Study On Dynamic Mechanical Properties Of Graphene-Reinforced 6061 Aluminum Matrix Composites

The graphene-reinforced 6061 aluminum matrix composite prepared by powder metallurgy method was used as the research object,and its dynamic mechanical properties were studied in two aspects: experimental and numerical simulation,and the main work was as follows:(1)The microstructure of the composites before and after dynamic compression was analyzed by optical microscopy,scanning electron microscopy(SEM),XRD,etc.,and the results showed that graphene in the composites before dynamic compression was distributed at the grain boundaries,and the matrix material was mainly mechanically bonded,and the binding interface was not generated by Al4C3.By analyzing the macroscopic morphology and microstructure after dynamic compression experiment,it is found that the deformation and failure of composite materials are due to grain deformation,composite interface damage,internal defects and crack propagation,etc.,and the fracture mode of composite materials is cleavage fracture.(2)The dynamic compression performance of 0.3wt%,0.5wt%,0.75wt% and 1wt%graphene/6061 Al composites at strain rates of 2000/s,3000/s and 4500/s was studied by separating Hopkinson pressure rods,and the stress-strain curves of the composites at different strain rates were obtained.The results show that the graphene/6061 Al composite has a significant strain rate effect.With the increase of strain rate,its flow stress and yield strength increase accordingly,and there is an obvious hardening phenomenon of strain rate.In addition,under the same content,it was found that the yield strength of 0.3wt%graphene/6061 Al composite material increased the most,reaching more than 33.7%.At the strain rate of 4500/s,the yield strength of 0.5wt% graphene/6061 Al composite material increased by 28.9%,and the dynamic mechanical properties were the best,while the yield strength of 1wt% graphene/6061 Al composite material increased the least due to the low degree of reinforcement phase dispersion.(3)By measuring the Vickers hardness of the composite,it was found that the content of graphene had a strengthening effect on the hardness of the composite.Before dynamic compression,compared with the matrix material,the overall hardness is increased by more than 17%,up to 29.3%,of which when the graphene content is 0.5wt%,the hardness of the composite material is the largest,and the hardness of the composite material with graphene content of 1wt% is the smallest compared to other composite materials,which is due to the low dispersion degree of graphene,which reduces the density of the material.After dynamic compression,the hardness of the sample increases due to dislocation migration and fine-grain strengthening factors.Among them,the composite material with a graphene content of 0.75wt% had the largest increase in hardness after compression,increasing by nearly 22.2%.(4)According to the yield of the composite in the dynamic compression test under different strain rates,the graphene/6061 aluminum matrix composite is more strain rate sensitive than the 6061 aluminum matrix,and the composite material with graphene content of 1wt% is the most sensitive to strain rate.(5)The finite element software DIGIMAT and ABAQUS jointly established a three-dimensional model of graphene-reinforced 6061 Al composite,simulated the dynamic loading process,and studied the deformation behavior and damage mechanism of graphene/6061 Al composite.The results show that the damage mechanism of composite materials is mainly the interfacial damage failure mechanism.Mainly because graphene does not deform under high-speed impact,stress concentration occurs around graphene,the stress received by graphene is transmitted through the interface between the two,directly reacting on the matrix,causing damage to the matrix,with the increase of strain rate,the stress range of the interface area expands,so that the matrix has serious plastic deformation,resulting in interface damage.(6)By comparing the experimental results with the numerical simulation results,it is found that the mechanical change trend of the two is similar,the numerical simulation results are slightly higher than the experimental results,and the overall error is within10%,which maintains good consistency,indicating the effectiveness of numerical simulation calculation.