The mechanical and tribological properties of composites of nanographene and an aluminium-metal matrix were studied, as was their corrosion behaviour, in order to develop materials suitable for use as shielding materials

In this investigation, pitting corrosion methods were used to investigate the corrosion behaviour of nanographene oxide-reinforced aluminium-copper metal matrix composites. S1 (AL 100% + 0% Cu + 0% Nano Graphene), S2 (AL 91% + 7% Cu + 2% Nano Graphene), S3 (AL 82% + 14% Cu + 4% Nano Graphene), and S4 (AL 73% + 21% Cu + 6% Nano Graphene) were the sample compositions. Ultrasonic stir casting was utilised to produce the aluminium-copper-nanographene composites. Nanographene was analysed with BET to determine its surface area, porosity volume, etc. The effects of nanographene oxide weight fraction on the corrosion behaviour of aluminium-copper composites were investigated. The surface texture of the corroded material was evaluated with an atomic force microscope, and the hardness was measured with a Vicker's microhardness tester. The results of the experiment revealed that the corrosion rate decreased as the percentage of nanoparticles in the matrix increased up to S3 composition. The microhardness values increased as the weight fractions of reinforcements in the matrix increased. And additional mechanical tests, such as tensile, wear, and flexural, to ascertain the composites' mechanical behaviour.


1.Introduction
Aluminium metal matrix composites (AMMCs) are a group of materials that combine the lightweight properties of aluminium with advanced mechanical and thermal properties through added strength The most commonly hardened component is copper, which provides mechanical strength.Another emerging reinforcement is nanographene, which offers unique properties such as high strength and thermal stability.The mechanical behaviour of materials is an important factor in determining their suitability for different architectural applications.In recent years, aluminium-metal matrix composites (AMMCs) labelled with copper nanographene have received increasing attention due to their improved mechanical properties Understanding the mechanical behaviour of these materials is important and to improve efficiency and expand their potential applications.
The incorporation of copper and nanographene into AMMCs offers several mechanical advantages.Copper with high strength and good ductility, acts as a reinforcing material to provide tensile strength, stiffness and toughness in composites while nanographene, with unique mechanical properties at the nanoscale, contributes to strength, stiffness and wear resistance.Several studies have been conducted to investigate the performance of AMMCs reinforced with copper nanographene.This 1300 (2024) 012028 IOP Publishing doi:10.1088/1757-899X/1300/1/012028 2 study uses various testing methods such as tensile testing, hardness testing and wear testing to evaluate the mechanical properties of the composites.
The addition of copper nanographene significantly improved the tensile properties of AMMCs, enhancing their tensile strength and parameters.This addition also enhanced machinability and toughness, making the composites more suitable for applications requiring high strength and resistance [1].In addition, numerical modelling techniques such as finite element analysis (FEA) have also been used to predict and understand the mechanical behaviour of AMMCs These models provide valuable insights into stress distribution, deformation behaviour and failure mechanisms in composites, contributing to they design and optimize their technology assets.The mechanical behaviour of aluminium-metal matrix composites with copper nanographene filler enhances tensile strength, corrosion resistance, and toughness, enhancing their application in construction, aerospace, automotive, and electronics industries.
Pitting corrosion is a localized form of corrosion that can lead to the formation of small pits or holes on the metal surface, potentially compromising the structural integrity of the material.Understanding the pitting corrosion behaviour of AMMCs is crucial to ensure their long-term durability and reliability [2].Research studies have investigated the pitting corrosion resistance of AMMCs with copper and nanographene, considering factors such as the corrosion potential, corrosion current density, and morphological analysis of the pits formed.These studies have focused on evaluating the corrosion behaviour of the composites in different corrosive environments, such as acidic, alkaline, and chloride-containing solutions [4].
The characterization of nano-scale materials is important to understand their properties and optimize their performance in various applications.For aluminium-metal matrix composites (AMMCs) with copper nanographene reinforcements, growth characteristics such as atomic force microscopy (AFM) and Brunauer-Emmett-Taylor (BET) analysis in analyzing their surface topography porosity play an important role.AFM is a powerful imaging technique that allows high-resolution imaging and measurement of surface topography at the nanoscale.It uses a sharp edge that scans the sample, detects forces between edge and sample and provides a detailed map This method provides valuable information about AMMC surface morphology, roughness and particle distribution, and empowers researchers investigate the effects of copper and nanographene reinforcement on composite microstructure.
BET analysis measures surface area and porosity of materials, providing insight into pore size distribution, surface area, and pore volume.It helps researchers understand the effect of copper and nanographene on porosity and surface area in materials like AMMCs.AFM-BET analysis was used to evaluate surface roughness in AFM composites, showing that nanographene increased smoothness and decreased roughness, highlighting its significant role in 19th-century AMMC surface appearance [4].In another study, BET analysis was used to investigate the porosity and specific surface area of different AMMCs of copper and nanographene materials.The results showed that the addition of nanographene increased the specific surface area of the composites, while copper affected the pore size distribution.These data show the importance of copper and nanographene on the porosity and surface of AMMCs the combination of attributes [5].
In conclusion, AFM and BET characterization techniques provide valuable insights into the surface area, roughness, and porosity of AMMCs incorporated with copper-nanographene fillers These techniques allow researchers to understand the effects of these fillers under the microstructure and surface properties in composites The combination of analysis contributes towards a broader understanding of AMMC and contributes to the development of improved materials with improved performance.
Aluminium alloy was chosen due to its excellent ductility and castability.The Al-Cu-Gr particle composite is manufactured in a pit furnace (model: INDFUR suppliers, Chennai), which is essentially a three-phase resistance furnace that is electrically heated and has a 12.5 kilowatt capacity.It also contains four 14 gauge, A-1-grade heating coils.The tank's capacity is 200 litres.The electrical furnace utilised in this project was a PLC automatic temperature control with electrical resistance type, with a maximum operating temperature of 1,200°C and a control precision of 5 °C for molten aluminium.The electrical stirrer can stir at a maximum speed of 2000 rpm.The process involves melting around 0.450 kg of Al metal matrix alloy in a graphite crucible at 1150°C.Magnesium ribbons are used to improve wettability and ensure uniform distribution of strength.When the temperature reaches 1150°C, nanographene powder is gradually added to the molten metal (2% of the base metal's weight) after preheating it to 600°C.A mechanical stirrer covered with alumina and equipped with four coated blades is used to blend the reinforcement with the molten metal, creating a vortex.The molten metal is stirred forcefully at 500 rpm in an organogas atmosphere to prevent oxidation.To create cast specimens measuring 100 x 16 x 5 mm, the high-temperature molten metal is poured into a preheated cast iron mold at 800°C.

