Tribological and Mechanical Characteristics of Mg–Zn6.0–Y1.2–Zr0.2 alloy by SPS Technique: Natural and Agro-Waste Utilization

In India, urban solid waste generation has risen over the last decade. The aspect of waste generation is a large amount of waste materials among all solid waste types. While using ash particles eliminates waste, it also contributes desirable qualities. In this research work, the effects of Himalayan nettle leaf ash (HNLA) and bean pod ash (BPA) with molybdenum trioxide (MoO3) on the ZWK611 (Mg–Zn6.0–Y1.2–Zr0.2) alloy is examined. The as-cast alloy exhibits an α-Mg matrix, and cubic γ-phases are formed in addition to MoO3 particles. In this work, an attempt was made to choose a ZWK611 alloy reinforced with HNLA and BPA by varying weight percentages (X = 4, 8, 12, and 15%) with a constant weight percentage of MoO3 (5%) fabricated using spark plasma sintering (SPS) technique. The mechanical and physical properties were tested for both as-cast alloy and magnesium hybrid composites. Surface morphology and XRD are analysed to identify material behaviour. The addition of 12% (HNLA-BPA)/5%(MoO3) hybrid composite exhibits high strength as compared to the as-cast alloy.


Introduction
Conventional monolithic materials have restrictions to meet today's demands in the field of advanced technologies. Evolution in material science has led to the birth of composite materials. Today composite is becoming an essential part due to its unique quality and high stiffness-to-weight ratio. Many mixtures used today are at the forefront of advanced materials, exhibiting more capability and cost-effectiveness suitable for demanding applications in the medical and automobile [1]. Nowadays, the owing applications of composite parts have extended their usage in the automobile, defence, aerospace, and medical fields in manufacturing rocker's arms, gear, bearing, and electrical sliding contacts. These have revealed the potential of the SPS technique as an alternative to conventional metal processing. Consolidating the materials does hot Isostatic Pressing and Cold Isostatic Pressing, followed by the sintering process to produce bulk materials [2]. The materials blend the most vital attributes of disparate materials while increasing their physical and mechanical characteristics. Identifying a novel material combination, such as zinc, aluminium, boron carbide, and molybdenum trioxide has propelled investigation into metal matrix composites. The main advantages of using Zr-Y-Zn-Al-Ti with Mg against the other matrix are higher strength, greater stiffness, less density, excellent hightemperature properties, enhanced wear characteristics and damping capabilities suggested by Wang et al. [3]. Ali et al. [4] recommended that magnesium alloy reinforced with particulates like RHA, FA, MoO3, and BA exhibits improved tensile strength, durability, and dry sliding wear behaviour. According to the investigations, the percentage ratio of reinforcement influences composites' mechanical performance and wear behaviour. The spark plasma sintering process involves the incorporation of reinforcement particulates into molten alloy and allowing the matrix to solidify. The critical thing in this process is to create excellent wetting between the base molten alloy matrix and its reinforcements. Liu et al. [5] observed that the SPS technique provides superior matrix particle binding because of the particulates' uniform stirring action into the melts compared to other fabrication methods. The problems associated with the attainment of homogeneous distribution with minimum porosity in sintering and suggested various methodologies and strategies overcome the manufacturing difficulties by Liu et al. [6]. Tan et al. (2014) [7] prepared AZ91D-MoO3/Si hybrid composites by sintering and in-situ reactive synthesis. Under different conditions, the dominant wear behaviour was studied using an EN31 steel disc. At higher load conditions, molybdenum trioxide and ash particles produce flaking traces and grooves on the wear surface, increasing the wear loss in the composites; a rise in sliding speed surface temperature of the specimen also increased. An attempt has been made to study the influence of ZKW611 reinforcing Himalayan nettle leaf ash (HNLA) and bean pod ash (BPA) with molybdenum trioxide (MoO3) on the mechanical properties and wear behaviour of hybrid magnesium composites. Surface morphology is determined using SEM, and phases are obtained through EDS analysis.

