Characterization of wear rate of Al-12 wt%Si alloy based MMC reinforced with ZrO2 particulates

The primary objective of this study is to fabricate an Al-12 wt% Si Alloy/ZrO2 composite using the Stir Casting technique, with a specific focus on assessing its performance, particularly in terms of wear characteristics. This research presents a unique approach by utilizing Al-12 wt% Si Alloy as the matrix material, aiming to develop tailored Al Alloy matrix composites suitable for applications requiring enhanced tribological properties. The composites are systematically manufactured with varying percentages of micro-sized ZrO2 reinforcements, specifically 0.5, 1, and 3 wt%. The incorporation of ZrO2 results in significant improvements in wear resistance, a critical attribute for Al-12 wt% Si Alloy-based composites. These composites find extensive utility across industries such as marine, aerospace, automotive, and the power sector, where they are indispensable for producing vital components like electrical sliding contacts, gears, bearings, bushes, pistons, piston rings, and clutches. Despite the availability of various promising reinforcement materials, researchers persistently explore novel combinations of matrices and reinforcements to tailor properties and enhance cost-effectiveness. ZrO2 has emerged as a notable reinforcement material in metal matrix composites, as evidenced by numerous research endeavours. The composites fabricated with ceramic reinforcement’s exhibit enhanced tribological characteristics. The study observes that the wear rate decreases up to 3 wt% of reinforcements, beyond which it increases due to reinforcement agglomeration. The optimal wear-resistant combination is found at 3 wt% of ZrO2, attributed to robust micro-coring and interstitial metal-oxygen bonding facilitated by the Si content in the Al-12%Si matrix. The results are further optimized using Response Surface Methodology (RSM) techniques and validated using the ANOVA table to elucidate the behaviour of the composites under different operational conditions. The hardness results further ascertain the decrease in the wear rate due to the inclusion of ZrO2 reinforcements owing to micro coring and strengthening.


Introduction
A composite material is a heterogeneous solid formed by bonding two or more distinct materials through mechanical or metallurgical means.These composites retain the unique properties of their individual components, encompassing characteristics such as stiffness, strength, weight, high-temperature resilience, corrosion resistance, hardness, and conductivity [1][2][3].These attributes are often unattainable within the individual constituent materials.For example, consider the conventional composite of bricks, where clay and cement serve as matrix components, while grass and sand act as reinforcement [4][5][6].Typically, one component functions as the matrix, creating the continuous phase in which the reinforcing material is distributed [7][8][9].

Materials
Aluminium possesses advantageous attributes, such as its ease of casting, machining, and shaping, along with low density, non-toxicity, high thermal conductivity, and corrosion resistance, securing its position as the sixthmost ductile and second-most malleable metal.Sourced from Hindalco in Bangalore, Karnataka, India, ingots consisting of 99.8% pure aluminium were obtained, while silicon, characterized by its brittleness and hardness, was acquired from Manas Metallurgical in the same region to introduce a secondary phase.
The 'Al-12%Si' used as matrix in the present work typically refers to an aluminium alloy containing 12% silicon (Si) by weight.This type of alloy is commonly used in various industrial applications due to its desirable properties.The addition of silicon to aluminium can enhance the alloy's strength, wear resistance, and castability.Al-12%Si alloys are often utilized in the production of cast components, particularly in the automotive industry for engine components and other applications where a combination of lightweight and good mechanical properties is essential.The specific characteristics of Al-12%Si alloy may vary based on the exact composition and processing conditions, and it is important to consult detailed specifications for precise information on its properties and applications.
In terms of mechanical properties measured in the metric system, the material exhibits a Brinell hardness of 85, Knoop Hardness of 109, Rockwell B Hardness of 53, and Vickers Hardness of 96.The Ultimate Tensile Strength is reported as 331 MPa, with a Yield Tensile Strength of 165 MPa.The Elongation at Break is specified as 2.5%, and the material demonstrates a Fatigue Strength of 140 MPa.Machinability is noted at 50%, and the Shear Strength is determined to be 199 MPa.Moving to electrical properties, the material showcases an Electrical Resistivity of 0.00000750 ohm-cm.In terms of thermal properties, the Heat of Fusion is reported as 389 J g −1 .The Coefficient of Thermal Expansion (CTE) linearly increases, with values of 20.8 μm m −1 °C (20.0 °C-100 °C) and 22.1 μm m −1 °C (20.0 °C-300 °C).Specific Heat Capacity is indicated as 0.963 J g −1 °C, and the Thermal Conductivity is measured at 92.0 W/m-K.The material exhibits a Melting Point range of 516 °C-582 °C, with a Solidus temperature at 516 °C and a Liquidus temperature at 582 °C.

