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This content will become publicly available on June 28, 2017

Title: High cycle fatigue in the transmission electron microscope

One of the most common causes of structural failure in metals is fatigue induced by cyclic loading. Historically, microstructure-level analysis of fatigue cracks has primarily been performed post mortem. However, such investigations do not directly reveal the internal structural processes at work near micro- and nanoscale fatigue cracks and thus do not provide direct evidence of active microstructural mechanisms. In this paper, the tension–tension fatigue behavior of nanocrystalline Cu was monitored in real time at the nanoscale by utilizing a new capability for quantitative cyclic mechanical loading performed in situ in a transmission electron microscope (TEM). Controllable loads were applied at frequencies from one to several hundred hertz, enabling accumulations of 106 cycles within 1 h. The nanometer-scale spatial resolution of the TEM allows quantitative fatigue crack growth studies at very slow crack growth rates, measured here at ~10–12 m·cycle–1. This represents an incipient threshold regime that is well below the tensile yield stress and near the minimum conditions for fatigue crack growth. Evidence of localized deformation and grain growth within 150 nm of the crack tip was observed by both standard imaging and precession electron diffraction orientation mapping. Finally, these observations begin to reveal with unprecedented detail the localmore » microstructural processes that govern damage accumulation, crack nucleation, and crack propagation during fatigue loading in nanocrystalline Cu.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Hysitron, Inc., Eden Prairie, MN (United States)
Publication Date:
OSTI Identifier:
1271014
Report Number(s):
SAND2016--6822J
Journal ID: ISSN 1530-6984; 645284
Grant/Contract Number:
AC04-94AL85000; FG02-04ER83979; FG02-07ER84813
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Name: Nano Letters; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Contributing Orgs:
Hysitron, Inc., Eden Prairie, MN (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE crack propagation; fatigue; metals; TEM