Investigation of Annealing Heat Treatment Effect on the Microstructure and Mechanical Properties of Friction Stir Welded C70600 Copper Nickel Alloy Joints

Friction stir welding (FSW) is a solid state welding process for joining aluminum, magnesium, zinc, copper alloys, etc. In this paper, effect of annealing heat treatment on the microstructure and mechanical properties of friction stir welded C70600 copper nickel alloy joints was investigated. Six different samples were welded in various annealing conditions and the tool rotation speeds. Microstructural properties were investigated by means of optical microscopy. Hardness value and tensile strengths of the specimens were investigated by Vickers hardness and standard tensile tests. Results show that by increasing the annealing time and decreasing rotation speed, the grain size in the NZ decreased significantly, hardness rose and tensile strength improved. The hardness behavior of friction stir welded joints was discussed by grain size variation and dislocation density. Investigations show that annealing heat treatment had significant influence on the hardness and tensile strength of FS welded C70600 copper nickel joints.