New technique for pressureless infiltration of Al alloys into Al2O3 preforms

摘要

Al alloys were infiltrated into alumina preforms without the aid of pressure in N(2) as well as in air at and above 750 degreesC. It was possible to eliminate termination of infiltration that was seen in open conditions (where N(2) was in continuous contact with the melt) by modifying the infiltration geometry. This configuration enables the infiltration to continue for longer periods of time, consequently producing greater thickness of composite. In air, Mg placed at the interface getters the in-coming oxygen until the alloy billet melts and seals off the front from the ingress of the furnace atmosphere thereby eliminating the need for prealloying Al with Mg and N(2)atmosphere. In addition, experiments in argon revealed that the infiltration requires some critical amount of N(2) in the atmosphere.