Nanoparticle-Enabled Reduction of Residual Stress in Arc Welding of Aluminum Alloys

Welding of aluminum alloys is widespread in aviation, aerospace, shipbuilding, and consumer products. However, residual stress in welds causes premature failure or distortion of welded structures, resulting in significant time and monetary costs. Hence, reduction of residual stress in arc welding of metals has remained a longstanding challenge. This paper studies and applies emerging nano-treating technology to achieve a significant reduction of residual stress and distortion in sheet welds of AA2024, AA6061, and AA7075. Macroscopic angular distortion, outward thermal flux from the weld metal, in-situ strain, and microstructure are evaluated to understand the effect of nano-treating on residual stress development. Macroscopic distortion angle is reduced by up to 50% when using nano-treated filler materials. Next, as shown by one-dimensional thermal flux calculations, the inclusion of nanoparticles slows the release of heat out of the weld during solidification. Finally, residual axial strain along the direction of the weld is reduced when using nano-treated filler. The stressed region adjacent to the weld was also shortened by approximately 1-2 mm. A nanotechnology-enabled mechanism based on experimental results and established nano-treating effects is elucidated to suggest nanoparticle-enabled control of residual stress by reducing constraints on solidification-induced shrinkage.