Analysis on the Mechanism of Strength-Ductility Enhancement by the Addition of 5% Mn in 0.1%C-2%Si-Mn Fresh Martensitic Steel with Synchrotron Radiation

Abstract

To clarify the mechanism in which a 0.1C-2Si-5wt%Mn fresh martensitic steel shows high strength and high ductility, the relationship between work hardening behavior and dislocation density change during tensile test using high intensity X-ray diffraction in synchrotron radiation in SPring-8. The increase in Mn content from 1.5 to 5% enables martensitic structure to increase dislocation density from 2.5x10¹⁵ to 4.4x10¹⁵mm/mm³, resulting in higher work hardening rate. The dislocation arrangement parameter obtained by the XRD result and TEM observation revealed that the addition of 5% Mn brought about retarding the formation of dislocation cell structure enable to increase dislocation density.