Effect of Al content on hot tearing susceptibility of Mg-5Zn-0.6Mn-xAl-0.6Zr alloys

Mg-Zn-Mn alloys constitute a novel class of magnesium alloys that exhibit medium strength and high plasticity, thus offering a promising application prospect. However, development and application of these alloys are limited due to their high hot tearing tendency. In this study, the effect of Al content on the hot tearing susceptibility (HTS) of Mg-5Zn-0.6Mn-xAl-0.6Zr alloys (x = 0.5, 1, 2, 4 wt%) was investigated via numerical simulation, hot tearing experiments, and differential thermal experiments. X-ray diffraction, optical microscopy, and scanning electron microscopy were used to observe the phase composition, microstructures, and fracture appearance of the alloys, and the hot tearing mechanism of the investigated alloys was comprehensively analyzed. Numerical simulation results show that the HTS of the alloys tends to decrease gradually with the increase in added content of Al. Experimental results show that with the increase in Al content, the solidification temperature range is shortened, the grain size is reduced, and the number of low-melting point phase Mg-32(Al, Zn)(49) at the grain boundaries is increased, which reduces the HTS of the alloys. The alloy with the best mechanical properties is Mg-5Zn-0.6Mn-4Al-0.6Zr, which has a tensile strength of 198 MPa and an elongation of 16%.