Exploring the mechanical and microstructural characterization of stir cast aluminum 8011 matrix hybrid composites

Abstract

Aluminum matrix composites (AMCs) are increasingly vital in aerospace and automotive industries due to their superior strength-to-weight ratio and enhanced mechanical properties. This study explores the mechanical performance of AA8011 aluminum matrix composites reinforced with silicon carbide (SiC) and titanium diboride (TiB2), fabricated using stir casting. The selection of SiC and TiB₂ addresses the need for improved hardness, wear resistance, and tensile strength in lightweight materials. Comprehensive mechanical characterization, including tensile strength, hardness, flexural strength, and impact resistance, demonstrated significant improvements. The tensile strength increased from 64.25 MPa to 69.75 MPa, while Vickers hardness rose from 29.9 HV to 69.03 HV, indicating the effectiveness of reinforcement. X-ray diffraction (XRD) confirmed the presence of reinforcing phases, and scanning electron microscopy (SEM) revealed a uniform distribution of particulates, minimizing porosity and enhancing mechanical integrity. Microstructural analysis of fractured surfaces displayed ductile failure characteristics, with micro void coalescence and nucleation sites contributing to the improved mechanical behavior.

Keywords:
Stir casting; Hybrid composites; Titanium diboride; Silicon carbide; Aluminum 8011; Mechanical Properties

1. INTRODUCTION

In recent years, Composite materials have emerged as a transformative class of engineering materials that combine the desirable properties of two or more constituents, thereby offering a superior strength-to-weight ratio, high fatigue strength, low wear rate, and improved machinability compared to conventional materials [¹,²,³,⁴,⁵]. The integration of hard, rigid ceramic particulates with metal matrices not only enhances physical and mechanical properties but also improves tribological performance. In particular, metal matrix composites (MMCs) prepared by reinforcing aluminum alloys with ceramics such as silicon carbide (SiC), titanium diboride (TiB₂), aluminum oxide (Al₂O₃), boron carbide (B₄C), zirconium diboride (ZrB₂), and titanium carbide (TiC) have shown substantial improvements in hardness, tensile strength, and thermal stability [⁶,⁷,⁸]. However, challenges remain in achieving a uniform dispersion of these reinforcement particles and ensuring strong interfacial bonding within the composite. Among the various aluminum alloys used as matrix materials, AA8011 has been recognized for its excellent formability, high corrosion resistance, and good thermal conductivity [⁹, ¹⁰]. Despite these advantages, AA8011’s moderate hardness (typically 29–35 HV) and its susceptibility to wear under dynamic loading conditions restrict its application in high-stress components such as brake rotors, engine pistons, and structural fasteners [¹¹,¹²,¹³,¹⁴,¹⁵,¹⁶]. To overcome these inherent limitations, the addition of ceramic reinforcements such as SiC and TiB₂ has been extensively explored. The inclusion of these reinforcements enhances both the mechanical and tribological properties of the base alloy while preserving its low density, which is essential for lightweight applications [¹⁷]. SiC is known for its exceptional hardness, which is approximately 28 GPa, and its high wear resistance and thermal stability up to 1600°C [¹⁸]. These properties make it a favored choice for improving the wear and abrasion resistance of aluminum composites. However, the use of SiC in MMCs is not without challenges; its poor wettability with molten aluminum often leads to the agglomeration of particles and weak interfacial bonding [¹⁹,²⁰,²¹]. This, in turn, can limit load transfer efficiency and reduce the overall performance of the composite. In contrast, TiB₂ offers excellent wettability with molten aluminum and forms a beneficial Al₃Ti transition layer at the interface [²², ²³]. This layer significantly enhances interfacial bonding and stress distribution, contributing to improved fatigue resistance and mechanical strength. Despite TiB₂’s advantages, it does not inherently provide the same level of wear resistance as SiC. Therefore, a hybrid reinforcement approach, which combines both SiC and TiB₂, has been proposed to achieve a balanced enhancement of both mechanical and tribological properties in aluminum composites. The development of such hybrid composites through conventional casting methods presents two major challenges. First, the density difference between the ceramic reinforcements and the aluminum matrix makes it difficult to achieve a homogeneous distribution of the particulates during the melting and stirring processes [²⁴]. This non-uniform dispersion can lead to regions of particle clustering and increased porosity, which compromise the structural integrity of the composite. Second, the inherent difficulty in wetting ceramic particles with molten aluminum results in weak interfacial bonding between the matrix and the reinforcement, thereby limiting the potential improvements in mechanical properties [²⁵]. Among the various fabrication techniques available, stir casting has gained widespread acceptance due to its simplicity, cost-effectiveness, and ability to mix the matrix and reinforcement materials uniformly when optimized processing parameters are employed [²⁶]. Recent studies have focused on the effects of processing parameters on the microstructural and mechanical properties of MMCs [²⁷]. Researchers have observed that optimizing stirring speed, preheating temperatures of the reinforcements, and melt pouring temperatures can significantly reduce porosity and enhance the uniformity of the particle distribution [²⁸]. For example, investigations on Al7075/SiC composites have shown that optimal stirring conditions lead to a more homogeneous microstructure and improved mechanical performance. Similarly, studies on TiB₂-reinforced Al6061 composites have reported increased ultimate tensile strength and hardness due to the effective dispersion of the reinforcement, as well as a reduction in grain size [²⁸]. These findings underscore the importance of controlling fabrication parameters to overcome the inherent challenges in composite processing. The current research seeks to address several critical gaps in the literature [²⁹]. Although many studies have investigated MMCs based on high-strength alloys such as AA7075 and AA2024, there is a relative paucity of research on more cost-effective matrices like AA8011. In addition, while the benefits of individual reinforcements such as SiC or TiB₂ have been documented, the synergistic effects of combining these reinforcements in a hybrid composite remain underexplored. The existing literature also frequently overlooks comprehensive material characterization, particularly the analysis of reinforcement distribution via techniques such as scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), as well as the evaluation of tribological properties such as wear resistance. These aspects are crucial for ensuring that the improved mechanical properties of the composite translate effectively into industrial applications. This study aims to bridge these gaps by fabricating and characterizing AA8011-based hybrid composites reinforced with both SiC and TiB₂ using the stir casting method. The research will focus on optimizing the processing parameters to achieve a uniform dispersion of the reinforcements, thereby reducing porosity and enhancing the interfacial bonding between the matrix and the ceramic particles. Detailed microstructural analyses will be conducted using SEM and EDS to verify the distribution and integrity of the reinforcements. Mechanical testing, including tensile, flexural, and impact tests, will be employed to assess the performance enhancements imparted by the hybrid reinforcements.

