Complex metallic alloys

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Complex metallic alloys (CMAs) or complex intermetallics (CIMs) are intermetallic compounds characterized by the following structural features:[citation needed]

  1. large unit cells, comprising some tens up to thousands of atoms,
  2. the presence of well-defined atom clusters, frequently of icosahedral point group symmetry,
  3. the occurrence of inherent disorder in the ideal structure.

Overview[]

Complex metallic alloys is an umbrella term for intermetallic compounds with a relatively large unit cell. There is no precise definition of how large the unit cell of a complex metallic alloy has to be, but the broadest definition includes Zintl phases, Skutterudites, and Heusler compounds on the most simple end, and quasicrystals on the more complex end.[1]

Research[]

Following the invention of X-ray crystallography techniques in the 1910s, the atomic structure of many compounds were investigated. Most metals have relatively simple structures. However, in a 1923 Linus Pauling reported on the structure of the intermetallic NaCd2, which had such a complicated structure he was unable to fully explain it.[2] Thirty years later, he concluded that NaCd2 contained 384 sodium and 768 cadmium atoms in each unit cell.[3]

Most physical properties of CMAs show distinct differences with respect to the behaviour of normal metallic alloys and therefore these materials possess a high potential for technological application.

The European Commission funded the Network of Excellence CMA [1] from 2005 to 2010, uniting 19 core groups in 12 countries. From this emerged the European Integrated Center for the Development of New Metallic Alloys and Compounds C-MAC [2], which connects researchers at 21 universities.

Examples[]

Example phases are:

  • β-Mg2Al3: 1168 atoms per unit cell, face centred cubic, atoms arranged in Friauf polyhedra.[4]
  • ξ'–Al74Pd22Mn4: 318 atoms per unit cell, face centred orthorhombic, atoms arranged in Mackay-type clusters.[5]
  • Mg32(Al,Zn)49 (Bergman phase): 163 atoms per unit cell, body centred cubic, atoms arranged in Bergman clusters.[6]
  • Al3Mn (Taylor phase): 204 atoms per unit cell, face centred orthorhombic, atoms arranged in Mackay-type clusters.[7][8]

See also[]

References[]

  1. ^ Dubois, Jean-Marie; Belin-Ferré, Esther, eds. (2011). Complex Metallic Alloys: Fundamentals and Applications. Wiley-VCH. doi:10.1002/9783527632718. ISBN 978-3-527-32523-8.
  2. ^ Pauling, Linus (1923). "The Crystal Structure of Magnesium Stannide". Journal of the American Chemical Society. American Chemical Society (ACS). 45 (12): 2777–2780. doi:10.1021/ja01665a001. ISSN 0002-7863.
  3. ^ Pauling, Linus (1955). "The Stochastic Method and the Structure of Proteins". American Scientist. 43 (2): 285–297. JSTOR 27826614.
  4. ^ Samson, S. (1965-09-01). "The crsytal structure of the phase β Mg2Al3". Acta Crystallographica. International Union of Crystallography (IUCr). 19 (3): 401–413. doi:10.1107/s0365110x65005133. ISSN 0365-110X.
  5. ^ Boudard, M.; Klein, H.; Boissieu, M. De; Audier, M.; Vincent, H. (1996). "Structure of quasicrystalline approximant phase in the Al-Pd-Mn system". Philosophical Magazine A. Informa UK Limited. 74 (4): 939–956. doi:10.1080/01418619608242169. ISSN 0141-8610.
  6. ^ Smontara, A.; Smiljanić, I.; Bilušić, A.; Jagličić, Z.; Klanjšek, M.; Roitsch, S.; Dolinšek, J.; Feuerbacher, M. (2007). "Electrical, magnetic, thermal and thermoelectric properties of the "Bergman phase" Mg32(Al,Zn)49 complex metallic alloy". Journal of Alloys and Compounds. Elsevier BV. 430 (1–2): 29–38. doi:10.1016/j.jallcom.2006.05.026. ISSN 0925-8388.
  7. ^ Taylor, M. A. (1961-01-10). "The space group of MnAl3". Acta Crystallographica. International Union of Crystallography (IUCr). 14 (1): 84–84. doi:10.1107/s0365110x61000346. ISSN 0365-110X.
  8. ^ Hiraga, K.; Kaneko, M.; Matsuo, Y.; Hashimoto, S. (1993). "The structure of Al3Mn: Close relationship to decagonal quasicrystais". Philosophical Magazine B. Informa UK Limited. 67 (2): 193–205. doi:10.1080/13642819308207867. ISSN 1364-2812.

Further reading[]

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