PRESSURE EFFECT ON PREMELTING TRANSITION IN A TILT GRAIN BOUNDARY IN AN Fe-Si ALLOY

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PRESSURE EFFECT ON PREMELTING

TRANSITION IN A TILT GRAIN BOUNDARY IN AN Fe-Si ALLOY

L. Shvindlerman, W. �ojkowski, E. Rabkin, B. Straumal

To cite this version:

L. Shvindlerman, W. �ojkowski, E. Rabkin, B. Straumal. PRESSURE EFFECT ON PREMELTING

TRANSITION IN A TILT GRAIN BOUNDARY IN AN Fe-Si ALLOY. Journal de Physique Colloques,

1990, 51 (C1), pp.C1-629-C1-634. �10.1051/jphyscol:1990199�. �jpa-00230368�

COLLOQUE D E PHYSIQUE

Colloque Cl, supplement au n o l , Tome 51, janvier 1990

PRESSURE EFFECT ON PREMELTING TRANSITION IN A TILT GRAIN BOUNDARY IN AN Fe-Si ALLOY

L.S. SHVINDLERMAN, W. Z O J K O W S K I * , E.I. RABKIN and B.B. STRAUMAL' Academu of Science of the URSS, Institute of Solid State Physics, f 42432-~hernogolowka, U. R. S. S.

UNIPRESS, High Pressure ~ e s e a r c h Centre, Sokokowska 29, 01-142 Warsaw, Poland

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w e r e p r e d i c t e d by C a h n ( 1 1 ) f o r t w o c o m p o n e n t f l u i d in c o n t a c t w i t h s o l i d . T h e p h a s e t r a n s i t i o n s o n i n t e r f a c e s c a n c l a s s i f f i e d a n a l y s i n g t h e f r e e e n e r g y of t h e w e t t i n g layer ( 1 1 ) :

H e r e c,, is t h e s u r f a c e tensicsn of t h e i n t e r f a c e b e t w e e n t h e c r y s t a l a n d t h e w e t t i n g p h a s e , 1 is t h e t h i c k n e s s of t h e w e t t i n g l a y e r , Ag is t h e e x c e s s b u l k f r e e e n e r g y of t h e w e t t i n g p h a s e a n d f ( 1 ) d e s c r i b e s t h e i n t e r a c t i o n of t h e t w o o p p o s i t e i n t e r f a c e s b e t w e e n t h e c r y s t a l s a c r o s s t h e w e t t i n g p h a s e ( f i g . 1 ) .

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It h a s to b e p o i n t e d o u t t h a t c,, in g e n e r a l may d e n o t e t h e e n e r g y of a n y i n t e r f a c e b e t w e n t h e w e t t i n g p h a s e a n d t h e a d j o i n i n g g r a i n s , e v e n i f t h e w e t t i n g p h a s e is s o l i d . W e h a v e a d d o p t e d t h e LS s u b s c r i p t b e c a u s e in t h e b e l o w p r e s e n t e d c a s e w e s h a l l c o n s i d e r t h e " p r e m e l t i n g " p h a s e t r a n s i t i o n , w h e r e t h e G B b e c o m e s w e t t e d by

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990199

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In o u r p r e v i o u s work (18,12) w e h a v e s t u d l e d t h e p e n e t r a t i o n of l i q u i d z i n c a l o n g synbmetrical t i l t G B s in a n F e - 5 a t X S i a l l o y . W e o b s e r v e d t h e f o r m a t i o n of a G B g r o o v e w i t h a d i h e d r a l a n g l e O

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Z i n c d i f f u s e d a l o n g t h e t i l t a x i s o f t h e G e s . C l o s e t o t h e g r a i n b o u n d a r y g r o o v e G B d i f f u s i o n c o e f f i c i e n t s of Z n w e r e by t w o o r d e r s of m a g n i t u d e h i g h e r t h a n in t h e r e g i o n m o r e d i s t a n t from t h e g r o o v e a n d of lower Z n c o n c e n t r a t i o n . W e a s s u m e d a G B p r e m e l t i n g t r a n s i t i o n t o o c c u r f o r Z n c o n c e n t r a t i o n s e x c e e d i n g a v a l u e c w . F o r t h e p r e m e l t i n g t r a n s i t i o n a c h a n g e of s p e c i f i c v o l u m e of t h e G B s h o u l d t a k e p l a c e . H e n c e , t h e parame'ter &g c o n t r o l l i n g t h e t h i c k n e s s of t h e w e t t i n g l a y e r s h o u l d b e p r e s s u r e d e p e n d e n t . T h e p u r p o s e of t h e p r e s e n t work w a s t o a p p l y h i g h p r e s s u r e s a s a n a d d i t i o n a l t h e r m o d y n a m i c p a r a m e t e r in o r d e r t o o b t a i n m o r e i n s i g h t in t h e n a t u r e of t h e a b o v e p h a s e t r a n s f o r m a t i o n ,

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w h e r e n, i s t h e n u m b e r of a t o m s in u n i t of s u r f a c e of o n e a t o m i c layer o n g r a i n b o u n d a r y , n is t h e n u m b e r of a t o m i c l a y e r s in g r a i n b o u n d a r y , K is t h e c o n c e n t r a t i o n of Z n a t o m s in t h e g r a i n b o u n d a r y . C o m b i n i n g e q s . C 3 - 5 ) o n e o b t a i n s :

T h e p h y s i c a l i n t e r p r e t a t i o n of e q , ( 6 ) is a s f o l l o w s : I f p r e m e l t i n g is a s s o c i a t e d w i t h r e p l a c i n g i r o n in t h e g r a i n b o u n d a r y w i t h a Z n r e a c h p h a s e of h i g h e r s p e c i f i c v o l u m e t h a n F e , t h e n t h e g r a i n b o u n d a r y p h a s e transition s h o u l d b e s u p p r e s s e d u n d e r p r e s s u r e p,.

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K i k u c h i R , , C a h n J , W , , P h y s . R e v . , B 3 6 1 9 8 7 ) 4 1 8

C o u n t e r m a n C . , C h e n L . - Q , , K a l o n j i G., J . d e P h y s i q u e CS, 4-2 619383 139

S i c k a f u s # . E , , S a s s S . L . , Ac ta M e t . , 35 ( 1 9 8 7 )

H s i e h T . E . , B a l l u f f i R . W . , A c t a M e t . , 37( 1989) 2 1 3 3 Vul E . M . , Z a v a r i t s k a j a , J E T P L e t t . , 3 2 ( 1 9 8 3 ) 571

H a i k i n M . S . , H l u s t i k o v I . N , , J E T P L e t t . , 53, i19&1

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R a b k i n E . I . , S h v i n d l e r m a n , L . S . , S t r a u m a l B . B . , J . L e s s C o m m o n M e t a l s , 11989) in p r e s s

De G e n n e s P . G . , , R e v . of M o d , P h y s ,

a,

D i e t r i c h S , in " P h a s e T r a n s i t i o n s a n d C r i t i c a l P h e n o m e n a " , e d s . D o m b C , a n d L e b u w i t z J . , A c a d . P r e s s , L o n d o n (1988) p . 1 - 2 1 8 C a h n J . W . , J . C h e m . P h y s . fSlL ( 1 9 7 7 ) 3 6 6 7

R a b k i n E . I . , S h v i n d l e r m a n L . S . , S t r a u m a l B . B . , A c t a M e t . , in p r e s s

M e t a l s R e f e r e n c e B o o k . E d , by S m i t h e l s C.I., B u t t e r w o r t h s , L o n d o n C 1 9 7 6 ) .