The strength of non-heat-treatable 5xxx Al alloys is derived from solid solution strengthening and strain hardening, the absence of a precipitation strengthening response results in their lower strength. In this study, significant improvements in strength can be achieved by subjecting three different Mg concentrations 5xxx Al alloys to cyclic plasticity. A quantitative analysis of the respective contributions to the yield strength has been conducted by combining transmission electron microscopy and atom probe tomography. Additionally, the fatigue performance and fatigue mechanism of the cyclic strengthened 5xxx Al alloys have been thoroughly studied due to its transformation from non-heat-treatable to precipitation strengthening. We demonstrate that the high-cycle fatigue (HCF) strength of the cyclically strengthened state only experiences a minor improvement compared to the as-received state, which is significantly disproportionate to the enhancement in tensile strength. This disparity is primarily attributed to the changes in microstructure and fatigue mechanisms, resulting in a reduction in fatigue ratio. This study provides important insights for expanding research on cyclic plasticity methods in fatigue performance, and can aid in the development of improved processes for optimal fatigue resistance.

中文翻译：

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阐明循环塑性对 5xxx Al 合金强化机制和疲劳性能的影响


不可热处理的 5xxx Al 合金的强度来自固溶强化和应变硬化，没有沉淀强化响应导致其强度较低。在本研究中，通过对三种不同 Mg 浓度的 5xxx Al 合金进行循环塑性，可以显著提高强度。通过结合透射电子显微镜和原子探针断层扫描，对各自对屈服强度的贡献进行了定量分析。此外，由于循环强化 5xxx Al 合金从不可热处理转变为沉淀强化，其疲劳性能和疲劳机制已被深入研究。我们证明，与接收状态相比，循环强化状态的高周疲劳 （HCF） 强度仅略有提高，这与拉伸强度的增强明显不成比例。这种差异主要归因于微观结构和疲劳机制的变化，导致疲劳率降低。这项研究为扩大疲劳性能中循环塑性方法的研究提供了重要见解，并有助于开发改进工艺以实现最佳抗疲劳性。