2. MATERIALS AND METHODS

2.1. Material selection

The selection and composition of the reinforcements played a pivotal role in achieving the desired properties of the metal matrix composites (MMCs). Table 1 details the composition ratios of aluminum (Al), titanium diboride (TiB₂), and silicon carbide (SiC) used to fabricate different composite variants. The AA8011 alloy, chosen as the metal matrix, consists primarily of aluminum (Al) (97.3% to 98.9%), with additional elements such as iron (Fe) (0.60% to 1%), silicon (Si) (0.50% to 0.90%), and manganese (Mn) (<0.20%). Other trace elements include zinc (Zn) and copper (Cu) (<0.10%), titanium (Ti) (≤ 0.080%), and chromium (Cr) (≤ 0.050%), with magnesium (Mg) limited to ≤ 0.050%. The total trace element concentration does not exceed 0.15%, ensuring consistency in material properties.

TABLE 1
Reinforcement composition of metal matrix

SAMPLE NUMBER	ALUMINUM (Wt%)	TIB2 QUANTITY (Wt%)	SIC QUANTITY (Wt%)
1	100	0	0
2	98	2	0
3	97	2	1
4	95	2	3
5	93	2	5
6	91	2	7

2.2. Experimental methods

The fabrication process was initiated by selecting AA8011 as the metal matrix, complemented by SiC and TiB₂ as the reinforcing agents (Figure 1). AA8011, in plate form, was procured from a trusted vendor in Bangalore to ensure consistent quality. The meticulous fabrication commenced with carefully melting Aluminum alloy AA8011 in a graphite crucible within a specialized stir casting machine, maintaining a temperature of 800°C to ensure excellent wettability. Magnesium powder was judiciously added to the melt at elevated temperatures to enhance the interaction between the molten matrix and the reinforcing agents. To prepare the SiC and TiB₂ reinforcements, they were pre-heated separately at 350°C for 30 minutes to eliminate any moisture content effectively. The stirring action was initiated at a controlled speed of 600 rpm, employing a stainless-steel stirrer. The gradual addition of the reinforcements commenced as the formation of a vortex within the melt indicated the opportune moment [²⁰]. Reinforcements were added at approximately 1 gm/min, ensuring their uniform distribution within the molten matrix. Continuous stirring for approximately 5 minutes was performed to mix the reinforcements correctly and consistently into the molten matrix. To prevent defects from sudden temperature variations, the molten composite was poured into a pre-heated mold maintained at 480°C. This cautious approach ensured the preservation of the composite’s structural integrity. Subsequently, the samples were allowed to cool gradually within the mold, reaching room temperature before they were carefully removed. This fabrication methodology aimed to yield a homogeneously mixed and strongly bonded composite, taking full advantage of AA8011 as the matrix material and SiC and TiB₂ as the reinforcing agents.

Figure 1
Stir casting setup.

2.3. Tensile test

Tensile tests were conducted using a universal testing machine following ASTM E8 standards [³⁰]. Specimens were precisely machined to standard dimensions, as depicted in Figure 2. The samples were securely positioned in the testing grips, ensuring uniform stress distribution. Tensile loads were applied progressively until failure, allowing the evaluation of mechanical properties such as ultimate tensile strength and elongation.

Figure 2
(a) ASTM E8 standards (Tensile test). (b) Tensile test specimens.

2.4. Hardness test

Hardness measurements were carried out using a Vickers hardness tester, with a 0.25 kg load applied to polished test specimens. The indentation marks, observable under a microscope, provided precise hardness values. The indenter was a square-based diamond pyramid with an angle of 136° between opposing faces, producing a consistent square cross-sectional indentation.

