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Title: Stability of binary nanocrystalline alloys against grain growth and phase separation

Abstract

Grain boundary segregation has been established through both simulation and experiments as a successful approach to stabilize nanocrystalline materials against grain growth. However, relatively few alloy systems have been studied in this context; these vary in their efficacy, and in many cases the stabilization effect is compromised by second phase precipitation. We address the open-ended design problem of how to select alloy systems that may be stable in a nanocrystalline state. We continue the development of a general “regular nanocrystalline solution” model to identify the conditions under which binary nanocrystalline alloy systems with positive heats of mixing are stable with respect to both grain growth (segregation removes the grain boundary energy penalty) and phase separation (the free energy of the nanocrystalline system is lower than the common tangent defining the bulk miscibility gap). We calculate a “nanostructure stability map” in terms of alloy thermodynamic parameters. Three main regions are delineated in these maps: one where grain boundary segregation does not result in a stabilized nanocrystalline structure, one in which macroscopic phase separation would be preferential (despite the presence of a nanocrystalline state stable against grain growth) and one for which the nanocrystalline state is stable against both grain growth andmore » phase separation. Additional details about the stabilized structures are also presented in the map, which can be regarded as a tool for the design of stable nanocrystalline alloys.« less

Authors:
 [1];  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Materials Science and Engineering
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1381964
Grant/Contract Number:  
SC0001299
Resource Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 61; Journal Issue: 6; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; nanocrystalline alloys; grain boundary segregation; thermodynamic stability

Citation Formats

Murdoch, Heather A., and Schuh, Christopher A. Stability of binary nanocrystalline alloys against grain growth and phase separation. United States: N. p., 2013. Web. doi:10.1016/j.actamat.2012.12.033.
Murdoch, Heather A., & Schuh, Christopher A. Stability of binary nanocrystalline alloys against grain growth and phase separation. United States. doi:10.1016/j.actamat.2012.12.033.
Murdoch, Heather A., and Schuh, Christopher A. Wed . "Stability of binary nanocrystalline alloys against grain growth and phase separation". United States. doi:10.1016/j.actamat.2012.12.033. https://www.osti.gov/servlets/purl/1381964.
@article{osti_1381964,
title = {Stability of binary nanocrystalline alloys against grain growth and phase separation},
author = {Murdoch, Heather A. and Schuh, Christopher A.},
abstractNote = {Grain boundary segregation has been established through both simulation and experiments as a successful approach to stabilize nanocrystalline materials against grain growth. However, relatively few alloy systems have been studied in this context; these vary in their efficacy, and in many cases the stabilization effect is compromised by second phase precipitation. We address the open-ended design problem of how to select alloy systems that may be stable in a nanocrystalline state. We continue the development of a general “regular nanocrystalline solution” model to identify the conditions under which binary nanocrystalline alloy systems with positive heats of mixing are stable with respect to both grain growth (segregation removes the grain boundary energy penalty) and phase separation (the free energy of the nanocrystalline system is lower than the common tangent defining the bulk miscibility gap). We calculate a “nanostructure stability map” in terms of alloy thermodynamic parameters. Three main regions are delineated in these maps: one where grain boundary segregation does not result in a stabilized nanocrystalline structure, one in which macroscopic phase separation would be preferential (despite the presence of a nanocrystalline state stable against grain growth) and one for which the nanocrystalline state is stable against both grain growth and phase separation. Additional details about the stabilized structures are also presented in the map, which can be regarded as a tool for the design of stable nanocrystalline alloys.},
doi = {10.1016/j.actamat.2012.12.033},
journal = {Acta Materialia},
number = 6,
volume = 61,
place = {United States},
year = {2013},
month = {1}
}

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