Synergistic Effect of Grain Size, β-Mg17Al12, and Texture on Mechanical Properties of Mg-15Al (wt.%) Magnesium Alloy Processed by Equal Channel Angular Pressing

Abstract

In this study, the Mg-15Al (wt.%) alloy was processed via equal channel angular pressing technology through different passes. The effect of the grain size, β-Mg17Al12 particles and texture on the mechanical properties was systematically investigated. It is found that the grain size was significantly refined, and the reticular β-Mg17Al12 phase was broken into dispersed particles after multi-pass ECAP. A large amount of nanoscale Mg17Al12 particles also precipitate from α-Mg matrix. After 4-pass ECAP, the texture features a favorable alignment of the basal planes along 45° from the extrusion direction. In addition, the tensile strength and ductility are remarkably improved with increasing the extrusion pass and the best mechanical properties are achieved for the 4-pass ECAP (UTS = 269.3 MPa, EL = 8.1%), which can be ascribed to the grain boundary strengthening, the precipitation strengthening as well as the declined fragmentation effect of the reticular β-Mg17Al12 phase. However, under the ECAP conditions with large deformation, the yield strength shows a contrarily decreasing tendency. This is because the orientations of the basal poles in the texture present a nearly 45° to the extrusion axis proven by the higher Schmid factor (SF), making it much easier to start the sliding system of the Mg-15Al alloy during ECAP.