CrCuFeMnNi high-entropy alloys for semisolid processing: The effect of copper on phase formation, melting behavior, and semisolid microstructure

High-entropy alloys containing Cu can lead to the formation of phases with lower melting temperatures and large solidification intervals, making them potential candidates for semisolid processing. Accordingly, in this study we aimed to investigate the influence of Cu content on the phase formation, melting behavior, and semisolid microstructure of CrCuFeMnNi alloys. Ingots with varying CrCuxFeMnNi compositions (x = 0, 0.5, 1, 1.5, 2, and 2.5) were arc-melted, cross-rolled, heated to reach the semisolid state, and water-quenched. Microstructural characterization involved scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The CrCuFeMnNi alloys were composed of one BCC phase, rich in Cr, and two FCC phases, one rich in Cu (FCC1) and the other with a more balanced composition (FCC2). The melting of the CrCuFeMnNi alloys was characterized by three thermal events, which corresponded to the melting of each phase. The solidification interval increased with the Cu content, and it was found that the studied alloys could be processed in the semisolid state at temperatures below 1100 degrees C. Therefore, the cross-rolled samples were isothermally heat-treated at 1080 degrees C for 300 s, resulting in globular microstructures. The chemical composition of the phases was modified after semisolid treatment as compared to the as-cast condition. The fraction of the BCC phase in the quenched microstructures did not change with the alloy composition; in contrast, the fraction of FCC1 increased, whereas that of FCC2 decreased with increasing Cu content.