In-situ study of defect evolution and calculation of defect migration energy in FeCoCrNiAl<sub>0.3</sub> high-entropy alloy under high-energy electron irradiation

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The sluggish diffusion and severe lattice distortion effects in high-entropy alloys (HEAs) theoretically impede the movement of radiation-induced point defects, thereby effectively suppressing the formation of larger defect clusters and ultimately enhancing the radiation resistance of materials. Current research on the radiation resistance of HEAs primarily concentrates on the qualitative analysis of the migration behaviors of radiation-induced defects, while the quantitative research on the energy barriers of the migration behavior of point defects is still limited. As a representative HEA system, FeCoCrNiAl-based alloys exhibit exceptional properties, including enhanced ductility, remarkable shear resistance, high tensile yield strength and excellent oxidation resistance. In this study, we selected the FeCoCrNiAl<sub>0.3</sub> alloy as the model material and conducted in-situ observations using a 1.25 MV high voltage electron microscope (HVEM) to systematically investigate the temporal evolution of irradiation-induced defects and precipitates under different temperatures. Based on the statistical data of saturated defect number density and defect growth rates under three irradiation temperatures, two intrinsic parameters of the alloy - the interstitial atom migration energy and vacancy migration energy - were determined respectively, which is 1.09 eV and 1.47 eV, respectively. The higher interstitial atomic migration energy may be related to the incorporation of Al, which has a smaller threshold energy and exhibits a larger atomic radius difference compared to the other elements in the alloy. In addition, the morphology and distribution of dislocation loops formed under 723 K high energy electron irradiation were characterized in detail, revealing the coexistence of perfect dislocation loops and Frank dislocation loops, both of which grow along different crystal planes. No systematic difference is observed between the growth process of the two types of loops.