Selection of Matrix
The Mg-Al binary system is often used as sintering alloys such as AM50, ZWK611 and AM60 are still needed for a large portion of the study. ZWK611 alloy exhibits more prominent and high strength due to its combination of Zn-Y-Zr in the material [8]. Adding magnesium content to Zn6.0-Y1.2-Zr0.2 improves the material strength based on the solid-solution formation of ZWK611. Magnesium and hybrid composites are an essential category of triboengineering materials generally employed in mechanical components such as cranks, camshafts, lubricants, bushes and bearing plates, where non-lubricated wear performance is a critical factor in material selection.

Material
Molybdenum trioxide (MoO3) has high strength and good corrosive resistance, so the second phase particles were incorporated to increase the strength of the matrix material.
It exhibits better electrical, mechanical, and thermal properties than other materials [9]. Molybdenum trioxide (asreceived) is obtained from Sangam Private Ltd, Chennai, India.

Heat Treatment of Reinforcement Particles into Ash
A plant that produces bean pods is a bean pod (Fabaceae). The residual husks are used to generate a "harvest" once the seeds have been extracted from the pods. In particular in India, the Himalayan nettle leaf is a rare cultivated plant grown in the Himalayan hills' region, and the bean pod ranks are also cultivated in the hill region and are second in terms of cultivation area and production. Figures 1 and 2 represent before and after heat treatment. The bean pod was burned at a Controlled temperature of 620 °C in a muffle furnace for an instance of 2 h, and it turned into ash particles [10]. The Himalayan nettle leaf powder is among the essential raw materials obtained from the palm, which are eco-friendly and alternative to conventional materials. The Himalayan nettle leaf was first carefully scrubbed with warm water to extract dust content and then dried at room temperature for 24 h. Later, it is transmitted to a tube furnace and burned over at a temperature of 480 °C for 120 min.

Fabrication of Magnesium Hybrid Composites
During the last two decades, various documents dealing with the spark plasma sintering (SPS) technique have shown a relatively rapid rise. In recent studies, the procurement of SPS equipment and materials fabrication increased rapidly due to producing complex shapes. As a cutting-edge material processing technique, spark plasma sintering creates uniformity in the distribution of the materials and helps functionally gradient materials, structural components, and wear-resistant thermoelectric semiconductors [11]. It is sustained by pulsating direct current (impulse frequency varies from one ms to one second, with a current amplitude of 0.01-10 kA), which is used in a variety of devices, from the outset to the end. A computer-aided design system and a vacuum chamber are two of the components of SPS devices used. A magnetic field is generated by the common impulse present in SPS equipment. Uniaxial compression occurs as a result of the area and current interacting. A compaction pressure of 30 MPa was utilized during the heating phases, while a vacuum pressure of 16 Pa was applied during the sintering phase. After 32 h of milling, all of the compositions were sintered. Zhao et al. [12] performed AZ91 composites reinforced with zinc and carbon fabricated through the SPS technique. The wear behaviour improved in the particle-reinforced composites due to micro alloying. The milled particles were placed in a graphite die and crushed uniaxially at 20 MPa while subjected to DC voltage. For a 5-min holding period, the sintering temperature was kept at 1000 °C. Using SPS, the heat transfer to the compact is exceptionally dependable because the die and the compressed powder materials are the burners. Dispersing the trigger factors (starting) and joule heat factors throughout the sintering process allows SPS to rapidly create a homogeneous, dense, high-grade sintered tiny. The schematic representation of spark plasma sintering is shown in Fig. 3. The SPS has a high thermal efficiency to produce samples with desired thicknesses (usually several hundred levels lower than the temperatures used during HP) and longer durations (as much as numerous mins). Nano-sized powders can benefit from the SPS qualities outlined above, especially when sintering.

Material Characteristics
The tensile strength, nature of fracture during tensile testing, and microhardness of the welded connections were determined through mechanical testing. ZWK611 and ZWK611/ (HNLA-BPA)/5%(MoO3) hybrid composites were mechanically tested. ASTM guidelines are followed for all the testing processes.

