Liquid–liquid transition in a strong bulk metallic glass-forming liquid

Abstract

Polymorphic phase transitions are common in crystalline solids. Recent studies suggest that phase transitions may also exist between two liquid forms with different entropy and structure. Such a liquid-liquid transition has been investigated in various substances including water, Al 2 O 3 -Y 2 O 3 and network glass formers. However, the nature of liquid-liquid transition is debated due to experimental difficulties in avoiding crystallization and/or measuring at high temperatures/pressures. Here we report the thermodynamic and structural evidence of a temperature-induced weak first-order liquid-liquid transition in a bulk metallic glassforming system Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 characterized by non-(or weak) directional bonds. Our experimental results suggest that the local structural changes during the transition induce the drastic viscosity changes without a detectable density anomaly. These changes are correlated with a heat capacity maximum in the liquid. Our findings support the hypothesis that the 'strong' kinetics (low fragility) of a liquid may arise from an underlying lambda transition above its glass transition.

Coincidence of collective relaxation anomaly and specific heat peak in a bulk metallic glass-forming liquid

“…In contrast to many similar QENS measurements 19,26,27,32,33 that are collected at Q values much lower than the structure factor S(Q) peak, the contribution to the neutron scattering signal in the wave vector transfer Q range we measured predominantly comes from the coherent scattering of individual elements. The structure factor S(Q) obtained by integrating the elastic scattering intensity in the energy transfer range of [−0.5, 0.5] meV shows a series of transitions from glassy state to "supercooled liquid", to crystal, and to liquid state over a temperature range from 27…”

“…In a recent study, a similar peak in c p of a Cu-Zr-Al based BMG has been attributed to an underlying temperature induced weak liquid-liquid phase transition characterized by change in length-scale of S(Q) 19 . The same interpretation has been applied to explain a similar nonmonotonic nature of the measured viscosity 49 .…”

“…There have been several studies regarding the mean self-dynamics of Cu-Zr based glass-forming liquids using QENS 19,26,27,32,33 . The relaxation behaviors of such melted liquid at small Q < 1.5Å −1 have been studied.…”

“…By alloying multiple elements of various atomic sizes, crystallization can be suppressed, and consequently high quality metallic glasses with sizes as large as 5 to 10 cm can be produced 15,16 . Understanding the liquid state dynamics of such materials is essential to elucidate the physical properties of the glassy state [17][18][19][20] . Despite numerous active ongoing research efforts, a quantitative description of the glass transition of metallic liquids remains elusive.…”

Computer simulations of glasses: the potential energy landscape

“…This fragile-strong behaviour is thought to be intimately connected with the phenomenon of polyamorphism in glasses [37]. A dynamical crossover temperature T B , well above T g , was established as the strong-fragile transition for oterphenyl recently [38], and it has also been suggested that a liquid-liquid phase transition may result in the change in fragility [39]. How does fragility affect glass-forming ability?…”