Microstructure and mechanical properties of Mg-6Zn-xCu-0.6Zr (wt.%) alloys

In this paper, we report the microstructures and mechanical properties of a new quaternary Mg-6Zn-xCu-0.6Zr alloys (x = 0, 0.5, 1.0 and 2.0 wt.%). The alloy design was demonstrated to be sensitive to the level of Cu. An addition of 0.5 wt.% Cu augmented significantly the age-hardening response during isothermal ageing at 180 °C and yielded the optimal mechanical properties with UTS of 266.3 MPa, YS of 185.6 MPa and elongation of 16.7%. However, an addition of up to 2.0 wt.% led to the formation of continuous grain-boundary intermetallic particles, thus degrading the age-hardening response and the mechanical properties of the alloy. The microstructural factors associated with the improvements in the mechanical properties are discussed in detail.