Transmission Electron Microscopy for Precipitate Phases in Rapidly Solidified Mg-2 at%Ce-1 at%Zn and Mg-2 at%Ce Alloys

Abstract

Precipitate phases in Mg-2 at%Ce-1 at%Zn (Mg 97 Ce 2 Zn 1 ) and Mg-2 at%Ce (Mg 98 Ce 2 ) alloys, prepared by a melt-quenching method, have been examined by high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). A precipitate phase formed at grain boundaries has an ordered structure with a hexagonal unit cell of √2a 0 and c 0 , in which a 0 and c 0 are lattice parameters of an h.c.p. structure of the Mg-matrix. On the other hand, a precipitate phase embedded in Mg-matrix grains has a long-period modulated structure formed by the appearance of two-dimensional anti-phase boundaries with a hexagonal symmetry in the fundamental hexagonal structure with lattice constants of √3a 0 and c 0 .