Dufanets M. Structural phase stability and electrophysical properties of high-entropy alloys

The work is devoted to the study of the structure, phase composition, regularities of structural-phase transformations and temperature dependences of structure-sensitive properties of low-temperature BiCuGaSnPb and industrial AlCoCrCuFeNi high-entropy alloys of equiatomic composition. The viscosity, electrical conductivity and thermoelectric power of melts of CuBi, CuGa, CuPb, CuSn, CuBiSn, CuBiSnIn, CuBiS, which are components of low-temperature high-entropy liquid alloys, were investigated. The dependence of electrical conductivity and thermoelectric power on the temperature of Cu50Pb50, Cu50Sn50, Cu50Bi50 systems, which are satisfactorily described by the Faber-Ziman formula, has been investigated. The dependence of thermoEMF on energy is determined by both the electron free path length λ and the Fermi surface area SF. The structure, microstructure and mechanical properties of a number of equiatomic alloys of the six component AlCoCrCuFeNi system of different chemical composition have been studied. Particular attention was paid to the analysis of structural and thermodynamic criteria for the formation of the phase composition and its influence on the mechanical properties of alloys. According to thermodynamic and structural criteria and based on the X-ray phase analysis, it was shown that the structure of equiatomic high-entropy alloys AlCoCrCuFeNi has a two-phase nature and contains solid solutions with BCC (type B2) and FCC –lattice (type A1). Temperature and compositional dependences of density are analyzed and molar excess volume is calculated. With the exception of the CoCrCuFeNi melt, the studied multicomponent melts showed a negative deviation of the molar volume from the ideal solution. The magnitude of the deviation decreases with increasing number of components. The scientific results obtained in the work and the established physical dependences are of practical interest for the methodological and scientific bases needed for the development of high-entropy alloys for purposeful management of their structure and properties, as well as the use of this class of alloys in manufacturing products with improved properties. The influence of the concentration of chemical elements on the phase composition, the distribution of elements between the phase components, the structure and physical and mechanical properties of high-entropy alloys is highly important from the scientific and practical points of view.