Elastic Moduli Inheritance and the Weakest Link in Bulk Metallic Glasses

We show that a variety of bulk metallic glasses (BMGs) inherit their Young’s modulus and shear modulus from the solvent components. This is attributed to preferential straining of locally solvent-rich configurations among tightly bonded atomic clusters, which constitute the weakest link in an amorphous structure. This aspect of inhomogeneous deformation, also revealed by our in situ neutron diffraction studies of an elastically deformed BMG, suggests a rubberlike viscoelastic behavior due to a hierarchy of atomic bonds in BMGs.

Figure 1

(a) The longitudinal structure factor $S(q)$ under a compressive stress of 10, 500, 1000, and 1500 MPa, respectively. (b) Difference plot of $S(q)\mathrm{\text{−}}s$, between 10 MPa and higher stress levels.

Figure 2

(a) A ${\chi }^2$-type functional $\Delta [\epsilon ,q]$ between two $S(q)\mathrm{\text{−}}s$ corresponding to stresses of 10 and 1500 MPa, as a function of $\epsilon$ and $q$, showing the $q$-dependent strains. Letters ($A–F$) point to local minima. (b) Decomposition of the structure factor obtained under the initial loading condition into the strain-sensitive and strain-insensitive partials.

Figure 3

Schematic illustration of a hypothetical amorphous structure showing local packing of solvent atoms ($A$), solute-centered clusters ($B$) and superclusters ($C$) in a metallic glass. The gray color in $B$ and $C$ denotes the outmost atomic shell filled with a majority of solvent atoms. The dark spot in $B$ represents the solute atom of a solute-centered cluster, while the dark area in $C$ represents the inner solute-enriched region within a supercluster.