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采用超声喷丸技术(USSP)处理TC4试样,再进行四点弯曲疲劳加载。采用X射线应力仪测试疲劳加载前后残余应力分布;利用TEM设备,对疲劳加载前后TC4组织结构进行表征。结果表明,经表面纳米化处理后,TC4合金的最大残余应力已超过自身的屈服强度;当外加载荷高于疲劳极限时,残余应力场明显减弱;当外加载荷接近或小于疲劳极限时,循环周次与载荷的增减不再明显改变残余应力场;位错及位错胞在疲劳过程中发生了组态和数量的变化,位错密度的降低导致了残余压应力的松弛。
The TC4 sample was processed by ultrasonic peening (USSP) and then subjected to four-point bending fatigue loading. The residual stress distribution before and after fatigue loading was measured by X-ray stress meter. The structure of TC4 before and after fatigue loading was characterized by TEM equipment. The results show that the maximum residual stress of TC4 alloy exceeds its own yield strength after surface nanocrystallization treatment. When the applied load is higher than the fatigue limit, the residual stress field obviously decreases. When the applied load is close to or less than the fatigue limit, Changes of secondary stress and load did not change the residual stress field obviously. Dislocation and dislocation cells changed their configuration and quantity during the fatigue process. The decrease of dislocation density led to the relaxation of residual compressive stress.