Abstract
Low-chromium (<10%Cr) high strength oxide dispersion strengthened (ODS) FeCrAl alloys are considered promising candidates for accident tolerant fuel cladding in light water fission reactors. These alloys are designed to combine the beneficial high temperature mechanical properties of ODS materials with the exceptionally high temperature oxidation resistance of FeCrAl in comparison to conventional Zr-containing cladding materials, while also providing good mechanical and aqueous corrosion behavior under normal light water reactor operating conditions. The initial (1st generation) ODS FeCrAl alloys combined gas atomized FeCrAl powders with yttria and other oxides for alloying element additions using the mechanical alloying approach. These alloys exhibited low ductility but excellent high temperature tensile strength while maintaining good oxidation resistance at temperatures up to 1400 °C. In an attempt to improve alloy ductility for accident tolerant fuel cladding applications, new low-Cr ODS FeCrAl alloys with decreased oxygen content were developed with the Zr alloying solute already gas atomized into the powder prior to mechanical alloying. The resultant Fe-10Cr-6.1Al-0.3Zr+0.3Y2O3 (106ZY) powders were ball milled for 10, 20, and 40hr followed by consolidation via hot extrusion at temperatures ranging from 900 to 1050 °C. Increasing the mechanical alloying time decreased the resultant grain size and improved high temperature tensile properties. Decreasing the extrusion temperature refined the grain size and subsequently strengthened the ODS FeCrAl 106ZY alloys while lowering the ductility. Scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) demonstrated the Zr solute addition effectively sequestered impurity C and N within the matrix. The root mean square (RMS) hardening superposition model for yield strength shows good agreement with experimental results. Errors between predicted and experimental values are discussed within the scope of processing parameters. These 2nd generation 106ZY alloys show a distinct increase in alloy ductility without sacrificing the high temperature tensile properties characteristic of legacy or 1st generation ODS FeCrAl alloys.
| Original language | English |
|---|---|
| Pages (from-to) | 227-238 |
| Number of pages | 12 |
| Journal | Journal of Nuclear Materials |
| Volume | 512 |
| DOIs | |
| State | Published - Dec 15 2018 |
Funding
The work presented in this paper was supported by the Advanced Fuels Campaign of the Fuel Cycle R&D program in the Office of Nuclear Energy, U.S. Department of Energy . A portion of the characterization efforts was performed on the FEI Talos F200X S/TEM tool provided by US DOE, Office of Nuclear Energy , Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors would like to acknowledge and thank Dieter Isheim at Northwestern University for his assistance in acquiring the atom probe tomography data presented in this study. The authors would like to also acknowledge Cox Gregory for alloy extrusion and Chris Stevens for collecting tensile data for this work. The authors extend sincere acknowledgements to Gregory Cox and his team for extruding the studied alloys, Tom Geer for metallographic sample preparation, and Chris Stephenson for tensile testing. This material is based upon work supported under a Department of Energy Nuclear Energy University Programs (NEUP) Graduate Fellowship.
Keywords
- Mechanical properties
- Oxide dispersion strengthened (ODS) alloy
- Precipitation
- Strengthening mechanisms