Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 52, Pages 13631-13636Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1708618114
Keywords
creep; molecular simulation; deformation mechanism; atomistic modeling; metallic glass
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Funding
- US Department of Energy (DOE) [DE-NE0008450]
- National Science Foundation CAREER [DMR-1654548]
- DOE-Basic Energy Sciences [DE-SC0002633]
- Kuwait-MIT Center Signature Project
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Molecular processes of creep in metallic glass thin films are simulated at experimental timescales using a metadynamics-based atomistic method. Space-time evolutions of the atomic strains and nonaffine atom displacements are analyzed to reveal details of the atomic-level deformation and flow processes of amorphous creep in response to stress and thermal activations. From the simulation results, resolved spatially on the nanoscale and temporally over time increments of fractions of a second, we derive a mechanistic explanation of the well-known variation of creep rate with stress. We also construct a deformation map delineating the predominant regimes of diffusional creep at low stress and high temperature and deformational creep at high stress. Our findings validate the relevance of two original models of the mechanisms of amorphous plasticity: one focusing on atomic diffusion via free volume and the other focusing on stress-induced shear deformation. These processes are found to be nonlinearly coupled through dynamically heterogeneous fluctuations that characterize the slow dynamics of systems out of equilibrium.
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