a
A b s t r a c t - The i n t e r n a l f r i c t i o n , r e l a t i v e s h e a r modulus and magnetic su- s c e p t i b i l i t y of La a s a f u n c t i o n of t e m p e r a t u r e have been measured i n t h e r a n g e 80-700K. The mechanism of phase t r a n s f o r m a t i o n FCC-double HCP of La is d i s c u s s e d .
I-INTRODUCTION
The a p p l i c a t i o n s of r a r e e a r t h m e t a l s g r e a t l y depend on o u r knowledge a b o u t t h e s t r u c t u r e and p r o p e r t i e s of t h i s k i n d of m e t a l / I / . I n t e r n a l f r i c t i o n i s a v e r y u s e f u l and s e n s i t i v e method f o r i n v e s t i g a t i n g t h e s t r u c t u r e s and d e f e c t s of m e t a l s . But a v a i l a b l e i n t e r n a l f r i c t i o n d a t a f o r r a r e e a r t h m e t a l s a r e l i m i t e d . A b r i e f r e v i e w a b o u t t h e o n l y a few p a p e r s was g i v e n by S c o t t / 2 / . The p r e p a r a t i o n and b a s i c p r o p e r t i e s / 3 / and magnetic and t r a n s p o r t p r o p e r t i e s
/ 4 /
of r a r e e a r t h m e t a l s were c o l l e c t e d i n Handbook on t h e P h y s i c s and Chemistry of Rare E a r t h s .11-EXPERIMENT PROCEDURE
The l a n t h a n u m w i r e s o f 9 9 . 8 X p u r i t y w i t h 1 t o 2 mm i n d i a m e t e r were used i n t h i s i n - v e s t i g a t i o n . The o r i g i n a l La w i r e s were a n n e a l e d i n a vacuum f u r n a c e of Pa a s f o l l o w i n g p r o c e d u r e : 1023K 1 . 5 h and 573K 2h and 423K 0.5h t h e n cooled t o room t e m p e r a t u r e .
The i n t e r n a l f r i c t i o n Q-' and r e l a t i v e s h e a r modulus which i s p r o p o r t i o n a l t o t h e s q u a r e of t h e v i b r a t i o n f r e q u e n c y F' were determined ,in a n a u t o m a t i c i n v e r t e d t o r - s i o n pendulum. I n s i d e t h e pendulum a s t a t i c p r e s s u r e of 200 Pa helium was main* t a i n e d a f t e r pumping t o Pa. The measurement e r r o r o f Q - l and F~ were l e s s t h a n 1% and 0.01% r e s p e c t i v e l y . The magnetic s u s c e p t i b i l i t y
x
was determined i n a F o r c e Magnetometer Geoge A s s o c i a t e s 3000 VT S e r i e s . The mass of a specimen was 0.3g and t h e i n t e n s i t y of magnetic f i e l d used was 5000 Oe. The e r r o r ofx
was l e s s t h a n 1%.111- EXPERIMENTAL RESULTS
1) I n t e r n a l F r i c t i o n and Modulus i n 400-700K. 2
Q-I and F of t h e a n n e a l e d La a s a f u n c t i o n of measuring t e m p e r a t u r e T i n t h e r a n g e 400-700K d u r i n g f i r s t and f i f t h t h e r m a l c y c l e a r e shown i n F i g . 1 and 2 r e s p e t i v e l y . The c u r v e s , w h i c h i n d i c a t e d by a n a r r o w from h i g h t o low t e m p e r a t u r e , d u r i n g k o o l i n g
C10-614
JOURNAL DE PHYSIQUE
i n t h e b o t h f i g u r e s a p p e a r two i n t e r n a l f r i c t i o n peaks C1 and C2. The c u r v e d u r i n g h e a t i n g i n Fig.2 a p p e a r s a l s o two peaks H1 and H
,
a l t h o u g h t h e r e i s o n l y one peak H1 i s i n F i g . 1.
