Abstract:Thermal analysis was used to investigate the microstructural evolution of Mg-7Zn-xCu-0.6Zr alloys during solidification. The effect of Cu content (0, 1, 2 and 3, mass fraction, %) on the hot tearing behavior of the Mg-7Zn-xCu-0.6Zr alloys was investigated with a constrained rod casting (CRC) apparatus, equipped with a load sensor and a data acquisition system. The thermal analysis results of Mg-7Zn-xCu-0.6Zr alloy revealed that the alloy consisted of two distinct phases: α-Mg and MgZn₂. Three distinct peaks were observed in the alloys with Cu addition, which were identified as α-Mg, MgZnCu and MgZn₂. In addition, the reaction temperature of α-Mg decreased and the reaction temperatures of MgZn₂ and MgZnCu increased as the Cu content increased. The experimental results of hot tearing demonstrated that the addition of Cu significantly reduced the hot tearing susceptibility (HTS) of Mg-7Zn-xCu-0.6Zr alloys due to the higher eutectic temperature and the shorter solidification temperature region.

Key words: Mg-7Zn-xCu-0.6Zr alloy; microstructure; solidification path; hot tearing susceptibility