Molecular dynamics studies on the sintering and mechanical behaviors of graphene nanoplatelet reinforced aluminum matrix composites

Abstract

The sintering process of graphene nanoplatelet (GNP) reinforced aluminum matrix composite powder was simulated by molecular dynamics method. The effects of Al nanoparticle size and sintering temperature on sintering behavior were studied. Uniaxial tensile simulation was applied to study the mechanical properties of sintered composites. The results show that the nanoparticle size and sintering temperature have significant effects on the sintering behavior of the composites. Smaller size nanoparticle system has lower melting point, which requires lower sintering temperature. Larger size particle system requires longer sintering time and higher sintering temperature. At lower temperatures, the main coalescence mechanisms of nanoparticle systems are surface diffusion and grain boundary diffusion. When the temperature is close to the melting point, volume diffusion and surface diffusion dominate. Tensile simulation results of sintered composites show that the addition of GNP can greatly improve the mechanical properties of the composites. Dislocation reinforcement and stress transfer are the main reinforcement mechanisms.

Atomistic Study on the Sintering Process and the Strengthening Mechanism of Al-Graphene System

“…Therefore, the same number of Al atoms in the Al-SLG composites occupies a smaller space, as presented in Table 2 . These indicate that graphene is conducive to promoting the sintering progress and improving the density of sintered structures, which can be ascribed to the higher binding energy between Al atoms and graphene [ 16 ], providing more energy for Al motions approaching graphene.…”

“…The NPT ensemble is also applied in the entire sintering process. It should be noted that parameter settings above such as the heating and cooling rate are selected according to the similar sintering process of the Al–graphene system in reference [ 16 ].…”

“…The eam potential is applied to the interaction between Al atoms [ 19 ], the file of which can be obtained from the LAMMPS library, and a simple sintering model of pure Al bulk is carried out to verify this potential file by checking the melting point ( Figure 1 b). The airebo potential is used to link carbon atoms in graphene [ 20 ], as commonly applied in [ 16 , 21 , 22 ] to mimic graphene; the Al–C interaction takes the style of the morse potential [ 23 ], which is proved to be more suitable for the interface between metal and graphene [ 24 ].…”

“…Wejrzanowski et al checked the melting behavior of Al–Si nanolayers with two different thicknesses to explain a noticeable decrease in the melting temperature [ 15 ]. He et al studied the sintering process of graphene nanoplatelet-reinforced aluminum matrix composite powder and the mechanical properties of sintered composites [ 16 ]. Kumar et al explored the orientation of aluminum atoms along with the mechanical properties of an aluminum/graphene nanocomposite, after a cooling process from 2500 K to 10 K [ 17 ].…”

“…The studies discussing the Al–graphene composite system often suffer the drawbacks of neglected details in initial models, where the size of graphene is equal to the plane size of the composite system. Such a sandwich-like structure under tension will give rise to a serious deformation in graphene bearing most of the direct stress, and the tensile strength can be as high as 14 GPa [ 16 ]. Although the graphene size in [ 17 ] is more reasonable, a crystallization process rather than sintering process is employed to prepare the Al–graphene composite and multilayer graphene has not been discussed.…”