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

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, beta-Mg(17)Al(12)particles and texture on the mechanical properties was systematically investigated. It is found that the grain size was significantly refined, and the reticular beta-Mg(17)Al(12)phase was broken into dispersed particles after multi-pass ECAP. A large amount of nanoscale Mg(17)Al(12)particles also precipitate from alpha-Mg matrix. After 4-pass ECAP, the texture features a favorable alignment of the basal planes along 45 degrees 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 beta-Mg(17)Al(12)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 degrees 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.