FEASIBILITY OF ALUMINUM NITRIDE FORMATION IN ALUMINUM-ALLOYS

The feasibility of forming aluminum nitride by in situ reactive nitrog en gas injection into molten aluminum alloys has been evaluated both a nalytically and experimentally over the temperature range from 700 to 1500 degrees C. It is shown that aluminum nitride can be melt formed i n the presence of Mg and Si, with nitrogen and/or ammonia as the react ive gases at temperature above 1100 degrees C. In this role, magnesium serves as a catalyst. Magnesium nitride is first formed in the vapor phase by the reaction of vaporized magnesium and nitrogen gas, followe d by incorporation of magnesium nitride particles into the molten alum inum. Via an in situ substitution reaction, aluminum nitride forms bet ween magnesium nitride and aluminum. Up to 17 wt.% aluminum nitride in an aluminum alloy has been formed with an average reinforcement size of 3 mu m. The potential for this process permits economical liquid ph ase processing of aluminum nitride-aluminum metal matrix composite wit h nitrogen gas injection for structural, thermal and wear applications .