Zinc (blue) and magnesium (red) centred clusters formed by the close packing of calcium atoms
(green) in the Ca60Mg20Zn20 glass.
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Bulk metallic glasses have unique properties which offer potential developments for a wide range of technological applications.
CaMgZn glasses have extremely good glass-forming ability, whilst exhibiting low densities (1.6 – 2.4 g/cm3) and extremely low Young’s (~20-30 GPa) and shear (~9-14 GPa) moduli. Relating the structural characteristics of these glasses to their physical properties will allow the design of new materials for specific applications. We have used neutron and X-ray diffraction, combined with Reverse Monte Carlo and ab initio molecular dynamics modelling. We find that those CaMgZn glasses which form easily have zinc- and magnesium-centred clusters, around which calcium atoms are packed efficiently to give high coordination numbers. As the composition of the glass is altered, the arrangement of the atoms in the clusters changes dramatically. A decrease in the glass-forming ability is linked to the formation of clusters similar to those found in Ca2Cu crystals, as well as to an increase in Zn-Zn clustering.
ON Senkov, DB Miracle (Air Force Research Laboratory), YQ Cheng, E Ma (John Hopkins University), ER Barney, and AC Hannon (ISIS)
Research date: November 2008
Contact: Dr ON Senkov, email@example.com
Further information: ON Senkov et al., Phys Rev B 82 (2010) 104206
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