Refill Friction Stir Spot Welding (RFSSW) of Aerospace Aluminium Alloys
By Anthony Mcandrew (TWI Ltd)

Refill friction stir spot welding (RFSSW) is a solid-state joining process, which is finding increasing industrial interest for spot welding aluminium alloys for aerospace applications. RFSSW is a technology with the potential to replace mass-adding mechanical fastening processes, such as riveting stringers and stiffeners to aircraft skins. Despite the interest, there is not yet a full understanding of the effects of this spot-welding process on the mechanical properties of aerospace aluminium alloys. To address this problem, refill friction stir spot welds were made in a range of aluminium alloys (AA7050-T7451 and AA2024-T3) and analysed for fatigue, lap-shear, cross-tension and corrosion performance. The results show that RFSSW has the potential to replace rivets for aerospace applications, owing to the excellent mechanical performance of the welds and repeatability of the process. These findings have significant, practical benefits and may aid industrialisation of RFSSW.