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Title: High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy

Abstract

Precipitates of the Laves and B2 phases were engineered in a newly-designed advanced ferritic alloy. Under creep test at 650 °C with 120 MPa, the material showed a steady-state minimum creep rate of 1 × 10 –4 h –1, about one order of magnitude lower than T91. Microstructural characterization of the ferritic alloy revealed primarily ductile and partially brittle fractures after the creep test. Coarse Laves phase (~ 1 µm) was observed associating with the brittle fracture, resulting in reduced creep ductility. However, fine Laves phase precipitates (~ 100 nm) helped the dimple-ductile fracture and strengthened the material through impeding the motion of dislocations and boundaries. Unlike the B2 precipitates remained coherent exerting the classic Orowan bypassing mechanism at the brittle location, some of the B2 precipitates at the ductile location became incoherent and can develop an attractive interaction with dislocations. In conclusion, this coherency change of B2 precipitates, together with the nucleation of ultrafine (~ 40 nm) Laves phase precipitates during the creep test, would compensate for the coarsening-induced loss of Orowan strengthening of coherent B2 precipitates.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1465062
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 720; Journal Issue: C; Journal ID: ISSN 0921-5093
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Creep; Fracture; Microstructure; Dislocation; Orowan strengthening; Precipitation strengthening

Citation Formats

Chen, Tianyi, Parish, Chad M., Yang, Ying, and Tan, Lizhen. High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy. United States: N. p., 2018. Web. doi:10.1016/j.msea.2018.02.013.
Chen, Tianyi, Parish, Chad M., Yang, Ying, & Tan, Lizhen. High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy. United States. doi:10.1016/j.msea.2018.02.013.
Chen, Tianyi, Parish, Chad M., Yang, Ying, and Tan, Lizhen. Wed . "High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy". United States. doi:10.1016/j.msea.2018.02.013. https://www.osti.gov/servlets/purl/1465062.
@article{osti_1465062,
title = {High-temperature strengthening mechanisms of Laves and B2 precipitates in a novel ferritic alloy},
author = {Chen, Tianyi and Parish, Chad M. and Yang, Ying and Tan, Lizhen},
abstractNote = {Precipitates of the Laves and B2 phases were engineered in a newly-designed advanced ferritic alloy. Under creep test at 650 °C with 120 MPa, the material showed a steady-state minimum creep rate of 1 × 10–4 h–1, about one order of magnitude lower than T91. Microstructural characterization of the ferritic alloy revealed primarily ductile and partially brittle fractures after the creep test. Coarse Laves phase (~ 1 µm) was observed associating with the brittle fracture, resulting in reduced creep ductility. However, fine Laves phase precipitates (~ 100 nm) helped the dimple-ductile fracture and strengthened the material through impeding the motion of dislocations and boundaries. Unlike the B2 precipitates remained coherent exerting the classic Orowan bypassing mechanism at the brittle location, some of the B2 precipitates at the ductile location became incoherent and can develop an attractive interaction with dislocations. In conclusion, this coherency change of B2 precipitates, together with the nucleation of ultrafine (~ 40 nm) Laves phase precipitates during the creep test, would compensate for the coarsening-induced loss of Orowan strengthening of coherent B2 precipitates.},
doi = {10.1016/j.msea.2018.02.013},
journal = {Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing},
issn = {0921-5093},
number = C,
volume = 720,
place = {United States},
year = {2018},
month = {2}
}

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