Introduction

The need for composites (hybrid materials)/green composites is rapidly increasing. One of the main reasons for this is that such composites have good mechanical and chemical characteristics. The inclusion of reinforcing agents/materials to the primary or base material significantly improves its properties. Another motive for switching from traditional to hybrid materials is to reduce pollution by recycling the trash from various sources and using it as reinforcements. Low-density, low-cost materials with strong mechanical characteristics have a wide range of applications in the marine, aircraft, and automobile industries, hence their development is very critical. Scientists were driven to develop hybrid materials by reusing industrial wastes due to a lack of raw resources and an increase in dangerous pollutants in the atmosphere. The industries producing these particles emit a huge amount of greenhouse gases such as N2O3, CH4 and CO2 [1]. These types of waste usage have grown in popularity in recent years, and this form of beneficial utilization is known as green manufacturing. Nowadays, instead of employing traditional raw materials, researchers and experts all over the world are focused on the development of such green manufacturing methods. Green manufacturing is defined as the use of waste materials to reduce detrimental impacts and create hybrid and innovative materials or products that do not affect the environment. Aluminium is used in a variety of sectors, including cans, foils, cooking utensils, window frames, beer kegs, automobiles, and aeroplane parts, due to its lightweight and high mechanical qualities. Because of the changing (improved) characteristics of Al after the inclusion of reinforcements, aluminium-based metal matrix composites (AMC) are also in high demand. The use of reinforcements sets the basic material (Al) different from other higher-order (expensive) metals in terms of characteristics. Heat sinks, microwaves, microchips, CPUs, aircraft wings, and other components made of AMC are in high demand in the electronics industry [1,2,3,4]. To build AMCs, most prior studies have employed traditional reinforcing agents such as SiC, Al2O3, Si3N4, and TiC. The downside of utilizing such reinforcements is that they are extremely expensive and have densities greater than Al, thus they are not suitable for developing a low-density composite. Table 1 shows the experimental values of reinforcing agent density. Agro waste items containing carbides and ceramic oxides, such as eggshell ash (ESA), groundnut shell (GSA), and rice husk ash (RHA), are sufficient to improve the mechanical and physical qualities of the base material.

Table 1 The experimental values of reinforcements
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They also have low densities, hence they might be used to make metal matrix composites (MMCs) with low densities. The second obvious benefit of using such wastes is that pollution might be reduced, as these types of agricultural products emit a lot of hazardous pollutants. Because it is estimated that by 2030, roughly 70% of individuals will be suffering from a lung-related ailment, pollution control will be critical [5,6,7,8]. The two principal pollution-causing agents are ESA and RHA, and the best approach to solve the problem is to put the waste to constructive use. If utilized as reinforcements, ESA and RHA could improve the underlying material's mechanical and physical qualities (Al). ESA is a waste product of the food industry, and it must be properly disposed of or it may cause major environmental problems. Because of its chemical composition and accessibility, various researchers have attempted to employ ESA for a variety of purposes. Egg shell's unique features make it a popular bio-filler reinforcing agent, improving the chemical and mechanical and physical properties of the base material (Al). Another advantage of using Eggshell (ES) to reinforce base material is its bulk availability, lightweight, cost-effectiveness, and environmental friendliness. Aluminium reinforcement with ES and investigation of its modified properties, such as mechanical, chemical, and thermal, is a relatively new field of study. Different casting processes, such as mechanical and electromagnetic stir casting, are used to synthesize such compounds [9, 10]. AMMC has better characteristics relative to the base material because of its even distribution and good contact of reinforcing particles in the metal matrix. Employed various ratios and particle sizes of ES as a bio-filler in propylene-based composites [12,13,14,15,16], claiming that as the value of Young's modulus increases, so does the amount of ES [11]. The use of various reinforcing particles in the production of materials is shown in Table 2.

Table 2 Utilization of waste material as reinforcement in the development of composite material
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Materials and Methods

Matrix Material

The matrix phase used in the current study was AA3105 aluminium alloy. As a result of its great mechanical strength, this alloy is used in the fabrication of aircraft structures (fuselages and wings). Since AA3105 can withstand extreme temperatures (melting point ~ 635–654 °C), it is also employed in the production of high-temperature parts such as engines, shafts, brake rotors, and other vehicle parts that require high-strength yet lightweight materials [19]. The elemental composition in wt.% of AA3105, as well as its mechanical properties, is discussed in Tables 3 and 4 respectively.

