LY12铝合金微弧氧化涂层组织结构对基体疲劳性能的影响

在硅酸盐体系电解液中于铝合金表面制备出不同厚度的微弧氧化涂层,研究涂层厚度对基体疲劳寿命的影响,并揭示疲劳损伤机制.采用XRD、SEM、EDS等分析手段分析涂层的物相与组织结构.用810 Material Test System 疲劳试验机评价涂层试样的疲劳寿命.结果表明,铝合金微弧氧化涂层主要由γ-Al_2O_3和a-Al_2O_3组成,涂层内层致密,表面多微孔.随氧化时间延长,涂层厚度增大,但表面粗糙度增加.疲劳测试结果表明,微弧氧化涂层会降低基底铝合金的疲劳寿命,涂层厚度增加,疲劳寿命下降显著.相对于基体铝合金,涂层厚度为10,18,30 mm的试样,疲劳寿命分别下降了4.4%,8.5%,32.2%.疲劳断口分析认为,涂层局部过度长入基体产生缺陷部位,在循环载荷作用下,容易产生应力集中,从而萌生疲劳源,使铝合金的疲劳寿命下降.

Influence of Coating Microstructure on Fatigue Performance of Microarc Oxidation Coated LY12 Alloy Specimen

The microarc oxidation coatings with different thickness were fabricated on LY12 alloy in silicate electrolyte system. The effect of the coating thickness on fatigue life was evaluated. The phase composition and microstructure of the coatings were determined by XRD, SEM and EDS etc, and the corresponding fatigue damage mechanism was revealed by 810 material fest system. The results show that the microarc oxidation coatings formed on LY12 alloy is mainly composed of γ-Al_2O_3 and α-Al_2O_3, dense in the inner layer and porous in the outer layer. The microarc oxidation coatings induce the decrease of fatigue life for the coated specimen. The fatigue life reduces by 4.39%, 8.51% and 32.24% for the 10, 18 and 30 μm thick coated specimens respectively, than that of the alloy substrate. The over growth of the coating into the substrate can contribute to the stress concentration under cycle loading, and finally cause fatigue damage, decreasing the fatigue life.