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Title: Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures

Abstract

Technologically important mechanical properties of engineering materials often degrade at low temperatures. One class of materials that defy this trend are CrCoNi-based medium- and high-entropy alloys, as they display enhanced strength, ductility, and toughness with decreasing temperature. Here we show, using in situ straining in the transmission electron microscope at 93 K (–180 °C) that their exceptional damage tolerance involves a synergy of deformation mechanisms, including twinning, glide of partials and full dislocations, extensive cross-slip, and multiple slip activated by dislocation and grain-boundary interactions. In particular, massive cross-slip occurs at the early stages of plastic deformation, thereby promoting multiple slip and dislocation interactions. Furthermore these results indicate that the reduced intensity of thermal activation of defects at low temperatures and the required increase of applied stress for continued plastic flow, together with high lattice resistance, play a pivotal role in promoting the concurrent operation of multiple deformation mechanisms, which collectively enable the outstanding mechanical properties of these alloys.

Authors:
 [1];  [1];  [2]; ORCiD logo [3]; ORCiD logo [4];  [1];  [1]; ORCiD logo [5];  [1];  [2];  [6]
  1. Zhejiang Univ., Hangzhou (China)
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. UNSW Sydney, NSW (Australia)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
  6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1512512
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Materials Today
Additional Journal Information:
Journal Volume: 25; Journal Issue: C; Journal ID: ISSN 1369-7021
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Ding, Qingqing, Fu, Xiaoqian, Chen, Dengke, Bei, Hongbin, Gludovatz, Bernd, Li, Jixue, Zhang, Ze, George, Easo P., Yu, Qian, Zhu, Ting, and Ritchie, Robert O. Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures. United States: N. p., 2019. Web. doi:10.1016/j.mattod.2019.03.001.
Ding, Qingqing, Fu, Xiaoqian, Chen, Dengke, Bei, Hongbin, Gludovatz, Bernd, Li, Jixue, Zhang, Ze, George, Easo P., Yu, Qian, Zhu, Ting, & Ritchie, Robert O. Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures. United States. doi:10.1016/j.mattod.2019.03.001.
Ding, Qingqing, Fu, Xiaoqian, Chen, Dengke, Bei, Hongbin, Gludovatz, Bernd, Li, Jixue, Zhang, Ze, George, Easo P., Yu, Qian, Zhu, Ting, and Ritchie, Robert O. Sat . "Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures". United States. doi:10.1016/j.mattod.2019.03.001.
@article{osti_1512512,
title = {Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures},
author = {Ding, Qingqing and Fu, Xiaoqian and Chen, Dengke and Bei, Hongbin and Gludovatz, Bernd and Li, Jixue and Zhang, Ze and George, Easo P. and Yu, Qian and Zhu, Ting and Ritchie, Robert O.},
abstractNote = {Technologically important mechanical properties of engineering materials often degrade at low temperatures. One class of materials that defy this trend are CrCoNi-based medium- and high-entropy alloys, as they display enhanced strength, ductility, and toughness with decreasing temperature. Here we show, using in situ straining in the transmission electron microscope at 93 K (–180 °C) that their exceptional damage tolerance involves a synergy of deformation mechanisms, including twinning, glide of partials and full dislocations, extensive cross-slip, and multiple slip activated by dislocation and grain-boundary interactions. In particular, massive cross-slip occurs at the early stages of plastic deformation, thereby promoting multiple slip and dislocation interactions. Furthermore these results indicate that the reduced intensity of thermal activation of defects at low temperatures and the required increase of applied stress for continued plastic flow, together with high lattice resistance, play a pivotal role in promoting the concurrent operation of multiple deformation mechanisms, which collectively enable the outstanding mechanical properties of these alloys.},
doi = {10.1016/j.mattod.2019.03.001},
journal = {Materials Today},
number = C,
volume = 25,
place = {United States},
year = {2019},
month = {3}
}

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This content will become publicly available on March 23, 2020
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