Joining of Alumina/Alumina Using Al-Cu Filler Metal and Its Application to Joning of Alumina/Aluminum

Abstract

The sessile drop technique was conducted to measure the contact angle of molten aluminum-copper (0-100 mass% Cu) alloys against alumina under vacuum, and the joining strength of alumina to alumina joint using aluminum-copper filler metals was measured by fracture shear loading. Further, alumina was metallized with aluminum or 4 mass% copper-aluminum alloy filler, and brazed to A1050 under vacuum. The results obtained are summarized as follows.
(1) The work of adhesion of Al-Cu alloys to alumina at 1373 K increases from 1.31 J/m² for pure Al to 1.35 J/m² for 30 mass% Cu containing alloy, and decreases to 0.157 J/m² for pure copper. This results suggest that on aluminum rich side the interaction of aluminum and copper in the alloys affects the wetting of aluminum and copper against alumina.
(2) The shear strength of alumina/alumina joint with Al-Cu fillers depends on the work of adhesion of the Al-Cu fillers, and also on the strength of the fillers. The fillers composed of (a+θ) phases are applicable to joining of alumina. In particular, alumina/alumina joint with 4 mass%Cu -aluminum filler exhibits the high strength of 157 MPa.
(3) The change in strength of Al₂O₃/Al₂O₃ joint with Al-4 mass% Cu filler with testing temperature is small up to 500 K. At further higher temperature the strength of the joint decreases with softening the alloy.
(4) After metallizing alumina with Al or Al-4 mass% Cu filler at 1373 K for 3.6 ks, the alumina is brazed to A 1050 with BA4004 at 883 K for 180 s or 900 s. The joining strength of Al₂O₃/Al joint where Al₂O₃ is metallized with Al-4 mass% Cu filler exhibits the higher value than that of Al₂O₃/Al joint where Al₂O₃ is metallized with Al.