Toughening of a 1500 MPa class steel through formation of an ultrafine fibrous grain structure

A deformation of tempered martensite, namely tempforming at an elevated temperature, was applied to a medium-carbon low-alloy steel. This thermomechanical treatment led to an evolution of an ultrafine fibrous grain structure with a strong 〈1 1 0〉∥RD fiber deformation texture and to a remarkable improvement in Charpy impact strength (uE = 165 J) at a tensile strength of 1.5 GPa.