Microstructure and mechanical response of the SiO2f/SiO2 composite and Invar alloy joints brazed with an AgCuTi alloy

摘要

The SiO2f/SiO2 composite and the Invar alloy were brazed at 860 degrees C from 5 min to 25 min using an AgCuTi alloy. Scanning electron microscopy(SEM) equipped with an energy dispersive spectrometer (EDS) was employed to examine the elemental distribution in the joint. X-ray diffraction (XRD) and transmission electron microscopy (TEM) was selected to accurately identify the species, morphologies and crystal structures of the reaction products. The effect of the holding time on the interfacial microstructure evolution of the joint was studied in detail. The shear strength of the joints and the fracture morphologies were closely related to the thickness of the whole reaction layer, as well as the thickness ratio of the Ti5Si3 + TiO2 layer to the CuxTi6-xO layer. The maximum shear strength was 26 MPa obtained at 860 degrees C for 10 min. Finally, the formation of the reaction products in the joint was analyzed by thermodynamic calculations. A brazing mechanism was proposed based on the experimental results. (C) 2016 Elsevier Ltd. All rights reserved.