A Bézier curve fit to melt pool geometry for modeling additive manufacturing microstructures

This work describes a Metropolis Monte Carlo model for modeling additively manufactured metallic microstructures which employs Bézier curves to formulate melt pool geometry induced by a moving laser heat source. With this formulation, a wide range of melt pool geometries can be modeled and their effects on microstructure morphologies can be evaluated. Melt pool geometries are fit with Bézier curves using melt pool dimensions of width, length, and depth obtained from FEM calculations of the thermal process. Assuming a steady state pool geometry, microstructures are simulated incrementally in the heat affected zone in much the same way an additively manufactured material part is built. The approach is computationally tractable as microstructure simulation is only required in the fusion and heat affected zones, thus requiring less computational resources than would be needed if the entire material/part domain was taken into account. Using the model, microstructures are simulated for LENS™ processed stainless steel. Demonstrations show the model can replicate microstructure morphologies seen in electron beam backscatter diffraction data.