Study On Microstructure And Static/dynamic Mechanical Properties Of Graphene Nanoplatelets 5083Al Composites

Graphene has excellent two-dimensional properties,the elastic modulus can reach 1TPa,especially the in-plane stress propagation speed is high?c²2.2 km/s?.As reinforcement,it can quickly disperse the stress concentration of composite at high strain rate.In the field of anti-ballistic,it is a kind of reinforcement with application potential.For this reason,0.6wt.%GNPs/5083Al composite was prepared by pressure infiltration method and formed by extrusion+rolling process.The microstructures of GNPs and their composites were analyzed by X-ray diffraction,Raman spectroscopy,scanning electron microscopy,transmission electron microscopy and atomic force microscopy.The mechanical properties of the composite under static and dynamic loads were tested by electronic universal testing machine and Split-Hopkinson pressure bar,and the damage mechanism of the material under static and dynamic loading was revealed.With the hot-forming process of hot extrusion+hot rolling,the grain size of the Al matrix reduced from 5.48?m to 1.97?m,and the thickness of the GNPs decreased from 300-400 nm to about 100 nm.The number of layers observed in the TEM was within 10 layers,and the GNPs were oriented along the rolling direction.There are two types of bonding interfaces of as-cast GNPs/5083Al composites:Al/GNPs direct bonding interface and Al-MgO-GNPs reactive interface.As-deformed GNPs/5083Al composites have three types of bonding interfaces:Al/GNPs direct bonding interface,Al-MgO-GNPs reactive interface and Al-Al₄C₃-C reactive interface.The hot deformation increased the flexural strength and fracture strain of 0.6wt.%GNPs/5083Al composite by 15.2%and 156.9%,respectively.And the elastic modulus,compressive yield strength,compressive fracture strength and fracture strain were increased by 7.33%,63.2%,7.86%and 81.1%,respectively.Under dynamic compression load,the strain hardening index of as-deformed GNPs/5083Al is higher than that of as-deformed 5083Al,indicating that the addition of GNPs is beneficial to improve the dynamic compressive property of GNPs/5083Al.The strain hardening index of as-cast GNPs/5083Al is higher than that of as-deformed GNPs/5083Al.After thermal deformation of GNPs/5083Al,a large amount of recrystallized structure appeared in the matrix,and the grain size changed from 1.97?m to 1.62?m,and the Al crystal grains appeared along the?220?crystal plane.The G peaks of GNPs shift to the right and the peaks become wider.At the same time,the morphology of GNPs changes from straight to arched,becoming bent,layered and kinked.When the strain rate is less than 2380s^-1,the dynamic compression constitutive model of the as-deformed GNPs/5083Al can be well fitted with the classical Johnson-Cook model.When the strain rate is greater than 2380s^-1,the thermal softening term is introduced to modify the classical J-C model.Afterwards,the dynamic compressive stress-strain curve of GNPs/5083Al composites can be well fitted.