Experimental studies of shear bands in Zr-Cu metallic glass

Abstract

Shear bands are the key feature that controls deformation in bulk metallic glasses (BMGs). This study provides a comprehensive analysis of plastic deformation of a Zr-Cu-based BMG at room temperature. Experiments were conducted to observe the evolution of shear bands in the material. It was shown that shear bands formed discretely in the material which allows for material deformation to occur across it. Additionally, individual shear bands were characterised to obtain a better understanding of shear-band-induced plasticity. Assessment of mechanical properties, such as hardness and elastic modulus, indicate the deformed regions of the material were weaker than undeformed regions. No compositional or structural changes were found in shear-band of the studied BMG suggesting generation of local free volume in the deformed region.

Experimental and computational analysis of initiation and propagation of shear bands in bulk metallic glasses

“…TEM studies showed that only broad amorphous peaks were present and no indication of crystalinity was found through the presence of Bragg's peaks (see Nekouie et al 2018). As reported by Nekouie et al dark field TEM images also confirmed the absence of crystalline phases in the sample and Selected Area Diffraction (SAED) pattern showed only a set of diffused rings typical for an amorphous structure of glassy nature.…”

“…Figure 7(c) shows that SBs are not initiated on a plane that lies along the length of the wedge indenter. This was observed in our experiments as on (Nekouie et al 2018). The effect of strain gradients on the initiation and propagation of SBs were studied and the load-displacement curves for different length parameters (l) were compared with the experiment.…”

“…Similar approach was considered by (Yu et al 2017) to simulate rolling on BMGs, though the plasticity model was not analogous to us. These weak-sites defined the fluctuation of free volume or chemical heterogeneity of the BMG specimen and controlled the energy barrier of SBs (Nekouie et al 2018). As reported by Nekouie (Nekouie et al 2018), SBs are mostly initiated from these weak sites.…”

“…In present work an alternative technique based on a phenomenological constitutive model to predict the initiation and propagation of SBs originating beneath the indenter is presented. The approach is able to capture the initiation and propagation of the SBs in BMGs adequately (detailed experimental work is available in (Nekouie et al 2018)). The model based on the experimental observation of Nekouie et al has provided new insights into SB initiation and propagation in Zr-Cu based BMGs under inhomogeneous loading conditions.…”

Shear Localization and Mechanical Properties of Cu/Ta Metallic Nanolayered Composites: A Molecular Dynamics Study

“…However, the plastic instability of Cu matrix MNCs produced by their shear localization severely disrupts the ability of the material to deform uniformly, limiting its application [5][6][7][8][9]. To effectively control this instability, the process of shear bands (SBs) formation in Cu matrix MNCs needs to be explored.…”