Work hardening behaviour and damage mechanisms in carbide-free bainitic steel during uni-axial tensile deformation

Abstract

The study has examined the work hardening characteristics and damage mechanisms of a newly developed carbide-free bainitic steel. These are correlated with the microstructural constituents using the established empirical equations and the experimental findings. Carbide-free bainitic steel has shown primarily three stages of deformation in modified Crussard-Jaoul analysis, which best describes the work hardening behaviour. Plastic deformation of retained austenite precedes the deformation of bainitic ferrite. The blocks of retained austenite transform to strain induced martensite at lower strain levels than the films of retained austenite. With increasing strain, cross slip assisted dynamic recovery, and sub-grain formation become predominant in bainitic ferrite. Although early void initiation occurs at the non-metallic inclusions, these do not play a significant role in the final fracture. Void initiation and splitting of phase boundaries due to strain incompatibility, decohesion of prior austenite grain boundaries and cracking of martensitic-austenitic constituents are the main damaging mechanisms.