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利用阳极氧化对7475铝合金进行表面改性处理,通过拉伸疲劳试验,用罗卡提法求出阳极氧化前后7475铝合金的疲劳极限。采用SEM、XRD等手段对阳极氧化前后7475铝合金的断口形貌和组成物相进行了分析,并对阳极氧化前后7475铝合金疲劳断裂机理进行了探讨。结果表明,阳极氧化膜主要是由γ-Al2O3和α-Al2O3组成,膜层越厚,α-Al2O3相含量越多;氧化膜降低了铝合金的疲劳性能,与原始试样相比,膜层厚度为6、8和10μm的试样疲劳极限分别下降了3.2%、3.9%和4.5%;氧化膜在基体原位生长,在界面处基体中产生的残留拉应力促进了疲劳源的萌生,使铝合金的疲劳性能有所降低。
The surface modification of 7475 aluminum alloy was carried out by anodic oxidation, and the fatigue limit of 7475 aluminum alloy before and after anodization was obtained by the tensile fatigue test and Rocard’s method. The fracture morphology and composition phases of 7475 aluminum alloy before and after anodic oxidation were analyzed by SEM and XRD. The fatigue fracture mechanism of 7475 aluminum alloy before and after anodic oxidation was also discussed. The results show that the anodic oxide film is mainly composed of γ-Al2O3 and α-Al2O3. The thicker the film, the more the α-Al2O3 phase content; the oxide film reduces the fatigue performance of the aluminum alloy. Compared with the original sample, The fatigue limits of specimens with thickness of 6, 8 and 10 μm decreased by 3.2%, 3.9% and 4.5% respectively. The oxide film grew in situ in the matrix and the residual tensile stress in the matrix at the interface promoted the initiation of fatigue source Aluminum alloy fatigue performance has decreased.