Abstract
Hot extrusion of machined chips of Mg96Zn2Y2 (at%) alloy was carried out at 623 K, and microstructures and mechanical properties of the extruded Mg96Zn2Y2 alloy were investigated. The alloy consisted of α-Mg, Mg12ZnY, and Mg3Zn3Y2 phases, and the Mg grains had a mean grain size of 450 nm. The Mg12ZnY phase was frequently observed inside the fine Mg grains. In addition, oxidation occurred around cavities remaining after extrusion. The extruded alloy exhibited a high 0.2% proof strength of 495 MPa and elongation of 3% at room temperature. The Mg grain refinement and dispersion of Mg12ZnY and Mg3Zn3Y2 phases caused by hot extrusion led to high strength at room temperature. Further, the extruded alloy also exhibited superplasticity at temperatures of 623 and 723 K with initial strain rates from 2×10−1 S−1 to 2×10−3 S−1. The maximum elongation was 450% at 723 K with an initial strain rate of 2×10−3 S−1. Grain boundary sliding of Mg grains is the dominant deformation mechanism for the alloy at high temperature ranges.
