To improve the low-cycle fatigue properties of Al–Zn–Mg–Cu 7075 aluminum alloy laser-welded joints, a post-weld treatment method for double-sided ultrasonic impact treatment (DSUIT) was used to treat the joints. The mechanism of different DSUITs on the microstructure and fatigue properties of welded joints was analyzed. The results showed that DSUIT reduced the welding defects and roughness of the joint surface, and the dendrite structure at the upper and lower surfaces of the joints was broken to form a plastic deformation layer (PDL) with an approximate thickness of 100 μm. Furthermore, the texture strength and grain size at the PDL were reduced. A beneficial residual compressive stress was introduced into the upper and lower surfaces of the joints after the DSUIT. When the number of cycles was 2נ10⁶, the maximum fatigue strength of the joints was 103.02 MPa after DSUIT, indicating an increase of 111.8% of the untreated joints of 48.62 MPa. Moreover, observance of the fatigue fracture of the joints revealed that the PDL produced by the DSUIT inhibited the initiation and propagation of cracks at the surface. Therefore, the DSUIT effectively improved the low-cycle fatigue properties of the joints.

为提高Al-Zn-Mg-Cu 7075铝合金激光焊接接头的低周疲劳性能，采用焊后双面超声冲击处理（DSUIT）方法对接头进行处理。分析了不同DSUITs对焊接接头组织和疲劳性能的影响机理。表明DSUIT减少焊接缺陷和接合面的粗糙度，和树枝状结构在接头处的上表面和下表面的结果被打破以形成具有100的近似厚度的塑性变形层（PDL）μ米。此外，PDL 处的织构强度和晶粒尺寸降低。DSUIT 后，在接头的上下表面引入了有益的残余压应力。当循环数为 2נ10^{如图6所示}，DSUIT后接头的最大疲劳强度为103.02 MPa，比未处理接头的48.62 MPa增加了111.8%。此外，对接头疲劳断裂的观察表明，DSUIT 产生的 PDL 抑制了表面裂纹的产生和扩展。因此，DSUIT有效地提高了接头的低周疲劳性能。