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Title: Ideal maximum strengths and defect-induced softening in nanocrystalline-nanotwinned metals

Abstract

Strengthening of metals through nanoscale grain boundaries and coherent twin boundaries is manifested by a maximum strength—a phenomenon known as Hall–Petch breakdown. Different softening mechanisms are considered to occur for nanocrystalline and nanotwinned materials. Here, we report nanocrystalline-nanotwinned Ag materials that exhibit two strength transitions dissimilar from the above mechanisms. Atomistic simulations show three distinct strength regions as twin spacing decreases, delineated by positive Hall–Petch strengthening to grain-boundary-dictated (near-zero Hall–Petch slope) mechanisms and to softening (negative Hall–Petch slope) induced by twin-boundary defects. An ideal maximum strength is reached for a range of twin spacings below 7 nm. We synthesized nanocrystalline-nanotwinned Ag with hardness 3.05 GPa—42 higher than the current record, by segregating trace concentrations of Cu impurity (< 1.0 weight (wt)%). The microalloy retains excellent electrical conductivity and remains stable up to 653 K; 215 K better than for pure nanotwinned Ag. In conclusion, this breaks the existing trade-off between strength and electrical conductivity, and demonstrates the potential for creating interface-dominated materials with unprecedented mechanical and physical properties.

Authors:
 [1]; ORCiD logo [2];  [1]; ORCiD logo [3];  [3];  [2];  [4];  [5];  [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Vermont, Burlington, VT (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Ames Lab., Ames, IA (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1572616
Alternate Identifier(s):
OSTI ID: 1573490
Report Number(s):
LLNL-JRNL-680480; IS-J 10070
Journal ID: ISSN 1476-1122; 804569
Grant/Contract Number:  
AC52-07NA27344; SC0016270; AC02-07CH11358; AC52-06NA253; DMR-1611342
Resource Type:
Accepted Manuscript
Journal Name:
Nature Materials
Additional Journal Information:
Journal Volume: 18; Journal Issue: 11; Journal ID: ISSN 1476-1122
Publisher:
Springer Nature - Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Ke, Xing, Ye, Jianchao, Pan, Zhiliang, Geng, Jie, Besser, Matt F., Qu, Dongxia, Caro, Alfredo, Marian, Jaime, Ott, Ryan T., Wang, Y. Morris, and Sansoz, Frederic. Ideal maximum strengths and defect-induced softening in nanocrystalline-nanotwinned metals. United States: N. p., 2019. Web. doi:10.1038/s41563-019-0484-3.
Ke, Xing, Ye, Jianchao, Pan, Zhiliang, Geng, Jie, Besser, Matt F., Qu, Dongxia, Caro, Alfredo, Marian, Jaime, Ott, Ryan T., Wang, Y. Morris, & Sansoz, Frederic. Ideal maximum strengths and defect-induced softening in nanocrystalline-nanotwinned metals. United States. doi:10.1038/s41563-019-0484-3.
Ke, Xing, Ye, Jianchao, Pan, Zhiliang, Geng, Jie, Besser, Matt F., Qu, Dongxia, Caro, Alfredo, Marian, Jaime, Ott, Ryan T., Wang, Y. Morris, and Sansoz, Frederic. Mon . "Ideal maximum strengths and defect-induced softening in nanocrystalline-nanotwinned metals". United States. doi:10.1038/s41563-019-0484-3.
@article{osti_1572616,
title = {Ideal maximum strengths and defect-induced softening in nanocrystalline-nanotwinned metals},
author = {Ke, Xing and Ye, Jianchao and Pan, Zhiliang and Geng, Jie and Besser, Matt F. and Qu, Dongxia and Caro, Alfredo and Marian, Jaime and Ott, Ryan T. and Wang, Y. Morris and Sansoz, Frederic},
abstractNote = {Strengthening of metals through nanoscale grain boundaries and coherent twin boundaries is manifested by a maximum strength—a phenomenon known as Hall–Petch breakdown. Different softening mechanisms are considered to occur for nanocrystalline and nanotwinned materials. Here, we report nanocrystalline-nanotwinned Ag materials that exhibit two strength transitions dissimilar from the above mechanisms. Atomistic simulations show three distinct strength regions as twin spacing decreases, delineated by positive Hall–Petch strengthening to grain-boundary-dictated (near-zero Hall–Petch slope) mechanisms and to softening (negative Hall–Petch slope) induced by twin-boundary defects. An ideal maximum strength is reached for a range of twin spacings below 7 nm. We synthesized nanocrystalline-nanotwinned Ag with hardness 3.05 GPa—42 higher than the current record, by segregating trace concentrations of Cu impurity (< 1.0 weight (wt)%). The microalloy retains excellent electrical conductivity and remains stable up to 653 K; 215 K better than for pure nanotwinned Ag. In conclusion, this breaks the existing trade-off between strength and electrical conductivity, and demonstrates the potential for creating interface-dominated materials with unprecedented mechanical and physical properties.},
doi = {10.1038/s41563-019-0484-3},
journal = {Nature Materials},
number = 11,
volume = 18,
place = {United States},
year = {2019},
month = {9}
}

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Works referenced in this record:

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Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
journal, October 1996