Monte Carlo simulations of solidification and solid-state phase transformation during directed energy deposition additive manufacturing

Both solidification and phase transformation play key roles in determining the final mechanical properties of Ti–6Al–4V parts fabricated by directed energy deposition (DED) additive manufacturing (AM). A cross-sectional Monte Carlo model is proposed to simulate both solidification and solid-state phase transformations on the cross section of DED parts. Results indicate that the simulated prior β and α grains are both well correlated with experimental observations. An increase in the build height leads to an increase in the grain length during solidification, and α embryos are generated on the boundaries of the formed β grains. The phase transformation is completed between 950 and 800 °C during cooling. The numerical results of the phase transformation agree well with the experimental observations.