Designing a multi-phase metastable steel with exceptional mechanical properties across a wide temperature range from 77 to 873 K

The design of alloys with exceptional mechanical properties across various temperature regimes has garnered significant attention due to their immense potential for applications in harsh environments. However, conventional alloys typically function effectively only within specific temperature ranges. In this study, we present a strategy to equip a multi-phase metastable steel attaining exceptional tensile strengths ranging from 2.2 GPa to 890 MPa, accompanied by tensile ductility between 13% and 26%, across the temperature range from 77 to 873 K. The superior cryogenic ductility is attributed to the synergistic incorporation of transformation-induced plasticity, twinning-induced plasticity, and interface enhancements. While the exceptional hardening effect at high temperature resulted from two distinctive nanoscale precipitations, including carbides and ω phase. The mechanisms are activated and function effectively at different temperatures, which paves the way for designing advanced multifunctional steels that outperform existing alloys across a broad temperature range.