Effect of TA1 thin sheet anisotropy on stamping of titanium BPPs for PEMFC

The significant anisotropy of TA1 thin sheet exerts a critical impact on the stamping forming of titanium bipolar plates (BPPs) for proton exchange membrane fuel cells (PEMFCs). This paper systematically investigates the effect of TA1 sheet anisotropy on BPP stamping via a combination of experiment and simulation. Tensile tests reveal that TA1 thin sheet exhibits obvious tensile anisotropy: yield strength is highest in the TD direction, followed by the RD direction, and lowest in the 45° direction; tensile strength peaks in the RD direction, while ductility is optimal in the 45° direction and poorest in the TD direction. EBSD analysis indicates that this anisotropy originates from the sheet's initial bimodal texture, with the [0001] axis inclined 45° between the TD and ND directions, and the texture transforms from fiber texture to sheet texture after tensile deformation. Based on tensile results and Hill’48 yield criterion, an anisotropic constitutive equation of TA1 sheet is established, and a BPP stamping model is built on the ABAQUS/Explicit platform. Simulation results show that the sheet presents the best thinning resistance and formability along the RD direction with the highest thickness anisotropy index r, superior to the TD and 45° directions. Stamping experiments confirm that the maximum thinning occurs at the outer flow channel fillet, and the RD direction achieves the minimum thinning and highest channel aspect ratio, highly consistent with simulation predictions. This study provides a clear industrial recommendation: aligning the flow channel length direction with the RD to maximize material performance and product yield.