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Synchrotron X-ray and neutron investigation of the structure and thermal expansion of the monoclinic Al13Cr2 phase

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journal contribution
posted on 08.01.2019 by Enzo Liotti, Caroline Kirk, I. Todd, K.S. Knight, Simon Hogg
The crystal structure of the Al13Cr2 intermetallic phase at 298 K was studied by synchrotron X-ray and neutron diffraction through the analysis of data collected on bulk samples, one in the as-cast condition, one after annealing at 773 K for 24 h and one for 168 h. Furthermore the thermal expansion behaviour of the structure was investigated for the first time in-situ up to 773 K. The diffraction patterns were analysed using whole pattern fitting techniques using the Le Bail and Pawley methods as well as the Rietveld method. The structure was found to be monoclinic with space group C2/m and lattice parameters a = 25.3101 Å, b = 7.6081 Å, c = 10.9689 Å and β = 128.704∘ at 298 K in the as-cast condition. From the temperature variation of the unit cell parameters the principal axes of the thermal expansion tensor were calculated. The largest principal axis has a magnitude of 1.66 × 10−5 K−1 and lies parallel to b, the second largest lies in the a-c plane at an angle of 37° from c in the direction of -a with a value 1.64 × 10−5 K−1 whereas the smallest lies at 53° to c in the direction of +a and has a value of 1.31 × 10−5 K−1. Analysis of the behaviour of the icosahedra revealed that their expansion is highly anisotropic and the level of anisotropy is related to the point symmetry of the central Cr atoms.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Journal of Alloys and Compounds

Volume

781

Pages

1198-1208

Citation

LIOTTI, E. ... et al, 2018. Synchrotron X-ray and neutron investigation of the structure and thermal expansion of the monoclinic Al13Cr2 phase. Journal of Alloys and Compounds, 781, pp.1198-1208.

Publisher

© Elsevier

Version

AM (Accepted Manuscript)

Publisher statement

This paper was accepted for publication in the journal Journal of Alloys and Compounds and the definitive published version is available at https://doi.org/10.1016/j.jallcom.2018.12.132

Acceptance date

08/12/2018

Publication date

2018-12-11

Copyright date

2019

ISSN

0925-8388

Language

en

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