Effect Of Rare Earth Ce And Solution Treatment On Corrosion Property Of ADC12-GNPs Composite

Aluminum alloy materials are often used in the industries of chemical industry,electronics,construction and transportation due to its merit of low density,high mechanical properties and relatively cheap price.With the continuous development of science and technology,more and more industries are limited by material properties and enter the bottleneck period.Many industries have improved their expectations on aluminum alloy properties,which are characterized by lightweight,excellent corrosion resistance and mechanical properties.The mechanical properties of aluminum alloy are significantly improved by the GNPs,but the corrosion resistance of the composite is reduced,and the reduction of corrosion resistance will be negatively feedback to the mechanical properties during application.Therefore,how to improve the corrosion resistance of GNPs reinforced aluminum matrix composite has great research significance.In this paper,the microstructure of ADC12-GNPs composite was analyzed,and electrochemical tests,weight loss hydrogen evolution tests and corrosion morphology observation after immersion were carried out to characterize the corrosion resistance of ADC12-0.9GNPs composite.The research in this article supplies theoretical support for the subsequent acquisition of aluminum alloys with excellent corrosion resistanceThe microstructure of ADC12-0.9GNPs composite is changed after solution treatment.The long silicon phase is fused into short strips,and the short silicon phase is gradually changed into spherical shape.In addition,the Al₂Cu phase dissolves into the matrix.These significant changes are related to the excellent thermal conductivity of graphene.The change in the size of the silicon phase and the dissolution of the Al₂Cu phase effectively weakens the damage of the micro-couple corrosion to the alloy,and reduce the corrosion rate of the ADC12-0.9GNPs composite.The electrochemistry result shows that the ADC12-0.9GNPs/ST composite has the highest corrosion voltage and the lowest corrosion current density,which are-0.589 V and 7.57μA·cm^-2respectively.And the corrosion current density is smaller than that of ADC12-0.9GNPs composite without solution treatment(20.92μA·cm^-2)by 63.8%.The ADC12-0.9GNPs/ST（520°C,5 h）composite also corresponds to the largest polarization resistance（876.62Ω·cm²）,which is 6.5 times than that of the ADC12-0.9GNPs composite（116.60Ω·cm²）.The weight loss and hydrogen evolution test results show that the weight loss rate and hydrogen evolution rate of ADC12-0.9GNPs composites are reduced after solution treatment,and ADC12-0.9GNPs/ST（520°C,5 h）composite have the smallest weight loss rate and hydrogen evolution rate,which are 0.60 mg.cm^-2.h^-1 and 0.46 m L.cm^-2.h^-1,respectively.The dispersed GNPs in the ADC12-0.9GNPs/ST composite forms dispersed heat transfer medium,which enables the Si phase in the composite to cool rapidly and become finer and rounder.However,the dispersed graphene means that more cathode phases are generated,which forms more micro-couples and reduces the corrosion resistance of the ADC12-0.9GNPs/ST composite.The electrochemistry result in 0.1mol/L HCl solution shows that the corrosion potential,corrosion current density and polarization resistance of ADC12-0.9GNPs non-dispersed/ST composite are-0.588 V,5.34μA·cm^-2 and 1002.74Ω·cm² respectively.The corrosion potential（-0.588 V）,corrosion current density(5.34μA·cm^-2),and polarization resistance（1002.74Ω·cm²）of ADC12-0.9GNPs non-dispersed/ST composite show great corrosion resistance.After ultrasonic treatment of dispersed GNPs.The corrosion potential（-0.591 V）,corrosion current density(7.02μA·cm^-2),and polarization resistance（869.72Ω·cm²）of ADC12-0.9GNPs composites reveal poor corrosion resistance.Optical microscope（OM）and scanning electron microscope（SEM）in situ corrosion consequences indicate that the GNPs phase and iron-rich phase are harmful to the corrosion resistance of ADC12-0.9GNPs composites.Compared with the agglomerated GNPs,the dispersed GNPs lead to more severe local corrosion in the vicinity,which leads to the dissolution of the surroundingα-Al matrix by point and surface.Compared with the agglomerated GNPs,the dispersed GNPs lead to more severe local corrosion at the grain boundaries,which is resulting in the dissolution of the surroundingα-Al matrix from point to surface.The addition of rare earth forms the Al-Si-Cu-Ce rare earth phase,which consumes part of the Cu atoms and reduces the formation of the Al₂Cu phase in the composite.In addition,the Si phase and the iron-rich phase are effectively refined.The addition of rare earths increases the hardness of ADC12-0.9GNPs composite by refining grains and generating high hardness rare earth phases.The hardness test shows that the microhardness of ADC12-0.9GNPs composite after adding rare earth Ce increase first and then decrease.The hardness of ADC12-0.9GNPs composite reaches the maximum 146 HV when rare earth addition is 0.6wt%.The refining effect of rare earth and the reduction of Al₂Cu phase reduce the corrosion rate of ADC12-0.9GNPs composite.Electrochemistry test show that the corrosion voltage of ADC12-0.9GNPs-0.6Ce reaches-0.587 V,which is higher than that of ADC12-0.9GNPs（-0.655 V）by10.4%.The corrosion current density is 9.60μA·cm^-2,which is higher than that of ADC12-0.9GNPs(20.92μA·cm^-2)decreased by 54.1%.Meanwhile,the polarization resistance of ADC12-0.9GNPs-0.6Ce was largest（643.18Ω·cm²）,which is 5.52 times of ADC12-0.9GNPs（116.60Ω·cm²）.