3.Mechanical Testings
The tensile strength of nanocomposites was tested using an electro-mechanical UTM 'Instron Make' at room temperature and a strain rate of 1 x 10 -4 s -1 .Four specimens of Al (base metal), unreinforced S1, and each reinforced composite were fabricated for tensile testing.The results showed that friction stir processing (FSP) of the base matrix led to a 5.94% decrease in ultimate tensile strength, while smaller particle size increased tensile fracture strength [6].The addition of nanoscale second-phase reinforcement particles increased the composites' elastic modulus, yield strengths, ultimate tensile strengths, and tensile failure stresses compared to an S1 matrix without reinforcement.The gradual improvement of properties from the unreinforced S1 matrix to the hybrid composite suggests equal refinement of grains and uniform distribution of dislocations in the matrix.The tensile properties of the unreinforced S1 specimen decreased from 53 m to 18 m while the average particle size decreased.The addition of nanographene to composite samples increases Vickers hardness from Hv 85.44 to Hv 167.However, the hardness decreases with higher amounts of graphene.Composite samples containing 4 weight % of nanographene have lower hardness than those containing 2 weight %.Al/GO composite samples have higher microhardness values than unreinforced Al alloy.The weight percentage of nanoparticles in the Al matrix can be raised by up to 1% without affecting hardness values.The hardness value of metal matrix composites is influenced by reinforcement amount and surface characteristics.The wear rate of hybrid composites made of aluminium-copper-nano graphene (MMCs) was studied using microns as a measure of wear.Sample 3 had the least wear, measuring 78.13 microns.The study found that higher graphene content percentages significantly reduced wear loss in MMCs.Hybrid composites made of Al + 4% Gr exhibited greater wear resistance than unreinforced S1 and other composites, regardless of load and sliding velocity circumstances.The graph depicting the wear rate over time demonstrates how nanoparticles affect the wear rate throughout periodic intervals.The flexural test examines the reaction of composite materials to deflection, using test samples created in accordance with ASTM A: 370 standards.Sample 2 exhibited higher flexural strength due to copper and nanographene content, while its deflection was smaller due to aluminium distribution.The result values of tests are shown in table 1 and represented graphically in figure 1.  , and the Al-nano graphene composites' behaviour of gradually growing surface roughness may be caused by the insertion of nanoscale carbonaceous reinforcement into the Al matrix.An increase in roughness was found to be a common trend in earlier studies [7,8].  .Both of these figures are quite large.The BJH method was applied in order to carry out the computations necessary to determine the related pore size distribution data for nanographene.These results led to the conclusion that the pores are uniform and have a restricted pore size distribution that is centred at 3 nm.The findings of the BET isotherm plot indicate that the particles have a type II isotherm out of a possible 6, which indicates that they are capable of unrestricted mono-multilayer adsorption.This conclusion was reached as a consequence of the fact that the particles have a type II isotherm.The vast majority of the time, this phenomena takes place when adsorption is taking place on powders that are either nonporous or have powders whose diameters are larger than micropores.The inflection point takes place at a moment that is quite near to the end of the process of forming the first monolayer of adsorbed particles.Strong van der Waals interactions between the graphene sheets cause graphene particles to have a tendency to stack on top of one another.Because functionalization increases the likelihood that graphene particles would stack on top of one another, the BET surface area of nanographene decreases as a direct consequence of this behaviour.The setup required for performing BET analysis and analysis graph are shown in the figures 5 and 6 respectively.electrode-electrolyte combination resulted in the polarisation curve.Table 2 gives estimates of the corrosion potential and density based on the polarisation curve.The polarisation curves show that when the amount of nanographene in the Al alloy grows, the current density rises and the corrosion potential falls.Corrosion resistance is found to diminish with rising corrosion current density.The experiment's findings showed that how effectively composites resist corrosion depends on the weight proportion of the reinforcements in the matrix.Figure 7 depicts the pitting corrosion setup.

