Joining metrics enhancement when combining FSW and ball-burnishing in a 2050 aluminium alloy

Abstract

This report describes the effect of the ball-burnishing process on the mechanical properties of 2050 aluminium alloy that was previously friction stir welded. This process is a fast, environmentally-friendly and cost-effective surface treatment based on the plastic deformation of the surface irregularities. Consequently, residual stress, material hardening and micro-structural alterations are investigated to improve fatigue strength and wear resistance. The results show that the ball-burnishing treatment enhances the surface properties by increasing the material hardness about 37.5% and by decreasing the average surface roughness from 2.23¿µm to 0.06¿µm when a high pressure and a perpendicular burnishing is deployed. Additionally, in-depth compressive residual stresses are generated from -315¿MPa to -700¿MPa depending on the burnishing configuration. Finally, a numerical simulation of the material elastoplastic response is performed to analyze the residual stress continuity in the cross sectional area when using two radial feeds and burnishing pressures. In short, the present study helps to reduce time consumption by selecting the larger radial feed combined with a proper burnishing pressure to ensure the desired quality and compressive residual stress at the surface, which are indices of enhancing the fatigue strength at the nugget zone of the welded area.