Characterization of β' 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)

摘要

The β' phase precipitated in an Mg-2 at%Y (Mg{sub}98 Y{sub}2) alloy aged to a peak hardness condition at 200℃ for 336 h has been studied by high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The β' 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 β' precipitates in the Mg{sub}98Y{sub}2 alloy is remarkably different from that in an Mg{sub}95Gd{sub}5 alloy.