Phase-field model of interface migration and powder consolidation in additive manufacturing of metals

Consolidation phenomena are of fundamental importance for additive manufacturing since the quality of metal parts produced by selective laser melting (SLM) is greatly dependent on residual porosity. The most recent studies use the lattice Boltzmann method (LBM) to analyze conjugated multiphase flow, heat transport, and phase transitions in the molten zone. A phase-field approach suggested in this paper retains all advantages of LBM and provides an alternative tool for theoretical analysis of SLM. In case of consolidation of composite powders where wetting phenomena are crucial at the matrix-inclusion interfaces, the phase-field method is more suitable. In this paper, the problem of metallic powder consolidation is numerically studied and the dynamics of pore and gas bubbles evolution in the molten zone is described. A two-step mechanism of consolidation is proposed which differs from a single-step mechanism typical for additive manufacturing of polymer powders. The consolidation time for different particle orderings is studied and an algorithm for the parameter selection in the widely used viscoplastic model is derived.