Effects of Silicon and Aluminum Alloying on Phase Transformation and Microstructure Evolution in Fe–0.2C–2.5Mn Steel: Insights from Continuous–Cooling–Transformation and Time–Temperature–Transformation Diagrams

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research Pub Date : 2024-08-26 DOI:10.1002/srin.202400159

Oguz Gulbay, Alexander Gramlich, Ulrich Krupp

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Abstract

The impact of silicon and aluminum on phase transformation behavior, particularly bainite, and microstructure evolution in Fe–0.2C–2.5Mn steel are presented. Continuous–cooling–transformation (CCT) and time–temperature–transformation (TTT) diagrams are determined experimentally. An aluminum extended empirical formula is introduced to estimate the martensite start temperature (Ms) with a thorough assessment of existing formulae. Results show that aluminum significantly increases Ms and has a stronger influence on promoting ferritic microstructures than silicon. During continuous cooling, alongside bainite, formation of Widmanstätten structures is induced in aluminum‐alloyed steel at higher cooling rates due to increased prior austenite grain size. Silicon decelerates bainite transformation kinetics by enhancing austenite's chemical stability through carbon enrichment via preventing carbide precipitation and by strengthening austenite against displacive phase transformation via solid solution hardening. Although aluminum has similar effects, incubation time is shortened during isothermal treatment because of the increased driving force, which overcompensates for the retardation effects. A finer carbide‐free bainitic microstructure is achieved in aluminum‐alloyed steel with more pronounced film‐like retained austenite (RA) formation and superior carbon enrichment, improving RA stability and suppressing martensite–austenite island formation. Finally, with the proposed formula, an accurate approximation to experimental Ms is accomplished.

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硅和铝合金对 Fe-0.2C-2.5Mn 钢中相变和显微组织演变的影响：从连续冷却-转变和时间-温度-转变图中获得的启示

介绍了硅和铝对 Fe-0.2C-2.5Mn 钢中相变行为（尤其是贝氏体）和微观结构演变的影响。通过实验确定了持续冷却-转变（CCT）和时间-温度-转变（TTT）图。通过对现有公式的全面评估，引入了铝扩展经验公式来估算马氏体起始温度（Ms）。结果表明，与硅相比，铝会明显增加 Ms，对促进铁素体微观结构的影响更大。在连续冷却过程中，由于奥氏体晶粒尺寸增大，铝合金钢在较高的冷却速率下，除了贝氏体之外，还会形成维德曼斯泰滕结构。硅通过富碳防止碳化物析出，从而增强奥氏体的化学稳定性，并通过固溶硬化加强奥氏体的位移相变，从而减缓贝氏体转变动力学。虽然铝也有类似的作用，但在等温处理过程中，由于驱动力增加，孵化时间缩短，从而弥补了延缓作用。在铝合金钢中可获得更精细的无碳化物贝氏体显微组织，形成更明显的膜状残余奥氏体（RA）和更优越的碳富集，从而提高 RA 的稳定性并抑制马氏体-奥氏体岛的形成。最后，利用所提出的公式，可以精确地近似于实验 Ms。

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来源期刊

Accounts of Chemical Research 化学-化学综合

CiteScore

31.40

自引率

1.10%

发文量

312

审稿时长

2 months

期刊介绍： Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance. Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.