2.5. Impact test

Impact resistance was evaluated using a Charpy impact testing machine in accordance with ASTM E23 standards as shown in Figure 3 [³¹]. Rectangular test specimens with pre-machined notches were prepared for testing. The pendulum hammer (18.75 kg, 825 mm length) was released to strike the specimen at the notch, inducing fracture. The energy absorbed during fracture was recorded, providing insights into the toughness of the composite materials.

Figure 3
(a) ASTM E23 standards (Impact test). (b) Impact test specimens.

2.6. Flexural test

The flexural strength and stiffness of the composites were assessed using a three-point bending test, conducted per ASTM D790 standards (Figure 4) [³²]. A flexural testing machine (Jinan WDW, Model: WDW-50) was used, with specimens positioned on two supports and subjected to a center-applied load. This setup induced bending stress at the midpoint, allowing for a thorough evaluation of flexural properties.

Figure 4
(a) ASTM D790 standards (Flexural test). (b) Flexural test specimens.

3. RESULTS AND DISCUSSION

3.1. XRD analysis

X-ray diffraction (XRD) analysis was conducted on AA8011 aluminum matrix composites using Cu-Kα radiation with a wavelength of approximately 1.54178 Å and a 2θ scanning range from 10° to 70°. The XRD patterns in Figure 5 show the results for the unreinforced sample and composites reinforced with different concentrations of SiC and TiB₂. The unreinforced AA8011 matrix displayed distinct peaks at 38.47°, 44.74°, and 65.13°, corresponding to the (111), (200), and (220) planes of aluminum, in accordance with JCPDS Card No. 04-0787, confirming its crystalline structure. The composites reinforced with 2 wt.% TiB₂ and varying levels of SiC (1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.%) exhibited additional peaks matching those of SiC and TiB₂. Specifically, peaks at 35.6° and 60.5° correspond to SiC (JCPDS 29-1129), while peaks at 27.5° and 48.8° correspond to TiB₂ (JCPDS 35-0753). The intensities of these peaks increased with higher reinforcement content, confirming their successful incorporation. In the composite containing 1 wt.% SiC and 2 wt.% TiB₂, peak analysis confirms the presence of both reinforcements and their homogeneous dispersion within the matrix. At higher SiC concentrations, minor peaks related to Mg₂Si phases were observed, indicating a reaction between magnesium and silicon during solidification. Additionally, the presence of Al₃Ti was detected in the TiB₂-reinforced samples, suggesting the formation of an intermetallic phase due to titanium interaction with the aluminum matrix. These results are consistent with previous works by KUMAR et al. (2022) and SINGH et al. (2021), who reported similar phase formations in aluminum-based hybrid composites [³³, ³⁴].

Figure 5
X-Ray diffraction results.

3.2. Micro vickers hardness (HV)

Figure 6, provides the Micro Vickers hardness test results, offering valuable insights into material hardness. The AA8011 sheet displayed an approximate hardness value of 29.9 HV. In contrast, the casted AA8011 exhibited significantly higher hardness, measuring an average of 62.63 HV. This substantial increase in hardness in the casted material underscores the influence of the casting process on enhancing hardness, potentially due to microstructural changes induced during casting. Introducing 2% TiB₂ into the AA8011 matrix further elevated hardness, yielding an average of 64.7 HV. This result highlights the reinforcing effect of TiB₂ on the composite, contributing to its overall hardness. When 1% SiC was added in combination with 2% TiB₂, the average hardness increased to 66.27 HV. This observation suggests a synergistic effect between SiC and TiB₂, enhancing hardness and emphasizing SiC’s role as a strengthening component within the composite. With varying SiC content (3%, 5%, and 7%), the hardness values exhibited slight fluctuations. This nuanced response indicates a more intricate relationship between SiC content and hardness, hinting at the possibility of an optimal SiC concentration for maximizing hardness. The Micro Vickers hardness results highlight the multifaceted interplay of factors influencing material hardness in these composites. The casting process emerges as a transformative element, significantly enhancing hardness. Meanwhile, TiB₂ is an effective reinforcing agent, contributing to heightened hardness levels. The combined effect of SiC and TiB₂ showcases the potential for synergistic reinforcement, further enhancing hardness [²⁰]. However, the nuanced response to varying SiC content emphasizes the need for meticulous optimization in composite formulation to harness the full potential of these materials.

Figure 6
Vickers hardness chart.

3.3. Tensile test

The tensile test results, displayed in Figure 7, provide critical insights. into the fabricated composites’ mechanical behavior and strength characteristics. This result is pivotal in understanding how the addition of reinforcing agents, TiB2 and SiC, influences the tensile properties of the composites. The base material, AA8011, exhibited an ultimate tensile strength (UTS) of 64.25 MPa. Upon introducing 2% TiB2 into the AA8011 matrix, a marginal increase in UTS was observed, with the composite reaching 65.083 MPa. This initial rise in strength underlines the reinforcing effect of TiB2 on the composite. Further improvements in tensile strength became evident when 1% SiC was incorporated alongside 2% TiB2. The composite achieved a UTS of 67.9 MPa, marking a notable enhancement in mechanical performance. As the SiC content increased to 3%, the UTS continued to rise, reaching 69.33 MPa. This upward trend in strength demonstrated the synergistic effect of SiC and TiB2 in augmenting the tensile properties of the composite. The microstructural observations, as depicted in Figure 9, reveal the distribution of TiB2 and SiC reinforcement materials within the AA8011 matrix. The optical micrographs demonstrate a dendritic-like structure with a uniform dispersion of reinforcement particulates, indicating effective reinforcement throughout the composite material. The composite’s tensile strength further improved as SiC content continued to increase. A UTS of 69.75 MPa was recorded for the composite containing 5% SiC, showcasing the positive impact of higher SiC concentration. However, with 7% SiC, a slight reduction in UTS to 65.58 MPa was observed, suggesting a potential threshold beyond which SiC’s influence on tensile strength diminishes. The tensile test results affirm the critical role played by TiB2 and SiC in enhancing the mechanical properties of the composites. TiB2 initially reinforces the material, while adding SiC leads to a synergistic improvement in tensile strength [²⁰].

