Microstructure evolution and mechanical properties of the Mg-Al-Ca-Zn-Mn alloy fabricated by hot extrusion

Abstract

In this work, high-Ca Mg-Al-Ca-Zn-Mn alloys were prepared at different extrusion temperatures (290 °C and 320 °C). At low-temperature extrusion, the yield strength was elevated to 345 MPa, corresponding to an increase of about 100 MPa. In contrast, its elongation value dropped slightly to 6.7 %. The overall performance is comparable to some high-Ca AXM alloys produced through ECAP. An analysis was conducted on the DRX mechanisms and texture evolution. At the early stage, the primary deformation mechanism is ($\bar{1}012$) extrusion twinning. At the late stage, PSN mechanism dominates the DRX process. The texture intensity increases initially and then decreases, and the texture gradually concentrates towards the < $10\bar{1}0$ > component as hot extrusion progresses. This phenomenon mainly depends on the unDRXed grains containing a substantial amount of basal <a> dislocations. The analysis results regarding the strength and plasticity mechanisms indicate that the presence of fine grains and a high density of dislocations are the reasons for high strength, while the low volume fraction of the second phases and the deformable Al₂Ca phases ensure good plasticity.