Effect of perlite nanoclay reinforcements on the mechanical and tribological behaviour of AA7076 metal matrix nanocomposites

Amitkumar R Nadugeri, I G Siddhalingeshwar
School of Mechanical Engineering, KLE Technological University, Hubballi, India
amitr1998@gmail.com
igs@kletech.ac.in, https://orcid.org/0000-0002-2361-596X

N.R. Banapurmath, Ashok M Sajjan

Centre of Excellence in Material Science, School of Mechanical Engineering, KLE Technological University, Hubballi-580031, India
nr_banapurmath@kletech.ac.in,https://orcid.org/0000-0002-1280-6234
am_sajjan@kletech.ac.in, https://orcid.org/0000-0003-1251-8803
B H Maruthi Prashanth
Department of Mechanical Engineering, AGM Rural College of Engineering and Technology, Varur, Hubballi, Karnataka - 581 207, India
bhmprashant@gmail.com, https://orcid.org/0000-0003-3100-5288

Aluminium alloys, primarily composed of aluminium (Al) with alloying elements such as copper, manganese, magnesium, silicon, zinc, and tin, are widely used in engineering applications, where strength and lightweight properties are crucial. Around $85\mathrm{\%}$$85\mathrm{\%}$85%85 \%$85\mathrm{\%}$ of aluminium is utilised in forged products such as billets, rolled plates, and aluminium foil. While cast aluminium alloys are more affordable due to their lower melting points, they generally have lower tensile strengths compared to forged alloys. Among cast aluminium alloys, Al-Si alloys are particularly popular because of their high silicon content ( $4-13\mathrm{\%}$$4-13\mathrm{\%}$4-13%4-13 \%$4-13\mathrm{\%}$ ), which gives them excellent casting properties. Since the introduction of metal-skinned aircraft, aluminium alloys have been extensively employed in the aerospace industry due to their favourable strength-toweight ratio $[1-3]$$[1-3]$[1-3][1-3]$[1-3]$.
Aluminium matrix composites are increasingly used in automotive and aerospace industries due to their superior mechanical properties, lower density, improved corrosion and wear resistance, and lower thermal expansion coefficient. Recent
advancements have focused on enhancing these properties through the incorporation of nano-scale reinforcements such as silicon carbide ( SiC ), boron carbide ( ${\mathrm{B}}_4\mathrm{C}$${\mathrm{B}}_4\mathrm{C}$B_(4)C\mathrm{B}_{4} \mathrm{C}${\mathrm{B}}_4\mathrm{C}$ ), alumina ( ${\mathrm{Al}}_2{\mathrm{O}}_3$${\mathrm{Al}}_2{\mathrm{O}}_3$Al_(2)O_(3)\mathrm{Al}_{2} \mathrm{O}_{3}${\mathrm{Al}}_2{\mathrm{O}}_3$ ), graphene, and carbon nanotubes ( CNTs )
Patel et al. [4-6] conducted a series of studies fabricating AA5052 aluminum matrix composites reinforced with $5\mathrm{wt}\mathrm{\%}$$5\mathrm{wt}\mathrm{\%}$5wt%5 \mathrm{wt} \%$5\mathrm{wt}\mathrm{\%}$ of either SiC or B 4 C particles via stir casting. Their results demonstrate that ${\mathrm{B}}_4\mathrm{C}$${\mathrm{B}}_4\mathrm{C}$B_(4)C\mathrm{B}_{4} \mathrm{C}${\mathrm{B}}_4\mathrm{C}$ reinforcement significantly enhances microhardness (69.2%) and compressive strength (46.9%) while reducing density ( $0.68\mathrm{\%}$$0.68\mathrm{\%}$0.68%0.68 \%$0.68\mathrm{\%}$ ), making it ideal for lightweight applications. In contrast, SiC reinforcement improves abrasive wear resistance and hardness ( $39.7\mathrm{\%}$$39.7\mathrm{\%}$39.7%39.7 \%$39.7\mathrm{\%}$ ) but increases density ( $0.8\mathrm{\%}$$0.8\mathrm{\%}$0.8%0.8 \%$0.8\mathrm{\%}$ ). Both composites show uniform particle distribution and low porosity, confirming the effectiveness of the stir casting process for developing high-performance composites. Zhu et al. [7] reported enhanced mechanical properties in Al 6082 reinforced with nano-SiC due to uniform dispersion. Wang et al. [8] studied aluminium-based silicon carbide composites and their tribological features, finding that higher SiC content enhanced