Atomic-scale Study On The Interface Properties And Mechanical Behavior Of Graphene Reinforced Aluminium-silicon Alloy Matrix Composites

Aluminum and alloys are widely used in aviation,aerospace and other fields because of their low manufacturing cost,light weight,good machining performance,excellent strength and plasticitybut their properties need to be further improved.Graphene,with excellent mechanical properties and high specific surface area,is an ideal reinforcement for metal matrix composites.At present,there are some problems in the research of graphene/Al matrix composites,such as the reinforcement mechanism and bonding mechanism.The first principle can reveal the nature of interface bonding from the electronic atomic scale,and molecular dynamics can simulate the mechanical behavior of the interface at finite temperature.In this paper,the first principles calculation and molecular dynamics simulation are used to study the interface properties and mechanical behaviors of graphene/Al matrix composites at the atomic scale,providing theoretical basis for the actual pre Paration of graphene/Al matrix composites.In this paper,the interface adhesion work,interface energy,atomic structure and electronic structure of Al/graphene/Al interface are calculated by CASTEP software based on the first principle.The stability and tensile behavior of Al/graphene/Al interface are simulated by lamps software based on molecular dynamics simulation.The effects of defects,the number of graphene layers and Si atoms on the interface properties and mechanical behaviors of Al/graphene/Al were studied.Based on [1???0]Al//[10???0]_graphene,?111?_Al//?0001?graphene orientation relationship,the interface model with the minimum degree of mismatch are established.The interface of Al/ideal graphene is mainly composed of physical bond.With the introduction of Stone-Wales defects,Single-Vacancy defects and Double-Vacancy defect in turn,the adhesion work of the interface increases gradually,and the chemical binding tendency of the vacancy defect interface is obvious,showing the characteristics of polar covalent bond;however,vacancy will increase the interface mismatch energy and reduce the interface stability.The addition of Si improves the interface adhesion work of ideal interface and Stone-Wales defective interface,improves the wettability of Al and complete graphene,suppresses the chemical reaction trend of Single-Vacancy defective and Double-Vacancy defective interface,and the interface atoms are arranged in order.The interface of Al / less graphene / Al and Al / defective graphene / Al can exist stably below 900 K,and the interface is tightly bonded and obviously folded.The bonding strength of the interface increases with the increase of temperature,and it is not sensitive to the types and layers of defects.In different directions of stretching,Al atom and C atom at the interface keep good combination before graphene fracture.The interface is difficult to deform in the process of stretching,which hinders dislocation slip and reduces the plasticity of the material.Both pure Al and composite materials exhibit the best mechanical properties along [1???0],while the mechanical properties along [111] are poor.After the introduction of a few layers of graphene?less than 3 layers?into the interface model,the elastic modulus and tensile strength of the material increase significantly with the increase of the number of layers,while the plasticity decreases,and the graphene can warpage,which alleviates the deformation to a certain extent;however,when the material fails,the interface Al atom and C atom still bond well,and the crack nucleates between the graphene layers,and finally the graphene layer desorption occurs material failure.the introduction of vacancy defects into graphene reduces the elastic model,tensile strength and elongation of the material,and the stress is concentrated on the atoms near the defects.The interface defects provide the crack nucleation site,and it is observed that the crack initiation is related to the sliding of the dislocation in the graphene layer.However,with the introduction of topological defects,the graphene structure is relatively intact,which increases the interface binding ability,but does not provide the crack nucleation site,the dislocation enhancement effect is obvious,the material strength can be improved,and the plastic retention is good.By relaxing the al-SI/ideal graphene/Al-SI interface,Si has a strong precipitation tendency at the interface,and Si is easy to be distributed on the interface.In addition,the addition of Si enhanced graphene's ability to resist deformation and increased the elastic modulus of the material.However,due to precipitation,there were many gaps in the matrix interface and the interface structure was damaged greatly.In the early stage of plastic deformation,crack core existed in the interface,and both the strength and plasticity of the material were weakened to a certain extent.