An investigation on the microstructure and mechanical properties in an ultrafine lamellar martensitic steel processed by heavy warm rolling and tempering

An ultrafine lamellar martensitic steel was fabricated by heavy warm rolling of undercooled austenite and subsequent quenching. The martensite transformed from warm rolled austenite was composed of ultrafine heterogeneous lamellar plates, which were further subdivided into laths and twins. The warm rolled steel after low temperature tempering exhibited excellent mechanical properties with a yield strength of 2343 MPa, ultimate tensile strength of 2586 MPa and total elongation of 9.4%. The combination of ultrahigh strength and high ductility was primarily attributed to the united effect of ultrafine lamellar plates, high density dislocations, twins and retained austenite. After high temperature tempering, the strength of warm rolled steel decreased dramatically, which was attributed to the severe recovery of martensite.