Vitaly Khonik - Academia.edu (original) (raw)

Papers by Vitaly Khonik

Research paper thumbnail of Recent Advancements in Metallic Glasses

Investigations of the structure and properties of metallic glasses constitute a subject of unabat... more Investigations of the structure and properties of metallic glasses constitute a subject of unabated interest [...]

Research paper thumbnail of A novel view of the nature of formation of metallic glasses, their structural relaxation, and crystallization

A novel view of the nature of formation of metallic glasses, their structural relaxation, and crystallization

Physics-Uspekhi

Research paper thumbnail of Rejuvenation of a Metallic and Oxide Glass by Cooling from the Supercooled Liquid State at Laboratory Rates

physica status solidi (RRL) – Rapid Research Letters, 2018

Research paper thumbnail of Thermodynamic approach for the understanding of the kinetics of heat effects induced by structural relaxation of metallic glasses

Thermodynamic approach for the understanding of the kinetics of heat effects induced by structural relaxation of metallic glasses

Journal of Physics: Condensed Matter, 2022

We present a novel approach to the understanding of heat effects induced by structural relaxation... more We present a novel approach to the understanding of heat effects induced by structural relaxation of metallic glasses. The key idea consists in the application of a general thermodynamic equation for the entropy change due to the evolution of a non-equilibrium part of a complex system. This non-equilibrium part is considered as a defect subsystem of glass and its evolution is governed by local thermoactivated rearrangements with a Gibbs free energy barrier proportional to the high-frequency shear modulus. The only assumption on the nature of the defects is that they should provide a reduction of the shear modulus—a diaelastic effect. This approach allows to determine glass entropy change upon relaxation. On this basis, the kinetics of the heat effects controlled by defect-induced structural relaxation is calculated. A very good agreement between the calculation and specially performed calorimetric and shear modulus measurements on three metallic glasses is found.

Research paper thumbnail of On the shear modulus and thermal effects during structural relaxation of a model metallic glass: Correlation and thermal decoupling

On the shear modulus and thermal effects during structural relaxation of a model metallic glass: Correlation and thermal decoupling

Journal of Materials Science & Technology, 2022

Research paper thumbnail of On the Shear Modulus and Thermal Effect During Structural Relaxation in a Model Metallic Glass: Correlation and Thermal Decoupling

On the Shear Modulus and Thermal Effect During Structural Relaxation in a Model Metallic Glass: Correlation and Thermal Decoupling

SSRN Electronic Journal, 2021

Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricat... more Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast state. Subsequently, the underlying structural relaxation was studied by investigating the modulus and thermal characteristics using in-situ shear modulus measurement and modulated differential scanning calorimetry. The results show that high-pressure torsion leads to shear modulus softening and an increase of the irreversible exothermic enthalpy, indicating a significant structural rejuvenation, while sub-Tg annealing causes shear modulus hardening and a decrease of the irreversible exothermic enthalpy. Besides, the reversible endothermic effect which reflects the heat capacity was found to be almost identical for all samples, independent on deformation or thermal history. The total heat flow can be well correlated to the shear modulus within the framework of interstitialcy theory. Furthermore, we demonstrate that the structural relaxation below Tg decouples into the internal stress relaxation and β-relaxation. The former is an irreversible process of releasing internal stress, accompanied by an exothermic effect and modulus hardening. The latter is a complex process involving kinetic and thermodynamic components, accompanied by an endothermic effect and modulus softening. Shadow glass transition and glass transition overshoot are related to the activation (cage-breaking) processes in the kinetics of β-relaxation and α-relaxation, respectively. This work indicates that β-relaxation and α-relaxation are kinetically and thermodynamically identical but occur in distinct temperature or frequency domains. Internal stress relaxation as a universal mechanism plays a significant role in the structural relaxation, and simultaneously modulates the diffusive relaxation spectrum.

