Effect of asymmetry on microstructure and mechanical behavior of as-rolled AZ31 magnesium alloy medium plates during coiling at warm temperatures

Abstract

This study investigates the mechanical behavior, microstructural characteristics, and neutral layer shift of as-rolled AZ31 Mg alloys during coiling deformation at various warm temperatures. The medium plates were subjected to V-bending tests and numerical simulations. The results indicated that as the temperature increases, the non-basal slip systems are heavily activated, resulting in a decrease in fracture stress and an increase in flexural deflection. The analysis of geometrically necessary dislocations (GND) and Schmid factor (SF) indicates that tension-compression asymmetry results in higher stress concentration and a greater likelihood of cracking in the tensile zone (TZ) compared to the compressive zone (CZ). This condition is not conducive to coiling. Moreover, as the temperature increases, the density of high-angle grain boundaries (HAGBs) in the TZ gradually increases. This leads to an enhanced activation of non-basal slip systems, improving the deformability of the medium plate during coiling. The stress triaxiality fluctuated the most when the temperature reached 200 °C. This can be attributed to the involvement of non-basal slip systems in the deformation of the plate. With the increase in coiling temperature and coiling rate, the neutral layer shifts towards the TZ and subsequently transitions to the CZ, leading to a reduction in the coiling inner diameter. Moreover, the shift of the neutral layer is significantly influenced by the radius of the indenter.