Mechanical Properties and Structure of High-Entropy Alloys Сo20Cr20Fe10Mn30Ni20 and Co20Cr20Zr9Mn31Ni20

The mechanical properties (nanohardness, Young’s modulus, microhardness, wear resistance), microstructure, and phase composition of the high-entropy alloys Сo20Cr20Fe10Mn30Ni20 and Co20Cr20Zr9Mn31Ni20 were investigated. The influence of substituting Zr for Fe on the structural-phase state of the CoCrMnNi system was evaluated. In the Co20Cr20Zr9Mn31Ni20 alloy, intermetallic compounds (e.g., ZrCo2, Cr2Ni3) were observed to form, which may be attributed to the larger atomic radius of Zr (0.160 nm) compared to Co, Cr, Mn, and Ni (~0.125–0.135 nm). This elemental partitioning induces localized lattice strain, promoting elemental segregation and intermetallic formation. The microstructure of the Co20Cr20Fe10Mn30Ni20 and Co20Cr20Zr9Mn31Ni20 alloys was analyzed via scanning electron microscopy (SEM) combined with characteristic X-ray emission mapping. SEM revealed that substituting zirconium for iron in the high-entropy alloy (up to 10 at %) led to the precipitation of secondary zirconium-rich phases, which reduced the chromium content available for dissolution in the matrix. The Co20Cr20Zr9Mn31Ni20 alloy exhibited 159% higher nanohardness and a 30.4% greater Young’s modulus compared to the non-equiatomic Cantor high-entropy alloy (CoCrFeMnNi), indicating superior strength and resistance to elastic deformation. The lower margin of error in the Young’s modulus of the Co20Cr20Fe10Mn30Ni20 alloy may stem from its more homogeneous elemental distribution within the as-cast ingot. Both alloys demonstrated comparable wear resistance parameters, with a wear rate of ≈2.08 × 10–5 g/rev, implying a mass loss of 0.0000208 g per revolution under frictional conditions. This exceptionally low wear rate underscores the need for further investigation into the underlying wear mechanisms.