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采用轴向加载疲劳试验方法,研究了航空用2124-T851铝合金板材不同取样方向、试样形式以及实验应力比下的疲劳性能;并通过金相显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)分析了该合金的显微组织和疲劳断口形貌。结果表明:2124-T851铝合金板材具有良好的耐疲劳损伤性能,疲劳极限随应力比的增加而增大;缺口的存在大大降低了材料的疲劳极限,光滑试样(K t=1)的疲劳极限大约是缺口试样(K t=3)的2倍;板材横向疲劳极限高于纵向疲劳极限,且应力比越小差异越大。断口形貌具有典型的疲劳断口特征,由疲劳源区、疲劳裂纹稳定扩展区和快速断裂区三部分组成,裂纹萌生一般位于表面夹杂或缺口等缺陷引起的应力集中处。
The fatigue behavior of 2124-T851 aluminum alloy sheet for aviation under different loading directions, specimen forms and experimental stress ratios was studied by axial loading fatigue test. The microstructure and mechanical properties of the 2124-T851 aluminum alloy sheet were studied by OM, SEM and TEM. The microstructure and fatigue fracture morphology of the alloy were analyzed by TEM. The results show that the 2124-T851 aluminum alloy sheet has good fatigue resistance and the fatigue limit increases with the increase of the stress ratio. The existence of the notch greatly reduces the fatigue limit of the material, and the fatigue of the smooth specimen (K t = 1) The limit is about twice as large as the notched specimen (K t = 3); the transverse fatigue limit of the plate is higher than the longitudinal fatigue limit, and the smaller the stress ratio, the greater the difference. The fracture surface is characterized by typical fatigue fracture. It consists of three parts: the source zone of fatigue, the stable expansion of fatigue crack and the rapid fracture zone. Crack initiation is usually located in the stress concentration point caused by defects such as surface inclusions or notches.