Refill friction stir spot welding of aerospace alloys in the presence of interfacial sealant

Refill friction stir spot welding (refill FSSW) is one of the most industrially promising friction stir spot welding variants. The absence of an exit hole improves the effectiveness of surface treatments and minimizes damage by fouling. Aerospace aluminium alloys AA2024-T3 and AA7075-T6 with a thickness of 2 mm were used in this investigation. A range of values for rotation speed and plunge depth were experimented to determine the most promising process parameter combination based on the crosssectional analysis and lap shear strength. The effect of an interfacial sealant on the weld properties was determined for both alloys using the most promising process parameter combination. Fatigue life analysis and fractography using scanning electron microscopy were performed for specimens with and without sealant.