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Fe-based metallic glass has wide industrial application due to its unique mechanical behavior and magnetic properties. In the present work, the non-isothermal crystallization kinetics in Fe68Nb6B23Mo3 glassy alloys were investigated by differential scanning calorimeter (DSC). The results indicate that both the glass transformation and crystallization process display an obvious kinetic effect. The activation energy is calculated using Kissinger's method and Ozawar's method. The activation energy for Tg (glass transition temperatures), Tx (crystallization initiation temperatures) and Tp (crystallization peak temperatures) calculated from Kissinger equation, is 308 ± 4, 342 ± 5 and 310 ± 7 kJ mol−1, respectively. The activation energy for Tg, Tx and Tp calculated from Ozawa equation is 322 ± 3, 356 ± 5 and 325 ± 7 kJ mol−1, respectively. With the increase of the crystallization volume fraction x, the Avrami exponent n(x) first decreases and then increases. At the preliminary step, 0 < x < 0.25, 2.5 < n(x) < 4.0 stands for the growth from a small size with an increasing nucleation rate. When 0.25 < x < 0.71, n(x) decreases from 2.5 to 1.5, indicating that this stage is controlled by the growth of small particles with a decreasing nucleation rate. [ABSTRACT FROM AUTHOR]

The nonisothermal crystallization kinetics for the first crystallization event of Cr‐rich metallic glass (MG) Cr29.4Fe29.4Mo14.7C14.7B9.8Y2 with desirable properties was systematically studied by Kissinger, Ozawa, Kissinger‐Akahira‐Sunose (KAS), Ozawa‐Flynn‐Wall (OFW), and Vogel‐Fulcher‐Tammann approaches using differential scanning calorimeter. The apparent activation energy (E) for characteristic temperatures deduced by Kissinger approach is comparable with that deduced by Ozawa approach. The Eg for the glass transition temperature is smaller than the Ep1 for the peak temperature of the first crystallization event and larger than E for other characteristic temperatures, exhibiting that the glass transition is easier than the growth process of the first crystallization event and more difficult than other processes. The local activation energy estimated by KAS and OFW approaches shows approximate tendency of increasing initially and then gradually decreasing, which indicates that the crystallization process is difficult at first and then gradually becomes easy. The local Avrami exponent (n(x)) changes from n(x) > 2.5 to 1.5 < n(x) < 2.5 for crystallization under low heating rate and from n(x) > 2.5 to 0 < n(x) < 1.5 for crystallization under high heating rate, corresponding to a diffusion‐governed crystallization changing from enhancing nucleation rate to reducing nucleation rate under low heating rate and from enhancing nucleation rate to preexisting nuclei under high heating rate, respectively. The kinetic fragility parameter shows that the glass‐forming liquid of the present MG is intermediate type with moderate glass‐forming ability. The results would provide comprehensive insights to understand the formation of Cr‐rich MG. [ABSTRACT FROM AUTHOR]

Abstract A ameliorative criterion for predicting the glass-forming ability of metallic glasses was presented. The coefficient of determination (R 2) of experimental log 10 (R c) versus the predicted log 10 { R c l i n e a r (T r g , D) } is 0.72. When the predicted log 10 { R c l i n e a r (T r g , D) } is replaced with our predicted log 10 { R c l i n e a r (T r g , 1 D) } , the coefficient of determination (R 2) will increase from 0.72 to 0.94, which is a great improvement for evaluating glass-forming ability (GFA). Highlights • A ameliorative criterion for predicting the glass-forming ability was presented. • The coefficient of determination (R 2) of experimental log 10 (R c) versus log 10 { R c l i n e a r (T r g , D) } is 0.72. • R 2 will increase from 0.72 to 0.94, when log 10 { R c l i n e a r (T r g , D) } is replaced with log 10 { R c l i n e a r (T r g , 1 D) }. [ABSTRACT FROM AUTHOR]

Ideal glass transition temperatures and transition activation energies of CuZrAl metallic glass was investigated using differential scanning calorimetry (DSC). The Vogel-Fulcher-Tammann temperature T and Kauzmann temperature T were determined, respectively, and T is greater than T . Meanwhile, activation energies of glass transition E , onset crystallization E and crystallization peak E were deduced to be 634.2 ± 15, 444 ± 16.1 and 366.8 ± 25.1 kJ mol, which indicates that glass transition is harder than crystallization process to proceed. [ABSTRACT FROM AUTHOR]

