Enhanced strength and plasticity of Mg-6Zn-0.5Zr alloy by low-temperature indirect extrusion

The microstructure and tensile properties of Mg-6Zn-0.5Zr alloy processed by low-temperature indirect extrusion utilizing artificial cooling were investigated. Remarkable grain refinement was obtained by the application of artificial cooling, resulting in an increase in the yield strength of as much as 53 MPa at room temperature, as compared to the case (245 MPa) of indirect extrusion without artificial cooling. Besides this, the fine-grained alloy was found to have superplastic properties at elevated temperature, revealing tensile elongations of 720-810% at 200 °C at strain rates of 2 × 10−4-1 × 10−3 s−1. Mechanisms responsible for the high strength and superplastic properties are discussed.