Comparative Gamma and Neutron Shielding Performance of High-Entropy and Shape Memory Alloys: A Data-Driven Analysis

High-entropy alloys (HEAs) and shape memory alloys (SMAs) have attracted significant interest for nuclear, aerospace, and medical applications due to their structural robustness. But their radiation shielding performance has yet to be evaluated in a direct, head-to-head comparison. In this study, the gamma-ray and fast-neutron attenuation properties of 59 alloys (30 HEAs and 29 SMAs) were evaluated against five standard reference materials across photon energies ranging from 0.015 to 15 MeV and a Watt fission neutron spectrum. Attenuation parameters calculated via Phy-X/PSD and Bragg additivity were cross-verified using independent Geant4 Monte Carlo simulations, agreeing to better than 0.5% outside the K-absorption edges of the heavy constituents, where three electromagnetic constructors differ among themselves by up to 1.45 percentage points. Because the two families differ systematically in density, comparisons were controlled both by covariate adjustment and by one-to-one density matching, and every quantity was evaluated on a per-thickness and a per-mass basis. No class difference in photon attenuation was detectable across the full sample. Of 19 pairs of density-matched alloys, those with only one high-atomic number dominant constituent element had greater attenuation in the photoelectric and pair production regimes and equal attenuation in the Compton regime; the exact elemental composition shows that the cause is greater attenuation in one element and not in the family of alloys. The high-entropy alloys showed a higher fast neutron removal cross-section on both bases, a difference that survived adjustment for density and effective atomic number, density matching and mass normalization. Explicit transport simulation of a twelve-alloy subset reproduced the direction of this difference at every configuration examined but was underpowered to confirm it independently. The material rankings inverted between the two design bases: none of the alloys outperformed tungsten by thickness or ordinary Portland concrete by mass, whereas 23 and 40 of 59 outperformed lead respectively. Findings are descriptive of this literature-derived sample.