Study on grain size of deposition layer in single-layer laser melting deposition additive manufacturing on Invar alloy

The laser melting deposition (LMD) process is utilized to fabricate single-layer single-pass samples of Invar alloy in the current study. The relationship between heat input and microstructure characteristics is investigated through simulation and experimental methods. A three-dimensional finite-element model is established to research the grain size and microstructure of deposition layer, combined with temperature distribution during the LMD process. Meanwhile, considering the influence of thermal history on grain growth, the thermal cycle curves during the LMD process are produced on the strength of the simulation results. It is explicit that, comparing the variation trends of grain size, the grain growth in the Y direction obtains a further advantage in competitive growth with heat input from 812 to 2300 J / cm2. In addition, simulation results indicate that temperature gradient shows some disparity in the X and Y directions, which generates difference of grain size in two directions.