Table 3 Composition of AA3105 alloy (wt.%)
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Table 4 Mechanical properties of AA3105 alloy [39]
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Eggshell as Primary Reinforcement Material

As primary reinforcing particles, waste eggshell has been used in the fabrication of an aluminium-based composite material. Ceramic particles comprise the majority of ES, with CaCO3 accounting for 94%, MgCO3 for 1%, Ca3(PO4)2 for 1%, and miscellaneous organic matter accounting for the remaining 4% [10]. Eggshells were acquired from local supermarkets, washed well, and then sun-dried for around 6 h to eliminate any moisture content as well as the covering ES layer. The powdered form of ES was obtained by ball milling this dry ESs. These powdered ES were then carbonized for up to 4 h at a temperature of approximately 550 °C to remove the carbonaceous particles from the ES powder. Carbonized eggshell particles were reported to have an average particle size of 25 μm. The formation of carbonized eggshell powder from waste eggshell recovered from foodstuff is depicted in Fig. 1. Scanning Electron Microscopy (SEM) images of carbonized ES powder has been shown in Fig. 2. The carbonized eggshell was subjected to X-ray diffraction (XRD) analysis to determine a clear picture of reinforcement, i.e., Eggshell. The resulting XRD pattern of carbonized ES is depicted in detail in Fig. 3. The XRD pattern of ES clearly shows that CaCO3 has the largest proportion, following by Mg.

Fig. 1
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Formation of carbonized eggshell powder from waste eggshell collected from the food industry

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Fig. 2
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SEM image of Eggshell powder

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Fig. 3
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Powder XRD of Carbonized Eggshell Powder

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RHA as Secondary Reinforcement Material

Waste rice husk ash (RHA) was chosen as the secondary reinforcing material for the development of AMMC. Rice husk was obtained from a local rice factory in India, rinsed with water to eliminate dust and other pollutants, and then air-dried at atmospheric temperature (25 °C) for 24 h. To remove any moisture and organic content, this cleansed RH was heated at 300 °C for 2–3 h. As the organic component began to char, the husk colour went from yellowish to mild black during drying. Then it's heated for roughly 12 h at 700 °C to remove the carbonaceous material's influence. After heating it again, the black tint turned greyish white. Finally, rice husk ash has been generated and is ready to be employed as a metal matrix reinforcing material. Figure 4 depicts the creation of rice husk ash from raw rice husk gathered from a local rice company. Figure 5 shows the XRD of powder rice husk ash; it is clear that SiO2 is the most abundant ingredient in RHA powder, followed by CaO and Fe2O3.

Fig. 4
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Formation of RHA from waste rice husk collected from rice industry

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Fig. 5
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Powder XRD of RHA powder

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Ball-Milling Process of Reinforcement Particles

Figure 6 depicts the procedure of ball-milling reinforcing particles to create single-entity reinforcements. While the stirring process is in progress, building a composite material is a difficult operation due to the disparity in densities of numerous reinforcing. The key issue was adequate reinforcing particle placement in the metal matrix, as some tend to float while others settle into the matrix. Table 5 shows the different parameters of ball mills used to prepare the AMMC. The make and model of the ball-milling machine are RETSCH and Planetary Ball Mill PM 100 respectively. As a result, the problem of mismatched densities might be eliminated by using the ball milling technique. Ball-milling of carbonized eggshell powder and RHA was used in this investigation to create a single entity powder. The ball-milling process has taken up to 75 h to complete.

