In-situ thermal analysis and macroscopical characterization of Mg–xCa and Mg–0.5Ca–xZn alloy systems

This research described the identification phases by thermal analysis and microscopy inspection of Mg–xCa and Mg–0.5%Ca–xZn alloys that were solidified at slow cooling rate. Analysis of cooling curve after Ca addition shows the evolution of the Mg2Ca intermetallic phase at around 520 °C in addition to α-Mg phase. First derivative curves of alloys after the addition of Zn to Mg–0.5Ca alloy reveals three peaks related to α-Mg, Mg2Ca and Ca2Mg6Zn3 for alloys that have Zn/Ca atomic ratio less than 1.23. The peak of Mg2Ca reaction on the first derivative curves disappeared for alloys containing Zn/Ca ratio more than 1.23. A new peak was also observed at 330 °C for Mg–0.5Ca–9Zn which was identified as Mg51Zn20. Solid fraction at coherency point decreased with increasing Ca and Zn elements. However, coherency time and difference between the nucleation and coherency temperatures (TN–TDCP) increased by adding Ca and Zn in Mg–Ca and Mg–Ca–Zn systems.

► The effect of Ca and Zn addition on Mg–Ca and Mg–Ca–Zn were investigated.
► Ca and Zn addition decreased solid fraction at coherency point.
► TN–TDCP increased by adding Ca and Zn in Mg–Ca and Mg–Ca–Zn, respectively.
► Three reactions were detected when Zn/Ca atomic ratio less than 1.25 in Mg–Ca–Zn.
► A new peak Mg51Zn20 was identified in Mg–0.5Ca–9Zn in addition of other peaks.