Reactive joining of alumina by oxidation of Al interlayers

Abstract

Al2O3 bars were butt-joined by brazing with thin Al interlayers. After brazing, an attempt was made to oxidize the Al interlayers to convert the metal to a crystalline ceramic. While pure Al interlayers did not oxidize significantly even under severe conditions (pure O-2, 1600degreesC for 4 hours), addition of MgO in the joint or alloying the interlayers with Si and Fe dramatically increased the oxidation of the interlayer according to SEM analysis. Heat treatment under pure O-2 resulted in more complete oxidation compared to similar treatments in air. The highest strength as measured with four-point bending of Al-brazed and oxidized joints was 112 MPa. The advantages offered by this approach include its relative simplicity and its ability to form a fully ceramic joined assembly.