Nanoscaled Al-AlN composites consolidated by equal channel angular pressing (ECAP) of partially in situ nitrided Al powder

Nanoscaled aluminium nitride (AlN) reinforced aluminium matrix composites were fabricated using a novel approach where powder mixtures of Al+Mg+Sn were partially in situ nitrided in flowing nitrogen followed by consolidation through equal channel angular pressing (ECAP). The resulting composites contain up to 23.8 vol% of AlN with relative density >98%. The microstructure shows two distinctively different alternate lamellar regions. One is the Al matrix free of AlN and the other is composed of nanoscaled AlN embedded in the Al matrix. The Al-AlN composites fabricated this way exhibited attractive properties, including thermal stability up to 450 °C, high compressive strength, high Young's modulus and low coefficient of thermal expansion. The presence of nanoscaled AlN reduced the thermal conductivity of the composites compared to the high thermal conductivity of Al-AlN composites prepared by metal infiltration techniques.