[SY-K1] System-spanning shear avalanches induced by thermal structural relaxation in metallic glasses
Metallic glasses (MGs) are one of the most attractive materials because of their excellent properties [1]. However, brittle fractures are an obstacle for MGs to be applied as structural materials. This brittleness originating from shear band nucleation is determined by structural relaxation using thermal annealing [2]. Thus, the influence of structural relaxation upon the nucleation of shear banding that can induce catastrophic failure in MGs is a significant challenge in material science.
For this challenge, we focus on the avalanche behavior that provides sudden massive deformations and spatiotemporal correlation in solid plasticity [3]. Thus, this avalanche behavior is deeply connected to the localization of plastic deformation and catastrophic failure in MGs.
In this study [4], we investigate the geometry of the shear transformation avalanches that exhibit the power-law statistics using molecular dynamics simulations of shear deformation in two thermally processed MG models that are based on a less-relaxed glass and a well-relaxed glass. The simulation showed a shear-band like heterogeneous pattern in the well-relaxed glass model, whereas the less-relaxed model exhibits homogeneous deformation patterns. Considering the spatial correlation functions of the non-affine least square displacements of atoms during each each avalanche event, we reveal that the regions an avalanche developed in well-relaxed glasses tend to be anisotropic whereas those in less-relaxed glasses are isotropic. Moreover, a temporal clustering feature of the direction of avalanche propagations and a considerable correlation between the anisotropy and size of an avalanche in the well-relaxed glass model are demonstrated.
[1] A. L. Greer, Science 267, 1947 (1995).
[2] G. Kumar, et al., Acta Mater. 57, 3572 (2009).
[3] M. C. Miguel, et al., Nature 410, 667 (2001).
[4] T. Niiyama, et al., arXiv:1804.00852 (2108).
For this challenge, we focus on the avalanche behavior that provides sudden massive deformations and spatiotemporal correlation in solid plasticity [3]. Thus, this avalanche behavior is deeply connected to the localization of plastic deformation and catastrophic failure in MGs.
In this study [4], we investigate the geometry of the shear transformation avalanches that exhibit the power-law statistics using molecular dynamics simulations of shear deformation in two thermally processed MG models that are based on a less-relaxed glass and a well-relaxed glass. The simulation showed a shear-band like heterogeneous pattern in the well-relaxed glass model, whereas the less-relaxed model exhibits homogeneous deformation patterns. Considering the spatial correlation functions of the non-affine least square displacements of atoms during each each avalanche event, we reveal that the regions an avalanche developed in well-relaxed glasses tend to be anisotropic whereas those in less-relaxed glasses are isotropic. Moreover, a temporal clustering feature of the direction of avalanche propagations and a considerable correlation between the anisotropy and size of an avalanche in the well-relaxed glass model are demonstrated.
[1] A. L. Greer, Science 267, 1947 (1995).
[2] G. Kumar, et al., Acta Mater. 57, 3572 (2009).
[3] M. C. Miguel, et al., Nature 410, 667 (2001).
[4] T. Niiyama, et al., arXiv:1804.00852 (2108).