Nanomechanics of 3D graphene networks in high-entropy alloy matrix nanocomposites

In this study, molecular dynamics simulations are carried out to investigate the tensile behavior of GN/CoCrFeMnNi high-entropy alloy (HEA) nanocomposites. By comparing with pure GN and pure CoCrFeMnNi HEA, we unveil a remarkable enhancement in strength and toughness conferred by the three-dimensional graphene network (3D GN). Before the interface separation, 3D GN and the HEA matrix deform in harmony, effectively distributing loads. Post-separation, the continuous and robust 3D GN bears the brunt of the load, alleviating stress concentration through global deformation. The mechanical interlocking between 3D GN and the matrix acts as a formidable barrier to dislocation motion, significantly increasing the material's resistance to deformation. Notably, while pure CoCrFeMnNi HEA fails via matrix fracture, the failure of the composite is dominated by graphene network (GN) breakage. During crack propagation, 3D GN forms a bridge across the crack, reducing stress at the crack tip and enhancing toughness. Additionally, the HEA matrix provides critical support to the GN, reducing its potential energy and stabilizing its structural configuration. The presence of Cr atoms, which form strong chemical bonds with both the matrix and GN, further optimizes load transfer efficiency at the interface, facilitating the effective utilization of GN's exceptional mechanical properties. These molecular dynamics simulation results are validated by experimental findings. These atomic-scale insights into the reinforcement and toughening mechanisms of GN/CoCrFeMnNi HEA nanocomposites hold great promise for the development of advanced structural materials.