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Characterization of 14YWT As-Atomized, Milled, Milled and Annealed Powders and HIP Consolidated Alloys

Published online by Cambridge University Press:  09 March 2011

Nicholas J. Cunningham ,
Auriane Etienne ,
G. Robert Odette ,
Erich Stergar ,
Yuan Wu  and
Brian D. Wirth
Nicholas J. Cunningham
Affiliation:
University of California, Santa Barbara, CA 93106, U.S.A.
Auriane Etienne
Affiliation:
University of California, Santa Barbara, CA 93106, U.S.A.
G. Robert Odette
Affiliation:
University of California, Santa Barbara, CA 93106, U.S.A.
Erich Stergar
Affiliation:
University of California, Santa Barbara, CA 93106, U.S.A.
Yuan Wu
Affiliation:
University of California, Santa Barbara, CA 93106, U.S.A.
Brian D. Wirth
Affiliation:
University of Tennessee, Knoxville, TN 37996, U.S.A.
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Abstract

Nanostructured ferritic alloys (NFA) are Fe-Cr based ferritic stainless steels containing an ultrahigh density of very stable Y-Ti-O nanofeatures (NFs) that provide dispersion strengthening and radiation damage resistance for candidate Generation IV and future fusion reactor materials. This work is a small and focused part of a larger collaboration to produce large best practice NFA heats. The powders analyzed were rapidly solidified from a melt containing Fe-14%Cr, 3%W, 0.4%Ti and 0.2%Y by gas atomization in Ar, Ar/O, and He atmospheres. Note this represents a different processing path from conventional NFA production where metallic powders are mechanically alloyed with Y2O3 by ball milling. Electron probe microanalysis (EPMA), atom probe tomography (APT), transmission electron microscopy (TEM) and small angle neutron scattering (SANS) were used to characterize the powders in the as-atomized, ball milled and ball milled and annealed conditions. EPMA showed the Y is heterogeneously distributed and phase separated in all the as atomized powders, but attritor milling for 20 to 40 h is required to mix the Y. Milling also creates a significant quantity of O as well as N contamination. Subsequent powder annealing treatments, typically at 1150°C, result in the precipitation of a high density of NFs. All the annealed powder variants show a bimodal grain size distribution, but TEM and APT show NFs in both large and small grains. Reducing O content added during milling of the Ar atomized powders increased the precipitate size and decreased the number density, adversely affecting the hardness.

Keywords

mechanical alloyingpowder processingnuclear materials
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1298: Symposium Q/R/T – Advanced Materials for Applications in Extreme Environments , 2011 , mrsf10-1298-q02-02
Copyright
Copyright © Materials Research Society 2011

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References

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