The mechanical properties of core–shell bimetallic composite nanowires, forming the bases of nanoporous metallic foams, have been investigated and compared with pure metal nanowires using molecular dynamics simulations. In the current study, pure copper and gold nanowires under uniaxial loading were tested at room temperature and compared to composite nanowires of the same materials (core) with a nickel coating (shell). The core radius ranged from 1 to 15 nm, and the shell thickness ranged from 0.1 to 5 nm. The tension strain was performed along the [001] direction under room temperature. Both coherent and semi-coherent composite nanowires were studied, and the effect of coating layer thickness was investigated. The strengthening mechanisms of the core–shell structures due to the presence of the two different types of interfaces were investigated for various nickel thicknesses. The atomistic simulation results revealed that the addition of the nickel shell strengthens the structure when the layer thickness exceeds a critical value.
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The dynamics of shear band propagation in metallic glasses
Understanding the dynamics of shear band propagation in metallic glasses remains elusive due to the limited
temporal and spatial scales accessible in experiments. In micron-scale molecular dynamics simulations on two
model metallic glasses, we studied the propagation of a dominant shear band under uniaxial tension with a
macroscopic strain of 3-5%. For both materials, the shear band can be intersonic with a propagation speed
exceeding their respective shear wave speeds. The propagation exhibits intrinsic instability that manifests itself
as microbranching and considerable fluctuations in velocity. The shear strain singularity ahead of propagating
shear band tip scales as 1/r (r is the distance away from the tip), independent of the macroscopic tensile strain. In
addition, we studied the intersection of two shear bands under uniaxial tension, during which path deflection,
speed slowing-down, and temperature rise at the junction region were observed. The dynamics of propagating
shear band shown here indicate that shear band in metallic glasses can be viewed as shear crack under the
framework of weakly nonlinear fracture mechanics theory.
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- Award ID(s):
- 1936368
- NSF-PAR ID:
- 10492393
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Acta Materialia
- ISSN:
- 1873-2453
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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