Numerical modelling and parametric study of grain morphology and resultant mechanical properties from selective laser melting process of Ti6Al4V

In this paper, a transient 3-dimensional thermal model for the selective laser melting process, based on the finite volume method, has been developed, which takes into account the phase change and powder to bulk material transition. A parametric study has been performed for the temperature field as well as the melt pool dimensions, and the results show the impact on melt pool size. Also, in this paper, a straightforward metallurgical model has been coupled to a thermal model, which uses the temperature gradient and the cooling rate on the melt pool borders at the onset of solidification to determine whether the grains have columnar or equiaxed morphology. Furthermore, the effect of process parameters on the size of grains and subsequently the yield stress has been studiedvia empirical equations. The results show that low speed along with high laser power (higher laser energy density) will cause low cooling rates and prompt the formation of large grain. This would consequently give rise to lower tensile strength, as compared tolower laser energy density where smaller grains are formed due to higher cooling rates.