Microstructure and properties of high-strength corrosion-resistant Fe-based medium entropy alloys

doi:10.13251/j.issn.0254-6051.2025.01.002

Abstract

Abstract: Using Python language to edit Thermal-Calc instructions for efficient calculation of alloy phase composition, two iron-based medium entropy alloys with L2₁ precipitation ratio greater than 15% were obtained according to design principles. Adopting large deformation cold rolling combined with medium temperature aging process for microstructure control to achieve excellent strength plasticity matching. The results show that the tensile strength and elongation of No.1 alloy are 1592 MPa and 17.50%, respectively, while that of No.2 alloy are 1682 MPa and 13.50%, respectively. At the same time, both the alloys form stable passivation films in a 3.5wt% NaCl solution, with a pitting potential close to 0 V(vs SCE) and good corrosion resistance. The main matrix phase of the two alloys is FCC solid solution, with a small amount of BCC phase. The combination of large deformation cold rolling and medium temperature aging results in the alloy having an incomplete recovery of fine grain structure, accompanied by the formation of multiphase and multi-scale precipitation phases, which form a soft and hard coordination with the FCC matrix to improve the strength and plasticity of the alloy. The combined effect of precipitation strengthening, dislocation strengthening and grain refinement strengthening enhances the strength of alloys. The high plasticity of the alloy is due to the relief of stress concentration during medium temperature aging. The good plasticity of the FCC matrix can effectively slow down the formation and propagation of cracks. In addition, the low mismatch between Heusler_L2₁ phase and the matrix can also slow down the formation of microcracks at the phase boundary, allowing the two medium entropy alloys to maintain high plasticity.

Key words: medium entropy alloy, Thermal-Calc, corrosion resistance, strengthening and toughening mechanism, precipitates

CLC Number:

TG142.71

Dai Chunduo, Li Jiangwen, Guo Chengyu, Zhang Yong, Sun Meihui, Li Tianyi, Gong Li, Pan Yue. Microstructure and properties of high-strength corrosion-resistant Fe-based medium entropy alloys[J]. Heat Treatment of Metals, 2025, 50(1): 12-21.

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