Ultrasound enhanced friction stir welding of aluminum and steel: process and properties of EN AW 6061/DC04-Joints
M. Thomä, G. Wagner, B. Straß, B. Wolter, S. Benfer, W. Fürbeth
Journal of Materials Science & Technology 34 (2018) 163-172; DOI: 10.1016/j.jmst.2017.10.022
In this work, the joining of aluminum to steel was conducted by ultrasound enhanced friction stir welding (USE-FSW). The power ultrasound was introduced into one of the metal sheets by an ultrasonic roll seam module synchronously to the FSW-process. The effect of the ultrasound on the resulting welds, their microstructure and their corrosion properties was investigated by light and scanning electron microscopy and corrosion investigations. The USE-FSW-joints showed less and smaller steel particles in the nugget zone as well as a thinner continuous intermetallic phase of FeAl3 at the interface. The nondestructive testing method of computed laminography proved the observations made by optic microscopy due to non-porous joints for both techniques. Corrosion investigations showed only low corrosion current densities and no enhanced galvanic corrosion for the EN AW-6061/DC04-hybrid joints in sodium chloride solution.