Effect of initial thickness on bendability and inhomogeneous deformation of Mg alloy plates

Plate thickness plays a critical role in engineering applications by directly influencing the forming behavior of materials. Magnesium (Mg) alloys undergo significant bending deformation during forming processes, making it essential to understand the thickness effect on their bending behavior. In this study, three-point bending tests were conducted on AZ31 Mg alloy plates with thicknesses ranging from 1 to 12 mm (denoted as T1–T12) at room temperature. In-situ digital image correlation (DIC) was employed to capture the heterogeneous strain fields and spatial distribution of the neutral layer, while electron backscatter diffraction (EBSD) was used to analyze the gradient microstructure along the thickness. A crystal plasticity finite element method (CPFEM) was applied to correlate bending behavior with plate thickness. Combined experimental and simulation results reveal that bendability, gradient strain, twinning behavior, neutral layer shift, and cross-sectional distortion are strongly thickness-dependent. Notably, medium-thick plates exhibit a unique wing-shaped distribution of strain and twinning at the intrados, leading to non-uniform neutral layer displacement. The CPFEM successfully captures the thickness-dependent bendability and heterogeneous deformation, and the underlying mechanisms are thoroughly discussed. This study provides valuable insights for improving the stamping performance of Mg alloy plates and the precision of straightening and forming processes.