Composition-Dependent Effects of Oxygen on Atomic Structure and Mechanical Property of Metallic Glasses

Abstract

Although minor alloying in metallic glasses (MGs) has been extensively investigated, the effect of O doping is still a debatable topic. In the present study, the atomic-level structures and mechanical properties of Cu-Zr MGs doped with different O contents have been analyzed using ab initio molecular dynamics simulations. It is found that O atoms prefer to bond with Zr atoms due to their low mixture enthalpy. The key finding is that we reveal the compositional dependence of O doping. For O-doped Cu64Zr36 MGs, the fraction of full icosahedra, size of the medium-range-order clusters, Young’s modulus, and shear modulus decrease sharply with O content, accompanied by a sharp increase of the non-Frank-Kasper polyhedral, ratio of bulk modulus to shear modulus, and Poisson's ratio, indicating decreased strength and improved plasticity. For O-doped Cu47Zr53 MGs, however, the above-mentioned structural and mechanical features experience little change or only change slowly after O doping, showing low oxygen sensitivity. It is reasoned that the high Zr content in Cu47Zr53 MGs weakens the effect of Zr-O bonding to some extent. The present study not only sheds light on the atomic-level structures of O-doped MGs that may provide guidelines for designing MGs with low-grade materials and low processing cost, but also help to explain the previous conflicting results based on the composition-dependence effect.