Active cement added brazing of quartz fibers reinforced silica composites to Invar alloy

Quartz fibers reinforced silica composites (QFSC) was bonded with Invar alloy effectively through one kind of active cement added brazing process. The results show that the active cement composing of TiH₂ reinforces the wettability of QFSC through reaction, and the bonding is formed by interface diffusion and reaction of Ti, Ag-Cu eutectic, pure Cu and matrix materials in brazing. There are seven reaction products generated in the joint QFSC/Invar brazed, namely as TiO, TiC, CuTi, Fe₂Ti, Si, Ag (s, s) and Cu (s, s). The interfacial structure of QFSC/Invar joint can be described as QFSC/TiO+Si+TiC+Cu (s, s)/CuTi+Cu (s, s)+Ag (s, s)/Cu (s, s)+Ag (s, s)+Fe₂Ti/Invar. The maximum shear strength is 44 MPa for the QFSC/Invar joint brazed at 850°C for 15 minutes. The pre-coating of active cement at the surface of QFSC, and the reactions between Ti, quartz fibers and filler metals are the key factors for effective bonding.