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

Advanced Engineering Materials, vol. 25

Abstract

Herein, the effect of shortening the intercritical annealing (IA) time in a two‐step process “intercritical annealing and tempering (IAT)” on the microstructure and the mechanical properties of medium‐manganese steel (MMnS) made of Fe–0.05C–7Mn–1.5Cu–1.5Ni–1.5Al–1.5Si–0.5Mo (wt%) and containing copper‐rich (CRP) and Ni(Al/Mn) precipitates is investigated. The atom probe tomography (APT), electron backscattering diffraction (EBSD), and the synchrotron X‐ray diffraction (SYXRD) are used to study precipitation, phase microstructure evolution, the austenite stability, and deformation mechanisms. Shortening the IA step, which is carried out at 700 °C, from 2 min (IAT‐2) to 1 min (IAT‐1), results in a yield strength (YS) increment of around 218 MPa with less than 1% loss of ductility. While the enhanced yield strength in IAT‐1 is attributed to the four times higher precipitates’ number density (n), the insignificant loss of ductility is attributed to the enhanced austenite stability factor from 4.5 to 9.2 in IAT‐2 and IAT‐1, respectively. The simultaneous increase in YS without ductility loss reflects that controlling the IA time is a promising strategy to overcome the yield strength and ductility trade‐off without the need for higher additions of costly alloying elements such as Ni, Al, Mn, and Cu.

Authors 5

1. Asmaa Elbeltagy corresponding Aachen Steel Institute

   RWTH Aachen University

   Affiliation as printed

   Steel Institute (IEHK) RWTH Aachen University 52072 Aachen Germany

   Steel Institute (IEHK), RWTH Aachen University, 52072 Aachen, Germany

2. Zigan Xu Aachen Steel Institute

   RWTH Aachen University

   Affiliation as printed

   Steel Institute (IEHK) RWTH Aachen University 52072 Aachen Germany

   Steel Institute (IEHK), RWTH Aachen University, 52072 Aachen, Germany

3. Xiao Huan Shen Aachen Steel Institute

   RWTH Aachen University

   Affiliation as printed

   Steel Institute (IEHK) RWTH Aachen University 52072 Aachen Germany

   Steel Institute (IEHK), RWTH Aachen University, 52072 Aachen, Germany

4. Ulrich Krupp Aachen Steel Institute

   RWTH Aachen University

   Affiliation as printed

   Steel Institute (IEHK) RWTH Aachen University 52072 Aachen Germany

   Steel Institute (IEHK), RWTH Aachen University, 52072 Aachen, Germany

5. Wenwen Song

   University of Kassel

   Affiliation as printed

   Institute of Materials Engineering University of Kassel 34125 Kassel Germany

   Institute of Materials Engineering, University of Kassel, 34125 Kassel, Germany