Simulation of temperature, stress and microstructure fields during laser deposition of Ti–6Al–4V

We study the evolution of prior columnar $\beta$ phase, interface $L$ phase, and $\alpha$ phase during directional solidification of a Ti-6Al-4V melt pool. Finite element simulations estimate the solidification temperature and velocity fields in the melt pool and analyze the stress field and thermal distortions in the solidified part during the laser powder bed fusion process. A phase-field model uses the temperature and velocity fields to predict the formation of columnar prior-$\beta$(Ti) phase. During the solidification of $\beta$ phase from an undercooled liquid, the residual liquid below the solidus temperature within the $\beta$ columns results in $\alpha$ phase. The finite element simulated stress and strain fields are correlated with the length scales and volume fractions of the microstructure fields. Finally, the coalescence behavior of the $\beta$(Ti) cells during solidification is illustrated. The above analyses are important as they can be used for proactive control of the subsequent modeling of the heat treatment processes.