Flux-Free Diffusion Joining of SiC/6063 Al Matrix Composites Using Liquid Gallium with Nano-Copper Particles in Atmosphere Environment.

A new method for flux-free diffusion joining of aluminum matrix composites reinforced with SiC particles (SiC/Al MMCs) in atmosphere environment has been developed. Liquid gallium and nano-copper particles were employed as filler metal under joining temperatures ranging between 400 °C to 480 °C, with a holding time of 2 h and pressure of 3 MPa. The results showed that 65 vol.% SiC/6063 Al MMCs were successfully joined together. X-ray diffraction (XRD) analysis confirmed the presence of GaO at the fracture. Meanwhile, neither copper oxide nor aluminum oxide was detected. The formation of GaO can protect nano-copper particles and SiC/6063 Al MMCs from oxidation. The width of weld seam tended to be narrowed from 40 μm to 14 μm gradually with increasing temperature from 400 °C to 480 °C. The maximum shear strength level of 41.2 MPa was achieved with a bonding temperature of 450 °C. The change of the strength was due to the adequate elements' mutual diffusion and solution, as well as the change of the quantity and morphology of intermetallic compounds in the weld seam, such as AlCu and CuGa. When the diffusion joining temperature reached 440 °C or above, the leak rate of the specimen remained under 10 Pa·m/s.