Glass Transition Studies of Bulk Metallic Glasses

In this chapter, we will study the glass transition of bulk metallic glasses by heating the glass or cooling the liquid with a constant heating rate through \(T_g\) or by holding the glass at a temperature below \(T_g\) in a calorimeter as well as in the x-ray beam of a synchrotron. Chapter 6.1 reports mainly on standard differential scanning calorimetric measurements for the study of the \(T_g\) -shift as a function of applied rate. Chapter 6.2, introduces the novel application of chip-calorimetry to the study of the glass transition of BMGs. Only recently, a high temperature chip-calorimeter became available and this has broadened the range of heating and cooling rates of calorimeters up to 50,000 K/s, allowing for measurements at ultrashort time scales that were previously impossible to be experimentally explored. We will see that with a chip-calorimeter, it is possible to study the glass transition not only upon heating (classical experimental way) but also directly during the vitrification path, i.e., upon cooling. This allowed us, for the first time, the direct study of the vitrification kinetics from the melt. In addition, Sect. 6.3 focuses on various techniques to exploit the study of the so-called dynamic glass transition, which is directly connected with the atomic mobility of the system. Finally, Sect. 6.6 deals with the structural signatures of the glass transition which can be detected by high-energy x-ray techniques.