Abstract
Wetting behavior of 72Ag-28Cu-x%Ti alloys on SiC was investigated in a vacuum of 10-3Pa, Ti-free Ag-Cu alloy did not wet SiC and the contact angle became about 160°. With more than 0.5% Ti, the alloy wetted SiC well. Wetting of SiC by Ag-Cu-x% Ti alloy was thought to proceed by the adsorption of active metal Ti at the interface. In Ag-Cu-0.2% Ti alloy, the wetting angle became about 130° in a vacuum of 10-3Pa, but the alloy reacted with SiC. Microstructure and composition at the surface and bulk of each alloy after wetting experiment were analyzed by SEM and EDX. Non-wetting behavior of Ag-Cu-0.2% Ti alloy on SiC was thought to have resulted from the presence of atmospheric oxygen. Thus, Ti was consumed by the reaction with the atmospheric oxygen at the surface of the alloy leaving little Ti available to wet SiC. But for more than 0.5% Ti, a considerable amount of Ti for adsorption remained and wetted SiC. When the amount of atmospheric oxygen was increased, the reaction between oxygen and Ti in the brazing alloy became active and therefore the alloy could not wet SiC even in the case of Ag-Cu-2% Ti. The state that brazing alloy contacts with atmospheric oxygen is much different between the cases of wetting and joining experiments. Ag-Cu-0.2% Ti alloy could join SiC successfully, even though the contact angle was about 130° in wetting experiment, probably because it was difficult for Ti to react with the atmospheric oxygen in joining experiment and Ti could adsorb at interface.