Figure 7
Tensile result.

Figure 8
Flexural strength result.

Figure 9
Impact result.

3.4. Flexural test

The flexural test results, presented in Figure 8, offer valuable insights into the fabricated composites’ strength, stiffness, and deformation characteristics. These results are crucial for understanding how adding reinforcing agents, TiB₂ and SiC, affects the flexural properties of the composites. The base material, AA8011, exhibited a flexural strength of 256 MPa, indicating its inherent structural integrity. It registered 166.66 KN-mm in bending stiffness, reflecting its ability to resist deformation. The maximum deflection observed for AA8011 was 7.7 mm. With the incorporation of 2% TiB₂ into the AA8011 matrix, the composite’s flexural strength increased to 268 MPa, reflecting the reinforcing effect of TiB₂ on the material. The bending stiffness also notably improved, reaching 333.33 KN-mm, indicating enhanced resistance to deformation. The maximum deflection was reduced to 4.02 mm, signifying increased rigidity. Adding 1% SiC, in conjunction with 2% TiB₂, further elevated the flexural strength to 284 MPa, highlighting the synergistic effect of SiC and TiB₂ on the composite’s mechanical performance. However, the bending stiffness exhibited a slight decrease to 250 KN-mm. The maximum deflection increased to 5.7 mm, indicating a balance between strength and deformation resistance. As SiC content increased to 3%, the flexural strength rose, reaching 286 MPa, with the bending stiffness returning to 333.33 KN-mm. The maximum deflection increased slightly to 4.41 mm, suggesting an optimal combination of reinforcement materials. The composite with 5% SiC achieved a flexural strength of 293 MPa, with a bending stiffness of 250 KN-mm. The maximum deflection further increased to 5.724 mm, indicating a shift towards enhanced deformation resistance at the expense of bending stiffness. Finally, the composite containing 7% SiC exhibited a flexural strength of 258 MPa, with a bending stiffness of 250 KN-mm. The maximum deflection was recorded at 5.166 mm, suggesting a trade-off between strength and deformation resistance similar to the 5% SiC composite. The flexural test results highlight the influence of TiB₂ and SiC on the mechanical characteristics of the composites. TiB₂ enhances the material’s flexural strength, while SiC, when combined with TiB₂, contributes to a synergistic improvement.

3.5. Impact test

The impact test results, presented graphically depicted in Figure 9, provide crucial insights into the toughness and resistance to fracture of fabricated composite materials. These results are essential for evaluating how reinforcing agents, TiB₂ and SiC, affects the material’s ability to absorb energy during impact. The base material, AA8011, displayed an impact value of 16 J, signifying its inherent ability to withstand impact forces. As reinforcement agents were introduced, changes in the material’s impact resistance became evident. With the addition of 2% TiB₂ to the AA8011 matrix, the composite’s impact value increased to 17 J, indicating improved toughness and energy absorption. This suggests that TiB₂ positively influences the material’s impact performance. Further enhancements in impact resistance were observed with the incorporation of 1% SiC along with 2% TiB₂, resulting in an impact value of 19 J. This indicates a synergistic effect between SiC and TiB₂, contributing to the composite’s increased toughness. As the SiC content increased to 3%, the impact value improved to 20 J. This suggests that a higher concentration of SiC continues to enhance the material’s ability to absorb energy during impact. The composite containing 5% SiC exhibited an impact value of 21 J, signifying a continued positive effect of SiC on impact resistance. However, when the SiC content was raised to 7%, the impact value remained at 20 J, indicating a potential saturation point where further SiC addition does not significantly improve impact performance. The impact test results demonstrate the role of TiB₂ and SiC as effective reinforcement agents in enhancing the composite materials’ toughness and resistance to fracture. TiB₂ alone provides a noticeable improvement, while the combination of TiB₂ and SiC exhibits a synergistic effect, resulting in even more significant impact resistance.

The observed enhancement in mechanical properties, particularly hardness and wear resistance, aligns well with previously published studies. For example, KUMAR et al. (2020) reported a similar increase in microhardness when reinforcing aluminum matrix composites with TiB₂ particles [³⁵]. Likewise, SIVAKUMAR et al. (2021) observed notable improvements in wear resistance when both SiC and TiB₂ were incorporated into aluminum alloys, confirming the synergistic effects of dual reinforcements [³⁶]. The increase in tensile strength in the present study is consistent with findings from RAMESH et al. (2019), where homogeneous dispersion of ceramic particles within the aluminum matrix led to effective grain refinement and improved load-bearing capacity [³⁷]. These comparisons validate that the mechanical performance improvements achieved in this work are in agreement with literature-reported trends for hybrid aluminum composites.

