Heterolamellar structure design simultaneously enhances strength and plasticity in ultrahigh strength steel

A dual phase lamellar heterostructured steel was designed and prepared by introducing soft phase lamellar δ-ferrite within hard phase lath martensite matrix. Comparing to the steel with fully martensitic, the dual phase lamellar heterostructured steel exhibits substantial enhancements in both strength and plasticity. The enhance of strength is attributed to the back stress strengthening and solid strengthening of Al. Additionally, the improvement of plasticity is largely due to the high strain hardening rate and presence of lamellar δ-ferrite which buffers microcrack propagation. This research offers a strategy to overcome the strength-plasticity trade-off in ultrahigh strength steels and shows potential for widespread industrial application.