NANOCRYSTALLINE AL-FE ALLOYS SYNTHESIZED BY HIGH-ENERGY BALL-MILLING

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 71, 75, 80 and 90 at.% Al. In the 71 and 75 at. % Al mixtures we observed the formation of the Al5Fe2 phase. At the 80 at.% Al concentration we observed the formation of an Al-rich ultrafi ne phase with a coherent domain size of the order of 1 nm. At the 90 a t.% Al concentration, no new phase is observed to nucleate for milling times up to 50 hs. The thermal behaviour of the samples depends on th e time of the milling. At all compositions, we observed the nucleation of the metastable Al6Fe compound at about 320 degrees C on heating of samples milled for short times (10 h or less) and the formation of th e equilibrium phase(s) upon heating to 600 degrees C.