Microstructure and mechanical characterization of a friction-stir-welded C18150 butt joint

In this study, the Cu-Cr-Zr alloy was welded by means of friction stir welding. Particularly, the microstructure of joints was observed by Metalloscope, SEM and Electron backscatter diffraction (EBSD). The mechanical properties were investigated by tension test and micro-hardness test. The result shows that the final grain structure in the nugget zone is composed of grains in state of dynamic recrystallization and partial dynamic recovery. The dynamic recrystallization process is a continuous dynamic recrystallization process. Coarse particles which are 5~10 μm in length are found innugget zone of Cu-Cr-Zr. The EDS analysis further reveals that these coarse particles are mainly composed of Cr element. All these precipitates are dissolved due to the high temperature in the nugget zone of Cu-Cr-Zr. The micro-hardness and tensile strength of nugget zone decreased due to the dissolution of precipitates.