Isothermal bainitic transformation in low alloy steels: factors limiting prediction of the resulting material's properties

Abstract The present study identifies key material phenomena that limit the predactive capabilities of current approaches employed in modelling the properties of heat treated components. Focus is on aspects related to the isothermal austenite-to-bainite transformation in low alloy steels. Specifically, experimental data are presented on (i) the stress–strain response of austenate prior to transformation, (ii) the magnitude and progress of transformation plasticity and (iii) the effect of externally applied loads on the kinetics of the bainitic phase transformation. The data obtained demonstrate a substantial stress-induced as well as a strain-induced acceleration of the bainitic transformation, which has to be accounted for in modelling. Moreover, stress–strain response of the supercooled austenite was found to be drastically different from that estimated based on the behaviour of stable austenitic steels. The results also point out that transformation plasticity can contribute significantly to distortion...