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Experimental Investigation of Phase Equilibria in the Fe-Cr-Si Ternary System An-dong Wen1 • Li-gang Zhang1 • Li-bin Liu1 • Patrick J. Masset2,3 Yun Zhao1 • Ling-hong Zheng1 • Fen-yan Zhao1

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Submitted: 13 January 2020 / in revised form: 31 May 2020  ASM International 2020

Abstract Isothermal sections of the Fe-Cr-Si ternary system at 1000 and 1100 C were studied using x-ray diffraction, scanning electron microscopy and electron probe micro-analysis. Isothermal sections were identified with seven and six three-phase regions at 1000 and 1100 C, respectively. The r phase contains 6.2-20.2 at.% Si at 1000 C and 8.3-21.2 at.% Si at 1100 C. Fe and Cr can be entirely substituted by each other to form the continuous solid-solution e or CrSi phases. The g phase is stable at 1100 C because of the dissolution of Cr. Additionally, large solubility was detected in some binary compounds, e.g., up to 26.6 and 19.6 at.% Fe in aCr5Si3 and Cr3Si at 1000 C, respectively. Keywords Fe-Cr-Si system
phase diagram
silicon steels

1 Introduction The Fe-Cr-Si system is one of the most important subsystems for the steel industry and manufacturers. Si-based steels are widely used for energy transmission and

& Li-gang Zhang [email protected] & Li-bin Liu [email protected] 1

School of Materials Science and Engineering, Central South University, Changsha 410083, People’s Republic of China

2

Faculty of Mechanical Engineering, Koszalin University of Technology, ul. S´niadeckich 2, 75-453 Koszalin, Poland

3

Technallium Engineering & Consulting, Fliederweg 6, 92449 Steinberg am See, Germany

electromagnetic energy conversion systems because of their low magnetostriction and high saturation magnetization.[1-5] Increased Si content makes steel sheets brittle and reduces their processing performance.[6-8] Chromium stainless steels are excellent materials for industrial fields owing to their good mechanical properties and excellent corrosion resistance.[9-12] Si and Cr can also enhance the high-temperature oxidation resistance of Fe-based alloys.[11-14] Therefore, the study of the Fe-Cr-Si system’s phase diagram is essential for industrial-grade, high-performance steels. The three binary systems of Fe-Si,[15-17] Fe-Cr[18-20] and Cr-Si,[21-24] comprising the Fe-Cr-Si ternary system, have previously been investigated. Recently, the binary Fe-Si system was critically re-evaluated by Cui and Jung[16] with two sets of optimized model parameters considering the A2/B2 and B2/D03 order–disorder transitions. A thermodynamic description of the Fe-Cr system was proposed by Jacob et al.,[20] which provided an improved sublattice model of the r phase. Cui and Jung[24] also re-optimized the thermodynamic description for the Cr-Si system, which was consistent with the experimentally measured phase diagram. These researches are adopted in the present work. Seven intermediate phases are known in the Fe-Si system: a2, Fe3Si(a1), Fe2Si, Fe5Si3(g), FeSi(e), bFeSi2, and aFeSi2. The Fe-Cr system has one intermediate phase, r. The Cr-Si system shows t