低碳钢和奥氏体不锈钢在低周冲击疲劳过程中亚结构的变化

Substructre Variation of Low Carbon Steel and Austenitic Stainless Steel in Low Cycle Impact Fatigue

组织结构的ＴＥＭ分析表明，在指定寿命常规低周疲劳过程中，１０钢和１Ｃｒ１８Ｎｉ９Ｔｉ钢的位错密度随载荷循环周次的增加而增大，组态从线状分布经位错缠结向位错胞转化。而在同样寿命的低周冲击疲劳过程中，１０钢位错密庆变化不大，１Ｃｒ１８Ｎｉ９Ｔｉ钢出现显微变形孪晶，均不出现胞状位错组态。疲劳亚结构的上述变化部分地解释了低周疲劳过程中的应变速率效应。

The TEM analysis of substructures of low carbon steel and austenitic stainless steel shows that in ordinarylow cycle fatigue under the definite fatigue life condition of N_f=2×10￣3,the dislocation density of both the testedsteels increases with the increase in loading cycles and dislocation arrangement changes from dislocation linesthrough tangles to cells. However,in low cycle impact fatigue under the same fatigue life condition,the disloca-tion array does not change obviously in both steels and only some microtwins appear with a density not influ-enced by the loading cycles in stainless steel.The strain rate effcets in low cycle fatigue process can be partlyexplained by the variation of the substructures.