Hybrid (Carbon Nanotube plus Graphene Nanoplatelet)/AZ31 Composite with Simultaneously Enhanced Strength and Ductility

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are added into an AZ31 matrix to obtain a composite with high performance via the powder metallurgy (PM) approach. The results reveal that the hybrid (CNT + GNP) reinforcements are dispersed uniformly in the Mg matrix with the help of intertwining and embedding effects of CNTs. The hybrid (CNT + GNP)/AZ31 nanocomposite exhibits simultaneous improvement in strength (315 MPa) and ductility (18.5%) compared with its matrix and nanocomposites reinforced with individual CNTs or GNPs, indicating a synergistic strengthening and toughening effects. The dominant strengthening mechanism might be load transfer generating from the good interface bonding between the hybrid (CNTs + GNPs) nanoreinforcements and the AZ31 matrix. In addition, thermal mismatch strengthening and the Orowan mechanism might also contribute to the increase in strength, and the significant improvement in ductility might mainly benefit from the weakened basal texture and the increase in strain hardening rate caused by the uniformly dispersed hybrid (CNTs + GNPs), which can trap mobile dislocations in the matrix.