The correlation between thermal variables and secondary dendrite arm spacing during solidification of horizontal cylinders of Sn-Pb alloys

The control of the microstructure during solidification is of great importance because it dictates the degree to which the material has to be worked subsequent to casting before the required mechanical property specifications can be met. In particular, it is well known the important influence of segregate spacings, i.e., dendrite arm spacings on mechanical properties of cast alloys. In this study, directional solidification experiments in a cylindrical chilled mould have been carried out on Sn-Pb alloys under different melt superheats. The transient metal/mould heat transfer coefficients were determined by a numerical-experimental fit of casting thermal profiles based on inverse heat transfer calculations. Experimental equations correlating heat transfer coefficients as a power function of time are proposed. The response of secondary dendrite arm spacing due to variation in growth conditions during radial solidification was also investigated.