On a γ′′ plate with a tri-layer structure in aged Mg–Ce–Ca ternary alloys

Abstract

• A Mg 2 Ca 3 Ce- γ ″ basal plate can form in the aged Mg–Ce–Ca alloy. • The γ ″ basal plate contains three atomic layers along the 0001 α direction. • There is a relatively small misfit between γ ″ plate and matrix along 0001 α . For the γ ″ precipitate in rare earth magnesium alloys , there are still some discrepancies on its structure and morphology. In this work, the microstructure of an aged Mg–Ce–Ca alloy is studied by atomic scale scanning transmission electron microscopy . It is confirmed that the γ ″ basal plate with three atomic layers has a Mg 2 Ca 3 Ce composition and a hexagonal structure (space group P 6 ¯ 2 m , a = 0.560 nm and c = 0.482 nm). There is a relatively small misfit between γ ″ and matrix along the 0001 α direction. Meanwhile, the correlations between the structure of the γ ″ and the average atomic radius are also discussed particularly.