Abstract: A model to express the dependence of the crystal–melt interfacial energy on the temperature for metals is proposed. The crystal–melt interfacial energies, the homogeneous nucleation undercoolings and the critical cooling rates to form ideal metallic glasses of silver, copper and nickel have been predicted according to the present model and simulated by the molecular dynamics method. The results show that the crystal–melt interfacial energy of metals increases nonlinearly with temperature. Over a wide temperature range from the melting point to the glass transition temperature the predicted results for the crystal–melt interfacial energy, the homogeneous nucleation undercooling and the critical cooling rate to form ideal metallic glasses from the present crystal–melt interfacial energy model are in good agreement with the experimental results reported, as well as the results of molecular dynamics simulations based on different EAM potentials of the metals. [Copyright &y& Elsevier]

The strength parameter D, ideal glass transition temperature T 0 , and fragility parameter m are vital parameters and frequently used to analyze significant problems in various glass-forming liquids. It is found that parameters D , T 0 and m will have great difference when these values for the same glass-forming liquid are obtained by fitting the measured viscosity data in different temperature ranges near glass transition temperature T g. In order to obtain accurate parameters (T 0 , D and m), the temperature dependences of viscosity in different temperature ranges are studied. The results show that in the temperature range 0.97 T g ~1.16 T g , the fitting viscosity data obtained by the measured data in temperature ranges (f)~(k) and Plazek's expression are close to the measured viscosity data. However, there are still great difference between the minimum and maximum values for fluctuant T 0 and D values, which are 28.61 K and 24.91, respectively. The study further finds that parameters obtained using the measured viscosity data in temperature ranges (g)~(i) and (k) by VFT relation are more accurate and the maximal fluctuations of T 0 and D parameters are decreased to 10.57 K and 10.79, respectively. Furthermore, parameters obtained by the measured data in (g) are the most accurate than those obtained by the measured data in any temperature range. Variations of Vogel-Fulcher-Tammann parameters with different temperature ranges (a)~(n). Image 1 • Fragility and VFT parameters near glass transition temperature are investigated. • These parameters obtained by different measured data will have great difference. • The accurate fragility and VFT parameters are obtained. [ABSTRACT FROM AUTHOR]

The Kauzmann temperature TK is a lower limit of glass transition temperature, and is known as the ideal thermodynamic glass transition temperature. A supercooled liquid will condense into glass before TK. Studying the ideal glass transition temperature is beneficial to understanding the essence of glass transition in glass-forming liquids. The Kauzmann temperature TK values are predicted in 38 kinds of glass-forming liquids. In order to acquire the accurate predicted TK by using a new deduced equation, we obtained the best fitting parameters of the deduced equation with the high coefficient of determination (R2 = 0.966). In addition, the coefficients of two reported relations are replaced by the best fitting parameters to obtain the accurate predicted TK, which makes the R2 values increase from 0.685 and 0.861 to 0.970 and 0.969, respectively. Three relations with the best fitting parameters are applied to obtain the accurate predicted TK values. [ABSTRACT FROM AUTHOR]

Herein, measured and ideal glass transition temperatures of glass-forming liquids have been investigated. The value of T 0 / T g increases with increasing fragility parameter m or decreasing strength parameter D (where T g and T 0 are the measured and ideal glass transition temperatures, respectively). We utilize T 0 / T g values to classify various glass-forming liquids into three broad categories, which are strong, metallic glass-forming (intermediate) and fragile liquids. The result reveals that strong liquids with 15.25 < m ≤ 30 (or 37.3 ≤ D) have 0 < T 0 / T g ≤ 0.49. By contrast, fragile liquids obtain 0.82 ≤ T 0 / T g ≤ 0.94 when m values lie in 100 ≤ m ≤ 214 (or 1.8 ≤ D ≤ 9.1). Metallic glass-forming liquids have 0.52 ≤ T 0 / T g ≤ 0.77 when m values have 32 ≤ m ≤ 66 (or 10.8 ≤ D ≤ 32.8). • Measured and ideal glass transition temperatures of glass-forming liquids are investigated. • T 0 / T g values are predicted using fragility parameter m and strength parameter D at different m min. • T 0 / T g values are utilized to classify various glass-forming liquids into three broad categories. [ABSTRACT FROM AUTHOR]

The reduced glass transition temperature (Trg) and fragility index (m) are both used to predict the critical cooling rate (Rc). When either Trg or m is individually used to predict log10(Rc), a large deviation occurrs in the prediction of log10(Rc) because both of the corresponding correlations have low coefficients of determination (R2). The R2 value increases from either 0.33 (by using only Trg) or 0.68 (by using only m) to 0.91 by using both Trg and m. Therefore, the glass‐forming ability (GFA) is estimated more accurately when Trg and m are both applied to predict log10(Rc) through a binary linear regression analysis. [ABSTRACT FROM AUTHOR]