Multi-scale simulation of grain growth during laser beam welding of nickel-based superalloy

A multi-scale model integrating a macro-scale finite element model and micro-scale phase field models is proposed to simulate the grain growth in the molten pool of laser beam welding of the Inconel 718 alloy. The calculated welding profile using the macro-scale model agrees well with experimental measurements. According to the calculated macro-scale temperature field, the temperature gradient G, the solidification rate R in the molten pool are calculated. The micro-scale phase field models of macro-scale G and R are coupled are used to simulate the grain growth in the molten pool. Simulated columnar grains are dendritic, which gives agreements with experimental observations. The simulation results and experimental measurements show that the columnar grains spacing increases slightly from the fusion edge to the weld. A power-law function of λ s ∝(G × R) −0.433 is found from the simulation results, which is similar to the power-law function of λ s ∝(G × R) −0.431 from the experimental measurements. Simulated microstructural patterns of the competitive growth match experimental findings well. The spacing of favorable oriented grains is a bit larger than that of unfavorable oriented grains in the competitive growth.