Fabrication methodology
The fabrication methodology employed for producing Al-12 wt% Si Alloy/ZrO 2 composites through stir casting encompasses several crucial steps aimed at creating advanced materials.It relies on the well-established stir casting technique to integrate reinforcements into an Al-12 wt% Si Alloy matrix.The process begins with the careful selection of high-quality commercial Al-12 wt% Si Alloy as the matrix material.Pre-heat-treated ZrO 2 in powdered form serves as the reinforcement, intended to provide additional strength.The preparation of these reinforcements is pivotal, involving pre-treating ZrO 2 to enhance its compatibility with the Al-12 wt% Si Alloy matrix, potentially through processes like heat treatment or surface modification.Additionally, pre-treating ZrO 2 ensures strong adhesion to the matrix.Subsequently, the Al-12 wt% Si Alloy material undergoes a melting process in a furnace, with its melting point typically around 674 °C.Once the Al-12 wt% Si Alloy is in a molten state, the pre-treated ZrO 2 reinforcements are carefully introduced into the Al-12 wt% Si Alloy within a crucible.To ensure a uniform distribution of the reinforcements throughout the matrix, a mechanical stirrer is employed, operating at a speed ranging from 350 rpm to 500 rpm, usually spanning a duration of 7 min to 10 min.The resulting mixture is then cast into a mould, taking on the desired shape.During the cooling and solidification process, the rate of cooling significantly influences the final properties of the composite.It is worth noting that, for further enhancement of the composite's characteristics, degassing of the molten metal is accomplished before pouring into the die set using coverall flux, to avoid entrapment of gases and impurities in the casting.Comprehensive testing and characterization follow the composite production process, assessing various mechanical properties, electrical conductivity, and other pertinent attributes.Based on the results obtained from these tests, adjustments to the composite's composition or processing conditions can be considered to optimize its properties.Subsequently, the Al-12 wt% Si Alloy/ZrO 2 composites can be employed in a range of applications tailored to their specific properties.It is important to acknowledge that specific parameters and conditions may vary based on particular research or industrial requirements.Additionally, the process includes essential steps such as heating ZrO 2 to 300 °C-350 °C for 15 min to remove moisture content, melting Al-12 wt% Si Alloy at a temperature exceeding 674 °C, degassing the molten metal at 650 °C, and pouring the melt with reinforced particles into preheated moulds, maintaining a pouring temperature of 645 °C.Castings are retrieved once the solidification of the molten metal is achieved.

Wear characterization
The specimen preparation process adhered to established ASTM standards for testing, involving the utilization of a computerized pin-on-disc wear testing machine, following ASTM standards G99-95.Test specimens (figure 1) with a diameter of 6 mm and a length of 25 mm were fabricated through machining of the cast specimens.These machined wear test specimens, prepared in accordance with ASTM Standard G99-95, are displayed.The wear test procedure outlined a laboratory approach for assessing material wear during sliding, employing a pin-on-disk apparatus, and it facilitated testing materials in pairs under nonabrasive conditions while allowing for the determination of the coefficient of friction.The wear characteristics were evaluated using a pin-on-disc wear system, with a schematic representation of the apparatus provided.The system encompassed essential components, including a motor, a revolution counter, pin specimen holder and lever arm, and wear measurement instruments.The sensitivity and precision of these instruments were essential for accurate wear measurement, particularly in low wear scenarios.

Test parameters
The test parameters are as follows: load, at the wearing contact; rotational speed; track diameter; and atmospheric conditions surrounding the wearing contact.The procedure for conducting the wear test involves initial cleaning and drying of the specimens, ensuring the removal of any foreign substances, and particularly, the elimination of cleaning fluids from materials with open grains [39].The dimensions of the specimens are measured, and they are securely placed in their respective holders.The motor is started, and speed adjustments are made while keeping the pin specimen away from the disk.The desired number of revolutions is set, and the test begins with the specimens in contact under load, with no interruptions or restarts allowed.Upon completion, the specimens are examined for features near the wear, and post-test measurements are conducted as needed.The formulae used for the calculation of wear rate are as follows.

