Glass-to-liquid transition in zirconium and palladium based metallic glasses

In metallic glasses, the presence of the glass-to-liquid transition upon heating is a measure for evaluating thermal or structural stability against crystallization. In some less-stable metallic glasses, the crystallization precedes the glass transition, while the distinct glass transition is observed prior to crystallization for some stable metallic glasses. This feature seems to be exceptional for metallic glasses and rarely observed for other kinds of glass materials, e.g., covalently bonded glasses. In this paper, focusing on this intriguing feature of metallic glasses, we investigate the glass-to-liquid transition of Zr₇₀ Ni₃₀, Zr₇₀ Cu₃₀, and Pd_42.5 Ni_7.5 Cu₃₀ P₂₀ (numbers indicate at.%) metallic glasses for varying the heating rate β in differential scanning calorimetry. Although in Zr₇₀ Ni₃₀ metallic glass, the glass-to-liquid transition is not detected for ordinary heating rates, sufficiently rapid heating exposes the glass-to-liquid transition by suppressing crystallization. Whereas two fitted curves for glass transition temperature, T_g and crystallization temperature, T_x against log β intersect at a quite small β for Pd_42.5 Ni_7.5 Cu₃₀ P₂₀, their intersection occurs at a relatively large β for Zr₇₀ Cu₃₀ or Zr₇₀ Ni₃₀. The value of β at the intersection apparently reflects the thermal stability of metallic glasses.