为了确定稀土元素Sc对T6态铸造Al-9.0%Si-4.0%Cu-0.4%Mg合金(质量分数)的低周疲劳行为的影响规律, 研究了T6态铸造Al-9.0%Si-4.0%Cu-0.4%Mg合金和Al-9.0%Si-4.0%Cu-0.4%Mg-0.3%Sc合金的低周疲劳行为. 结果表明, 在低的外加总应变幅下, Al-9.0%Si-4.0%Cu-0.4%Mg合金在整个疲劳变形期间均表现为循环应变硬化, Al-9.0%Si- 4.0%Cu-0.4%Mg-0.3%Sc合金在疲劳变形初期表现为循环应变硬化, 在疲劳变形后期则表现为循环稳定; 当外加总应变幅较高时, Al-9.0%Si-4.0%Cu-0.4%Mg(-0.3%Sc)合金均呈现循环应变硬化. Sc的加入可以有效地提高T6态Al-9.0%Si-4.0%Cu-0.4%Mg合金的循环变形抗力和低周疲劳寿命. 在较低的外加总应变幅下, T6态Al-9.0%Si- 4.0%Cu-0.4%Mg(-0.3%Sc)合金的循环变形机制为平面滑移, 当外加总应变幅较高时则为波状滑移机制.

The Al-Si-Cu-Mg cast aluminum alloys have high mechanical properties and good cast performance. Due to their excellent comprehensive properties, the Al-Si-Cu-Mg cast aluminum alloys have wide application, and have become one of the most important structural materials applied in the equipment manufacturing industry. Actually, many key components in practical engineering application are often subjected to the alternating load, and thus the fatigue failure has become an important factor which concerns the safety and economy for those structures used in various engineering fields. Although some researches for the fatigue behavior of aluminum alloys have been performed, mainly focus on the regularity understanding. Especially, the influences of rare earth elements and heat-treat condition on the low-cycle fatigue behavior of aluminum alloys have not been comprehensively revealed. Obviously, the investigation concerning the microstructure and fatigue property of the Al-Si-Cu-Mg cast aluminum alloys can not only provide the theoretical basis for the development of new type cast aluminum alloys but also the reliable theoretical foundation for the safety design and reasonable use of these alloys. In order to determine the influence of rare earth element Sc on the low-cycle fatigue behavior of casting Al-9.0%Si-4.0%Cu-0.4%Mg alloy with T6 treated state, the cyclic stress response behavior, fatigue life behavior and cyclic deformation mechanism of the Al-9.0%Si-4.0%Cu-0.4%Mg(-0.3%Sc) cast aluminum alloys with T6 treated states under low-cycle fatigue loading condition were investigated. The results show that at the low total strain amplitude, the Al-9.0%Si-4.0%Cu-0.4%Mg alloy exhibits the cyclic strain hardening during whole fatigue deformation, while the Al-9.0%Si-4.0%Cu-0.4%Mg-0.3%Sc alloys exhibit the cyclic strain hardening in the initial stage of fatigue deformation and then the stable cyclic stress response in the later stage of fatigue deformation. At the higher total strain amplitudes, the Al-9.0%Si-4.0%Cu-0.4%Mg(-0.3%Sc) alloys exhibit the cyclic strain hardening. The addition of Sc can effectively enhance the cyclic deformation resistance and prolong the fatigue lives of the Al-9.0%Si-4.0%Cu-0.4%Mg alloy with T6 treated state. At the lower total strain amplitudes, the cyclic deformation mechanism of the Al-9.0%Si-4.0%Cu-0.4%Mg(-0.3%Sc) alloys with T6 treated state is the plane slip, while at the higher total strain amplitudes, the cyclic deformation mechanism becomes the wavy slip.