Influence of ultrasonic peening on microstructure and surface performance of laser-arc hybrid welded 5A06 aluminum alloy joint

Abstract In this study, laser-arc hybrid welding of 5A06 aluminum alloys was performed firstly. To improve the surface quality of welded joints, ultrasonic peening (UP) process was employed. The influence of different peening needle velocities on surface microstructure and properties was investigated. The results indicated that UP produced protrusions and grooves on treated surface of welded joints. EBSD analysis showed that grains in UP-treated surface layers was refined from 100 to 50 μm. Improved dislocation structure was observed via TEM analysis. Increasement in full width at half maximum (FMHW) and Bragg angle of diffraction peaks in XRD analysis further demonstrated the formation of fine grains. The surface microhardness increased by 38.9% from 92.6 to 132 HV due to the work hardening effects. In addition, UP-treated welded joints possessed better wear resistance. After UP process, a 50% decrease in wear rate was obtained. The wear mechanism changed from adhesive to abrasive wear for the UP-treated joints. Besides, the possibility of corrosion initiation and the corrosion rate of UP-treated joints were lower than those of non-treated joints implying better corrosion resistance.