Erich Stergar

Profile Information
Name
Erich Stergar
Institution
University of California-Berkeley
Publications:
"Atom probe tomography analysis of high dose MA957 at selected irradiation temperatures" Nathan Bailey, Peter Hosemann, Erich Stergar, Mychailo Toloczko, Journal of Nuclear Materials Vol. 459 2015 225-234 Link
Oxide dispersion strengthened (ODS) alloys are meritable structural materials for nuclear reactor systems due to the exemplary resistance to radiation damage and high temperature creep. Summarized in this work are atom probe tomography (APT) investigations on a heat of MA957 that underwent irradiation in the form of in-reactor creep specimens in the Fast Flux Test Facility–Materials Open Test Assembly (FFTF–MOTA) for the Liquid Metal Fast Breeder Reactor (LMFBR) program. The oxide precipitates appear stable under irradiation at elevated temperature over extended periods of time. Nominally, the precipitate chemistry is unchanged by the accumulated dose; although, evidence suggests that ballistic dissolution and reformation processes are occurring at all irradiation temperatures. At 412 °C–109 dpa, chromium enrichments – consistent with the a' phase – appear between the oxide precipitates, indicating radiation induced segregation. Grain boundaries, enriched with several elements including nickel and titanium, are observed at all irradiation conditions. At 412 °C–109 dpa, the grain boundaries are also enriched in molecular titanium oxide (TiO).
"Characterization of (Ti,Mo,Cr)C nanoprecipitates in an austenitic stainless steel on the atomic scale" Niels Cautaerts, Remi Delville, Erich Stergar, Marc Verwerft, Acta Materialia Vol. 164 2018 90-98 Link
"Twin boundary-accelerated ferritization of austenitic stainless steels in liquid lead–bismuth eutectic" David Frazer, Peter Hosemann, Konstantina Lambrinou, Erich Stergar, Scripta Materialia Vol. 118 2016 37-40 Link
Exposure of austenitic stainless steels to liquid lead-bismuth eutectic with low concentration of dissolved oxygen typically results in selective leaching of highly-soluble alloying elements and ferritization of the dissolution-affected zone. In this work, focused ion beam, transmission electron backscatter diffraction and scanning transmission electron microscopy were utilised to elucidate early-stage aspects of the dissolution corrosion process of cold-worked austenitic stainless steels exposed to static, oxygen-poor liquid lead-bismuth eutectic at 450C for 1000 hours. It was found that deformation-induced twin boundaries in the cold-worked steel bulk provide paths of accelerated penetration of the liquid metal into the steel bulk.