Interstitial migration behavior and defect evolution in ion irradiated pure nickel and Ni-xFe binary alloys

Transition from long-range one-dimensional to short-range three-dimensional migration modes of interstitial defect clusters greatly reduces the damage accumulation in single-phase concentrated solid solution alloys under ion irradiation. A synergetic investigation with experimental, computational and modeling approaches revealed that both the resistance to void swelling and the delay in dislocation evolution in Ni-Fe alloys increased with iron concentration. This was attributed to the gradually increased sluggishness of defect migration, which enhances interstitial and vacancy recombination. Transition from long-range one-dimensional defect motion in pure nickel to short-range three-dimensional motion in concentrated Ni-Fe alloys is continuum, not abrupt, and within an iron concentration range up to 20%. The gradual transition process can be quantitatively characterized by the mean free path of the interstitial defect clusters.