CALPHAD-Based Modeling and Experimental Validation of Microstructural Evolution and Microsegregation in Magnesium Alloys During Solidification

The microstructural evolution and microsegregation of a series of magnesium alloys (Mg-Al, Mg-Al-Ca and Mg-Al-Sn) at various cooling rates were investigated using a CALPHAD-based solidification model called PanSolidification. Experimental validations were carried out in a wide range of cooling rate (0.12 similar to 55 K/s) using both directional solidification and die casting techniques. The back-diffusion effect in solidified solid was included in the solidification model. Good agreements have been achieved between the simulated and measured solidification microstructure parameters (phase fraction and secondary dendrite arm spacing) and microsegregation within the alpha(Mg) phase. This modeling approach demonstrated the reliability of the CALPHAD-based models for the prediction of solidification microstructure of magnesium alloys and their applicability for the optimization of magnesium castings.