A strategy for imparting radiation resistance to dilute alloys using synergistic solutes

A novel approach for imparting radiation resistance to dilute alloys is proposed whereby two synergistic solute species are employed, a first one, solute B, that binds strongly to vacancies and a second one, solute C, that binds to solute B and is also a slow diffuser in solvent A. This combination results in B-C solute clusters that are immobile traps for vacancies. These traps promote point-defect recombination over irradiation doses far beyond that achievable in binary alloys, where solutes that strongly bind to vacancies are typically fast diffusers and thus quickly removed from grain interiors by radiation-induced segregation. A parametric study, performed using atomistic kinetic Monte Carlo simulations with realistic metallic solute properties in Cu, reveals that alloy stability under irradiation derives largely from the formation of mixed B-C solute clusters comprised of 10 or more atoms. The solute loss at sinks, moreover, is found to follow stretched exponentials, with the most promising alloys corresponding to values of the stretch exponent $\beta$ approaching 0.5. The effects of irradiation dose rate and grain size are discussed using simple scaling relationships. Lastly, the approach is illustrated by identifying promising solute combinations in Cu, Ni and Al alloys.