Mechanical, electrochemical and structural characteristics of friction stir spot welds of aluminium alloy 6063

Abstract

The work presents the friction stir spot welding (FSSW) of AA6063. The evolving properties due to the influence of process parameters and the efficacy of metallurgical, structural, mechanical, and electrochemical integrities were studied. FSSW was conducted on 2mm thickness by varying the rotational speed of 600, 900 and 1200 rpm and the dwell time at 10 and 15 s. The evolving microstructures, hardness, corrosion, shear tensile behaviours and X-ray diffraction characteristics of the as-received material and the welds were studied. As the tool rotational speed increased at a constant dwell time, a smooth and debris free spot welds were noticed, more HAZ formations became visible and more intermetallic phases of aluminium magnesium (AlMg) were formed although with very low peaks during structural assessment. Furthermore, the hardness values increased up to a certain limit and then decreased, the corrosion properties in artificial seawater (ASW) shown significant improvement on the spot-welded samples and the tensile shear strength was also improved. It would be recommended that spot welds at 900 rpm and 10 and/or 15 s for applications where the hardness is significant imperative and at 1200 rpm with 10 and/or 15 s dwell time where higher tensile shear strength is required and lastly, 1200 rpm at 15 s where corrosion application is significant.