Unravelling the subgrain stabilities of microstructures across P91 steel weld joint under creep-fatigue interaction loading waveforms through EBSD and synchrotron based XRD studies

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization Pub Date : 2025-04-17 DOI:10.1016/j.matchar.2025.115062

P. Vaishali , Vani Shankar , Ashok Bhakar , Sanjay Rai

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引用次数: 0

Abstract

The aim of the present work is to be able to explain the subgrain stability/changes in the perspective of statistically stored dislocations(SSDs) and geometrically necessary dislocations (GNDs) and the resultant dislocation characters due to their interactions in the various microstructural zones of P91 steel weld joint (WJ) under the effects of different types of creep-fatigue interaction (CFI) loading waveforms. Towards this, five different combinations of simultaneous creep and fatigue loadings in the CFI waveforms and one low cycle fatigue loading (i.e. with no creep hold) were utilized for experimentation. The susceptibility of the subgrains to coarsening depend upon the microstructural zone in consideration (i.e. hard zones (weld metal and coarse grain heat affected zone) or soft zones (base metal, intercritical heat affected zone and fine grain heat affected zone) of P91 steel WJ), asymmetricity/symmetricity of the CFI waveforms applied (i.e. application of either tensile or compressive hold alone or both tensile and compressive holds) and the extents of creep/fatigue contributions (short or long holds) in the CFI loadings. Since the resultant subgrains formed in the various microstructural zones across the P91 steel WJ under different cyclic loading waveforms are the complex interplay of dislocation-dislocation interactions among the initial dislocations, production and annihilations, the net dislocation densities have been determined in terms of GNDs and SSDs. The outcome of the study was that, while GNDs may primarily influence the overall cyclic softening of the P91 steel weld joint, the SSDs determined the resultant substructure sizes.

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利用EBSD和基于同步加速器的XRD研究了蠕变-疲劳相互作用加载波形下P91钢焊缝微观组织的亚晶稳定性

本研究的目的是在不同类型的蠕变-疲劳相互作用（CFI）加载波形的作用下，从统计存储位错（ssd）和几何必要位错（GNDs）的角度解释它们在P91钢焊接接头（WJ）的各个显微组织区域中的相互作用所导致的亚晶稳定性/变化以及由此产生的位错特征。为此，在CFI波形中使用五种不同的同时蠕变和疲劳载荷组合以及一种低周疲劳载荷（即无蠕变保持）进行实验。亚晶对粗化的敏感性取决于所考虑的组织区(即P91钢WJ的硬区（焊缝金属和粗晶热影响区）或软区（母材、临界间热影响区和细晶热影响区）。应用的CFI波形的不对称性/对称性（即单独应用拉伸或压缩货舱或同时应用拉伸和压缩货舱）和CFI载荷的蠕变/疲劳贡献程度（短货舱或长货舱）。由于在不同循环加载波形下，在P91钢WJ的各个显微组织区形成的亚晶粒是初始位错、产生和湮灭之间位错-位错相互作用的复杂相互作用，因此确定了GNDs和ssd的净位错密度。研究结果表明，虽然GNDs可能主要影响P91钢焊接接头的整体循环软化，但ssd决定了最终的子结构尺寸。

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来源期刊

Materials Characterization 工程技术-材料科学：表征与测试

CiteScore

7.60

自引率

8.50%

发文量

746

审稿时长

36 days

期刊介绍： Materials Characterization features original articles and state-of-the-art reviews on theoretical and practical aspects of the structure and behaviour of materials. The Journal focuses on all characterization techniques, including all forms of microscopy (light, electron, acoustic, etc.,) and analysis (especially microanalysis and surface analytical techniques). Developments in both this wide range of techniques and their application to the quantification of the microstructure of materials are essential facets of the Journal. The Journal provides the Materials Scientist/Engineer with up-to-date information on many types of materials with an underlying theme of explaining the behavior of materials using novel approaches. Materials covered by the journal include: Metals & Alloys Ceramics Nanomaterials Biomedical materials Optical materials Composites Natural Materials.