TY - THES

T1 - Synchrotron-Based Characterization of Bulk Metallic Glasses

AU - Rovira Ferrer, David

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Synchrotron X-ray diffraction allows in-situ monitoring of rapid structural changes in materials during the application of external stimuli such as mechanical, chemical or thermal processes. In bulk metallic glasses, this allows the identification of metastable phases emerging from the amorphous matrix during temperature programmes as applied during Fast Differential Scanning Calorimetry (FDSC) with high heating and cooling rates in the range of 1 - 100 000 K/s. However, the high energy and focused beam provided by the latest generation of synchrotron facilities could alter the energetic states of the material and its crystallisation mechanisms. In this work, a Pt57.5Cu14.7Ni5.3P22.5 (at.%) alloy produced by suction casting is subjected to FDSC experiments under in-situ and ex-situ control, i.e. with and without X-ray irradiation. The different thermal transformations, activation energies and continuous heat transformation diagrams are calculated for comparison. Significant differences are found between the two conditions, the most notable being the higher number of crystalline phases and the annealing step at 296ºC with X-rays on. It is hypothesised that the absorption of X-rays by the gold chip and the supercooled liquid state of the alloy respectively heat the sample and increase the vibrational kinetics of the light elements in the material. This means that the results of the in-situ synchrotron characterisation should be considered as "radiation-influenced".

AB - Synchrotron X-ray diffraction allows in-situ monitoring of rapid structural changes in materials during the application of external stimuli such as mechanical, chemical or thermal processes. In bulk metallic glasses, this allows the identification of metastable phases emerging from the amorphous matrix during temperature programmes as applied during Fast Differential Scanning Calorimetry (FDSC) with high heating and cooling rates in the range of 1 - 100 000 K/s. However, the high energy and focused beam provided by the latest generation of synchrotron facilities could alter the energetic states of the material and its crystallisation mechanisms. In this work, a Pt57.5Cu14.7Ni5.3P22.5 (at.%) alloy produced by suction casting is subjected to FDSC experiments under in-situ and ex-situ control, i.e. with and without X-ray irradiation. The different thermal transformations, activation energies and continuous heat transformation diagrams are calculated for comparison. Significant differences are found between the two conditions, the most notable being the higher number of crystalline phases and the annealing step at 296ºC with X-rays on. It is hypothesised that the absorption of X-rays by the gold chip and the supercooled liquid state of the alloy respectively heat the sample and increase the vibrational kinetics of the light elements in the material. This means that the results of the in-situ synchrotron characterisation should be considered as "radiation-influenced".

KW - metallic glass

KW - synchrotron X-ray diffraction

KW - thermal transitions

KW - in-situ characterization

KW - Metallisches Glas

KW - Synchrotron-Röntgenbeugung

KW - thermische Übergänge

KW - in-situ Charakterisierung

U2 - 10.34901/mul.pub.2023.132

DO - 10.34901/mul.pub.2023.132

M3 - Master's Thesis

ER -