Synergistic Enhancement of Gamma Radiation Shielding and Mechanical Properties in Al7075 Composites via Nano-Er2O3 Reinforcement: A Combined Experimental and PHITS Simulation Study

Abstract

Aluminum alloys are widely used in weight-critical engineering systems; however, their intrinsically low atomic number limits their effectiveness for gamma-ray shielding. In this study, nano-Er2O3 (0-4 wt%) was incorporated into an Al7075 matrix and consolidated via a powder-metallurgy route consisting of mechanical alloying, cold isostatic pressing, and sintering (550 degrees C/4 h, Ar). Microstructural analyses reveal that 1 wt% Er2O3 provides the most homogeneous dispersion, whereas 4 wt% promotes particle clustering at interparticle/grain boundaries and increases porosity. The 1 wt% composite exhibited the most favorable densification strength balance with a relative density of 96.88% and a Vickers microhardness of 32.72 HV (HV0.2), compared to 20.44 HV for unreinforced Al7075. Gamma attenuation measurements using Am-241 (59.5 keV) and Cs-137 (662 keV), supported by PHITS Monte Carlo simulations, show a pronounced improvement in shielding performance with increasing Er2O3 content, particularly at low photon energy. The linear attenuation coefficient increased by up to 236.1% (Am-241) and 89.7% (Cs-137) for the 4 wt% composite relative to Al7075, with experimental and PHITS results agreeing within similar to 6%. Overall, nano-Er2O3 reinforced Al7075 composites offer a promising lightweight structural shielding concept for aerospace applications, where an optimum reinforcement level (approximate to 1 wt%) maximizes microstructural integrity and hardness, while higher contents further enhance attenuation for missions requiring increased low-energy gamma protection in harsh orbital environments.