Cu-assisted austenite reversion and enhanced TRIP effect in maraging stainless steels

Control of the formation and stability of reverted austenite is critical in achieving a favorable combination of strength, ductility, and toughness in high-strength steels. In this work, the effects of Cu precipitation on the austenite reversion and mechanical properties of maraging stainless steels were investigated by atom probe tomography, transmission electron microscopy, and mechanical tests. Our results indicate that Cu accelerates the austenite reversion kinetics in two manners: first, Cu, as an austenite stabilizer, increases the equilibrium austenite fraction and hence enhances the chemical driving force for the austenite forma-tion, and second, Cu-rich nanoprecipitates promote the austenite reversion by serving as heterogeneous nucleation sites and providing Ni-enriched chemical conditions through interfacial segregation. In addi-tion, the Cu precipitation hardening compensates the strength drop induced by the formation of soft reverted austenite. During tensile deformation, the metastable reverted austenite transforms to marten-site, which substantially improves the ductility and toughness through a transformation-induced plastic-ity (TRIP) effect. The Cu-added maraging stainless steel exhibits a superior combination of a yield strength of-1.3 GPa, an elongation of-15%, and an impact toughness of-58 J. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

Control of the formation and stability of reverted austenite is critical in achieving a favorable combination of strength, ductility, and toughness in high-strength steels. The effects of Cu precipitation on the austenite reversion and mechanical properties of maraging stainless steels were investigated. Cu accelerates the austenite reversion kinetics by increasing the equilibrium austenite fraction and serving as heterogeneous nucleation sites. Cu precipitation hardening compensates the strength drop induced by the formation of soft reverted austenite.