Influence of processing on the microstructure and mechanical properties of 14YWT

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Abstract

The investigation of the mechanical alloying (MA) conditions for producing the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy led to significant improvements in balancing the strength, ductility and fracture toughness properties while still maintaining the salient microstructural features consisting of ultra-fine grains and high concentration of Y-, Ti- and O-enriched nanoclusters. The implemented changes to the processing conditions included reducing the contamination of the powder during ball milling, applying a pre-extrusion annealing treatment on the ball milled powder and exploring different extrusion temperatures at 850 °C (SM170 heat), 1000 °C (SM185) and 1150 °C (SM200). The microstructural studies of the three 14YWT heats showed similarities in the dispersion of nanoclusters and sub-micron size grains, indicating the microstructure was insensitive to the different extrusion conditions. Compared to past 14YWT heats, the three new heats showed lower strength, but higher ductility levels between 25 and 800 °C and significantly higher fracture toughness values between 25 °C and 700 °C. The lower contamination levels of O, C and N achieved with improved ball milling conditions plus the slightly larger grain size were identified as important factors for improving the balance in mechanical properties of the three heats of 14YWT.

Original languageEnglish
Pages (from-to)251-265
Number of pages15
JournalJournal of Nuclear Materials
Volume471
DOIs
StatePublished - Apr 1 2016

Funding

The authors acknowledge G.R. Odette and S.A. Maloy for their valuable discussions with regards to the continued development of the advanced ODS 14YWT ferritic alloy and would like to thank D.C Harper, D.W. Coffey, T. Geer and E.T. Manneschmidt for assistance with the experimental work. Research at Oak Ridge National Laboratory (ORNL) was sponsored by the Office of Nuclear Energy, Science and Technology . Microscopy was supported through a user proposal by ORNL's Center for Nanophase Materials Science (CNMS) , which is a U.S. Department of Energy, Office of Science User Facility . This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

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