Friction stir welding of Al-Zn-Mg alloy AA7039

Abstract

In this investigation Al-Zn-Mg alloy AA7039 was friction stir welded (FSW) successfully employing a rotary speed of 635 rpm and welding speed of 75 mm/min, in order to elucidate the effect of FSW on mechanical and corrosion properties. The yield and ultimate tensile strength of the joint were found lower than the base material while ductility of FSW joint was found higher than the base material. The joint efficiency of friction stir welded joint was 85.59 %. The microstructure and other unique features associated with different zones of FSW joints were studied by optical and scanning electron microscopy. SEM study of fracture surfaces revealed that fracture is triggered by the breaking of secondary precipitates (MgZn2). Weld nugget of FSW joint was found to be susceptible to corrosion than HAZ and base metal. The current density for WNZ and HAZ were ~8.5 and 2.8 times higher than that of the base metal.