Icosahedron-dominated tension–compression asymmetry and brittle–ductile transition of metallic glass

Abstract

Molecular dynamics simulation was used to study the tension–compression asymmetry and brittle–ductile transition of Ni–Al metallic glass. We found the cooling rate has little influence on its tension–compression asymmetry. Their mechanical properties depend on the components. When the content of Al element is high, the low content of icosahedral clusters leads to poor mechanical properties. Meanwhile, the tension–compression asymmetry is more obvious with the high aspect ratio, which is positively correlated with the content of icosahedral clusters. Compared with aspect ratio, cooling rate and composition have little effect on brittle–ductile transition. The icosahedral clusters transform from low to high symmetry under tensile and compressive loads, accompanied by irreversible atomic rearrangements near the shear bands, leading to limited plasticity. The rejuvenation rate of icosahedral clusters is faster in metallic glasses with high aspect ratio, leading to brittle fracture, which is the mechanism of brittle–ductile transition behavior of metallic glasses.