The simulation of microstructural evolutions in friction stir additive manufacturing

Both recrystallization and solid state phase transformation take key role for the determination of final mechanical properties in friction stir additive manufacturing (FSAM) of titanium alloy. Monte Carlo model is developed to simulate the microstructural changes and a two scale strategy is used to simulate both the recrystallization and the solid state phase transformation in FSAM of duplex titanium alloy. Results indicate that the selection of the building direction can lead to different temperature variations in FSAM due to the different heat accumulations. Lower temperature leads to lower cooling rate in FSAM. This is the reason that the volume fraction of α phase is decreased when the process temperature is decreased. Higher temperature leads to the formation of bigger grains when the rotating speed is increased or the transverse speed is decreased.