表面层亚结构和残余应力对不锈钢和低碳钢疲劳强度的影响

EFFECT OF SUBSTRUCTURE AND RESIDUAL STRESS IN STRENGTHENED LAYER ON FATIGUE STRENGTH OF STAINLESS STEEL OR LOW CARBON STEEL

透射电镜分析结果表明,不锈钢表面强化层内存在大量显微变形孪晶。变形孪晶不仅起到了组织强化的作用,而且还可防止表面残余应力在疲劳过程中逐渐衰减,使不锈钢弯曲疲劳强度维待在较高的水平。低碳钢表面强化层中的胞状位错组态在疲劳过程中稳定性较差,不能阻止表面残余应力的松弛,因此表面机械强化不能提高低碳钢的弯曲疲劳强度。

In the strengthened surface layer of stainless steel after shot peening,there are a great amount of deformation microtwins, which may act as structuralstrengthening and prevent the gradual relexation of surface residual stress duringfatigue, so as to keep its rather high level of bending fatigue strength. However,in the strengthened surface layer of low carbon steel, dislocation cell structure isso unstable during fatigue that its surface residual stress relexation cannot be retard-ed. Therefore, the bending fatigue strength of the low carbon steel does not beimproved by shot peening.