Design of mechanical properties of Al-alloys chill castings based on the metal/mold interfacial heat transfer coefficient

Abstract

Solidification thermal parameters such as the growth rate and the cooling rate depend on the metal/mold heat transfer efficiency, usually characterized by an interfacial heat transfer coefficient, h i , and determine the arrangement of the solidification microstructure, including its morphology and scale. The mechanical properties can be correlated with the microstructural parameters such as the cellular and dendritic spacings and hence with the instantaneous value of h i . In the present investigation, it is shown that h i varies in time according to an expression of the form h i = a t − m , where m < 0.5. Directional solidification experiments are carried out, and interrelations of thermal parameters, microstructure and tensile properties are established. Linear relationships between the ultimate tensile strength and h i have been determined for hypoeutectic Al–Fe and Al–Sn alloys.