Atomic-Scale Structural Evolution and Stability of Supercooled Liquid of a Zr-Based Bulk Metallic Glass

Abstract

In this Letter, direct experimental evidence is provided for understanding the thermal stability with respect to crystallization in the Zr 41:2 Ti 13:8 Cu 12:5 Ni 10 Be 22:5 glass-forming liquid. Through high-resolution transmission electron microscopy, the atomic-structure evolution in the glass-forming liquid during the isothermal annealing process is clearly revealed. In contrast with the existing theoretical models, our results reveal that, prior to nanocrystallization, there exists a metastable state prone to forming icosahedralike atomic clusters, which impede the subsequent crystallization and hence stabilize the supercooled liquid. The outcome of the current research underpins the topological origin for the excellent thermal stability displayed by the Zr-based bulk metallic glass.

Kinetics of structural relaxation in bulk metallic glasses by mechanical spectroscopy: Determination of the stretching parameter βKWW

“…Additionally, structural relaxation can modify topological short range ordering (TSRO) and chemical short range ordering (CSRO) in metallic glasses [2,51]. Structure of metallic glasses annealed below T g tends to local medium-range ordered [52,53].…”

Hierarchical amorphous structures in a Zr50Cu42Al8 bulk metallic glass

“…The various microstructures consisting of short-rage orders, medium-range orders and phase separation comprise a hierarchical structure at the macroscopic scale in this ascast BMG specimen. It should be pointed out that the configurations of the atomic packing in metallic glasses, such as the short-range orders and the medium-range orders, are still being debated [28][29][30][31][32]. In the present work, the detailed atomic configurations of the macroscopic hierarchical structure are not fully understood, and further investigations are necessary to uncover the corresponding atomic structures.…”

Correlating the supercooled liquid region width with the fragility parameter in bulk metallic glasses

“…Experimental result suggests that the presence of the icosahedral-like atomic clusters in Zr-based BMG after annealing effectively raises the overall viscosity of the supercooled liquid and finally suppresses the crystallization. 20 The glass transition region when cooling is controlled by kinetic factors, e.g., by the viscosity. 21 The supercooled liquid region during a reverse heating process would be related to the viscosity variation.…”