Brinell hardness characterization
The Brinell hardness test stands as a prevalent method for determining the hardness of materials.This test involves applying a known force to a hardened steel ball of specified dimensions and pressing it against the surface of the material under examination for a defined duration.The resulting indentation's diameter is then measured, and the Brinell hardness number (HB) is computed using a formula that considers the applied force and the indentation's surface area.This test is particularly suitable for materials with coarse microstructures or rough surfaces, such as castings and forgings, as it offers a robust measure of hardness without causing damage.It finds wide application across manufacturing, metallurgy, and materials science for evaluating the hardness of metals and alloys, providing valuable insights into material properties and performance.The hardness is characterized using the formula in equation

Results and discussion
3.1.Wear test results for different loads, track diameter and wt% of ZrO 2 at 200 RPM The results section offers insights into wear rate data concerning various combinations of ZrO 2 reinforcement % at different applied loads and RPM settings.Wear rate, a crucial metric measured in milligrams per meter (mg/m), serves as a fundamental parameter for evaluating a material's wear resistance in specific conditions.Summarizing the findings, it becomes evident that the wear rate is notably influenced by several factors [40].First, an initial increment in the wt% of ZrO 2 from 0.5 wt% to 1 wt% correlates with a decrease in wear rate, signifying that a higher ZrO 2 wear resistance by strengthening the material.Second, the wear rate diminishes with a rise in ZrO 2 content, demonstrating that ZrO 2 acts as an effective reinforcement, bolstering the material's resistance to wear [41].Even a small addition of ZrO 2 (0.5%) results in a discernible reduction in wear rate, and higher ZrO 2 percentages (up to 3%) contribute to further wear rate reduction.Third, an increase in applied load is associated with an elevated wear rate, as greater pressure leads to more pronounced wear.Lastly, higher RPM settings result in increased wear rates due to more frequent contact and sliding between materials.In conclusion, these findings emphasize the interplay between Al-Si and ZrO 2 content, applied load, and RPM in influencing a composite material's wear resistance.Augmenting the ZrO 2 content enhances wear resistance, while greater loads and RPM levels correspond to higher wear rates, providing valuable insights for the development of materials with superior wear properties.The table 2 gives the wear rate for different loads, track diameter and wt% of ZrO 2 for different loads at 200 RPM.
The provided table offers insights into wear rates, measured in milligrams per meter (mg/m), within a matrix of variables including ZrO 2 percentages, and applied loads at a constant RPM of 200.The trends in the data reveal the following patterns: First, an increase in ZrO 2 reinforcements from 0.5 wt% to 3 wt% consistently leads to reduced wear rates, signifying that higher ZrO 2 content enhances wear resistance by strengthening the material [42].Second, higher ZrO 2 percentages exhibit a significant reduction in wear rates, emphasizing ZrO 2 's effectiveness in augmenting wear resistance, with a more pronounced effect at greater ZrO 2 percentages [43].Lastly, elevated applied loads are directly associated with increased wear rates, underlining the impact of pressure on material wear [44].In summary, these findings offer valuable guidance for tailoring material compositions to specific wear-resistant applications, empowering engineers and material scientists to optimize materials for varying conditions.