Micro-Hardness Test
Small applied loads in relevant regions were measured using a Vickers microhardness tester. The hardness of the weld zone was measured using microhardness with a 0.05 kg load for 20 s [13]. A Microhardness test was performed on wellpolished alloy samples and ZWK611/(HNLA-BPA)/(MoO3) hybrid composites.

Compression Test
Materials, components, and products can be tested for safety and quality using compression testing at various production phases. It can investigate the properties of a material by performing compression experiments. To determine to withstand a material when the amount of load is applied. In this study, cylindrical samples for the compression test were chosen as 15 × 10 mm with a 0.5 aspect ratio. ASTM E9 standards [13] were followed to conduct compression tests using a computerized universal testing machine.

Tensile Test
The sintering samples were subjected to an ASTM standard E8M-04 [14] polished round bar tensile test with a gauge diameter of 9 mm and a gauge length of 45 mm for each sample. The universal testing machine utilized was an electromechanically controlled universal testing machine with a load of 100 kN. Tensile samples have been examined for yield, tensile strength, and % elongation.

Density
The sintered silicon brass nanocomposite specimens were cleaned with acetone to remove the external contaminants on the surface of the samples. Density was determined using the Archimedes principle using Eq. (1) [15]. The different weight fractions of BPA-reinforced and prepared composites from each composition of three samples are considered to calculate the average density value. It was observed between the mass of the specimen in the air atmosphere and the mass of the specimen in water. The composite specimen's theoretical density was determined by using a rule of the mixture and compared with a mean density.
where, M wat -Water atmosphere, M atm -Air atmosphere

Porosity
Porosity is a significant test in determining the trapped volatiles of a material that can considerably analyse the material's performance. The volume of fluid-filled small gaps is related to the material's overall volume. The pore system can be divided into different porosity if treated as a connecting pore network and channels of small diameters. The experimental density was determined by the Archimedes principle [16]. According to the ASTM B962-13, Porosity (P) was calculated for all the mixtures using Eq. (2).

Tribology Test
The dry sliding wear tests were carried out at room temperature using a pin on the disc device (DUCOM 400) according to ASTM G99 standards. The steel parts were ground to a 6 mm diameter and raised to provide a 30-mill sounded height and polished surface area. The surface roughness of each sample was kept at 1 μm to get uniform contact on the disc. The specimens were washed and dried with acetone, and weight was measured using an accurate weighing machine of 0.001 mg before and after wear check. The weight loss process does the calculation of wear rate. The frictional force was noted during the experiment, and the friction coefficient was measured [17]. The worn surface of selected specimens was analysed using an SEM, and testing conditions are provided in Table 1.

Microstructural Observation
SEM was used to examine the cracked surfaces of tensile test specimens for fractographic information (SEM). High Temperature ( o C) Room temperature and low magnification images can be generated by simultaneously emphasizing several samples. The specimen was coated before testing to maximize its conductivity and limit the high voltage applied to the selection during the testing process. A thin layer of conductive metal, ranging in thickness from 20 to 30 nm, is applied to the specimens [18]. The SEM is one of the most extensively utilized analyses in research and industry because of its high magnification, large depth field, higher resolution, and crystallographic information.

Optical Microscope Analysis
The microstructural characteristics of hybrid composites were analysed using an Optical microscope (OM). OM analyses were performed on four samples to observe the surface morphology characteristics after curing NaCl solution. The OM images of ZWK611, HNLA, and BPA with molybdenum trioxide, respectively. From the visual observation of the images obtained from the OM analysis, it is observed that the base alloy is characterized by small pores (Fig. 4a), which may be the reason for the reduction in its strength compared to all other materials. The MoO 3 with all materials is densely packed, which reduces the voids, as shown in Fig. 4b-d. The pores have been refined by adding 12% (HNLA-BPA)/5%MoO 3 hybrid composite. Due to the filler effect, the porosity level is reduced by adding molybdenum trioxide and ash particles.

