Process Optimization And Fatigue Properties Of UIT Of 7A52 Aluminum Alloy Welded Joints

7A52 is a high-strength aluminum alloy independently developed by China,but the fatigue fracture caused by poor fatigue property is still one of the main failure modes of its welded components in engineering practice,which brings huge economic loss and human resource waste.In response to such problems,the UIT of the welded joints of TANDEM MIG and MIG-VPPA were carried out at different time,and base on the changes of surface topography,roughness,plastic deformation layer thickness,microhardness and residual stress to select the time parameters of under-,over-and proper-treatment,fatigue tests are carried out to determine the influence of UIT time parameters on fatigue strength,and the fitting relationship of ultrasonic impact time,grain size and fatigue strength is established It provides theoretical basis and data support for the practical application of 7A52 aluminum alloy welded jointsThis article takes the 7A52 aluminum alloy welded joints of TANDEM MIG and MIG-VPPA UIT time per unit area of 2.5mim,5min,10min,15min,30min and 75min as the research objects.Through the observation of surface topography,microstructure and mechanical properties test,the time parameters of under-,over-and proper-treatment are selected,and the effect of them on fatigue strength are analyzedThe test results show that the under-,over-and proper-treatment time parameters of the TANDEM MIG welded joint are 2.5min,30min and 15min.Under the condition of R=0.1,N=2×106 the fatigue strength is 29.56MPa,27.78MPa and 37.86MPa,compared with 28.61MPa of the welded specimen increased by 3.32%,-2.9%and 32.33%.The under-,over-and proper-treatment time of MIG-VPPA welded joints are 2.5min,75min and 30min,under the condition of R=0.1,the fatigue strength is 64.81MPa,65.46MPa and 87.63MPa,which is 32.80%,34.17%and 79.57%higher than the 48.80MPa of the welded specimen.The relationship equations for the fitting of the TANDEM MIG and the MIG-VPPA welded joints are:D = 29.75891+7.61998et/4.59232,??= 7215.17079D-1.58903,??= 29.56+8.3ee-(t-15)2/54.47.D= 26.53998+3.57605e-t/6.07737,??= 46668.08716D-1.95597??= 64.81+ 22.82e(t-30)2/481.78.