Phase separation and crystallization in the Zr 41.2–Ti 13.8–Cu 12.5–Ni 10–Be 22.5 bulk metallic glass determined by physical measurements and electron microscopy

Abstract

Phase separation and crystallization processes of bulk amorphous Zr 41.2–Ti 13.8–Cu 12.5–Ni 10–Be 22.5 (Vitreloy 1) are reported. In addition to classical differential scanning calorimetry and X-ray diffraction experiments, thermoelectric power (TEP) measurements, mechanical spectroscopy and high resolution transmission electron microscopy (HR-TEM) observations are performed. During annealing in the supercooled liquid region both reversible and irreversible microstructure evolutions are observed before the onset of crystallization, as indicated by a TEP variation, which can be positive or negative, depending on annealing conditions. Once the crystallization process is started, size and volume fraction of nanocrystallized particles increase. The isolated nanocrystals increase the elastic features in the glass temperature region, but the main viscoelastic relaxation is still observed, indicating therefore that the crystalline phase embedded in the decomposed amorphous matrix does not form a continuous network of rigid particles. Both phase separation and crystallization processes are discussed on the basis of microstructure observations, physical and mechanical measurements.