The influence of iron (Fe)-containing constituent particles on the behavior of fatigue crack initiation and propagation of Al-Cu-Li-Mg-Zr alloys has been studied using fatigue crack growth (FCG) tests and in-situ fatigue testing and detailed metallographic examination based on scanning electron microscopy. Experimental results show that the alloy with a low level of Fe content (2A97-T3 sheet) exhibited a lower density, accompanying equivalent tensile strength and FCG rate compared to the damage-tolerant 2524-T3 sheet. It was found that the fatigue b growth of both alloys is dominated by transgranular mode, accompanied by intergranular expansion, and the high level of Fe content alloy presents more characteristics of intergranular. Coarse constituent particles were detrimental to the resistance against FCG. It is postulated here that the micro-cracks formed around the coarse Fe-containing particles are merged with the primary crack to produce a bridging effect, accelerating the growth of fatigue cracks in the alloy with a high level of Fe content.

中文翻译：

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Al-Cu-Li-Mg-Zr合金的固有疲劳裂纹扩展：铁成分颗粒的影响

使用疲劳裂纹扩展（FCG）试验和原位疲劳试验研究了含铁成分颗粒对Al-Cu-Li-Mg-Zr合金疲劳裂纹萌生和扩展行为的影响，并详细基于扫描电子显微镜的金相检查。实验结果表明，与耐损伤的2524-T3板相比，低铁含量的合金（2A97-T3板）表现出较低的密度，并具有同等的拉伸强度和FCG率。结果表明，两种合金的疲劳b生长均以晶界为主，并伴随晶间膨胀，而高含量的Fe含量合金则表现出更多的晶界特征。粗大的组成颗粒不利于抵抗FCG。