In-situ study the crack initiation mechanism of P92 steel under high-temperature three-point bending fatigue process

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

Materials Characterization Pub Date : 2024-10-17 DOI:10.1016/j.matchar.2024.114447

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Abstract

Various prior austenite grain size (PAGS) of the P92 specimens were obtained after annealing at 950 °C for different times. In-situ three-points bending fatigue tests were carried out to study the crack initiation mechanisms from 550 °C to 650 °C. Results revealed that the microstructure with large PAGS exhibits better cracking resistance during the fatigue process, which restricts the sliding of prior austenite grain boundary (PAGB) and tends to generate large and sparse cracks. Reducing PAGS promotes the plastic deformation and leads to the fast accumulation of fatigue damage at the initial fatigue stage. Fatigue crack at 550 °C is initiated at the prefabricated notch root, which progresses along a specific route mainly due to the intracrystalline slipping mechanism. However, as the temperature increases to 650 °C, sliding of PAGB is enhanced and it mobilizes a larger region coordinating the plastic deformation, ultimately leads to the opening of the notches. Three typical crack models are established based on the evolution of microstructures both on specimen surface and interior. Moreover, a modified θ projection method is proposed trying to predict the accumulated fatigue damage, of which the physical concepts behind the θ parameters are discussed.

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高温三点弯曲疲劳过程下 P92 钢裂纹萌发机制的原位研究

在 950 °C 退火不同时间后，P92 试样获得了不同的先奥氏体晶粒大小（PAGS）。在 550 ℃ 至 650 ℃ 温度范围内进行了原位三点弯曲疲劳试验，以研究裂纹萌发机制。结果表明，PAGS 大的微观结构在疲劳过程中表现出更好的抗开裂性，它限制了先奥氏体晶界（PAGB）的滑动，容易产生大而稀疏的裂纹。降低 PAGS 会促进塑性变形，并导致疲劳初始阶段疲劳损伤的快速积累。550 ℃时的疲劳裂纹始于预制缺口根部，主要由于晶内滑动机制，裂纹沿着特定路线发展。然而，当温度升高到 650 ℃ 时，PAGB 的滑动增强，并动员更大的区域协调塑性变形，最终导致缺口打开。根据试样表面和内部微观结构的演变，建立了三种典型的裂纹模型。此外，还提出了一种修正的 θ 投影方法，试图预测累积疲劳损伤，并讨论了 θ 参数背后的物理概念。

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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.