The data analysis reveals pivotal trends
ZrO 2 Percentage: The dataset underscores that amplified ZrO 2 wt% coincide with diminished wear rates.Even a minor 0.5% ZrO 2 addition results in an evident reduction in wear rates in comparison to scenarios without ZrO 2 .The efficacy of ZrO 2 reinforcement becomes increasingly pronounced with higher ZrO 2 proportions.For instance, at 10 N load, wear rates drop from 0.03019 mg/m for 0.5 wt% ZrO2 reinforcements to 0.025895 mg m −1 with 3% ZrO 2 , signifying the robust impact of ZrO 2 .Further, the lubricating property of ZrO 2 can significantly influence friction and wear rates, potentially reducing them by forming a lubricious layer between contacting surfaces.This effect can mitigate abrasive wear and surface damage, leading to improved wear resistance in composites containing ZrO 2 reinforcements.Therefore, acknowledging the lubricating effect of ZrO 2 enhances the comprehensiveness of wear behaviour analysis and provides insights into the mechanisms underlying the performance of composite materials in tribological applications.
Applied Load: Wear rates consistently surge with augmented applied loads.At 1 wt% ZrO 2 , wear rates ascend from 0.01453 mg m −1 at a 10 N load to 0.019096 mg m −1 at a 20 N load.This underscores the direct correlation between applied loads and wear rates, where heightened loads intensify material pressure, leading to elevated wear and wear rates.The figures 2 and 3, gives the surface plot and 3D contour plot of wear rate for different wt% of ZrO 2 , loads and track diameter.The figure 4 gives the comparison for the predicted values in reference to the actual values.The error is less than +/− 5% and is within the permissible limit.
The table 3 presents the ANOVA model for wear rate in milligrams per meter at 200 RPM.The significant Model F-value of 67.86 suggests the model's overall significance.The probability of obtaining an F-value of this magnitude due to random variation is only 0.01%.Model terms with p-values less than 0.0500, such as A, B, C, B 2 , and C 2 , are considered statistically significant.Conversely, model terms with p-values greater than 0.1000 are deemed not significant.If numerous model terms are found to be insignificant (excluding those necessary for maintaining hierarchy), reducing the model may enhance its effectiveness.Table 4 provides the fit statistics for wear rate measured in milligrams per meter at 200 RPM.The Predicted R 2 , standing at 0.9374, aligns reasonably well with the Adjusted R 2 , which is recorded at 0.9586.The marginal  difference, less than 0.2, suggests a consistent fit.The Adeq Precision, indicating the signal-to-noise ratio, is notably high at 27.145, exceeding the desirable ratio of 4. This signifies a robust signal in the model, affirming its suitability for navigating the design space.
The results of the present work are compared with the relevant findings of other authors to ascertain the wear mechanism that has impacted the behaviour of the composites.A

