Mechanical alloying of Nb-Al powders

The effect of mechanical alloying (MA) on solid solubility extension, nanostructure formation, amorphization, intermetallic compound formation, and the occurrence of a face-centered cubic (fcc) phase in the Nb-Al system has been studied. Solid solubility extension was observed in both the terminal compositions and intermetallic compounds: 15 pct Nb in Al and 60 pet Al in Nb, well beyond the equilibrium and even rapid solidification levels (2.4 pct Nb and 25 pct Al, respectively) and increased homogeneity range for the NbAl3 phase. Nanostructured grains formed in all compositions. In the central part of the phase diagram, amorphization occurred predominantly. Only NbAl3, the most stable intermetallic, formed during MA; in most cases, a subsequent anneal was required. On long milling time, an fcc phase, probably a nitride, formed as a result of contamination from the ambient atmosphere.