The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

Journal Article · Wed Jun 03 00:00:00 EDT 2015 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2015.05.057· OSTI ID:1185761

Mazumder, B. ^[1]; Parish, C. M. ^[1]; Bei, H. ^[1]; Miller, M. K. ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Nanostructured ferritic alloys (NFAs) have outstanding high temperature creep properties and extreme tolerance to radiation damage. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of -Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of -Fe with 50-100 m irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Al5Y3O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These differences can be explained by the differences in the microstructure and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms retarding diffusion.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1185761
• Alternate ID(s): OSTI ID: 1251986
• Journal Information: Journal of Nuclear Materials, Vol. 465, Issue C; ISSN 0022-3115
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE