Microstructure and mechanical properties of a continuous carbon-gradient sheet steel

Abstract

To take advantage of the high strength of high-carbon martensitic steel and simultaneously avoid insufficient plasticity, a novel continuous carbon-gradient sheet steel (CGSS) with a high-carbon surface and medium-carbon core was developed as a gradient material using surface carburizing and warm rolling. An exceptional strength–ductility combination was achieved. On the premise of carbides precipitation in high-carbon martensitic matrix, tempered CGSS at 200 °C exhibits excellent mechanical property with an ultimate tensile strength of 2440 MPa and a total elongation of 4.6%. Enlarged-strain-component in the tensile direction is the primary cause for higher plasticity in the high-carbon surface. Inhomogeneous fracture mode indicates the typical restraint of crack propagation in the core, suggesting greater toughness for the tempered CGSS.