Austenite reversion and nano-precipitation during a compact two-step heat treatment of medium-Mn steel containing Cu and Ni

• DOI: 10.1016/j.jmrt.2022.02.008
• Publication Date: 2022-02-10T02:52:33Z
• Authors: Zigan Xu; Xiao Shen; Tarek Allam; Wenwen Song; Wolfgang Bleck
• Keywords: Composite material; Medium-Mn steel (MMnS); Three-dimensional atom probe tomography; Ferrite (magnet); 670; Hydrogen Embrittlement in Metals and Alloys; Austenite reversion; Materials Science; FOS: Mechanical engineering; Martensite Transformation; Precipitation; 02 engineering and technology; Austenite; Tempering; Engineering; Meteorology; Synchrotron X-ray diffraction; Annealing (glass); Microstructure; Austenite Stability; info:eu-repo/classification/ddc/670; Mining engineering. Metallurgy; Volume fraction; Mechanical Engineering; Physics; TN1-997; Metals and Alloys; Strain Hardening; Materials science; Electronic, Optical and Magnetic Materials; 0205 materials engineering; Ultimate tensile strength; Physical Sciences; Metallurgy; High-Strength Steel Materials; Magnetostriction in Magnetic Materials; Nano-precipitation; Nanoprecipitation; 0210 nano-technology

Published by Elsevier, Rio de Janeiro<br/>Journal of materials research and technology 17, 2601 - 2613 (2022). doi:10.1016/j.jmrt.2022.02.008<br/>Breaking the strength-ductility paradox of very-low (0.05 wt.%)-C medium (3e12 wt.%)- Mn steels (MMnS) has been a hard-wired topic, since in these steels multi-step heattreatments are usually required to obtain austenite for improved ductility and precipitates for higher strength. In this study, a compact two-step heat treatment comprising short(2 min) annealing and tempering was developed to investigate the synergetic effect of austenite reversion and nano-precipitation on the tensile behavior of a very-low-C MMnScontaining 1.5 wt.% Cu and 1.5 wt.% Ni. The annealing step promoted considerable amount of reverted austenite (33 vol.%), and the annealing was short to prevent Cu and Ni from partitioning into austenite, since they were supposed to maintain in the ferrite phase and then promote the nano-precipitation in the subsequent tempering stage. During the subsequent tempering step, the nano-precipitates with Cu concentration of 20e50 at.% in the precipitation core and enriched with Cu, Ni, Al and Mn were observed in the ferrite phase. The volume fraction of reverted austenite reached 38.5 vol.% after tempering, which led to the ultimate tensile strength of 1222 MPa and total elongation of 29% by the transformation induced plasticity during plastic deformation. The current study demonstrates the beneficial influence of the compact two-step heat treatment on the austenite reversion and nano-precipitation behavior of very-low-C MMnS with the addition of Cu and Ni, which subsequently enables an enhanced strain hardening behavior, thereby improving the mechanical property profile of the MMnS.<br/>