Sluggish dynamics in Al-containing metallic glass-forming melts

Abstract

Microalloying is an effective approach to improve the macroscopic properties of alloys. For understanding the microalloying effect on the dynamic behavior of metallic glass-forming systems, the impact of alloying the metalloid-like element Al on the melt viscosity of the Zr72-xCo28Alx (x = 4,8,16,24) alloys has been investigated utilizing the electrostatic levitation technique. Single-particle dynamics and atomic structure were also analyzed based on ab initio molecular-dynamics simulations. We identified orbital hybridization effects between Al and transition metal elements as the primary origin of the sluggish dynamics of the Zr-Co-Al melts upon Al addition, along with a weak decoupling of the diffusive dynamics, particularly at the composition Zr56Co28Al16. The composition dependent melt viscosity and the liquid fragility promote the glass formation, while the optimal glass forming ability cannot be solely understood by the contribution of the liquid dynamics. This work might shed new light on the influence of minor additions in alloy melts from the electronic structure viewpoint, which could help us to develop novel multicomponent amorphous materials, especially metallic glasses with excellent performance.