期刊
INTERMETALLICS
卷 31, 期 -, 页码 55-64出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.intermet.2012.06.010
关键词
Intermetallics; miscellaneous; Crystallography; Electron microscopy; transmission
资金
- Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan [22656156, 23360306, 23109002]
- Global COE (Center of Excellence) Program of International Center for Integrated Research and Advanced Education in Materials Science from the MEXT, Japan
- Kumamoto Prefecture CREATE project from JST
- Grants-in-Aid for Scientific Research [22656156, 23360306] Funding Source: KAKEN
The crystal structure of a long-period stacking-ordered (LPSO) phase of the 14H-type formed in a Mg-Al-Gd alloy as a local small part in the intergrowth structure together with that of the 18R-type (the majority) has been investigated by scanning transmission and transmission electron microscopy. The LPSO phase of the 14H-type in the Mg-Al-Gd system is found to form by stacking structural blocks, each of which consists of seven close-packed atomic planes. In each of the structural blocks, a long-range ordering occurs for the constituent Mg, Al and Gd atoms with the enrichment of Gd atoms in the four consecutive atomic planes. The in-plane long-range ordering in the four consecutive atomic planes occurs so as to form Al6Gd8 clusters in a periodic manner. This is exactly the same as what is observed in the LPSO phase of the 18R-type. The crystal structure of the 14H-type LPSO phase can thus be described to form simply by adding a Mg layer to the crystal structure of the 18R-type LPSO phase so as to form triple (three consecutive) Mg layers to sandwich the Gd-enriched quadruple layers. The ideal chemical formula of the structural block is Mg35Al3Gd4 (Mg - 7.1 at.% Al - 9.5 at.%Gd). The crystal structure of the LPSO phase can thus be crystallographically described as one of the order-disorder (OD) structures, and the space group of either P6(3)22 or R (3) over barc, is assigned when the simplest stacking of structural blocks is assumed. (C) 2012 Elsevier Ltd. All rights reserved.
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