Evaluation on the impact behavior of stir-casted Aluminum composites reinforced with SiC and Gr for lightweight applications

Increasing demands for lightweight materials in various industries, such as aerospace, automotive, and manufacturing, have led to a growing interest in the development of advanced materials with enhanced mechanical properties. One promising avenue for achieving lightweight and high-performance materials is the fabrication of aluminum-based composites reinforced with silicon carbide (SiC) and graphite (Gr) particles through stir casting. The current study examines the impact strength behavior of composites reinforced with AA6063 cast materials that contain different amounts of micron sized SiC particles and 5 weight percent graphite. By using liquid metallurgy, hybrid composites of AA6063, SiC, and Gr were created. The numerous created samples underwent the customary Charpy impact testing, and the impact strength was assessed. By reinforcing SiC and graphite to the aluminum matrix, a substantial increase in impact strength was observed. For the three test samples, the average impact strength of pure aluminum was found to be 7 Joule. Average Impact strength for aluminum with 10% silicon carbide was found to be 8 Joule, which is 14.28% greater than for pure aluminum. The average Impact strength for the composite of aluminum with 20% silicon carbide was 10 Joule, which represents a 42.85% increase in strength over pure aluminum.


Introduction
In order for science and technology to advance, cutting-edge materials must be used in structural applications.In several fields, including the aerospace and military, there is a huge need for innovative materials with exceptional mechanical and physical capabilities [1][2][3].This results from the typical inability of monolithic materials to integrate various mechanical qualities, such as strength and ductility.In order to overcome this problem, metal matrix composites (MMCs) have showed promise, combining or even changing the greatest qualities of a heavily reinforced ductile and robust matrix [4,5].The most significant benefit of composites is their combination of low weight, high stiffness, and strength [6].The interest in the industrial application of aluminum (Al) and alloy-based composites in the automotive and aircraft sectors has steadily developed dramatically in recent years due to their remarkable mechanical qualities [7][8][9].The aluminum alloy AA6063 has excellent mechanical properties and exceptional performance.These remarkable qualities can strengthen the incentive for replacing ferrous metals with adaptable aluminum alloys.Al has weak hardness and strength for the indicated purpose given their low weight.Aluminum matrix composites, a successful method of enhancing the mechanical properties of aluminum alloys, are created by the adding of reinforcement particles to the matrix alloys [10].The usage of nitrides, carbides, oxides, and a few intermetallic compounds as reinforcing particles for AMCs has been widespread.The superior physical and mechanical qualities of silicon carbide (SiC), which is one of the carbide particles, as well as its good wet ability with aluminum, make it incredibly alluring [11].
The development of AMCs can be done by a variety of processing methods, including powder metallurgy, spray casting, squeeze casting, stir casting, ball milling, and friction stir processing.When compared to products created using other procedures, the stir casting process for nanocomposite products is among the most capable, dependable, and affordable [12,13].The high performance A356 -Nano Al2O3 composites were made using the vortex process by Mazahery et al. [14].They demonstrated that as the volume proportion of nanoparticles grew, the composites' hardness increased as well.The enhanced UTS at 10% micro size SiC was found in the tensile test results of as-cast and heat-treated SiC-reinforced Al 7075 matrix composites.Al and Al-AlN nanocomposites' compressive and tensile characteristics have been investigated.They suggested that the inclusion of AlN nanoparticles increased compressive strength.Pre-synthesized composite reinforcement (master metal matrix composite) made by milling alumina with Al and Mg powders was anticipated.They have come to the conclusion that manufacturing Al-A206/alumina composites by adding 100 nm alumina particles while the material is still semisolid leads to a significant increase in strength.A composite material that perfectly satisfies the requirements of a particular application can be generated by selecting the right matrix and reinforcement material combination.A356 reinforced with SiC nanoparticles created by a two-step stir casting process has not been thoroughly and satisfactorily explored in previous study.However, certain studies have shown the production of SiC composites reinforced with aluminum alloy by double stir casting.In particular, AA6063 reinforced with previously mechanically milled aluminum fine powder containing SiC and Graphite nanoparticles through a two-step stir casting process is missing from earlier study.This research focuses on investigating the stir casting method for producing AA6063/SiC/Gr hybrid composites.Additionally covered in detail are the mechanical behavior and morphology of the SiC nanoparticle reinforced AA6063.

Materials and Methods
Aluminum 6063 T5 is used as a matrix material and the Silicon carbide (SiC) and Graphite (Gr) is used as reinforcement.The elemental chemical compositions of matrix Al7075 are expressed in Table 1.

