Casting aluminum alloy faces challenges during service, such as micro defects, low surface hardness, and inadequate fretting fatigue performance. This study employs acousto-electropulsing-stress synergistic strengthening to construct a strengthened layer structure on the surface of casting aluminum alloy, characterized by “micro-defect healing + surface gradient nanostructure.” The results demonstrate that, compared to surface burnishing processing, electro-ultrasonic surface burnishing processing (EUSBP) increases the thickness of the fine-grained layer by 75 % and enhances the amplitude of surface residual compressive stress by 39.3 % while simultaneously achieving micro-defect healing in the surface layer. Through fretting fatigue tests, it is discovered that the fretting fatigue life of EUSBP specimens is significantly higher than that of burnished and original specimens. Fracture surface analysis and damage zone characterization indicate that EUSBP specimens exhibit the best crack propagation resistance and fretting damage resistance. Molecular dynamics simulations reveal that EUSBP specimens enhance their resistance to fretting fatigue damage by utilizing the nano-gradient grain structure to inhibit dislocation motion and reduce the influence range of plastic deformation during the fretting fatigue process, resulting in a reduction of damage depth in the fretting fatigue damage zone by more than 25 %.

中文翻译：

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声-电脉冲-应力协同强化作用下铸造铝合金的表面增强机理及微动疲劳行为研究


铸造铝合金在使用过程中面临微缺陷、表面硬度低和微动疲劳性能不足等挑战。本研究采用声电脉冲应力协同强化技术，在铸造铝合金表面构建了以“微缺陷修复+表面梯度纳米结构”为特征的强化层结构。结果表明，与表面抛光加工相比，电超声表面抛光加工 （EUSBP） 使细晶层的厚度增加了 75%，表面残余压应力的幅度增加了 39.3%，同时实现了表面层的微缺陷修复。通过微动疲劳试验发现，EUSBP 试样的微动疲劳寿命明显高于抛光试样和原始试样。断裂表面分析和损伤区表征表明，EUSBP 试样表现出最佳的抗裂纹扩展性和抗微动损伤能力。分子动力学模拟表明，EUSBP 试样通过利用纳米梯度晶粒结构抑制位错运动并减小微动疲劳过程中塑性变形的影响范围来增强其对微动疲劳损伤的抵抗力，从而使微动疲劳损伤区的损伤深度减少 25% 以上。