Microstructure evolution, texture and mechanical properties of a Mg–Gd–Y–Zn–Zr alloy fabricated by cyclic expansion extrusion with an asymmetrical extrusion cavity: The influence of passes and processing route

Abstract

In the present work, two processing routes (A and B) with 3 CEE-AEC passes are performed on Mg–13Gd–4Y–2Zn–0.4Zr alloys, and the resultant microstructure evolution, texture analysis and mechanical properties are investigated systematically. The core difference between the two processing routes is the orientation between the expansion and extrusion steps, i.e., they are parallel to each other for on route A and perpendicular to each other for route B. The results show that a remarkable grain refinement is achieved via both processing routes due to dynamic recrystallization (DRX). Fine equiaxed grains are observed in the samples processed with route B with a final size of 3.6 ± 0.4 µm compared to the grain size of 4.5 ± 0.5 µm with route A. With an increasing number of CEE-AEC passes, the overall texture intensity decreases, and the basal texture gradually changes to the mixed texture components. The shear deformation introduced by the asymmetrical extrusion cavity promotes a broad angular distribution of the basal planes on routes A and B, leading to an obvious increase in the Schmid factor for the activation of the basal 〈a〉 slip system. The tensile test at ambient temperature reveals that the comprehensive mechanical properties are improved, and the conventional mechanical anisotropy of as-received alloys is alleviated by successive CEE-AEC processing, which is mainly derived from the competitive balance relation between the grain refinement and texture modification.