Purpose

This study aims to investigate the fatigue crack propagation behavior of SiC particle-reinforced 2124 Al alloy composites under constant amplitude axial loading at a stress ratio of R = 0.1. For this purpose, it is performed experiments and comparatively analyze the results by producing 5, 10, 15 Vol.% SiCp-reinforced composites and unreinforced 2124 Al alloy billets with powder metallurgy (PM) production technique.

Design/methodology/approach

With the PM production technique, SiCp-reinforced composite and unreinforced 2124 Al alloy billets were produced at 5%, 10%, 15% volume ratios. After the produced billets were extruded and 5 mm thick plates were formed, tensile and fatigue crack propagation compact tensile (CT) samples were prepared. Optical microscope examinations were carried out to determine the microstructural properties of billet and samples. To determine the SiC particle–matrix interactions due to the composite microstructure, unlike the Al alloy, which affects the crack initiation life and crack propagation rate, detailed scanning electron microscopy (SEM) studies have been carried out.

Findings

Optical microscope examinations for the determination of the microstructural properties of billet and samples showed that although SiC particles were rarely clustered in the Al alloy matrix, they were generally homogeneously dispersed. Fatigue crack propagation rates were determined experimentally. While the highest crack initiation resistance was achieved at 5% SiC volume ratio, the slowest crack propagation rate in the stable crack propagation region was found in the unreinforced 2124 Al alloy. At volume ratios greater than 5%, the number of crack initiation cycles decreases and the propagation rate increases.

Originality/value

As a requirement of damage tolerance design, the fatigue crack propagation rate and fatigue behavior of materials to be used in high-tech vehicles such as aircraft structural parts should be well characterized. Therefore, safer use of these materials in critical structural parts becomes widespread. In this study, besides measuring fatigue crack propagation rates, the mechanisms causing crack acceleration or deceleration were determined by applying detailed SEM examinations.

中文翻译：

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SiC颗粒增强铝合金基复合材料疲劳裂纹扩展速率及扩展机制

目的

本研究旨在研究SiC颗粒增强2124铝合金复合材料在应力比R = 0.1下等幅轴向载荷下的疲劳裂纹扩展行为。为此，采用粉末冶金（PM）生产技术生产5、10、15 Vol.% SiCp增强复合材料和非增强2124铝合金坯料，进行实验并对结果进行对比分析。

设计/方法论/途径

采用PM生产技术，生产了体积比为5%、10%、15%的SiCp增强复合材料和非增强2124铝合金坯料。将生产的坯料挤压并形成 5 mm 厚的板材后，制备拉伸样品和疲劳裂纹扩展致密拉伸 (CT) 样品。进行光学显微镜检查以确定坯料和样品的微观结构特性。为了确定复合材料微观结构引起的 SiC 颗粒-基体相互作用（与影响裂纹萌生寿命和裂纹扩展速率的铝合金不同），进行了详细的扫描电子显微镜 (SEM) 研究。

发现

用于测定坯料和样品显微组织性能的光学显微镜检查表明，虽然 SiC 颗粒很少聚集在铝合金基体中，但它们通常均匀分散。疲劳裂纹扩展速率通过实验确定。虽然 SiC 体积比为 5% 时获得了最高的抗裂纹萌生能力，但未增强的 2124 铝合金在稳定裂纹扩展区域中的裂纹扩展速率最慢。当体积比大于 5% 时，裂纹萌生循环次数减少，扩展速率增加。

原创性/价值

作为损伤容限设计的要求，应该很好地表征飞机结构件等高科技车辆所用材料的疲劳裂纹扩展速率和疲劳行为。因此，在关键结构部件中更安全地使用这些材料变得越来越普遍。在这项研究中，除了测量疲劳裂纹扩展速率外，还通过详细的 SEM 检查确定了导致裂纹加速或减速的机制。