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本文测定了20SiMnV钢经疲劳后的正电子寿命谱和宏观残余力,观察了疲劳断口、表面滑移带和沿试样层深位错结构的变化。结果表明:随着循环周次的增加,正电子湮没寿命和强度呈周期性变化,宏观残余应力时增时减。正电子湮没参数的周期性,与点阵畸变和晶体缺陷的周期性变化有关。滑移过程的不断进行,使试样表面残余应力的积蓄和释放交迭进行,故宏观残余应力时增时减。随着层深的增加,位错密度减少,与塑性形变沿层深减少相对应。
In this paper, positron lifetime spectrum and macroscopic residual force of 20SiMnV steel after fatigue were measured, and the changes of deep dislocation structure along the fatigue fracture, surface slip band and along the sample layer were observed. The results show that the lifetime and intensity of positron annihilation periodically change with the increase of the number of cycles, and the number of macroscopic residual stress increases and decreases with time. The periodicity of positron annihilation parameters is related to the periodic changes of lattice distortion and crystal defects. The continuous sliding process makes the accumulation and release of residual stress on the sample surface overlap, so the macro residual stress increases and decreases. With the increase of the layer depth, the dislocation density decreases, which corresponds to the decrease of the depth of plastic deformation along the layer.