Abstract
The article presents investigations of Ti40Cu36Zr10Pd14 bulk metallic glass crystallization process heated with the rates of 10, 60, 100 and 140 K/min. High heating rates experiments were performed in a new type of differential scanning calorimeter equipped with a fast responding thermal sensor. Phase composition and microstructure were studied with x-ray diffraction and transmission electron microscopy. The observed crystallization proceeded in two separate steps. Applied high rates of heating/cooling resulted in the crystallization of only one CuTi phase, replacing typical multi-phase crystallization. The microstructure after crystallization was polycrystalline with some amount of amorphous phase retained. Kinetic parameters were determined with the use of the Kissinger and Friedman iso-conversional analysis and Matusita–Sakka iso-kinetic model. The kinetic analysis supplies results concerning autocatalytically activated mechanism of primary crystallization with decreasing activation energy and small density of quenched-in nuclei, in good agreement with previous structural investigations. The mechanism of secondary crystallization required dense nuclei site, increasing activation energy and large nucleation frequency. The amorphous phase of Ti40Cu36Zr10Pd14 BMG revealed high thermal stability against crystallization. Application of high heating rates in DSC experiments might be useful for the determination of mechanism and kinetic parameters in investigations of metallic glasses crystallization, giving reasonable results.
Highlights
Metallic glasses remain a current subject of the investigations in material sciences
It may be noticed that the first exothermic peak related to primary crystallization at the high-temperature side reveals broadening, which may be related to a prolonged, relatively slow crystallization process or/end large thermal lag, while the secondary crystallization peak is much narrower and Heating rates, K/min
Application of the high heating rates, between 60 and 140 K/min in differential scanning calorimetry (DSC) experiments proved to be useful for the determination of crystallization mechanism and the kinetic parameters in CuZrTiPd metallic glass investigations
Summary
Metallic glasses remain a current subject of the investigations in material sciences. Bulk metallic glasses, requiring relatively low critical cooling rates to form amorphous phase, are promising materials for some applications (Ref 1). A lot of attention has been given to finding amorphous equivalents of Al- and Ti-based light alloys. The Ti-based crystalline alloys are characterized by high specific strength and low density. Another important property of both crystalline and amorphous Ti alloys is their biocompatibility which enables their application as different types of implants (Ref [2,3,4]). The mechanical properties of BMGs may be better adapted to parameters required for human implants than those of crystalline alloys (Ref 5)
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