Joining of high strength aluminum alloys by refill friction stir spot welding (III-1854-18)

Starting with a brief presentation of the boundary conditions and the refill friction stir spot welding of high strength aluminum alloys, this paper introduces the quality criteria of refill friction stir spot welded joints. Afterwards, the paper discusses the influences of the process parameters on the joint formation and load-bearing capacities. Due to possible industrial application fields in automotive and airplane production, in which the combination with sealer or adhesives gets increasingly important, hybrid joining (combination of spot-shaped refill friction stir spot welds and sealer or adhesives) will also be discussed. Due to increased tool wear and contamination, different strategies for driving the polymer out of the joint area will be shown and compared. As the assurance of the joint quality with the help of nondestructive testing (NDT) plays an important role, an ultrasonic-based testing procedure will be shown. Additionally, a repair concept by “over-welding” will be investigated by destructive and nondestructive (ultrasonic testing procedure) testing for selected failure modes. The paper closes with specific recommendations for the realization of elementary and hybrid refill friction stir spot welded joints which meet the quality demands, and an outlook for further research steps will be given.