Characteristics Study of Mechanical and Tribological Behaviour of Gr/Sn Dispersed Al-7Si Alloy Matrix Composite Processed Through Bottom Pouring Stir Casting Technique

The present study deals with the effect of the Gr, and Sn particulates in the mechanical and wear resistance of Al-7Si alloy based composites. The Al-7Si/Gr/Sn composites were prepared with the proportion of 10wt.% graphite and varying wt.% of tin (0, 2.5, 5, 7.5 and 10 wt.%) particles through the bottom pouring stir casting method. The added Sn metal powder up to 7.5 wt.% was diffused in the lattice of hypo eutectic Al-7Si alloy and formed a solid solution. The hybridization of Sn with graphite in Al-7Si alloy matrix brought significant enhancement in the tribological and mechanical properties of the composites. The tear ridges and dimples noted in the composites expressed the ductile mode of fracture in all the composites. The wear rate and the coefficient of friction of the composites were decreased with the addition of Sn metal powder in the composite. The Sn metal powder surfaced during the wear process and formed a thin mechanically mixed tribo-layer and reduced the friction. The thin mechanically mixed tribo-layer at the interface restricted the direct contact of asperities in the mating surface and reduced the wear loss. The adhesive wear was noted to be active in the composites with Sn metal powder.


Introduction
Aluminum-Silicon alloy is a widely used aluminum alloy in automotive, military and aircraft components due to their superior bulk and surface properties based on the silicon content [1,2]. The weldability, ductility, low-cost availability of the material made it suitable for several applications. The hypereutectic Al-Si alloy contained 17% of silicon is reported to possess exceptional resistance to wear and showed an increase in the transition load of mild to severe wear. The wear and mechanical properties of Al-Si alloy are tailored by introducing secondary particles such as graphite, Boron Carbide (B 4 C), Alumina (Al 2 O 3 ) [1,3,4], Zirconium Silicate (ZrSiO 4 ) [5] and Carbon nanotube (CNT) [6,7] in the matrix.
Among them, graphite reinforcement in aluminum and its alloys has significantly improved its ductility, tensile strength, elastic modulus, compressive strength, stiffness, thermal and electrical conductivity. Particularly in the automotive sector, the Al-Gr composites are used as brake components, pistons, gears, bearing surfaces and cylinder liners [8].
According to Jaswinder et al. [9], adding 6% graphite in Al/10%SiC composite would lower the friction coefficient and improve mechanical properties. Chou et al. [10] fabricated Al-Si/Al 2 O 3 composites by squeeze casting process and reported that the fracture toughness and bending strength were improved from 4.97 to 11.35 MPa m1/2 and 397 to 443 MPa respectively. Sajjadi et al. [1] used two stage melt process such as compo-casting followed by stir-casting to develop both micro and nano composites of Al-Si/Al 2 O 3 . The twostage method improved the microstructure with low porosity, grain refinement and uniform distribution of micro and nano reinforcements in the matrix. The improved microstructure of the composites resulted in superior yield strength, tensile strength, compression strength, and hardness. HajiZamani and Baharvandi [11] manufactured Al-Si-Al 2 O 3 -10% ZrO 2 composites using stir casting route at liquidous temperature 850 °C and the results expressed that alumina content increased the compressive strength, tensile strength, and yield strength. Bharath et al. [12] adopted two-stage stir casting process to produce the Al2014/Al 2 O 3 composites and studied the effect of varying weight percentage of Al 2 O 3 on microstructure and wear behavior and reported the improved resistance of composite to the wear. Chandla et al. [13] developed hybrid aluminum composite with 5 wt.% Al 2 O 3 and varying wt.% of bagasse ash and reported the superior mechanical properties such as micro-hardness, impact strength, ductility, and tensile strength.
