Effect of magnesium on nitridation and infiltration of aluminum powder

Abstract

We investigated the effect of Mg on the nitridation behavior of Al particles during thermal treatment for a range of Mg contents and temperatures. The addition of Mg stimulates the initiation of nitridation because it diffuses and forms an Al-Mg alloy with a lower melting point than that of pure Al. In the initial stages of the nitridation, nitrides without a perfect crystallographic structure are formed on the surface of Al particles and then AlN with a superlattice structure is formed within the reaction product. Since the Al-Mg powder bed is rapidly densified during heat treatment compared to its pure Al counterpart, the pathways in it for nitrogen diffusion are limited in comparison and further nitridation is much suppressed, resulting in much lower total nitridation compared to a pure Al powder bed. This behavior is observed regardless of the Mg content or the nitridation temperature (up to 900 A degrees C), demonstrated in experiment for Al powder beds containing < 5 wt% Mg.