Effects of Graphite Addition on Structure and Properties of CrCuFeNiTiAl1 High-Entropy Alloys

In this study, the CrCuFeNiTiAl1 equiatomic alloy was used as a base, which was modified by adding graphite in proportions of 0.5, 1.0, 2.5, and 5.0 mol%. The samples were obtained by powder metallurgy and sintering at 1200 °C for 2 h in a furnace with a protective argon atmosphere. Structural characterization was performed by XRD. A microstructural evaluation was conducted by SEM. The best mechanical microhardness and compressive strength results were obtained in the samples with the lowest amounts of graphite (238 μHV and 1000 MPa, respectively). The density values showed that samples with low amounts of graphite had better densification, lower porosity, and finer structural characteristics than those with graphite percentages higher than 1 mol%. The XRD studies determined the formation of a mixture of crystalline structures composed of FCC due to the presence of Cu, Ni, and Al metals; BCC due to Fe and Cr metals; and HCP due to Ti, and the formation of a Cr7C3 compound. SEM analysis showed the formation of cracks and porosity due to the formation of carbides.