Nanoprecipitate-Hardened 2.8 GPa Medium-Carbon Low-Alloy Martensitic Steel with Exceptional Ductility Produced via Rapid Heavy Warm Rolling.

A rapid heavy warm rolling (HWR) process was adopted to fabricate medium-carbon low-alloy (<2.0 wt.%) martensitic steels with ultra-fine lamellar structure (ULS) suitable for industrial applications. The microstructure of the ULS martensite was mainly characterized by ultra-fine lamellae comprised of only aligned laths with reduced martensitic variants. Numerous nanoprecipitates were introduced and dispersed uniformly within the matrix after the HWR process without any tempering treatment. The density of dislocations increased dramatically to 6.694 × 10¹⁵ m⁻² in ULS martensite due to the HWR process and martensitic phase transformation. Moreover, dispersed ultra-fine retained austenitic phases were embedded within the ultra-fine martensitic matrix and along martensitic boundaries, which led to an excellent combination of ultra-high ultimate yield strength of ~ 1.9 GPa, tensile strength of ~ 2.8 GPa and great elongation of ~ 6.4%. The present rapid HWR process provides a feasible method for improving the ultra-high strength and excellent ductility of martensitic steels. [ABSTRACT FROM AUTHOR]