Effect of extrusion ratio on microstructure and mechanical properties of Mg-6Sn-3Al-1Zn alloy

Abstract

The Mg–6Sn–3Al–1Zn (wt%) alloy was prepared by casting and then deformed by hot extrusion at 350 °C with different extrusion ratios (9:1, 13:1, 20:1), extrusion rate was 20 mm min−1. The microstructure of as-extruded alloy was analyzed by XRD and EBSD, the tensile properties were tested by a universal testing machine. The results showed that there underwent processing hardening and recrystallization softening simultaneously during the process thermal deformation. Dynamic recrystallization (DRX) mainly occurred at the grain boundary of the deformed grain, with the extrusion ratio increased, the volume fraction of the dynamic recrystallization grain of alloy increased. When the extrusion ratio was less than or equal to 13:1, the average grain size decreased with the extrusion ratio increased. When the extrusion ratio reached up to 20:1, the average grain size increased. {0001} basal plane texture formed after the alloy extruded, and it paralleled to the extrusion direction, the texture intensity decreased first and then increased as the extrusion ratio increased. With the extrusion ratio increased from 9:1 to 20:1, the tensile properties increased first and then declined. Among all the tested alloys, the alloy with the extrusion ratio of 13:1 exhibited the optimum mechanical properties, the yield strength, tensile strength and elongation of alloy was 320 MPa, 371 MPa and 13.5%, the texture strength of the alloy was 8.26, the average grain size was 1.5 μm.