Interfacial Microstructure of Silicon Carbide and Titanium Aluminide Joints Produced by Solid-State Diffusion Bonding

Abstract

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+Ti2AlC, a layer of Ti5Si3CX containing Ti2AlC particles and a layer of TiAl2. However, the TiAl2 layer is formed during cooling. The actual phase sequence at the bonding temperatures of 1573 K and 1673 K are SiC/TiC/(TiC+Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti1� XAl1þX/TiAl and SiC/TiC/(TiC+ Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti5Al11/Ti1� XAl1þX/TiAl, respectively. Ti5Al11 and Ti1� XAl1þX rapidly transform to TiAl2 during cooling. The layers grow obeying the parabolic law. The growth rate of the reaction layers change sensitively depending on the bonding temperature.