Metallographie examination of TD-Nickel base alloys
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Liquid Structure SX Sp Chains without permanent neighbors
Thermal* Analysis
X-Ray* Diffraction
MP-393 393461 461-BP
MP-397 397-448/498 448/498-BP
*MP and BP denote the melting and boiling points, respectively.
Table I I I. Temperatu res I K) Associated with the Disappearance of the Second Liquid Structure
Thermal Analysis
X-Ray Diffraction
tin
1400
mercury iridium
1400
1170-1470 277 >920* 323-423
Metal
gallium
Diftktsion Data ~1300 ~277 ~ 1300 ~340
*lligher temperature data unavailable.
Table IV. Ratio of the Integrated Area Under the Subsidiary and Main Peaks of Liquid Tin as a Function of Temperature 4
T, K
Ratio
323 608 773
8.5 5.6 8.7 1.3 1.0
1173
1473
the liquid which is stable at temperatures slightly a b o v e t h e m e l t i n g p o i n t i s c o m p o s e d of r i n g m o l e c u l e s a n d i s k n o w n a s SM On h e a t i n g to a h i g h e r t e m p e r a ture the melt darkens and becomes more viscous. T h i s l i q u i d i s k n o w n a s S~, a n d i s c o n s i d e r e d to c o n t a i n c h a i n s . A p l o t of t h e a v e r a g e n u m b e r of a t o m s in a spherical shell versus the shell radius shows that a r e f e r e n c e a t o m in b o t h t h e SX a n d Sp l i q u i d s h a s two p e r m a n e n t n e i g h b o r s . A t t e m p e r a t u r e b e t w e e n 448 a n d 498 K t h e r e a r e no l o n g e r p e r m a n e n t n e i g h b o r s b e c a u s e of t h e r a p i d m a k i n g a n d b r e a k i n g of c h a i n s . T a b l e II shows that the temperatures determined by thermal a n a l y s i s a r e in e x c e l l e n t a g r e e m e n t w i t h t h e X - r a y measurements of t h e s e s t r u c t u r a l c h a n g e s . The liquid metals possessing two structures for which diffusion data have been reported over a wide t e m p e r a t u r e i n t e r v a l a r e s h o w n in T a b l e III. T h e t e m p e r a t u r e of 1400 K d e t e r m i n e d b y t h e r m a l a n a l y s i s of t i n f o r t h e d i s a p p e a r a n c e of t h e s e c o n d - s t r u c t u r e is i n a g r e e m e n t w i t h t h e d i s c o n t i n u i t y in t h e d i f f u s i o n d a t a ~ a t a b o u t 1300 K. T h e t i n X - r a y d a t a of N o r t h a n d Wagner 4 indicate that the subsidiary peak disappears at slightly lower temperatures ( s e e T a b l e IV). As noted above the slightly lower temperature indicated b y t h e X - r a y d a t a i s p r o b a b l y d u e to t h e r m a l b r o a d e n ing. T h e d i f f u s i o n d a t a t t e n d to s h o w a d i s c o n t i n u i t y a t a b o u t 1300 K, a n d t h e t h e r m a l a n a l y s i s r e s u l t s i n d i cate the second structure dissociates at a temperature of a b o u t 1400 K. H i g h e r t e m p e r a t u r e i n d i u m d i f f u s i o n r u n s w o u l d b e n e c e s s a r y to c o n c l u s i v e l y d e m o n s t r a t e 1296-VOLUME 6A, JUNE 1975
a n i n c r e a s e in t h e d i f f u s i o n c o e f f i c i e n t , b u t s u c h d a t a c o u l d n o t b e r e l i a b l y d e t e r m i n e d b e c a u s
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