BNi-2非晶钎料钎焊高铌TiAl合金与GH3536合金接头组织与性能

采用非晶态BNi-2钎料成功实现了高铌TiAl合金与GH3536合金的连接，获得良好的钎焊接头。钎焊接头的典型界面组织为TAN/B2+τ3/τ4+（Ni-Ti）-B/γ+（Ni-Ti）-B+CrB+G相/GH3536。通过分析钎焊温度对接头界面微观组织的影响，表明BNi-2钎料中B元素的扩散以及GH3536合金向液态钎料中的溶解对界面组织结构演变起着至关重要的作用。而随着钎焊温度的升高，扩散IV区逐渐消失，接头由4个区域变为3个区域，τ3/τ4化合物层及钎缝区域均逐渐增厚，黑色CrB相发生粗化，细小点状（Ni，Ti）-B含量减少。1 160℃保温10 min时，所获得的钎焊接头最大室温及高温（700℃）抗剪强度分别为~106.8 MPa和~76.2 MPa，其剪切强度降低约28.6%，接头均呈现脆性断裂模式。接头形成过程可以划分为固相扩散、液相生成、等温扩散凝固和残余液相析出4个阶段。

Interfacial microstructure and mechanical properties of high Nb containing TiAl alloy and GH3536 superalloy brazed using amorphous BNi-2 filler

High Nb containing TiAl alloy and GH3536 superalloy is brazed successfully by using amorphous BNi-2 filler metal and sound joints were obtained. The typical interfacial microstructure of the brazed joint consists of TAN substrate/B2+τ3/τ4+(Ni-Ti)-B/γ+(Ni-Ti)-B+CrB+G phase/GH3536 superalloy. The effects of brazing temperature on the interfacial microstructure of joints are then investigated. The results show that the diffusion of element B in BNi-2 and the dissolution of the elements from GH3536 alloy into the liquid brazing alloy play a crucial role in the evolution of the interfacial microstructure. With the increase of brazing temperature, the diffusion zone IV gradually disappears and the joint changes from four areas to three. It appears that the thickened τ3/τ4 compound layer and the brazing seam coarsened the black CrB phase, reducing the content of small dots (Ni, Ti)-B. After 10 min at 1160 ℃, the optimal shear strength of the joints at room temperature and high temperature (700 ℃) is about 106.8 MPa and 76.2 MPa, respectively, decreasing by about 28.6%. All the brazed joints exhibit a brittle fracture mode after the shear test. The process of joint formation can be divided into four stages: solid phase diffusion, liquid phase formation, isothermal diffusion solidification, and residual liquid phase precipitation.