Abstract
In the past decades, high MnAlC lightweight steels have been extensively studied due to their excellent mechanical properties. However, the yield strength is usually less than 1.2 GPa for relative lower carbon content (≤1.2 wt %) steels after the general strengthening process. This study was intended to enhance the yield strength of the steel. For this purpose, a novel heterogenous lamellar microstructure was introduced in lightweight steel with the nominal component of Fe30Mn11Al-1.2C (wt. %), which could provide extra back stress strengthening. The microstructure consists of the lamellar fully recrystallized austenite matrix and the small volume fraction (<2%) submicron-sized ferrite which merely distributed in the fine grain layer. The formation process and the underlying strengthening mechanism of the lamellar microstructure were analyzed. Due to the synergistic strengthening of back stress, grain refinement and aging strengthening, ultrahigh yield strength (∼1.4 GPa) and greatest specific yield strength (∼220 MPa g−1 cm3) with good elongation (∼27%) were realized in the present alloy.
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