Effect of High-Dose Gamma Irradiation on the Microstructure, Mechanical and Radiation Shielding Performance of Nano-Er2O3 Reinforced Al7075–B4C Hybrid Composites

Abstract

This study focuses on the fabrication and characterization of B4C and nano-Er2O3-reinforced Al7075 metal matrix composites, with compositions of Al7075-(10-n)B4C-nEr(2)O(3) (n = 0, 2, 4, 6 wt%). The composites were produced through high-energy ball milling, cold isostatic pressing, and sintering at 550 degrees C. Phase constitution, microstructure, and mechanical properties were examined before and after Co-60 gamma irradiation at doses of 50, 100, and 200 kGy. X-ray diffraction (XRD) analyses revealed alpha-Al as the primary phase in all compositions. An increase in Er2O3 content resulted in peak broadening and slight 2 theta shifts, indicating enhanced lattice strain, increased defect density, and grain refinement. No intermetallic reaction phases formed between the Al7075 matrix and B4C/Er2O3 reinforcements. SEM/EDS observations showed that the composite containing 4-Er2O3 and 6-B4C exhibited the most homogeneous reinforcement distribution, lowest porosity, and superior sintering integrity, while 6-Er2O3 led to particle agglomeration and microstructural degradation. Vickers microhardness measurements demonstrated that Er2O3 addition and moderate gamma doses (<= 100 kGy) enhanced hardness through dispersion and radiation hardening, but a significant decrease in hardness occurred at 200 kGy due to radiation-induced pore and crack formation. Gamma shielding performance was experimentally evaluated using Am-241 (59.5 keV) and Cs-137 (662 keV) sources in narrow-beam geometry and validated by PHITS Monte Carlo simulations. Increasing Er2O3 content improved the linear attenuation coefficient by approximately similar to 63% at 59.5 keV and similar to 11% at 662 keV, despite a decrease in B4C content. Overall, the 4-Er2O3 composite is a promising lightweight structural gamma-shielding material for aerospace and nuclear applications.