Wetting and joint-formed characteristics of amorphous Ni-based filler metal foil and its influence on brazed joint formation

The control of the amount of amorphous nickel-based filler metal foil was analyzed, and the wetting and joint-formed characteristics of the amorphous nickel-based filler metal foil and brazed joint formation were studied. The results showed that the filler metal residual layer always exists after the brazing process with amorphous nickel-based filler metal foil, even when the filler metal is insufficient to fill in the joint. The migration of the interface between filler metal residual layer and base metal was observed, which was related to the interaction between molten filler metal and base metal. The thickness of filler metal residual layer increases with adding the filler metal foil, but the interface migration depth does not relate to the filler metal foil size. The joint-formed behavior of molten filler metal follows the minimum energy principle, the molten filler metal is affected by its own gravity, viscous force and the additional pressure are caused by surface tension, which flow into the seam with viscous fluid characteristics. The flow rate of liquid alloy in the boundary layer closing to steel surface gradually slows down, and the dissolution of base metal to the molten filler metal further reduces its fluidity. Finally the molten filler metal solidifies and the residual layer forms.