Revealing the nucleation event of Mg-Al alloy induced by Fe impurity

Abstract

This study revealed the nucleation event and grain refinement mechanism of Mg-Al alloy induced by Fe impurity. The following orientation relationship was observed between Al-Fe particle and α-Mg matrix in the Mg-3Al alloy containing Fe impurity using a focused ion beam aided transmission electron microscope technique: $(\bar 1011){[01\bar 11]_{{\rm{Mg}}}}//(01\bar 1){[011]_{{\rm{A}}{{\rm{l}}_2}{\rm{Fe}}}}$. Mg-3Al alloy was inoculated by adding 0.02wt% Fe to verify the nucleating potency of the Al₂Fe phase for α-Mg grain. The results indicated that Mg-3Al alloy was effectively refined with an average grain size declining from 1135 to 540 µm. Among the potential Al-Fe phases of Mg-3Al-0.02Fe alloy, only the precipitation of the Al₂Fe phase occurs earlier than that of α-Mg grain, and the Al₂Fe phase is stable in the nucleation stage of α-Mg grain. Therefore, the Al₂Fe particle is the only available nucleating site for Mg-Al alloy with Fe impurity. The heterogeneous nucleation event of α-Mg grain on the Al₂Fe particle is responsible for the grain refinement of Mg-3Al alloy inoculated by Fe.

Keywords

grain refinement / Mg-Al alloy / Al-Fe particle / heterogeneous nucleation

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