CHANGES IN THE FRACTURE SURFACE OF A HIGH-ENTROPY CoCrFeMnNi ALLOY AFTER ELECTRON BEAM PROCESSING

Abstract

Using the technology of wire-arc additive manufacturing (WAAM), a high-entropy alloy (HEA) CoCrFeMnNi of non-equiatomic composition was obtained. Using scanning electron microscopy, the structure of the destruction surface of HEA samples in the initial state and after irradiation with a pulsed electron beam with the following parameters was studied: electron beam energy density 10–30 J/cm², duration 50 μs, number of pulses 3, pulse repetition rate 0,3 Hz. The study of the destruction surface of the HEA after EPO, in addition to areas with a viscous mechanism of destruction, revealed areas with a strip (lamellar) structure. The area with a band structure increases with an increase in the electron beam density from 25 % at 10 J/cm² to 65 % at 30 J/cm². The diameter of the separation pits in the fracture bands varies within 0.1–0.2 µm, which is much smaller than the size of the separation pits in the rest of the HEA sample. After EPO, the thickness of the molten layer varies within (0.8-5.0) µm and increases with increasing energy density of the electron beam. The average size of crystallization cells formed during EPO depends on the energy density of the electron beam and increases from 310 nm at 15 J/cm² to 800 nm at 30 J/cm².