STRUCTURE AND MECHANISM OF BONDING AT A DIFFUSION-BONDED AL/SIC INTERFACE

Al/SiC interfaces were fabricated by diffusion bonding a pure Al foil between two blocks of SiC for temperatures ranging from 500 to 600-degrees-C. For samples bonded below 586-degrees-C, the interfacial strength was low and TEM specimens could not be fabricated due to separation of the Al and SiC pieces during thinning. For samples bonded at and above 586-degrees-C, a strong bond was formed and conventional and high-resolution transmission electron microscopy revealed the formation of a thin amorphous phase at the interface. Compositional analysis showed that the interfacial phase contained Al, Si, C and 0. Formation of the amorphous phase was demonstrated to occur by a solid state reaction and is discussed on the basis of thermodynamic and kinetic considerations. Lastly, some of the advantages of having an amorphous phase at a metal/ceramic interface are discussed.