THE WETTING AND BONDING OF SI3N4 BY COPPER-TITANIUM ALLOYS WITH OTHER ELEMENTS

The wettability of pressureless sintered Si3N4 by ternary alloys of copper, titanium and aluminium, silicon and yttrium has been investigated in vacuum at 1160°C. The bond strength of Si3N4 to itself was also evaluated by compressive shear test. While the wettability is influenced by the titanium activity, it may be overcome by the surface tension of the alloy. Titanium activity is lowered when aluminium and silicon, which have high interactions with titanium, are added. On the other hand, titanium activity is enhanced when yttrium, which has a low interaction with titanium, is added. It was found that TiN and various Ti-silicides formed in the reaction layer. The type and position of the reaction products are changed by the titanium activity, according to the alloying additions and their contents. Higher strength was obtained with the addition of aluminium and thin reaction layer formation. As the reaction temperature and time were increased, shear strength decreased due to the increased thickness of the reaction layer and the formation of a brittle phase in spite of improved wettability. Aluminium appeared to be the most effective element for the control of interfacial reaction. Yttrium addition (less than about 5 %wt) was also very effective in increasing strength under very low concentrations of titanium (less than about 5 %wt). © 1990.