Modification Mechanisms of Sn or V Elements on Brazing Interface of TA2 Titanium Alloy

Abstract:

Brazing technology is an important method to realize structural integrity of gas turbine components. There is a lack of highly mature Ti-based filler metals and the corresponding brazing technology in China. The effects of Ti-Zr-Cu-Ni filler metal composition and brazing processes on the interface structure and tensile properties of TA2 titanium alloy brazed joints were studied. Modification mechanisms of Sn or V elements on the brazing interface were discussed. The results show that the thicknesses of embrittlement layer and intergranular infiltration zone at the brazing interface are obviously reduced by adding Sn or V elements and decreasing brazing temperature. The strengthening phase formed by adding 1.5wt% V or 5wt% Sn leads to an increase in the tensile strength of the brazed joint. The increase in brazing temperature leads to intensified metallurgical reactions at the interface and the formation of various hard and brittle phases, resulting in an increase in the tensile strength of the joint, but the tensile strength decreases with prolonged insulation time. The fracture surfaces of the filler metal, interface bonding layer, and the matrix exhibit brittle, cleavage-like, and ductile fracture morphologies, respectively. Sn is combined with Ti and Zr to form strengthening phases such as Ti₂Sn₃, Ti₆Sn₅, and Zr₅Sn₃, while V is combined with Ni to form strengthening phases such as Ni₃VZr₂, NiV₃, and Ni₂V, all of which lead to an increase in the tensile strength of the brazed joint. V combined with Ni slows down the diffusion of Ni element into titanium alloy and regulates the metallurgical reaction at the brazing interface.