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用光滑圆柱形试样,在应变控制下测定了两种热处理状态5CrNiMo钢的低周疲劳性能.试验发现,应变幅△ε_t/2在0.6～1.8×10~(-2)范围内,两种状态试验钢均表现为循环软化特性,软化效应主要集中在前几周;试验钢的应变-寿命曲线符合Manson-Coffin关系,且高温处理有较好的低周疲劳性能.TEM分析表明,循环软化与塑性变形的不均匀性有关;软化现象是由于循环变形中位错结构转变成低密度、低内应力的位错胞状组织,以及细小碳化物受性错往复剪切不断碎化而回溶所引起的.
The low-cycle fatigue properties of two heat-treated 5CrNiMo steels were measured with a smooth cylindrical specimen under strain control. It was found that the strain rate ranged from 0.6 to 1.8 × 10 ~ (-2) The test steel shows the characteristics of cyclic softening, the softening effect mainly concentrated in the first few weeks, the strain-life curve of the test steel meets the Manson-Coffin relationship, and the high temperature treatment has good low cycle fatigue performance. TEM analysis shows that the cycle softening Which is related to the non-uniformity of plastic deformation. The softening phenomenon is due to the transformation of the dislocation structure in cyclic deformation into dislocation cells with low density and low internal stress, caused.