超声冲击对搅拌摩擦焊缝疲劳性能的影响

Effect of ultrasonic impact on fatigue performance of friction stir weld

采用超声冲击对铝合金2024-T4搅拌摩擦焊焊缝进行处理,对冲击前后试样进行残余应力、微观组织、显微硬度和疲劳性能的对比分析。结果表明:超声冲击处理之后,试样的表面引入残余压应力,平均残余压应力可达263 MPa;试样经过超声冲击处理表层组织得到细化,变形层深度可达50~70μm,表面硬度由175 HV提升到235 HV;超声冲击处理的试样疲劳寿命明显提高,超声冲击试样是未冲击试样疲劳寿命的1.72~2倍,疲劳裂纹萌生的位置由表面转移至强化层以下的亚表面。

Ultrasonic impact is used to process the welding seam of aluminum alloy 2024-T4 friction stir welding. The residual stress,microstructure,microhardness and fatigue performance of the specimens before and after ultrasonic impact were compared and analyzed. The results show,after ultrasonic impact treatment,residual compressive stress is introduced into the surface of the specimen,and the average residual compressive stress can reach 263 MPa. The surface structure of the sample is refined after ultrasonic impact treatment,the depth of the deformation layer can reach 50~70 μm,and the surface hardness is increased from 175 HV to 235 HV. The fatigue life of the specimens treated by ultrasonic impact are significantly improved. The fatigue life of the ultrasonic impact specimens are 1.72~2 times that of the unimpacted specimens,and the location of fatigue crack initiation is transferred from the surface to the subsurface below the strengthening layer.