【摘要】 对50钢进行了正火+高温回火、中温回火、高温回火三种不同热处理状态的对称拉压超声疲劳试验,同时用扫描电子显微分析技术和X射线能谱分析方法对50钢的疲劳断口形貌进行显微分析,研究其疲劳断裂行为和疲劳断裂机理。结果表明,50钢存在表面和内部两种裂纹萌生机制;在本试验范围内,热处理工艺对50钢超高周疲劳性能的影响较低周和高周为小,随着寿命的增加,影响越来越弱;热处理工艺对50钢不同的疲劳阶段有不同的影响起源于不同的裂纹萌生机制,对常规疲劳性能起改善作用的热处理工艺可能对材料超高周疲劳性能的改善没有太大作用。更多还原

【Abstract】 The ultrasoic fatigue tests were carried out to study the influence of heat treatment on fatigue strength of 50 steel in the very high cycle regime.The fatigue fracture surface of 50 steel was analyzed by scanning electron microscopy and energy dispersive X-ray.The results show that both surface and subsurface fatique crack initiation are observed.Heat treatments have a little influence in UHCF regime compared with LCF and HCF.The reason that heat treatments have different effects in different fatigue regime results from different crack initiation mechanism.Therefore the heat treatment that can improve conventional fatigue behavior probably has no effect on UHCF fatigue behavior.更多还原