Modelling the kinetics of bainite transformation with pre-existing martensite in High-Si steels

IF 1.9 3区材料科学 Q4 CHEMISTRY, PHYSICAL

Calphad-computer Coupling of Phase Diagrams and Thermochemistry Pub Date : 2026-03-01 Epub Date: 2025-12-08 DOI:10.1016/j.calphad.2025.102898

Yong Li , Keming Mao , Shan Chen , Chenchong Wang , Wei Xu

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Abstract

Bainite is a crucial microstructure in steel, and its transformation kinetics plays a key role in microstructural control and property optimisation. Conventionally, bainite formation initiates at austenite grain boundaries and continues through autocatalytic nucleation at the newly formed bainitic ferrite/austenite interfaces. However, recent studies have revealed that the presence of martensite prior to the austenite-to-bainite transformation can significantly alter the transformation behaviour. In this work, within the framework of the displacive mechanism, a new isothermal kinetic model is proposed by introducing the catalytic effect of martensite/austenite interfaces to characterise the influence of pre-existing martensite on bainite transformation in high-Si steels. The model was validated through dilatometry experiments performed on two Fe-C-Mn-Si steels with different Mn contents, under both above-Ms and below-Ms temperature conditions. The results demonstrate that bainite transformation exhibits an incubation period above Ms, whereas below Ms, the pre-existing martensite markedly shortens the incubation stage and accelerates the initial transformation rate. There is a high level of agreement between the model predictions and the experimental observations, successfully capturing the key features of the transformation behaviour, including transformation rate, incubation period, final fraction, and the incomplete transformation phenomenon.

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高硅钢中预先存在马氏体的贝氏体转变动力学模拟

贝氏体是钢中重要的微观组织，其相变动力学对钢的组织控制和性能优化起着关键作用。通常，贝氏体的形成始于奥氏体晶界，并在新形成的贝氏体铁素体/奥氏体界面上通过自催化成核继续形成。然而，最近的研究表明，在奥氏体向贝氏体转变之前，马氏体的存在可以显著改变转变行为。本文在驱替机制的框架内，通过引入马氏体/奥氏体界面的催化作用，提出了一个新的等温动力学模型，以表征预先存在的马氏体对高硅钢贝氏体转变的影响。通过对两种不同Mn含量的Fe-C-Mn-Si钢在高于ms和低于ms温度条件下的膨胀实验验证了该模型。结果表明：在Ms以上，贝氏体相变有一个孕育期，而在Ms以下，马氏体的存在明显缩短了孕育期，加快了初始相变速率。在模型预测和实验观测之间有高度的一致性，成功地捕获了转变行为的关键特征，包括转变速率、潜伏期、最终分数和不完全转变现象。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Calphad-computer Coupling of Phase Diagrams and Thermochemistry 化学-热力学

CiteScore

4.00

自引率

16.70%

发文量

审稿时长

2.5 months

期刊介绍： The design of industrial processes requires reliable thermodynamic data. CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) aims to promote computational thermodynamics through development of models to represent thermodynamic properties for various phases which permit prediction of properties of multicomponent systems from those of binary and ternary subsystems, critical assessment of data and their incorporation into self-consistent databases, development of software to optimize and derive thermodynamic parameters and the development and use of databanks for calculations to improve understanding of various industrial and technological processes. This work is disseminated through the CALPHAD journal and its annual conference.