Microstructure and Mechanical Property of 5000 Series Aluminum Stud Joint with Zinc Insert Using Friction Welding

Abstract

Friction stud welding with zinc insert was applied to 5000 series aluminum alloys. A cone-shaped A5056 stud bolt was successfully friction-welded onto A5083 plate at low torque using zinc insert compared to that without zinc insert. This is considered to be contributed by a eutectic reaction between aluminum and zinc, which can effectively remove the oxide film and promote the joining. With bigger torque and longer welding time, the amount of residual zinc was reduced and high strength was achieved. On the other hand, a twist break between the stirred zone and the stud bolt increased during friction and this causes the decrease of tensile strength of the joint after a certain amount of torque. The results of micro-tensile test showed that strength at the edge of joint interface was higher than that at the center area regardless of zinc insert. From the experimental results, the joining process of the present friction stud welding classified into five processes, i.e. wear of stud bolt, start of joining, increase of tensile strength, decrease of tensile strength, and fracture during friction.