Implications of elastic constants, fragility, and bonding on permanent deformation in metallic glass

Ratios of elastic constants C-12/C-11 and C-44/C-11 are compared for a representative group of bulk metallic glasses (BMGs) via a Blackman diagram [M. Blackman, Proc. R. Soc. London, Ser. A 164, 62 (1938)]. By the application of bounding limits to the elastic data, with respect to the Born mechanical-instability criterion and the extent of deviation from zero Cauchy pressure, a physical picture emerges of the required structural nature of a BMG if plasticity is to be prevalent, suggesting the need for a large kinetic glass fragility index m as well as nondirectional interatomic bonds. (C) 2011 American Institute of Physics. [doi:10.1063/1.3540652]