Uncovering the effect of retained austenite stability on the dynamic mechanical properties of TRIP-aided steel

TRIP-aided steel has received significant attention because of its ability to appreciably enhance the ductility and toughness by utilizing the transformation-induced plasticity (TRIP) effect of retained austenite (RA). However, the dynamic mechanical properties, similar to the condition of crash situation, which is related to RA stability, are overlooked. In this study, three types of TRIP-aided steels with different RA stability were prepared by controlling the isothermal tempering time while maintaining a consistent matrix. Dynamic compression was conducted at different strain rates to elucidate the influence of RA stability on the dynamic mechanical properties. The results indicate that at high strain rates, adiabatic temperature increase enhances the stability of austenite. The effect of adiabatic temperature increase on RA with different stability is consistent at different strain rates, and the initial stability of RA determines the dynamic mechanical properties. Compared with the steel with initially high stable RA, the steel with unstable RA can absorb more plastic work/deformation energy through more active TRIP effect, hinders the formation of adiabatic shear bands (ASB), and significantly improves the dynamic mechanical properties. The higher strain rate induces a more significant improvement in dynamic mechanical performance brought by unstable RA. This provides a new perspective on the microstructure design of TRIP-aided steel that needs to consider deformation behavior under high strain rates, such as high velocity impact.