The research works on hybridization of aluminum matrix composites for tailoring the surface properties have been carried out by several researchers and they found distinctive results. The organic and inorganic solid lubricants such as graphite, graphene, hBN, zinc stearate was used as a secondary reinforcement to form hybrid composites. These solid lubricants as a constituent of the composite, reduced the wear loss and coefficient of friction at the interface of the mating parts. The constituents of these solid lubricants form a transfer layer at the interface which restricts the direct contact of mating surface and results in better tribological characteristics. Reddy et al. [14] used ultrasonically assisted casting technique to study the tribological behavior of aluminum alloy reinforced with 2 wt.% of SiC and varying wt.% of Gr. The uniform dispersion of SiC and Gr nano-reinforcements in the composites resulted in reduced wear rate and coefficient of friction. Singhal & Pandey [15] developed hybrid aluminum metal matrix composite via stir casting technique and studied the effect of Gr/Sn as a reinforcement. The composite containing Gr/Sn as a solid lubricant, showed the maximum reduction in wear rate and coefficient of friction. However, there was no significant attempt in Al-Si/Al 2 O 3 based composites to enhance the resistance to friction and wear by incorporating Sn as a hybridizing reinforcement. Ravindran et al. [16] used a powder metallurgy technique to fabricate Al2024/ 0 to 20%SiCp/5%.Gr hybrid composites. The addition of Gr and SiC nano particles reinforced with the Al2024 alloy significantly increased the hardness and wear resistance of the fabricated hybrid composites. The minimum wear loss and maximum hardness are observed in al alloy based composite reinforced with 20% SiC and 5% graphite particles. Liu et al. [17] studied the wear behavior of Al2014 alloy reinforced with 5% graphite composite. The minimum friction coefficient and wear loss are observed in the graphite reinforced Al2014 composite compared to that of the base matrix. Aruri et al. [18] used a friction stir casting route to fabricate Al6061/SiC composites reinforced with Al 2 O 3 and Gr particles. Improved wear resistance is observed due to the additions of the selected ceramic reinforcement particles such as silicon carbide, alumina and graphite. It is observed from the Al6061/SiC/Gr hybrid composites that silicon carbide particles withstand the external applied load and graphite particles act as a solid lubricant. Kaushik et al. [19] manufactured Al 6082-SiC and Al6082-SiC-Gr hybrid composites by stir casting route and studied the abrasive wear phenomena. Minimum wear rate is observed in Al6082-SiC-Gr hybrid composites compared to base alloy and Al 6082-SiC composites. Suresha and Sridhara [20] fabricated LM25/SiC/Gr hybrid composites through stir casting route. The author used central composite based RSM technique to optimize the input factors such as sliding distance, % reinforcement, applied Load, and sliding speed. The author concluded that minimum wear rate is observed in LM25 alloy reinforced with 3.5% of SiC and 3.5% of graphite for any value of sliding speed, applied load and sliding distance within the selected range in the experimentation. In their study of the graphene-reinforced al 7050 alloy by squeeze casting technique, Venkatesan et al. [21] adopted Taguchi's methodology (L27 orthogonal array) with variables such as load, sliding distance and velocity. Analysis of variance (ANOVA) was carried out to determine the significant parameters that affect the wear rate of the composite prepared. According to the results of the ANOVA, load has a greater impact on wear rate than sliding velocity and distance. Additionally, the microstructure demonstrates that as the load increases, a changeover from mild to severe wear in the composite pin specimen is observed.
Tofigh et al. [22] fabricated A356/nano-Al 2 O 3 composites using compocast processing technique. The highest ultimate tensile strength value is achieved with the addition of 1.8% nano-Al 2 O 3 particles into the A356 alloy matrix. These mechanical properties improvement in fabricated composite samples is achieved due to the primary a-Al phase refinement and uniform distribution of eutectic Si particles. Shabani and Heydari [23] Al-Si-Mg alloys have the properties such as good wear resistance, good castability, good weldability, and low thermal expansion which is the reason for highest consumption rate in industrial sector. The author investigated the influence of temperature and time of heat treatment on spheroidization of silicon particles in fabricated composite casting samples and concluded that higher solutionising time and lower temperature is very suitable for gaining fine and scattered distribution of the silicon particles in the composites. Shabani et al. [24] used conventional and compo casting processes to fabricate Al-Si alloy/nano-Al 2 O 3 composites. Microstructural characterization study reveals that sand casted composite sample exhibits dendritic structure and compo cast composite sample exhibits non-dendritic microstructure. Shabani et al. [25] used three techniques such as conventional gravity sand casting, compocasting, squeeze casting to fabricate the A356/nano-Al 2 O 3 composites. The tensile fractured specimen machined from the composites undergone a microstructural study which reveals that the presence of dimples became even smaller, more spherical and distributed uniformly in the matrix due to refined and more spherical α dendrites and silicones in composites that fabricated via of compo casting in comparison with sand casting and squeeze casting samples. In comparison to squeeze and compo casting, samples fabricated via sand castings exhibits coarser dendritic fracture and sever agglomeration of reinforcing particles. Shabania and Heydari [26] investigated the effect of various casting techniques on the wear properties of Al-SiC composites. The test results reveal that minimum porosity, maximum hardness and wear resistance of the composite samples is observed when using higher applied current rate. In addition increment in sliding distance results in increased weight loss of the samples hence lower sliding speed is preferred.