The interpretation of these values reveals key trends:
ZrO 2 Percentage: The data illustrates a clear relationship between ZrO 2 percentages and wear rates.As the ZrO 2 wt% increases, wear rates tend to decrease.Even a minor addition of 0.5% ZrO 2 results in a significant reduction in wear rates compared to situations without ZrO 2 .The effect is most pronounced with 3% ZrO 2 , and a 10 N load where the wear rate decreases to 0.008385 mg/m.This underscores the effectiveness of ZrO 2 as a reinforcement in reducing wear rates.Applied Load: The table also highlights the impact of applied loads on wear rates.As the load increases, wear rates tend to rise.For example, at 1% ZrO 2 , the wear rates increase from 0.003085 mg m −1 at a 10 N load to 0.009552 mg m −1 at a 30 N load.This demonstrates the direct correlation between applied loads and wear rates, with higher loads resulting in increased wear rates.
In summary, this dataset reveals the complex interplay of ZrO 2 and applied load on wear rates measured in mg/m.Higher ZrO 2 percentages contribute to improved wear resistance, resulting in lower wear rates, while increasing applied loads lead to higher wear rates.These findings offer valuable insights for optimizing material compositions to meet specific wear-resistant criteria.The figure 5 gives the surface plot of the Wear rate for different wt% of Reinforcements and load at 400 RPM for 0.5 wt% ZrO 2 , 1 wt% ZrO 2 , and 3 wt% ZrO 2 , while the figure 6 gives the 3D contour plot.
The figure 7 gives the predicted versus actual wear rate for different track diameter and load at 400 RPM, and it is evident that the predicted wear rate is in close correlation with the actual wear rate.
Table 6 displays the ANOVA model for wear rate measured in milligrams per meter at 400 RPM.The Model F-value, standing at 44.12, signifies the model's significance, with only a 0.01% likelihood of such a large F-value occurring due to random noise.Model terms are considered significant when their p-values are less than 0.0500, and in this instance, A, B, C, A 2 , B 2 , and C 2 are identified as such.Conversely, model terms with p-values exceeding 0.1000 are regarded as not significant.Should there be numerous insignificant model terms (excluding those essential for maintaining hierarchy), reducing the model might enhance its overall effectiveness.
Table 7 presents fit statistics for wear rate at 400 RPM, conveying key metrics for model evaluation.The standard deviation (Std.Dev.) of 0.0014 signifies the spread or variability of wear rate data around the mean, with lower values indicating reduced variability.The mean, denoted as 0.0071, represents the central point around which individual wear rate measurements vary.The Coefficient of Variation (C.V.%) at 19.42%   expresses the standard deviation relative to the mean, offering insight into the data's relative variability.A higher C.V. suggests increased variability.The coefficient of determination (R   reinforcement percentages, and applied loads, all while maintaining a constant RPM of 600.The analysis of these values reveals significant trends: ZrO 2 Percentage: The data reveals that higher ZrO 2 percentages correspond to lower wear rates.Even a modest 0.5% ZrO 2 addition leads to a noticeable reduction in wear rates compared to scenarios without ZrO 2 , and this effect becomes more pronounced with higher ZrO 2 percentages.For instance, at 10 N load, the wear rates decrease from 0.008183 mg/m for 0.5 wt% ZrO 2 to 0.007221 mg m −1 with 3% ZrO 2 , demonstrating the robust influence of ZrO 2 as a reinforcement.
Applied Load: The table also emphasizes the role of applied loads in wear rates.As the load increases, wear rates tend to rise consistently.For example, with the increase in the reinforcement's viz., 1% ZrO 2 , the wear rates increase from 0.005839 mg m −1 at a 10 N load to 0.006886 mg m −1 at a 30 N load.This underscores the direct relationship between applied loads and wear rates, where higher loads exert more pressure on the material, resulting in increased wear and wear rates.
This dataset predicts the intricate interactions among ZrO 2 percentage, and applied load concerning wear rates measured in mg/m.Higher ZrO 2 percentages lead to improved wear resistance and lower wear rates, while increased applied loads correspond to higher wear rates.These insights provide valuable guidance for optimizing material compositions to meet specific wear-resistant criteria.The figure 8 gives the surface plot of wear rate for different wt% of reinforcements and load at 600 RPM for 0.5 wt% ZrO 2 , 1 wt% ZrO 2 , and 3 wt% ZrO 2 respectively, while the figure 9 gives the 3D contour plot.The figure 10 gives the predicted versus actual wear rate for different wt% of reinforcements, track diameter and load at 600 RPM.It is herewith evident that the predicted and actual wear rate are in close agreement with each other.
The table 9 gives the ANOVA for wear rate in mg/m at 600 RPM.The Model F-value of 35.49implies the model is significant.There is only a 0.01% chance that an F-value this large could occur due to noise.P-values less than 0.0500 indicate model terms are significant.In this case A, B, C, AB, B 2 , C 2 are significant model terms.Values greater than 0.1000 indicate the model terms are not significant.If there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model.The table 10 gives the fit statistics for wear rate in mg/m at 600 RPM.
The Predicted R 2 of 0.8856 is in reasonable agreement with the Adjusted R 2 of 0.9227; i.e. the difference is less than 0.2.Adeq Precision measures the signal to noise ratio.A ratio greater than 4 is desirable.The ratio of 20.039 indicates an adequate signal.This model can be used to navigate the design space.The optimization for wear rate are accomplished with the R 2 value close to 95%.
The comparisons drawn between the wear mechanisms in this study and those investigated by Rahman Bajmalu Rostami et al form the basis for exploring how ZrO 2 affects the microstructure and wear properties of Al 2 O 3 /Al-Si composites.The authors' research delves into the interaction between ZrO 2 addition and resulting microstructural alterations in these composites, as well as their impact on wear properties.Their findings provide valuable insights into the potential improvement in wear resistance due to ZrO 2 reinforcement, illuminating the intricate connection between microstructure and material performance, a relationship also confirmed in the current study [46].

