Processing, microstructure and mechanical properties of vacuum-brazed Al2O3/Ti6Al4V joints

The vacuum brazing of alumina ceramic to Ti6Al4V alloy was performed using Ag–Cu eutectic filler metal. The microstructure at the ceramic-metal interfaces and the mechanical properties of the brazed joint were examined. The microstructure of the joint brazed at 825 °C for 10 min consisted of α–β Ti, Ti2Cu, TiCu, Ti3Cu4, Ag-based solid solution and Ti4(Cu,Al)2O phases starting from Ti6Al4V to alumina substrate. The brazing parameters had a strong influence on the microstructure and shear strength of the joint. The brittle fracture mainly propagated in the alumina substrate. The highest shear strength was obtained when the joint was brazed at 825 °C for 10 min. When a Cu foil was sandwiched between two Ag–Cu brazing foils, the microstructure of the joint changed greatly and the shear strength increased correspondingly.