Microstructure and mechanical/conductivity properties of pure copper joint welded by friction stir welding

Copper plates with 3 mm thickness were friction stir welded at a rotation rate of 800 r/min and different welding velocity. The effects of microstructure and the mechanical/conductivity properties of the FSW joints were studied. The results indicate that the grain sizes of nugget zones are 2.49, 2.13 and 5.07 μm for welding speed of 100, 150 and 200 mm/min, respectively. Furthermore, lower density of dislocation was obtained in the nugget zone. Under the welding speed of 200 mm/min, annealing twins had been observed. When the speed is 150 mm/min, the tensile strength of the stir welded joint is 264 MPa that can reach 98% of the base metal. The mechanical properties of the joints with the welding speed of both 100 mm/min and 200 mm/min are lower than the base metal. The corrosion resistance of weld is higher than that of base metal. Electrical resistivity measurement shows no obvious change in the welded joints compared to the base metal at the room temperature.