Molecular dynamics-based explanation of the reinforcement geometry effects on CNT/graphene-reinforced AlCoCrFeNi high-entropy alloys.

Designing lightweight structural materials often drives the research community to explore high-strength nanomaterials as reinforcement agents. These reinforcements hold significant potential to enhance functional properties while substantially reducing weight. However, despite their promising role in material design, the underlying mechanisms behind their exceptional behaviour remain insufficiently understood. Motivated by this, the present study aims to elucidate the underlying mechanism that contributes to the improved mechanical performance of graphene (Gr)/carbon nanotube (CNT)-reinforced AlCoCrFeNi high-entropy alloys (HEAs) via molecular dynamics simulations. In this study, a series of atomistic models of CNT/graphene-reinforced high-entropy alloy (HEA) configurations (featuring progressively increased surface area of CNT/graphene reinforcements) were developed and mechanically characterized. The influence of reinforcement's shape and geometry on the mechanical performance of HEA composites is explained by observing the load distribution, dislocation analysis, deformation mechanism, and failure mechanism. The investigation revealed that using CNT-S4, which has the highest surface area among the CNT reinforcements, resulted in approximately a 30% increase in failure strength compared to the graphene-reinforced configuration (Gr-S4). The comparative analysis of the deformation mechanisms in the HEA-CNT S4 and HEA-Gr S4 configurations reveals notable differences in their plastic responses. While both models undergo plastic deformation during yielding, the HEA-CNT S4 model interestingly exhibits fewer and less intense shear bands, suggesting a delayed onset of plasticity. With increase in the surface area of the reinforcement, the specific strength (yield strength-to-density ratio) improved in both systems, with the S4 model reaching the highest values of 2673.03 kN m/kg for HEA-CNT and 2077.27 kN m/kg for HEA-Gr. This trend underscores the superior reinforcing efficiency of CNTs in enhancing the mechanical performance while minimizing the density (weight) of HEAs. Overall, this work highlights the critical role of the geometry and interfacial interaction of carbon-based reinforcements in optimizing the mechanical performance of HEA-based nanocomposites and provides valuable atomistic insights for the design of high-performance structural materials.