Microstructure of fragile metallic glasses inferred from ultrasound-accelerated crystallization in Pd-based metallic glasses.
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.
Ichitsubo
T
T
Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan. tichi@mtl.kyoto-u.ac.jp
Matsubara
E
E
Yamamoto
T
T
Chen
H S
HS
Nishiyama
N
N
Saida
J
J
Anazawa
K
K