Hardness
The table 11, presents data related to the designation of specimens and their respective weight percentages of ZrO 2 , along with the Brinell Hardness (HB) Number observed across multiple trials on the surface of the composite specimens.The specimens are designated as 'As Cast,' 'A0.5Z,' 'A1Z,' and 'A3Z,' representing different weight percentages of ZrO 2 (0%, 0.5%, 1%, and 3%, respectively).For each specimen designation, three trials were conducted to measure the BHN.In the 'As Cast' specimen, which contains 0% ZrO 2 , the HB number ranged from 59.4 to 61.2 across the three trials, with an average HB number of 60.03.As the weight  percentage of ZrO 2 increased to 0.5% in the 'A0.5Z' specimen, the HB number also increased, ranging from 61.9 to 63.1 across trials, with an average HB number of 62.50.Similarly, for the 'A1Z' and 'A3Z' specimens containing 1% and 3% ZrO 2 , respectively, the HB number increased further, with average values of 74.97 and 74.27, respectively.The standard deviation and variance values provide insights into the dispersion of data points around the mean HB number for each specimen designation, indicating the level of consistency or variability in the hardness measurements across trials.Overall, the table highlights the influence of ZrO 2 content on the hardness properties of the Al-Si composites, with higher ZrO 2 concentrations generally corresponding to higher HB number values.K Senthil Kumar et al have accomplished works on the hardness characteristics of the Al-SiC composites.The objective of their study is to investigate the wear characteristics of aluminium-based composites reinforced with silicon carbide and granite powder.The metal matrix composite will be fabricated using the bottom pour stir casting process, followed by analyzing the wear performance of the prepared hybrid metal matrix composites.Wear analysis will be conducted using a pin-on-disc apparatus under various loads to assess the wear resistance of the material.Additionally, Rockwell hardness tests will be performed and the hybrid composite material will be optimized.The results indicate that aluminium without reinforcement exhibits low hardness compared to reinforced specimens.The findings suggest that increased percentages of SiC lead to faster solidification, enhancing mechanical properties and refining grain size.Moreover, the hardness of the specimens increases with the dispersion of particles in the matrix, particularly evident when reinforced with SiC.For instance, the addition of 3% SiC results in a 7.2% increase in aluminium hardness compared to pure aluminium, while the most significant change occurs with 7% SiC reinforcement, showing a 70.2% increase in hardness.The presence of hard reinforcement particles like SiC enhances the load-bearing capacity of the specimen and restricts matrix deformation by limiting dislocation movement.
The table 12 gives the Brinell hardness (HB) number for different wt% of reinforcements measured across the cross section of the composite.From the provided tables, it's evident that both sets of specimens (designated as As Cast, A0.5Z, A1Z, and A3Z) have been subjected to trials measuring Brinell Hardness (HB) number with varying weight percentages of ZrO 2 .
Comparing the two tables, it's observed that in general, the addition of ZrO 2 tends to increase the average HB number across all specimens.For instance, in the 'As Cast' specimens, where no ZrO 2 is added, the average HB number is higher in the second set of specimens (59.00) compared to the first set (60.03).Similarly, across all weight percentages of ZrO 2 , the average HB number tends to be higher in the second set of specimens.
In terms of variability, the standard deviation and variance values provide insights into the consistency or variability in hardness measurements across trials.In both sets of specimens, as the weight percentage of ZrO 2 increases, the standard deviation and variance values tend to fluctuate.However, the extent of variability seems to differ between the two sets of specimens.
Regarding the comparison of hardness values on the surface and across the surface of the composite specimens, it's important to note that the HB number values presented in the tables reflect measurements taken on the surface of the specimens.While these measurements provide valuable insights into the surface hardness of the composites, they may not fully represent the hardness characteristics across the entire volume of the specimens.
In summary, the comprehensive comparison of the two tables suggests that the addition of ZrO 2 generally leads to an increase in the average surface hardness of the composite specimens.However, the extent of this increase and the variability in hardness measurements may vary depending on factors such as the weight percentage of ZrO 2 and the specific characteristics of the composite materials used.The findings of the present work are compared with the research outcomes of Jaafari et al their study focuses on investigating the microstructure and mechanical properties of 6261 Aluminum matrix reinforced with Zirconium dioxide (ZrO 2 ) particles, produced using the stir casting process.Casting is conducted with varying weight percentages of ZrO 2 as the reinforcement phase.Specimens are machined according to ASTM standards for composites to facilitate different testing.The analysis using SEM morphology reveals a uniform distribution of hardened particles throughout the metal matrix, without any clustering, resulted in enhanced strength and hardness owing to micro coring and segregation [47].

