Phase-field simulation of secondary dendrite growth in directional solidification of binary alloys

Abstract

Phase field method was used to simulate the effect of grains orientation angle θ11 and azimuth θA of non-preferentially growing dendrites on the secondary dendrites of preferentially growing dendrites. In the simulation process, two single-factor influence experiments were designed for columnar crystal structures. The simulation results showed that, when θ11 < 45° and θA < 45°, as θ11 was enlarged, the growth direction of the secondary dendrites on the preferentially growing dendrites at the converging grain boundary (GB) presented an increasing inclination to that of preferentially growing dendrites; with increasing θA, the growth direction of the secondary dendrites on the preferentially growing dendrites at the converging GB exhibited greater deflection, and the secondary dendrites grew with branches; the secondary dendrites on the preferentially growing dendrites at diverging GBs grew along a direction vertical to the growth direction of the preferentially growing dendrites. When θA = 45° and θ11 = 45°, the secondary dendrites grew in a direction vertical to the growth direction of preferentially growing dendrites. The morphologies of the dendrites obtained through simulation can also be found in metallographs of practical solidification experiments. This implies that the effect of a grain’s orientation angle and azimuth of non-preferentially growing dendrites on the secondary dendrites of preferentially growing dendrites does exist and frequently appears in the practical solidification process.