Metallic Glacial Glass Formation by a First-Order Liquid–Liquid Transition

Abstract

The glacial phase, with an apparently glassy structure, can be formed by a first-order transition in some molecular-glass-forming supercooled liquids. Here we report the formation of metallic glacial glass (MGG) from the precursor of a rare-earth-element-based metallic glass via the first-order phase transition in its supercooled liquid. The excellent glass-forming ability of the precursor ensures the MGG to be successfully fabricated into bulk samples (with a minimal critical diameter exceeding 3 mm). Distinct enthalpy, structure, and property changes are detected between MGG and metallic glass, and the reversed “melting-like” transition from the glacial phase to the supercooled liquid is observed in fast differential scanning calorimetry. The kinetics of MGG formation is reflected by a continuous heating transformation diagram, with the phase transition pathways measured at different heating rates taken into account. The finding supports the scenario of liquid–liquid transition in metallic-glass-forming liquids.

Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations

“…The melting is produced when the configurons percolation occurs. The crystallization occurs at T m after slow cooling from homogeneous melts when the bond number becomes equal to the percolation threshold [ 34 , 35 , 65 , 66 ]. It is important to note that the crystallization entropy loss below T m is expected to be equal and opposite to the melting entropy observed above T m at the temperature T n+ [ 1 ].…”

“…Heating the glass through T g breaks the atomic bonds and gives rise to configurons that are always accompanied by a second-order phase transition [ 7 , 8 , 9 , 10 , 11 , 12 ]. The non-classical homogeneous nucleation (NCHM) model predicts the temperatures of glasses, stable and ultrastable glasses [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], and glacial phases [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ] showing that a new phase called Phase 3 appears after heating the quenched liquids through T g with an enthalpy equal to the difference ∆ε lg between those of liquids 1 and 2. Quenched Liquid 1 has an initial enthalpy, before giving rise to the glass state, equal to ε ls H m, varying with the square of the reduced temperature θ = T−T m )/T m as shown in Equation (1) (H m being the melting heat of crystals) [ 36 ]: …”

“…High heating rate increases the glass transition temperature [ 44 ]. Recent studies showed two associated transitions to glacial phases for various heating rates [ 35 ]. Exothermic transitions were observed during the first heating at the nucleation temperature of glacial phases followed, at higher temperatures, by endothermic glass transitions.…”

High-entropy induced a glass-to-glass transition in a metallic glass

“…These additional results further suggest that a high-entropy effect is discovered, which enables a wide tunability of the glass states, and indicate that such glass-to-glass transitions would not be limited in the present HEMGs. Compared to the previous works on MGs with metalloid elements (e.g., P 15 , 16 ) or rare earth elements (e.g., La, Ce 46 ), the proposed high-entropy effect moves the phenomenon from the special cases to general cases with a series of HEMGs discovered, instead of only one special MG. In such consideration, the HEMGs may serve as model materials in exploring the glass-to-glass transitions and glass nature in the fields of materials science and condensed-matter physics.…”

“…After T start , the bifurcations of both the peak positions and peak heights of r 21 and r 22 can be clearly noticed, which suggest that the splitting of the second peak of G ( r ) becomes prominent. These results indicate that the glass-to-glass transition is associated with significant short- and medium-range structural changes, and the changes in the short-range structures is much stronger than typical structural relaxation 31 – 37 and glass-to-glass or liquid-to-liquid transitions 15 , 16 , 46 . Based on these results, a schematic structural change of the phase transition is prepared (Supplementary Note 7 and Supplementary Fig.…”