通过750℃低周疲劳试验,研究55Ni?23Cr?13Co基高温合金在应变幅度为0.35％～0.6％下的循环变形行为及显微组织演变.Coffin?Manson?Basquin和Smith?Watson?Topper模型能很好地预测该合金不同应变幅度下的疲劳寿命.在循环加载过程中,该合金表现出现循环硬化后再循环软化的特征.初始循环硬化行为是由于位错与析出物的相互作用,而循环软化行为是由位错切割 γ′ 相和位错回复引起的.显微组织分析结果表明,M23C6碳化物在较低应变幅度下呈连续链状分布,而在较高的应变幅度下呈不连续分布.由于位错对γ′ 相的重复剪切作用,随着应变幅度的增大,γ′ 相的尺寸减小.分析断裂机制,在较高的应变幅度下,孔洞容易在晶界附近形成.“,”The cyclic deformation behavior and microstructure evolution of the 55Ni?23Cr?13Co nickel-based superalloy were studied at 750 ?C under the strain amplitudes from 0.35％ to 0.6％. Coffin?Manson?Basquin and Smith?Watson?Topper relationships were employed, which satisfactorily predicted the fatigue life of the alloy under various strain amplitudes. The superalloy showed an initial cyclic hardening as a result of the interaction between the dislocations and the precipitates, and following cyclic softening behavior mainly due to the shearing of the γ′ phase by dislocations and dislocations recovery under all strain amplitudes. Microstructure analyses showed that the M23C6 carbides exhibited a continuous-chain distribution at lower strain amplitudes, while they showed a discontinuous distribution at higher strain amplitudes. As the strain amplitude increased, the size of the γ′ phase decreased as the consequence of repeated shearing by dislocations. Fracture mechanisms were analyzed. Under higher strain amplitudes, cavities preferred to form around grain boundaries.