Clustering-mediated enhancement of glass-forming ability and plasticity in oxygen-minor-alloyed Zr-Cu metallic glasses

A better metallic glass (MG) is usually more brittle as if there exists a tradeoff between glass-forming ability (GFA) and plasticity. However, recent experiments show that GFA and plasticity can be simultaneously enhanced via minor addition of oxygen into a Zr-Cu-based MG, a previously thought harmful element. In this work, using molecular dynamics (MD) simulations, we reveal that finely dispersed O-centered clusters (OCCs), being structurally compact and energetically stable at the both liquid and glass states, are responsible for the concurrent enhancement of GFA and plasticity in Zr-Cu MGs. The OCCs promote structural and dynamical heterogeneities in the supercooled liquid, leading to an enhanced GFA. Meanwhile, the densely packed OCCs collaborate with their loosely packed surroundings, amplifying structural fluctuations, facilitating formation of shear-transformation zones and thus enhancing plastic deformation. This work not only deepens the mechanistic understanding of glass formation and deformation behaviors of MGs, but also has important implications for developing low-cost MGs with low-grade raw materials containing oxygen.