Brazing of C/C Composite to TiAl Alloy Using (Ti/Ni/Cu)f Multi-foil Filler

Abstract

C/C composite is brazed to TiAl alloy using (Ti/Ni/Cu)f multi-foil filler. The brazing joint displayed reliable interface bonding and excellent mechanical properties under high temperature. The research showed during brazing process, low-melting-point eutectic liquid-phase structure is firstly formed through the contact reaction at the Ti/Ni interface, then complete melt and diffusion of the filler occurred afterwards with Cu element dissolving. General microstructure of the joint show as follows: C/C/TiC/ Al2(Cu,Ni)Ti3C/Ti(Cu,Ni)+Al(Cu,Ni)2Ti/Al(Cu,Ni)Ti+Ti3Al/TiAl. The Ti(Cu,Ni) matrix phase and spheroidal dispersion of the Al(Cu,Ni)2Ti phase constitute the main components of the joint. A mass of fragile Ti2Ni phase caused by lower brazing temperature and shorter holding time reduced mechanical property of the joint. Higher brazing temperature and longer holding time made the interface structure of the C/C composite crack and TiC separate from the substrate, leading to a drop in shear strength of the joint. When the joint of the C/C composite and the TiAl alloy is brazing at 980℃ for 10 min, the shear strength reached the maximum 18 MPa at room temperature, and increased to 22 MPa at high temperature about 600℃.