ALN DISPERSED REINFORCED ALUMINUM COMPOSITE

In this paper the first results are presented on nitriding of aluminiu m powder and the fabrication of Al-AlN composites after milling and ho t-pressing. Nitriding appears to follow a complex process. High energe tic milling of these powders is an important factor in obtaining homog eneous materials with AlN nanometric grains. TEM and EDX nanoanalyses have shown that Al grains are surrounded by AlN nanocrystals, with som e Al2O3 needles and AlON crystals. Physical properties - thermal expan sion, thermal conductivity, electrical conductivity, hardness, Young's modulus, fracture strength - of these composites change with the AlN content, and the values for 0 vol.% AlN (process powders) always corre spond to higher or lower values than for pure Al (unprocessed powders) , reflecting the fact that processing introduces impurities. A compari son of composites fabricated from composite powders and fr om a mixtur e of Al-AlN commercially available powders is interesting. Generally t hese new composites exhibit better properties than those for Al-SiC or Al-Al2O3 composites with an apparently similar reinforcement content. (C) 1997 Elsevier Science Limited.