The role of ausforming in the stability of retained austenite in a medium-C carbide-free bainitic steel

Zorgani, M., Garcia-Mateo, Carlos et Jahazi, M.. 2020. « The role of ausforming in the stability of retained austenite in a medium-C carbide-free bainitic steel ». Journal of Materials Research and Technology, vol. 9, nº 4. pp. 7762-7776.
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Résumé

In this work, the influence of thermomechanical treatments, consisting of a combination of ausforming followed by isothermal holding and cooling to room temperature, on the stability of retained austenite of a carbide-free medium carbon-high silicon steel was investigated. The amount of retained austenite and its transformation to martensite for a range of ausforming treatments was determined by means of X-ray diffraction, dilatometry signal analysis, and metallographic investigation. Different amounts of deformations were applied at 600 °C in the austenite region prior to fast cooling into the bainitic transformation region. Four isothermal temperatures (325, 350, 375, and 400 °C) with a holding time of 1800 s were selected to estimate the extent of the stability of the retained austenite after the completion of the bainitic transformation. The results show that the deformation-free austenite was more stable for the samples isothermally treated at temperatures between 325 and 350 °C. However, the decomposition of retained austenite to martensite during cooling to room temperature increased for isothermal holding temperatures above 350 °C. It was found that the stability of retained austenite was a function of the temperature and percent deformation, and the critical temperature and percent deformations were determined. It was also found that ausforming enhanced the formation of blocky-shaped retained austenite for isothermal holdings above 350 °C, resulting in a decrease in retained austenite stability. The results were analyzed in terms of the influence of thermomechanical conditions on bainitic transformation and its impact on the transformation of retained austenite to martensite.

Type de document:	Article publié dans une revue, révisé par les pairs
Professeur:	Professeur Jahazi, Mohammad
Affiliation:	Génie mécanique
Date de dépôt:	12 juin 2020 19:13
Dernière modification:	13 avr. 2023 16:08
URI:	https://espace2.etsmtl.ca/id/eprint/20789

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