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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 notablymore »Free, publicly-accessible full text available December 22, 2022
Observation of an apparent first-order glass transition in ultrafragile Pt–Cu–P bulk metallic glasses
An experimental study of the configurational thermodynamics for a series of near-eutectic Pt80-
xCu xP20bulk metallic glass-forming alloys is reported where 14 < x< 27. The undercooled liquid alloys exhibit very high fragility that increases as xdecreases, resulting in an increasingly sharp glass transition. With decreasing x, the extrapolated Kauzmann temperature of the liquid, T K, becomes indistinguishable from the conventionally defined glass transition temperature, T g. For x< 17, the observed liquid configurational enthalpy vs. Tdisplays a marked discontinuous drop or latent heat at a well-defined freezing temperature, T gm. The entropy drop for this first-order liquid/glass transition is approximately two-thirds of the entropy of fusion of the crystallized eutectic alloy. Below T gm,more »
A molten metal is an atomic liquid that lacks directional bonding and is free from chemical ordering eﬀects. Experimentally, liquid metals can be undercooled by up to ∼20% of their melting temperature but crystallize rapidly in subnanosecond time scales at deeper undercooling. To address this limited metastability with respect to crystallization, we employed molecular dynamics simulations to study the thermodynamics and kinetics of the glass transition and crystallization in deeply undercooled liquid Ag. We present direct evidence that undercooled liquid Ag undergoes a ﬁrst-order conﬁgurational freezing transition from the high-temperature homogeneous disordered liquid phase (L) to a metastable, heterogeneous, conﬁgura-tionallymore »