Effect of tool rotational speed and position on mechanical and microstructural properties of friction stir welded dissimilar alloys AZ31B Mg and Al6061

Abstract

The existence of some problems in joining Al and Mg alloys using classical fusion welding methods causes limitations in the use of Mg and Al alloys in common structures. Friction stir welding (FSW) is a solid-state welding method for joining materials having same or different properties at temperatures below their melting points. In this study, dissimilar alloys AZ31B Mg and Al6061 were joined by FSW at a feed rate of 34 mm center dot min(-1) and at different tool rotational speeds (600 and 700 rpm) and material positions. During the welding process, AZ31B Mg plate was positioned at the advancing side and Al6061 was located at the retreating side, and moreover, the two alloys were also positioned vice versa. Tensile strength and microhardness tests were performed to examine the mechanical properties of the welded specimens. The microstructures of the welded zones were examined by obtaining the optical microscopic (OM) and scanning electron microscopic (SEM) images. The highest welding strength was obtained from the specimen welded at a tool rotational speed of 600 rpm, at a feed rate of 34 mm center dot min(-1) and by locating AZ31B Mg on the advancing side.