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通过研究不同回火温度的马氏体在疲劳前后的组织变化,发现在疲劳过程发生了碳化物的析出或聚集现象;以及相应的位错结构的回复。其变化方向与回火过程一致。提出变化的本质就是疲劳载荷协助的再回火效应。用这一观点统一解释了不同回火温度下马氏体的疲劳软化机制,以及400℃回火可获得最大软化量的原因。此外,根据对400℃回火马氏体疲劳前后碳化物特征参数的测定,表明微细碳化物的聚集是该温度回火态试样疲劳软化的主要机制。
By studying the microstructure changes of martensite with different tempering temperatures before and after fatigue, it was found that carbide precipitation or aggregation occurred during the fatigue process and the corresponding dislocation structure was recovered. The direction of change is consistent with the tempering process. The essence of the proposed change is the re-tempering effect assisted by fatigue loads. From this point of view, the mechanism of fatigue softening of martensite at different tempering temperatures and the reason of the maximum softening amount at 400 ℃ are obtained. In addition, according to the determination of characteristic parameters of carbides before and after tempering martensite at 400 ℃, it shows that the aggregation of fine carbides is the main mechanism of fatigue softening of tempered samples.