TiAl与Si3N4f/Si3N4复合材料钎焊接头界面结构及性能研究

采用AgCuTi钎料实现了TiAl与Si3N4f/Si3N4复合材料的钎焊,确定了钎焊接头的典型界面组织结构为TiAl/AlCuTi/Ag(s,s)/TiN/Si3N4f/Si3N4。钎焊过程中,液相钎料在Si3N4f/Si3N4复合材料表面发生较好润湿,钎料中活性元素Ti与Si3N4基体及纤维发生反应形成连续的TiN化合物层。过高的钎焊温度或过长的保温时间导致钎缝中脆性的AlCuTi化合物增加,且由于接头应力的作用在钎缝中产生微裂纹甚至开裂,严重地降低了钎焊接头性能。当钎焊温度T=850℃,保温时间为10min时,接头抗剪强度达到最大,为9.4MPa,超过Si3N4f/Si3N4母材层间抗剪强度的60%。断口分析表明:压剪过程中,断裂发生在Si3N4f/Si3N4复合材料一侧。

Research on the Interfacial Structure and Properties of TiAl - Si3N4f/Si3N4 Brazed Joints

The TiAl alloy was brazed to Si3N4f/Si3N4 composite using AgCuTi filler metal. The typical interfacial microstructure of the joint is TiAl/AlCuTi reaction layer/Ag based solid solution/TiN reaction layer/Si3N4f/Si3N4. During the brazing process, liquid solder wets the surfaces of Si3N4f/Si3N4 composite well, and the active element Ti reacts with Si3N4 matrix and fibers to form continuous TiN compounds layer. The amount of brittle AlCuTi intermetallics increases when the brazing temperature is much higher or the brazing time is much longer. Some microcracks form in AlCuTi intermetallics due to the residual stress in the joint, which seriously degrade the joining properties. A maximum of 9.4 MPa of the shear strength can be obtained when the brazing temperature T=860 °C and holding time t=5 min, which exceeds 60% of the strength of composite materials. Fracture analysis shows that fracture occurs in the side of Si3N4f/Si3N4 composite.