Unusual plastic deformation mechanism in copper-high entropy alloy nanocomposites: Insights from molecular dynamics simulations

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In this study, molecular dynamics simulations are employed to investigate the mechanical behaviors of copper/high-entropy-alloy nanocomposites, in which high-entropy alloy nanowires are embedded in copper matrix. The obtained results show that the mechanical properties of these nanocomposites are significantly affected by the volume fraction of high entropy alloy nanowires. Specifically, the Young’s modulus of the nanocomposites increases linearly with increasing volume fraction of nanowires. However, the yielding stress and ultimate tensile strength increase nonlinearly with increasing nanowire volume fraction from 0.1 to 0.5, while opposite trends are obtained as the volume fraction further increases to 0.6. Moreover, distinct mechanical characteristics are observed in nanocomposites with nanowire volume fractions below and above 0.5. Nanocomposites with a nanowire volume fraction below 0.5 exhibit four distinguishable regimes, while those with a nanowire volume fraction above 0.5 present six distinct regimes. Notably, partial dislocations and stacking faults are highly activated inside the copper matrix in nanocomposites with a nanowire volume fraction below 0.5 but within both the copper matrix and high entropy alloy nanowires in nanocomposites with a volume fraction exceeding 0.5. Furthermore, the study highlights the significant impact of strain rate on the plastic deformation of nanocomposites. Nanocomposites with a smaller volume fraction of nanowires demonstrate a higher strain rate sensitivity compared to those possessing a larger volume fraction. In addition, the mechanical properties of Cu/HEA nanocomposites significantly depend on temperature.