Wenguang Liao , Veronika Mazánová , Milan Heczko , Wenkao Hou , John Procario , Michael J. Mills , Xun Liu
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引用次数: 0
Abstract
Niobium (Nb) is a widely recognized micro-alloying element due to its low cost and substantial impact on steel properties. While the effect of Nb in processed steels has been well investigated, studies on its elemental distribution and precipitation behavior in weld metal remain scarce. This study focuses on the weld metal of specially designed Nb-rich X70 pipeline steel by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) characterization, complemented with thermodynamic and kinetics modeling analysis. In the majority of the weld, Nb was essentially uniformly distributed. This suggests that Nb primarily exists in the solid solution form in the weld metal, which is also supported by precipitation kinetics modeling results. This is primarily due to the short thermal history associated with the welding process, which leads to insufficient time for the uniform precipitation of Nb. Two instances of Nb precipitates were observed at the weld centerline and reinforcement region. The low partition coefficient of Nb results in an elevated local concentration along the weld centerline. However, precipitation kinetics calculations suggest that this enhancement alone is not adequate to induce precipitate formation. The occurrence of MnS and the prior formation of Ti precipitates may provide heterogeneous nucleation sites for Nb, facilitating the nucleation of Nb precipitates in the weld centerline and reinforcement region.
铌(Nb)是一种被广泛认可的微合金元素,因其成本低且对钢的性能有重大影响。虽然铌在加工钢中的影响已经得到了很好的研究,但有关其元素分布和在焊接金属中的析出行为的研究仍然很少。本研究通过扫描透射电子显微镜(STEM)和能量色散 X 射线光谱(EDS)表征,并辅以热力学和动力学建模分析,重点研究了专门设计的富铌 X70 管线钢的焊缝金属。在大部分焊缝中,铌基本上均匀分布。这表明铌主要以固溶体形式存在于焊缝金属中,沉淀动力学建模结果也证明了这一点。这主要是由于焊接过程的热历史较短,导致铌没有足够的时间均匀析出。在焊接中心线和加固区域观察到两次铌析出。由于铌的分配系数较低,导致沿焊接中心线的局部浓度升高。然而,沉淀动力学计算表明,仅靠这种提高不足以诱导沉淀形成。MnS 的出现和之前 Ti 沉淀的形成可能为 Nb 提供了异质成核位点,促进了 Nb 沉淀在焊接中心线和加固区域的成核。
期刊介绍:
Materialia is a multidisciplinary journal of materials science and engineering that publishes original peer-reviewed research articles. Articles in Materialia advance the understanding of the relationship between processing, structure, property, and function of materials.
Materialia publishes full-length research articles, review articles, and letters (short communications). In addition to receiving direct submissions, Materialia also accepts transfers from Acta Materialia, Inc. partner journals. Materialia offers authors the choice to publish on an open access model (with author fee), or on a subscription model (with no author fee).