Refill friction stir spot welding of EN AW-7075-T6 sheets
By Koen Faes (Belgian Welding Institute), Irene Kwee (Belgian Welding Institute), Wim De Waele (Ghent University, Department of Electrical Energy, Metals, Mechanical Constructions & Systems, Laboratory Soete)

Refill friction stir spot welding is a solid-state spot welding process for joining lightweight sheets in the overlap configuration by means of frictional heat and mechanical work. In this experimental research, refill friction stir spot welds of aluminium alloy EN AW-7075-T6 sheets, used in aircraft applications for its light weight and high strength, were produced. The joining time, rotational speed and plunge depth were varied. Surface temperature measurements in the proximity of the weld provided an indication of the heat input. The microstructure and hardness of the sheet joints were investigated and related to the welding parameters and heat input. The mechanical properties, in particular the lap shear strength, cross tension strength and their corresponding failure modes were examined and related to the weld characteristics and welding parameters.