A multi-component phase field model has been implemented to investigate columnar to equiaxed transition during in-situ alloying of a Ti-1Al-8V-5Fe alloy via Laser Powder Bed Fusion (LPBF). The process of in-situ alloying, where elemental powder is used instead of pre-alloyed powder, was studied by performing two simulations having (1) a uniform initial composition, and (2) spatially varying initial composition to represent different powder particles. The columnar to equiaxed transition under the two different scenarios was simulated and compared. Further, a macro-scale finite element model was developed to simulate the heat transfer during LPBF process. Specifically, the temperature gradient and solidification rate calculated by the finite element model is fed to the phase field model to simulate the dendritic growth behaviour. The results show the differing effects of elemental powder and pre-alloyed powder on columnar to equiaxed transition. The work provides fundamental knowledge about solidification in inhomogeneous concentration fields and aims to support in-situ alloying process development.

Moderated by: Andreas Ludwig / Alain Jacot