IN-SITU FORMATION OF AlN REINFORCED Al ALLOY COMPOSITES USING AMMONIA

摘要

In-situ formation of Al alloy matrix composites was investigated. The synthesis of Al alloy matrix composites reinforced with in-situ formed AlN particles was achieved in the temperature range of 1273-1473K by directly bubbling ammonia (NH_3) through an Al alloy melt. Products were characterized using X-ray diffraction, optical microscopy, SEM, and EDS analyses. Thermodynamic analysis of Al-Si-N ternary system was carried out using Gibbs energy minimization method and its phase diagram at 1473K was calculated. The results showed that the AlN content in the composites is up to 27.4 wt% and AlN particles are uniformly dispersed in the Al-alloy matrix. Formed AlN particles are non-spherical and small in size. The results also indicated that AlN reinforcement is thermodynamically stable in Al and Al-Si alloy matrix over a wide temperature range.