Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses (MGs). However, for the MGs quenched from different melt temperatures with a quartz tube, the underlying physical origin responsible for the variation of properties remains poorly understood. In the present work, we systematically studied the influence of melt treatment on the thermal properties of a Zr₅₀Cu₃₆Al₁₄ glass-forming alloy and unveiled the microscopic origins. Specifically, we quenched the melt at different temperatures ranging from 1.1T_l to 1.5T_l (T_l is the liquidus temperature) to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating. We found that glass transition temperature, T_g, increases by as much as 36 K, and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5T_l. The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys. The incorporated oxygen and silicon can both enhance the interactions between atoms, which renders the cooperative rearrangements of atoms difficult, and thus enhances the kinetic stability of the MGs.