Study On Fabrication And Properties Of Graphene Reinforced Pure Aluminum Matrix Composites

In this paper,0.5wt.%graphene nenoplate reinforced aluminum composite(0.5wt.%GNP/Al)was fabricated.Orthogonal experiments were used to determine the optimal fabrication parameters,a powder metallurgy method-vacuum hot pressing was used to condense the composite,and the second process-hot extrusion was used to improve the performance of the composite.The microstructure,fracture morphology and phase composition of the composite were compared and analyzed by using OM,SEM,TEM,XRD,EBSD and Raman spectroscopy.At the same time,the tensile strength and elongation of the composite were measured using a universal testing machine.The reinforcement mechanisms of the graphene-reinforced aluminum-based composite were discussed.The main conclusions are as follows:By analyzing the particle size distribution of the 0.5wt.%GNP/A1 powder obtained by different fabrication parameters,the main parameters are obtained by orthogonal experiment method:ball milling time,ball milling speed and ultrasonic time.The analysis using SEM and Raman spectrum results showed that when the ultrasonic time is 90 min,the ball milling time is 6 h,and the ball milling speed is 300 r/min,the best performance would be obtained.By using this parameter,graphene is uniformly dispersed in the matrix.It can be known from the tensile test that the tensile strength of the(0.5wt.%GNP/Al)prepared by the vacuum hot pressing sintering process is significantly higher than that of pure aluminum.When the ball milling time is 6h and the ball milling speed is 300r/min,the mechanical properties of the composite are the best:Elongation is 26.4%,the tensile strength reaches 126.2MPa,which is 25.57%higher than pure aluminum.Analysis of the tensile fracture morphology of the composites by SEM showed that when the ball milling time is short and the ball milling speed is lower,the composites mainly exhibit brittle fracture characteristics.With the increase of the ball milling time and the increase of the ball milling speed,the fracture mode of the composite changes from brittle fracture to a ductile style.The interface of the graphene and the matrix is pretty good and clear,but there is some agglomeration of graphene somewhere,and pieces of Al2O3 was also observed at the grain boundary.According to the tensile test results,the tensile strength of the composite material after hot extrusion is 140.5MPa,which is 10.3%higher than the composite material after hot pressing,and the elongation is 25%,which is slightly higher than the composite material after hot pressing.The comparison between the pure aluminum after hot-extrused and the composite shows that the composite exhibits the phenomenon of elongated grains in the extrusion direction,and equiaxed crystals appear in the vertical surface of the extrusion direction which is mainly due to the fine crystal strengthening effect of graphene.It can be seen from the TEM of the hot-extruded composite that,graphene obviously slip along the extrusion,and dislocations can be clearly observed on the interface of the graphene and the matrix.Big pieces of Al2O3 were spread along the interface,indicating graphene It can effectively hinder the dislocation slip,and the hot extrusion process can effectively promote the dispersion of Al2O3.