Direct Observations of Deformation-Induced Retained Austenite Transformation in a Vanadium-Containing Dual-Phase Steel

The mechanical stability of retained austenite was investigated in a vanadium-containing dual-phase steel by in situ deformation of thin foils in a transmission electron microscope. Essentially two types of retained austenite particles were observed, large 2–6 μm diameter particles and submicron-size particles. The former were found to be extremely unstable to deformation, readily undergoing transformation to twinned plate martensite, while the latter resisted transformation even after severe deformation. The significance of these observations to the work-hardening behavior of the dual-phase steel is discussed.