Particle Size Distribution
Product properties are directly related to the particle size distribution of a given material, making it a significant analysis parameter in quality control operations and research applications. Particle size distribution affects the strength and transmitting behaviour, abrasiveness, extraction, and reaction characteristics of bulk materials. Figure 5a-c represents the size distribution of ZWK611 alloy, and magnesium hybrid composites are described in the form of a histogram. The particle size of ZWK611 is observed as 32.03 µm and is shown in Fig. 5a. The particle size of Himalayan nettle leaf ash and bean pod ash is 10 µm and is shown in Fig. 5b-c. In contrast, molybdenum trioxide is 15 µm (Fig. 5d). According to Zhang et al. [19], the particle size distribution affects the material's characteristics. As far as particle distribution is concerned, wettability appears to be an essential factor.

XRD analysis
It is mainly used for phase identification and analysis of mixtures of crystalline structure. Figure 6 shows the  103) and (002) indicated the crystal structure of magnesium alloy, as shown in Fig. 6a. The HNLA-BPA reinforcing particles lower the magnesium peak. The decreasing peaks confirm the inclusion of carbon, silica, and iron content due to the addition of 6%(HNLA-BPA)/5%(MoO3) hybrid particles. The hexagonal crystal structure with a peak 2Ɵ value is 21.16°, which matches the (003) plane, confirms the presence of molybdenum trioxide and is shown in Fig. 6b-c. Ovali et al. [20] illustrate that molybdenum trioxide and fly ash content in the Mg alloy will form a vital phase at the alloy-particle interface during sintering and tends to improve the corrosion and wear resistance and machining characteristics of the alloy. The diffraction pattern shows the presence of 12%(HNLA-BPA)/5%(MoO3) hybrid composite possessing a strong peak (Fig. 6d) since it leads to improving the wear and mechanical behaviour of the hybrid composites. In addition, beyond 12% hybrid composite may lead to weak peak results in decreasing O and C content attributed to high porosity and low density. Hence, XRD analysis indicates the presence of reinforcement particles influences the matrix.

Porosity Test
The term porosity is widely used to identify voids. Composite materials are generally caused by the issue of porosity, particularly in metals and fibres. Keeping porosity to a minimum is necessary to obtain a high machining performance. The porosity of matrix and magnesium hybrid composites is labelled in Table 2 and calculated using Eq. 2. The results show that high porosity is obtained for a base alloy of 2.49% due to more agglomeration and is reduced by adding reinforcement particles. The porosity level decreases with the increase of 3 to 6% of BPA and HNLA particles.
The low porosity (1.82%) is achieved due to the presence of molybdenum trioxide and increasing ash content up to 10%, resulting in reduced open pores compared to alloy. A similar trend is observed by Abdullaev et al. [21] in the show that molybdenum trioxide with an ash component is more effective in removing pores and improving the hybrid composites' mechanical properties. Including a 12% hybrid composite causes the matrix's porosity to increase due to pore nucleation at the matrix interface. In a 12% hybrid composite, the reduction in porosity can be attributed to the well-wetted hard particles and uniform dispersion of these particles in the matrix. Further increasing the concentration to 15% hybrid composite tends to increase the porosity (2.2%) which is due to an effect of low wettability and high agglomeration. Pore nucleation at the matrix interface is also the reason for higher porosity. Ash/silica particles fill more pores, and the number of open pores decreases in hybrid composites. Therefore, 12% (HNLA-BPA)/5%(MoO3) hybrid composite exhibits a lower porosity than alloy and other hybrid composites.

Density Test
The experimental and theoretical density of ZWK611 alloy and hybrid composites are listed in Table 2. As the bulk volume increases, the surface pores become smaller suggested by Khaleghi et al. [22] performed a bulk density test by varying different weight fractions. It is identified that increasing the weight fraction of ash particles with molybdenum trioxide reduces density. This study uses Archimedes' principle to measure density, as shown in Table 2. The experimental density of 12% (HNLA/BPA)/5%MoO3 hybrid composite shows a lower density (1.95%) compared to the theoretical density (2.02%). However, with the increasing weight of reinforcement particles, the experimental density is increased due to soaking particles, disturbing alumina and silica content. Further addition of 12% hybrid composite tends to increase the density level. High powder contamination and shorter distances between pores-dominated particles can be attributed to small fragments mixed with larger sizes. Overall, the theoretical density is lower than the experimental density in all compositions. Therefore, comparing the results, the inclusion of reinforcement particles into the ZWK611 alloy showed lower experimental density than comparing to theoretical density.

