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Title: Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. Finally, the present research will broaden the applications of ferritic alloys to higher temperatures.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6] ;  [1] ;  [1] ;  [7] ;  [4] ;  [1] ;  [3] ;  [3] ;  [2] ;  [3] ;  [1]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Tohoku Univ., Sendai (Japan)
  3. Northwestern Univ., Evanston, IL (United States)
  4. Univ. of California, Berkeley, CA (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  7. City Univ. of Hong Kong (Hong Kong)
Publication Date:
OSTI Identifier:
1259493
Grant/Contract Number:
AC52-06NA-25396; FE0005868; 09NT0008089; FE-0011194; FE-0024054
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 5; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE