利用旋转弯曲疲劳试验机研究了三种膜厚(10μm、15μm、20μm)的微弧氧化处理LD10铝合金的疲劳性能;采用SEM观察微弧氧化试样的表面、截面以及断口形貌;利用XRD分析微弧氧化试样的表面相组成和表面残余应力.结果表明:微弧氧化膜层由AISi_(0.5)O_(2.5)非晶相组成,膜层中的微裂纹起源于放电通道(微孔),终止在通道附近区域;膜层附近基体中存在残余拉应力,促使疲劳裂纹在此形成和扩展,导致10 μm、15μm、20 μm三种膜厚的微弧氧化处理铝合金的疲劳寿命分别下降了63%、75%和65%,疲劳极限分别下降了9.5%、7.9%和9.9%.
Micro-arc oxidation(MAO) coatings with different thicknesss (10 tam,15μm and 20μm) were deposited on LD10 Al alloy samples using MAO processing. The samples were tested using a rotating bending fatigue tester to character their fatigue properties. Scanning electron microscopy (SEM) was used to observe the microstructure and fatigue fracture morphology of the specimen with MAO coatings. X-ray diffraction (XRD) was employed to analyze the phases and residual stress in the coatings. The results show that the MAO coating is mainly composed of AlSi_(0.5)O_(2.5) amorphous phase,and the net micro-cracks observed in the coating initiate in the discharge channel and end at the region near the discharge channel. The tensile residual stress presented at the interface of the sabstrate and the coating induces early crack initiation and propagation. Compared to the sample without MAO coating,the reduction of fatigue life are 63%,75% and 65%,and the reduction of fatigue limit are 9.5%,7.9% and 9.9% for the samples with the MAO coatings thickness of 10tam,15μm and 20μm,respectively.
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