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

• Published in: Journal of materials science & technology 2022-03, Vol.104, p.52-58
• Main Authors: Niu, M.C., Yang, K., Luan, J.H., Wang, W., Jiao, Z.B.
• Format: Article
• Language: English
• Subjects: Austenite reversion; Cu-rich nanoprecipitate; Maraging stainless steel; TRIP effect
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2021.06.055

•Effects of Cu on austenite reversion and TRIP of maraging steels were studied.•Cu as an austenite stabilizer increases the driving force for austenite reversion.•Cu precipitates promote the austenite reversion through interfacial segregation.•Reverted austenite improves the ductility and toughness through a TRIP effect.•The work provides a new avenue to enhance the strength-ductility-toughness synergy. 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 formation, 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 addition, 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 martensite, which substantially improves the ductility and toughness through a transformation-induced plasticity (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. [Display omitted]