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对淬火高温回火的未服役新叶片材料及已服役近７万ｈ的旧叶片材料２Ｃｒ１３钢进行了低周、高周疲劳试验。用透射及扫描电镜对其微观结构的演变进行了观察。新２Ｃｒ１３钢经低周疲劳软化后，位错发生了较大范围的动态回复，形成了具有较低能量的亚晶界结构，位错运动的平均自由程增大是其软化的原因。服役后旧叶片本身已发生了软化，微观应力测定结果表明旧叶片的微观应力较小，而且低温冲击断口的ＳＥＭ观察发现旧叶片中已形成了微空洞。服役叶片的低周疲劳实验也表现出循环“软化”，但位错亚结构的变化却表现了循环硬化的特征，这说明服役叶片的循环软化是由于旧叶片内已形成的微空洞损伤造成的。
Low-cycle and high-cycle fatigue tests were carried out on un-serviced new blade materials tempered at high temperature and quenched and on aged 2Cr13 steel, which has been used for nearly 70,000 h. The microstructure evolution was observed by transmission and scanning electron microscopy. After the low cycle fatigue softening of the new 2Cr13 steel, a large range of dynamic responses occurred to the dislocations, forming a subgrain boundary structure with lower energy. The increase of the mean free path of dislocation movement is the reason of its softening. After service, the old blade itself has been softened. The results of micro-stress measurement show that the micro-stress of the old blade is small, and the SEM observation of the low-temperature impact fracture shows that micro-cavities have formed in the old blade. Low-cycle fatigue tests of service blades also showed cyclic “softening”, but the change of dislocation sub-structure showed the characteristics of cyclic hardening, which indicated that the cyclic softening of service blades was caused by the micro-cavity damage that had formed in the old blades .