Characterization of beta' precipitate phase in Mg-2 at% Y alloy aged to peak hardness condition by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM)

The beta' phase precipitated in an Mg-2 at%Y (Mg98Y2) alloy aged to a peak hardness condition at 200 degrees C for 336 h has been studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The beta' precipitates have an about 20 nm size and definite facets parallel to the (010) plane, and Y-enriched double atom planes parallel to the (010) plane grow long and sometimes individually along the [100] and [001] directions. This morphology of the beta' precipitates in the Mg98Y2 alloy is remarkably different from that in an M95Gd5 alloy.