New insights on nucleation and transformation process in temperature-induced martensitic transformation

Abstract Understanding mechanisms of the nucleation and transformation sequence is of critical importance to control temperature-induced martensitic transformations and hence retained austenite. In the present work, quasi-in-situ Electron Backscattering Diffraction and Transmission Electron Microscopy were employed to investigate the nucleation and transition in a prototype austenitic stainless steel. Detailed evidence was provided, that nucleation could occur on new defects generated during cryogenic treatment, and not just on pre-existing defects. Moreover, transformation follows both austenite → e-martensite → α′-martensite and austenite → α′-martensite routes, their associated mechanisms, and crystallographic characteristics were analysed. These new insights could provide further guidelines for the optimization and modelling of martensitic transformation.