A parametric investigation on effects of friction stir welding process parameters on mechanical properties of AA6061-T6 to Cu dissimilar joints

Abstract

Joining of dissimilar materials is required in many engineering applications such as - power generation, transportation and electronics industries. Friction stir welding (FSW) is considered to be the most significant development in metal joining in last two and half decades. Friction stir welding is a solid-state welding technique involving low heat input and one of the most suitable process for joining dissimilar alloys. In friction stir welding of dissimilar metals, formation of brittle intermetallics may take place depending on peak temperature attained at the weld interface. Nature and form of these intermetallics affect dissimilar joint properties. Nature and dispersion of intermetallics can be altered by addition of suitable filler powder at weld interface. An experimental investigation has been carried out to investigate effects of FSW parameters on ultimate tensile strength (UTS) of dissimilar AA6061-T6 to pure copper joints prepared with tin filler powder. Experiments have been carried out in 11 run settings with one parameter at a time. 27% runs (3 runs) were repeated to check repeatability. Four process parameters: tool rotation speed (710, 1000 and 1400 rpm), tool travel speed (28 and 56 mm/min), tin filler powder amount by gap method (0.0, i.e., no filler, 0.05, 0.10, 0.15 mm) and tool pin axis offset at two levels (0 mm, i.e., no offset and +1.0 mm offset toward AA6061-T6 sheet) have been considered. Microstructure, microhardness testing and X-ray diffraction (XRD) analysis have been carried out. Results indicate that weld prepared with 0.05 mm tin filler powder gap resulted into optimum tensile properties which can be attributed to only Cu₃Sn intermetallic layer at the interface of the weld.