Three-Dimensional Shapes and Distributions of Long-Period Stacking Ordered Structures in Mg₉₇Zn₁Gd₂ Cast Alloys Characterized by Electron Tomography

Abstract

Three-dimensional (3D) configurations of 14H long-period stacking ordered (LPSO) structures formed in Mg 97 Zn 1 Gd 2 cast alloys at intermediate stages of the formation process have been studied by single tilt-axis electron tomography using high-angle annular dark-field scanning transmission electron microscopy. Lateral morphology of the 14H LPSO is clearly visualized by reconstructing 3D volumes. An existence of "dent-shaped" area was found in a 3D reconstructed volume for the first time. The edge of LPSO shows a characteristic triangular shape with an angle of 60°, which indicates that the growth front is parallel to f11 20g Mg . It is suggested that in-plane irregular or characteristic shapes are related to the lateral growth mechanism of LPSO. Electron tomography has proven to be an indispensable tool to characterize in-plane structural information of LPSO formed in ¡-Mg matrix.

Correlative atom probe tomography and scanning transmission electron microscopy reveal growth sequence of LPSO phase in Mg alloy containing Al and Gd

“…4 a,b, the LPSO/OD phase region seems to have habit planes parallel to either {1 00} or {11 0} planes. This is consistent with the result from electron tomography experiment that lateral growth of the LPSO/OD phase in the Mg–Zn–Gd system occurs with habit planes parallel to either {1 00} or {11 0} planes with some preference of {11 0} 26 . More work is definitely needed to unambiguously determine the growth habit plane (either {1 00} or {11 0} planes) for the LPSO/OD phase in the Mg–Al–Gd system.…”