Measuring and Modeling Microsegregation in High-Pressure Die Cast Mg–Al Alloys

This work provides a quantitative description of the microstructure and microsegregation behavior of high-pressure die-cast (HPDC) Mg–Al and Mg–Al–Mn alloys. Plate castings of these alloys were produced using Super Vacuum Die Casting. Electron probe microanalysis mapping demonstrates that the solute profiles are in good agreement with the Scheil solidification model at the plate interior but diverge from the Scheil model near the plate surface where the cooling rate is higher. A modified Scheil equation, which incorporates solidification front velocity-dependent partition coefficients ( k v ) , provides a better description of both the microsegregation behavior and of the fraction of β -Mg 17 Al 12 that forms during solidification. Agreement between the model and experimental results can be improved by considering the amount of externally solidified crystals that have been incorporated into the local microstructure. Integrated Computational Materials Engineering capabilities for HPDC Mg–Al and Mg–Al–Mn alloys will be improved by incorporating this modified Scheil relationship into solidification simulations to better predict how the Al solute is distributed throughout the casting.