Tuning mechanical behavior and deformation mechanisms in high-manganese steels via carbon content modification

In this paper, two high-manganese steels with comparable grain sizes and manganese contents, namely 34Mn0.1C and 32Mn0.6C, were investigated to explore the effect of carbon content on the mechanical behavior and deformation mechanisms at both room temperature (RT) and liquid nitrogen temperature (LNT). The results indicate that increasing the carbon content promotes the transition of deformation mechanism from dislocation slip to deformation twinning, which is similar to the effect of reducing the deformation temperature. At RT, the strength and elongation are effectively improved by increasing the carbon content, which is attributed to the transformation of deformation mode. Specifically, the yield strength, the ultimate tensile strength and the total elongation increase from 262 MPa, 595 MPa and 50.4% for the 34Mn0.1C steel to 360 MPa, 846 MPa and 87.4% for the 32Mn0.6C steel, respectively. However, at LNT, the 32Mn0.6C steel exhibites higher strength but lower elongation than the 34Mn0.1C steel. The total elongation decreases from 70.6% to 52.3%, which is because the high carbon content and cryogenic temperature induce the rapid activation of deformation twins, leading to premature fracture.