Enhancing work hardening through tuning TRIP by nano-precipitates in maraging stainless steels

Abstract

The transformation-induced plasticity (TRIP) effect is one of the most powerful approaches to improve mechanical properties and work hardening capability of maraging stainless steels (MSSs). However, controlling the TRIP effect poses a great challenge due to the difficulties in manipulating the stability of reverted austenite (RA). In this work, through introducing nano-precipitates into the RA we achieved a significant improvement in the work-hardening ability for MSSs. The role of the RA decorated and not decorated by nano-precipitates (RADP and RANDP, respectively) was carefully investigated. The precipitation of Ni₃(Ti, Mo) and Mo-rich phases within RA causes a low stacking fault energy (SFE) in the RADP compared to the RANDP. In the initial stage of deformation, the RADP is susceptible to the TRIP effect due to the low SFE, which can effectively relieve stresses. Upon further deformation, the nano-precipitates within the RA can block the movement of the 1/6<112> Shockley partial dislocations and delay the transformation, thus improving the stability of the RA. This results in a sustainable absorption of stresses and delays the initiation and propagation of cracks. Moreover, the nano-precipitates in the matrix provide a significant increase in strength. Consequently, an excellent combination of high strength, ductility, and work-hardening ability was obtained in the MSSs. The newly developed MSS demonstrates a yield strength of 1790 ± 24 MPa, a tensile strength of 2140 ±32 MPa, a uniform elongation of 9.5 ± 1.3 % and a total elongation of 16.4 ± 1.1 %. Exploiting the nano-precipitation within RA to tune the TRIP effect provides a new approach for developing high-performance MSSs.