tensile strength at the cost of reduced ductility. Singh et al. [9] investigated the mechanical and tribological performance of hypereutectic aluminium-silicon alloy composites, reinforced with SiC , observing a $38\mathrm{\%}$$38\mathrm{\%}$38%38 \%$38\mathrm{\%}$ increase in tensile strength due to uniform dispersion of reinforcements along the grain boundaries. Patel et al. [10] developed AA5052/B ${}_4$${}_4$_(4){ }_{4}${}_4$ C metal matrix composites using stir casting, achieving 71% higher hardness and improved wear resistance compared to pure AA5052, making them suitable for lightweight and wear critical applications. AA7075 reinforced with ${\mathrm{TiB}}_2$${\mathrm{TiB}}_2$TiB_(2)\mathrm{TiB}_{2}${\mathrm{TiB}}_2$ and ${\mathrm{ZrO}}_2$${\mathrm{ZrO}}_2$ZrO_(2)\mathrm{ZrO}_{2}${\mathrm{ZrO}}_2$ showed an improvement in tensile strength ( $50\mathrm{\%}$$50\mathrm{\%}$50%50 \%$50\mathrm{\%}$ ), hardness ( $20\mathrm{\%}$$20\mathrm{\%}$20%20 \%$20\mathrm{\%}$ ), and a reduction in wear rate by $70\mathrm{\%}$$70\mathrm{\%}$70%70 \%$70\mathrm{\%}$ [11]. Ravikumar et al. [12] reported that reinforcement of AA7075 with hybrid micro and nano ${\mathrm{Al}}_2{\mathrm{O}}_3$${\mathrm{Al}}_2{\mathrm{O}}_3$Al_(2)O_(3)\mathrm{Al}_{2} \mathrm{O}_{3}${\mathrm{Al}}_2{\mathrm{O}}_3$ improved hardness ( $28\mathrm{\%}$$28\mathrm{\%}$28%28 \%$28\mathrm{\%}$ ), tensile strength ( $32\mathrm{\%}$$32\mathrm{\%}$32%32 \%$32\mathrm{\%}$ ), and up to $40-50\mathrm{\%}$$40-50\mathrm{\%}$40-50%40-50 \%$40-50\mathrm{\%}$ reduction in wear rate. Patil et al [13] reported an increase in wear resistance with the addition of MWCNTs ( $0.5\mathrm{wt}\mathrm{\%}-2\mathrm{wt}.\mathrm{\%}$$0.5\mathrm{wt}\mathrm{\%}-2\mathrm{wt}.\mathrm{\%}$0.5wt%-2wt.%0.5 \mathrm{wt} \%-2 \mathrm{wt} . \%$0.5\mathrm{wt}\mathrm{\%}-2\mathrm{wt}.\mathrm{\%}$ ) to AA7076. Raju et al. [14] reported that hybrid Mg-AZ91D composite reinforced with carbon fibers and MWCNTs showed up to $19\mathrm{\%}$$19\mathrm{\%}$19%19 \%$19\mathrm{\%}$ higher hardness, $35\mathrm{\%}$$35\mathrm{\%}$35%35 \%$35\mathrm{\%}$ higher tensile strength, and improved wear resistance, owing to uniform reinforcement dispersion and strong interfacial bonding. The wear rate reduction ranged between $4\mathrm{\%}$$4\mathrm{\%}$4%4 \%$4\mathrm{\%}$ to $35\mathrm{\%}$$35\mathrm{\%}$35%35 \%$35\mathrm{\%}$ at different loading conditions ( 10 N , 20N, and 30N). While AA7076 loaded with graphene amine and carbon fiber at $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ reinforcement achieved an increase in hardness, tensile strength by $50\mathrm{\%}$$50\mathrm{\%}$50%50 \%$50\mathrm{\%}$ and $42\mathrm{\%}$$42\mathrm{\%}$42%42 \%$42\mathrm{\%}$ respectively [15]. Studies by Jayaseelan et al. [16] and Nirala et al. [17] further highlighted the potential of graphene and CNT reinforcements in improving tensile strength and wear resistance.
Despite these advances, there remains a need for cost-effective and readily available reinforcements that can be easily integrated into aluminium matrices. Nanoclays, such as perlite nanoclay, offer a promising alternative due to their high aspect ratio, thermal stability, and potential for improving mechanical and tribological properties. While nanoclays have been extensively studied in polymer composites, their application in aluminium MMCs, particularly with AA7076 alloy, has been scarcely explored.
To date, systematic evaluation of perlite nanoclay as a reinforcement in AA7076 alloys has not been reported. This work, therefore, represents the first systematic investigation of perlite nanoclay-reinforced AA7076 composites, highlighting their mechanical and tribological performance and establishing their potential as a cost-effective and sustainable reinforcement material.

