Reliable joining Al₅(TiZrHfNb)₉₅ multicomponent alloy and Nb using Ti–Ni filler metal

The reliable joining of Al₅(TiZrHfNb)₉₅ multicomponent alloy and Nb was achieved by the reaction of Ti–Ni filler and base materials. The relation of the microstructure evolution and brazing temperature was analyzed to reveal the brazing mechanism. The joint property was evaluated by the shear strength. The results showed that the liquid brazing filler reacted with Nb substrate to form a TiZrHfNb layer adjacent to the Nb, and the brazing seam was composed of TiZrHfNb matrix, (Ti,Zr,Hf)₂Ni and (Hf,Zr,Ti)₂Ni phases. Increasing the brazing temperature promoted the Al₅(TiZrHfNb)₉₅ to dissolve into the brazing filler, and the (Ti,Zr,Hf)₂Ni and (Hf,Zr,Ti)₂Ni phases volume enlarged. The (Ti,Zr,Hf)₂Ni and (Hf,Zr,Ti)₂Ni phases were beneficial to the property of the brazing seam. But high volume of (Ti,Zr,Hf)₂Ni and (Hf,Zr,Ti)₂Ni facilitated the propagation of cracks in the brazing seam, seriously weakening the joint shear strength. When the Al₅(TiZrHfNb)₉₅ and Nb were brazed at 1150 °C for 20 min, the maximum shear strength achieved at room temperature was 338 MPa, and the crack was located in the brazing seam.