Shabani et al. [27] investigated the effect of various casting techniques, reinforcing particles sizes and heat treatment on the mechanical properties of A356/nano-Al 2 O 3 composite. The authors concluded that the higher mechanical properties were found in specimens fabricated by semisolid compo casting in comparison with sand casting and squeeze casting samples. Shabani et al. [28] concluded that the higher tensile strength value is achieved in compo casting sample in semi-solid state due to uniform distribution of reinforcing particles when compared to sand casting and squeeze casting technique. In addition, the tensile strength of the heat-treated specimens has improved by about 30%.
Investigation of mechanical and wear behavior of Al-Si alloy reinforced with graphite and tin is an interesting area of research. Because the content of Si determines the tribological characteristics of the Al-Si alloy. However, the friction between the mating surfaces needs to be reduced to enhance the tribological behaviour of the material. The introduction of selflubricating secondary particle and alloying elements in the base alloy is expected to form transfer film which will reduce the friction between mating surfaces under wear process. The self lubricating capacity of Al-Si alloy can be enhanced by introducing the Sn, a solid lubricant, as an inherent alloying element along with graphite secondary particle in the composite. This research work is an attempt to enhance the friction and wear properties of hypo eutectic Al-Si alloy / 10 wt.% Gr composites by adding Sn metal powder in the material. The addition of Sn is expected to dissolve and be a part of solid solution of alloy, whereas the graphite remains the secondary particle. Therefore, this study emphasizes the mechanical and wear properties of hypo eutectic Al-Si alloy-based composites by adding graphite and tin as reinforcement. The main objective of the present research work is to include the Sn in the solid solution of Al-Si alloy-based composites and to bring the Sn to the interface during the wear process. The result of this attempt is anticipated to resist the friction and wear along with the enhancement of mechanical properties in Al-Si/Gr composite.

Materials and Methods
The Al-7Si alloy was procured from a local supplier in Coimbatore, Tamil Nadu. The chemical composition of Al-7Si alloy is displayed in Table 1. The reinforcement particles of graphite (Gr) and tin (Sn) were supplied by Merck with the average size of ≤ 50 µm and ≤ 45 µm respectively with > 99% purity. The morphology of Gr and Sn particles are displayed in Fig. 1(a) and (b) respectively. Figure 1 (a) shows hexagonal shaped Gr particles and Fig. 1 (b) displays smooth spherical shaped Sn particles. Table 2 shows the composition details of the composites. The stir casting route was used to manufacture the composites. The Al-7Si alloy rods of 250 g were heated and melted initially in the furnace. The molten Al-7Si alloy's temperature was kept constant at 700 °C. Before adding the reinforcements, the molten metal was agitated for 5 min with a graphite stirrer at 500 rpm. The reinforcement particles were heated to 130 °C before being added to the molten metal. The reinforcements were put in place in two stages. Initially, the Sn metal powder was added to the melt and stirred for 5 min at 500 rpm. The liquid temperature was then raised to 850 °C and held there for 6 h to allow the complete dissolution of Sn in Al. Later, the Gr particles were introduced into the melt while wrapped in thin aluminum foil to ensure uniform distribution throughout the matrix. After stirring, the composite mixture was poured into a cylindrical mild steel die. The experimental setup and fabricated composite sample are displayed in Figs. 2 and 3. The optical micrographs study of prepared Al-7Si/Sn/Gr composites is carried out. For the optical micrographs study, samples were prepared and ground with different grades of abrasive papers and then polished with a velvet cloth using 1 M aluminate solution. These polished specimens were then etched in an acetic picric solution to make the grain boundaries visible. Figure 4 depicts the EDS results of the composites W5 with uniform distribution. The presence of the elements Al, Si, Mg, Fe, Sn, and O in the composites was confirmed by Fig. 4.
Ultimate tensile and compression tests were performed on a Universal testing (UTM) machine according to ASTM E8/E8M and ASTM E9 standards, respectively. The Brinell hardness test was carried out according to the ASTM E10 standard. The polished composite samples were hardened with the help of Brinell hardness testing machine with a load of 50 kg and a ∅ 2.5 mm ball indenter. The dry sliding wear test was performed in room temperature using a pin on disc-DUCOM tribometer and an EN-31 hardened disc according to the ASTM G99 standard. The tribological performance of the composites was evaluated using varying normal loads of 10N, 20N, 30N, and 40N while maintaining a sliding distance of 1000 m and a velocity of 1 m/s.

