Effect of microalloyed Zr on the extruded microstructure of Mg–6.2Zn-based alloys

The addition of a small amount of Zr to a Mg–6.2Zn (Z6) binary alloy causes a substantial increase in the tensile yield strength of the extruded form of this alloy. This is attributed to the formation of thermally stable fine Mg(Zn,Zr) precipitates, which refine the extruded microstructure. A fine dispersion of β′1 and β′2 precipitates within the refined grains after T6 aging at 160 °C results in a high tensile yield strength of 275 MPa, and an ultimate tensile strength of 318 MPa with an elongation to failure of 17.1%.