Sn或V元素对TA2钛合金钎焊界面调控机制

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

摘要:

钎焊技术是实现燃气轮机部件结构完整性的重要手段，国内成熟的钛基钎料及其钎焊工艺高度匮乏，研究了Ti-Zr-Cu-Ni钎料成分及钎焊工艺对TA2钛合金钎焊接头界面结构和拉伸性能的影响，探讨了钎料中引入Sn或V元素对钛合金钎焊界面的调控机理。结果表明，钎料中引入Sn或V元素和降低钎焊温度，在钎焊界面处形成的脆化层和晶间渗入区的厚度减薄。钎料中添加1.5wt% V或5wt% Sn形成的强化相导致钎焊接头抗拉强度增大。钎焊温度升高引发界面冶金反应加剧并形成多种硬脆相，致使接头抗拉强度增大，但拉伸强度随保温时间延长而减小。钎料、界面结合层和基体断口分别呈现脆性、类解理和韧性断裂形貌。Sn与Ti、Zr形成Ti₂Sn₃、Ti₆Sn₅、Zr₅Sn₃等强化相，V与Ni形成Ni₃VZr₂、NiV₃、Ni₂V等强化相，均导致接头抗拉强度增大；V与Ni结合，减缓Ni元素向钛合金中扩散，调控钎焊界面冶金反应。

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.