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Influence of annealing parameters on phase evolution and recrystallization kinetics of a Mn-Al-Si alloyed duplex steel

Journal Article · · Materials Characterization
; ; ;  [1]
  1. Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India)
Highlights: • Stacking fault energy calculated for Fe-9.8Mn-7.5Al-1.22Si-0.2C steel is 48.4 mJ/m{sup 2} • Austenite stability decreases with increasing temperature due to higher free energy • Mn{sub 5}(Al,Si)C precipitates evolve with concurrent disappearance of austenite at 1273 K • Decrease in austenite fraction stimulates boundary migration for recrystallization • The maximum value of Avrami exponent ~ 1 implies sluggish recrystallization kinetics - Abstract: In this study, the phase transformation and recrystallization behavior of hot-forged Fe-Mn-Al-Si-C alloyed duplex steel has been investigated in wide ranges of annealing temperatures (973-1273 K) and durations (15–150 min). The recrystallization kinetics has been evaluated employing Johnson-Mehl-Avrami-Kolmogorov model. A limited extent of phase transformation (i.e. duplex to single phase) has been found to take place during annealing in the range of 973-1173 K. However, during annealing at 1273 K, not only the transformation from duplex to ferritic microstructure accelerates, but also recrystallization is initiated in these ferrite grains. The changes in the free energy of the austenite with the annealing temperature play a pivotal role in dictating the stabilization of the corresponding phase. Moreover, the disappearance of the austenitic phase at 1273 K owing to higher free energy is compensated by the formation of Mn-Al-Si rich carbide precipitates. The phase evolution triggered by annealing at 1273 K affects the recrystallization kinetics of each of the phase constituents. A sharp rise in the Avrami exponent (n) value is noticed following annealing at 1273 K, which clearly denotes that the disappearing austenite-ferrite interfaces facilitate the migration of the ferrite boundaries that stimulate recrystallization. In spite of the increasing values of n with the annealing temperature, its maximum value (at 1273 K) remains close to 1. This is a clear indication of the sluggish nature of the recrystallization process in the developed alloy.
OSTI ID:
22804822
Journal Information:
Materials Characterization, Journal Name: Materials Characterization Vol. 134; ISSN 1044-5803; ISSN MACHEX
Country of Publication:
United States
Language:
English

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