Influence of Mn–Si elements on the kinetics of oxidative phase transformation under continuous cooling conditions and modeling study

• Published in: Journal of materials science Vol. 59; no. 21; pp. 9593 - 9609
• Main Authors: Cao, Guangming, Zhao, Wencong, Song, Wentao, Yu, Hengxiang, Li, Silin, Liu, Zhenyu
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2024; Springer Nature B.V
• Subjects: Alloys; Alpha iron; Avrami equation; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Cooling; Crystallography and Scattering Methods; Eutectoid temperature; Hot rolling; Isothermal processes; Kinetics; Manganese; Materials Science; Metals & Corrosion; Phase transitions; Polymer Sciences; Reaction kinetics; Solid Mechanics; Solid solutions; Supercooling; Supersaturation; Temperature
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-024-09746-7

In this paper, a simultaneous thermal analyzer carried out isothermal eutectoid transformation experiments of Fe–0.4Mn, Fe–1.2Mn, and Fe–1.2Mn–0.2Si alloys. The kinetic model of the isothermal phase transformation of FeO was established using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation combined with the experimental data. The kinetic model of the eutectoid transformation of FeO in a non-isothermal process was also established based on Scheil's additivity rule and the mapped-out FeO. The CCT diagram shows that increasing the Mn content and adding Si elements during the continuous cooling process cause the phase zone where the FeO layer undergoes eutectoid transformation to shift to the right. Due to the similarity of crystal structures, the (Fe, Mn)O solid solution formed by FeO and MnO improves the stability of FeO. Mn 2+ widens the spacing between oxide ions, and with the increase in Mn content, the Gibbs energy of the formation of (Fe, Mn)O becomes too small to compensate for that of the formation of α -Fe from (Fe, Mn)O. In addition, the temperature point at which the phase transformation of FeO occurs decreases with the increase in Mn content, resulting in the decrease in phase transformation supercooling, so the increase in Mn content will inhibit the eutectoid transformation. The addition of elemental Si resulted in the formation of a cation-deficient FeO with higher O content and lower Fe content, and the time for the Fe 2+ concentration to reach supersaturation was prolonged, thus further inhibiting the onset of the eutectoid transformation.