INTRODUCTION
As a result of technological developments in recent years, which have required special properties not provided by metals alone, such as high strength and corrosion resistance, researchers have considered producing metal composites consisting of a specific combination of metals to achieve special properties [1-3]. One important material in this context for use as a matrix for producing composites is aluminum composites (AMCs) reinforced with ceramic particles [4]. Aluminum alloys play an important role in many industries and technological circles, including the automotive, aerospace, and defense industries [5,6]. However, compared to Al pure and alloys have lower ductility and higher strength, making them ideal for use as a matrix [7]. Al and its alloys’ remarkable resistance to air corrosion has been demonstrated by numerous investigations to be due to their capacity to produce an oxide layer that shields them from outside effects, particularly corrosive solutions. [8-11]. By modifying the surrounding corrosive environment, various corrosion inhibitors can be applied to increase corrosion resistance. Interestingly, these inhibitors consist of alloying components and surface anodizing. Despite these distinct properties of Al alloys, aluminum nanocomposites (AMCs) are not as desirable as other homogeneous alloys [12-14]. The disadvantages of these nanocomposites include internal stress, manufacturing defects, and microstructural variations, which ultimately lead to galvanic effects. Several researchers have studied Al alloy matrixes. For example, Zhu et al. 2022, [15] developed an aluminum alloy coated with tin oxide (SnO2) thin film. The results showed that adding 8% silicon carbide (SiC) particles significantly increased the tensile strength and toughness of the alloy by approximately 26% and 46%, respectively. Aluminum alloy was hand-cast with SnO2 nanoparticles to produce nanocomposite powders with different SnO2 concentrations. These powders were pressed and heat-treated in the presence of argon, where the increase in SnO2 significantly improved the compressive strength and toughness of the nanocomposites [16]. There are several techniques and methods for preparing nanocomposites of Al and its alloys, such as powder metallurgy (PM) [17, 18], micro-agitation [19], compression casting [20], and stir casting [21]. The latter provides a homogeneous distribution of particles in the microstructure and is a modern and economical method for efficiently dispersing reinforcements into the matrix [22,23]. As a result of these significant advantages, mechanical alloying (MA) is one of the best surface treatment techniques for producing nanocomposites. This method enables control of the size and shape of the reinforcing additive. The mechanical alloying process involves crushing and welding powder particles. The process is highly dependent on important parameters such as grinding time, speed, grinding type, ball-to-powder ratio (BPR), and flask/ball material [24]. Al alloys made via powder metallurgy can benefit from the addition of SnO2 as a strengthening agent. Within the metal matrix, SnO2 functions as finely dispersed reinforcing particles. Dislocations, which are flaws in the metal’s crystal structure, are hampered by these particles. The alloy’s strength and hardness are increased by retarding dislocation movement [25, 26]. In this work, we conducted a comprehensive investigation to improve the mechanical properties, flexibility, and resistance to wear and corrosion, by doping the Al-SiC alloy with varying weight percentages of tin oxide nanoparticles generated by the metal powder method, where mixed with different ratios of SnO2 (3, 6, 9, and 12) wt% using powder metallurgy method.
MATERIALS AND METHODS
The matrix in this study was Al–SiC alloy, and the tin oxide nanoparticles (less than 80 nm) were reinforced with 0, 3, 6, 9, and 12 weight percent (Table 1). The Al–SiC alloy was made by the mechanical alloying process. Al (99.9%), SiC (99.9%) were the ingredients. For 24 hours, the Al alloy’s constituent parts were combined in a planetary ball mill spinning at 130 rpm. These mixtures were put through a 24-hour grinding process at 500 rpm in order to create nanocomposites. The grinding procedure was done in two-hour cycles with two-hour break periods. XRD and SEM were used to characterize the mechanically cast powders in order to examine their morphology. A diffractometer was used to quantify the particle size in order to determine each powder’s average distribution pattern [5]. Using the Scherrer equation, the intensity of the diffraction peaks was used to determine the crystallite size of the ground powders. After that, the powdered powders were crushed and sintered in an argon atmosphere for an hour at 550 °C. It is significant to remember that the mixing rule was used to determine the specimens’ theoretical densities, accounting for the fact that the density of SnO2 is 5.68 g/cm3 and that of the Al-SiC alloy is 2.7 g/cm3. However, the