Superior strength and ductility of 316L stainless steel with heterogeneous lamella structure

Strength and ductility are two of the most important mechanical properties for a metal, but often trade off with each other. Here, we report a 316L stainless steel with superior combinations of strength and ductility that can be controlled by fine-tuning its heterogeneous lamella structure (HLS). The HLS was produced by 85% cold rolling, which produced lamellar coarse grains sandwiched between mixtures of nano-grains and nano-twins. The HLS was fine-tuned by annealing at 750 °C for 5–25 min, which resulted in varying volume fractions of nano-grains, nano-twins, lamellar coarse grains, and recrystallized grains. During tensile testing, large amount of geometrically necessary dislocations were generated near the heterostructure interfaces to coordinate the deformation between soft domains and hard domains, which results in high back stress to achieve superior combination of strength and ductility. An optimal high yield strength of ~ 1 GPa with an elongation-to-failure of ~ 20% was obtained for an optimized HLS sample. Furthermore, the processing technique employed here is conducive to large-scale industrial production at low cost.