Glass-liquid transition in a less-stable metallic glass

Abstract

A stable metallic glass, SMG, is often viewed as an amorphous alloy exhibiting a reversible $\text{glass}\ensuremath{\leftrightarrow}\text{liquid}$ transition. Here we show experimentally that even in a less-stable metallic glass, LMG, which is prepared only by rapid melt quenching and promptly crystallized without glass transition at the ordinary heating rate, sufficiently rapid heating exposes the $\text{glass}\ensuremath{\rightarrow}\text{liquid}$ transition by suppressing crystallization. The experimental glass transition ${T}_{\mathrm{g}}$ and crystallization ${T}_{x}$ temperatures were plotted as a function of heating rate $\ensuremath{\beta}$, for ${\mathrm{Pd}}_{42.5}{\mathrm{Ni}}_{7.5}{\mathrm{Cu}}_{30}{\mathrm{P}}_{20}$ of SMG and for ${\mathrm{Zr}}_{70}{\mathrm{Ni}}_{30}$ of LMG. Two extrapolated curves, ${T}_{g}\ensuremath{-}\mathrm{log}\phantom{\rule{0.2em}{0ex}}\ensuremath{\beta}$ and ${T}_{x}\ensuremath{-}\mathrm{log}\phantom{\rule{0.2em}{0ex}}\ensuremath{\beta}$, intersect at a quite small $\ensuremath{\beta}$, e.g., $\ensuremath{\sim}{10}^{\ensuremath{-}4}\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}∕\mathrm{min}$, for SMG, whereas their intersection occurs at a large $\ensuremath{\beta}$, e.g., $\ensuremath{\sim}10\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}∕\mathrm{min}$, for LMG. Such a large $\ensuremath{\beta}$ that is comparable to conventional heating rates makes it difficult to observe the reversible glass transition in LMG, and reflects low thermal stability of the glassy state.