bulk density and obvious porosity were measured using the Archimedes approach. Utilising a scanning electron microscope, the microstructure of the sintered specimens was examined (SEM; Philips XL30). Shimadzu-HMV (Japan) was used to test the micro-Vickers hardness (HV) in accordance with ASTM standard B933-09, as detailed in reference [25]. Additionally, the sintered nanocomposites underwent compression testing in compliance with ASTM standard. The maximum levels of stress and strain on the stress-strain curve correlate to the ultimate strength and elongation, respectively, since the stress-strain curve was utilised to calculate the final strength, yield strength, and elongation. A pin-on-disc testing equipment was used to conduct the wear test, and a digital scale with a 0.0001 g precision was used to weigh and measure the samples. Every sample had the same size and was processed coarsely using varying grades of grinding paper (600 to 4000). Four distinct loads were used in the test. The following formulas were used to determine the wear rate brought on by weight loss [27]:
RESULTS AND DISCUSSION
Fig. 1 displayed the XRD patterns of the AS0, AS3, AS6, AS9, and AS12 nanocomposite powders. Based on the reference card numbers (JCPDS 01-089-4037 and 96-901-2197), the primary phases of the powder are Al and SiC, respectively, as the XRD pattern of sample AZ0 (matrix) makes evident. XRD results showed that the characteristic aluminum peaks at angles (39.51°, 44.73°, and 65.12°) remained clearly visible with almost no change in location or intensity across all samples, indicating that the primary phase was not affected by the presence of SnO₂. Silicon carbide (SiC) peaks at angles (60.32°, 7°, and 2.64°) were also prominent and stable, reflecting its homogeneous distribution in the metal matrix [28]. However, depending on card numbers, SnO2 peak arise from its addition in varying amounts (JCPDS 86-1450). The results also showed that with increasing SnO₂ content, new peaks appeared at angles such as 26.61°, 33.95°, and 51.83°, attributed to the tetragonal phase of SnO₂. The gradual increase in intensity of these peaks indicates increased precipitation of this compound within the structure, without crystalline interference with other phases, indicating a phase segregation pattern. These results suggest that the increased presence of SnO₂ in the form of finely dispersed particles enhances the potential for solid dispersion reinforcement, leading to improved yield strength and hardness [29]. Its presence alongside SiC also contributes to dual microstructural reinforcement, which enhances the overall mechanical performance of the alloy, especially in applications requiring high corrosion resistance and hardness [30]. The results also indicate that the powder metallurgy technique allowed for the homogeneous distribution of both SiC and SnO₂ within the aluminum matrix, without the occurrence of undesirable interfacial interactions or secondary phases, enhancing the efficiency of this method for preparing nanoscale or advanced alloys [31]. As seen in Fig. 2, it can be inferred that the breadth of the crystallite grows and its density dramatically lowers as the weight % of SnO2 steadily increases. This results in a decrease in the size of the crystallite. Samples AS0, AS3, AS6, AS9, and AS12 have average crystallite sizes of 32.25, 31.35, 29.43, 24.99, and 19.53 nm, respectively. These results match the results of the researcher (Özay et al., 2018) [32].
Compaction of mixed nanocomposite powders is frequently a crucial step to getting bulk materials following sample preparation. As a result, this procedure controls the final sintered compacted materials’ porosity and nanoscale structure [33]. The relative intensity and obvious porosity of the felt samples after an hour at 550 °C are described in Fig. 3, which also displays the bar graph that represent the weight percentages of SnO2. Additionally, Table 2 provides the standard deviation of the observed relative density with apparent porosity. The AS0, AS2, AS4, AS8, and AS16 samples have theoretical densities of 2.66, 2.69, 2.72, 2.78, and 2.91 g/cm3, in that order. Following sintering at 550 °C, the AS0 and AS16 samples have relative densities of 93.23 and 85.97%, respectively. The compressive strength of the sintered samples with greater SnO2 weight percentages may be decreased as a result of the strength of the SnO2 ceramic particle in the Al alloy matrix. Furthermore, the SnO2 hardener has a melting point of about 1630 °C, which is significantly higher than the Al matrixes. Therefore, the high quantities of SnO2 act as a barrier to diffusion stages during the sintering procedure and inhibit it [34]. On the other hand, by fostering more interparticle hugs and enhancing the degree of connectedness between them, the sintering temperature of 550 °C can successfully increase the relative density. [35] The samples’ relative density dropped from 97.57 to 92.12% when the SnO2 level was increased from 0 to 12 wt% (Fig. 4).
