Solidification Microstructure Prediction of Ti-6Al-4V Alloy Produced by Laser Melting Deposition

The ability to achieve a predictable solidification microstructure would greatly accelerate the qualification of the additive manufacturing process. Solidification microstructure control is a challenging issue for the additive manufacturing of metallic components using the laser melting deposition (LMD) method. To obtain desirable microstructure characteristics and mechanical properties, it is essential to research the solidification mechanism of microstructures initiated during the LMD process. In this study, the grain morphology and size of an LMD-fabricated Ti-6Al-4V alloy were predicted using a three-dimensional cellular automaton (CA) model coupled with a finite element (FE) model (CA–FE). First, the temperature distribution and solidification microstructure were established with the multi-scale CA–FE model, and the simulated results were shown to be in qualitative agreement with the experimental results. Moreover, the effects of the process parameters on both the thermal characteristics and the solidification microstructure were identified, and the morphologies and sizes of prior β grains under different laser power levels and scanning speeds were compared. The average grain size of the molten pool was shown to decrease with decreasing incident energy (lower laser power/higher scanning speed), and columnar-to-equiaxed transformation could be achieved under the proper processing parameters. This work will serve as a guide for the optimization and regulation of microstructures in the LMD process.