Simultaneous enhancement of strength-ductility via multiple precipitates and austenite in a novel precipitation-hardened martensitic stainless steel

In this study, the advantages of the novel precipitation-hardened martensitic stainless steel (abbreviated as novel steel) in terms of an excellent strength–ductility balance are fully elucidated utilizing various methods and tests. The novel steel increases the yield and ultimate tensile strength from 1480 ± 20 MPa and 1500 ± 18 MPa to 1530 ± 15 MPa and 1650 ± 20 MPa, respectively, and simultaneously improves the elongation from 9.7 ± 0.5% to 17.8 ± 1.1% over that of conventional PH13–8Mo steel. Specifically, the novel steel is mainly strengthened and toughened by three factors, including fine grain strengthening, precipitation strengthening of multiple precipitates (Cu, NiAl) and the TRIP effect. The contribution of fine grain strengthening is quantitatively evaluated through the Hall–Petch relationship. Meanwhile, the value of strengthening contributions by multiple precipitates are quantitatively evaluated through the shearing or Orowan mechanism. Significantly, compared with conventional PH13–8Mo steel, the addition of Cu leads to the formation of multitudinous metastable austenite in the novel steel. The TRIP effect can be generated by metastable austenite upon applied loading conditions. An accessible pathway is found to exploit high-performance stainless steel.