| High-entropy alloy is one of the most popular new alloys in recent years.Due to its unique composition design,excellent mechanical properties,high temperature resistance,corrosion resistance and radiation resistance.It is considered to be a very potential one of the candidate nuclear structural materials.In this paper,the structures of FeCoNiCr alloy and FeCoNiCrTi0.2 are firstly characterized,and then irradiated with He+and Fe+,respectively.The irradiation behaviour after irradiation,and its mechanism was explored.In this paper,FeCoNiCrTix(x=0,0.2)are prepared using a vacuum melting furnace and annealed.The two samples after annealing are characterized,and the following results are obtained:FeCoNiCr alloy has a single-phase FCC structure with uniform element distribution and no obvious segregation.FeCoNiCrTi0.2 alloy has a second phase.The matrix is a single-phase FCC phase,and the second phase is a γ’phase with an L12 structure.The size of the γ’ phase is about 60-80 nm,and its structure is completely coherent with the matrix.In addition,the main constituent elements of the γ’phase in the FeCoNiCrTi0.2 alloy are Ni and Ti elements,the ratio is basically 3:1.The Co element is evenly distributed in the second phase and the matrix.XRD results show that the lattice constant of the FeCoNiCr sample is 3.5745 A,and that of the FeCoNiCrTi0.2 sample is 3.6061 A.The FeCoNiCr samples and FeCoNiCrTi0.2 samples are irradiated with He+with an energy of 50 keV and a irradiation fluence of 2×1016 ions/cm2 at 450℃.He bubbles size is characterized by TEM.The He bubbles size of FeCoNiCr is 3.25 ± 0.21 nm,and the size of He bubbles of FeCoNiCrTio.2 is 2.5 ± 0.47 nm.At 450℃,the size of He bubbles in FeCoNiCr is larger than that of FeCoNiCrTi0.2 samples,indicating that the FeCoNiCrTi0.2 samples have a stronger resistance to He+ radiation.An in-situ annealing experiment is performed on the FeCoNiCrTi0.2 samples with He+implanted.The behaviours of He bubbles in FeCoNiCrTi0.2 samples at different temperatures are characterized.The results show that the size of the He bubbles in the FeCoNiCrTi0.2 samples increase with the increase of the holding time,and increase with the increase of the annealing temperature,and the size change conforms to the empirical formula.At room temperature,FeCoNiCr samples are irradiated ex-situ with Fe+ with an energy of 400 keV,and the irradiation fluences are 3.33 × 1015 ions/cm2(8.6 dpa),1× 1016 ions/cm2(28.7 dpa)and 3.33×1016 ions/cm2(86.3 dpa),using TEM to characterize its structural changes.When the irradiation fluences are 3.33×1015 ions/cm2(8.6 dpa)and 1×1016 ions/cm2(28.7 dpa),the structure of FeCoNiCr samples does not change significantly,indicating that the FeCoNiCr samples have great radiation resistance stability.Under the irradiation fluences of 3.33×1016 ions/cm2(86.3 dpa),the FeCoNiCr samples are formed nanocrystals.We believe that on the one hand,it is due to the irradiation-induced amorphous and nano-crystallization according to the energy storage and dissipation process in the irradiation process.On the other hand,it is due to the formation of ripples with periodic wavy structure due to abnormal ion implantation.Due to the stress effect,the wave peak area becomes a favorable position for phase separation,and then nanocrystals are formed.At room temperature,the FeCoNiCrTi0.2 samples are irradiated ex-situ with Fe+with an energy of 400 keV,and the irradiation fluences are 3.33×1015 ions/cm2(8.56 dpa)and 3.33×1016 ions/cm2(85.6 dpa),using TEM to characterize its structural changes.When the FeCoNiCrTi0.2 sample is irradiated to 3.33 × 1015 ions/cm2(8.56 dpa),the second phase undergoes early dissolution and disordered transformation.When the radiation fluence is 3.33×1016 ions/cm2(85.6 dpa),the second phase transforms to amorphization,and the volume of the second phase becomes larger after being amorphous. |
PDF Full Text Request