Effect of dose and post irradiation annealing in Ni implanted high entropy alloy FeCrCoNi using slow positron beam

Defect characterization of room temperature 1.5 MeV Ni ion implanted high entropy FeCrCoNi alloy for two fluences (1 × 1015 ions/cm2 and 5 × 1016 ions/cm2) was carried out using the variable low energy positron beam. The FCC solid solution remains robust and stable under 100 dpa irradiation and high temperature annealing. The change in the defect sensitive S-parameter upon implantation reveals the presence of monovacancies for both the doses. The changes in the defect microstructure upon thermal annealing are found to be dose dependent. The high dose shows the formation of stable stacking fault tetrahedrons (SFT's) from the aggregates of monovacancies at higher annealing temperatures while the low dose shows the annealing of monovacancies with temperature.