In this study, perlite nanoclay is employed as a reinforcement. Perlite is a naturally occurring amorphous volcanic aluminosilicate, chemically distinct from pearlite ( a steel microstructure), which, when heated to ${870}^{\circ }\mathrm{C}$${870}^{\circ }\mathrm{C}$870^(@)C870^{\circ} \mathrm{C}${870}^{\circ }\mathrm{C}$, expands into a lightweight, glassy cellular structure that imparts excellent insulation and low density [18]. The chemical composition is ${\mathrm{SiO}}_2(61.61\mathrm{\%}),{\mathrm{Al}}_2{\mathrm{O}}_3(8.84\mathrm{\%}),{\mathrm{Fe}}_2{\mathrm{O}}_3(16.92\mathrm{\%}),{\mathrm{TiO}}_2(1.8\mathrm{\%}),{\mathrm{K}}_2\mathrm{O}(4.11\mathrm{\%}),\mathrm{MgO}(6.02\mathrm{\%})$${\mathrm{SiO}}_2(61.61\mathrm{\%}),{\mathrm{Al}}_2{\mathrm{O}}_3(8.84\mathrm{\%}),{\mathrm{Fe}}_2{\mathrm{O}}_3(16.92\mathrm{\%}),{\mathrm{TiO}}_2(1.8\mathrm{\%}),{\mathrm{K}}_2\mathrm{O}(4.11\mathrm{\%}),\mathrm{MgO}(6.02\mathrm{\%})$SiO_(2)(61.61%),Al_(2)O_(3)(8.84%),Fe_(2)O_(3)(16.92%),TiO_(2)(1.8%),K_(2)O(4.11%),MgO(6.02%)\mathrm{SiO}_{2}(61.61 \%), \mathrm{Al}_{2} \mathrm{O}_{3}(8.84 \%), \mathrm{Fe}_{2} \mathrm{O}_{3}(16.92 \%), \mathrm{TiO}_{2}(1.8 \%), \mathrm{K}_{2} \mathrm{O}(4.11 \%), \mathrm{MgO}(6.02 \%)${\mathrm{SiO}}_2(61.61\mathrm{\%}),{\mathrm{Al}}_2{\mathrm{O}}_3(8.84\mathrm{\%}),{\mathrm{Fe}}_2{\mathrm{O}}_3(16.92\mathrm{\%}),{\mathrm{TiO}}_2(1.8\mathrm{\%}),{\mathrm{K}}_2\mathrm{O}(4.11\mathrm{\%}),\mathrm{MgO}(6.02\mathrm{\%})$, and $0.7\mathrm{\%}$$0.7\mathrm{\%}$0.7%0.7 \%$0.7\mathrm{\%}$ others [19]. Tab. 1 depicts the chemical composition of AA7076 alloy, while Tab. 2 provides the properties of perlite nanoclay. To develop nanocomposites, a base matrix containing perlite nanoclay particles at 1.0 and $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ was used. The AA7076perlite nanoclay nanocomposite was synthesised using the motorised stir casting technique, as shown in Fig. 1. The AA7076 aluminium was heated to ${650}^{\circ }\mathrm{C}$${650}^{\circ }\mathrm{C}$650^(@)C650^{\circ} \mathrm{C}${650}^{\circ }\mathrm{C}$, and both the aluminium and the perlite nanoclay were preheated in a preheater chamber at a constant temperature of ${400}^{\circ }\mathrm{C}$${400}^{\circ }\mathrm{C}$400^(@)C400^{\circ} \mathrm{C}${400}^{\circ }\mathrm{C}$. The reinforcements were added to the furnace once the preheating was completed. Degasification was performed to remove entrapped gases from the heated liquid melt [20-21]. A stirring speed of 400 rpm was maintained throughout the fabrication process to create vortices in the crucible, ensuring uniform dispersion of nanofillers. Finally, the liquid melt was poured into a preheated metallic mould. The Al 7076/perlite nanoclay nanocomposite test samples were prepared in accordance with ASTM standards to evaluate the mechanical and tribological properties.

The bulk hardness of samples was measured using a Vickers hardness tester as per ASTM E92. Before testing, the surfaces of the base alloy and composites were polished to ensure smoothness. A load of 50 N was applied using a steel ball indenter with a diameter of 5 mm .

The tensile strength of composite specimens was evaluated using a UTM ( 100 kN ). The test was conducted following the ASTM E-8 standard. Fig. 2 displays the dimensions of the tensile test specimen, which were designed following the ASTM E-8 standard.

The wear resistance of composites was evaluated using a pin-on-disk tribometer under room temperature, as per ASTM G99. Test specimens measuring 6 mm in diameter and 30 mm long were prepared from cast composite bars. The
experiments were carried out at different applied loads ( $10\mathrm{N},20\mathrm{N}$$10\mathrm{N},20\mathrm{N}$10N,20N10 \mathrm{~N}, 20 \mathrm{~N}$10\mathrm{N},20\mathrm{N}$, and 30 N ) with a constant sliding velocity of $1\mathrm{m}/\mathrm{s}$$1\mathrm{m}/\mathrm{s}$1m//s1 \mathrm{~m} / \mathrm{s}$1\mathrm{m}/\mathrm{s}$ and a sliding distance of 1200 m for each test.

