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Micro-Structure and Mechanical Properties of FeCrAl Alloys Under Extreme Environment

Dongyue Xie, University of Nebraska - Lincoln


Iron-chromium-aluminum (FeCrAl) alloys become a competitive candidate for fuel cladding materials because of extraordinary oxidation resistance, excellent corrosion resistance at high-temperature and low parabolic oxidation rate. Mechanical properties and behaviors of FeCrAl alloys, especially in irradiated state, must be thoroughly investigated. However, neutron irradiation in experimental reactor is extremely time-consuming, which makes ion-irradiated an ideal replacement. Ion penetration depths is limited to tens of microns, which makes micro-scale mechanical tests a necessity. Plastic deformation in FeCrAl alloys is accommodated by dislocation slips. Corresponding to a body-centered cubic (BCC) structure of FeCrAl alloy (C35M), experimental characterizations confirmed two slip families, {110}<111> and {112}<111>. In this dissertation, our focus is to explore the effects of deformation-induced and irradiation-induced defects on dislocation motion at room temperature. The initial samples of C35M alloy are annealed at 800 °C for 1 hour. Two types of defects were introduced to it. Deformation-induced defects were introduced by tension until fracture; irradiation-induced defects were produced by proton irradiation and Fe3+ ion irradiation. The orientation of grains in these samples were analyzed. Micro-pillars were prepared in the grains with selected orientation and tested. The resistance to dislocation glide on each slip systems in annealed samples were measured via compression and tensile tests on micro-pillar with different morphology. The orientation and grain boundary dependence of mechanical responses of FeCrAl alloy were investigated through micro-mechanical tests. The strain hardening rate increases with increasing the number of activated slip system in single crystals. Grain boundaries with the high geometrical compatibility factor corresponds to a low strain hardening rate. The mechanical responses of alloy with pre-existed defects were explored. Both deformation-induced and irradiation-induced defects increase the glide resistance of dislocations and the instability of deformation. The deformation-induced defects will also increase the strain hardening rate, but irradiation- induced defects will not.This work deepens the understanding of mechanical behavior in FeCrAl alloys, explores the relationship between defects and mechanical property. These results will benefit the processing optimization and performance improvement of FeCrAl alloys.

Subject Area

Materials science

Recommended Citation

Xie, Dongyue, "Micro-Structure and Mechanical Properties of FeCrAl Alloys Under Extreme Environment" (2021). ETD collection for University of Nebraska-Lincoln. AAI28712924.