Structural Signature of Plastic Deformation in Metallic Glasses

The structure feature of a model CuZr metallic glass during deformation is investigated by molecular dynamics simulations. A spatially heterogeneous irreversible rearrangement is observed in terms of nonaffine displacement. We find that regions with smaller nonaffine displacement have more Voronoi pentagons, while in those with larger nonaffine displacement other types of faces are more populated. We use the degree of local fivefold symmetry (LFFS) as the structural indicator to predict plastic deformation of local structures and find that the plastic events prefer to be initiated in regions with a lower degree of LFFS and propagate toward regions with a higher degree of LFFS.

Figure 1

Atomistic configurations of the nonaffine displacement of $D^2$ illustrated by colors at the strain of 5% when $\Delta t=10\mathrm{ps}$ (a) and $\Delta t=40\mathrm{ps}$ (b).

Figure 2

(a) The correlation between the nonaffine displacements and the fraction of $i$-edged faces in polyhedra. (b) The correlation of the nonaffine displacements with the common-neighbor types and their fractions.

Figure 3

(a) The variation of the average $d_5$ with strain; (b) the distribution of the average $d_5$ with the nonaffine displacement.

Figure 4

Correlation between the structures having a higher degree of LFFS and the irreversible rearrangement during deformation. The slice in the middle of the samples along $Z$ direction with thickness of the first minimum of the pair correlation function was taken for the illustration. Black points denote the atoms having a higher degree of LFFS ($d_5\ge 0.5$) at the strain of (a) 5% and (b) 10%. The colors represent values of $D^2$ with $\Delta t=40\mathrm{ps}$.

Figure 5

Correlation between the yield stress and averaged $d_5$ measured with different cooling rates (CR).