Microstructure,crystallographic texture,and plastic anisotropy evolution in an Mg alloy during equal channel angular extrusion processing

摘要

In this article, we report on the relationship between the active deformation mechanisms and the development of texture, grain size and morphology, and dynamic recrystallization (DRX) during large plastic strain deformation of an AZ31B magnesium alloy. Equal channel angular extrusion (ECAE) is used to apply a variable amount and sequence of simple shearing at 200 °C. Two different starting textures were used: basal poles either aligned with or perpendicular to the extrusion direction. A multi-scale ECAE simulation model based on crystal plasticity was employed to determine the relative contributions of different slip systems during ECAE at 200 °C. These simulations clarified how different active deformation modes were responsible for specific grain size and distribution, and grain morphology as a function of the starting textures and ECAE route. For instance, we found that relatively intense prismatic slip activity suppresses DRX, which, in turn, leads to an elongated grain structure. Room temperature mechanical testing was carried out on the processed samples along three orthogonal directions to characterize flow stress anisotropy and tension-compression asymmetry. It is shown that with proper selection of the starting texture and ECAE route, it is possible to control the level of mechanical anisotropy in the processed samples and obtain strongly or weakly anisotropic mechanical response in Mg alloys.