Solid-state reactions in mechanically alloyed Al-V powders

High-energy ball milling has been performed on AlxV1-x powder mixtures in t he Al-rich range of composition (x = 0.61, 0.70, 0.75, 0.85 and 0.90). The structural evolution and the thermal stability of the samples was followed by X-rap diffraction and differential scanning calorimetry. We have observe d that, similar to other Al-transition metal binary systems, the reaction r ate decreases with increasing Al content and that milling promotes diffusio n of both elements into each other; in fact for short times of milling Al(V ) and V(Al) solid solutions have been observed at all investigated composit ions. With the exception of the Al-richest composition, several metastable phases have been observed to nucleate in the early stages of milling. In a broad range of composition around the stoichiometric ratio extended milling promotes the formation of the Al3V intermetallic compound in a heavily str ained nanocrystalline state. Upon heating of pre-milled samples to 360 degr ees C the disappearance of the metastable phases and the formation of a sig nificant amount of the compound Al3V has been observed at every composition and for all investigated milling times. The formation of Al8V5, Al23V4 and Al10V has been observed upon heating to higher temperatures pre-milled sam ples containing 61, 85 and 90 at.% Al.