Interfacial microstructure of silicon carbide and titanium aluminide joints produced by solid-state diffusion bonding

This paper describes the microstructure and the formation mechanism of solid-state diffusion bonded interfaces of silicon carbide (SiC) and titanium aluminide (TiAl). Two SiC specimens were diffusion bonded using a Ti-48 at%Al foil in vacuum. The interfacial microstructure has been investigated by means of scanning electron microscopy, electron probe microanalysis and X-ray diffraction. Four layers of reaction products are formed at the interface by diffusion bonding: a layer of TiC adjacent to SiC followed by a diphase layer of TiC+Ti 2 AlC, a layer of Ti 5 Si 3 C X containing Ti 2 AlC particles and a layer of TiAl 2 . However, the TiAl 2 layer is formed during cooling. The actual phase sequence at the bonding temperatures of 1573 K and 1673 K are SiC/TiC/(TiC+Ti 2 AlC)/(Ti 5 Si 3 C X +Ti 2 AlC)/Ti 1ÀX Al 1þX /TiAl and SiC/TiC/(TiC+ Ti 2 AlC)/(Ti 5 Si 3 C X +Ti 2 AlC)/Ti 5 Al 11 /Ti 1ÀX Al 1þX /TiAl, respectively. Ti 5 Al 11 and Ti 1ÀX Al 1þX rapidly transform to TiAl 2 during cooling. The layers grow obeying the parabolic law. The growth rate of the reaction layers change sensitively depending on the bonding temperature