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

Abstract

This report describes the effect of the ball-burnishing process on the mechanical properties of 2050 aluminiumalloy that was previously friction stir welded. This process is a fast, environmentally-friendly and cost-effectivesurface 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 thematerial hardness about 37.5% and by decreasing the average surface roughness from 2.23 μm to 0.06 μm whena high pressure and a perpendicular burnishing is deployed. Additionally, in-depth compressive residual stressesare generated from −315 MPa to −700 MPa depending on the burnishing configuration. Finally, a numericalsimulation of the material elastoplastic response is performed to analyze the residual stress continuity in thecross sectional area when using two radial feeds and burnishing pressures. In short, the present study helps toreduce time consumption by selecting the larger radial feed combined with a proper burnishing pressure toensure the desired quality and compressive residual stress at the surface, which are indices of enhancing thefatigue strength at the nugget zone of the welded area.