Texture effect on the neutral layer shift and twinning behavior in bending of Mg alloys: Crystal plasticity modeling and experiment

Bending is a crucial operation in the sheet forming of Mg alloys for automotive and aerospace applications. In this work, three kinds of sheets from an AZ31 rolled plate, sheared at 0° (S0), 45° (S45), and 90° (S90) to the rolling direction, were subjected to three-point bending tests. In-situ digital image correlation (DIC) system was employed to capture the strain fields. Electron backscatter diffraction (EBSD) was used to examine the through-thickness microstructures. A crystal plasticity finite element method (CPFEM) incorporating twinning and slip mechanisms was developed to simulate the bending deformation. The texture effect on the neutral layer shift and twinning behaviors was systematically investigated in terms of both experiments and simulations. The results show that CPFEM effectively simulated the texture-dependent shifting behaviors of neutral layer and the associated twinning behaviors. Particularly, the spatial distributions of neutral layer across the entire bent plates were captured by both DIC and CPFEM. Additionally, some unusual twinning behaviors were analyzed in depth, such as the {10-12}-{10-12} secondary twins in S90, localized twin bands in S0, and the twin traces difference in S45. These findings reveal a close relationship between the neutral layer shift and twinning activity induced by the initial texture and strain levels. This work provides valuable insights into the bending deformation mechanisms of Mg alloys and has important implications for improving their formability and controlling springback.