Predicting the hot tearing susceptibility of Mg-10Gd-xZn alloys from a perspective of thermal analysis and thermodynamic modeling

In the present investigation, the hot tearing susceptibility of Mg-10Gd-xZn (x = 0,1,2,4 wt% Zn) was evaluated from the Kou model, where the Fraction of solid-Temperature curves were derived from a thermodynamic database (TCMG5) and also from the thermal analysis approach. The Kou-TCMG5 and the Kou-thermal analysis models were thoroughly compared with one another and were further validated with the experimentally calculated crack volume, obtained by performing the constrained rod casting (CRC) test. From the outcomes, it was observed that the Kou-thermal analysis results were in good agreement with the experimentally obtained crack volume, while on the other hand, the Kou-TCMG5 model deviated from the experimental observations. Using a combination of XRD and SEM, the phases evolved during thermal analysis were compared with the TCMG5 Scheil model, and it was observed that the knowledge of the actual phase equilibria is an important factor in accurately predicting the hot tearing susceptibility using the Kou model. The reasons for the discrepancy between the Kou-thermal analysis and the Kou-TCMG5 model have been addressed in detail.