IMPROVEMENT OF STRENGTH AND DUCTILITY OF MG-ZN-CA-MN ALLOY BY EQUAL CHANNEL ANGULAR PRESSING

摘要

An ultrafine-grained (UFG) Mg-5.25 wt.% Zn-0.6 wt.% Ca-0.3 wt.% Mn alloy was produced by subjecting the as-extruded alloy to equal channel angular pressing (ECAP) for 4 passes at 250 and 300 ℃, respectively. ECAP resulted in a remarkable grain refinement. After ECAP processing at 250℃, basal planes are oriented both parallel and inclined about 45° to the extrusion direction, while most the basal planes are oriented parallel to the extrusion direction after ECAP processing at 300 ℃. Both yield strength and elongation were increased after ECAP processing. The yield strength was higher in the ECAPed alloy processed at 300 ℃ with larger grain size, indicating that the texture strengthening effect was dominant over the strengthening from grain refinement in the ECAPed alloy. The grain refinement may lead to dislocation slip on non-basal plane and grain boundary sliding, which improved the ductility of the ECAPed Mg-Zn-Ca-Mn alloy.