Evolution of Microstructure and Mechanical Properties of AZ31 Sheets with Different Initial Microstructures During the Corrugated Wide Limit Alignment Process

Abstract

Presetting tensile twins (TTs) can enhance the mechanical properties of magnesium (Mg) alloys. Two as-received (AR) sheets, as-received state-A (AR-A) with fiber texture and nonuniform grains and as-received state-B with basal texture and uniform equiaxial grains are selected to induce TTs via a novel method called corrugated wide limit alignment (CWLA), and the corresponding CWLA-processed sheets are denoted as CWLA-processed state-A (C-A) and CWLA-processed state-B (C-B). The results demonstrate that a larger initial average grain size correlates with a higher fraction of TTs induced in Mg sheets, thereby refining the grains and forming a new rolling direction (RD) tilted texture during CWLA. The ultimate tensile strength increases by 32% from AR-A to C-A, primarily due to refinement strengthening and twinning-induced strain hardening. The recrystallization mechanism of C-A is dominated by twinning-induced dynamic recrystallization (DRX), where DRX grains prefer to inherit the orientation of TTs, resulting in an enhanced RD-tilted texture and the formation of multi-modal texture. The recrystallization mechanism of C-B is mainly discontinuous DRX and continuous DRX, and the DRX grains prefer to inherit the orientation of matrix grains, ultimately forming a basal texture. In summary, the tensile mechanical behavior of pre-twinned Mg sheets significantly depends on the grain size and texture of the AR sheets, so they present similar changing trends during tensile deformation.