<p>The experiment involved the preparation of an Mg-10Zn-5Al-0.4Zr (wt.%) alloy through gravity casting and heat treatment, which was conducted to investigate the effects of heat treatment on the microstructure and properties. Before heat treatment, the microstructure consisted of MgZnAl and a minor amount of Al₂Zr phases. After heat treatment, the Al₂Zr phase was eliminated, and the microstructure displayed numerous rod-shaped and particulate MgZnAl phases, fine rod-shaped MgZn phases, as well as block-shaped Mg₂ZnAl₃ phases. Both the MgZnAl and MgZn phases possess a hexagonal close-packed crystal structure and exhibit certain coherency with the α-Mg matrix. The Mg2ZnAl3 phase has a monoclinic crystal structure and displays partial coherency with the <i>α</i>-Mg matrix. After heat treatment, the tensile properties of the Mg-10Zn-5Al-0.4Zr alloy reached a maximum of 244.2&#xa0;MPa in tension, with a yield strength of 220.09&#xa0;MPa and an elongation of 1.3%. These values represent improvements of 52.48, 66.02 and 0.5%, respectively, compared to the properties before heat treatment. These enhancements can be attributed to the high density of coherently and partially coherently precipitated phases, as well as grain refinement, which induces dislocations and stacking faults that strengthen the alloy’s matrix.</p>