Microstructure and XRD Analysis
The optical microstructure of the alloy and composites prepared are shown in Fig. 5 (a-f). All the images were captured in the same magnification. The bright spot represents α-Al phase of Al-Si alloy. The black spot indicates the presence of graphite in the grain boundary. The Sn added up to 7.5% occupied the vacancies in the crystal lattice of base alloy. The mechanical properties were increased by the addition of Sn in the alloy. This may be predicted due to the improvement in precipitation hardening of the Al-Si alloy [29]. The addition of Sn more than that, segregated in the grain boundary as shown in Fig. 5 (e) and (f). These segregations were noted as intermetallic compound Mg 2 Sn formed due to the excessive addition of Sn in the matrix. Figure 6 displays the XRD patterns of the Al-7Si/10%Gr/7.5% Sn composite and conforms the presence of α-Al, Si Gr, and Sn peaks in the composite.

Hardness Evaluation
The microhardness values of the synthesized composite samples were evaluated in five distinct regions, with the average results shown in Table 3. The Fig. 7 illustrates that the micro-hardness values improved with the amount of Sn particulates, reaching 7.5 wt.%. The value decreased with the addition of Sn particulates (10 wt.%). The Al-7Si alloy had a hardness of 71 BHN, which was lower than that of its composites. When graphite particles were introduced to the Al-7Si alloy, the microhardness improved from 71 to 75 BHN. In terms of microhardness, the composite Al-7Si/7.5%Sn/10% Gr outperformed the Al-7Si alloy and the other composites. The uniform dispersion of the graphite particles could be attributed to the increased micro-hardness. Furthermore, the superior bonding between the reinforcement and the matrix, the presence of hard particles, and the absence of porosities contribute to the microhardness [30]. On the other hand, the reduction in microhardness can be described by two factors: the presence of particle agglomeration in the composites and the presence of micropores in the composites. Inside the eutectic Si region, the β-Sn phase is formed. Another factor in the hardness reduction is the soft β-Sn phase [31].

Tensile and Compressive Properties
The fractured samples of the tensile test are shown in Fig. 8. Figure 9 and Table 3 summarize the tensile properties of the Al-7Si/Sn/10Gr composite samples, such as ultimate tensile strength (UTS) and percentage of elongation. Compared to Al-7Si alloy and Al-7Si/10Gr composite, Sn particles improved both the average yield and tensile strengths of composites marginally. The UTS and percentage of elongation of pure Al-7Si alloy increased by ~ 11.4% and ~ 8%, respectively, with a 10% Gr addition. Furthermore, the addition of 2.5 wt.% Sn with 10 wt.% Gr increased the UTS of Al-7Si alloy by ~ 25.8%. It can be denoted that the addition of Sn particles caused a gradual increase in UTS of up to 7.5 wt.%.
On the other hand, the addition of 2.5 wt.% Sn with Al-7Si/10Gr increased the elongation percentage significantly by ~ 87.6%, and the elongation percentage gradually improved with the addition of Sn particles up to 7.5 wt.%. It is seen that the tensile properties of the composites started to decline with the 10 wt.% Sn additions. The failure mechanism of tensile fracture of the tested composite samples was investigated using microstructural analysis. SEM micrographs of the fractured specimen Al-7Si/7.5Sn/10Gr are displayed in Fig. 10 (a) and (b). In the SEM image of the fractured sample, tear ridges and dimples can be seen. Tear ridges can be noted at the grain boundaries, which can be attributed to the resistance provided by the reinforcing particles that were uniformly distributed along the grain boundaries against tensile loading. The Al-7Si fracture develops into a transgranular fracture mainly at the contact between the eutectic Si and the eutectic Al in the eutectic region [32].
