Effects of Si doping on microstructure, mechanical properties and oxidation resistance of FeCrAl fuel cladding alloys

Abstract

FeCrAl alloys, as nuclear fuel cladding materials, exhibit excellent oxidation resistance, low linear expansion, neutron absorption and high-temperature mechanical properties, which provide promising options for enhancing the safety and reliability of nuclear reactors. In this study, we investigate the effect of silicon (Si) doping on the microstructure, mechanical properties, and oxidation resistance of Fe13Cr6Al alloys, tailored for nuclear fuel cladding applications. Through vacuum induction melting, Si contents of 0.1, 0.2, 0.3, and 0.4 wt.% were incorporated, with a non-doped alloy serving as a benchmark. Our findings reveal that Si doping substantially refines the grain structure, particularly evident at 0.4 wt.% Si, reducing the average grain size to 19.42 μm post-annealing at 800°C. This refinement enhances the mechanical robustness of the alloy, with the 0.4Si variant achieving the highest hardness (241.8 HV), tensile strength (628 MPa at room temperature; 573 MPa at 380°C), yield strength, and elongation at break, surpassing traditional FeCrAl materials. Additionally, Si doping curtails oxidation weight gain, evidenced by a parabolic decrease with increased Si content, and augments oxidation resistance by inducing SiO₂ and Al₂SiO₅ phases within the oxide layer. These advancements underscore the potential of Si-doped FeCrAl alloys in fortifying nuclear reactor safety through superior cladding material performance.