Incoloy 825镍基合金的低周疲劳行为

为了研究Incoloy 825镍基合金的循环应力响应行为和低周疲劳行为,在室温和760℃下进行外加总应变幅控制下的疲劳实验,确定了合金在不同温度下的应变疲劳参数.利用透射电子显微镜和扫描电子显微镜分析了合金疲劳变形后的位错亚结构与断口形貌.结果表明,室温下合金呈现先循环硬化后循环软化的特征,而在760℃下合金则呈现先循环硬化后循环软化或循环稳定的特征.在不同温度下合金的塑性应变幅、弹性应变幅与断裂时的载荷反向周次之间均呈现单斜率线性关系,并分别服从Coffin-Manson和Basquin公式.在室温和760℃下合金的低周疲劳变形机制主要为平面滑移,且疲劳裂纹均以穿晶方式萌生和扩展.

Low-cycle fatigue behavior of Incoloy 825 nickel-based alloy

In order to investigate the cyclic stress response behavior and low-cycle fatigue behavior of Incoloy 825 nickel-based alloy, the applied total strain amplitude controlled fatigue tests at both room temperature and 760 ℃ were carried out, and the strain fatigue parameters of the alloy at different temperatures were determined. The dislocation substructures and morphologies of fracture surfaces for the alloy after low-cycle fatigue deformation were analyzed with the transmission electron microscope(TEM)and scanning electron microscope(SEM). The results show that at room temperature, the alloy exhibits the characteristics of cyclic hardening followed by the cyclic softening, while the alloy exhibits the characteristics of cyclic hardening followed by either cyclic softening or cyclic stability at 760 ℃. The relationship between both plastic and elastic strain amplitudes as well as reversals to failure at different temperatures for the alloy shows a single slope linear behavior, which can be described by the Coffin-Manson and Basquin equations, respectively. At both room temperature and 760 ℃, the low-cycle fatigue deformation mechanism for the alloy is mainly the planar slip. In addition, the fatigue cracks initiate and propagate in the transgranular mode.