Synthesis of nanocrystalline iron aluminides by mechanical alloying

This study describes the effect of ball milling and heat treatment on the phases synthesized in a SPEX mill starting from mixtures of Al and Fe powders containing 75 and 80 at.% Al. Upon milling of the 75% Al mixture we have observed the formation of the Al5Fe2 phase. At the 80% Al composition we have observed the formation of an Al-rich ultrafine phase with a size of the coherent domains of the order of 1 nm. The thermal behaviour of the samples depends on the time of milling. Upon heating of samples milled for short times we have observed at both compositions the nucleation of the metastable Al6Fe compound at about 320 degrees C. At the 75% Al composition the Al5Fe2 compound has been observed to nucleate at about 380 degrees C in those samples where it had not formed during milling. Finally, the nucleation of Al3Fe was observed only at the 80% Al composition in the samples heated above 450 degrees C.