The SEM micrographs and Energy-Dispersive X-ray (EDS) analysis of composite samples provide a clear and informative overview of the material's microstructure. The SEM micrographs in Fig.s 3 (a-d) confirm the presence of perlite nanoclay reinforcement particles within the MMCs. These micrographs illustrate the dispersion of particles within the matrix, providing crucial insights into the structural integrity of the composites. The micrographs demonstrate that the nanoparticles are uniformly distributed along the grain boundaries of the AA7076 matrix. This homogeneous distribution is attributed to the motorised stir-casting process, which effectively disperses the particles throughout the matrix, minimising agglomeration and porosity. This reduction in agglomeration and porosity indicates the effectiveness of the motorised stir-casting technique in achieving uniform dispersion.

Figs. 4 (a-d) illustrate the elemental distribution in the AA7076/perlite nanoclay composites obtained from EDX area mapping. Aluminium (Al) (Fig. 4a) appears uniformly across the scanned region, confirming the dominance of the base alloy matrix. Zinc (Zn) (Fig. 4b), the major alloying element in AA7076, also shows a uniform spread reflecting its even incorporation during casting. Carbon (C) (Fig. 4c) signals the presence of perlite nanoclay reinforcement, since perlite nanoclays contain water and carbon-rich traces from surface functionalization, which remain high after high-temperature processing. Iron (Fe) (Fig. 4d) appears as a localized bright spot, possibly originating from trace ${\mathrm{Fe}}_2{\mathrm{O}}_3$${\mathrm{Fe}}_2{\mathrm{O}}_3$Fe_(2)O_(3)\mathrm{Fe}_{2} \mathrm{O}_{3}${\mathrm{Fe}}_2{\mathrm{O}}_3$ content in perlite. The combined mapping confirms the integration of reinforcement particles into the aluminium matrix. Fig. 5 displays peaks corresponding to aluminium (Al) and carbon (C) in the AA7076/perlite nanoclay composites.

Fig. 6 illustrates the Vickers hardness of AA7076 composite reinforced with varying weight percentages of perlite nanoclay, providing valuable insights into the impact of these reinforcements on the material's properties. The Vickers hardness of the base material was found to be 82 HV . The addition of perlite nanoclay substantially enhanced the hardness of the AA7076 composite, indicating improved resistance to deformation. Composite loaded with $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ and $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ perlite nanoclay reinforcement exhibited an enhancement in hardness by $17\mathrm{\%}$$17\mathrm{\%}$17%17 \%$17\mathrm{\%}$ and $32\mathrm{\%}$$32\mathrm{\%}$32%32 \%$32\mathrm{\%}$ respectively, compared to the aluminium alloy. Increasing the concentration of reinforcement particles positively influences hardness, with the 1.5 $\mathrm{wt}.\mathrm{\%}$$\mathrm{wt}.\mathrm{\%}$wt.%\mathrm{wt} . \%$\mathrm{wt}.\mathrm{\%}$ composite exhibiting the highest hardness. The enhanced hardness is attributed to the homogeneous distribution of perlite nanoclay reinforcement around the grain boundaries of AA7076 alloy. Perlite nanoclay particles act as load-absorbing agents, contributing to the ability of the composite to withstand deformation under stress. Similar hardness improvements have been reported in other aluminium-based nanocomposites. Patel et al. [5] observed a $40\mathrm{\%}$$40\mathrm{\%}$40%40 \%$40\mathrm{\%}$ increase in hardness in AA5052/SiC composites, while Ravikumar et al. [12] reported a $28\mathrm{\%}$$28\mathrm{\%}$28%28 \%$28\mathrm{\%}$ increase in AA7075 reinforced with hybrid ${\mathrm{Al}}_2{\mathrm{O}}_3$${\mathrm{Al}}_2{\mathrm{O}}_3$Al_(2)O_(3)\mathrm{Al}_{2} \mathrm{O}_{3}${\mathrm{Al}}_2{\mathrm{O}}_3$ particles. Harichandran and Selvakumar [11] also demonstrated that the addition of ${\mathrm{B}}_4\mathrm{C}$${\mathrm{B}}_4\mathrm{C}$B_(4)C\mathrm{B}_{4} \mathrm{C}${\mathrm{B}}_4\mathrm{C}$ nanoparticles significantly improved hardness due to their role in restricting dislocation motion.

