Nanoindentation Mechanical Properties of FeCoCrNiCu High Entropy Alloys: A Molecular Dynamics Study

Abstract

Nanoindentation of FeCoCrNiCu high entropy alloys (HEAs) was simulated by molecular dynamics (MD) simulation to investigate the mechanical properties of HEAs in terms of Young’s modulus, dislocation, and shear strain. And the effects of loading rates and temperatures on the deformation of alloy matrix were studied. The young's modulus obtained by fitting was approximately consistent with the experimental results. In nanoindentation, HEAs underwent elastic deformation first, and then began plastic deformation. Dislocations continuously nucleated and expanded under the indenter and eventually formed dislocation loops. Owing to the complex element composition and the strain gradient effect, the distribution of shear strain in the alloy was not uniform. The loading rate had an effect on the growth of dislocation, and the critical plastic depth also increased with the increase of loading rate. The deformation of HEAs was significantly affected by temperature. With the increase of indentation temperature, atoms moved more violently, and the matrix was easily deformed. The indentation force increased obviously at low temperature, because the low temperature itself reduced the atomic mobility and facilitated the formation of twins, which further strengthened the matrix.

Keywords

• high entropy alloys
• molecular dynamics
• nanoindentation
• temperature
• loading rate