HIGH-RESOLUTION ELECTRON-MICROSCOPY OF A SIC/SIC JOINT BRAZED BY A AG-CU-TI ALLOY

Microscope observations were performed on the joined portion of a brazed polycrystalline or single crystal SiC to itself with (Ag-28 wt. percent Cu) plus 2 wt. percent Ti alloy foil. The brazing was done under vacuum at temperatures of 800 degree C to 950 degree C with a holding period of up to 30 min. Reaction products formed at the joined interface were mainly TiC. In the specimen brazed at 800 degree C with the holding time of 0 min, TiC formed into small crystallites and an amorphous-like layer was found between SiC and TiC. On the other hand, TiC was formed as a lyer along the joined interface for the specimen brazed at 950 degree C for the holding time of 30 min. Lattice matching of SiC to TiC crystals appeared to be good so the high bonding strength of the joint is attributed to the formation of this epitaxial interface.