On the structure and chemistry of complex oxide nanofeatures in nanostructured ferritic alloy U14YWT |
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| Authors: | D Bhattacharyya P Dickerson GR Odette SA Maloy A Misra MA Nastasi |
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| Institution: | 1. Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos , NM 87545 , USA dhriti1@gmail.com dhriti.bhattacharyya@ansto.gov.au;3. MST-6, Metallurgy Division, Los Alamos National Laboratory , Los Alamos , NM 87545 , USA;4. Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , CA , USA;5. MST-8, Structure-Property Correlations, Los Alamos National Laboratory , Los Alamos , NM 87545 , USA;6. Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos , NM 87545 , USA |
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| Abstract: | The remarkable radiation damage resistance of nanostructured ferritic alloys (NFAs) is attributed to the large numbers of matrix nanofeatures (NFs) of various types, which can enhance the recombination of displacement defects and trap transmutant helium in fine scale bubbles. Characterizing the chemistry, crystallographic structure and orientation relationships of the NFs is critical to understanding how they enhance the radiation damage resistance of NFAs. Conventional and high-resolution transmission electron microscopy and energy-dispersive spectroscopy were used to characterize the various types of NF and larger oxide phases in a model 14Cr–3?W–0.4Ti–0.25Y2O3 NFA (14YWT) hot isostatic pressed (HIP-ed) at 1150°C. Large CrTiO3 precipitates (50–300?nm) and small diffracting NFs (<5?nm) were found in this alloy. One major new result is the observation of an additional type of nanofeature (10–50?nm), orthorhombic in structure, with a square center cross-section, which constitutes a new kind of Y–Ti-oxide phase with lattice parameters different from those of known Y and Ti complex oxides. The interfaces of these particles seem to be semicoherent, while manifesting a possible orientation relationship with the BCC matrix. The ratio of Y to Ti varies between <1 and 2 for these larger NFs. |
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| Keywords: | oxide dispersion strengthened steels nanostructured ferritic alloys TEM yttrium–titanium oxide precipitates |
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