预腐蚀条件下不同孔数冷挤压强化7075-T6铝合金板件疲劳寿命退化规律

目的 研究腐蚀环境下单孔和多孔冷挤压强化铝合金板件的疲劳寿命退化规律和损伤机理。方法 针对2种不同孔距的三孔冷挤压强化7075-T6铝合金板件，采用模拟热带海洋大气环境的实验室加速腐蚀谱，开展不同腐蚀时间下的预腐蚀疲劳试验。结果 获得了3倍孔距的三孔挤压强化铝板以及单孔挤压强化铝板的C(t)曲线、疲劳S-N曲线和损伤形貌特征，分析了腐蚀后挤压强化试件的腐蚀机理及挤压强化作用。同时，将不同孔数试件的试验结果进行比较，探明了孔数对挤压强化铝板腐蚀和疲劳性能的影响。结论 腐蚀后挤压强化铝合金板件的疲劳性能发生显著退化，腐蚀损伤主要为剥蚀，疲劳裂纹萌生位置由孔边转移至表面。挤压孔数量对挤压强化铝合金板件的疲劳和腐蚀疲劳性能的影响较小。

Fatigue Life Degradation of 7075-T6 Aluminum Alloy Sheets Strengthened by Cold Extrusion with Different Number of Holes under Pre-corrosion Condition

The work aims to study the fatigue life degradation law and damage mechanism of aluminum alloy sheets strengthened by single-hole and multi-hole cold extrusion in corrosive environment. Two kinds of three-hole cold extrusion strengthened 7075-T6 aluminum alloy sheets with different hole spacing were used to carry out pre-corrosion fatigue tests for different corrosion time in laboratory accelerated corrosion spectrum simulating tropical marine atmospheric environment. The C(t) curve, fatigue S-N curve and damage morphology characteristics of three-hole extrusion strengthened aluminum sheets and single-hole extrusion strengthened aluminum sheets with triple hole spacing were obtained, and the corrosion mechanism and extrusion strengthening effect of extrusion strengthened specimens after corrosion were analyzed. At the same time, the experimental results of specimens with different number of holes were compared, and the effect of the number of holes on the corrosion and fatigue properties of extrusion strengthened aluminum sheets was explored. The results show that the fatigue performance of the extruded aluminum alloy sheet after corrosion is significantly degraded, the corrosion damage is mainly denudation, and the fatigue crack initiation position is transferred from the hole edge to the surface. The number of extrusion holes has little effect on the fatigue and corrosion fatigue performance of extrusion strengthened aluminum alloy sheets.