Simulation of recrystallization and martensite revision in 304L austenitic stainless steel after multi-pass rolling proc
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ORIGINAL PAPER
Simulation of recrystallization and martensite revision in 304L austenitic stainless steel after multi‑pass rolling processes P. Alavi1 · S. Serajzadeh1 Received: 8 February 2020 / Accepted: 2 May 2020 © Springer Nature Switzerland AG 2020
Abstract In this work, non-isothermal annealing of cold-rolled 304L austenitic stainless steel was studied at temperatures ranging between 400 and 800 °C. In the first place, a dual-phase structure containing work-hardened austenite and strain-induced martensite was produced by means of multi-pass plate rolling, and then, the deformed steel was subjected to annealing heat treatments. To determine the distribution of stored strain energy in the rolling operations, an elastic–plastic finiteelement modeling was conducted. Afterwards, an artificial neural network technique was coupled with the thermal-cellular automata model for prediction of martensite reversion, temperature history, and recrystallization progress during subsequent non-isothermal heat treatments. Experimental methods including X-ray diffraction, optical metallography, and Feritscope measurements were carried out to assess the material constants as well as to verify the predictions. Comparison between the predicted results and experimental data showed a good agreement indicating the capability of the model under practical conditions. It was found that that martensite revision started at about 550 °C, while the onset of recrystallization occurred around 670 °C. The activation energies for nucleation and growth during static recrystallization were determined as 180 kJ/ mole and 240 kJ/mole, respectively. In addition, the homogenous nucleation mechanism was found to be operative in the rolled steel subjected to total reduction of 35% or higher that resulted in a uniform fine-grained structure. Keywords Austenitic stainless steel · Martensite reversion · Cellular automata · Neural network · Cold rolling · Static recrystallization
1 Introduction Although austenitic stainless steels have shown good formability and high corrosion resistance, they are not heat treatable, while cold-working and grain refinement are considered as the main hardening mechanisms. During cold working, strain-induced martensite may be formed and it reduces corrosion resistance (Liu et al. 2019). In this regard, a combination of cold working and annealing treatment is usually employed to obtain the desired mechanical properties and corrosion resistance. It should be noted that martensite could act as preferential nucleation sites during static recrystallization, and thus, cold working and subsequent recrystallization can even produce sub-micron grain structures (Misra et al. 2018). At the initial stage of cold deformation, ε-martensite * S. Serajzadeh [email protected] 1
Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran
with HCP crystallographic structure may be formed on stacking faults; however, by further plastic straining, α′martensite is developed on shear band intersectio
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