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用透射电子显微镜和扫描电子显微镜研究了一种镍基合金(Nimonic 75型)蠕变-疲劳交互作用的机制。在温度873K,应力幅392MPa下进行的实验表明,蠕变、疲劳和“蠕变叠加疲劳”数据近似满足线性积累损伤规律。扫描电子显微镜断口观察表明,所有试样均发生晶间型断裂。但用透射电子显微镜进行的位错观察指出,在蠕变、疲劳和“蠕变叠加疲劳”试样中,位错组态有明显的差别。这些不同的位错组态,对晶间断裂过程产生了各自不同的影响,因而蠕变损伤与疲劳损伤相互独立,在宏观上表现出线性交互作用的规律。本工作表明,透射电子显微学对于揭示蠕变-疲劳交互作用的机制有很大的潜力。
The mechanism of creep-fatigue interaction of a Ni-based alloy (Nimonic 75 type) was investigated by transmission electron microscopy and scanning electron microscopy. Experiments carried out at a temperature of 873K and a stress of 392MPa show that the creep, fatigue and creep superposition fatigue data satisfy the law of linearly accumulated damage. Scanning electron microscopy fracture observations showed that all samples were intergranular fracture. However, dislocation observation using a transmission electron microscope indicates that there is a clear difference in dislocation configurations in creep, fatigue and “creep stack fatigue” specimens. These different dislocation configurations have different effects on the intergranular fracture process. Therefore, the creep damage and fatigue damage are independent of each other, exhibiting the law of linear interaction macroscopically. This work shows that transmission electron microscopy has great potential for revealing the mechanism of creep-fatigue interaction.