Aging precipitation behavior of 445 ultra-purified ferritic stainless steel with different Mo contents

doi:10.13251/j.issn.0254-6051.2024.12.027

Abstract

Abstract: Types of equilibrium precipitated phases in 445 ultra-purified ferritic stainless steel with different Mo content (0.68%, 1.79% and 2.37%) were analyzed by Thermo-Calc thermodynamic software. The specimens were annealed at 1020 ℃ for 10 min and aged at 700 ℃/870 ℃ for 1 h. The SEM and TEM methods were used to study the precipitation of second phases in the 445 stainless steel after annealing and aging. The results show that the types of equilibrium precipitates calculated by Thermo-Calc are basically consistent with the experimental results of microstructure observation and phase analysis. The second phases with different morphologies are precipitated in the aged 445 stainless steel, including Laves phase Fe₂(Nb, Mo) with strip-like shape distributing inside the grain and (Nb, Ti)C carbides with irregular granular shape presenting inside the grain and at the grain boundaries. There is remarkable difference in sensitivity of precipitated phases for the 445 ultra-purified ferritic stainless steel with different Mo contents. As the Mo content increases, the precipitation temperature of second phase rises and the amount of second phase precipitation also increases at the same aging temperature.

Key words: Thermo-Calc software, ferritic stainless steel, second phase, aging

CLC Number:

TG156.1

Li Jianchun, Jia Yuanwei. Aging precipitation behavior of 445 ultra-purified ferritic stainless steel with different Mo contents[J]. Heat Treatment of Metals, 2024, 49(12): 163-168.

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