Adding Sn particles to Al-7Si/10Gr composites improved the ultimate compressive strengths, as indicated in Table 3, according to the compressive testing findings of the Al-7Si/Sn/10Gr composites. The compressive strength improved with the addition of Sn particles to the composite as shown in Fig. 9. The compressive strength of Al-7Si alloy was 175.5 MPa and adding 10 wt.% Gr enhanced the compressive strength by ~ 9.8%. The inclusion of Sn particles in the Al-7Si/10Gr composite improved the Al-7Si alloy's compressive strength by ~ 10.6%. The Al-7Si/10Sn/10Gr composite has better compressive properties than the alloy, with a compressive strength of 228.9 MPa, which is 30.4% higher. Figure 11 displays the wear specimens used for the experimentation. The variation in CoF and weight loss for alloys and composites sliding at constant speeds and distances are shown in Fig. 12 (a) as functions of the applied load. The average CoF and weight loss both enhances with increasing load, as can be observed. The alloy with 10% Gr particles added has a lower CoF and weight loss under all applied loads than the Al-7Si base alloy. The decreased CoF and wear loss might be attributed to Gr's lubricating properties [33]. Additionally, it is noticeable that adding Sn particles to the Al-7Si/10Gr composite can enhance wear resistance in Fig. 12 (b). In comparison to Al-7Si alloy and its composites, the Al-7Si/10Sn/10Gr composite provided higher wear resistance under all wearing loads studied. The Mg2Sn intermetallic phase is formed by the addition of Sn, which interacts with Mg more readily than Si [34]. The improved wear resistance of the alloy and its composites might be attributed to the formation of the hard Mg2Sn phase. SEM images with lower to a higher magnification of worn surfaces of the Al-7Si/10Gr composite after 1000 m of sliding at 40 N load, and 1 m/s sliding velocity are shown in Fig. 13 (a-d). The composites showed considerable adhesive wear under these circumstances. In Fig. 13(a), the grooves and scratches found on the composites' worn surface go parallel to the direction of sliding. The interaction of the composite surface with the harder counter disc led to the development of parallel scratches. The higher magnification SEM images, as displayed in Fig. 13 (c) and (d) illustrate the delamination wear along with the abrasive grooves on the worn surface of the   Fig. 7 Effect of addition of graphite and tin reinforcement on hardness of the composites Al-7Si/10Gr composite. Delamination wear, ploughing grooves, and cracks were observed on the worn surface of an Al-7Si/10Gr composite pin (Fig. 13(c) and (d)), indicating mixed wear mechanisms that may be the cause of the increased wear rate. The nucleation of cracks on the worn surface perpendicular to the sliding direction might lead to delamination wear. Figure 14 (a-d) display the worn surface images of the Al-7Si/7.5Sn/10Gr composite pin at various magnifications. The shallow abrasive grooves and traces of plastic deformation caused by the ploughing action are shown in Fig. 14 (a). And the traces of ploughing action and cracks were observed in the higher magnification SEM image (Fig. 14 (c)) of the Al-7Si/7.5Sn/10Gr composite.

Experimental Analysis Using RSM Design of Experiment
Based on the test results, sample W5 has high tensile strength and hardness value which is selected as best composite specimen among others. Hence, tribological characterization study were conducted on the W5 specimen with Taguchi based optimization methodology (L9 Orthogonal array), to select the best optimum input factors (applied Load, sliding distance and velocity) by considering the output responses such as wear rate and CoF. The process and response factors values are displayed in Table 4. The ANOVA table (95% confidence interval) for the response wear rate is shown in Table 5. It is observed from the Table 5, that the applied Load have the highest sum of square value and also have a major influence on the wear rate followed by sliding distance and velocity. The significant input parameters are selected based on the P-Value   is 0 to 0.05). Based on the P-Value mentioned in the Analysis of Variance table, Load and sliding distance are selected as most significant factor, affecting the selected response called wear rate, and as the sliding velocity having P-Value greater 0.05 is consider as a nonsignificant parameter in predicting the wear rate. For the selected response (wear rate), the R 2 value is 0.9706 which is in good agreement with the adjusted R 2 value (0.9529). The "Predicted R 2 " of 0.8808 and "Adj R-Squared" of 0.9529 are in reasonable agreement with each other. Hence, this model within the selected parameter ranges can able to predict the wear rate.
The ANOVA table (95% confidence interval) for the response coefficient of friction is shown in Table 6. It is observed from the Table 6, that the applied Load have the highest sum of square value and also have a major influence on the CoF followed by sliding distance and velocity. The significant input parameters are selected based on the P-Value (Significant range is 0 to 0.05). Based on the P-Value mentioned in the Analysis of Variance table, Load and sliding distance are selected as most significant factor, affecting the selected response (CoF), and as the sliding velocity having P-Value greater 0.05 is consider as a non-significant parameter in predicting the CoF. For the selected response (CoF), the R 2 value is 0.9837 which is in good agreement with the adjusted R 2 value (0.9739). The "Predicted R 2 " of 0.9316 and "Adj R-Squared" of 0.9739 are in reasonable agreement with each other. Hence, this model within the selected parameter ranges can able to predict the CoF.
