Modeling the mechanism of micro / nanostructured surface formation in Al-Co-Cr-Fe-Ni and Co-Cr-Fe-Mn-Ni high-entropy alloys treated with a high current pulsed electron beam

Abstract

In this work, we investigated, using transmission and scanning electron microscopy, the microstructure of Al-Co-Cr-Fe-Ni and Co-Cr-Fe-Mn-Ni non-equimolar high-entropy alloys treated by high current pulsed electron beams with an energy density of 30 J / cm 2 . Both alloys revealed a cellular crystallization structure with an average cell size of 192 ± 5 nm, and 453 ± 6 nm, correspondingly. The study aims to improve the model of the mechanism of formation of micro-and nanostructured surface layers taking into account combined thermocapillary, concentration-capillary, evaporative-capillary and thermoelectric instabilities at the melt-plasma interface. The results of the linear stability analysis showed that the absorbed power density is lost by evaporation that leads to a decrease in the values of the gradient of the undisturbed temperature and, an increase in the wavelength at which the maximum rate of growth of disturbances is observed. An analysis of the dispersion equation showed that the values of the wavelengths of disturbances on the surface of alloys in the liquid phase are 454 nm for Co-Cr-Fe-Mn-Ni and 189 nm for Al-Co-Cr-Fe-Ni, which deviate from the experimental data by no more than 2 %.