Publication

Abstract : This study employs a series of molecular dynamics (MD) simulations to investigate the atomistic deformation mechanism of graphene (Gr)-coated Al0.3 CoCrFeNi high-entropy alloy (HEA) during nanoindentation. In the elastic region, both substrates exhibit similar indentation performance. However, at greater indentation depths, the Gr-coated HEA offered higher resistance against indentation, leading to a remarkable 78% increase in hardness compared to pristine HEA. The graphene-coated HEA also shows extended unloading time (52.3ps) compared to the pristine HEA (44.7ps), indicating improved structural recovery. Importantly, graphene coating raises the critical indentation depth for the emergence of the initial embryonic plastic deformation loop (PDL) from 0.628nm in pristine HEA to 0.86nm in the Gr-coated HEA, signifying its hindrance to the elastoplastic transition. Gr coating suppresses dislocation nucleation at first, but eventually stimulates dislocation formation at greater depths, resulting in a higher dislocation density in Gr-coated HEA, which contributes to increased material strength. Additionally, the post-indentation surface morphology of the Gr-coated HEA substrate displays reduced pile-up formation due to the restraining action of the Gr coating. The findings of this study provide a comprehensive understanding of the deformation mechanism in the Gr-coated Al0.3 CoCrFeNi HEA and its potential implications for surface engineering.