The stress-strain curves from the tensile tests of AA7076 and its perlite nanoclay-reinforced composites are shown in Fig. 7(a). The tensile strength, modulus, and percentage elongation derived from these curves are shown in Figs. 7(b), 7(c), and 7(d), respectively. The base AA7076 alloy exhibited a tensile strength of 106.15 MPa , a tensile modulus of 1.33 GPa , and a maximum strain of $12.2\mathrm{\%}$$12.2\mathrm{\%}$12.2%12.2 \%$12.2\mathrm{\%}$. With the addition of $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ nanoclay, the tensile strength increased to 126.27 MPa ( $\sim 19\mathrm{\%}$$\sim 19\mathrm{\%}$∼19%\sim 19 \%$\sim 19\mathrm{\%}$ improvement), accompanied by an increase in modulus to 1.77 GPa , while the maximum strain decreased slightly to $11.2\mathrm{\%}$$11.2\mathrm{\%}$11.2%11.2 \%$11.2\mathrm{\%}$. The $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ nanoclay composite demonstrated the highest tensile strength of 146.39 MPa ( $\sim 38\mathrm{\%}$$\sim 38\mathrm{\%}$∼38%\sim 38 \%$\sim 38\mathrm{\%}$ improvement) and the highest modulus of 2.21 GPa , though the maximum strain dropped further to $8.9\mathrm{\%}$$8.9\mathrm{\%}$8.9%8.9 \%$8.9\mathrm{\%}$.
These results highlight the beneficial effect of nanoclay on stiffness and load-bearing capacity, but also confirm the typical trade-off between strength and ductility. The improvement in mechanical properties can be attributed to multiple strengthening mechanisms, along with homogeneous dispersion. The nanoscale perlite particles act as a effective barrier to dislocation motion, contributing Orowan strengthening [22], where dislocations bow around the hard inclusions. Additionally, the strong interfacial bonding between the aluminium matrix and nanoclay facilitates efficient load transfer, enhancing tensile strength. The fine distribution of the nanoclay particles also leads to grain boundary pinning, which refines the grain structure and further strengthens the alloy.
Comparable strengthening effects have been reported in earlier studies. Singh et al. [9] observed a $38\mathrm{\%}$$38\mathrm{\%}$38%38 \%$38\mathrm{\%}$ increase in tensile strength in $\mathrm{Al}-\mathrm{Si}/\mathrm{SiC}$$\mathrm{Al}-\mathrm{Si}/\mathrm{SiC}$Al-Si//SiC\mathrm{Al}-\mathrm{Si} / \mathrm{SiC}$\mathrm{Al}-\mathrm{Si}/\mathrm{SiC}$ composites. The close agreement between these studies and the present work suggests that perlite nanoclay offers a highly efficient strengthening mechanism, achieving similar improvements to higher-loading ceramic reinforcements with the only $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ addition.
The SEM micrographs of the fractured tensile specimens (Figs. 8 (a-d) provide critical insights into the failure mechanisms of the composites. The SEM micrographs (Fig. 8(a-b)) of $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ loaded exhibit a smoother, flatter fracture surface with dimples, a combination of intergranular cracks, and shallower cleavage facets. These features reflect weaker bonding between matrix and filler particles, providing less for crack propagation. The fracture surface (Fig. 8(c-d)) of $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ demonstrates rougher morphology with dimples, river lines, and particle pull-out. These features indicate strong interfacial bonding between filler particles and the matrix, enabling effective load transfer and resistance to crack propagation. The improved bonding between the matrix and reinforcement particles acts as a barrier to dislocation, further contributing to the increased tensile strength.

