AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn–Zn–Al filler metal.The microstructure,fracture morphologies,and mechanical properties of joint were investigated.The results show that Mg–Al intermetallic compounds can be avoided by the process.But,a small quantity of porosity is found in the joint.The shearing strength of joint interface adjacent to magnesium alloy is35.4 MPa for formation of Mg–Sn intermetallic compounds,which is about 46%of that of filler metal.While,the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn–Sn–Al solid solution,which is about 92%of that of filler metal.
Stirring assisted brazing of SiC(p/A356) composites in air was investigated. A stirring was applied on one of the samples to be bonded at 455℃ during brazing. The filler metal was extruded and impacted intensively on the two surfaces of the base materials during stirring. It can be found that oxide film on the surface of the composites can be disrupted and removed through the observation by scanning electron microscopy (SEM). The metallurgical bonds formed between the filler metal and the base materials. However, continuous residual oxide film was found at bottom joint interface, which limited the lift of joint strength. A stirring was applied once more after the samples were continuously heated up to 470 and 500℃, respectively. At this time, residual oxide film after the first of stirring can be broken by once more stirring. The bonds are mainly composed of a new alloy, which have a higher content of aluminum and are free of continuous oxide film, showing higher shear strength of 113 MPa than that of the base materials.
In this paper, 2024 Al alloy and AZ31 B Mg alloy were brazed with aid of stirring without flux in air.The effects of the brazing temperature on microstructure and shear strength of the joint were investigated. The diffusion zone is found at joint interface near Al base metal,which consists of Al–Zn–Sn solid solution. At the same time, continuous intermetallic compounds(IMCs) phase and broken ones are found at joint interface near Mg base metal, which mainly consists of the Mg2 Sn phase. With the increase of the brazing temperature, the shear strength at the joint interface near Al base metal rises gradually. On the contrary, that of the joint interface near Mg base metal obviously decreases.
