The Role of Chromium Carbides Volume Fraction on Plastic Instability Under Three-Point Bending Test in Martensitic Stainless Steel

Martensitic stainless steels (MSS) are valid candidates for automotive applications as they present a good combination of mechanical and functional properties which improves the safety and efficiency of new vehicles. However, these steels show limited fracture strain under three-point bending conditions. The fracture strain is controlled by the evolution of ductile damage as the material is plastically deformed, which in turn is influenced by microstructural features such phase ratio and carbides distribution. In this work, a modified AISI 410 MSS is heat treated in order to change the carbides distribution by dissolving part of the Cr-rich carbides while keeping the same phase ratio of ferrite and martensite. Each sample is tested under three-point bending and uniaxial tensile loading. The importance of the carbides distribution parameters (volume fraction, interparticle distance and size) on the crack propagation mechanism is assessed in order to link the material ductility to the critical microstructure constituents