Si3N4/AgCu/TiAl钎焊接头界面结构及性能

Interfacial Structure and Properties of Si3N4/AgCu/TiAl Brazing Joints

摘要:

采用AgCu非活性钎料实现了Si3N4陶瓷与TiAl基合金的钎焊，确定接头的典型界面组织结构为：TiAl/Ti3Al+Ti(s,s)/AlCuTi/Ag(s,s)+AlCu2Ti/Ti5Si3+TiN/Si3N4陶瓷。钎焊过程中，活性元素Ti从TiAl母材溶解到钎料中与Si3N4陶瓷发生反应润湿，实现了TiAl与Si3N4陶瓷的连接。随着钎焊温度的升高及保温时间的延长，靠近Si3N4陶瓷的TiN反应层厚度增加，Ag基固溶体中弥散分布的AlCu2Ti化合物聚集长大成块状，导致接头性能下降。当钎焊温度T=860 ℃，保温时间为5 min时接头抗剪强度达到最大值124.6 MPa。基于反应热力学及动力学计算TiN层反应激活能Q约为528.7 kJ/mol，860 ℃时该层的成长系数KP=2.7×10-7 m/s1/2

Abstract:

The non-active AgCu filler metal was used to join Si3N4 ceramics to TiAl-based alloys. The typical interfacial microstructure of the joints was determined as TiAl/Ti3Al+Ti(s,s)/AlCuTi/Ag(s,s)+AlCu2Ti/Ti5Si3+TiN/Si3N4 ceramics. During the brazing process, the active element Ti, which dissolves into the non-active AgCu liquid filler metal, involves in the wetting on the Si3N4 ceramic and reacts to the ceramic materials. With the increase of brazing temperature and holding time, the thickness of the TiN reaction layer close to the Si3N4 ceramic increases and AlCu2Ti compounds dispersed in the Ag-based solid solution gather greatly, which reduces the joining properties. The shear strength of the joints reaches a maximum of 124.6 MPa when the brazing temperature T = 860 oC and the holding time t=5 min. According of the thermodynamics and kinetics calculation, the activation energy Q and the growth coefficient KP of the TiN layer are 528.7 kJ/mol and 2.7×10-7 m/s1/2, respectively