Fig. 6
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Line diagram of the ball-milling process

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Table 5 Parameters of the different ball- mills used to prepare the AMMC
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Development of Composite Material

Figure 7 depicts a line diagram of the stir casting method used to develop composite materials. As a matrix material, AA 3105 was used. Before mixing in the matrix material, carbonized eggshell powder and rice husk ash (RHA) were preheated at 300 °C and 200 °C, respectively. The single entity of ball-milled carbonized eggshell particles and RHA was warmed at 250 °C. In a muffle furnace, AA3105 was melted. As soon as the temperature of metal matrix temperature exceeds 690 °C, reinforcing particles were introduced. Squeeze and pressure were applied to the UTM machine in the mushy phase to remove pores and irregular reinforcing surface structure. Table 6 shows the composition of the produced composite material with reinforcing weight percent. Five composite materials with different compositions (Table 6) were made, and the physical and mechanical behaviour of these samples has been investigated. The developed composite material is shown in Fig. 8.

Fig. 7
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Process to develop a hybrid composite material

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Table 6 Sample number and their compositions
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Fig. 8
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Developed composite samples (S1–S5)

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Materials Testing

A tensile test of the composite material was performed on the computerized universal testing machine. The parameters of a computerized universal testing machine for tensile testing of composite samples are mentioned in Table 7. Hardness testing of the composite samples was carried out on a Vickers hardness testing machine. A corrosion test of the samples was carried out in a salt spray chamber. Technical Specification of salt spray chamber for corrosion test is shown in Table 8. Thermal expansion of the composite material was performed in the muffle furnace. The technical specification of the muffle furnace is shown in Table 9.

Table 7 Computerized universal testing machine parameters [39]
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Table 8 Technical Specification of salt spray chamber for corrosion test
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Table 9 Technical specification of muffle furnace
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Results and Discussion

Microstructural Investigation

Figure 9 shows SEM images of an Al3105-based Metal Matrix Composite with various reinforcing weight percents of ES and RHA. The significant intermolecular force between the reinforcing particles and the base/matrix material is seen in this study (Al-3105). The robust connection between the reinforcement particles and the matrix material indicates that the tensile strength has improved. The presence of a strong intermolecular force or good bonding between the reinforcing agent particles and the matrix alloy is a clear sign of high wettability. Furthermore, the existence of voids and porosity, as well as the claustration of reinforcing particles, indicates that the created hybrid composite would lose ductility at increasing reinforcement weight percentages. In most cases, strengthening indicates that the reinforcement particles and the base metal are well-bonded. In order to achieve the desired (higher) mechanical properties, uniformly dispersed reinforcing particles in the matrix are essential [42]. The homogeneous distribution and dispersion of the reinforcing particles in the metal matrix are greatly improved by the stir casting process [43]. The microstructure analysis demonstrates that the reinforcement particles are dispersed evenly or uniformly inside the matrix, which is consistent with earlier findings [6, 9, 10]. Casting in an electromagnetic field has a significant impact on reinforcing particle distribution and dispersion [44]. The microstructure study indicates that the matrix has a uniform distribution of reinforcement. The findings are in line with those of other researchers [6, 9, 10]. There will be a decrease in ductility as the content (wt.%) of reinforcing particles increases beyond a particular point. The presence of brittle and hard ceramic particles identified in the reinforcement caused the maximum drop in ductility to be 65.7% at 20 wt.% of reinforcement (ESA and RHA reinforcing particles). These images indicate homogeneous dispersion of RHA and ESA particles with little or no cavities or defects, as well as interfacial resolution between metal matrix and reinforcements i.e., ESA and RHA particles.

Fig. 9
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SEM image of Al/5% ES/5% RHA

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Mechanical Behaviour of Composite

Figure 10a depicts the relationship between the tensile strength of synthesized composite materials and varied weight percentages of reinforcements i.e., ESA and RHA particles. The tensile strength of the material rose as there is a rise in wt.% of reinforcements. When force, is applied reinforcement particles create barriers to deformations. Basavarajappa et al. [47] reiterated similar observations for fly ash granules. The improved tensile strength of the composites can be linked to the fillers ESA and RHA, which has a stronger strength and offers better tolerance. When the weight percentage of reinforcements is greater than 7.5%, the tensile strength of the specimens decreased it could be owing to the reinforcement's low wettability with the metal matrix. Figure 11 shows the stress–strain diagram of different compositions. Maximum tensile strength was found to be 184.67 Mpa for composition Al/5% ESA/5% RHA composite with a percent elongation of 6.12%.