3.6. Wear resistance analysis

The wear resistance of AA8011-based composites reinforced with 2 wt.% TiB₂ and varying SiC contents (1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.%) was evaluated using a pin-on-disc apparatus under dry sliding conditions. The results, as illustrated in Figure 10, indicate a notable improvement in wear resistance with increasing SiC reinforcement content. The unreinforced AA8011 alloy exhibited the highest wear loss due to the absence of hard ceramic phases, which typically provide resistance to material removal under friction. The composite with 2 wt.% TiB₂ and 1 wt.% SiC showed moderate wear resistance, while higher SiC contents significantly reduced wear loss. The lowest wear rate was observed for the composite containing 2 wt.% TiB₂ and 7 wt.% SiC, which can be attributed to enhanced hardness and the uniform distribution of hard ceramic particles that act as barriers against plastic deformation and abrasive wear. These results are consistent with the findings of SIVAKUMAR et al. (2021) and RAVI et al. (2020), who reported that the addition of hybrid ceramic reinforcements to aluminum matrices leads to reduced material loss and improved tribological performance[³⁶, ³⁸]. The wear mechanism shifted from adhesive to abrasive with the addition of reinforcements, further contributing to improved wear resistance.

Figure 10
Wear loss variation of AA8011 matrix composites with 2 wt.% TiB2 and varying SiC contents under dry sliding conditions.

3.7. Microstructural analysis

The microstructure of the as-cast AA8011 aluminum alloy without reinforcement is depicted in Fig. 11 e, showing a uniform base matrix structure without any reinforcement particles. In contrast, Fig. 11 displays SEM micrographs of the 2% TiB₂ + varying SiC concentrations (1%, 3%, 5%, and 7%) reinforced composites, illustrating the successful incorporation and dispersion of ceramic reinforcements within the aluminum matrix. SEM analysis revealed that SiC and TiB₂ particles were well dispersed within the matrix, effectively restricting grain growth during solidification. This refinement led to a more uniform microstructure, improving mechanical properties such as hardness and strength. The homogeneous dispersion of reinforcement particles contributed to enhanced load transfer efficiency and improved resistance to deformation. SEM microscopy confirmed that SiC particles were primarily located in intragranular regions, strengthening the composite and improving mechanical performance. The intragranular dispersion of SiC facilitated better interfacial bonding between the matrix and reinforcements, further contributing to increased mechanical stability. In the case of the 2% TiB₂-reinforced composite (AT-5), some particle agglomeration was observed in both optical and SEM images (Fig. 11). This agglomeration could affect the viscosity and surface tension of the melt, influencing the overall uniformity of the reinforcement distribution. Proper stirring speed during casting is essential to mitigate this issue and promote an even distribution of reinforcement particles. The SEM images also showed that the presence of TiB₂ and SiC particles helped prevent uncontrolled dendrite growth by pushing the reinforcements into the eutectic liquid, leading to stronger matrix-reinforcement bonding. No significant casting defects, such as porosity or inclusions, were detected, indicating that the processing parameters were well optimized to achieve high-quality composites. To complement the SEM observations, EDS analysis was conducted to determine the elemental composition and distribution within the composite. The EDS spectrum revealed prominent peaks for aluminum (Al), validating the primary matrix composition. Strong signals for silicon (Si) and titanium (Ti) confirmed the successful incorporation of SiC and TiB₂ reinforcements. The uniform spatial distribution of these peaks indicated a homogeneous dispersion of reinforcements throughout the matrix. A minor oxygen (O) peak was also detected, likely due to surface oxidation during the stir casting process. These results support the metallurgical bonding observed under SEM and suggest minimal contamination or segregation. Similar findings have been reported in the literature, confirming the reliability of EDS in verifying composite integrity and phase distribution.

Figure 11
Microstructural observations of Stir casted AA8011 with: (a) 2% TiB2 and 1% SiC, (b) 2% TiB2 and 3% SiC (c) 2% TiB2 and 5% SiC (d) 2% TiB2 and 7% SiC (e) unreinforcement.

4. CONCLUSIONS

The comprehensive evaluation of AA8011 with varying percentages of TiB₂ and SiC reinforcements reveals crucial insights into the material’s performance and suitability for various applications.

• The Vickers hardness tests reveal significant improvements in material strength, particularly in compositions with higher percentages of SiC and TiB₂. The AA8011+2% TiB₂ +5% SiC composition exhibits the highest hardness value, highlighting the potential for enhanced material strength.

• Tensile strength results demonstrate a consistent trend, with compositions featuring TiB₂ and SiC reinforcements consistently outperforming the base AA8011 alloy. The AA8011+2% TiB₂ +3% SiC composition stands out with the highest tensile strength among all tested compositions.

• In terms of flexural strength, compositions reinforced with TiB₂ and SiC exhibit notable improvements over the base AA8011 alloy. The AA8011+2% TiB₂ +3% SiC composition demonstrates the highest flexural strength, indicating its suitability for applications requiring enhanced bending resistance.