Microhardness Test
To study the hardness of the ZWK611 alloy and ZWK611/ (HNLA-BPA)/5%(MoO3) specimens at high precision, a Vickers micro-hardness tensiometer is used. The diamond pyramid indenter was used to carry out the Vickers microhardness test. The VHN hardness value of Mg alloy is 70.4 HN, and standard deviations are shown in Fig. 7. The addition of reinforcement particles increases the strength to 81.4 HN, respectively. The hardness values of 4% to 8wt% are better than the matrix where the reinforcements act as strengthen behaviour. Figure 7 shows samples 4% and 8% hybrid composite values will lie between 74.7 and 80.3 HN. The 12%(HNLA-BPA)/5%(MoO3) hybrid composite was found to be higher hardness than the other composites due to the increasing weight fraction of reinforcement particles; the hardness value increased gradually. The improvement in the hardness of the composite is also due to the formation of homogenous dispersoids [23]. It might refine the grain size of the matrix, improving the composite's property. Further increasing 12%, the specimen reduced tensile strength due to poor wettability. Therefore, it is identified that the reinforcement particles influence the property of the matrix, and

Tensile Test
The tensile strength of ZWK611 alloy reinforcement various weight fractions of BPA and HNLA mixtures is represented in Table 3. Servo-controlled universal testing equipment is used to perform tensile tests on cylindrical samples. A higher percentage of ash particles containing molybdenum trioxide in the composite results in an increased, ultimate tensile strength. It can be seen in the test results, which show a rise in tensile strength as the ratio of reinforcement increases. The high tensile strength of the hybrid composites can be attributed to the presence of reinforcement particles in the matrix rather than the ZWK611 alloy. It improves as BPA and HNLA particles increase from 4 to 8% of the aggregate. The tensile strength of ZWK611 alloy is 5.2 MPa, whereas for addition, ashes with constant molybdenum trioxide-based 4% and 8% hybrid composite are found to be 5.9 MPa and 6.5 MPa, and increase to 24% greater than a matrix. Due to 12% of BPA and the solid adhesive phase of HNLA with 5% of MoO3, there is a rapid increase in strength. The addition of the S 4 mixture displays high tensile strength (7.3 MPa) due to low porosity. Stalin et al. [24] examined the 7072/10%SiC/5%MoO3 composite was identified that silica with molybdenum trioxide particles exhibits a homogenous distribution and is well bonded with magnesium, leading to a 21% increase in yield strength and a 16% increase in elastic modulus compared with the unreinforced magnesium alloy. When 15% of HNLA and BPA are added to the alloy, the tensile strength decreases to 261 MPa due to low wettability.

Compression Test
The compressive test with a varied weight percentage of ash particles and a molybdenum trioxide of hybrid composites is performed according to ASTM standards for all mixes. The compression strength findings for both ZWK611 alloy and magnesium hybrid composites are shown in Fig. 8. The plotted results determine the desired level of addition of BPA and HNLA with MoO3. The decreases in compressive strength for ZWK611 alloy are observed due to high porosity and low wettability, as shown in Fig. 8. In contrast, the strength is improved by increasing the weight fraction of BPA and HNLA content with molybdenum trioxide. The test outcomes show that the compressive strength increases by 23% in between 4 and 8% replacement of ash content are higher than a matrix. Cui et al. [25] developed the Mg/calcium polyphosphate/RHA hybrid composites by SPS technique at varying five different weight fractions. It suggested that because of better wettability, a more significant bit of molybdenum trioxide and RHA particulates can be incorporated into the matrix and may lead to increased hardness and tensile strength. Moreover, adding a 12%(HNLA-BPA)/5%MoO3 hybrid composite shows high compression strength of 128 MPa and standard deviations are shown in Fig. 8. When molybdenum trioxide with ash particles is incorporated into the matrix, the strength of the composite increases significantly. Thus, a 12% hybrid composite enhances the mechanical properties. A further rise in hybrid composite content above 12% causes a reduction in compressive strength due to an instability mix and nonhomogeneous content.

