Multi-track, multi-layer dendrite growth and solid phase transformation analysis during additive manufacturing of H13 tool steel using a combined hybrid cellular automata/phase field, solid-state phase prediction models

Using an efficient hybrid Cellular Automata/Phase Field (CA-PF) dendrite growth model in combination with a solid-state phase transformation model, microstructure evolution and solid-state phase transformation were predicted during laser direct deposition (LDD) of H13 tool steel powder within a large domain across multiple deposition tracks and layers. Temperature and surface geometry data were provided by a comprehensive physics-based laser deposition model. The computational efficiency of the CA-PF model allows for simulating domains large enough to capture dendrite growth across an entire molten pool and into multiple neighboring LDD tracks and layers. The microstructure of the target track is strongly affected by heat from neighboring tracks including re-melting, re-solidification and solid-state phase transformation including austenitization, martensite formation and martensite tempering. Dendrite size and growth direction across the entire fusion zone, as well as predicted hardness values, are found to be in good agreement with experimental results.