Atomic simulations of the formation of twist grain boundary and mechanical properties of graphene/aluminum nanolaminated composites

In this paper, generation of twist grain boundaries (TGBs) and their effects on the mechanical behaviors of graphene/aluminum (Gr/Al) nanolaminated composites were studied via molecular dynamics (MD) method. Crystallization of the Gr/Al composite was conducted to observe the microstructural evolution. The whole evolution process including nucleation and growth of crystals was presented. TGBs were formed between the adjacent crystals after crystallization. The fcc (1 1 1) plane of the Al matrix has three-fold symmetry, so that the TGB angles can range from 0° to 60°. Tensile tests on the Gr/Al composites with TGBs were carried out to study their deformation behavior. The results showed that the graphene-nanoplate (GNP) and TGBs greatly impact on the dislocation behavior of the Al matrix. The dependences of dislocation nucleation and evolution on the TGB angle were uncovered. The TGB also plays a significant role in blocking dislocation motion, and the effectiveness mainly depends on its strength. The variations of yield stress and strain of the Gr/Al composites with different TGB angles were also predicted. It was revealed that failure of the composite is caused by combined action of tensile deformation and shear deformation induced by defects at the GNP edge.