Nanoscale periodic corrugation to dimple transition due to “beat” in a bulk metallic glass

Abstract

We report an intriguing observation that the interaction of brittle nanoscale periodic corrugations (NPCs) can lead to the formation of ductile dimples on the dynamic fracture surface of a tough Vit 1 bulk metallic glass (BMG) under high-velocity plate impact. A "beat" phenomenon due to superposition of simple harmonic vibrations, approximately characterizing NPCs, is proposed to explain this unusual brittle-to-ductile transition. The present results agree well with our previously revealed energy dissipation mechanism in the fracture of BMGs.

Fractal in fracture of bulk metallic glass

“…Within the range of L 32 nm, the long-range correlation (H ¼ 0.95) of the profiles infers that the local plastic flow occurs during the formation of peak portion of the NPC. However, this characteristic length is smaller than the wavelength (w85 nm) of the initial perturbation of the meniscus instability for Vit 1 bulk MGs [21,26]. According to the ductile-to-brittle criterion for fracture of MGs [21,26,30], the meniscus instability actually does not develop during such extremely local flow.…”

“…However, this characteristic length is smaller than the wavelength (w85 nm) of the initial perturbation of the meniscus instability for Vit 1 bulk MGs [21,26]. According to the ductile-to-brittle criterion for fracture of MGs [21,26,30], the meniscus instability actually does not develop during such extremely local flow. Moreover, with the attendant long-range correlated plastic flow in nanoscale, the peak profiles also display very weak-fractal character with the dimension of about 1.05.…”

“…Based on a broad overview of fracture patterns [21,22,26], we have previously proposed that the NPC forms via periodically activation of tension transformation zones (TTZs) with local plastic flow in the background ahead of the crack tip. The TTZ can be envisioned as a transient transition from a STZ that experiences significant tension/dilatation fracture [21,24,26].…”

“…The TTZ can be envisioned as a transient transition from a STZ that experiences significant tension/dilatation fracture [21,24,26]. Compared to a STZ being the elementary process of ductile cracking, a TTZ can be regarded as the basis of brittle "quasi-cleavage" fracture through which energy dissipates mainly by forming new surfaces and little by accompanying weaker plastic flow.…”

Analysis of the three-dimensional TGS crystal spatial inhomogeneity of the fractal structure

“…In principle, material-based investigations were dominated by the two-dimensional studies of static effects. However, quasi-dynamical effects and three dimensional phenomena, including crack instabilities in ductile fractures systems [35], were studied in bulk metallic glasses (BMG) in order to analyze a plastic flow at microscale [36] and in order to observe periodic corrugations [37] using a high-velocity plate impact, Atomic Force Microscopy (AFM) recording of profiles, Detrended Fluctuation Analysis (DFA), simulations of Hurst exponents and calculations of diffusive dimensions.…”