锂霞石复合玻璃钎料连接碳化硅陶瓷接头的应力缓释机理

To solve thermal mismatch problem in the bonding process of RB-SiC ceramic using borosilicate glass braze (BS), β-eucryptite/BS composite braze (BSL) was designed. The effect of β-eucryptite addition on a) the characteristictemperature, thermal expansion coefficient and wettability of composite glass braze, as well as b) the microstructure and mechanical properties of joints was investigated. The thermal expansion coefficient of BSL decreases and its rate increases with the increase of β-eucryptite amount. Also, the characteristictemperature of BSL and its rate both increase with the increase of β-eucryptite amount. The apparent contact angle of BSL increases at the same temperature, and the variation of apparent contact angle along with temperature becomes slow. The RB-SiC/composite glass solder (BSL3)/RB-SiC joint has the similar interface to the RB-SiC/BS/RB-SiC joint bonded at 850℃ for 10 min. However, in the glass seam, β-eucryptite turns into massive gray KAlSiO₄ crystals (i.e., kaliophilite). The massive KAlSiO₄ crystals with a negative expansion characteristic can reduce the thermal expansion coefficient and prevent the crack propagation, thus strengthing the joint. The shear strength of the joint after reinforcement increases from 5.2 MPa to 10.9 MPa.