The wear behaviour of AA7076/perlite nanoclay composites was assessed in terms of wear rate under different applied loads (10,20, and 30N), as shown in Fig. 9. The wear rate of the AA7076 alloy was observed to be 0.0028 ${\mathrm{mm}}^3/\mathrm{m},0.0034{\mathrm{mm}}^3/\mathrm{m}$${\mathrm{mm}}^3/\mathrm{m},0.0034{\mathrm{mm}}^3/\mathrm{m}$mm^(3)//m,0.0034mm^(3)//m\mathrm{mm}^{3} / \mathrm{m}, 0.0034 \mathrm{~mm}^{3} / \mathrm{m}${\mathrm{mm}}^3/\mathrm{m},0.0034{\mathrm{mm}}^3/\mathrm{m}$, and $0.0038{\mathrm{mm}}^3/\mathrm{m}$$0.0038{\mathrm{mm}}^3/\mathrm{m}$0.0038mm^(3)//m0.0038 \mathrm{~mm}^{3} / \mathrm{m}$0.0038{\mathrm{mm}}^3/\mathrm{m}$ at $10\mathrm{N},20\mathrm{N}$$10\mathrm{N},20\mathrm{N}$10N,20N10 \mathrm{~N}, 20 \mathrm{~N}$10\mathrm{N},20\mathrm{N}$, and 30 N , respectively, confirming that the wear severity increases with load due to higher contact stresses and intensified ploughing at the sliding interface. Incorporation of perlite nanoclay significantly reduced the wear rate across all loading conditions. At $1\mathrm{wt}\mathrm{\%}$$1\mathrm{wt}\mathrm{\%}$1wt%1 \mathrm{wt} \%$1\mathrm{wt}\mathrm{\%}$ reinforcement, the wear rate decreased to $0.0021{\mathrm{mm}}^3/\mathrm{m},0.0027{\mathrm{mm}}^3/\mathrm{m}$$0.0021{\mathrm{mm}}^3/\mathrm{m},0.0027{\mathrm{mm}}^3/\mathrm{m}$0.0021mm^(3)//m,0.0027mm^(3)//m0.0021 \mathrm{~mm}^{3} / \mathrm{m}, 0.0027 \mathrm{~mm}^{3} / \mathrm{m}$0.0021{\mathrm{mm}}^3/\mathrm{m},0.0027{\mathrm{mm}}^3/\mathrm{m}$, and $0.0033{\mathrm{mm}}^3/\mathrm{m}$$0.0033{\mathrm{mm}}^3/\mathrm{m}$0.0033mm^(3)//m0.0033 \mathrm{~mm}^{3} / \mathrm{m}$0.0033{\mathrm{mm}}^3/\mathrm{m}$ for $10\mathrm{N},20\mathrm{N}$$10\mathrm{N},20\mathrm{N}$10N,20N10 \mathrm{~N}, 20 \mathrm{~N}$10\mathrm{N},20\mathrm{N}$, and 30 N , respectively. The best performance was achieved with $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ nanoclay, where the wear rate further decreased to $0.0017{\mathrm{mm}}^3/\mathrm{m},0.0025{\mathrm{mm}}^3/\mathrm{m}$$0.0017{\mathrm{mm}}^3/\mathrm{m},0.0025{\mathrm{mm}}^3/\mathrm{m}$0.0017mm^(3)//m,0.0025mm^(3)//m0.0017 \mathrm{~mm}^{3} / \mathrm{m}, 0.0025 \mathrm{~mm}^{3} / \mathrm{m}$0.0017{\mathrm{mm}}^3/\mathrm{m},0.0025{\mathrm{mm}}^3/\mathrm{m}$, and 0.003 ${\mathrm{mm}}^3/\mathrm{m}$${\mathrm{mm}}^3/\mathrm{m}$mm^(3)//m\mathrm{mm}^{3} / \mathrm{m}${\mathrm{mm}}^3/\mathrm{m}$ under the same load conditions. These reductions clearly demonstrate that perlite nanoclay imparts enhanced wear resistance by increasing the hardness, improving load distribution, and providing a lubricating effect at the sliding interface. Similar decreases in wear rate with ceramic reinforcements have been reported for SiC [4] and ${\mathrm{B}}_4\mathrm{C}$${\mathrm{B}}_4\mathrm{C}$B_(4)C\mathrm{B}_{4} \mathrm{C}${\mathrm{B}}_4\mathrm{C}$ [5] based aluminium composites, validating that nanoclay serves as an effective reinforcement for improving the tribological performance of aluminum alloys.

SEM micrographs of worn surfaces of AA7076-perlite nanoclay composites are shown in Fig. 10 (a-d). The SEM micrographs reveal faint spots on the surface, indicating that material is being removed from the surface in a manner consistent with typical wear patterns. This suggests that the composite material effectively responds to the wear test conditions [16]. The micrographs of $1\mathrm{wt}\mathrm{\%}$$1\mathrm{wt}\mathrm{\%}$1wt%1 \mathrm{wt} \%$1\mathrm{wt}\mathrm{\%}$ composite (Fig. 10(a-b)) demonstrates deeper grooves, increased surface roughness, and more significant wear debris, indicating relatively higher material removal. However, the $1.5\mathrm{wt}\mathrm{\%}$$1.5\mathrm{wt}\mathrm{\%}$1.5wt%1.5 \mathrm{wt} \%$1.5\mathrm{wt}\mathrm{\%}$ composite images (Fig. 10 (c-d)) showed narrower grooves, smoother surfaces, and smaller, less significant wear debris, implying improved wear resistance. This resistance is attributed to the higher hardness of the composite material. Perlite nanoclay
particles impede dislocation movements, enhancing the composite's ability to withstand wear. The uniform dispersion of perlite nanoclay reinforcements in the composite matrix is crucial in enhancing wear resistance. This uniform distribution contributes to the composite's mechanical and tribological properties. The SEM micrographs further show that tracks on the surface are narrow and aligned parallel to the direction of wear. This alignment suggests the presence of a two-body abrasive wear mechanism. In this type of wear, material is removed from the surface due to direct contact and abrasion between the two surfaces in relative motion. Notably, worn debris materials cannot adhere to the surface, and their size is smaller. This is indicative of effective wear resistance, as smaller worn debris particles are less likely to cause additional damage or exacerbate wear.
The SEM micrographs shown in Fig. 11 (a-d) depict the wear debris of AA7076-perlite nanoclay composites, providing important insights into the morphology and composition of debris formed during wear tests. Micrographs of $1\mathrm{wt}\mathrm{\%}$$1\mathrm{wt}\mathrm{\%}$1wt%1 \mathrm{wt} \%$1\mathrm{wt}\mathrm{\%}$ composites Fig. 11 (a-b) show larger, sharper, and more irregular fragment structures, while $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ composite images Fig. 11 (c-d) depict smaller, flat, and fragmented platelike structures. This variation in morphology demonstrates that increasing filler content influences the debris characteristics, with $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ exhibiting a more noticeable abrasive wear mechanism. The elemental analysis provided in Fig. 12 reveals the presence of aluminium (Al) and zinc (Zn) as the primary alloying elements along with carbon ( C ), iron ( Fe ), and oxygen ( O ), indicating material transfer, oxidation, and interaction during sliding.

