Joining and wetting of CaO-stabilized ZrO2 with Al-Cu alloys

Abstract

The contact angles of molten Al-Cu alloys on CaO-stabilized ZrO2 have been measured using a sessile drop technique at 1373 K under a vacuum. The work of adhesion, Wad, of an alloy against ZrO2 was evaluated from the equilibrium contact angle of the alloy. The Wad values Al-Cu alloys with copper contents up to 10 at% are the same or slightly higher than the value of 1.25 J m−2 for pure aluminium. On further increase in copper content, Wad gradually decreases to 0.8 J m−2 for pure copper at 1373 K. The general trend in the work of adhesion against copper content of Al-Cu alloys is in accordance with the copper-content dependence of the joining strength of ZrO2 joints brazed with the Al-Cu alloys. A ZrO2 joint brazed with Al-1.7 at% Cu filler provides the maximum fracture strength of 105 MPa at room temperature, and this improved strength of ZrO2 is maintained at elevated temperatures up to 773 K. The joining strength of a ZrO2 joint brazed with an Al-Cu alloy is dominated by the mechanical properties of the alloy in addition to the wettability of the alloy against ZrO2.