Tribological Behaviour
The tribological test includes the study of wear, friction and lubrication principles. The composite sample was rubbed against the abrasive paper of 600 grit papers at different parameters such as sliding load, speed and sliding distance in multi-pass conditions. Looking at wear behaviour in the manufacturing and metallurgy fields is essential to determine a material's resistance. A lubricant is dispersed in a solution employed in this work to increase the wear resistance. The initial weight, final weight and change in weight of as-received ZWK611 alloy and all SPS composites are labelled in Table 4. The weight of the specimens was measured using a digital weight machine having the least count of 0.001 g. The change in weight change was negligible for ZWK611 alloy and hybrid composites. However, a noticeable weight change was observed for ZWK611 alloy and the other two compositions of sintering composites. The change in alloy weight was more significant than that of the two different compositions of SPS composites. From Table 4, the difference between initial and final weight decreases and is observed with the addition of 5%MoO3 with the increase in the weight ratio of HNLA/BPA particles, respectively. The ASTM G-99 standard [27] was used to evaluate dry sliding wear using pin-on-disc equipment. Each sample was cut with an EDM with a diameter of 20 mm and a length of 10 mm. A vertical pin on a revolving metallic piece spins on an EN 31 steel disc with a predetermined centre point. The sliding wear rate of ZWK611 alloy is 1.6 × 10-3 mm 3 /m, which improves by adding reinforcement particle from 4 to 12% is 1.2 × 10 -3 mm 3 /m, 0.8 × 10 -3 mm 3 /m, 0.5 × 10 -3 mm 3 /m, and 0.4 × 10 -3 mm 3 /m, respectively. It leads to the conclusion that ZWK611/12% (HNLA/BPA) with 5% MoO3 has better wear resistance than other compositions.

Wear loss and C.O.F Analysis by Varying Reinforcement Particles
The wear loss analysis and friction coefficient by varying 4-15% (HNLA/BPA) with 5%MoO3 is shown in Fig. 9.
Abrasive wear occurs when two smooth, flat surfaces come into contact in dry or lubricated conditions. Abrasive wear is   Figure 9a shows higher wear loss (0.014) than hybrid composites due to low hardness and porosity. In contrast, adding molybdenum trioxide and ash particles reduces wear loss from 3.53 to 2.14 g and improves wear rate. The lowest wear loss (0.08) is found in adding 12% hybrid composite. A similar trend is found in coefficient friction. The lowest wear loss is identified as attributed to silica and alumina content leading to improved wear resistance. Hence, the adhesive wear is demolished, and low C.O.F and wear loss are achieved in addition to 12% (HNLA/BPA)/5% MoO3 hybrid composite. Since the specimen's surface has a mechanically mixed layer due to the transfer of metallic particles from its counterface, it is the primary cause. Suresh et al. [26] performed on Steel discs with varied weights ranging from 50 to 100 N were subjected to the adhesive wear behaviour of magnesium alloy and magnesium hybrid composites at a sliding velocity of 3 m/s. It concluded that adding molybdenum trioxide particles improves wear rate and lowers friction coefficient at all sliding conditions. It is further noticed an increase in wear loss and friction coefficient in addition to 15% hybrid composite due to reducing hardness strength and increasing porosity.