Afinite element (FE) simulation, carried out using ANSYS Workbench 2023 R1, predicts the mechanical properties of the developed metal nanocomposites, and the results are validated using experimental data.

In the Engineering Data section of ANSYS Workbench's Material Designer, a custom material was developed by incorporating the properties of AA7076 aluminium alloy and perlite nanoclay. This new material was configured to combine the characteristics of both components for simulation purposes. Representative volume element (RVE) [23-24], as shown in Fig. 13(a), was created for each nanocomposite with varying concentrations of nanofillers. The properties of the RVE were taken as input for structural analysis in ANSYS WB.

The CAD model for tensile testing, designed in compliance with ASTM E-8 standards, was developed using CATIA V5. The tensile model was discretised with Solid 92 elements, as illustrated in Fig. 13(b). For the simulation of tensile testing, one end of the specimen was fixed, while an axial load was applied to the opposite end, as depicted in Fig. 13(c). A Static structural analysis was performed on the meshed model to obtain the required results.
A mesh sensitivity (convergence) study was performed on a tensile specimen model to ensure that the FE results are independent of the mesh discretization. Three different element sizes were compared, starting with a coarse mesh of 1 mm , followed by a medium mesh of 0.5 mm , and finally a fine mesh of 0.25 mm , using Solid 92 elements. The predicted tensile strength for the $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ composite increased slightly from 154.93 MPa ( 1 mm mesh) to 156.64 MPa ( 0.5 mm mesh) and 157.74 MPa ( 0.25 mm mesh). As shown in Fig. 14, the convergence curve illustrates that the change in predicted tensile strength beyond 0.5 mm element size is negligible (less than 1%), confirming mesh independence. Therefore, the 0.5 mm
mesh was selected for subsequent simulations as it provided an optimal balance between computational efficiency and accuracy.

The tensile strength of the composite samples was determined through simulations conducted in ANSYS Workbench, and the results were compared with experimental data provided in Tab. 3. Fig. 15 illustrates the stress distribution in $1\mathrm{wt}\mathrm{\%}$$1\mathrm{wt}\mathrm{\%}$1wt%1 \mathrm{wt} \%$1\mathrm{wt}\mathrm{\%}$ nanocomposite specimen. The tensile strength values obtained for the $1\mathrm{wt}.\mathrm{\%}$$1\mathrm{wt}.\mathrm{\%}$1wt.%1 \mathrm{wt} . \%$1\mathrm{wt}.\mathrm{\%}$ specimen was 120.16 MPa from the simulation and 126.27 MPa from experimental testing. The variation between the simulated and experimental tensile strength values for all nanocomposites was found to be within a $10\mathrm{\%}$$10\mathrm{\%}$10%10 \%$10\mathrm{\%}$ margin.

Table 4: Comparative analysis of mechanical and tribological properties of AA7076/perlite nanoclay with other aluminium matrix.

