Solidification Simulation of Direct Energy Deposition Process by Multi-Phase Field Method Coupled with Thermal Analysis

The multi-phase field method coupled with the thermodynamics database of calculation of phase diagrams has been successfully applied to simulation of solidification microstructure evolutions in engineering casting processes. As multi-phase field method is based on the local (quasi-)equilibrium assumption in solidification theory [1], applying this method to solidification of additive manufacturing processes is not studied enough because of extremely large cooling rate and temperature gradient conditions. On the other hand, some researchers have reported experimental observations of the columnar-to-equiaxed transition in the solidification of the additive manufacturing processes including the direct energy deposition. They suggest that the local (quasi-)equilibrium assumption can be applied to solidification of additive manufacturing processes [2]. In this study, solidification microstructures of titanium alloys in direct energy deposition are calculated by multi-phase field method. Temperature distributions obtained by thermal analyses using finite element method are adapted to multi-phase field method. The microstructure evolution of columnar-to-equiaxed transition is confirmed. The results are summarized in a solidification map for direct energy deposition process conditions.