The quadratic equation for wear rate and COF is mentioned in Eqs. 1 and 2 respectively. Wear rate and COF residual plot are displayed in Fig. 16  (a) and (b) respectively. Figure describes that all the residues run between -3 to 3 levels that there was no expected pattern perceived.
(1) The influence of selected process parameters on wear rate of Al-7Si/Gr/Sn composites has been studied from dry sliding wear test and the same is displayed in Fig. 17 Fig. 17(a). In comparison to 20 N and 10 N applied loads, the wear rate for Al-7Si/Gr/Sn composites is greater at 30 N; this may be attributed to adhesive wear on the pin material brought on by temperature increases between contacting surfaces at higher loads [35]. The protective layer may be developed at greater loads (30 N) and sliding distances (2000 m) by removing graphite and Sn particles from the composite. This oxide layer, known as the mechanically mixed layer, forms over the sliding surfaces and lowers the wear rate for higher sliding velocities. The formation of a protective layer causes the wear rate to increase as the sliding velocity rises from 1 m/s to 3 m/s [36].
Dry sliding wear test was used to study the impact of applied load, sliding distance, and velocity on coefficient of friction of Al-7Si/Gr/Sn composites and the results are presented in Fig. 18. As the load and velocity increase, the coefficient of friction also rises, as depicted in Fig. 18(a). The coefficient of friction was found to be lowered at 1 m/s velocity and 10 N applied load. This is because the third layer formation between surfaces at lower velocities due to the abrasive nature of material removal. When the load was increased from 10 to 30 N, the CoF also improved by 30%. This phenomenon occurs because the transfer layer produced by graphite (a solid lubricant) is stable under lower loads but wipes out under larger loads as a result of temperature rise. Inaddition, Variation of COF was noted to be in the marginal range of 0.36 to 0.38. This is predicted due to the increase in normal load, the active secondary particle graphite and the Sn particles in the alloy were pulled out due to the abrasion of the material. The worn-out particles formed a tribo-layer in between the mating surfaces, which reduced the friction considerably in the tribo-system. A significant variation in the COF can be found from Fig. 18 (b), which is in the range of 0.2 to 0.41. This graph represents the COF value with respect to the increase in sliding distance and sliding speed. This is attributed to the mechanism that the tribo-layer formed was wiped out when the sliding speed was increased.
The best optimized combination of values for output responses such as wear rate and COF are 0.00555486 g/Km and 0.3648595 which could be obtained when testing with 10 N applied load, 1000 m sliding distance and 1.002 m/s sliding speed, and the same is displayed in Fig. 19. The optimized process parameters have desirability value 96.9% in predicting the selected responses. The histogram of the desirability of the best solution is displayed in Fig. 20.

Conclusion
Al-7Si/Gr composites are fabricated by adding Sn metal powder in different weight percentage. The Sn in Al-7Si alloy dissolved and became part of the solid solution. The mechanical and tribological performance of the developed material was studied and the following conclusions were arrived.
1. The tensile properties of composites were increased up to the addition of 7.5 wt.% of Sn. Ductile mode of fail-ure was noted in all the composites with tear ridges and dimples. Matrix strengthening due to the addition of Sn and Strengthening due to secondary particle Gr were identified as major strengthening mechanisms.  18 Effect of input parameters on COF the increased micro-hardness. Furthermore, the superior bonding between the reinforcement and the matrix, the presence of hard particles, and the absence of porosities contribute to the microhardness. 3. The Al-7Si/10Sn/10Gr composite has better compressive properties than the alloy, with a compressive strength of 228.9 MPa, which is 30.4% higher. 4. In comparison to Al-7Si alloy and its composites, the Al-7Si/10Sn/10Gr composite provided higher wear resistance under all wearing loads studied. The Mg2Sn intermetallic phase is formed by the addition of Sn, which interacts with Mg more readily than Si. The improved wear resistance of the alloy and its composites might be attributed to the formation of the hard Mg2Sn phase. 5. The COF of the composites were decreased with the addition of Sn metal powder in the material system. The Sn metal powder surfaced during the wear process and formed a thin mechanically mixed tribo layer and reduced the friction. 6. Based on the design of experiments selected, output responses such as wear rate and COF has the best optimized combination of values are 0.00555486 g/Km and 0.3648595 which could be obtained when formed with 10 N load, 1000 m sliding distance and 1.002 m/s sliding speed