David Hoelzer

Profile Information
Dr. David Hoelzer
Oak Ridge National Laboratory
Mechanical Properties
"Advancd TEM characterization of oxide nanoparticles in ODS Fe-12-Cr-5Al alloys" David Hoelzer, Journal of Material Science Vol. 51 2016 9190-9206 Link
"Applications of Combined Transmission Kikuchi Diffraction and STEM-SDD X-Ray Analysis in Irradiated Materials" Chad Parish, Kun Wang, Philip Edmondson, David Hoelzer, Microscopy and Microanalysis Vol. 24 2018 736-737 Link
"Development of low-Cr ODS FeCrAl alloys for accident-tolerant fuel cladding" David Hoelzer, Caleb Massey, Sebastien Dryepondt, Kinga Unocic, Bruce Pint, Journal of Nuclear Materials Vol. 501 2018 59-71 Link
Low-Cr oxide dispersion strengthened (ODS) FeCrAl alloys were developed as accident tolerant fuel cladding because of their excellent oxidation resistance at very high temperature, high strength and improved radiation tolerance. Fe-12Cr-5Al wt.% gas atomized powder was ball milled with Y2O3+FeO, Y2O3+ZrO2 or Y2O3+TiO2, and the resulting powders were extruded at 950?°C. The resulting fine grain structure, particularly for the Ti and Zr containing alloys, led to very high strength but limited ductility. Comparison with variants of commercial PM2000 (Fe-20Cr-5Al) highlighted the significant impact of the powder consolidation step on the alloy grain size and, therefore, on the alloy mechanical properties at T?<?500?°C. These low-Cr compositions exhibited good oxidation resistance at 1400?°C in air and steam for 4?h but could not form a protective alumina scale at 1450?°C, similar to observations for fine grained PM2000 alloys. The effect of alloy grain size, Zr and Ti additions, and impurities on the alloy mechanical and oxidation behaviors are discussed.
"Helium sequestration at nanoparticle-matrix interfaces in helium + heavy ion irradiated nanostructured ferritic alloys" Yutai Katoh, Chad Parish, Lizhen Tan, Steven Zinkle, Kinga Unocic, Sosuke Kondo, Lance Snead, David Hoelzer, Journal of Nuclear Materials Vol. 483 2017 21-34 Link
We irradiated four ferritic alloys with energetic Fe and He ions: one castable nanostructured alloy (CNA) containing Ti-W-Ta-carbides, and three nanostructured ferritic alloys (NFAs). The NFAs were: 9Cr containing Y-Ti-O nanoclusters, and two Fe-12Cr-5Al NFAs containing Y-Zr-O or Y-Hf-O clusters. All four were subjected to simultaneous dual-beam Fe + He ion implantation (650 °C, ~50 dpa, ~15 appm He/dpa), simulating fusion-reactor conditions. Examination using scanning/transmission electron microscopy (STEM) revealed high-number-density helium bubbles of ~8 nm, ~1021 m-3 (CNA), and of ~3 nm, 1023 m-3 (NFAs). STEM combined with multivariate statistical analysis data mining suggests that the precipitate-matrix interfaces in all alloys survived ~50 dpa at 650 °C and serve as effective helium trapping sites. All alloys appear viable structural material candidates for fusion or advanced fission energy systems. Among these developmental alloys the NFAs appear to sequester the helium into smaller bubbles and away from the grain boundaries more effectively than the early-generation CNA.
"High-energy synchrotron x-ray techniques for studying irradiated materials" David Hoelzer, Jun-Sang Park, Xuan Zhang, Hemant Sharma, Peter Kenesei, Meimei Li, Jonathan Almer, Journal of Materials Research Vol. 30 2015 1380-1391 Link
High performance materials that can withstand radiation, heat, multiaxial stresses, and corrosive environment are necessary for the deployment of advanced nuclear energy systems. Nondestructive in situ experimental techniques utilizing high energy x-rays from synchrotron sources can be an attractive set of tools for engineers and scientists to investigate the structure-processing-property relationship systematically at smaller length scales and help build better material models. In this study, two unique and interconnected experimental techniques, namely, simultaneous small-angle/wide-angle x-ray scattering (SAXS/WAXS) and far-field high-energy diffraction microscopy (FF-HEDM) are presented. The changes in material state as Fe-based alloys are heated to high temperatures or subject to irradiation are examined using these techniques.
"Post irradiation examination of nanoprecipitate stability and α′ precipitation in an oxide dispersion strengthened Fe-12Cr-5Al alloy" Caleb Massey, Philip Edmondson, Kevin Field, David Hoelzer, Kurt Terrani, Steven Zinkle, Scripta Materialia Vol. 162 2018 94-98 Link
"Characterization of Nanostructured Ferritic Alloy Atomized with Yttrium And Controlling Oxygen Content" Nicholas Cunningham, David Hoelzer, Stuart Maloy, G. Robert Odette, TMS 2014 February 16-20, (2014)
"Manufacturing of nanostructured ODS steel cladding tubes for advanced nuclear reactors using cold spray technology" Mia Lenling, Hwasung Yeom, Ben Maier, Greg Johnson, David Hoelzer, Peter Hosemann, Stuart Maloy, Kumar Sridharan, Jeffrey Graham, The Minerals, Metals and Materials Society (TMS) 2019 March 10-14, (2019)
"Nanoscale analysis of neutron irradiated ODS 14YWT ferritic alloy" Maria A Auger, David Hoelzer, Kevin Field, European MRS 2019 May 27-31, (2019)
"Program Review Presentation Entitled "Development of Low Temperature Spray Process for Manufacturing Fuel Cladding and Surface Modification of Reactor Components"" Mia Lenling, Kumar Sridharan, Hwasung Yeom, Peter Hosemann, David Hoelzer, Jeffrey Graham, Stuart Maloy, Advanced Methods for Manufacturing Program Review December 4-6, (2018)