Tailoring the Austenite Fraction of a Cu and Ni Containing Medium-Mn Steel via Warm Rolling

Abstract

Developing medium-Mn steels (MMnS) demands a better understanding of the microstructure evolution during thermo-mechanical treatments (TMTs). This study demonstrates the relationship among processing, microstructure, and mechanical properties of a warm-rolled medium-Mn steel (MMnS) containing 1.5 wt. % Cu and 1.5 wt. % Ni. After short-time warm rolling (WR) in an intercritical temperature range, a significant quantity (40.6 vol.%) of austenite was reverted and retained after air cooling. The microstructure and tensile properties of the WR specimens were compared with two typical process routes, namely hot rolling+ cold rolling+ annealing+ tempering (CRAT) and warm rolling+ annealing+ tempering (WRAT). The WR specimen exhibited comparable tensile properties with the CRAT specimens (967 MPa yield strength, 1155 MPa tensile strength, 23% total elongation), with a remarkably shortened process route, which was derived from the dislocation accumulation and austenite reversion during rolling. The WR route stands out among the traditional CRAT and the extended WRAT routes for its excellent tensile properties and compact processing route.

Yield Strength Enhancement Without Ductility Loss Through Controlling the Intercritical Annealing Time in Medium‐Mn Steels

“…More details on the chemical composition design using ThemoCalc 2019b software in addition to the processing route are reported in earlier work. [ 24,26 ]…”

“…In the previously published work of this study, [ 24–26 ] the processing route and heat treatment parameters in a two‐step IAT were designed and optimized to obtain the best ductility. To study the effect of IA time on the microstructure, nanoprecipitates, and mechanical properties, two categories including four processing variants were designed.…”

“…In our previous research work, [ 24–26 ] a two‐steps process of intercritical annealing (IA) for 2 min followed by a 3 h tempering step was developed. The processing route and heat treatment parameters with respect to the annealing time and tempering temperature were optimized to achieve an MMnS alloy that contains CRP and Ni(Al/Mn) precipitates with better mechanical properties, namely, ductility.…”

“…With this two‐fold strategy, a higher yield strength without loss of ductility should be achieved via a two‐steps “intercritical annealing and tempering (IAT) process”. [ 24–26 ]…”

Influence of the Inherited Structure Induced by Al and Si Alloying on Microstructure Evolution and Mechanical Properties of 100Cr6 Steels

“…[ 1 ] The volume fraction, distribution, and stability of the retained austenite determine the deformation‐induced austenite‐α’–martensite transformation as a function of the temperature and the mechanical stress. [ 11 ] These parameters must be chosen in such a way that, on the one hand, the intended increase in the damage tolerance is achieved, but on the other hand a large‐scale transformation, and thus, a volume change that exceeds the geometrical tolerance, is excluded. [ 12 ]…”