Effect of mass ratio of Zn to Al on as-cast microstructure and solidification behaviour of Mg-Zn-Al ternary magnesium alloys

The effect of mass ratio of Zn to Al on the as-cast microstructure and solidification behaviour of Mg-Zn-Al ternary magnesium alloys was investigated. The results indicate that, when the mass ratio of Zn to Al of experimental alloys are less than 2, the alloys are composed of α-Mg and Mg32(Al, Zn)49 phases, and with increasing mass ratio of Zn to Al, the amount of the second phases in the alloys gradually decreases and the distribution of the second phases changes from continuous net to quasti-continuous net. However, when the mass ratio of Zn to Al of experimental alloys is more than 2, the alloys are composed of α-Mg, Mg32(Al, Zn)49 and MgZn phases, and with increasing mass ratio of Zn to Al, the amount of the second phases in the alloys gradually increases and the distribution of the second phases changes from quasti-continuous net to uniform particles. In addition, the onset and peak temperatures of the second phase transformation for the experimental alloys with relatively low mass ratio of Zn to Al (2), which results in different reactions during the second phase transformation and different types of the second phases.