Phase Field Modeling of Melting, Resolidification, and Elastic Response of Metallic Powder-Substrate Interaction in Selective Laser Melting

Selective laser melting of metallic powders has been broadly applied in additive manufacturing process for building complicated parts that are otherwise difficult to manufacture by conventional methods. However, the control of surface quality and elimination of defects in AM produced parts is of a great challenge due to incomplete melting of powders and gas entrapment in the AM process. There is a great need of resolving the small scale process dynamics at the powder level. We present the interplay of solid-liquid phase transition, interfacial deformation, thermal capillary flow, and thermal elasticity involved in powder-substrate interaction upon selective laser melting. A phase field formulation is derived from irreversible thermodynamics to describe the transient evolution of three phases in a 2D space. By considering the temperature dependent material properties, the dynamics of phase transition and interfacial deformation during the fusion process are resolved computationally along with transient temperature distribution and the thermal stress in the substrate. The integrated modeling framework has captured the thermal fluid-structure interactions during the laser melting process, and can be extended to interactions of many powders for the prediction of surface defects.