Prediction of the microstructure, resultant phases and hardness of additively manufactured Ti6Al4V

A multi-physics model developed is used to investigate the transport phenomena, subsequent microstructure and phase evolution and resultant hardness in the directed energy deposition process. A physics-based computational fluid dynamics model with an improved level-set method is built to simulate the heat/mass transport and the dynamic evolution of the molten pool surface on the macro-scale. The resultant microstructural grain morphology and phase compositions are predicted based on the three dimensional temperature and cooling rates calculated during the solidification processes using a three dimensional cellular automata model and a computationally efficient novel cellular automata-phase field model. In addition, the solid state phase transformation due to repeated heating and cooling of solidified regions during multi-track and multi-layer deposition is also modeled. The modeling results are validated against the experiments, and the predicted geometry, grain morphology and phases of deposited tracks match well with the experimental results. The effects of the processing parameters on the track geometry and microstructure are also investigated. The developed integrated modeling tools will allow effective design of process parameters to achieve desired microstructure and mechanical properties.