Microstructure and mechanical properties of Ti2AlNb alloy and C/C composite joints brazed with Ag–Cu–Zn and Ag–Cu–Zn/Cu/Ag–Cu–Ti filler metals

Abstract

C/C composite was successfully joined to Ti2AlNb alloy with inactive filler metal, Ag–Cu–Zn filler. In addition, a designed composite interlayer, Ag–Cu–Zn/Cu/Ag–Cu–Ti, was used to improve the properties of brazed joints. AlCu2Ti compound blocks were formed in brazing seam and the double reaction layers adjacent to C/C composite were AlCu2Ti and TiC when Ag–Cu–Zn filler was used to join C/C composite and Ti2AlNb. With the increase of brazing temperature and time, the amount of AlCu2Ti compound blocks increased and tended to accumulate together nearby the C/C composite, the double reaction layers thickened as well. In order to avoid the serious accumulation of brittle AlCu2Ti compound nearby C/C composite, Cu foil was added between the Ag–Cu–Zn filler and Ti2AlNb. Soft Cu but not brittle AlCu2Ti existed nearby the C/C composite with the addition of Cu foil, which is beneficial for the relief of residual stress near the C/C composite, and the shear strength of joint improved obviously. With the barrier of Cu foil, the thickness of reaction layers adjacent to C/C composite could be controlled easily by the addition of Ag–Cu–Ti foil. Correspondingly, the shear strength of this joint reached at 28MPa, which was close to that of C/C itself.