Influence of the Final Annealing Temperature on Al-Fe-Si Alloy Foil Microstructure and Properties

This study systematically investigates the effects of the final annealing temperature on the microstructural evolution and mechanical properties of an Al-Fe-Si alloy aluminum foil. Scanning electron microscopy (SEM) characterization and tensile tests are employed for analysis. As the annealing temperature is elevated from 240 °C to 360 °C, the average grain size increases monotonically from 5.2 μm to 9.6 μm. Continuous recrystallization is identified as the predominant grain growth mechanism. Tensile deformation exhibits the homogeneous plastic behavior without localized necking. The tensile strength decreases significantly in the range of 240–300 °C and subsequently undergoes a recovery stage at 300–360 °C. Significant elongation anisotropy is observed. The maximum elongation reaches 30–34% in the 45° direction, relative to the rolling direction (RD), which is approximately 1.5 times that along the RD (0°). Comparative analysis of the anisotropy indices demonstrates that the aluminum foil annealed at 240 °C achieves the minimal tensile strength anisotropy (13.0 MPa) and elongation anisotropy (−4.2%). This indicates an optimal comprehensive mechanical performance. These findings provide a theoretical rationale for the industrial optimization of the annealing processes for Al-Fe-Si alloy foils. They are particularly valuable for balancing microstructural regulation and mechanical property enhancement in lithium-ion battery soft-packaging applications.