Microstructure of fragile metallic glasses inferred from ultrasound-accelerated crystallization in Pd-based metallic glasses

• Published in: Physical review letters Vol. 95; no. 24; p. 245501
• Main Authors: Ichitsubo, T, Matsubara, E, Yamamoto, T, Chen, H S, Nishiyama, N, Saida, J, Anazawa, K
• Format: Journal Article
• Language: English
• Published: United States 09.12.2005
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.95.245501

By utilizing ultrasonic annealing at a temperature below (or near) the glass transition temperature Tg, we revealed a microstructural pattern of a partially crystallized Pd-based metallic glass with a high-resolution electron microscopy. On the basis of the observed microstructure, we inferred a plausible microstructural model of fragile metallic glasses composed of strongly bonded regions surrounded by weakly bonded regions (WBRs). The crystallization in WBRs at such a low temperature under the ultrasonic vibrations is caused by accumulation of atomic jumps associated with the beta relaxation being resonant with the ultrasonic strains. This microstructural model successfully illustrates a marked increase of elasticity after crystallization with a small density change and a correlation between the fragility of the liquid and the Poisson ratio of the solid.