Following 20 hours of grinding and compression at 50 MPa, SEM images of the compacted AS0, AS6, and AS12 nanocomposite powders were displayed in Fig. 5a–c. The placement of SnO2 nanoparticles in the well-densified Al alloy matrix significantly influences the mechanical and electrical characteristics of the finished nanocomposites, according to a careful examination of the SEM images. The SEM pictures of the nanocomposites with varying SnO2 nanoparticle concentrations that were sintered at 550 °C were displayed in Figs 5d–f. SnO2 nanoparticles are usually found along the matrix’s grain edges in aluminum alloys. A uniform distribution of SnO2 particles is seen in the sample with the lowest SnO2 level; as the SnO2 content increases, this fine distribution becomes less pronounced. As a result, the SnO2 particle distribution is uniform in both AS6 nanocomposite specimens but diminishes in the AS12 samples. Interestingly, in the examined samples, porosity showed the reverse pattern, rising as the quantity of SnO2 particles increases. However, a greater densification behavior is produced, which is almost full density. The contact boundaries between the particles seem to widen through the sintering stage of the nanocomposite samples, suggesting that a strong binding between the nanocomposite matrix and SnO2 was achieved and that there were no holes in the SnO2 particle area [36]. These results match the results of the researcher Lai et al., 2021 [37].
Non-destructive ultrasonic technology (NDT) was used to assess the longitudinal (VL) and cut (VS) ultrasonic quickness of the sintered samples at 550°C (Fig. 6). It is important to note that increased ultrasonic velocities result from raising the SnO2 concentration from 3 to 12 weight percent. The findings indicate that when the quantity of SnO2 increased, the specimen VL and VS amount varied from 5886.5 to 7510.3 and 3205.7 to 4027.3 ms-1, respectively. Fig. 7 shows the elastic moduli of the nanocomposites under investigation. The figure shows that, in relation to the ultrasonic velocities, the elastic moduli exhibit a similar pattern [38]. For instance, the AS0 sample has an elastic modulus of 89.7 and a Poisson’s ratio of 0.2896 GPa. Interestingly, after adding 12% SnO2, they rose to 150.6 GPa and 0.2983 GPa, respectively. In complete agreement with the accurate results for microhardness and strength of compressive, the inclusion of SnO2 nanoparticles as reinforcement greatly increased the elastic moduli and ultrasonic speeds. These results match the results in the same line of the researcher Khan et al.,2024. [39].
Fig. 8 shows the average microhardness (HV) values of Al-SiC alloy and Al-SiC: SnO2 nanocomposite samples that were annealed at 550°C. As the quantity of different SnO2 particles of Al alloy matrix high, the findings demonstrate a considerable increase in microhardness values. The microhardness of the Al alloy matrix increases from 431.13 to 1124.6 MPa with the addition of 12 weight percent SnO2. The enhanced microhardness of the nanocomposite specimens can be attributed to a number of factors, including the presence of ceramic parts, the even distribution of reinforce within the matrix, and the Al alloy matrix’s decreasing grain sizes as the concentration of SnO2 increases [39].
A histogram plot of the wear rates of AS0, AS3, AS6, AS9, and AS12 samples under loads of 10, 20, and 40 N is displayed in Fig. 9. The standard deviation of the observed wear rates is also displayed in Table 3 The results show that although the nanocomposite samples’ wear resistance tends to increase with increasing SnO2 concentrations, it tends to deteriorate with increasing load [40, 41]. An unreinforced sample (AS0) will corrode at rates of 0.01 g/s, 0.0084 g/s, and 0.0126 g/s when stresses of 10, 20, and 40 N are applied.
CONCLUSION
In this study, SnO2 nano powder and Al-SiC alloy nanocomposites were made via powder metallurgy. The study’s conclusions were as follows:
The findings demonstrated that the produced nanocomposites had observable agglomerations and a uniform dispersion of tin oxide nanoparticles inside the alloy matrix.
As the amount of tin oxide particles increased, the particle size shrank until it reached 45.9 nm for the sample that included 12% tin oxide by weight.
As the quantity of tin oxide in the samples grew, the obvious porosity increased but the relative density dropped.
As the quantity of tin oxide grew, so did the elastic modulus. The bulk and elastic modulus increased to 71% and 69%, respectively, with the addition of 12% tin oxide by weight.
The microhardness, ultimate strength, and yield strength all rose in proportion to the quantity of tin oxide. The AS12 sample’s maximum microhardness and ultimate strength values were approximately 1.9 and 2.2 times more than the AS0 sample’s, respectively.
Wear rates in the sample rose as the load increased, but they fell as the SnO2 level rose.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.