TC4/TNM钎焊接头界面组织及性能

Interfacial Microstructure and Mechanical Property of TC4 / TNM Brazed Joints

摘要:

采用Ti-25.65Zr-13.3Cu-12.35Ni-3Co-2Mo(wt.%)非晶箔带钎料在900 ℃~1020 ℃/10 min工艺下真空钎焊连接TC4和TNM合金,并系统研究了TC4/TNM钎焊接头的界面组织和形成机理以及钎焊温度对界面组织和剪切强度的影响规律。结果表明：钎焊温度900～980 ℃时接头的组织为TC4/细小网篮状(α+β)-Ti/γ-(Ti,Zr)2(Cu,Ni) + α-Ti/Ti3Al/TNM,随钎焊温度升高,钎缝中硬脆的γ相减少、韧性的α-Ti增加。钎焊温度1000 ℃和1020 ℃时,接头的界面反应层由三层演变成两层且对应的物相分别是韧性差的粗针状(α+β)-Ti和Ti3Al,粗针状(α+β)-Ti随温度升高进一步粗化。钎焊接头剪切强度随温度升高先增加后减小,钎焊温度980 ℃时剪切强度达到最大值494.83 MPa。剪切测试的钎焊接头均脆性断裂于TNM侧的钎缝中。

Abstract:

Vacuum dissimilar brazing of TC4 alloy and TNM alloy was performed at 900 ~ 1020 °C for 10 min using amorphous Ti-25.65Zr-13.3Cu-12.35Ni-3Co-2Mo (wt.%) filler. The interfacial microstructure and formation mechanism of the TC4/TNM brazed joint and the variation of the interfacial microstructure and shear strength of the brazed joints as brazing temperature were systematically investigated. Results revealed that the interfacial microstructure of the TC4/TNM joints brazed at 900 ~ 980 ℃ were TC4/ fine basket weave (α+β)-Ti/γ-(Ti, Zr)2(Cu, Ni) + α-Ti/Ti3Al/TNM. The brittle γ-(Ti, Zr)2(Cu, Ni) decreases but the ductile α-Ti increases with brazing temperature. Once the brazing temperature increased to 1000 °C and 1020 °C, the interfacial reaction layer of the TC4/TNM brazed joints transformed from three layers into two layers, which consist of coarse acicular (α+β)-Ti with poor ductility and Ti3Al, respectively. And the coarse acicular (α+β)-Ti was further coarsened with brazing temperature. The shear strength of the TC4/TNM brazed joint increased first and then decreased with brazing temperature. The maximum shear strength of 494.83 MPa was obtained at 980 ℃. The brittle fracture primarily occurs in the brazing seam near TNM side regardless of brazing temperature during shear test.