Mechanical properties of 2024-T3 AlClad aluminum FSW lap joints and impact of surface preparation

Abstract

The effect of removing oxides prior to friction stir welding (FSW) by brushing the mating surfaces of 2024-T3 AlClad plates in lap joint assemblies was studied. Two types of surface preparation were selected: light brushing with a stainless steel brush (“brushed”) and simple cleaning with acetone (“as-clad”).Macroscopic discontinuities and geometrical features of friction-stir-welded joints, known to affect their mechanical behavior, were observed and were found to be similar for both types of preparation. Tensile tests were conducted on brushed and as-clad welds. The results showed no significant difference between the samples, with all specimens failing in shear through the nugget zone. Fatigue tests at different stress amplitudes showed similar crack paths for the brushed and the as-clad specimens, with failure occurring through the top plate of the lap joint, in mode I.Light brushing of Al2024-T3 AlClad plates, intended to remove the passive oxide scale on the mating surfaces, did not have a significant influence on the microstructural characteristics and the macrostructural features of the weld, or on the cladding fragments distribution in the joint. The removal of surface oxides prior to welding did not affect either tensile or fatigue strength in the range of the tested conditions because the AlClad in the welded zone dictated the failure location during tensile testing, while the fatigue failure mode was controlled by the kissing bond geometry.