The irradiation resistance of pre-deformed FeCu alloy was studied using a 3 MeV Fe ion irradiation experiment at room temperature in comparison with that of the as-received sample.Nanoindentation and atom probe tomography (APT) were used to characterize the mechanical properties and solute distribution.The stress-strain curve obtained by nanoindentation shows that the yield strength (σ0.2) of the pre-deformed sample is unexpectedly reduced with an increase in the irradiation dose to five displacements per atom (dpa).We suggest that it results both from the decrease in the dislocation density and the suppression of defects during irradiation.APT shows that the nucleation of the Cu cluster is suppressed;however,its growth is promoted in the pre-deformed sample,resulting in the formation of sparse and coarse clusters at 1 dpa irradiation.These coarse Cu clusters were then unexpectedly refined to finer grains with an increase in the irradiation dose to 5 dpa.Theoretically,the improvement in the resistance to irradiation in the pre-deformed sample is attributed to the dense point-defect sinks,that is,the dislocations and grain boundaries introduced by pre-deformation.In addition,the contributions of the dislocations and grain boundaries to the sink strength are estimated for both the as-received and pre-deformed samples.The results indicate that dislocations,rather than grain boundaries,play a major role after deformation.