Enhanced dislocation obstruction in nanolaminated graphene/Cu composite as revealed by stress relaxation experiments

The strengthening mechanism of graphene in graphene/Cu nanolaminated composites was investigated by progressive compressive stress relaxation experiments in the microplastic regime. The results reveal that, when the loading effect of graphene is lacking, the higher yield strength of the composite is attributed to the higher longrange internal stress and effective stress at the yield point. The derived activation volumes imply a much higher critical resolved shear stress required for dislocation cross-slip and/or nucleation at/near grain boundaries in the graphene/Cu composite than that in the unreinforced Cu matrix, indicating that graphene may significantly affect the intrinsic deformation mechanism of the matrix. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.