It i s c l e a r from F i g . 1 and 2 t 2 a t t h e i n t e r n a l f r i c t i o n peaks can be i n f l u e n c e d by t h e t h e r m a l c y c l e s and by t h e h i g h e s t t e m p e r a t u r e t o which t h e s p e c i - men was h e a t e d i n l a s t thermal c y c l e . The t e m p e r a t u r e of peak H I , C 2 were appre- c i a b l y d e c r e a s e d and t h e h i g h t of peak C i was i n c r e a s e d b u t peak C2 was r e l a t i v e l y d e c r e a r e d a f t e r f i v e t h e r m a l c y c l e s . I f t h e sample La was o n l y h e a t e d t o 550K and s a b s e q u e n t l y c o o l e d , t h e n no peak may be observed i n t h e t e m p e r a t u r e r a n g e of peak C1 and C2. For t h e mentioned peaks t h e f o l l o w i n g c h a r a c t e r i s t i c f e a t u r e s of t h e i n t e r n a l f r i c t i o n due t o phase t r a n s f o r m a t i o n have been observed. F i r s t , t h e h e i g h t of t h e peaks depends on t h e r a t e of h e a t i n g and c o o l i n g . Second, thermal h y s t e r e s i s i s c l e a r l y shown i n F i g . 1 and 2 , which t h e t e m p e r a t u r e of peak HI i s h i g h e r t h a n t h a t t e m p e r a t u r e of c o r r e s p o n d i n g peak C7. F i n a l l y , t h e peak tempera- t u r e i s independent of t h e f r e q u e n c y used i n t h e measurement. It i s c o n s i d e r e d t h a t t h e peaks H1, H2,C1 and C2 i s a s e t ef i n t e r n a l f r i c t i o n peak due t o phase t r a n s f o r m a t i o n .It i s viewed t h a t t h e t e m p e r a t u r e dependence of r e l a t i v e s h e a r modulus i s a s s o c - i a t e d w i t h peaks H1 and C2 i n F i g . 1 and 2 .
2) Magnetic S u s c e p t i b i l i t y
The t e m p e r a t u r e dependence of rpagnetic s e e c e p t i h i l i t y
x
and1 / x
of unannealing La d u r i n g t h e second h e a t i n g a r e shown i n Fig.3. It i s c l e a r t h a t t h e Curie-WeissI2w i s followed. The i n t e r s e c t i o n p o i n t of t h e l i n e s L and L2 i s about 530K. which is c o r r e s p o n d i n g t o t h e t e m p e r a t u r e of phase t r a c s g o r m a t i o n of La from d o u b l e HCP s t r u c t u r e t o FCC s t r u c t u r e 131.
3 ) I n t e r n a l f r i c t i o n spectrum i n 80-450K
For t h e o r i g i n a l specimen La f o u r i n t e r n a l f r i c t i o n peaks l a b e l e d a s H3, H4, H5 and H6 a r e r e s p e c t i v e l y observed i n t h e t e m p e r a t u r e r a n g e 80-450K a s shown i n F i g . 4 , However o n l y t h r e e H3, H5 and H6 of them a p p e a r i n t h e f i r s t r u n
.
The peak Hq may be o n l y observed a f t e r s e v e r a l r u n s o r a f t e r a s p e c i a l a n n e a l i n g t r e a t m e n t . The peak H5 is a t y p i c a l r a l a x a t i o n p r o c e s s w i t h a c t i v a t i o n e n t h a l p y 0.35 eV, which can be o b t a i n e d from A r r h e n i u s e q u a t i o n by measuring t h e peak t e m p e r a t u r e i n v a r i o u s f r e q u e n c y . The f e a t u r e s of r e l a x a t i o n was a l s o appeared i n t h e t e m p e r a t u r e depen- dence of r e l a t i v e s h e a r modulus (F2).
The peak H i s dependent on c o l d work de- g r e e and a n n e a l i n g t e m p e r a t u r e . A c o l d worked sample La w i t h r e d u c t i o n of a r e a 10% was a n n e a l e d a t 400K 1 0 min and t h e i n t e r n a l f r i c t i o n of t h e samples was measured d u r i n g h e a t i n g from l l O K . A symmetric peak H was appeared a s Fig.5. The h i g h of5
peak H was d e c r e a s e d w i t h i n c r e a s i n g t h e a n n e a l i n g t e m p e r a t u r e o v e r 450K. It seems t h a t tl?e peak H5 might be presumably a s s o c i a t e d w i t h t h e i n t e r a c t i o n between t h e d i s l o c a t i o n s and i n t e r s t i t i a l s o l u t e atoms i n a s p e c i a l phase e . g . d o u b l e HCP s t r u c - t u r e .
IV
-
DISCUSSIONI t i s shown / 3 , 5 / t h a t t h e phase t r a n s f o r m a t i o n of La from FCC s t r u c t u r e t o d o u b l e HCP s t r u c t u r e i s t a k e n p l a c e a t about 530K d u r i n g c o o l i n g and t h e o p p o s i t e t r a n s - f o r m a t i o n a t a b o u t 580K. I t i s a 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 .
A d i s l ~ c a t i o p ~ ~ o d e of t r a n s f o r m a t i o n FCC-dHCP of La was proposed by Marcinkowski and Hopking a c c o r d i n g t o some r e s u l t s of e l e c t r i c r e s i s t i v i t y and e l e c t r o n microscope. But i t i s d i f f i c u l t t o e x p l a i n t h e two i n t e r n a l f r i c t i o n peaks of La due t o t h e t r a n s f o r m a t i o n dHCP-FCC.
