Effects of fabrication condition on the formation of A1N by means of gas/melt in-situ reactions were investigated through injection of mixture gas of 95% N₂＋5%H₂into the commercial grade A5083 alloys. In this investigation, the fabrication was performed in the temperature range of 1000 to 1200℃ for up to 4 hours. The fabricated composites were characterized using X-ray diffraction, scanning electron microscopy with dispersive X-ray microanalysis and transmission electron microscopy. The volume fraction of MN formed in the specimens increased with increasing reaction time and reaction temperature as well, while the trend of increment of volume fraction of AIN per hour is different with the reaction temperature. The formation of A1N by means of gas/melt in-situ reactions was examined through the thermodynamic and kinetic considerations.