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Title: Interfacial diffusion aided deformation during nanoindentation

Nanoindentation is commonly used to quantify the mechanical response of material surfaces. Despite its widespread use, a detailed understanding of the deformation mechanisms responsible for plasticity during these experiments has remained elusive. Nanoindentation measurements often show stress values close to a material’s ideal strength which suggests that dislocation nucleation and subsequent dislocation activity dominates the deformation. However, low strain-rate exponents and small activation volumes have also been reported which indicates high temperature sensitivity of the deformation processes. Using an order parameter aided temperature accelerated sampling technique called adiabatic free energy dynamics [J. B. Abrams and M. E. Tuckerman, J. Phys. Chem. B, 112, 15742 (2008)], and molecular dynamics we have probed the diffusive mode of deformation during nanoindentation. Localized processes such as surface vacancy and ad-atom pair formation, vacancy diffusion are found to play an important role during indentation. Furthermore, our analysis suggests a change in the dominant deformation mode from dislocation mediated plasticity to diffusional flow at high temperatures, slow indentation rates and small indenter tip radii.
Authors:
 [1] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physics Div.
  2. Peking Univ., Beijing (China). BICMR and School of Mathematical Sciences; Princeton Univ., Princeton, NJ (United States). Dept of Mathematics and Program in Applied and Computational Mathematics
Publication Date:
Report Number(s):
LLNL-JRNL-676455
Journal ID: ISSN 2158-3226
Grant/Contract Number:
AC52-07NA27344; SC0009248
Type:
Published Article
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 6; Journal Issue: 7; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; vacancies; hardness; nanotechnology; diffusion; dislocations
OSTI Identifier:
1260431
Alternate Identifier(s):
OSTI ID: 1305905