Acritical observation from the comparison of the mechanical and tribological properties of aluminium matrix nanocomposites from the literature with the current work, as presented in Tab. 4, reveals a significant enhancement achieved with a remarkably low weight fraction ( $1-1.5\mathrm{wt}.\mathrm{\%}$$1-1.5\mathrm{wt}.\mathrm{\%}$1-1.5wt.%1-1.5 \mathrm{wt} . \%$1-1.5\mathrm{wt}.\mathrm{\%}$ ) of perlite nanoclay reinforcement. While many highperformance composites, such as those reinforced with $\mathrm{SiC},{\mathrm{B}}_4\mathrm{C}$$\mathrm{SiC},{\mathrm{B}}_4\mathrm{C}$SiC,B_(4)C\mathrm{SiC}, \mathrm{B}_{4} \mathrm{C}$\mathrm{SiC},{\mathrm{B}}_4\mathrm{C}$, or hybrid systems, require reinforcement loads of $5\mathrm{wt}.\mathrm{\%}$$5\mathrm{wt}.\mathrm{\%}$5wt.%5 \mathrm{wt} . \%$5\mathrm{wt}.\mathrm{\%}$ or higher to achieve substantial improvements $[5,9,10,16]$$[5,9,10,16]$[5,9,10,16][5,9,10,16]$[5,9,10,16]$, the present composite demonstrates comparable or higher effectiveness at a fraction of the reinforcement content.
For instance, the maximum improvement in tensile strength (38%) and hardness (38%) for AA7076/perlite nanoclay composite is comparable to the $38\mathrm{\%}$$38\mathrm{\%}$38%38 \%$38\mathrm{\%}$ increase in tensile strength reported by Singh et al. [9] using $10\mathrm{wt}.\mathrm{\%}\mathrm{SiC}$$10\mathrm{wt}.\mathrm{\%}\mathrm{SiC}$10wt.%SiC10 \mathrm{wt} . \% \mathrm{SiC}$10\mathrm{wt}.\mathrm{\%}\mathrm{SiC}$ and the $40\mathrm{\%}$$40\mathrm{\%}$40%40 \%$40\mathrm{\%}$
hardness improvement by Patel et al. [5] using SiC. Notably, the wear rate reduction (up to $39\mathrm{\%}$$39\mathrm{\%}$39%39 \%$39\mathrm{\%}$ ) is noticeable and outperforms AA7076 composites reinforced with MWCNTs or graphene amine-carbon fibre [13-14].
This demonstrates the exceptional reinforcing efficiency of perlite nanoclay. The ability to achieve property enhancements higher or similar to high-loading or hybrid composites using only $1.5\mathrm{wt}\mathrm{\%}$$1.5\mathrm{wt}\mathrm{\%}$1.5wt%1.5 \mathrm{wt} \%$1.5\mathrm{wt}\mathrm{\%}$ reinforcement is a significant advantage.

While this study demonstrates significant improvements in the mechanical and tribological properties of AA7076 composites reinforced with perlite nanoclay, this study has certain limitations. First, only two reinforcement levels (1.0 and $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ ) were investigated, which restricts the understanding of the full range of composition-property relationships. At higher filler contents, there remains a possibility of particle agglomeration and porosity formation, which could adversely affect performance. Second, the present work is limited to room temperature mechanical and wear testing. High-temperature stability, corrosion resistance, and long-term environmental durability were not evaluated but are critical for aerospace, automotive, and marine applications.

Building on the present findings, several directions can be pursued in future research. First, exploring higher weight percentages of perlite nanoclay will help to identify the optimum reinforcement level while assessing the risk of agglomeration. Incorporating hybrid reinforcements ( combining nanoclay with SiC, CNTs, or graphene) could further enhance mechanical, thermal, and tribological properties through synergetic effects. Second, industrial-scale prototyping and process optimization of stir casting will be essential to evaluate the scalability and economic feasibility of these composites for aerospace and automotive applications. Finally, comprehensive studies on corrosion resistance, high temperature performance, and environmental durability are needed to assess their suitability for real-world operating conditions.

This study developed and characterized AA7076-based metal matrix nanocomposites reinforced with perlite nanoclay through a motorized stir casting process. The results demonstrate that the $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ nanoclay composite was the optimal composition, exhibiting the highest improvements in hardness ( $32\mathrm{\%}$$32\mathrm{\%}$32%32 \%$32\mathrm{\%}$ ), tensile strength ( $38\mathrm{\%}$$38\mathrm{\%}$38%38 \%$38\mathrm{\%}$ ), and wear reduction ( $39\mathrm{\%}$$39\mathrm{\%}$39%39 \%$39\mathrm{\%}$ ) compared to the unreinforced alloy.
The observed enhancements are attributed to multiple strengthening and wear resistance mechanisms. Uniform dispersion of nanoclay particles across the AA7076 matrix facilitated effective load transfer and restricted dislocation motion. At higher reinforcement loading ( $1.5\mathrm{wt}.\mathrm{\%}$$1.5\mathrm{wt}.\mathrm{\%}$1.5wt.%1.5 \mathrm{wt} . \%$1.5\mathrm{wt}.\mathrm{\%}$ ), the nanoclay further contributed to grain boundary pinning, enabling effective load transfer and wear resistance by reducing ploughing and surface damage.
Numerical simulation studies using ANSYS Workbench further validated the experimental findings. The finite element models predicted tensile strengths within $5-8\mathrm{\%}$$5-8\mathrm{\%}$5-8%5-8 \%$5-8\mathrm{\%}$ variation of measured values, demonstrating strong agreement between computational and experimental approaches and confirming the reliability of the developed material model.
Overall, the combination of lightweight AA7076 alloy with perlite nanoclay reinforcement offers a cost-effective, sustainable, and high-performance material. These composites demonstrate strong lightweight potential with superior mechanical and wear properties, suitable for automotive, aerospace, and marine applications.

$\sigma$$\sigma$sigma\sigma$\sigma$ - tensile stress
$\epsilon$$\epsilon$epsi\varepsilon$\epsilon$ - strain
HV - hardness value
CoF -coefficient of friction

T he author extends heartfelt appreciation to all individuals and institutions whose invaluable support, guidance, and contributions were instrumental in the successful completion of this research.

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