Substructure control by solidification control in cu crystals
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s t a l and e n c l o s e d in a m u l l i t e tube e v a c u a t e d to 10 -a t o r r , Fig. 1. Solidification is a c c o m p l i s h e d by moving A K a n t h a l - w o u n d f u r n a c e p a r a l l e l to the c r y s t a l axis b y m e a n s of a v a r i a b l e speed m o t o r . Solidification r a t e s (furnace speeds) v a r y f r o m 1.1 to 730 c m / h .
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Solidification All copper c r y s t a l s a r e grown in the (111) o r i e n t a tion by a modified B r i d g e m a n method in a high p u r i t y (National C a r b o n type AUC) graphite s p l i t mold f r o m 99.999+ pet p u r e Cu ( A m e r i c a n Smelting and Refining Company). The mold is p l a c e d on a w a t e r cooled p e d H. AKITA and D. S. SAMPAR,formerly with Department of Metallurgical Engineeringand Materials Sciences, University of Notre Dame, Notre Dame, Ind. 46556, are now with The Research Institute, Fumkawa Electric Co., Tokyo, Japan and the U. S. Army, respectively. N. F. FIORE is Professor of MetallurgicalEngineeringand Materials Science, University of Notre Dame. Manuscript submitted July 18, 1972. METALLURGICALTRANSACTIONS
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COOLINGPEDESTAL Fig. 1--Hard mold with sleeve and thermocouple )ositions. VOLUME 4, JUNE 1973-1593
The c r y s t a l s a r e right c i r c u l a r c y l i n d e r s 1 cm in d i a m e t e r by 15 cm in length and a r e s e e d e d with (111) c r y s t a l s 0.5 cm in d i a m e t e r by 4 cm in length. P r e l i m i n a r y e x p e r i m e n t s with seed c r y s t a l s of v a r i o u s dislocation s u b s t r u c t u r e s indicate that for the conditions of these e x p e r i m e n t s , c r y s t a l s u b s t r u c t u r e is independent of seed s u b s t r u c t u r e . Moreover, in an effort to Insure that s e e d - r e l a t e d effects a r e not influencing r e s u l t s , a l l runs d i s c u s s e d in this p a p e r a r e made with seed c r y s t a l s cut from the s a m e p a r e n t seed. The t e m p e r a t u r e of the furnace is maintained to • 3~ during c r y s t a l growth by a t i m e - p r o p o r t i o n i n g c o n t r o l l e r with thermocouple sensing. The constancy of t e m p e r a t u r e and t e m p e r a t u r e g r a d i e n t s is an i m p o r t a n t feature of these e x p e r i m e n t s since many c r y s tal growth studies a r e made with the furnace o p e r a t i n g at steady state. In such studies, as the furnace or mold is moved, the t h e r m a l load on the furnace changes, and its o p e r a t i n g t e m p e r a t u r e and t e m p e r a t u r e g r a d i ents change during the c o u r s e of c r y s t a l growth. The t e m p e r a t u r e s and t e m p e r a t u r e g r a d i e n t s at v a r i ous posittbns in the mold a r e m e a s u r e d i m m e d i a t e l y before the furnace ts moved upward. The m e a s u r e ment is a c c o m p l i s h e d by the t h e r m o c o u p l e s entering the s
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