Reduction of freely migrating defect concentrations by cascade remnants in Ni-Si alloys

Interactions of cascade remnants with freely migrating defects in Ni-12.7% Si were investigated using in-situ Rutherford backscattering spectrometry during simultaneous irradiation with 1.5 MeV He and 400 keV Ne ions at elevated temperatures. Radiation induced segregation of Si atoms toward the specimen surface caused γ′-Ni₃Si layers to grow on the surface during irradiation. The γ′-Ni₃Si growth rate during He bombardment was strongly suppressed by simultaneous irradiation with Ne ions, even when the calculated defect production rate for the Ne ions was only a few percent of that for the He ions. This result shows that the cascade remnants generated by the Ne ions act as additional recombination sites for freely migrating defects, reducing their steady state concentration. Despite a large difference in defect properties and in the kinetics of radiation induced segregation between the two alloys, the effects of cascade remnants on freely migrating defects in Ni-12.7% Si are remarkably similar to those found previously in Cu-1% Au.