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Al-Cu approximants and associated B2 chemical-twinning modes
MedLine Citation:
PMID:  10831295     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The Al3Cu4 alloy, with an e/a ratio of 1.86 being close to ternary Al-Cu-TM (transition metal) quasicrystals, has been chosen for the search of Al-Cu approximants. Phase structures and compositions were studied using TEM, X-ray diffraction and EPMA techniques. Two new phases were found: face-centered orthorhombic oF-Al43.2Cu56.8 (a = 0.816(6), b = 1.414(9), c = 0.999(5) nm) and body-centered orthorhombic oI-Al41.3Cu58.7 (oI, a = 0.408(3), b = 0.707(4), c = 0.999(5) nm). Their e/a ratios are the same as that of the Al-Cu-Fe icosahedral quasicrystal. Both are B2 superstructures and their unit cell components can be expressed approximately as oF-Al36Cu48vacancies12 and oI-Al8Cu12vacancies4. They both exist in twinning variants of the types 120 degrees/[001] and 180 degrees/[310]. Such twinning modes indicate that these orthorhombic phases are the decomposition products of a high-temperature parent phase epsilon2-Al2Cu3, the atomic structure of which shows pentagonal atomic arrangements. Further analysis on the twinning modes of oF and oI leads to the recognition of the chemical-twinning mode of the basic B2 structure as 180 degrees/(111)B2. This kind of chemical twinning mode is responsible for the pentagonal atomic configuration in the Al-Cu approximants as well as for the pseudo-5-fold B2 twinning.
Authors:
Dong; Zhang; Wang; Wang
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Publication Detail:
Type:  JOURNAL ARTICLE    
Journal Detail:
Title:  Micron (Oxford, England : 1993)     Volume:  31     ISSN:  1878-4291     ISO Abbreviation:  Micron     Publication Date:  2000 Oct 
Date Detail:
Created Date:  2000-05-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9312850     Medline TA:  Micron     Country:  ENGLAND    
Other Details:
Languages:  Eng     Pagination:  507-14     Citation Subset:  -    
Affiliation:
State Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Dalian University Technology, People's Republic of China. dong@dlut.edu.cn
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