Effect on Wear Loss by Varying Applied Load, Sliding Speed and Distance
Under three distinct sliding conditions, variations in alloy and composite wear loss on 600-grit MoO3 paper are  Fig. 10a-c. The wear data of the composites reveals that the wear loss tends to decrease with increasing weight fraction of reinforcement particles, as shown in Fig. 10a. It is noticed that wear loss from the ball is significantly high in the sliding pair and later linearly reduced in increasing 4 to 15% of reinforced particles. Adding 12% (HNLA/BPA) with 5%MoO3 particles exhibits low wear loss due to presence of molybdenum trioxide and ash content. Increasing the mechanical characteristics and tribolayer effect is crucial for including reinforcing component form, which may reduce wear loss. Zheng et al. [27] investigated different weight fractions of ash concentration that are known to improve magnesium alloy's mechanical and wear rate. The wear rate of the matrix decreases and then increases as the applied loads increase from 40 to 80 N, resulting in a surface loss. Similar observations were made by Banerjee et al. [28]. The wear behaviour with varying sliding speeds of 3 to 5 m/s at a constant 60 N load and 2000 m of magnesium alloy and magnesium hybrid composite is shown in Fig. 10b. The addition of HNLA-BPA particles can considerably improve the wear resistance of magnesium composites. The presence of molybdenum trioxide in the matrix can form a thin layer on the surface, restricting cracks and making the composite more strength. As a result, adding 12% hybrid composite increases wear loss and decreases delamination wear under all sliding regimes. Material removal is accelerated by the grain ploughing and cutting action when the pin slides at high speed. Further addition of 15% the wear loss is increased due to low hardness and material turns to plastic deformation. Figure 10c represents the wear loss measured with a constant load of 60 N at a sliding speed of 3 m/s by varying sliding distances of 1000-3000 m, respectively. Kumar et al. [29] concluded that increasing the weight fraction of fly ash with molybdenum trioxide particulates improved the mechanical properties of magnesium alloy. Also, increased wear resistance plays an essential role as a solid lubricant. In this study, increasing reinforcement content from 4 to 8% indicates that the material possesses a protective surface film to improve the wear rate and reduce wear loss. The improved strength is mainly contributed by adding 12% reinforcement particles to minimize wear loss. It specifies molybdenum trioxide particle improves the wetting of the base alloy and its reinforcements suggested by Yan et al. [30]. Therefore, it is concluded that molybdenum trioxide particles perform as fillers, and adding ash particles will help improve wear resistance over the matrix. When fillers are used, they primarily increase mechanical characteristics, considerably impacting tribobehaviour. Changes in weight fractions of reinforcement particles directly impact tribological properties.

Analysis of Coefficient of Friction on Various Parameters
The materials will differ slightly at varying sliding conditions, as shown in Fig. 11. The coefficient of friction is reduced with an increasing weight fraction of reinforcement particles. However, as the load increases from 60 to 80 N, the pin comes into contact with the counter disc material and tends to small tinning on the subsurface with a constant speed of 3 m/s and a sliding distance of 2000 m as shown in Fig. 11a. Hence at a higher load, the C.O.F of an alloy is higher; it decreases with the addition of molybdenum trioxide particles. The lowest friction coefficient is observed in addition to 12% (HNLA/BPA) with 5%MoO3 hybrid composite is 0.46, which is nearly 36% less than an un-reinforcement alloy. However, a significant friction coefficient and wear rate reduction are measured when the incorporation of molybdenum trioxide with ash particles in magnesium alloy. The figure reveals that reinforcing particles can reduce matrix rubbing during abrasion, resulting in less damage. A transmission layer and efficient barriers are provided by the ASP/BPA ash particles, preventing large-scale fragmentation. Zeifert et al. [31] made the same findings. When the pin initially appears on the contact area, abrasion wear can be seen, and as the sliding distance increases, the base alloy becomes sensitive to oxidation. At constant load 60 N and sliding speed 3 m/s by varying sliding distance from 1000 to 3000 m as shown in Fig. 11b. In addition, 12% hybrid composite results in low C.O.F. compared to other composites at sliding distances and improves wear resistance. Due to the incorporation of ash and molybdenum trioxide particles, the coefficient of friction dramatically decreases, reducing wear debris. Similar observations were made by Thirugnanasambandham et al. [32]. Figure 11c represents the variations in C.O.F at varying sliding speeds of 3-5 m/s with a constant sliding distance of 1000 m and a load of 60 N. It is observed that, while increasing sliding speed coefficient of friction is higher for alloy. This causes worn debris to accumulate on the disc surface, which results in the formation of a tribo layer at a sliding speed of 4 m/s. This effect is minimized with the addition of reinforcement particles helps to improve friction coefficient and reduce debris-filled by silica and ash particles. Zheng et al. [27] performed the wear behaviour of magnesium/MoO3 composites by choosing 2-5 m/s speed at a constant load of 70 N and concluded at all sliding speeds that the coefficient of friction was found to improve when silica was silica added. The C.O.F. is increased in addition to 15% hybrid composite due to low hardness and rising porosity level, leading to reduced wear resistance. Material strength is increased as a result of the increased resistance to wear. Therefore, because of molybdenum trioxide and ash in the alloy, adding

