Feasibility of aluminium nitride formation in aluminum alloys

The feasibility of forming aluminum nitride by in situ reactive nitrogen gas injection into molten aluminum alloys has been evaluated both analytically and experimentally over the temperature range from 700 to 1500°C. It is shown that aluminum nitride can be melt formed in the presence of Mg and Si, with nitrogen and/or ammonia as the reactive gases at temperature above 1100°C. In this role, magnesium serves as a catalyst. Magnesium niride is first formed in the vapor phase by the reaction of vaporized magnesium and nitrogen gas, followed by incorporation of magnesium nitride particles into the molten aluminum. Via an in situ substitution reaction, aluminum nitride forms between magnesium nitride and aluminum. Up to 17 wt.% aluminum nitride in an aluminum alloy has been formed with an average reinforcement size of 3 μm. The potential for this process permits economical liquid phase processing of aluminum nitride-aluminum metal matrix composite with nitrogen gas injection for structural, thermal and wear applications.