Probing atomistic deformation behavior of graphene-coated Al0.3CoCrFeNi high-entropy alloy under nanoindentation

Abstract

This study employs a series of molecular dynamics (MD) simulations to investigate the atomistic deformation mechanism of graphene (Gr)-coated Al[Formula: see text]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 (52.3[Formula: see text]ps) compared to the pristine HEA (44.7[Formula: see text]ps), indicating improved structural recovery. Importantly, graphene coating raises the critical indentation depth for the emergence of the initial embryonic plastic deformation loop (PDL) from 0.628[Formula: see text]nm in pristine HEA to 0.86[Formula: see text]nm 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 Al[Formula: see text]CoCrFeNi HEA and its potential implications for surface engineering.