Wear Debris
The SEM micrographs from Fig. 12a-e revealed the test samples' linear elastic behaviour and brittle-type fracture. Initially, the cracks are observed in an alloy (Fig. 12a) because layers of the composite and void nucleation at high sliding circumstances lead to increased wear debris. The degradation of the material was primarily due to particle cracking. Adding reinforcement particles to an alloy matrix reduces the plastic flow of the resulting nanocomposites. Deformation behaviour changed from ductile to brittle with the addition of 4-8% hybrid composite (Fig. 12b-c) because of the presence of triaxial stress in the area around the particles. The pores are reducing, and dimples on the surface were relatively lower than alloy due to molybdenum trioxide and ash content, which will restrict plastic flow in the sintered samples. Figure 12d shows that low debris is observed, and 12% hybrid composite results in a smooth surface and improving wear resistance. Increased molybdenum trioxide and palm oil shell ash particles, according to Thirugnanasambandham et al. [33], improve the Mg matrix wear characteristics. As the matrix level rises, the fracture surface will transform from brittle to ductile. The increase in wear debris was found in the addition of 15% hybrid composite attributed to high agglomeration, and increasing porosity leads to cracks in the material. An improved worn surface is due to less wear debris, making it ideal for orthopaedic applications and the production of industrial connecting rods and pistons.

Conclusions
This project objective is to reduce the potential waste generated at the outset. Additionally, adding Zn6.0-Y1.2-Zr0.2 to Mg alloy with constant molybdenum trioxide was fabricated through the SPS technique. The following conclusions are drawn: • Percentage of reinforcement particle directly impacts mechanical properties. An increase in the inclusion of particulates restricts the deformation of a material, resulting in improved tensile strength and hardness.
• The addition of reinforcing particles enhanced the strength of the material by 18.06% (hardness), 24.03% (compression), and 42.32% (splitting tensile) compared to the base alloy. • The porosity is improved (1.81%) by the addition of 10%(HNLA-BPA)/5%(MoO3) hybrid composite. • The formation of voids and cracks characterizes using the TEM analysis of the fractured tensile test samples. In comparison, adding ZNK611/12%(HNLA-BPA)/5%MoO3 hybrid composite shows a smooth surface as a compared matrix.

Wear Properties
• Wear loss and coefficient of friction of hybrid composites lowered with an increased weight ratio of reinforcements in an alloy matrix. • The HNLA/BPA with 5% of MoO3 particulates influenced the wear rate. Increased reinforcing particles will restrict sintering specimen deformation, and thus lowest wear loss is achieved. • The low sliding speed and wear rate directly correlate; raising the sliding speed improved the wear rate. The matrix phase thermally softens and reduces the bonding efficiency of the reinforcements with the base alloy at high-speed circumstances, resulting in increased wear. The wear rate of the hybrid composites rises with an increase in load but drops marginally with increasing sliding distance. • The coefficient of friction has an inverse relation with the weight fraction of reinforcement particulates, sliding speed and applied load. The coefficient of friction dropped as the percentage of reinforcements increased with the sliding parameters. Ploughing indication for wear debris and MML impacts the wear behaviour of composite materials.