DC-assisted rapid wetting of 3Y-PSZ by molten 72Ag–28Cu and its application in joining

The effects of current polarity, temperature and current intensity on the wettability of 3 mol% yttria-partially stabilized zirconia (3Y-PSZ) by molten 72Ag–28Cu were investigated using a direct current (DC)-coupled sessile drop method. The wettability was significantly improved with the assistance of a DC, especially when 3Y-PSZ was connected to anode. Noticeably, the contact angle rapidly decreased from 143° to smaller than 20° when the current intensity was larger than +10 mA. The wettability also showed abnormal dependence on temperature, presumably due to the competition between nucleation and growth of the m(AgCu₄Zr) phase at the interface. The mechanisms for the significant improvement in the wettability under the DC application were ascribed to the formation of substoichiometric ZrO_2-δ, the release and adsorption of metallic Zr, and the formation of wettable m(AgCu₄Zr) phase at the interface. The DC-assisted wetting provides a new strategy for the rapid and robust joining of 3Y-PSZ to metals.