| Aluminium and its alloys have a series of advantages when they are compared with other metals and alloys which used commonly,such as low density,high strength,high hardness,strong wear resistance and corrosion resistance.Therefore,it has broad application prospects in many important fields.However,with the development of science and technology,each industry has put forward higher requirements on their Strength,Hardness,Corrosion Resistance and Production Cost.At the same time,aluminium and its alloys also have some shortcomings.These factors require us to explore more perfect aluminium alloy products from the aspects of preparation technology of aluminium and aluminium alloys.In this paper,Al-Mn-GNPs composite coatings were successfully prepared on 7075 aluminum alloy substrates by adding graphene to the organic system of AlCl3+LiAlH4+MnCl2 with the tetrahydrofuran and benzene.As follows are the main work and conclusions in this paper:（1）The preparation process of tetrahydrofuran and benzene organic system of AlCl3+LiAlH4+MnCl2 was optimized.On the basis of the original preparation,the effects of supernatant and graphene addition sequence on the properties of the composite coatings were investigated,and the optimal bath configuration process was obtained:Making the preparation for THF Solution with LiAlH4（A liquid）→Making the preparation for C6H6 Solution with AlCl3（B liquid）→Adding the liquid A to the liquid B then stirring it.→Adding the MnCl2 and then stirring it→Adding the graphene and then stirring it→Taking the supernatant of the stationary system solution as electroplating solution.（2）The Al-Mn-GNPs composite coatings were characterized by SEM,EDS,XRD and RAMAN.The morphology and composition of the composite coating were obtained,and the existence of GNPs in the coating was proved.The ratio of Al to Mn in the coating tends to be stable between 9:1 and 7:1;the Mn changes the crystal form of Al and grows in the amorphous state of the alloy.（3）The experimental conditions for the preparation of Al-Mn-GNPs composite coatings were explored by orthogonal test,and the optimum and concise experimental process was designed according to the orthogonal test.the order of the influence of each process parameter on the microhardness of the Al-Mn-GNPs composite coating is:graphene concentration>stirring speed>current density>plating time.the order of the influence on the friction coefficient of composite coating is:graphene concentration>current density>stirring speed>plating time.Meanwhile,the optimum process conditions were obtained:the graphene concentration was 3 g/L,the current density was 7 A/dm2,the stirring speed was 200 r/min and the electroplating time was45 min.（4）Using single factor experiments,the effects of various process parameters on the properties of Al-Mn-GNPs composite coatings were investigated comprehensively.The optimum process conditions were obtained again:When microhardness and friction coefficient were used as evaluation indexes,the best test conditions were obtained:the graphene concentration was 2.5 g/L,the current density was 7 A/dm2,the stirring speed was 200 r/min and the electroplating time was 45 min. |
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