# Thermal and Thermomechanical Analysis of Amorphous Metals: A Compact Review
## 2 Thermal Characterization of Amorphous Metals  
### A Brief Overview of Conventional Technology  
#### 2.1.1 Differential Scanning Calorimetry of Metallic Glasses  
Conventional thermal analysis implies differential thermal analysis (DTA) and differential scanning calorimetry (DSC), both of which are methods that measure heat flux differences between a reference sample and the measured sample. The main difference lies in the collected signal; for DTA, that is the temperature difference between a reference sample and the measured sample, while for DSC, that is the direct heat flux difference between a reference sample and the measured sample. For DSC, this commonly involves different power outputs being applied to the heaters to keep the reference and measured samples at the same temperature. On the other hand, DTA is capable of simultaneous thermogravimetric analysis (TGA), which is the measurement of the sample's mass, while DSC is not. Calorimetry methods use a flat heater and a crucible in which the sample is deposited, which can achieve an average cooling rate of around 50 K min\({}^{-1}\) and a maximum heating rate of 200 K min\({}^{-1}\)[41]. It is a standard method of analysis for amorphous metals, primarily for the determination of the glass transition temperature [42] and critical cooling rates, which, along with the melting point of the alloy, define the metal's glass-forming ability (GFA), best described by Equation (1) [43]:  
\[\gamma_{m}=\frac{2T_{x}-T_{g}}{T_{l}} \tag{1}\]  
where \(T_{x}\), \(T_{g}\), and \(T_{l}\) stand for crystallization onset, glass transition onset, and liquidus temperature, respectively. The best glass-forming ability criterion has already been discussed and studied systematically, and was shown to be the one presented in Equation (1) due to the physical definitions of the parameters and the range of applicability. For further insight into all the proposed GFA criteria and their correlation with critical cooling rate, as well as their validity, we highly recommend the work of [PERSON] et al. [43], as it will not be discussed further in the scope of this work. Critical cooling rate \(R_{c}\) is measured in many ways, depending on the studied system. One of the most common methods is the continuous cooling method, where a number of discrete cooling rates are applied until a fully amorphous structure is obtained. It is quite easy but requires a substantial amount of experimental work [44]. The Colmenero and Barandiaran (CB) method requires fewer experiments and involves measuring \(T_{l}\) at a constant heating rate and the temperature of solidification \(T_{xc}\) at varying cooling rates [45]. Another important method is the time-temperature-transformation (TTT) curve method, which relies upon constructing a TTT diagram that defines the time required at any temperature to form a volume fraction of crystallized species. The critical cooling rate is defined as the slope that nearly reaches the TTT curve:  
\[R_{c}=\frac{T_{m}-T_{n}}{t_{n}} \tag{2}\]  
where \(T_{m}\) is the melting temperature, and \(T_{n}\) and \(t_{n}\) are temperature and time from the TTT curve [46].