The L-G phase transition in binary Cu-Zr metallic liquids

Q An and WL Johnson and K Samwer and SL Corona and YD Shen and WA Goddard, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 24, 497-506 (2021).

DOI: 10.1039/d1cp04157f

The authors recently reported that undercooled liquid Ag and Ag-Cu alloys both exhibit a first order phase transition from the homogeneous liquid (L-phase) to a heterogeneous solid-like G-phase under isothermal evolution. Here, we report a similar L-G transition and heterogenous G-phase in simulations of liquid Cu-Zr bulk glass. The thermodynamic description and kinetic features (viscosity) of the L-G-phase transition in Cu-Zr simulations suggest it corresponds to experimentally reported liquid-liquid phase transitions in Vitreloy 1 (Vit1) and other Cu-Zr- bearing bulk glass forming alloys. The Cu-Zr G-phase has icosahedrally ordered cores versus fcc/hcp core structures in Ag and Ag-Cu with a notably smaller heterogeneity length scale ?. We propose the L-G transition is a phenomenon in metallic liquids associated with the emergence of elastic rigidity. The heterogeneous core-shell nano- composite structure likely results from accommodating strain mismatch of stiff core regions by more compliant intervening liquid-like medium.

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