Study on a novel orientation domain of Mg17Ce2 in aged Mg-Y-Ce alloy by HAADF-STEM

摘要

After solid solution and aging treatment, Mg-3.0 wt%Y-1.0 wt%Ce ternary alloys were characterized using high angle annular dark field scanning transmission electron microscopy. The main precipitates are dominated by beta phase and Mg17Ce2, a Ni17Th2-type intermetallic compound. An orientation domain can be discerned generally in Mg17Ce2 granules. This domain structure of Mg17Ce2 always consists of two types of domains (defined as domain I and domain II) with a 90 degree orientation difference. In terms of crystallographic orientation relationships among alpha-Mg matrix and both domains, the domain I is parallel to alpha-Mg matrix, whereas, the domain-II is perpendicular to alpha-Mg matrix. It can be certain that a (1010) direction is an unchanged orientation. Due to nearly equal values of lattice parameters (a and c) of Mg17Ce2, both domain-I and domain-II can matches well with alpha-Mg matrix. Comparatively, the interfacial matching between domain-I and alpha-Mg matrix is better, suggesting that the domain-I is dominant.

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