Influence of Electron Beam Treatment on the Defect Substructure of a High-Entropy Co–Cr–Fe–Mn–Ni Alloy

Surface treatment by an electron beam is a method of improving the mechanical properties of metals. Rapid heating, vaporization, recrystallization, and plastic deformation in the surface produce dislocations with high density. That results in increase in physicomechanical properties such as the hardness and wear resistance. Since high-entropy alloys are a relatively new class of materials, the influence of a high-intensity pulsed electron beam on the dislocational structure has yet to be established. In the present work, a nonequiatomic high-entropy Co–Cr–Fe–Mn–Ni alloy produced by additive wire-arc technology undergoes surface treatment using a high-intensity pulsed electron beam (energy density 30 J/cm 2 ). Investigation of thin foil by means of a transmission electron microscope indicates that this treatment has no effect on the chemical composition of the alloy. However, the dislocational substructure is profoundly changed. The scalar dislocation density varies nonmonotonically, reaching a maximum of 5.5 × 10 10 cm –2 at a distance of 25 μm from the irradiated surface. At this distance, a somewhat oriented cellular dislocation substructure (cell size 400–600 nm) is formed. At greater distances from the surface (up to 45 μm), the dislocation substructure changes from cellular to cellular–reticular. At a distance of 120–130 μm, no effect of the electron beam is seen: the substructure corresponds to that of the initial alloy with a chaotic distribution of the dislocations.