Title: Interfacial diffusion aided deformation during nanoindentation

Abstract

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:

Samanta, Amit; E, Weinan

Publication Date:

Fri Jul 01 00:00:00 EDT 2016

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1260431

Alternate Identifier(s):

OSTI ID: 1305905; OSTI ID: 1421195

Report Number(s):

LLNL-JRNL-676455
Journal ID: ISSN 2158-3226

Grant/Contract Number:  

AC52-07NA27344; SC0009248

Resource Type:

Published Article

Journal Name:

AIP Advances

Additional Journal Information:

Journal Name: AIP Advances Journal Volume: 6 Journal Issue: 7; Journal ID: ISSN 2158-3226

Publisher:

American Institute of Physics

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; vacancies; hardness; nanotechnology; diffusion; dislocations