scholarly journals Signature of local stress states in the deformation behavior of metallic glasses

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Xilei Bian ◽  
Daniel Şopu ◽  
Gang Wang ◽  
Baoan Sun ◽  
Jozef Bednarčik ◽  
...  
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Level Structure ◽  
Local Stress ◽  
Atomic Level ◽  
Range Order ◽  
Atomic Scale ◽  
Activation Process ◽  
Eshelby Inclusion ◽  
Stress States

Abstract The design of ductile heterogeneous metallic glasses (MGs) with enhanced deformability by purposely controlling the shear-band dynamics via modulation of the atomic-scale structures and local stress states remains a significant challenge. Here, we correlate the changes in the local atomic structure when cooling to cryogenic temperature with the observed improved shear stability. The enhanced atomic-level structural and elastic heterogeneities related to the nonaffine thermal contraction of the short-range order (SRO) and medium-range order (MRO) change the characteristics of the activation process of the shear transformation zones (STZs). The experimental observations corroborated by Eshelby inclusion analysis and molecular dynamics simulations disclose the correlation between the structural fluctuations and the change in the stress field around the STZ. The variations in the inclination axes of the STZs alter their percolation mechanism, affect the shear-band dynamics and kinetics, and consequently delay shear failure. These results expand the understanding of the correlation between the atomic-level structure and elementary plastic events in monolithic MGs and thereby pave the way for the design of new ductile metallic alloys.

Atomic-Level Processes of Shear Band Nucleation in Metallic Glasses

2017 ◽  
Vol 119 (19) ◽  
Author(s):  
D. Şopu ◽  
A. Stukowski ◽  
M. Stoica ◽  
S. Scudino
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Atomic Level

scholarly journals Atomic level structure of Ge-Sb-S glasses: Chemical short range order and long Sb-S bonds

2019 ◽  
Vol 774 ◽  
pp. 1009-1016 ◽  
Author(s):  
I. Pethes ◽  
V. Nazabal ◽  
J. Ari ◽  
I. Kaban ◽  
J. Darpentigny ◽  
...  
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Level Structure ◽  
Atomic Level ◽  
Range Order

The nature of the atomic-level structure in the Cu–Zr binary metallic glasses

2012 ◽  
Vol 26 ◽  
pp. 8-10 ◽  
Author(s):  
Z.D. Sha ◽  
H. Pan ◽  
Q.X. Pei ◽  
Y.W. Zhang
Keyword(s):  
Metallic Glasses ◽  
Level Structure ◽  
Atomic Level ◽  
Binary Metallic Glasses

scholarly journals Dilatancy induced ductile–brittle transition of shear band in metallic glasses

2018 ◽  
Vol 474 (2212) ◽  
pp. 20170836 ◽  
Author(s):  
F. Zeng ◽  
M. Q. Jiang ◽  
L. H. Dai
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Shear Failure ◽  
Scaling Law ◽  
Shear Banding ◽  
Structural Evolution ◽  
Atomic Scale ◽  
Serrated Flow ◽  
Brittle Transition ◽  
Evolution Dynamics

Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile–brittle transition of shear banding is controlled by a critical dilatation.

Atomic-scale origin of shear band multiplication in heterogeneous metallic glasses

2020 ◽  
Vol 178 ◽  
pp. 57-61 ◽  
Author(s):  
D. Şopu ◽  
S. Scudino ◽  
X.L. Bian ◽  
C. Gammer ◽  
J. Eckert
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Atomic Scale

scholarly journals On the question of fractal packing structure in metallic glasses

2017 ◽  
Vol 114 (32) ◽  
pp. 8458-8463 ◽  
Author(s):  
Jun Ding ◽  
Mark Asta ◽  
Robert O. Ritchie
Keyword(s):  
Metallic Glasses ◽  
Amorphous Materials ◽  
Level Structure ◽  
Atomic Scale ◽  
Structure Property ◽  
Packing Structure ◽  
Structure Property Relationships ◽  
Fractal Models ◽  
Percolation Clusters ◽  
Compositional Variations

This work addresses the long-standing debate over fractal models of packing structure in metallic glasses (MGs). Through detailed fractal and percolation analyses of MG structures, derived from simulations spanning a range of compositions and quenching rates, we conclude that there is no fractal atomic-level structure associated with the packing of all atoms or solute-centered clusters. The results are in contradiction with conclusions derived from previous studies based on analyses of shifts in radial distribution function and structure factor peaks associated with volume changes induced by pressure and compositional variations. The interpretation of such shifts is shown to be challenged by the heterogeneous nature of MG structure and deformation at the atomic scale. Moreover, our analysis in the present work illustrates clearly the percolation theory applied to MGs, for example, the percolation threshold and characteristics of percolation clusters formed by subsets of atoms, which can have important consequences for structure–property relationships in these amorphous materials.

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