Simulation-assisted analysis of microstructural evolution of Ti-6Al-4V during laser powder bed fusion

A combination of a Multi-Phase Field model and an Orientation Field is proposed to describe the microstructure evolution induced by laser-material interaction in Laser Powder Bed Fusion (LPBF). The relevant phase transformations are covered by nucleation and growth processes driven by free enthalpy. An empiric correction is applied to the phase-field approach to reduce the grid resolution required for the numerical simulation. This contribution focuses on the LPBF processing of the titanium alloy Ti-6Al-4V. Particularly, the transition between beta-titanium and melt is emphasized. The results are discussed and compared to measurements. A numerical correction can be applied to the MPF model to avoid a mesh introduct anisotopy in the crystal growth. The simulation shows the beta-phase crystal growth with the (1 0 0) direction into the melt. The model for the phase transformation from beta-phase to alpha-phase agrees with the XRD measurements.