Modeling of Carbon Redistribution and Tetragonality Evolution in Supersaturated Ferrite

Martensite and bainite are formed from austenite through the rapid application of Bain’s strain. In several studies, martensite is considered as a body-centered tetragonal phase, but it can also be viewed as bcc ferrite supersaturated with carbon, subject to internal residual stresses from incomplet...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-12, Vol.55 (12), p.4940-4953
Main Authors: Svoboda, J., Ressel, G., Brandl, D.
Format: Article
Language:English
Subjects:
Bainite
Carbon
Characterization and Evaluation of Materials
Chemistry and Materials Science
Electron back scatter
Ferrite
Lattice sites
Martensite
Materials Science
Metallic Materials
Nanotechnology
Original Research Article
Residual stress
Room temperature
Strain
Stress relaxation
Structural Materials
Surfaces and Interfaces
Tetragonal lattice
Thin Films
Unit cell
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Summary:Martensite and bainite are formed from austenite through the rapid application of Bain’s strain. In several studies, martensite is considered as a body-centered tetragonal phase, but it can also be viewed as bcc ferrite supersaturated with carbon, subject to internal residual stresses from incomplete relaxation of Bain’s strain. Recent electron backscatter diffraction measurements have revealed a broad spectrum of tetragonality in quenched martensite, which can be attributed to the diversity of internal stress rather than variations in carbon distribution. Therefore, a thermodynamic unit cell model is developed to calculate the kinetics of carbon atom occupancy in particular kinds of octahedral interstitial lattice sites, contributing to tetragonality in loaded ferrite. The model includes a Zener-ordering term that influences carbon atom distribution and consequently affects tetragonality. Simulations suggest that carbon redistribution among octahedral interstitial lattice sites reaches equilibrium with internal stress within an hour at room temperature. The presented model provides a framework for understanding tetragonality in martensite and bainite, incorporating the effects of internal stress and carbon atom distribution in particular kinds of octahedral interstitial lattice sites.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-024-07576-5