Effect of tungsten crystallographic orientation on He-ion-induced surface morphology changes

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2013.09.045· OSTI ID:1154776

Parish, Chad M ^[1]; Hijazi, Hussein Dib ^[1]; Meyer, III, Harry M ^[1]; Meyer, Fred W ^[1]

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1. ORNL

In order to study the early stages of nanofuzz growth in fusion-plasma-facing tungsten, mirror-polished high-purity tungsten was exposed to 80 eV helium at 1130 C to a fluence of 4 1024 He/m2. The previously smooth surface shows morphology changes, and grains form one of four qualitatively different morphologies: smooth, wavy, pyramidal, or terraced/wide waves. Combining high-resolution scanning electron microscopy (SEM) observations to determine the morphology of each grain with quantitative measurement of the grain's orientation via electron backscatter diffraction (EBSD) in SEM shows that the normal-direction crystallographic orientation of the underlying grain controls the growth morphology. Specifically, near-<001> || normal direction (ND) grains formed pyramids, near-<114> to <112> || ND grains formed wavy and stepped structures, and near-<103> || ND grains remained smooth. Comparisons to control specimens indicate no changes to underlying bulk crystallographic texture, and the effects are attributed to surface energy anisotropy, although, surprisingly, the expected {101} low-energy planes were not the most stable. Future developments to control tungsten texture via thermomechanical processing, ideally obtaining a sharp near- <103> || ND processing texture, may delay the formation of nanofuzz.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Multicharged Ion Research Facility (MIRF)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1154776
• Journal Information: Acta Materialia, Vol. 62; ISSN 1359-6454
• Country of Publication: United States
• Language: English