Vacuum brazing of Cf/β–spodumene composites and Ti–6Al–4 V alloy using Ag–Cu filler metal

Abstract

Interfacial microstructure and mechanical properties of Ti–6Al–4V/Cf/β–spodumene composites joints brazed by Ag–Cu eutectic brazing filler were investigated. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of Ti–6Al–4V/Cf/β–spodumene composites joints were studied. The result indicated that the typical interfacial microstructure of the joint was Ti–6Al–4V/Ti2Cu+α-Ti (s,s)/Ti2Cu/TiCu/Ag (s,s)/Cu (s,s)/Ti2Cu3/TiSi2+TiC/Cf/β–spodumene composites. The thickness of the diffusion layer, Ti2Cu3 layer, and reaction layer on the interface of Cf/β–spodumene composites increased with the brazing temperature or holding time increasing, meanwhile, the thickness of Ti–Cu layers decreased. The diffusion of Ti in brazing seam, which was significantly determined by the brazing temperature and holding time, was a decisive factor on the interfacial microstructure and mechanical properties of brazed joints. The optimal shear strength of joint brazed at 880°C for 10min was 33.5MPa. Further raising the brazing temperature or extending the holding time would reduce the shear strength of joints. Brazing specimens brazed at 880°C and 910°C for 10min broke in form of cleavage fracture after shearing test. Moreover, the formation of excessive thickness of TiSi2+TiC layer or Ti3Cu4 reaction layer was harmful to the mechanical property of the joint.