SEM of wear track
Scanning Electron Microscopy (SEM) is a valuable imaging technique widely employed for investigating material surfaces at the micro-or nanoscale.In this context, SEM is utilized to capture images of wear tracks generated by a specific material composition.The SEM images reveal distinctive surface morphological characteristics, showcasing the formation of deep grooves, plough marks, continuous valleys, wide groove formations, and wear patterns.The material composition of the specimens considered for morphological analysis of the wear track contains 0.5% ZrO 2 and 3% ZrO 2 by weight, effectively evaluating its suitability for applications requiring wear resistance.The SE micrographs of the A0.5Z and A3Z are represented in figures 11(a) and (b) respectively.The SE micrographs captured using the VEGA 3 TESCAN machine at 25 k V scanning voltage.Microstructure in figure 11(a) for A0.5Z exhibits a slightly refined grain structure, and there might be initial indications of ZrO 2 particles dispersed throughout the matrix, contributing to slight increase in hardness.
The figure 11(b) gives the SE micrograph of the A3Z specimen.At this concentration, the microstructure may exhibit a saturation point with ZrO 2 particles, contributing to the hardness and embrittlement of the composite.
Further to the SE micrograph of the composite samples, the imaging process of the wear track is conducted to provide meaningful insights into the microstructure and wear performance.In particular, the description encompasses SEM images of wear tracks, elucidating the surface features of composite materials with varying ZrO 2 concentrations (0.5%, 3%), with imaging conducted using the Zeiss make Multi SEM 506 machine.
These SEM images serve as essential tools for comprehending the intricate microstructures and wear behaviours of the composite materials.The SEM images of figure 12(a) depicts the wear track of the composite reinforced with 0.5 wt% ZrO 2 , the formation of deep groves and deep plough marks are evident in the SEM, while the grooves and plough marks tend to reduce in the width with narrow valleys owing to the resistance of indentation by the sliding disk on the pin as in figure 12(b).Further, the plough marks, and micro scratch lines tend to become thinner with the further increase of reinforcements upto 3 wt%.The scratch lines are very fine and narrow owing to greater strengthening formed between the Al-Si and ZrO 2 ceramic reinforcements as in figure 12(b).Also, the wear patches are eliminated owing to micro-coring and greater strengthening between the atoms due to the metal-oxygen bonds.The presence of ZrO 2 particles at higher concentrations contributes to enhanced hardness and wear resistance, limiting the extent of surface deformation.This microstructural modification is consistent with the observed reduction in wear, highlighting the beneficial effects of incorporating ZrO 2 up to 3 wt% in enhancing the wear performance of the composite material.
The EDS analysis further ascertain the presence of ZrO 2 in the matrix, thereby validating the inclusion of the ceramic reinforcements of ZrO 2 leading to enhanced hardness and offering thick lubrication films that eventually led to reduction in the wear of the composites.The wear enhancement of composites reinforced with Zirconium dioxide (ZrO 2 ) is attributed to the strengthening mechanisms, primarily involving dispersion strengthening and grain refinement effects [48][49][50][51].ZrO 2 particles, when uniformly dispersed in the matrix material like aluminium, obstruct dislocation movement during deformation, thereby increasing the composite's strength and hardness [52].This hindrance to dislocation motion reduces wear rates by impeding the movement of contacting surfaces during wear.Additionally, the addition of ZrO 2 particles leads to grain refinement within the composite structure, resulting in smaller grain sizes and increased grain boundary density [53].These fine grains effectively block dislocation movement and prevent crack propagation during wear processes, contributing to improved wear resistance.Moreover, ZrO 2 particles may form a protective layer on the composite surface, reducing direct contact between wearing surfaces and acting as a lubricant to minimize friction and wear.In summary, the incorporation of Zirconium dioxide particles enhances wear resistance through a combination of dispersion strengthening, grain refinement, and the formation of protective surface layers [54][55][56].

Conclusions
1.The critical analysis of the wear results reveals a substantial decrease in wear rates as the percentage of ZrO 2 reinforcement increases.For instance, at 200 RPM, the wear rate decreases from 0.03019 mg m −1 with 0.5% ZrO 2 to 0.00591 mg m −1 with 3% ZrO 2 .Similarly, at 400 RPM, wear rates decrease from 0.011522 mg m −1 to 0.0007307 mg m −1 with the same increase in ZrO 2 content.
2. The statistical validation using Response Surface Methodology (RSM) techniques provides robust support for the observed trends in wear rate variations across different ZrO 2 percentages and RPM settings.The RSM analysis confirms the significance of ZrO 2 content and RPM as influential factors affecting wear rates in the composite materials.This statistical validation enhances the reliability and credibility of the experimental findings, reinforcing the understanding of wear behaviour in ZrO 2 -reinforced composites and facilitating their optimization for various industrial.3. Hardness values obtained from the brinell tests demonstrate an increase in hardness with higher percentages of ZrO 2 reinforcement.For example, a 7.2% increase in hardness is observed when 3% ZrO 2 is added compared to the base aluminum alloy.
4. The SEM images of the wear track reveal the formation of deep grooves, plough marks, and continuous valleys, indicating significant material removal during wear testing.The presence of ZrO 2 reinforcement in the composites results in the formation of ridges within the wear track, which act as barriers to further abrasive penetration.This observation underscores the role of ZrO 2 in enhancing the wear resistance of the composites by effectively modifying the surface morphology and mitigating wear-induced damage.
5. The EDS analysis corroborates the uniform distribution of ZrO 2 particles within the metal matrix, preventing cluster formation and enhancing overall strength.
6.The strengthening mechanism responsible for wear enhancement in the composites can be attributed to the interstitial strengthening effect brought about by the incorporation of ZrO 2 .This reinforcement effectively limits matrix deformation by restricting the movement of dislocations, thereby improving wear resistance.
In conclusions, the experimental findings and RSM validations underscore the significant role of ZrO 2 reinforcement in enhancing wear resistance in aluminum composites.The observed decrease in wear rates, coupled with the SEM and EDS analyses confirming improved microstructural characteristics and uniform distribution of reinforcement, highlights the potential of ZrO 2 -based composites for wear-resistant applications.Additionally, the increase in hardness values and the identified strengthening mechanism further support the effectiveness of ZrO 2 as a reinforcement material in metal matrix composites.