SAMPLE TENSILE STRENGTH HARDNESS AVERAGE WEAR FLEXURAL
The mean Ecorr and Epit values of the Al/nano GO composites are calculated using potential dynamic techniques (Table 3).

Table 2: Pitting Corrosion Values of Samples
The resistance of a material can be calculated using the values of Epit, Ecorr, and the passive range.With this figure, the material's corrosion resistance rises.Despite graphene being a nobler metal than aluminium, which would be predicted to boost corrosion resistance and shift Ecorr values to higher positive values, no appreciable variations were detected in the solution potentials of the graphene-containing and graphene-free materials.However, there are noticeable improvements in passive range values between S2 and S3, as well as between alloys with and without reinforcement.Due to its substantially higher Epit value compared to the other materials examined, the S3's passive range value was the highest.According to these results, composite materials have better corrosion resistance than unreinforced alloys electrochemically and composites are electrochemically superior to unreinforced alloys.Copper-

Conclusion
• By changing the weight proportion of reinforcements, stir casting composites of Al, Copper, and Nano Graphene may be made successfully.• Higher tensile strength is observed in composite S4 (AL 73% + 21%Cu + 6% Nano Graphene) due to the formation strong bond among Copper, nano Graphene and Alcompound.• The addition of varied amounts of reinforcement to the base material is found to boost hardness; the composite S4 (AL 73% + 21% Cu + 6% Nano Graphene) achieves the highest value.This is because Cu/Nano Graphene is present in the Al compound.

Figure 5 : 6 :. Tribological study 5 . 1
Figure 5: BET Analysis Set-up Figure 6: Graph showing BET Analysis Figure 18 displays the polarisation curves for various Al-nanographene composite compositions.For studying the corrosion behaviours of Al/nano GO composites under various circumstances, polarisation curves are absolutely necessary.Plotting the current density (I) vs. electrode potential (E) for a particular

Figure 7 : 8 :
Figure 7: Pitting Corrosion Setup Figure 8: Polarization Curves of Samples containing materials exhibit higher corrosion resistance than unreinforced materials, outperforming electrochemically.The addition of alumina fibres affects corrosion behavior by physically restricting the course of corrosion and resulting in a finer microstructure.This results in less micro segregation and inhomogeneities, preventing localised corrosion in the specimen[9,10,11]

Sample vs Tensile Strength Sample vs Hardness Number Sample Vs Wear rate Sample Vs Flexural strength Samples for wear Test Flexural Test Samples Samples for Tensile Test
It has been discovered that, in comparison to other combinations, adding copper to a nanographene compound increases the attribute of flexural strength because a strong link is formed.• It has been shown that the addition of various reinforcements to the base material increases wear resistance.The composite S3 (AL 82% + 14% Cu + 4% Nano Graphene) exhibits the lowest wear loss; this is because Cu/Nano Graphene is present in the Al compound.• The composite S3 (AL 82% + 14% Cu + 4% Nano Graphene) has much higher corrosion resistance compared to other composites because graphene increases corrosion resistance, which is a crucial quality for maritime applications and automotive radiators, among other places.• Characterization of samples of Al/Copper/Nano Graphene composites made by varying wt% of reinforcements are done by AFM, BET, SEM and EDAX.