Order Effect of Vacuum and Ammonia Atmospheres on Aluminium Nitriding by Mechanical Alloying

Aluminium powder was milled under vacuum and/or ammonia atmospheres, in order to evaluate the effect of the order of the atmospheres on the amount of nitrides appearing in the powder after a subsequent heat treatment. All milling experiences were carried out at room temperature for 5 h. The XRD study of sintered powders showed that important amounts of AlN appeared after heating. The use of vacuum and ammonia flow allows controlling the percentage of N rich phases formed. Moreover, the capacity of incorporating nitrogen to the aluminium lattice is very influenced by the vacuum and ammonia flow atmospheres order during the milling process.