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In Situ Electron Microscopy of Helium Bubble Implantation in Metal Hydrides

Hattar, Khalid M.; Bufford, Daniel C.; Robinson, David; Snow, Clark S.

Here we investigated the microstructural response of various Pd physically vapor deposited films and Er and ErD2 samples prepared from neutron Tube targets to implanted He via in situ ion irradiation transmission electron microscopy and subsequent in situ annealing experiments. Small bubbles formed in both systems during implantation, but did not grow with increasing fluence or a short duration room temperature aging (weeks). Annealing produced large cavities with different densities in the two systems. The ErD2 showed increased cavity nucleation compared to Er. The spherical bubbles formed from high fluence implantation and rapid annealing in both Er and ErD2 cases differed from microstructures of naturally aged tritiated samples. Further work is still underway to determine the transition in bubble shape in the Er samples, as well as the mechanism for evolution in Pd films.

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TYPE Other Report YEAR 2014
DOIOSTI

Anisotropic radiation-induced segregation in 316L austenitic stainless steel with grain boundary character

Acta Materialia

Barr, Christopher M.; Vetterick, Gregory A.; Unocic, Kinga A.; Hattar, Khalid M.; Bai, Xian M.; Taheri, Mitra L.

Radiation-induced segregation (RIS) and subsequent depletion of chromium along grain boundaries has been shown to be an important factor in irradiation-assisted stress corrosion cracking in austenitic face-centered cubic (fcc)-based alloys used for nuclear energy systems. A full understanding of RIS requires examination of the effect of the grain boundary character on the segregation process. Understanding how specific grain boundary structures respond under irradiation would assist in developing or designing alloys that are more efficient at removing point defects, or reducing the overall rate of deleterious Cr segregation. This study shows that solute segregation is dependent not only on grain boundary misorientation, but also on the grain boundary plane, as highlighted by markedly different segregation behavior for the Σ3 incoherent and coherent grain boundaries. The link between RIS and atomistic modeling is also explored through molecular dynamic simulations of the interaction of vacancies at different grain boundary structures through defect energetics in a simple model system. A key insight from the coupled experimental RIS measurements and corresponding defect-grain boundary modeling is that grain boundary-vacancy formation energy may have a critical threshold value related to the major alloying elements' solute segregation. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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TYPE Journal Article YEAR 2014
ScopusOSTI
Results 451–475 of 613
Results 451–475 of 613