Effect of arc-ultrasound on microstructures and mechanical properties of plasma arc welded joints of SiCp/Al MMCs

The effect of arc-ultrasound on microstructures and mechanical properties of SiCp/6061Al MMCs joints produced by arc-ultrasound plasma arc “in-situ” alloy-welding with different excitation frequencies was investigated, in which argon-nitrogen mixture was used as plasma gas, Ti wire as filler and the arc-ultrasound was produced by modulating the plasma arc with high frequency. The results show that arc-ultrasound could refine the new reinforced composites such as TiC, TiN significantly, and improve their distribution greatly. And new phase Al3Ti becomes finer and less. The test results of mechanical properties indicate that the maximum tensile strength of welded joints is gained when the excitation frequency is 50 kHz, and the maximum is 225 MPa, raising by about 7% compared with conventional plasma arc welding (PAW) (203 MPa).