Structure and mechanical properties of high-entropy alloys of the CoCrZrMnNi system with different Zr and Mn contents produced by vacuum-induction melting

The mechanical properties and microstructure of high-entropy alloys (HEA) of the CoCrZrMnNi system produced by vacuum-induction melting are studied depending on the change in the Zr and Mn content. The effect of the Zr and Mn percentage on the microstructure and mechanical properties (Young’s modulus, nanohardness, microhardness) of the high-entropy alloys of the CoCrZrMnNi system is estimated. The relationship between varying the percentage of Zr and Mn and changing the grain size and mechanical properties of high-entropy alloys is studied. The structure, chemical composition and distribution of the intensity of characteristic X-ray radiation of atoms are studied using scanning electron microscopy. The study by scanning electron microscopy methods has demonstrated that in CoCrZrMnNi alloys, with an increase in the zirconium content and a decrease in the manganese content closer to the equiatomic composition, the material structure became more homogeneous. Changing the percentage of zirconium from 8 to 28 at. % contributed to the grain size reduction from 30 to 5 μm and a more uniform elemental distribution. The Сo19.8Cr17.5Zr15.3Mn27.7Ni19.7 alloy demonstrated the highest nanohardness (10 GPa) and Young’s modulus (161 GPa) during instrumental indentation with an indenter load of 50 mN. The Сo20.4Cr18.0Zr7.9Mn33.3Ni20.3 alloy has the lowest nanohardness, Young’s modulus, and microhardness among other alloys, which may be related to the coarse-grained structure with a grain size of up to 30 μm. As the indenter load increased to 5 N, the microhardness of the Сo19.8Cr17.5Zr15.3Mn27.7Ni19.7 alloy decreased compared to the Сo18.7Cr16.5Zr28.9Mn17.4Ni18.6 alloy, which may indicate more universal mechanical properties of alloys with equiatomic zirconium content.