Evaluating thixoformability of Mg-Zn-Nd alloys in the Mg-rich region by assessing thixoformability criteria using solidification curves

The present study investigates the thixoformability of Mg-Zn-Nd alloys in the Mg-rich region. The solidification curves of selected alloys were thermodynamically calculated using the CALPHAD approach and compared with thermal analysis experiments. The experimentally calculated curves were found to be more reliable than the Scheil-Gulliver model. Thixoforming criteria, including the highest knee point, fraction of liquid sensitivity, solidification range, and hot tearing susceptibility, were calculated based on the experimental solidification curves. Based on this analysis, alloys with compositions of Mg-3Zn-5Nd, Mg-3Zn-6Nd, Mg-4Zn-6Nd, and Mg-5Zn-6Nd have been identified as suitable for thixoforming, as they meet all four thixoforming criteria. It was observed that the alloys that met all four thixoforming criteria had a minimum of 5 wt% Nd and the presence of either Mg3Zn3Nd2 or the D-phase. Previous studies have assessed the thixoformability of alloys based on the high solidification range as an identifying characteristic for hot tearing prone alloys. However, this study has demonstrated that not all alloys with high solidification ranges are necessarily prone to hot tearing, and many alloys with relatively short freezing ranges are susceptible to hot tearing. Therefore, it is crucial to evaluate both the hot tearing susceptibility and solidification limit criteria separately when examining the thixoformability of an alloy.