Numerical Simulation of Solidification in Additive Manufacturing of Ti Alloy by Multi-Phase Field Method

The multi-phase field method (MPFM) coupled with the database of calculation of phase diagrams (CALPHAD) is a powerful tool for simulation of solidification microstructure evolution in engineering casting conditions. MPFM equations have been introduced assuming quasi-equilibrium at the interface. However, few attempts have been made adopting MPFM for solidification in additive manufacturing (AM) conditions because the process is considered to be in a strongly non-equilibrium condition. In other words, the classical solidification theory based on the local equilibrium assumption was not considered to be applicable to this process. However, some researchers have reported experimental observations of the columnar-to-equiaxed transition in the solidification of AM. These suggest MPFM can be adopted for solidification simulation of the AM process. We tackled the issue of applicability of MPFM for solidification simulation in AM of Ti alloys. It was confirmed that solidification simulation using MPFM can provide observation of the columnar-to-equiaxed transition and establish a solidification map for the AM process conditions. ; Mechanical Engineering