Microscopic characterisation of brittle fracture initiation in irradiated and thermally aged low-alloy steel welds of a decommissioned reactor pressure vessel

IF 2.8 2区工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY

Journal of Nuclear Materials Pub Date : 2024-09-21 DOI:10.1016/j.jnucmat.2024.155423

N. Hytönen , S. Lindqvist , J. Lydman , Y. Ge , Z. Que , P. Efsing

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引用次数: 0

Abstract

Microstructure has a significant effect on material's integrity and in a heterogeneous weld microstructure the discontinuities affect the brittle fracture initiation and propagation and determine the fracture toughness. The knowledge of brittle fracture initiation mechanisms in high-Mn/high-Ni welds is limited. The brittle fracture initiation behaviour of the decommissioned Barsebäck Unit 2 reactor pressure vessel (RPV) welds of high-Mn/high-Ni weld metal from three different locations, the RPV head and the beltline regions, were investigated and compared with specimens from the surveillance program with high fluence. Systematic fractography has been performed on impact and fracture toughness specimens and the main features of the brittle fracture initiation in the component weld are presented and discussed. Two main types of initiators are identified as the weakest links to initiate the cleavage fracture and the initiation mechanism is found independent from the operation condition. The high-fluence surveillance specimens have a larger amount of intergranular cracking. The cleavage fracture initiation appears to be independent of the operation conditions but dependent on the welding process and metallurgical features. The findings aid in the development of improved material-property correlations which will result in better computational tools for predicting aging of welds based on microstructure.

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退役反应堆压力容器辐照和热老化低合金钢焊缝脆性断裂的显微特征分析

微观结构对材料的完整性有重要影响，在异质焊接微观结构中，不连续性会影响脆性断裂的发生和扩展，并决定断裂韧性。对高锰/高镍焊缝中脆性断裂起始机制的了解十分有限。研究了退役的巴塞拜克 2 号机组反应堆压力容器（RPV）焊缝的脆性断裂起始行为，这些焊缝的高锰/高镍焊缝金属来自三个不同的位置，即 RPV 封头和腰线区域，并与高通量监视计划中的试样进行了比较。对冲击和断裂韧性试样进行了系统的断口分析，并介绍和讨论了组件焊缝中脆性断裂引发的主要特征。确定了两种主要类型的引发剂作为引发劈裂断裂的最薄弱环节，并发现引发机制与操作条件无关。高流变监控试样有较多的晶间裂纹。劈裂断口的引发似乎与操作条件无关，但取决于焊接工艺和冶金特征。这些发现有助于开发更好的材料-性能相关性，从而为根据微观结构预测焊缝老化提供更好的计算工具。

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

Journal of Nuclear Materials 工程技术-材料科学：综合

CiteScore

5.70

自引率

25.80%

发文量

601

审稿时长

63 days

期刊介绍： The Journal of Nuclear Materials publishes high quality papers in materials research for nuclear applications, primarily fission reactors, fusion reactors, and similar environments including radiation areas of charged particle accelerators. Both original research and critical review papers covering experimental, theoretical, and computational aspects of either fundamental or applied nature are welcome. The breadth of the field is such that a wide range of processes and properties in the field of materials science and engineering is of interest to the readership, spanning atom-scale processes, microstructures, thermodynamics, mechanical properties, physical properties, and corrosion, for example. Topics covered by JNM Fission reactor materials, including fuels, cladding, core structures, pressure vessels, coolant interactions with materials, moderator and control components, fission product behavior. Materials aspects of the entire fuel cycle. Materials aspects of the actinides and their compounds. Performance of nuclear waste materials; materials aspects of the immobilization of wastes. Fusion reactor materials, including first walls, blankets, insulators and magnets. Neutron and charged particle radiation effects in materials, including defects, transmutations, microstructures, phase changes and macroscopic properties. Interaction of plasmas, ion beams, electron beams and electromagnetic radiation with materials relevant to nuclear systems.