Influence of silicon content on bonding ability and deformation resistance during brazing in Al–Si alloy single layer materials

In the conventional brazing method, a filler material is required. The filler material melts at the brazing temperature and bonds the members. This study demonstrates a new brazing method where the aluminum members are bonded without a filler material by using the liquid phase provided from the Al–Si alloy single-layer material. In the new method, the Al–Si alloy single layer material partially melts and provides the liquid phase during brazing. Generally, the amount of liquid phase is influenced by the Si content. Therefore, we investigated the influence of Si content on the bonding ability and deformation resistance in a single-layer material. The bonding ability was evaluated by using a test piece made of fin and base materials, and the deformation resistance was evaluated by a sagging test. The bonding ability increased with Si content, but the deformation resistance decreased. We clarified that the trade-off between these properties can be avoided by using Al–2.5 mass%Si alloy at 600°C brazing. We also investigated the influence of Si content on the metal structure and changes in the metal structure during brazing. Accordingly, we clarified that a spherical liquid phase formed from the Si phase and a laminar liquid phase formed through the grain boundaries.