Numerical Model for Simulation of Melting and Microstructure Evolution during a Multi-layered Laser Melting Process

In this paper, a numerical model is presented for the simulation of melting and microstructure formation during a layer-by-layer laser melting process. The model couples the solution of thermal and species transport with a sharp-interface enthalpy-based phase change model to track the melting and solidification in each layer. The effect of the moving laser energy source is implemented through a transient moving heat flux boundary condition. Transition from the completion of a layer to the start of a new layer is implemented using a domain translation technique, keeping the size of the computational domain constant. The model captures the remelting of a previous layer during the formation of a new layer. Simulations are performed to predict the segregation and grain structure formation during multi-layered laser melting of Al-10%Cu alloy. It is seen that the laser scan direction governs the grain orientation with grains growing in the direction of laser travel. Also, the remelting of the previously formed grains in the adjacent layer affects the species concentration and grain structure in the subsequent layer. Higher power, lower laser scan speed, and smaller laser radius leads to the formation of longer grains with larger aspect ratio spanning multiple layers.