Comments about a recent publication entitled “Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions”

Tournier, R.; Ojovan, Michael I.

doi:10.1016/j.scriptamat.2021.114039

Cited by 3 publications

(3 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to the nucleation temperatures T n− below T m , the existence of a homogenous nucleation temperature T n+ above T m is confirmed by many experiments, observing the undercooling versus the overheating rates of liquid elements, and glassforming melts [43,65,[75][76][77][78]. This nucleation temperature has confirmed the existence of a second melting temperature, T n+ , of growth nuclei above T m , and of their homogeneous nucleation at temperatures weaker than θ n+ , as shown in several publications [30][31][32][33][34][35][36][37][38][39][79][80][81][82].…”

Section: The Bulk Glassy State Below T Gsupporting

confidence: 65%

Multiple Melting Temperatures in Glass-Forming Melts

Tournier

Ojovan

2022

Sustainability

Self Cite

View full text Add to dashboard Cite

All materials are vitrified by fast quenching even monoatomic substances. Second melting temperatures accompanied by weak exothermic or endothermic heat are often observed at Tn+ after remelting them above the equilibrium thermodynamic melting transition at Tm. These temperatures, Tn+, are due to the breaking of bonds (configurons formation) or antibonds depending on the thermal history, which is explained by using a nonclassical nucleation equation. Their multiple existence in monoatomic elements is now demonstrated by molecular dynamics simulations and still predicted. Proposed equations show that crystallization enthalpy is reduced at the temperature Tx due to new vitrification of noncrystallized parts and their melting at Tn+. These glassy parts, being equal above Tx to singular values or to their sum, are melted at various temperatures Tn+ and attain 100% in Cu46Zr46Al8 and 86.7% in bismuth. These first order transitions at Tn+ are either reversible or irreversible, depending on the formation of super atoms, either solid or liquid.

show abstract

Section: The Bulk Glassy State Below T Gsupporting

confidence: 65%

Multiple Melting Temperatures in Glass-Forming Melts

Tournier

Ojovan

2022

Sustainability

Self Cite

View full text Add to dashboard Cite

show abstract

“…Annealing a melt between T m and T n+ induces bonds and may develop bond percolation leading to crystallization at T m without undercooling. The temperatures T n+ are not easy to recognize because they are mixed with liquidus temperatures in non-congruent materials [ 69 , 70 , 71 ].…”

Section: Introductionmentioning

confidence: 99%

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

Tournier

Ojovan

2021

Materials

Self Cite

View full text Add to dashboard Cite

A second melting temperature occurs at a temperature Tn+ higher than Tm in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bonds up to Tn+. Recent MD simulations show full melting at Tn+ = 1.119Tm for Zr, 1.126Tm for Ag, 1.219Tm for Fe and 1.354Tm for Cu. The non-classical homogeneous nucleation model applied to liquid elements is based on the increase of the Lindemann coefficient with the heating rate. The glass transition at Tg and the nucleation temperatures TnG of glacial phases are successfully predicted below and above Tm. The glass transition temperature Tg increases with the heating rate up to Tn+. Melting and crystallization of glacial phases occur with entropy and enthalpy reductions. A universal law relating Tn+ and TnG around Tm shows that TnG cannot be higher than 1.293Tm for Tn+= 1.47Tm. The enthalpies and entropies of glacial phases have singular values, corresponding to the increase of percolation thresholds with Tg and TnG above the Scher and Zallen invariant at various heating and cooling rates. The G-phases are metastable up to Tn+ because the antibonds are broken by homogeneous nucleation of bonds.

show abstract

“…The first one leads to the glass formation temperature, while the second is a nucleation reduced temperature θ n+ above T m obtained in many experiments, observing the undercooling versus the overheating rates of liquid elements, and glass-forming melts [39][40][41][42][43]. These nucleation temperatures predict, for consequence, the existence of second melting temperatures T n+ of growth nuclei above T m and their growth below T m , shown in several publications [11,32,[44][45][46][47][48][49][50][51][52][53][54][55][56][57].…”

Section: Predictions Of Nchn and Configuron Models 21 The Nonclassica...mentioning

confidence: 79%

NiTi2, a New Liquid Glass

Tournier,

Ojovan

2023

Materials

Self Cite

View full text Add to dashboard Cite

Many endothermic liquid–liquid transitions, occurring at a temperature Tn+ above the melting temperature Tm, are related to previous exothermic transitions, occurring at a temperature Tx after glass formation below Tg, with or without attached crystallization and predicted by the nonclassical homogenous nucleation equation. A new thermodynamic phase composed of broken bonds (configurons), driven by percolation thresholds, varying from ~0.145 to Δε, is formed at Tx, with a constant enthalpy up to Tn+. The liquid fraction Δε is a liquid glass up to Tn+. The solid phase contains glass and crystals. Molecular dynamics simulations are used to induce, in NiTi2, a reversible first-order transition by varying the temperature between 300 and 1000 K under a pressure of 1000 GPa. Cooling to 300 K, without applied pressure, shows the liquid glass presence with Δε = 0.22335 as memory effect and Tn+ = 2120 K for Tm = 1257 K.

show abstract

Comments about a recent publication entitled “Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions”

Cited by 3 publications

References 16 publications

Multiple Melting Temperatures in Glass-Forming Melts

Multiple Melting Temperatures in Glass-Forming Melts

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

NiTi2, a New Liquid Glass

Contact Info

Product

Resources

About