Effects of germanium additions on microstructures and properties of Al–Si filler metals for brazing aluminum

A series of Al–Si–Ge filler metals were studied for brazing aluminum. The microstructures and properties of the filler metals were investigated systematically. The results show that the liquidus temperature of Al–Si–Ge filler metals drops from 592 to 519 °C as the content of Ge increases from 0 to 30% (mass fraction). As the content of Ge increases, bright eutectic Ge forms. However, as the Ge content exceeds 20%, the aggregation growth of the eutectic structure tends to happen and coarsened primary Si–Ge particle forms, which is detrimental to the properties of alloys. The Al–10.8Si–10Ge filler metal has good processability and wettability with the base metal Al. When this filler metal is used to braze 1060 aluminum, the complete joint can be achieved. Furthermore, the shear strength test results show that the fracture of brazed joint with Al–10.8Si–10Ge filler metal occurs in the base metal.