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31答: a.韧性过载断面呈微坑花样(韧窝)。 b.疲劳扩展第一阶段,大多数合金为平断口,没有滑移解理及其他特征,高温镍基合金可以看到类似解理断裂,河流台阶花样,疲劳纹,舌头花样,少数合金呈锯齿状断口,可以看到平行片层,其位向在晶界处发生变化,有时可看到擦伤痕迹及疲劳纹。疲劳裂纹扩展第二阶段断口最重要的特点是疲劳纹。
31 A: a. Tenacity overload section was pit-like pattern (dimple). b. Fatigue extension In the first stage of fatigue expansion, most of the alloys are flat and without slip cleavage and other features. High-temperature nickel-base alloys show similar cleavage fractures, river step patterns, fatigue patterns, tongue patterns, Fracture-like, you can see the parallel sheet, the bit changes to the grain boundary, and sometimes can see traces of scratches and fatigue patterns. Fatigue crack growth The second phase of the fracture is the most important feature of fatigue patterns.