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In this study,Cu nanoparticles-coated graphene nanoplatelets(Cu-NPs@GNPs)were synthesized by a simple in situ method with the assistance of NaCl templates and used for reinforcing Al-10Si composites through stir casting process.The experi-mental results showed that the coating of Cu-NPs on the GNPs could compromise the density mismatch between GNPs and metal matrix and effectively hinder the float of GNPs during stirring.The reaction of Cu-NPs and Al matrix could protect the structural integrity of GNPs as well as improve the interfacial wettability between GNPs and the matrix,thus promoting the uniform dispersion of GNPs in the composites.As a result,the as-prepared 0.5 wt％Cu-NPs@GNPs/Al-10Si composite exhibited a tensile strength of 251 MPa(45％higher than the Al-10Si)with a total elongation of 15％.The strengthening effects were mainly attributed to the following three reasons:Firstly,the Cu-NPs coating improved the interfacial bonding between GNPs and Al matrix which promoted the load transfer from the matrix to the GNPs.Secondly,the nanoscale Al2Cu formed by the reaction of Cu-NPs and Al matrix played a role in precipitation strengthening.Thirdly,GNPs refined the silicon phases and improved the monolithic performances of the composites.