Change of the Fraction Solidified during Solidification of Al-Cu Alloy

Abstract

When the molten metal is freezing unidirectionally by convectional heat transfer of the air, its heat equation can be expressed as follows:
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where h is the heat transfer coefficient, S is the heat transfer area, T is the temperature of sample, T_∞ is the temperature of air at the infinity, M is the weight of sample, C_p is the specific heat at constant pressure, L is the latent heat of sample, t is the time, and f_s is the fraction solidified.
The relation between t and T was obtained from the observed cooling curves of samples. After substituting them into the heat equation, the relation between f_s and T was then calculated by graphically integrating the current equation.
The results obtained were compared with the relation between f_s and T based on the equilibrium solidification or the nonequilibrium solidification proposed by Pfann et al.
It was found that f_s was retarded compared to the two cases mentioned above. This was considered due to the solute built-up in the liquid at the solid-liquid interface during solidification as observed by E.P.M.A.