Biaxial experimental investigation on tensile deformation of copper-containing austenitic stainless steel under different strain conditions

To address the issues of insufficient emphasis on bidirectional loading, high experimental equipment costs, and scarce related data in traditional research, its paper proposes and adopts a sequential biaxial tensile simulation method based on stepwise loading of a uniaxial tensile machine. The mechanical behavior and microstructural evolution of 3.6% Cu-304L austenitic stainless steel under various biaxial strain paths were investigated via DIC, EBSD and TEM. Results indicate that the deformation behavior is strongly path-dependent. Y-direction pre-strain significantly affects subsequent X-direction deformation, leading to lower yield strength and higher elongation. The TRIP effect is reactivated during secondary loading, and acts with dislocation rearrangement to form LAGBs and regulate work hardening. TEM results show obvious CRP coarsening and segregation, with the average size increasing linearly from 16.11 nm to 32.8 nm with strain. The Twin-Induced Martensitic Transformation (TIMT) mechanism enhances the TRIP effect at medium strains. Texture evolution transforms from uniaxial to stable biaxial orientations. Differences between strain concentration zones and uniform deformation zones dominate the synergistic strength–ductility balance.