On the nature of enthalpy relaxation below and above the glass transition of metallic glasses

Abstract

Correlation between glass-forming ability, thermal stability, and crystallization kinetics of Cu-Zr-Ag metallic glasses J. Appl. Phys. 112, 063503 (2012) Evidence for ferromagnetic strain glass in Ni-Co-Mn-Ga Heusler alloy system Appl. Phys. Lett. 101, 101913 (2012) Nanosize icosahedral quasicrystal in Mg90Ca10 glass: An ab initio molecular dynamics study J. Chem. Phys. 137, 034503 (2012) Correlation between fragility and eutectic instability and glass-forming ability in binary metallic glasses under growth controlled conditions J. Appl. Phys. 111, 103525 (2012) Characteristic free volume change of bulk metallic glasses

Understanding of the Structural Relaxation of Metallic Glasses within the Framework of the Interstitialcy Theory

“…One can point out a good agreement between calculated and experimental heat release below T g and heat absorption above T g . Similar agreement was found for other Pd-and Zr-based metallic glasses [77][78][79]. Below T g , a decrease of the interstitialcy defect concentration upon heating leads to the heat release and related increase of the shear modulus.…”

“…x are the shear moduli of glass and parent crystal at room temperature, respectively, substituting Equation (1) into Equation (13), one can calculate the heat heat per unit time and per unit mass flow as [78]:…”

Theoretical analysis of the interconnection between the shear elasticity and heat effects in metallic glasses

“…This relationship was repeatedly tested on different metallic glasses. 2 It was found that it gives a good description of the kinetics of exothermal heat flow below T g and endothermal heat flow in the glass transition region both in the initial and relaxed states [22,[25][26][27]]. An example is given in Fig.…”

“…Refs. [22,[25][26][27]), fails at high temperatures T N T x (T x is the crystallization onset temperature). Recently, these problems were overcome by i) modification of the EMAT setup and ii) using samples of bulk glassy Zr 46 Cu 45 Al 7 Ti 2 , which combines relatively low internal friction as well as high viscosity and allows performing measurements above T x .…”

“…The underlying microscopic reason for the key role of the anharmonicity, like in crystals [30,31], might be the large local compression and related decreased interatomic distance between the atoms constituting the interstitialcy defect, 3 which makes important the steeply repulsive part of the interatomic potential. 2 Originally, the heat flow within the framework of the approach under consideration was derived as [25] …”