Static tensile crack behavior of brazed joints of dissimilar metals tubes in aerospace system

The dissimilar metals(such as Titanium alloy and stainless steel) thin-wall small-diameter tube structures in aerospace propulsion system were bonded, using high frequency induction brazing process. Their qualities and properties are largely superior to the bolt connection tubes structures. The static tensile experiments of the brazed joints were conducted. The results indicate that the mechanical properties of joints brazed using Ag-based filler metals are slightly better than those using Cu-based filler metals. And then the joints microstructures after static tensile experiments were analyzed. It is found that, all the cracks in the joint area brazed by Ag-based filler metals germinate and propagate in the brazing seam, the cracks stop when they propagate on the interfaces between brazing seam and the base metals. The cracks in the joint area brazed by Cu-based filler metals germinate in three locations: the boundary of two phases in the brazing seam, the interface between brazing seam and Titanium alloy, the interface between brazing seam and stainless steel. The crack driving force consists mainly of the static tensile load and the mismatch behaviour of dissimilar metals brazed joint. And the resistance force of crack extension is related to the microstructures in the brazed joint.