Development and Experimental Characterization of Ti-Zr-Hf-Gd–Based High-Entropy Alloys Reinforced with Rare Earth Element Oxides for Advanced Nuclear Applications Through Nuclear Radiation Transmission, Phase Stability, and Nanostructure Control

This study designs and evaluates Ti-Zr-Hf-Gd–based high-entropy alloy (HEA) matrix composites prepared with three different rare earth oxide additions, namely Sm2O3, Er2O3, and Eu2O3, as multifunctional candidate materials for nuclear- and radiation-related applications. The rare earth oxide additions were selected because of their potential contribution to photon attenuation and neutron interaction behavior.X-ray diffraction analysis revealed that the alloying strategy strongly influenced the resulting phase constitution. The Nb-containing TiZrHfGdNbEr2O3 composition promoted a highly crystalline body-centered-cubic–dominated structure, whereas the B-containing TiZrHfGdBSm2O3 and TiZrHfGdBEu2O3 alloys exhibited dominant hexagonal close packed (hcp)-type features with broadened diffraction peaks, indicating refined or nanocrystalline structures associated with boride-related phase formation.scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses showed a relatively uniform elemental distribution in the Nb-Er2O3–containing alloy, while the B-containing alloys displayed localized Ti- and Zr-rich partitioning within the secondary phase regions, supporting the possible formation of hard (Ti,Zr,Hf)B2–type precipitates. Vickers microhardness measurements further confirmed a composition-dependent mechanical response, with the highest hardness observed for the Nb-containing alloy.Gamma-ray attenuation experiments using a 133Ba source confirmed that all the fabricated alloys exhibited effective shielding behavior within the measured photon energy range up to 383 keV, although the relative mass attenuation coefficient, linear attenuation coefficient, and half-value layer rankings varied with photon energy.In addition, theoretical EpiXS-based mean free path benchmarking suggested that the Eu2O3–containing alloy may provide favorable calculated attenuation behavior compared with AISI (American Iron and Steel Institute) 316 and Inconel 600/625 in the 0.5- to 2-MeV range; however, this comparison, which should be regarded as predictive screening, requires future experimental validation at higher gamma-ray energies.Fast neutron experiments under 241Am/Be exposure showed absorbed dose rate reductions of up to 56.7%, indicating the neutron attenuation capability of the developed compositions under the employed experimental conditions. Nevertheless, neutron activation of Hf-, Gd-, and Er-containing systems remains an important consideration for long-term nuclear service use and should be assessed through isotope-specific activation studies.Overall, the developed HEA composites demonstrated composition-dependent phase formation, microstructural features, microhardness behavior, and combined gamma/neutron attenuation potential, supporting their further investigation as advanced radiation shielding materials.