γ-graphdiyne (γ-GDY) is a new two-dimensional carbon allotrope that has received increasing attention in scientific and engineering fields. The mechanical properties of γ-GDY should be thoroughly understood for realizing their practical applications. Although γ-GDY is synthesized and employed mainly in their bilayer or multilayer forms, previous theoretical studies mainly focused on the single-layer form. To evaluate the characteristics of the multilayer form, the mechanical properties of the bilayer γ-GDY (γ-BGDY) were tested under uniaxial tension using the molecular dynamics simulations. The stress–strain relation of γ-BGDY is highly temperature-dependent and exhibits a brittle-to-ductile transition with increasing temperature. When the temperature is below the critical brittle-to-ductile transition temperature, γ-BGDY cracks in a brittle manner and the fracture strain decreases with increasing temperature. Otherwise, it exhibits ductile characteristics and the fracture strain increases with temperature. Such a temperature-dependent brittle-to-ductile transition is attributed to the interlayer cooperative deformation mechanism, in which the co-rearrangement of neighboring layers is dominated by thermal vibrations of carbon atoms in diacetylenic chains. Furthermore, the brittle-to-ductile transition behavior of γ-BGDY is independent of loading direction and loading rate. The ultimate stress and Young’s modulus decrease at higher temperatures. These results are beneficial for the design of advanced γ-GDY-based devices.

Graphene, a remarkable two-dimensional material, enhances the mechanical properties of high-entropy alloys as a reinforcing phase. This study investigated the influence of vacancy defects in graphene on the strengthening effect of FeNiCrCoCu high-entropy alloy through molecular dynamics simulations. The findings reveal that vacancy defects diminish graphene’s strength, resulting in its premature failure. In tensile tests, graphene with defects lowers the yield stress of the composite, yet it retains the ability to impede dislocations. Conversely, graphene exhibits a more pronounced strengthening effect during compression. Specifically, when the deletion of C atoms is less than 1%, the impact is negligible; between 1% and 6%, the strengthening effect diminishes; and when it surpasses 6%, the strengthening effect virtually ceases to exist. This research offers a theoretical foundation for optimizing graphene-reinforced composites.

Graphene, a remarkable two-dimensional material, enhances the mechanical properties of high entropy alloys as a reinforcing phase. This study uses molecular dynamics to explore the influence of vacant defects in graphene on mechanical properties of alloys. By incorporating graphene with varying vacancy defects into FeNiCrCoCu high entropy alloys containing initial dislocations, tensile and compressive simulations were conducted. Simulation results indicate that graphene, serving as the reinforcing phase in high-entropy alloy (FeNiCrCoCu), experiences a reduction in strength and load-bearing capacity due to its vacancy defects. These defects result in premature failure during the initial stages of strain and diminish the elastic strengthening effect. However, even with defects, graphene retains the ability to enhance the flow stress post-yield. A small number of defects can effectively impede dislocation motion, thereby strengthening the alloy. Conversely, an excessive number of defects allows dislocations to penetrate through the graphene, weakening the strengthening effect. Research has revealed that a defect structure characterized by a homogeneous loss of up to 5% of carbon atoms can enhance both the toughness of graphene and the yield strain of the alloy. Beyond this critical threshold, however, structural stability diminishes, leading to a significant reduction in the strengthening effect.