搅拌摩擦焊2124-T851铝合金超低周疲劳特性

摘要

为获得搅拌摩擦焊接(FSW)条件下单次加载断裂与循环加载断裂机制的演化规律,研究了FSW及标准基材2124-T851铝合金超低周疲劳(ELCF)特性.分析表明,FSW试样S-N曲线在超低周疲劳寿命区符合幂函数关系但数据分散性大,且当指定寿命越大时,焊接试样相对于基材的定寿强度(SSFL)下降率越高.在极限寿命定义为1个循环的假设下,单次加载断裂与多次加载断裂具有统一的宏观变化规律,其微观断裂机制也具有连续演化的特征.超低周疲劳断口无明显的疲劳源区,FSW试样随着超低周疲劳寿命的增大,断裂特征由正断型向切断型转变.%In order to get the mechanism of single loading fracture and cyclic loading fracture of the bond fabricated by friction stir welding(FSW),the extremely low cycle fatigue (ELCF) features of the FSW specimen and standard matrix material 2124-T851 aluminum alloy have been studied.The results show that,in the extremely low cycle fatigue life zone,the S-N Curve of FSW specimen is corresponding with power function relationship but there is a large dispersion of data,and with the longer of the specified fatigue life,the FSW specimen has a higher decrease in strength of specified fatigue life (SSFL).Supposing that the limit of fatigue life is defined as 1 cycle,single loading fracture and cyclic loading fracture have a unified macro variable rule and the micro fracture mechanism also has the characteristics of continuous evolution.Obvious fatigue source region can not be observed on extremely low cycle fatigue fracture surface.With the increasing of extremely low cycle fatigue life,the type of FSW fracture characteristics turns the normal mode into shear mode.