Non‐Additive Criteria Assessment in Sustainability Evaluation of High Entropy Alloys: A Toxicity‐Weighted Framework

Sustainability assessment of high entropy alloys (HEAs) requires robust methodologies that appropriately distinguish between additive and non‐additive material properties. Current approaches apply uniform weighted‐average calculations across all sustainability criteria, which inadequately captures the complex, synergistic behaviors exhibited by toxicity and other non‐additive indicators in multicomponent materials. This study develops and applies an improved framework for criteria assessment in HEA sustainability evaluation that explicitly distinguishes between additive criteria (cost, embodied energy) and non‐additive criteria (human health damage, human rights pressure, and labor rights pressure). We introduce a toxicity‐weighted scoring system that accounts for the disproportionate influence of highly toxic constituents through nonlinear weighting functions, providing more realistic estimates than simple weighted averages while avoiding overly conservative worst‐case assumptions. The methodology is applied to binary alloys (Fe–Ni and Fe–Mo), dilute alloys (Fe‐based stainless steel and Ni‐based superalloys), and various HEA compositions (transition metal, refractory, and light‐weight systems). Results demonstrate that choice of assessment methodology significantly influences materials selection outcomes, with differences between conventional and improved approaches ranging from 1 to 28 points in human health damage scores. This framework advances sustainability‐based materials selection for complex multicomponent systems where direct experimental data remain unavailable, with implications extending beyond HEAs to other multimaterial products.