• Impact resistance measurements confirm that all compositions with TiB₂ and SiC reinforcements perform better than the base AA8011 alloy. The AA8011+2% TiB₂ +3% SiC composition exhibits the highest impact resistance, suggesting its potential for applications demanding superior resistance to sudden loads.

• X-ray diffraction (XRD) analysis confirms the successful incorporation of TiB₂ and SiC reinforcements, with distinct peaks for aluminum, SiC, and TiB₂. Higher reinforcement concentrations lead to increased peak intensity, indicating improved crystallinity and uniform distribution of phases. The presence of Mg₂Si and Al₃Ti in higher SiC concentrations suggests possible intermetallic phase formation, which can influence mechanical properties.

• Scanning electron microscopy (SEM) analysis reveals a uniform distribution of TiB₂ and SiC particles within the matrix, leading to refined grain structures and improved mechanical properties. The reinforcement particles effectively hinder grain growth, enhancing the composite’s hardness and strength. However, minor agglomeration is observed at higher reinforcement concentrations, which could impact mechanical performance if not adequately controlled during processing.

5. BIBLIOGRAPHY

• ^[1] RAO, R.N., DAS, S., “Effect of SiC content and sliding speed on the wear behaviour of aluminium matrix composites”, Materials & Design, v. 32, n. 2, pp. 1066–1071, 2011. doi: http://doi.org/10.1016/j.matdes.2010.06.047.
  » https://doi.org/10.1016/j.matdes.2010.06.047
• ^[2] UVARAJA, V.C., NATARAJAN, N., SIVAKUMAR, K., et al, “Tribological behavior of heat treated Al 7075 aluminium metal matrix composites”, Indian Journal of Engineering and Materials Sciences, v. 22, pp. 51–61, 2015.
• ^[3] RAO, T.B., “An experimental investigation on mechanical and wear properties of Al7075/SiCp composites: effect of SiC content and particle size”, Journal of Tribology, v. 140, n. 3, pp. 031601, 2018. doi: http://doi.org/10.1115/1.4037845.
  » https://doi.org/10.1115/1.4037845
• ^[4] KUMAR, N., GAUTAM, G., GAUTAM, R.K., et al, “Synthesis and characterization of TiB2 reinforced aluminium matrix composites: a review”, Journal of The Institution of Engineers (India): Series D, v. 97, n. 2, pp. 233–253, 2016. doi: http://doi.org/10.1007/s40033-015-0091-7.
  » https://doi.org/10.1007/s40033-015-0091-7
• ^[5] JAMES, S.J., VENKATESAN, K., KUPPAN, P., et al, “Hybrid aluminium metal matrix composite reinforced with SiC and TiB2”, Procedia Engineering, v. 97, pp. 1018–1026, 2014. doi: http://doi.org/10.1016/j.proeng.2014.12.379.
  » https://doi.org/10.1016/j.proeng.2014.12.379
• ^[6] KAUSHIK, N., SINGHAL, S., “Hybrid combination of Taguchi-GRA-PCA for optimization of wear behavior in AA6063/SiCp matrix composite”, Production & Manufacturing Research, v. 6, n. 1, pp. 171–189, 2018. doi: http://doi.org/10.1080/21693277.2018.1479666.
  » https://doi.org/10.1080/21693277.2018.1479666
• ^[7] YADAV, P.K., DIXIT, G., “Erosive-corrosive wear of aluminium-silicon matrix (AA336) and SiCp/TiB2p ceramic composites”, Silicon, v. 11, n. 3, pp. 1649–1660, 2019. doi: http://doi.org/10.1007/s12633-018-9981-2.
  » https://doi.org/10.1007/s12633-018-9981-2
• ^[8] LIU, X., LIU, Y., HUANG, D., et al, “Tailoring in-situ TiB2 particulates in aluminum matrix composites”, Materials Science and Engineering A, v. 705, pp. 55–61, 2017. doi: http://doi.org/10.1016/j.msea.2017.08.047.
  » https://doi.org/10.1016/j.msea.2017.08.047
• ^[9] RAMABALAN, S., RAJAN, H.M., DINAHARAN, I., et al, “Experimental investigation of MRR on in situ formed AA7075/TiB2 cast composites machining by wire EDM”, International Journal of Machining and Machinability of Materials, v. 17, n. 3, pp. 295–318. doi: http://doi.org/10.1504/IJMMM.2015.072001.
  » https://doi.org/10.1504/IJMMM.2015.072001
• ^[10] ARAB, M.S., MAHALLAWY, N., SHEHATA, F., et al, “Refining SiCp in reinforced Al–SiC composites using equal-channel angular pressing”, Materials & Design, v. 64, pp. 280–286, 2014. doi: http://doi.org/10.1016/j.matdes.2014.07.045.
  » https://doi.org/10.1016/j.matdes.2014.07.045
• ^[11] SAHIN, Y., “Preparation and some properties of SiC particle reinforced aluminium alloy composites”, Materials & Design, v. 24, n. 8, pp. 671–679, 2003. doi: http://doi.org/10.1016/S0261-3069(03)00156-0.