Research paper thumbnail of A simple kinetic parameter indicating the origin of the relaxations induced by point(-like) defects in metallic crystals and glasses

A simple kinetic parameter indicating the origin of the relaxations induced by point(-like) defects in metallic crystals and glasses

Journal of Physics: Condensed Matter, 2020

Computer simulation shows that an increase of the volume V due to point defects in a simple metal... more Computer simulation shows that an increase of the volume V due to point defects in a simple metallic crystal (Al) and high entropy alloy (Fe20Ni20Cr20Co20Cu20) leads to a linear decrease of the shear modulus G. This diaelastic effect can be characterized by a single dimensionless parameter K = dln G/dln V. For dumbbell interstitials in single crystals K ≈ -30 while for vacancies the absolute K-value is smaller by an order of magnitude. In the polycrystalline state, K ≈ -20 but its the absolute value remains anyway 5-6 times larger than that for vacancies. The physical origin of this difference comes from the fact that dumbbell interstitials constitute elastic dipoles with highly mobile atoms in their nuclei and that is why produce much larger shear softening compared to vacancies. For simulated Al and high entropy alloy in the glassy state, K equals to -18 and -12, respectively. By the absolute magnitude, these values are by several times larger compared to the case of vacancies in the polycrystalline state of these materials. An analysis of the experimental data on isothermal relaxations of G as a function of V for six Zr-based metallic glasses tested at different temperatures shows that K is time independent and equals to ≈-43, similar to interstitials in single-crystals. It is concluded that K constitutes a important simple kinetic parameter indicating the origin of relaxations induced by point(-like) defects in the crystalline and glassy states.

Research paper thumbnail of Heat Effects Occurring in the Supercooled Liquid State and Upon Crystallization of Metallic Glasses as a Result of Thermally Activated Evolution of Their Defect Systems

Metals, 2020

We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liqu... more We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liquid state and upon crystallization of metallic glasses can be well reproduced using temperature dependences of their shear moduli. It is argued that the interrelation between the heat effects and shear modulus relaxation reflects thermally activated evolution of interstitial-type defect system inherited from the maternal melt.

Research paper thumbnail of Boson Heat Capacity Peak in Metallic Glasses: Evidence of the Same Defect‐Induced Heat Absorption Mechanism in Structurally Relaxed and Partially Crystallized States

physica status solidi (RRL) – Rapid Research Letters, 2018

The evolution of the Boson heat capacity peak in a typical metallic glass upon structural relaxat... more The evolution of the Boson heat capacity peak in a typical metallic glass upon structural relaxation and partial crystallization is studied. It is found that heat treatment changes the peak height in both fully amorphous and partially crystalline states in line with the prediction of the Interstitialcy theory.

Research paper thumbnail of Interstitial clustering in metallic systems as a source for the formation of the icosahedral matrix and defects in the glassy state

Interstitial clustering in metallic systems as a source for the formation of the icosahedral matrix and defects in the glassy state

Journal of Physics: Condensed Matter, 2019

The paper presents molecular dynamics and -statics simulations of a prototypical mono-atomic meta... more The paper presents molecular dynamics and -statics simulations of a prototypical mono-atomic metallic system (aluminum) and its defects in the crystalline and glassy states. It is shown that there is a thermodynamic driving force for the association of dumbbell interstitials in the crystalline lattice into clusters consisting of different amounts of defects. Clusters containing seven interstitials constitute perfect icosahedra. Within the general framework of the Interstitialcy theory, melting of simple metallic crystals is intrinsically related to a rapid increase of the concentration of dumbbell interstitials, which remain identifiable structural units in the liquid state. Then, the glass produced by rapid melt quenching contains interstitial-type defects. The idea of the present work is to argue that the major structural feature of many metallic glasses -- icosahedral ordering -- originates from the clustering of interstitial-type defects frozen-in upon melt quenching. Separate defects and their small clusters represent the defect part of the glassy structure.

Research paper thumbnail of Metallic Glasses: A New Approach to the Understanding of the Defect Structure and Physical Properties

Metals, 2019

The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different... more The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different relaxation phenomena occurring in metallic glasses upon structural relaxation and crystallization. The basic hypotheses of the IT and their experimental verification are shortly considered. The main focus is given on the interpretation of recent experiments on the heat effects, volume changes and their link with the shear modulus relaxation. The issues related to the development of the IT and its relationship with other models on defects in metallic glasses are discussed.

Research paper thumbnail of Relationship between the shear viscosity and heating rate in metallic glasses below the glass transition

Research paper thumbnail of Boson heat capacity peak and its evolution with the enthalpy state and defect concentration in a high entropy bulk metallic glass

Boson heat capacity peak and its evolution with the enthalpy state and defect concentration in a high entropy bulk metallic glass

Intermetallics

Research paper thumbnail of Recent Advancements in Metallic Glasses

Investigations of the structure and properties of metallic glasses constitute a subject of unabat... more Investigations of the structure and properties of metallic glasses constitute a subject of unabated interest [...]

