Effect of element Zr in Ti-Zr–Ni-Nb system brazing filler alloys on the microstructure and strength of TiAl/TiAl joints

A series of Zr-Ti-Ni-Nb system filler alloys with different content of Zr were developed and fabricated for TiAl joining. The phase characteristics of typical joint interface microstructure were analyzed, and the effect of element Zr on the microstructure and strength of the joints was investigated. The results showed that when the content of Zr was 5 ~ 11 wt. %, the joint was composed of Ti₂Al, Ti–Al-Ni, Ti₃Al, Ti₂AlNi dissolved with Zr. With the content of Zr was greater than 25 wt. %, elements Ni, Zr and Nb were enriched in the central part of the joint, and the predominant phase in the reaction zone of the joint was (Ti,Zr)₂AlNi dissolved with Nb. The joint brazed with Zr(8 ~ 11)-Ti(Bal.)-Ni(18 ~ 21)-Nb(15 ~ 17) (wt. %) filler at 1010 °C for 10 min exhibited the maximum average the shear strength of 280.2 MPa. For the filler alloys with the Zr content of 40 wt. % and 60 wt. %, cracks were detected in the as-brazed joints.