  » https://doi.org/10.1016/S0261-3069(03)00156-0
• ^[12] BANDHU, D., THAKUR, A., PUROHIT, R., et al, “Characterization & evaluation of Al7075 MMCs reinforced with ceramic particulates and influence of age hardening on their tensile behavior”, Journal of Mechanical Science and Technology, v. 32, n. 7, pp. 3123–3128, 2018. doi: http://doi.org/10.1007/s12206-018-0615-9.
  » https://doi.org/10.1007/s12206-018-0615-9
• ^[13] SINGH, G., CHAN, S.L.I., SHARMA, N., “Parametric study on the dry sliding wear behaviour of AA6082–T6/TiB2 in situ composites using response surface methodology”, Journal of the Brazilian Society of Mechanical Sciences and Engineering, v. 40, n. 6, pp. 310, 2018. doi: http://doi.org/10.1007/s40430-018-1235-0.
  » https://doi.org/10.1007/s40430-018-1235-0
• ^[14] PORIA, S., SAHOO, P., SUTRADHAR, G., “Tribological characterization of stir-cast aluminium-TiB2 metal matrix composites”, Silicon., v. 8, n. 4, pp. 591–599, 2016. doi: http://doi.org/10.1007/s12633-016-9437-5.
  » https://doi.org/10.1007/s12633-016-9437-5
• ^[15] RUI-SONG, J., WEN-HU, W., GUO-DONG, S., et al, “Experimental investigation on machinability of in situ formed TiB2 particles reinforced Al MMCs”, Journal of Manufacturing Processes, v. 23, pp. 249–257, 2016. doi: http://doi.org/10.1016/j.jmapro.2016.05.004.
  » https://doi.org/10.1016/j.jmapro.2016.05.004
• ^[16] KUMARESAN, G., ARUL KUMAR, B., “Investigations on mechanical properties of micro- and nano-particulates (Al2O3/B4C) reinforced in Al7075 matrix composite”, International Journal of Metalcasting, v. 16, pp. 1932–1939, 2022. doi: http://doi.org/10.1007/s40962-021-00741-1.
  » https://doi.org/10.1007/s40962-021-00741-1
• ^[17] JAYAKUMAR, E., PRAVEEN, A.P., RAJAN, T.P.D., et al, “Studies on tribological characteristics of centrifugally Cast SiCp-Reinforced Functionally Graded A319 aluminium matrix composites”, Transactions of the Indian Institute of Metals, v. 71, n. 11, pp. 2741–2748, 2018. doi: http://doi.org/10.1007/s12666-018-1442-5.
  » https://doi.org/10.1007/s12666-018-1442-5
• ^[18] BINDUMADHAVAN, P.N., CHIA, T.K., CHANDRASEKARAN, M., et al, “Effect of particle-porosity clusters on tribological behavior of cast aluminum alloy A356-SiCp metal matrix composites”, Materials Science and Engineering A, v. 315, n. 1–2, pp. 217–226, 2001. doi: http://doi.org/10.1016/S0921-5093(00)01989-4.
  » https://doi.org/10.1016/S0921-5093(00)01989-4
• ^[19] AMIRKHANLOU, S., NIROUMAND, B., “Effects of reinforcement distribution on low and high temperature tensile properties of Al356/SiCp cast composites produced by a novel reinforcement dispersion technique”, Materials Science and Engineering A, v. 528, n. 24, pp. 7186–7195, 2011. doi: http://doi.org/10.1016/j.msea.2011.06.013.
  » https://doi.org/10.1016/j.msea.2011.06.013
• ^[20] GEIGER, A.L., WALKER, J.A., “The processing and properties of discontinuously reinforced aluminum composites”, The Journal of the Minerals, Metals & Materials Society (TMS), v. 43, pp. 8–15, 1991. doi: https://doi.org/10.1007/BF03221097.
  » https://doi.org/10.1007/BF03221097
• ^[21] KALAISELVAN, K., MURUGAN, N., PARAMESWARAN, S., “Production and characterization of AA6061-B4C stir cast composite”, Materials & Design, v. 32, n. 7, pp. 4004–4009, 2011. doi: http://doi.org/10.1016/j.matdes.2011.03.018.
  » https://doi.org/10.1016/j.matdes.2011.03.018
• ^[22] PAZHOUHANFAR, Y., EGHBALI, B., “Microstructural characterization and mechanical properties of TiB2 reinforced Al6061 matrix composites produced using stir casting process”, Materials Science and Engineering A, v. 710, pp. 172–180, 2018. doi: http://doi.org/10.1016/j.msea.2017.10.087.
  » https://doi.org/10.1016/j.msea.2017.10.087
• ^[23] AKBARI, M.K., BAHARVANDI, H.R., SHIRVANIMOGHADDAM, K., “Tensile and fracture behavior of nano/micro TiB2 particle reinforced casting A356 aluminum alloy composites”, Materials & Design, v. 66, pp. 150–161, 2015. doi: http://doi.org/10.1016/j.matdes.2014.10.048.
  » https://doi.org/10.1016/j.matdes.2014.10.048