Fig. 10
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Mechanical properties of composite; a Tensile Strength, b Vickers Hardness of Composites, c Ductility, d Toughness

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Fig. 11
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Stress–strain diagram of different compositions

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Figure 10b depicts the relationship between wt.% of reinforcements and the hardness of produced MMCs. The hardness of the composite was found to rise gradually as the weight ratio of RHA and ESA particles increased. It emerges as the matrix's surface area expands, resulting in smaller grain size distribution. The existence of this hard surface area tends to increase the plastic deformation resistance, resulting in increased hardness. Ramachandra and Radhakrishna [48] reached the same conclusion with SiC particulates reinforcing agents.

Figure 10c depicts the influence of ESA and RHA reinforcement on composite percentage extension. The ductility of the composite was observed to reduce as the weight percentage of reinforcements increased. This is caused by the hardening of the reinforcement particles or the clumping of the particles. Sudarshan et al. and Surappa [49] observed identical results for different weight percents of fly ash reinforcements.

The effect of the addition of reinforcement particles i.e., ESA and RHA to the base material Al3105 has been discussed in Fig. 10d. The toughness of the final developed composite was reduced as there is an increase in the wt.% of reinforcements. On further addition of reinforcing agents, the toughness was increased to some extent due to good/uniform interfacial bonding development between the base material and reinforcements ES and RHA.

Corrosion and Thermal Behavior of Composite

A corrosion test of the composite was carried out in a salt spray chamber (Table 9). The weight of each sample before the corrosion test was kept uniform. Five different samples of the composite having different wt.% of the reinforcements and their corresponding loss in wt. was examined. It was observed that as the wt.% of the reinforcements gets increased the composite becomes more resistant to corrosion. Figure 12a indicates the variation of weight loss of different samples having different wt.% of the reinforcements. The dimension of each sample before the thermal expansion test was 2500 mm3. A thermal expansion test was carried out in a muffle furnace for 72 h at the temperature of 450 °C. Figure 12b indicates the change in volume due to the change in temperature, it was found that the addition of reinforcements enhances the thermal stability of the composite material. For the fifth sample where the reinforcements i.e., ESA and RHA were added in max wt.% the thermal expansion is minimum.

Fig. 12
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Behaviour of composite; a Corrosion weight loss, b Thermal expansion behaviour

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XRD Analysis of Composite Material

The main goal of the XRD analysis is to figure out how many distinct phases are there in the MMC. The XRD plots of the ball-milled AA3105/5% CESA/5% RHA composite material are shown in Fig. 13. For mechanically stirred casted samples, these XRD were plotted between relative intensity (y-axis) and 2-theta diffraction angle (degree) (MSCS). The fluctuation of relative intensity with 2 theta angle of diffraction for Al3105/5% ESA/5% RHA is depicted in an XRD plot. The peak points corresponding to the various elements contained in the composite are shown in Fig. 13. The XRD plot clearly shows that the greatest intensity peaks are Aluminum (base metal), followed by CaCO3, SiO2, and CaO.

Fig. 13
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XRD behaviour of Al + 5% ES + 5% RHA composite

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Conclusions

ESA and RHA can be utilized in the development of Aluminum-based composite materials. The correct wettability between the matrix material and reinforcement particles was observed in the microstructure of the AA3105/5% ES/5% RHA. An interfacial interaction reaction layer created between the matrix material and reinforcing material may result in adequate wettability. The highest value of tensile strength was found to be 184.67 MPa at 5 wt.% of ESA and 5 wt.% of RHA while highest hardness value was also found to be 58 HV for the third prepared sample i.e., having wt.% of each reinforcement 5%. As the wt.% of each of the reinforcements increases the toughness in J as well as ductility decreases and came out to be 10 J and 8.2% respectively this is due to the development of stronger interfacial bonding between the base metal Al3105 and reinforcements ES and RHA. However, the presence of hard phases in composites such as CaCO3, SiO2, and CaO respectively was responsible for enhancing the mechanical properties such as hardness and tensile strength of the composite. Good corrosion resistance is also evident from this study along with this the thermal stability of the developed composite increased to a significant extent.