Microstructural Evolution and Strengthening Mechanisms of 1100 Aluminum Foil under High Strain

This study systematically investigated the grain structure evolution of 1100 aluminum alloy during rolling processes and the strengthening mechanisms of 13 μm ultra-thin aluminum foil. Metallographic observations revealed that the as-cast rolled sheet exhibited fibrous grain structures, with refined edge grains and coarser central layer grains determined by temperature gradients induced by roller cooling. During cold rolling and foil rolling (6.8 mm → 13 μm), grains experienced severe elongation along the rolling direction, with thickness compressed from millimeter-scale to nano-scale (20-50 nm). This process formed lamellar nanocrystalline bands and periodic shear bands (200 nm spacing), accompanied by significantly increased dislocation density, ultimately creating fiber bundle structures with aspect ratios exceeding 40:1. Annealing experiments demonstrated that 460°C/3h treatment rapidly recrystallized fibrous grains into equiaxed grains. Transmission electron microscopy (TEM) analysis revealed high-density dislocation tangles, dislocation walls, and subgrains within 13 μm foil. Severe dislocation pile-ups at grain boundaries substantially impeded dislocation motion, elevating tensile strength to 250 MPa. Mechanical property analysis identified three synergistic strengthening mechanisms: 1) Dominant grain refinement strengthening; 2) Significant dislocation strengthening; 3) Second-phase strengthening. Their combined effects enabled the foil to achieve both high strength (250 MPa) and moderate ductility (3.5%), surpassing the theoretical strength limit of pure aluminum. This research provides theoretical guidance for process optimization of high-performance battery aluminum foils, demonstrating the critical role of multi-scale microstructure control in balancing material strength and toughness.