Microstructure evolution of medium‑manganese Al-alloyed steel manufactured by double-step intercritical annealing

Effects of heating and cooling rates

Journal article (2023)

Authors

Aleksandra Kozłowska Silesian University of Technology
Mateusz Morawiec Silesian University of Technology
R.H. Petrov Universiteit Gent, Team Maria Santofimia Navarro - Mechanical, Maritime and Materials Engineering
Adam Grajcar Silesian University of Technology
Research Group
Team Maria Santofimia Navarro (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2023 Aleksandra Kozłowska, Mateusz Morawiec, R.H. Petrov, Adam Grajcar
DOI
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https://doi.org/10.1016/j.matchar.2023.112816
TRIP-assisted steel Double-step intercritical annealing Low-C martensite Medium-Mn steel Multiphase microstructure
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Published Date

2023

Language

English

Faculty

Mechanical, Maritime and Materials Engineering

Department

Materials Science and Engineering

Research Group

Team Maria Santofimia Navarro

Abstract

A novel double-step intercritical annealing (DSIA) process was conducted on Fe-0.16C-4.7Mn-1.6Al-0.2Si transformation induced plasticity (TRIP) steel. In a present study, an effect of different heating and cooling rates applied to the second intercritical annealing (IA) step on the microstructure was studied in detail by using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) techniques. The quantitative analysis of the retained austenite fractions for particular heat treatment variants was carried out via X-ray diffraction (XRD). The formation of complex microstructures containing a small fraction of ferrite, retained austenite and two types of martensite was observed regardless on the applied heating and cooling rates. It was found that the soft ferrite can be replaced by martensite through the incomplete stabilization of austenite with C and Mn during short second intercritical annealing step. The heating rate influences significantly the kinetics of austenite formation during the second heat treatment step. Low heating rates ensure more time for formation and homogenization of austenite during heating improving its thermal stability. Thus, the best balance of martensite and austenite fractions in combination with homogenous morphology of the microstructure was noted for the specimen heated at a rate of 3 °C/s, which was the lowest one in the reported experiment.