scholarly journals Metallic Glasses: A New Approach to the Understanding of the Defect Structure and Physical Properties

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 605 ◽  
Author(s):  
Vitaly Khonik ◽  
Nikolai Kobelev
Keyword(s):  
Shear Modulus ◽  
Physical Properties ◽  
Experimental Verification ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Defect Structure ◽  
Relaxation Phenomena ◽  
Volume Changes ◽  
New Approach ◽  
Heat Effects

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.

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

2021 ◽  
Author(s):  
Andrey Makarov ◽  
Gennadii V Afonin ◽  
Alexander S Aronin ◽  
Nikolai Kobelev ◽  
Vitaly A Khonik
Keyword(s):  
Shear Modulus ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Entropy Change ◽  
Free Energy Barrier ◽  
Novel Approach ◽  
Heat Effects ◽  
Kinetics Of ◽  
Good Agreement ◽  
Non Equilibrium

Abstract 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.

On the origin of heat effects and shear modulus changes upon structural relaxation and crystallization of metallic glasses

2017 ◽  
Vol 475 ◽  
pp. 48-52 ◽  
Author(s):  
G.V. Afonin ◽  
Yu.P. Mitrofanov ◽  
A.S. Makarov ◽  
N.P. Kobelev ◽  
V.A. Khonik
Keyword(s):  
Shear Modulus ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Heat Effects

On the nature of heat effects and shear modulus softening in metallic glasses: A generalized approach

2014 ◽  
Vol 115 (3) ◽  
pp. 033513 ◽  
Author(s):  
N. P. Kobelev ◽  
V. A. Khonik ◽  
A. S. Makarov ◽  
G. V. Afonin ◽  
Yu. P. Mitrofanov
Keyword(s):  
Shear Modulus ◽  
Metallic Glasses ◽  
Heat Effects

Determination of the activation energy spectrum of structural relaxation in metallic glasses using calorimetric and shear modulus relaxation data

2014 ◽  
Vol 116 (12) ◽  
pp. 123507 ◽  
Author(s):  
A. N. Tsyplakov ◽  
Yu. P. Mitrofanov ◽  
A. S. Makarov ◽  
G. V. Afonin ◽  
V. A. Khonik
Keyword(s):  
Activation Energy ◽  
Energy Spectrum ◽  
Shear Modulus ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Relaxation Data

Free Volume Changes in Bulk Amorphous Alloys During Structural Relaxation and in the Supercooled Liquid State

1998 ◽  
Vol 554 ◽  
Author(s):  
C. Nagel ◽  
K. Rätzke ◽  
E. Schmidtke ◽  
F. Faupel
Keyword(s):  
Free Volume ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Excess Volume ◽  
Positron Lifetime ◽  
Supercooled Liquid ◽  
Mechanical Tests ◽  
Volume Changes ◽  
Shallow Traps

AbstractVolume changes in Zr46.7Ti8.3Cu7.5Ni10Be27.5 and Zr 65Al7.5Ni10Cu17.5 bulk metallic glasses have been observed by positron annihilation and density measurements. At low cooling rates excess volume of the order of 0.1 % is quenched in both glasses. Isothermal relaxation kinetics below the glass transition temperature obey a Kohlrausch law with exponents of β≈(0.3 ± 0.1). Structural relaxation is not accompanied by embrittlement, as indicated by simple mechanical tests. The outer surface plays a crucial role in annealing of excess volume, which can be restored by annealing above Tg. The observed free volume changes are at variance with the behavior of a perfectly strong glass. The temperature dependence of the positron lifetime is discussed in terms of thermal detrapping from shallow traps.

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