Research paper thumbnail of A novel view of the nature of formation of metallic glasses, their structural relaxation, and crystallization

A novel view of the nature of formation of metallic glasses, their structural relaxation, and crystallization

Physics-Uspekhi

Research paper thumbnail of Rejuvenation of a Metallic and Oxide Glass by Cooling from the Supercooled Liquid State at Laboratory Rates

physica status solidi (RRL) – Rapid Research Letters, 2018

Research paper thumbnail of Thermodynamic approach for the understanding of the kinetics of heat effects induced by structural relaxation of metallic glasses

Thermodynamic approach for the understanding of the kinetics of heat effects induced by structural relaxation of metallic glasses

Journal of Physics: Condensed Matter, 2022

We present a novel approach to the understanding of heat effects induced by structural relaxation... more We present a novel approach to the understanding of heat effects induced by structural relaxation of metallic glasses. The key idea consists in the application of a general thermodynamic equation for the entropy change due to the evolution of a non-equilibrium part of a complex system. This non-equilibrium part is considered as a defect subsystem of glass and its evolution is governed by local thermoactivated rearrangements with a Gibbs free energy barrier proportional to the high-frequency shear modulus. The only assumption on the nature of the defects is that they should provide a reduction of the shear modulus—a diaelastic effect. This approach allows to determine glass entropy change upon relaxation. On this basis, the kinetics of the heat effects controlled by defect-induced structural relaxation is calculated. A very good agreement between the calculation and specially performed calorimetric and shear modulus measurements on three metallic glasses is found.

Research paper thumbnail of On the shear modulus and thermal effects during structural relaxation of a model metallic glass: Correlation and thermal decoupling

On the shear modulus and thermal effects during structural relaxation of a model metallic glass: Correlation and thermal decoupling

Journal of Materials Science & Technology, 2022

Research paper thumbnail of On the Shear Modulus and Thermal Effect During Structural Relaxation in a Model Metallic Glass: Correlation and Thermal Decoupling

On the Shear Modulus and Thermal Effect During Structural Relaxation in a Model Metallic Glass: Correlation and Thermal Decoupling

SSRN Electronic Journal, 2021

Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricat... more Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast state. Subsequently, the underlying structural relaxation was studied by investigating the modulus and thermal characteristics using in-situ shear modulus measurement and modulated differential scanning calorimetry. The results show that high-pressure torsion leads to shear modulus softening and an increase of the irreversible exothermic enthalpy, indicating a significant structural rejuvenation, while sub-Tg annealing causes shear modulus hardening and a decrease of the irreversible exothermic enthalpy. Besides, the reversible endothermic effect which reflects the heat capacity was found to be almost identical for all samples, independent on deformation or thermal history. The total heat flow can be well correlated to the shear modulus within the framework of interstitialcy theory. Furthermore, we demonstrate that the structural relaxation below Tg decouples into the internal stress relaxation and β-relaxation. The former is an irreversible process of releasing internal stress, accompanied by an exothermic effect and modulus hardening. The latter is a complex process involving kinetic and thermodynamic components, accompanied by an endothermic effect and modulus softening. Shadow glass transition and glass transition overshoot are related to the activation (cage-breaking) processes in the kinetics of β-relaxation and α-relaxation, respectively. This work indicates that β-relaxation and α-relaxation are kinetically and thermodynamically identical but occur in distinct temperature or frequency domains. Internal stress relaxation as a universal mechanism plays a significant role in the structural relaxation, and simultaneously modulates the diffusive relaxation spectrum.

