Phase-field simulation of microstructure formation in technical magnesium alloys

A phase-field model is presented which is specially tailored for engineering-oriented application. It addresses multi-phase, multicomponent alloys and considers lattice specific crystallographic anisotropy. Versatile application examples to magnesium alloys demonstrate the model's capability of handling important aspects of microstructure formation during solidification. Thermodynamic data is derived from a Calphad database for the Mg-Al-Zn-Ca-Mn system. First, orientation selection and texture evolution is studied under directional growth conditions. A new approach is proposed to model the anisotropy of the hexagonal close-packed magnesium phase. Subsequently, grain structure formation is simulated for technical Mg Al-based alloys under equiaxed growth conditions. It is shown how the cooling rate and the addition of specific alloy elements affect the grain size. Finally, the solidification path and its effect on the precipitation of the secondary phase Mg17Al12 has been investigated.