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利用SEM观察了疲劳裂纹在具有片层组织的TC4ELI合金中的扩展路径,通过统计疲劳裂纹与α片层所呈的角度,分析了α和β两相晶体学取向对疲劳裂纹扩展路径的影响.基于对疲劳裂纹扩展路径的研究,测试并讨论了片层组织中晶粒和α片层对近门槛值阶段及Paris区阶段疲劳裂纹扩展速率的影响.研究表明,疲劳裂纹在片层组织中扩展时,疲劳裂纹在穿过α片层时倾向于沿平行或垂直于α片层的方向扩展,导致疲劳裂纹扩展路径每隔几个片层宽度出现扩展台阶;影响近门槛值阶段疲劳裂纹扩展速率的主要因素是α片层厚度,而与晶粒尺寸无关;在Paris阶段,晶粒尺寸、α片层厚度和片层长/宽比均对裂纹扩展速率产生影响.
The extension path of fatigue crack in TC4ELI alloy with lamellar microstructure was observed by SEM. The influence of α and β two-phase crystallographic orientation on fatigue crack propagation path was analyzed by counting the angle between fatigue crack and α lamella. Based on the study of fatigue crack propagation path, the effects of grain and α sheet on the near-threshold value and the fatigue crack growth rate in the Paris zone were tested and discussed. The results show that the fatigue crack propagates in the lamellar structure , Fatigue cracks tend to propagate parallel or perpendicular to the α sheet as they pass through the α sheet, resulting in an extended step in the fatigue crack propagation path every few sheet widths; affecting the fatigue crack growth rate near the threshold value The main factor is the thickness of α sheet, which is independent of the grain size. In the Paris stage, the grain size, the thickness of α sheet and the length / width ratio of the sheet both influence the crack growth rate.