Analysis and volta potential measurement of second phases in friction stir welding seam of 7A52 aluminum alloy

The species, size and volta potential of intermetallics of friction stir welding seam of 7A52 aluminum alloy have important influence on its corrosion behavior. The interemtallics of the welded seam were observed and characterized with metallographic microscope, scanning electron microscope, energy dispersive spectrometer and scanning Kelvin probe force microscope, and the volta potential of the welded seam was tested. The results indicate that the irregularly shaped intermetalics AlFeMnSi and Mg₂Si disperse in the welded seam, which sizes are several microns and volta potentials are lower than the matrix. The volta potential of Mg₂Si is lower than that of AlFeMnSi intermetalics, which means that Mg₂Si is easier to be corroded in erosive environments. The results lay the foundation of studying corrosion behavior of friction stir welding seam of 7A52 aluminum alloy.