Analysis of interface fracture behavior of arc fusion-brazed joint between titanium and aluminum dissimilar alloys

Fusion-brazing of titanium alloy to aluminum alloy was achieved by TIG arc,and the interface microstructure and fracture characteristics of the joints made with different fillers were analyzed. The results indicate that the interface microstructure in the joints with pure Al filler consisted of TiAl₃ phase,and cracks initiated at the interface corner and propagated along the interface between TiAl₃ layer and welded seam. The facture style changed to tearing through the welded seam when the crack propagated to the back side,and the tensile strength of the joint was 139 MPa. In contrast,the interface of the joints with Al-Cu-La filler exhibited dual layers,containing TiAl₃ and Ti₂Al₂₀La phases. The fracture happened along the interface between TiAl₃ layer and Ti alloy substrate. The microcracks at the interface acted as the crack sources during the tensile test,and the fracture occurred in the interfacial layer with quasi-cleavage features. The tensile strength of joint with Al-Cu-La filler reached 270 MPa. The double compound layers formed due to the effect of La, which was the key to improve the joint strength.