Enhanced mechanical properties of a Fe-Mn-Al-C austenitic low-density steel by increasing hot-rolling reduction

The microstructure evolution and mechanical properties of a Fe-Mn-Al-C austenitic low-density steel at different hot-rolling reductions have been investigated. It was found that with the increase in hot-rolling reduction from 45% to 82%, the grain size was uniformly refined and the dislocation density was continuously increased. As a result, both yield strength and ultimate tensile strength were effectively enhanced while the ductility and toughness only slightly decreased. An excellent combination of yield strength, ultimate tensile strength, total elongation, and toughness of 648 MPa, 976 MPa, 50%, and 105 J/m2, respectively, was obtained. The yield strength increment was interpreted by the stronger grain boundary strengthening and dislocation strengthening, and the minor loss of ductility and toughness was arising from the faster saturation of the slip band refinement (slip band spacing reached ∼50 nm) and an earlier occurrence of microbands due to the finer grain size. Based on this research, it is proposed that increasing the hot-rolling reduction was an effective approach to enhance the overall mechanical properties of the low-density steel with a fully austenitic microstructure.