MULTILAYER DIFFUSION BONDING OF POLYCRYSTALLINE AI203TO AI ALLOYS CONTAINING Sr, Mg, AND Si

Multilayered ceramic-metal composites were produced by solid state diffusion bonding of polycrystalline alumina and three Al alloys containing 1 to 2%Sr, 2% Mg and Mg + Si (5057 Al alloy). The multilayered structures were fabricated at 610°C under a compressive stress of 3 MPa for 2 hours in He-5%H atmosphere. The ceramic-metal interfaces were studied by SEM and TEM equipped with an energy dispersive spectrometer (EDS). Addition of 1 wt % Sr to Al promoted good adhesion, without producing any interfacial products, while the AI-2wt%Sr was poor in this regard due to the presence of dispersed AI4Sr, which is an intrinsic phase in the AI-Sr phase system. The AI-2%Mg alloy produced a continuous film at the interface, which was characterized as being MgAh04. Al alloys containing Mg and Si (5057 commercial alloy) produced not only the spinel structure (MgAh04), but another phase rich in Mg and Si (close to Mg2Si). These latter interfacial reaction products were not the intrinsic phases in AI-Mg alloys, but were reaction products at the Ah03 -AI alloy interfaces