Solidification rate in rapid conduction cooling
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INCREASING attention has recently been paid on the method of splat cooling in producing new crystalline and non-crystalline phases which are not obtainable by conventional techniques. The method of splat cooling, x though there are many variations in details, is characterized by the rapid cooling of small amount of liquid material by heat extraction into a cooled substrate by conduction. Quantitative calculations of cooling rate in splat cooling were performed by Ruhl2 who analyzed the effects of some ten variables on cooling rate. In order to properly evaluate the ability of splat cooling to produce new structures, however, it appears necessary to estimate not only the average rate of cooling but also the rate of advancement of solid-liquid interface, the solidificationrate. The purpose of this paper is to present the results of calculations of solidificationrate based on the heat flow balance during splat cooling and to show how the c a l c u l a t e d r e s u l t s can be c o m p a r e d with the r a t e of c r y s t a l l i z a t i o n which m a y b e e s t i m a t e d f r o m the m o l e c u l a r k i n e t i c c o n s i d e r a t i o n s . F r o m such c o m p a r i sons it is p o s s i b l e to e s t i m a t e the k i n e t i c u n d e r c o o l ings in the liquid at the s o l i d - l i q u i d i n t e r f a c e . A knowledge of such u n d e r c o o l i n g s should p e r m i t the q u a n t i t a tive a s s e s s m e n t s of the e f f e c t i v e n e s s of individual splat cooling e x p e r i m e n t . CALCULATION OF SOLIDIFICATION RATE BASED ON THE HEAT FLOW BALANCE
where T = temperature t = time x = p o s i t i o n v a r i a b l e as indicated in Fig. I = t h e r m a l diffusivity Initial and b o u n d a r y conditions a r e , T ( x , O) = T b
x
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