New technique for pressureless infiltration of Al alloys into Al2O3 preforms

Al alloys were infiltrated into alumina preforms without the aid of pressur e in N-2 as well as in air at and above 750 degreesC. It was possible to el iminate 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 long er periods of time, consequently producing greater thickness of composite. In air, Mg placed at the interface getters the in-coming oxygen until the a lloy billet melts and seals off the front from the ingress of the furnace a tmosphere thereby eliminating the need for prealloying Al with Mg and N-2 a tmosphere. In addition, experiments in argon revealed that the infiltration requires some critical amount of N-2 in the atmosphere.