Microstructure and texture characterization of Mg–Al and Mg–Gd binary alloys processed by simple shear extrusion

Abstract

Microstructural and textural evolutions of pure Mg, Mg–2 wt% Al, and Mg–2 wt% Gd were investigated after extrusion and simple shear extrusion (SSE). Microstructural studies revealed that the grain size of all extruded samples decreased after 4 passes of SSE at 553 K (280 °C). In the fine-grained Mg–2Gd alloy, however, a duplex structure consisting of fine recrystallized grains and coarse unrecrystallized patches was formed. Although the 2.5 μm size of the recrystallized grains did not experience a significant change, the volume fraction of the coarse 15 μm-wide unrecrystallized patches decreased, and the overall microstructural homogeneity was improved after 4 passes of SSE. In Mg–2Gd, fragmentation of large grains and unrecrystallized patches encouraged the formation of HAGBs, while Mg–2Al did not experience significant changes in the fraction of HAGBs. Contrary to pure Mg and Mg–2Al alloy, Mg–2Gd alloy developed a new “rare earth texture component” with the 〈112¯1〉 direction parallel to the extrusion direction in the extruded condition. However, all three materials developed the conventional “extrusion texture” after SSE.