Transformation potential predictions for the stress-induced austenite to martensite transformation in steel

The stress-induced transformation behavior of retained austenite is considered in this work. With the development of transformation-induced plasticity (TRIP) steels this deformation mode is of growing importance. Twinned martensite structures were calculated using the crystallographic theory of martensite. An available work criterion was used to predict the transformation potentials for 16 different in-plane stress states for sheet sample geometry. By rotating the twinned martensite structures over all crystallographic orientations using Euler angles, the magnitude of the transformation potential was plotted as an orientation distribution plot for comparison with typical texture components. From these data, the Brass and Copper orientation components that are typical in retained austenite such as in TRIP steels were found to have low transformation potential values. Grains aligned with these orientations would require higher stresses to transform than other orientations, and may therefore never transform. This correlates to experimental observations that heavily deformed TRIP steel contains residual retained austenite.