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 2.0wt.%). The alloy design was demonstrated to be sensitive to the level of Cu. An addition of 0.5wt.% Cu augmented significantly the age-hardening response during isothermal ageing at 180°C and yielded the optimal mechanical properties with UTS of 266.3MPa, YS of 185.6MPa and elongation of 16.7%. However, an addition of up to 2.0wt.% 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. The microstructures and mechanical properties of the new quaternary Mg–6Zn–xCu–0.6Zr alloys (x=0, 0.5, 1.0 and 2.0wt.%) have been investigated. The results show that the Cu content has a significant effect on the age-hardening response, tensile performance and fracture behavior of the alloys. The addition of 0.5wt.% Cu resulted in a remarkable age-hardening response and a striking improvement of the room temperature tensile properties after an isothermal ageing at 180°C. However, an excessive Cu addition of 2.0wt.% caused the formation of continuous brittle 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.