Fabrication of composites
The aluminium alloy (Al6063T5) and Reinforcements (Sic and Graphite) is melted, and composite were casted by stir casting method.Stir casting is a liquid state fabrication method in which dispersed phase (ceramic particles ) is mixed with molten aluminium alloy 6063T5 ( melting temperature of 800 o C achieved using furnace and graphite crucibles) by manual stirring for 30 s.The mixture is then poured into a sand Mold and allows cooling to room temperature.Thereafter, specimens were cut as per standard size for characterizing physical and impact testing.The Figure 1 depicts the steps involved in the fabrication of the AA6063-SiC-Gr composites.

Impact strength testing
Following the guidelines in ASTM E23 Standard is utilized to determine the Charpy test parameter.
Manual stir casting was used to prepare the material for the Charpy test.The Impact test apparatus was used for the Charpy test.To determine the composite's impact strength, standard specimens were employed.the comparison of the attributes of composite materials and those of pure aluminum 6063T5.The 55mm long, 10x10mm2 cross-section Charpy test specimen had a conventional 45 notch that was 2 mm deep.

Results and Discussion
The impact strength of monolithic Al and different composite samples is demonstrated in Figure 4.The impact strength of all produced composites is higher than neat AA6063.This is attributes to the high hardness and strength of reinforcement particles and well distribution of reinforcing particle into the base matrix.For the three test samples, the average impact strength of pure aluminium was found to be 7 Joule.The average impact strength of aluminium containing 10% silicon carbide was determined to be 8 Joule, that is 14.28% more than pure aluminium.The average impact strength for the three samples of aluminium containing 20% silicon carbide was 10Joule, a 42.85% increase in strength over pure aluminium.The impact strength for the composites samples with 10% graphite was determined to be 12 Joule, which is 71.42 percent higher than pure aluminium.In comparison to pure aluminium, the average strength for the composites samples of aluminium containing 20% graphite was determined to be 8Joule, a 14.28% increase.A 10.5% silicon carbide and 5% graphite alloy of aluminium was attained to have an average impact strength of 11.33, which is 61.85% greater than pure aluminium.
The impact strength of the samples of aluminium, which contained 10% graphite and 5% silicon carbide, was found to be 8, 14.28% higher than that of pure aluminium.The samples of aluminium containing 20% silicon carbide and 5% graphite had an average impact strength of 14, which is 100% greater than pure aluminium.The impact strength for the composites samples, which contained 20% graphite and 5% silicon carbide, was 10, 42.85% greater than that of pure aluminium.The findings of this research are comparable with results of existing literature [15][16][17].Fractography was applied to the specimen in order to comprehend the peculiar impact behavior of this composite.The SEM images of the fractured surface of the composites with varying amounts of silicon and graphite is shown in Figure 5(a-b).Normal fractures are caused by one or more of the following mechanisms (a).particle that reinforces fractures; (b).void formation and particle debonding at the interface between the reinforcement and matrix; (c).emergence of gaps and igniting of matrix cracks [18].
The composite fracture is caused by a variety of reasons.They are the processing techniques, the tension that is used, the distribution of reinforcement, and the reinforcing particle shape.Overall, the fracture had a ductile composition.Any material's fracture behavior is influenced by a number of factors, including shape, size, and processing techniques, which determine the material's porosity, strength at the interface, and other characteristics.The dendrite formation and their deformation are observed in the fractography images (Figure 5a-b).Some brittle fractures were observed in Figure 5b.Seep grooves and tear out is also visible.The similar findings are found in existing literature [19,20].

Conclusion
This study aimed to synthesize and investigate the impact strength of Al alloy based composites reinforced with SIC and graphite particles.Stir casting was used to create the hybrid AA6063/SiC/Gr composites.For creating AMMCs with the appropriate characteristics, the stir casting method works well and is reasonably priced.The maximum impact strength of MMC, which is achieved by sample 8 (Al-20% Sic+5% Gr), increases with an increase in the weight percentage of Sic & Gr.Al-20% Sic+5% Gr weight fraction of silicon carbide and graphite particles produced the greatest results.14 Joules were observed as the maximum impact strength for synthetic composites.It is important to note that further research is needed to explore the potential of other mechanical properties of with same reinforcement.Additionally, extending the study to investigate different matrix materials, operating conditions, and environmental factors would contribute to a more comprehensive understanding of the impact behavior for the developed composites.

Figure 1 :
Figure 1: Flow chart of experimental work

Figure 4 .
Figure 4. Average Impact Strength Comparison of pure AA6063

Table 1 :
Chemical composition of aluminum 6063T5