For decades, scanning/transmission electron microscopy (S/TEM) techniques have been employed to analyze shear bands in metallic glasses and understand their formation in order to improve the mechanical properties of metallic glasses. However, due to a lack of direct information in reciprocal space, conventional S/TEM cannot characterize the local strain and atomic structure of amorphous materials, which are key to describe the deformation of glasses. For this work, 4-dimensional-STEM (4D-STEM) is applied to map and directly correlate the local strain and the atomic structure at the nanometer scale in deformed metallic glasses. Residual strain fields are observed with quadrupolar symmetry concentrated at dilated Eshelby inclusions. The strain fields percolate in a vortex-like manner building up the shear band. This provides a new understanding of the formation of shear bands in metallic glass.
With the pace of miniaturization, investigating the mechanical properties of small objects and understanding their mechanism have been an urging task. However, developing mechanical tensile testing techniques and methodologies at micro-and nanoscale is challenging. Micro-and nanoscale tensile testing differs in comparison with other methods in that the interpretation of the data is relatively straightforward but the technical hurdles are high.Two main challenges have to be mastered during tensile tests at small dimensions. One is the handling of extremely small specimens. The other is the requirements on force/displacement measurements. Here we use a Focus Ion Beam Microscope (FIB) with a micromanipulator to handle small specimens such as copper and silver sub-micro-wires. Force/displacement measurements were performed using Atomic Force Microscope (AFM) cantilevers. They are sensitive load sensors and can provide high accuracy of force measurement. By changing the different AFM cantilevers, a large range of force measurement can be achieved. The experiment set-up is shown in Figure 1. In our experiments the loading was applied continuously and the Scanning Electron Microscope (SEM) images were recorded in real-time using the movie tool. By analyzing the sequential snapshot images from the movie, the stress and strain curves could be drawn (Fig. 2).In order to understand the mechanism of deformation and the mechanical properties at small scale, the investigations of the microstructure in materials before, after and during tensile tests are essential. Transmission Electron Microscopy (TEM) was performed to explore the microstructures at atomic scale. Figure 3 shows the microstructure change of silver wires before and after the tensile test. The results clearly show the stacking faults and twin boundaries are introduced into original single crystal silver wires. The mechanical properties of the metal nanowires strongly depend on their original microstructure and changes after the mechanical deformation.Here, we demonstrate that combining different microscopy techniques (AFM, SEM, FIB, and TEM) is an efficient way to analyze the mechanical properties of metal nanowires. A novel and simple technique to measure the mechanical material properties of small metal wires was developed. This method can be easily applied to vast ranges of materials from normal metals to bio-materials such as feathers and hairs etc. TEM was used to investigate the microstructure change of metal nanowires before, after, and during mechanical tests. The results suggest that their mechanical properties strongly depend on their microstructures and microstructural changes due to deformation.
Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.
Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.