(FCC). It i s p r e s u m a b l y s u g g e s t e d t h a t t h e embryo o f HCP s t r u c t u r e o f La i s f i r s t formed a t t h e s t a c k i n g f a u l t o f FCC s t r u c t u r e d u r i n g c o o l i n g a n d grown and t r a n s - formed t o d o u b l e HCP s t r u c t u r e d u r i n g c o n t i n u a l c o o l i n g , s o t h a t t h e t r a n s f o r m a t i o n y-B (and B-y) o f La h a s t o i n c l n d e a t r a n s i e n t p h a s e which i s HCP s t r u c t u r e i n o r d e r t o d e c r e a s i n g t h e f r e e e n e r g y o f t h e p h a s e t r a n s f o r m a t i o n . T h e r e e x i s t two t r a n s f o r m a t i o n p r o c e s s e s . The p r e t r a n s f o r m a t i o n i s from dHCP t o HCP d u r i n g h e a t i n g and from FCC t o HCP d u r i n g c o o l i n g w h i c h a r e r e s p e c t i v e l y c o r r e s p o n d i n g t o i n t e r n a l f r i c t i o n p e a k s Hg and C1. The p e a k s H1 and C2 c o r r e s p o n d t o t h e s e c o n d p r o c e s s o f t r a n s f o r m a t i o n w h i c h i s from HCP t o FCC d u r i n g h e a t i n g and from HCP t o dHCP d u r i n g c o o l i n g . Then t h e s t a r t and f i n a l t e m p e r a t u r e o f t h e two p r o c e s s e s o f p h a s e t r a n s - f o r m a t i o n B-y ( a n d y-6) o f La c a n b e o b t a i n e d from t h e t e m p e r a t u r e r e g i o n o f t h e i n t e r n a l f r i c t i o n p e a k s , a s T a b l e I . The d a t a from e l e c t r i c r e s i s t i v i t y / 5 / i s a l s o l i s t e d i n T a b l e 1 f o r c o m p a r i n g w i t h e a c h o t h e r . But n o p r e t r a n s f o r m a t i o n was o b s e r v e d i n e l e c t r i c r e s i s t i v i t y e x p e r i m e n t . T a b l e I 6-y t r a n s f o r m a t i o n t e m p e r a t u r e o f La, K h e a t i n g As Af method dHCP-HCP 4 7 0 5 0 5 5 0 5 0 i n t e r n a l f r i c t i o n ( p e a k Hz) HCP-FCC 5 5 0 5 0 6 5 0 5 0 i n t e r n a l f r i c t i o n ( p e a k HI) dHCP-FCC 573 610 e l e c t r i c r e s i s t i v i t y / 5 / C o o l i n g M, M,
.
FCC-HCP 6 2 0 5 0 48055 i n t e r n a l f r i c t i o n ( p e a k C1) HCP-dHCP 4 8 0 f 5 4 1 0 t 5 i n t e r n a l f r i c t i o n ( p e a k C2) FCC-dHCP 4 7 7 423- e l e c t r i c r e s i s t i v i t y / 5 / A i n t e r n a l f r i c t i o n c u r v e s o f La w i t h p u r i t y 98% was r e p o r t e d by R e f . / 7 / . Only a p e a k,
w h i c h p e a k t e m p e r a t u r e was 620 K d u r i n g h e a t i n g and 570K d u r i n g c o o l i n g , a n d a f e w d a t a p o i n t s w e r e m e a s u r e d i n t h e r a n g e 470-670K. Now it i s seemly c o n s i d e r e d t h e i r e x p e r i m e n t r e s u l t s are q u e n s t i o n a b l e.
REFERENCE / I / K.A.Gschneidner J r . J . L e s s Common M e t a l s *(1984), 1./ 2 / T . E . S c o t t , Handbook o n t h e p h y s i c s and C h e m i s t r y o f R a r e E a r t h s , e d . by K.A. G s c h n e i d n e r J r . and L . R . E y r i n g , N o r t h - H o l l a n d P u b l i s h i n g Co. 1 9 7 8 , Amsterdam, Vol.1, p . 5 9 1 .
/ 3 / B.J.Beaudy and K.A.Gschneidner J r k i b i d , p . 1 7 3 .
1 4 1 K.A.McEwen, i b i d , P.411.
/ 5 / M.J.Narcinkowski a n d E.N.Hopkins, T r a n s . M e t . S o c . AIHE, *(1968)579. / 6 / J . F r i e d e 1 , D i s l o c a t i o n s , Pergamon P r e s s , 1 9 6 4 , O x f o r d , P.138. / 7 / D a s h k o v s k i y , A.I. and S a v i t s k i y , E.M.Net. i M e t a l l . C h i s t y k h
