Effects of extrusion ratio and temperature on the microstructure and mechanical properties of Mg–Zn–Yb–Zr extrusion alloys

Abstract

In this work, the effects of extrusion ratios (ER) and temperatures (ET) on the microstructure and mechanical properties of Mg–6.0 Zn–2.0 Yb–0.5 Zr (wt.%) extrusion alloys are investigated. The results reveal that prismatic and basal slips dominate the deformation of the low ER and ET extruded alloy, resulting in the generation of heterogeneous microstructure with an intensified basal texture. In contrast, non-basal slips robustly activate when hot extruded at the large ER and ET, promoting the development of the homogeneous-grained extrudates with a weakened “Rare-Earth” (RE) texture. A large ER effectively refines the microstructure and induces profuse nanoscale precipitates, corresponding to increased rotation angles and a wide spread of orientations in newborn grains, whereas an elevated ET coarsens the precipitates and promotes the preferential growth of grains with a certain crystallographic orientation thus developing the RE texture component. The studied extrusion alloys exhibit tunable ultimate tensile strength (301–370 MPa) and elongation (17.1–26.7%) depending on extrusion parameters. With the optimum extrusion condition (ER: 20:1 and ET: 320 °C), the alloy exhibits the best mechanical performance, which is primarily attributed to grain boundary strengthening, multiple slip systems activations, and stress concentration alleviation.