Effect of electron beam treatment on the structure and properties of AlCoCrFeNi high-entropy alloy

Abstract

In last years, a new system of alloys known as highentropy alloys (HEA) has been attracting scientists’ attention [1–3]. Unlike traditional alloys high-entropy ones are composed of five and more main elements with a percentage from 5 to 35 at.% [4–7]. The idea of high-entropy alloys is that atoms of all elements are considered atoms of a dissolved substance, cause deformation of a crystal structure and improve thermodynamic stability of properties related to differences in atomic radii of components. It results in high entropy of a system to further manufacturing a material with unique properties, which are impossible in traditional micro-alloying techniques [8–10]. The original results obtained in the field of HEA are considered in detail in analytical reviews [11–13] where the HEA microstructure, properties, thermodynamics are described, results of modelling of their structure are considered and new variants of methods for obtaining the multi-component alloys are discussed. The HEA studies have shown that it is possible to form in them nanodimensional structures and even amorphous phases due to considerable distortions of lattice caused by difference in the atomic radii of substitution elements [1]. Present day practically all types of such alloys (structural, cryoand heat resistant, corrosion-resistant, those with special magnetic and electrical properties) as well as compounds (carbides, nitrides, oxides, borides, silicides) are being developed [14]. Improvement of alloy properties can be achieved by treating the surface with concentrated energy flows. The main feature of hardening materials with concentrated energy fluxes, in comparison with the methods of traditional thermal and chemical-thermal treatment, is the nanostructuring of their surface layers. This means a decrease in the scale level of localization of plastic deformation of the surface, which leads to a more uniform distribution of elastic stresses near it under the influence of operational factors. As a result, the probability of nucleation of microcracks in the surface layer leading to failure is significantly reduced. This increases both strength and ductility. One of the most promising and highly effective methods of surface hardening of products is electron-beam processing [15, 16]. Electron beam processing provides ultrahigh heating rates (up to 106 K/s) of the surface layer to predetermined temperatures and cooling of the surface layer due to heat removal to the bulk of the material at speeds of 104–109 K/s, resulting in the formation of non-uniform submicron nanocrystalline structural phase states. Effect of electron beam treatment on the structure and properties of AlCoCrFeNi high-entropy alloy