Research paper thumbnail of A simple kinetic parameter indicating the origin of the relaxations induced by point(-like) defects in metallic crystals and glasses

A simple kinetic parameter indicating the origin of the relaxations induced by point(-like) defects in metallic crystals and glasses

Journal of Physics: Condensed Matter, 2020

Computer simulation shows that an increase of the volume V due to point defects in a simple metal... more Computer simulation shows that an increase of the volume V due to point defects in a simple metallic crystal (Al) and high entropy alloy (Fe20Ni20Cr20Co20Cu20) leads to a linear decrease of the shear modulus G. This diaelastic effect can be characterized by a single dimensionless parameter K = dln G/dln V. For dumbbell interstitials in single crystals K ≈ -30 while for vacancies the absolute K-value is smaller by an order of magnitude. In the polycrystalline state, K ≈ -20 but its the absolute value remains anyway 5-6 times larger than that for vacancies. The physical origin of this difference comes from the fact that dumbbell interstitials constitute elastic dipoles with highly mobile atoms in their nuclei and that is why produce much larger shear softening compared to vacancies. For simulated Al and high entropy alloy in the glassy state, K equals to -18 and -12, respectively. By the absolute magnitude, these values are by several times larger compared to the case of vacancies in the polycrystalline state of these materials. An analysis of the experimental data on isothermal relaxations of G as a function of V for six Zr-based metallic glasses tested at different temperatures shows that K is time independent and equals to ≈-43, similar to interstitials in single-crystals. It is concluded that K constitutes a important simple kinetic parameter indicating the origin of relaxations induced by point(-like) defects in the crystalline and glassy states.

Research paper thumbnail of Heat Effects Occurring in the Supercooled Liquid State and Upon Crystallization of Metallic Glasses as a Result of Thermally Activated Evolution of Their Defect Systems

Metals, 2020

We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liqu... more We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liquid state and upon crystallization of metallic glasses can be well reproduced using temperature dependences of their shear moduli. It is argued that the interrelation between the heat effects and shear modulus relaxation reflects thermally activated evolution of interstitial-type defect system inherited from the maternal melt.

Research paper thumbnail of Boson Heat Capacity Peak in Metallic Glasses: Evidence of the Same Defect‐Induced Heat Absorption Mechanism in Structurally Relaxed and Partially Crystallized States

physica status solidi (RRL) – Rapid Research Letters, 2018

The evolution of the Boson heat capacity peak in a typical metallic glass upon structural relaxat... more The evolution of the Boson heat capacity peak in a typical metallic glass upon structural relaxation and partial crystallization is studied. It is found that heat treatment changes the peak height in both fully amorphous and partially crystalline states in line with the prediction of the Interstitialcy theory.

Research paper thumbnail of Interstitial clustering in metallic systems as a source for the formation of the icosahedral matrix and defects in the glassy state

Interstitial clustering in metallic systems as a source for the formation of the icosahedral matrix and defects in the glassy state

Journal of Physics: Condensed Matter, 2019

The paper presents molecular dynamics and -statics simulations of a prototypical mono-atomic meta... more The paper presents molecular dynamics and -statics simulations of a prototypical mono-atomic metallic system (aluminum) and its defects in the crystalline and glassy states. It is shown that there is a thermodynamic driving force for the association of dumbbell interstitials in the crystalline lattice into clusters consisting of different amounts of defects. Clusters containing seven interstitials constitute perfect icosahedra. Within the general framework of the Interstitialcy theory, melting of simple metallic crystals is intrinsically related to a rapid increase of the concentration of dumbbell interstitials, which remain identifiable structural units in the liquid state. Then, the glass produced by rapid melt quenching contains interstitial-type defects. The idea of the present work is to argue that the major structural feature of many metallic glasses -- icosahedral ordering -- originates from the clustering of interstitial-type defects frozen-in upon melt quenching. Separate defects and their small clusters represent the defect part of the glassy structure.

Research paper thumbnail of Metallic Glasses: A New Approach to the Understanding of the Defect Structure and Physical Properties

Metals, 2019

The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different... more The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different relaxation phenomena occurring in metallic glasses upon structural relaxation and crystallization. The basic hypotheses of the IT and their experimental verification are shortly considered. The main focus is given on the interpretation of recent experiments on the heat effects, volume changes and their link with the shear modulus relaxation. The issues related to the development of the IT and its relationship with other models on defects in metallic glasses are discussed.

Research paper thumbnail of Relationship between the shear viscosity and heating rate in metallic glasses below the glass transition

Research paper thumbnail of Boson heat capacity peak and its evolution with the enthalpy state and defect concentration in a high entropy bulk metallic glass

Boson heat capacity peak and its evolution with the enthalpy state and defect concentration in a high entropy bulk metallic glass

Intermetallics