Extraordinary strength and ductility obtained in transformation-induced plasticity steel by slightly modifying its chemical composition

Extraordinary mechanical properties were obtained in a low-carbon transformation-induced plasticity (TRIP) steel by modifying its chemical composition and employing thermo-mechanical processing. It was found that Cu addition to the conventional CMnSiAl TRIP steel could improve the thermal stability of high temperature austenite by decreasing the Ac3 temperature and retarding the bainitic transformation, which led to the formation of retained austenite with higher volume fraction but lower carbon content. The combined effects of high strain hardening due to the TRIP effect, uniform strain distribution, higher volume fraction of thermal martensite, and nano-scale precipitation of ε-Cu particles in the Cu-TRIP steel led to a high strength of 1 GPa and total elongation of approximately 50%. Moreover, a detailed scanning electron microscopy analysis showed that the copper had a noticeable effect on the morphology of the martensite phase created within the microstructure.