Chemically-biased diffusion and segregation impede void growth in irradiated Ni-Fe alloys

Recent irradiations of Ni-Fe concentrated solid solution alloys have demonstrated significant improvement of radiation performance. This improvement is attributed to redistribution of the alloying elements near sinks of point defects (voids, dislocations) due to chemically-biased atomic diffusion, where vacancies have preference to migrate via Fe atoms and interstitials via Ni atoms. In Ni-Fe, all sinks are enriched by Ni atoms, which strongly affects further interactions of radiation-produced mobile defects with voids and dislocations, hence void growth and dislocation climb. Ni-decorated sinks interact stronger with interstitial atoms than vacancies, which enhances dislocation loops growth. At the same time, Ni segregation creates Fe-enriched “channels” for vacancy migration out of the damage region to agglomerate in the outer regions, inaccessible to interstitial atoms. Strong effect of chemically-biased diffusion is supported by transmission electron microscope characterization and calls for special attention in designing alloys with desired properties through tuning defect mobilities.