Short-range structure of Al-Mn and Al-Mn-Si aperiodic alloys

Journal Article · Mon Aug 15 04:00:00 EDT 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.38.3754· OSTI ID:6927347

Ma, Y; Stern, E A

X-ray-absorption fine-structure results on the icosahedral Al-Mn and Al-Mn-Si, ..cap alpha..-(Al-Mn-Si), and decagonal Al-Mn alloys are presented. High-resolution first-shell Al radial distributions around Mn atoms were obtained using a newly developed, direct Fourier-transform method. The first and second Mn shells are analyzed in detail. The Al and Mn positions on the structural unit of the icosahedral phase are determined from these results. The result is in agreement with the speculation that the structural unit is a Mackay icosahedron (MI). Furthermore, it is found that about 40% of the MI units in the icosahedral phase have the same connection as that in ..cap alpha..-(Al-Mn-Si) and the average coordination number of the MI is about 7 in the icosahedral phase. The MI units also closely resemble those in the ..cap alpha.. phase, including the distortion induced by the cubic packing of the MI's in ..cap alpha..-(Al-Mn-Si). These results suggest the presence of a short-range cubic environment in the icosahedral phase with an estimated correlation length of about 20 A. These results are in disagreement with both the completely random accretion of oriented MI units and a quasicrystalline arrangement of the MI. Results on the decagonal Al-Mn phase and the role of Si in icosahedral Al-Mn-Si are also discussed.

• Research Organization: Physics Department, FM-15, University of Washington, Seattle, Washington 98195
• OSTI ID: 6927347
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:6; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ABSORPTION SPECTRA
ALLOYS
ALUMINIUM ALLOYS
COORDINATION NUMBER
CRYSTAL STRUCTURE
FINE STRUCTURE
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
MANGANESE ALLOYS
POWDERS
SILICON ALLOYS
SPECTRA
TRANSFORMATIONS
X-RAY SPECTRA