Friction Stir Welding (FSW) of Aged CuCrZr Alloy Plates

Friction Stir Welding (FSW) of Cu-0.80Cr-0.10Zr (in wt pct) alloy under aged condition was performed to study the effects of process parameters on microstructure and properties of the joint. FSW was performed over a wide range of process parameters, like tool-rotation speed (from 800 to 1200 rpm) and tool-travel speed (from 40 to 100 mm/min), and the resulting thermal cycles were recorded on both sides (advancing and retreating) of the joint. The joints were characterized for their microstructure and tensile properties. The welding process resulted in a sound and defect-free weld joint, over the entire range of the process parameters used in this study. Microstructure of the stir zone showed fine and equiaxed grains, the scale of which varied with FSW process parameters. Grain size in the stir zone showed direct correlation with tool rotation and inverse correlation with tool-travel speed. Tensile strength of the weld joints was ranging from 225 to 260 MPa, which is substantially lower than that of the parent metal under aged condition (~ 400 MPa), but superior to that of the parent material under annealed condition (~ 220 MPa). Lower strength of the FSW joint than that of the parent material under aged condition can be attributed to dissolution of the precipitates in the stir zone and TMAZ. These results are presented and discussed in this paper.