Enhancing the mechanical properties of Cu crystal substrate by CoCrCuFeNi HEA coating: A molecular dynamics study

In this study, molecular dynamics (MD) simulations were used to analyze the changes in mechanical properties and deformation behavior of CoCrCuFeNi high entropy alloy (HEA) coating with different thicknesses on Cu single crystal substrate. The results indicate the phase structure transition from Face-Centered Cubic (FCC) to Hexagonal Close-Packed (HCP) and Body-Centered Cubic (BCC), an increase in dislocations motion , stacking fault (SF) density, and the density of structural defects as the indenter size increases. Meanwhile, the yield strength ( P y ) and the pile-up height decrease. When the coating thickness is varied, the results show that at thicknesses of t = 20 Å and t = 25 Å, the changes in crystal lattice structure, stacking fault density, the number of FCC and HCP structures , and the elastic modulus percentage are nearly identical. The dislocation density decreases fastest at t = 25 Å, predicting that the plastic deformation process ends early, resulting in better material stability. The hardness value increased with increasing coating thickness, demonstrating that the CoCrCuFeNi HEA coating protected the crystalline Cu substrate structure due to the hardening process, which enhanced the mechanical properties of the Cu substrate.