Interfacial microstructure and mechanical properties of joining electroless nickel plated quartz fibers reinforced silica composite to Invar

Vacuum brazing of electroless nickel plated quartz fibers reinforced silica composite (QFSC) to Invar alloy using Ag-Cu eutectic alloy at various temperatures (1073-1163 K) and times (5-35 min) has been investigated. The scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction examination of the joints showed that the junction between QFSC and Invar produced reaction products like Cu3.8Ni, Cu (s, s), Ni (s, s) and Ag (s, s), with the structure of Invar/Cu3.8Ni + Ni (s, s)/Ni (s, s) + Cu3.8Ni + Ag (s, s) + Cu (s, s)/Cu (s, s) + Cu3.8Ni + Ni (s, s) + QFSC. The shear strength of joint was effected by the changes of relative amount of Cu-Ni eutectic structure (Cu3.8Ni + Ni (s, s)) and thickness of nickel plating film at different parameters. The shear strength of joint increased when there were proper amount of Cu-Ni eutectic structure and nickel plating film for reinforcement, and decreased while them were consumed excessively in interaction. The maximum shear strength of joint is 29 MPa, which was brazed at 1103 K for 15 min.