Study of the Evolution of the Structure of a High-Entropy Al₂₀Ni₂₀Co₂₀Fe₂₀Cr₂₀ Alloy under the Action of High Pressure and Temperature

The structure of a high-entropy submicrocrystalline AlNiCoFeCr alloy of equiatomic composition obtained by arc melting is studied by electron microscopy and X-ray diffraction. The alloy consists of a substitutional solid solution with the packing of components corresponding to the B2 structure based on a distorted BCC lattice. The average grain size of the B2 phase is 120 nm. The stability of the alloy with increasing temperature is studied. When the alloy is heated to 1650°C and subsequently solidified an increase in the grain size of the B2 phase and the separation of several phases with different morphologies along the grain boundaries are observed in the structure. The effect of high pressure on the alloy structure after quenching from the liquid phase is explored. The structure of the sample obtained upon solidification at a temperature of 1650°C under a pressure of 5 GPa is different from the structure of the alloy obtained at a temperature of 1650°C by arc melting. Under thermobaric conditions, a structure of mixed A1 (body-centered cubic) and A2 (face-centered cubic) phases is formed in the alloy. The alloy has high hardness, the value of which, depending on the selected production conditions, varies from 4.8 to 5.5 GPa.