Abstract
To improve the weldability of 6061 aluminum alloy and improve the mechanical properties of welded joints, ultrasonic was introduced into the welding process. The microstructure changes of welded joints under different ultrasonic power were studied, and their effects on the mechanical properties of welded joints were analyzed. The grain size was calculated, and the distribution of precipitated phases was observed by the EBSD technique. The results show that the cavitation and acoustic flow produced by ultrasonic vibration can refine the microstructure of welded joint, reduce the grain size by nearly 50%. It promotes the transition of alloy elements to weld and eliminates the segregation of the strengthening phase to the grain boundary, thus improving the mechanical properties of the welded joint.
Highlights
Vibration on Grain Size andHard aluminum alloy is an ideal lightweight structural material due to its high strength, hardness, and low density
It was found that the center microstructure of the heat-treated aluminum alloy weld zone was mainly equiaxed grain, and the second phase was precipitated at the grain boundary
6061-T6 aluminum alloy was selected as the base material, the main component was alloy is α (Al)-Mg-Si, the plate size was 125 mm × 125 mm × 5 mm, the mechanical properties were shown in the Table 1
Summary
Hard aluminum alloy is an ideal lightweight structural material due to its high strength, hardness, and low density. It is widely used in aerospace, automobile manufacturing, and rail transit. There is recrystallization in the fusion zone of the weld and over-aging softening in the heat-affected zone, and the strength coefficient of the welded joint is significantly reduced [1]. It was found that the center microstructure of the heat-treated aluminum alloy weld zone was mainly equiaxed grain, and the second phase was precipitated at the grain boundary. There was a segregation phenomenon of uneven chemical composition in the weld metal, the heat-affected zone of the joint was obvious softened, and the microstructure near the weld zone was recrystallized [2]. The joint strength usually does not exceed 60% of the base metal strength
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