The Fe addition as an effective treatment for improving the radiation resistance of fcc NixFe1-x single-crystal alloys

In this work, five different compositions of fcc Ni and NixFe1-x single crystal alloys namely Ni, Ni0.88Fe0.12, Ni0.77Fe0.23, Ni0.62Fe0.38, Ni0.38Fe0.62 were irradiated by 1.5 MeV Ni-58 ions at room temperature in a wide fluence range (4 x 10(13) to 4 x 10(15) ions/cm(2)). The role of Fe addition on the radiation resistance of the NixFe1-x single crystals was studied by transmission electron microscopy (TEM), ion channeling technique (RBS/C) and nanoindentation techniques. The Multi-Step Damage Accumulation analysis revealed the cross-sections for damage formation significantly decreases for Ni0.38Fe0.62 and Ni0.62Fe0.38 as compared to that in pure Ni single crystal, which is consistent with RBS/C and TEM results. The results of nanoindentation show that Ni0.62Fe0.38 alloy possesses the highest hardness (2.96 GPa) among the other compositions in a pristine state. To interpret this result, hybrid Monte Carlo/ Molecular dynamics simulations were used to check the presence of the ordered crystal phase structure for NixFe1-x binary alloys. The simulation results have shown that depending on the iron content, we deal with different amounts of FeNi3 (L1(2)) phase. This result revealed that in Ni0.62Fe0.38 alloy, nanoprecipitate FeNi3 (L1(2)) phase (around 20%) is formed inside the disordered matrix, which could be one of the main reasons for the high hardness of this alloy before irradiation. Additionally, we have found adding iron reduced the number and size of the defects (as a result of ion irradiation) in NixFe1-x because the Fe element is more stable than Ni, which results from the electron configuration of both elements in the excited state. Therefore, the more iron in the material, the fewer defects are created.