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选用第3代铝锂合金2198-T8材料,对其力学以及高周疲劳性能进行了研究。结果表明,相对于其它航空铝合金材料,2198-T8在抗拉强度和屈服强度上均有不同程度的提升,并具有较强的抗疲劳性能,但疲劳数据的离散性却随着施加应力的减小而增大。利用扫描电子显微镜(SEM)及其自带的能谱分析(EDS)功能对疲劳裂纹萌生机理进行深入研究。研究发现,位错的增殖、运动和塞积是2198-T8疲劳裂纹萌生的主要原因,疲劳裂纹易于从驻留滑移带(PSB)以及挤出带形成的粗糙区域萌生。不同应力状态下,由材料内部缺陷引起的疲劳断裂现象是致命的,对疲劳寿命有巨大影响,最高可使疲劳寿命降低90%以上。裂纹萌生机制的不同可引起疲劳寿命的较大变化,合理地解释了疲劳数据的离散性问题。
The 3rd generation Al-Li alloy 2198-T8 was selected to study its mechanical properties and high-cycle fatigue properties. The results show that compared with other aviation aluminum alloy materials, 2198-T8 has different degrees of tensile strength and yield strength improvement, and has a strong anti-fatigue performance, but the dispersion of fatigue data but with the stress Reduce and increase. The mechanism of fatigue crack initiation was further studied by scanning electron microscopy (SEM) and its own energy spectrum analysis (EDS). It is found that the dislocation proliferation, motility and plugging are the main causes of 2198-T8 fatigue crack initiation, and the fatigue cracks tend to germinate from the localized slip zone (PSB) and the rough zone formed by the extrusion zone. Under different stress conditions, the fatigue fracture caused by the material internal defects is fatal and has a huge impact on the fatigue life, which can reduce the fatigue life by more than 90%. Different crack initiation mechanisms can cause large changes in fatigue life, and reasonably explain the discreteness of fatigue data.