Microstructural Characteristics and Mechanical Properties of Friction-Stir-Welded CuSn6 Tin Bronze

Tin bronze is widely applied in various industries for its excellent wear and corrosion resistance. Friction stir welding is a solid-state welding process, which generates less heat and avoids the melting-related defects. CuSn6 tin bronze plates of 4 mm in thickness were friction-stir-welded at welding speeds ranging from 50 to 150 mm/min under a constant rotation speed. The microstructural and mechanical properties of joints were investigated. The microstructure of the stir zone consists of refined equiaxed grains. The grain size decreased from top to bottom of the welds. The mean grain size is increased with increasing welding speed. The largest strength and elongation of welded joints were both obtained at the welding speed of 100 mm/min. During tensile test, all of the joints were fractured at the heat affected zone of retreating side with typical plastic fracture feature, since the grains were coarsened by welding heat.