ISSN:
1434-6036
Keywords:
PACS. 61.44.+p Semi-periodic solids - 61.66.Dk Alloys
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract: The composition, 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. Their space groups are probably oF-Fmm2 and oI-Imm2. Both are B2 vacancy-containing superstructures; unit cell compositions can be expressed approximately as oF-Al36Cu and oI-Al8Cu ( : vacancies). They both exist in twinning variants of the types and . Such twinning modes indicate that these orthorhombic phases are the decomposition products of a high-temperature parent phase 2-Al2Cu3, the atomic structure of which contains pentagonal atomic arrangements. Therefore the oF, oI, and phases are all B2-based approximants corresponding to the Al-Cu-TM quasicrystals.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s100510050522
Permalink