Structural Transformations upon Annealing of a Cold-Worked High-Entropy Al 0.3 CoCrFeNi Alloy

The paper considers the features of structural transformations during annealing of a high-entropy Al 0.3 CoCrFeNi alloy. The ingots obtained by argon-arc melting were subjected to cold rolling with a reduction ratio of 50%. The billets were annealed in a furnace for 4 hours at temperatures of 200, 400, 600, 800, and 1000°C. The samples obtained by the described method were studied using the methods of synchrotron X-ray diffraction in the transmission mode and diffraction of backscattered electrons. The results indicate that, up to a temperature of 600°C, the structure of the alloys is represented by a single phase with a fcc lattice. When alloys are annealed at temperatures of 800 and 1000°C, the phase composition is characterized by the presence of two phases: a disordered phase with a fcc lattice and an ordered phase with a primitive cubic lattice. At temperatures above 800°C, annealing of alloys is accompanied by the development of recrystallization processes. After annealing at 800°C, the relative proportion of microvolumes characterized by an interangular misorientation of more than 10° was 20%. After annealing at 1000°C, it was 65%. The microhardness of the samples under study increases with an increase in temperature up to 600°C and decreases with a further increase in temperature. An analysis of the width of the diffraction maxima using the methods of profile analysis of diffraction patterns indicates an increase in the distortions of the crystal lattice of the disordered phase. This behavior may be related to the precipitation of nanosized inclusions in the matrix of the main phase.