Platelet precipitate in an age-hardening Mg-Zn-Gd alloy

Highlights: • The structure of a unique platelet precipitate in age-hardening Mg-Zn-Gd alloys has been determined. • Combined use of scanning transmission electron microscopy and first principles calculations. • Unlike the previous report, the zone has a reconstructed ternary Mg-Zn-Gd structure. The structure of a unique platelet precipitate with a three close-packed layer thickness, which occurred in a Mg-1at.%Zn-2at.%Gd alloy aged at low temperatures (c-axis. Therefore, the present platelet precipitate is found to be not a simple ordered hexagonal-close-packed Mg-Gd as previously reported, but a reconstructed ternary Mg-Zn-Gd structure.