Figure 2 .
Figure 2. Surface plot of Wear rate in mg/m for different track diameter and load at 200 RPM.

Figure 3 .
Figure 3. 3D contour plot of Wear rate in mg/m for different track diameter and load at 200 RPM.
Daoud et al have accomplished the research on the study of wear and friction characteristics in near eutectic Al-Si composites reinforced with ZrO 2 particles is a significant area of interest in materials engineering.Near eutectic Al-Si alloys are commonly utilized due to their

Figure 4 .
Figure 4. Predicted versus Actual Wear rate in mg/m for different track diameter and load at 200 RPM.

Figure 5 .
Figure 5. Surface plot of Wear rate in mg/m for different track diameter and load at 400 RPM.

Figure 6 .
Figure 6.3D contour plot of Wear rate in mg/m for different track diameter and load at 400 RPM.

Figure 7 .
Figure 7. Predicted versus Actual Wear rate in mg/m for different track diameter and load at 400 RPM.

Figure 8 .
Figure 8. Surface plot of Wear rate in mg/m for different track diameter and load at 600 RPM.

Figure 9 .
Figure 9. 3D contour plot of Wear rate in mg/m for different track diameter and load at 600 RPM.

Figure 10 .
Figure 10.Predicted versus Actual Wear rate in mg/m for different track diameter and load at 600 RPM.
The experimentations for wear tests are accomplished for 4 different set of test parameters viz., the diameter, load, rotational speed in rpm, and the wt% of ZrO 2 .The parameters employed in the wear test are represented in table1.

Table 1 .
Test parameters applied in the wear test.

Table 2 .
Wear rate mg/m for different loads, track diameter and wt% of ZrO 2 at 200 RPM.

Table 3 .
ANOVA for wear rate in mg/m at 200 RPM.

Table 4 .
[45]statistics for wear rate in mg/m at 200 RPM.lightweight and corrosion resistance; however, they often lack adequate hardness and wear resistance for demanding applications.Incorporating ZrO 2 particles into the Al-Si matrix alters the composite's microstructure and mechanical properties, with ZrO 2 known for its hardness and thermal stability, enhances the hardness and reduces the wear of the composites.Investigation into wear and friction behaviours involves experimental tribological tests such as pin-on-disc or ball-on-disc tests, exploring various factors including particle type, size, distribution, and processing techniques.Understanding wear mechanisms like abrasive, adhesive, and fatigue wear is crucial for optimizing composite performance and identifying potential applications across industries like automotive and aerospace where materials endure harsh conditions and significant wear[45].
3.2.Wear test results for different loads, track diameter and wt% of ZrO 2 at 400 RPM The table 5 provides a comprehensive dataset of wear rates, measured in milligrams per meter (mg/m), across various combinations of ZrO 2 reinforcement percentages, and applied loads at a constant RPM of 400.

Table 5 .
Wear rate mg/m for different loads, track diameter and wt% of ZrO 2 at 400 RPM.

Table 6 .
ANOVA for wear rate in mg/m at 400 RPM.

Table 7 .
Fit statistics for wear rate in mg/m at 400 RPM.Wear test results for different loads, track diameter and wt% of ZrO 2 at 600 RPM The table 8 presents a comprehensive dataset of wear rates measured in mg/m across various ZrO 2

Table 8 .
Wear rate mg/m for different loads and wt% of ZrO 2 at 600 RPM.

Table 9 .
ANOVA for wear rate in mg/m at 600 RPM.

Table 10 .
Fit statistics for wear rate in mg/m at 600 RPM.

Table 11 .
Brinell hardness (HB) number for different wt% of reinforcements measured across the surface of the composite.

Table 12 .
Brinell hardness (HB) number for different wt% of reinforcements measured across the cross section of the composite.