Mechanism of Grain and Twin Nanoboundaries Making Strength and Wear Resistance Different in CoCrFeNiCu: A Molecular Dynamics Study

Abstract

With the indenter scratches the single-crystal, polycrystalline and polycrystalline-twin structures CoCrFeNiCu, these characteristics in various crystal nanostructures were found. Single-crystal structure CoCrFeNiCu has the strongest strength, but its wear resistance is weakest in the three types for the generating of long-range and same direction hexagonal closest packings (HCPs), because the long-range HCPs will move the internal atoms, making single-crystal structure CoCrFeNiCu has the most serious abrasive wear. However, the multigrain boundaries can isolate the damage of scratching, playing a lubrication role. Twin-polycrystalline CoCrFeNiCu has the best wear resistance in the three structures because of the hardening effects of twin boundaries. Our relevant research results can not only deeper the understanding about the different structural effects on the wear resistance mechanism of high-entropy alloys, but also provide the guidance for the material structure applications. The data in this paper can provide a theoretical support for further enhancing the wear resistance of CoCrFeNi-Cu from changing the structures such as polycrystalline or polycrystalline-twin. For industrial applications, this paper can provide a suggest that the single-crystal structure CoCrFeNiCu should be used as a load-bearing material, polycrystalline structure CoCrFeNiCu should be applied in wear-resistant parts, and polycrystalline-twin as a perfect material can be used simultaneously in load-bearing and wear conditions. For example, in the field of marine machinery, the single crystal structure of HEA can be used as a skeleton and substrate to enhance its strength, and at the same time, the outer surface can be covered with a polycrystalline structure to isolate the internal wear of the hull by its water current. In the field of petroleum machinery, high-entropy alloys can maintain high mechanical properties under the premise of corrosion prevention and high temperature resistance, and in the internal structure, the mechanical properties can be enhanced with a single crystal structure, and the microscopic grains of polycrystalline CoCrFeNiCu coating can be used on the exterior to reduce wear.