Journal
ACTA MATERIALIA
Volume 153, Issue -, Pages 71-85Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2018.04.046
Keywords
ODS ferritic steel; Grain-boundary segregation; Nanoparticles; Atom probe tomography
Funding
- National Research Foundation of Korea (NRF) - Korea government (MSIT) [2018R1A2B6004490]
- MSIT of Korea [2018R1C1B6008585]
- Civil-Military Technology Cooperation Program [17-CM-MA-06]
- Agency for Defense Development (ADD), Republic of Korea [17-CM-MA-06-MKE] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
- National Research Foundation of Korea [2018R1A2B6004490, 2018R1C1B6008585] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Doping with interstitials influences the grain boundary (GB) composition of metallic alloys, enabling changes in elemental GB enrichment, grain size, and mechanical properties or even promoting nanoparticle formation. Yet, little efforts on these doping effects have been made in oxide dispersion-strengthened (ODS) steels. Here, by combining advanced microscopy techniques, we studied the impact of interstitial concentration and extrusion temperature on the GB structure-dependent solute segregation, Y-Ti-O nanofeatures, and mechanical properties of ferritic Fe-14Cr (wt%) ODS steels fabricated by ball milling. We found that doping with high carbon and oxygen contents causes the GB to be decorated with the interstitials and promotes nanoparticle formation along the GBs, thereby retarding capillary-driven grain coarsening. This effect performs twofold, through grain size refinement and particle hardening. For samples with low interstitial contents, altering the extrusion temperature does not significantly change the material's mechanical properties and microstructure or the nonstoichiometric chemistry of nanoparticles, which are highly stable at high temperatures. Further, for all the samples, Y -Al oxides in the initial precipitation stages rapidly become coarsened at high temperatures, as Al weakens the thermal stability of nanoparticles, thereby transforming them to core-shell structures with Y-Al-rich cores and Ti-O-rich shells in the later precipitation stages. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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