Suppression of Shear Banding and Transition to Necking and Homogeneous Flow in Nanoglass Nanopillars

Abstract

In order to improve the properties of metallic glasses (MG) a new type of MG structure, composed of nanoscale grains, referred to as nanoglass (NG), has been recently proposed. Here, we use large-scale molecular dynamics (MD) simulations of tensile loading to investigate the deformation and failure mechanisms of Cu64Zr36 NG nanopillars with large, experimentally accessible, 50 nm diameter. Our results reveal NG ductility and failure by necking below the average glassy grain size of 20 nm, in contrast to brittle failure by shear band propagation in MG nanopillars. Moreover, the results predict substantially larger ductility in NG nanopillars compared with previous predictions of MD simulations of bulk NG models with columnar grains. The results, in excellent agreement with experimental data, highlight the substantial enhancement of plasticity induced in experimentally relevant MG samples by the use of nanoglass architectures and point out to exciting novel applications of these materials.

Nanoglass‐based balloon expandable stents

“…These results demonstrate that the NG nanostructure constrains the generation and propagation of a dominant shear band and promotes delocalization of the plastic deformation, effectively inducing a transition in failure mode, enhancing the overall ductility as well as the toughness of MGs. Here, it is noteworthy that using similar MD simulation framework, we have successfully investigated the structure–property relations is a wide range of MGs and nanoglasses in good agreement with experiments . The proper setup of boundary conditions in our MD simulations enables us to reproduce the mechanical behavior of the MGs and nanoglasses in the bulk, for example, their deformation and failure mechanisms, similar to those in experiments .…”

“…Here, it is noteworthy that using similar MD simulation framework, we have successfully investigated the structure-property relations is a wide range of MGs and nanoglasses in good agreement with experiments. 53,[57][58][59][60][61][62] The proper setup of boundary conditions in our MD simulations enables us to reproduce the mechanical behavior of the MGs and nanoglasses in the bulk, for example, their deformation and failure mechanisms, similar to those in experiments. 36,52,53,[63][64][65] Then, as a "multiphysics" modeling scheme, [66][67][68] we have used these information, for example, Young modulus, and so forth, to build the constitutive relationships for our FEM simulations.…”

Sample size effects on strength and deformation mechanism of Sc75Fe25 nanoglass and metallic glass

“…Plastic flow then will take place in other sites, resulting in significant global plastic strain (Fig.4c). As a consequence, the existence of a large number of GGIs in the nanoglass benefits for the nucleation and the subsequent multiplication of shear bands while the metallic glass is shear band nucleation starved in samples of small sizes [4,[30][31][32]. As is observed above in the experimental section, the transition of deformation mode in nanoglasses might occur at a smaller size scale (~ 100 nm).…”

Interfacial plasticity governs strain delocalization in metallic nanoglasses

“…This cross-over transpired at a finer amorphous grain size of 5 nm for the Voronoi-tessellated columnar nanoglass model [27,28] and was explained in the context of the rapid decrease in atom fraction composing the interfaces with increasing grain size [21] (though this rationale applies to both nanoglass models). Insights into the pursuit of tensile ductility from nanoglass pillar simulations containing free surfaces have also suggested that finer amorphous grain sizes promote a more homogenous plastic response, which inhibits necking instabilities deriving from shear localization prevalent at larger grain sizes [29].…”