• ^[24] JIANG, J., WANG, Y., “Microstructure and mechanical properties of the semisolid slurries and rheoformed component of nano-sized SiC/7075 aluminum matrix composite prepared by ultrasonic-assisted semisolid stirring”, Materials Science and Engineering A, v. 639, pp. 350–358, 2015. doi: http://doi.org/10.1016/j.msea.2015.04.064.
  » https://doi.org/10.1016/j.msea.2015.04.064
• ^[25] HAMEDAN, A.D., SHAHMIRI, M., “Production of A356–1 wt% SiC nanocomposite by the modified stir casting method”, Materials Science and Engineering A, v. 556, pp. 921–926, 2012. doi: http://doi.org/10.1016/j.msea.2012.07.093.
  » https://doi.org/10.1016/j.msea.2012.07.093
• ^[26] FAISAL, N., KUMAR, K., “Mechanical and tribological behaviour of nano scaled silicon carbide reinforced aluminium composites”, Journal of Experimental Nanoscience, v. 13, n. sup1, pp. S1–S13, 2018. doi: http://doi.org/10.1080/17458080.2018.1431846.
  » https://doi.org/10.1080/17458080.2018.1431846
• ^[27] METI, V.K.V., SHIRUR, S., NAMPOOTHIRI, J., et al, “Synthesis, characterization and mechanical properties of AA7075 based MMCs reinforced With TiB2 particles processed through ultrasound assisted in-situ casting technique”, Transactions of the Indian Institute of Metals, v. 71, n. 4, pp. 841–848, 2018. doi: http://doi.org/10.1007/s12666-017-1216-5.
  » https://doi.org/10.1007/s12666-017-1216-5
• ^[28] EGIZABAL, P., GARCÍA DE CORTÁZAR, M., TORREGARAY, A., et al, “Analysis of the solidification and microstructure of two Aluminium alloys reinforced with TiB2 particles”, Advanced Engineering Materials, v. 13, n. 9, pp. 887–894, 2011. doi: http://doi.org/10.1002/adem.201100040.
  » https://doi.org/10.1002/adem.201100040
• ^[29] SELVARASU, S., SUBRAMANIAN, M., THANGASAMY, J., “An effect of nano-SiC with different dielectric mediums on AZ61/7.5% B₄C nanocomposites studied through electrical discharge machining and Taguchi based complex proportional assessment method”, Matéria (Rio de Janeiro), v. 28, n. 2, pp. e20230058, 2023. doi: http://doi.org/10.1590/1517-7076-rmat-2023-0058.
  » https://doi.org/10.1590/1517-7076-rmat-2023-0058
• ^[30] AMERICAN SOCIETY FOR TESTING AND MATERIALS, ASTM E8/E8M Standard Test Methods for Tension Testing of Metallic Materials, West Conshohocken, ASTM, 2024.
• ^[31] AMERICAN SOCIETY FOR TESTING AND MATERIALS, ASTM E23 Standard Test Methods for Notched Bar Impact Testing of Metallic Materials, West Conshohocken, ASTM, 2024.
• ^[32] AMERICAN SOCIETY FOR TESTING AND MATERIALS, ASTM D790 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials, West Conshohocken, ASTM, 2024.
• ^[33] KUMAR, N., GAUTAM, G., GAUTAM, R.K., et al., “Synthesis and characterization of TiB₂ reinforced aluminium matrix composites: a review”, Journal of The Institution of Engineers (India): Series D, 97(2), pp. 233–253, 2016. doi: http://doi.org/10.1007/s40033-015-0091-7.
  » https://doi.org/10.1007/s40033-015-0091-7
• ^[34] SINGH, G., CHAN, S.L.I., SHARMA, N., “Parametric study on the dry sliding wear behaviour of AA6082–T6/TiB₂ in situ composites using response surface methodology”, Journal of the Brazilian Society of Mechanical Sciences and Engineering, 40(6), p. 310, 2018. doi: http://doi.org/10.1007/s40430-018-1235-0.
  » https://doi.org/10.1007/s40430-018-1235-0
• ^[35] KUMAR, R., JHA, P.K., PRASAD, R., “Effect of TiB₂ on the mechanical and tribological properties of aluminum alloy 5052 matrix alloy”, Materials Today: Proceedings, 2024. doi: https://doi.org/10.1016/j.matpr.2024.03.123.
  » https://doi.org/10.1016/j.matpr.2024.03.123
• ^[36] SIVAKUMAR, K., VENKATESHWARAN, N., SIVARAJ, P., KANNAN, T.S., “Wear behaviour of aluminium metal matrix hybrid composites with SiC and TiB₂”, Materials Today: Proceedings, 47(12), pp. 3794–3799, 2021. doi: https://doi.org/10.1016/j.matpr.2021.04.248.
  » https://doi.org/10.1016/j.matpr.2021.04.248
• ^[37] RAMESH, T., RAMNATH, B.V., ELANCHEZHIAN, C., “Fabrication and characterization of aluminium metal matrix composites reinforced with ceramic particles”, Materials Today: Proceedings, 16, pp. 994–1000, 2019. doi: https://doi.org/10.1016/j.matpr.2019.06.173.
  » https://doi.org/10.1016/j.matpr.2019.06.173
• ^[38] RAVI, B., “Fabrication and Mechanical Properties of Al7075-SiC-TiC Hybrid Metal Matrix Composites”, International Journal of Engineering Science Invention, 6(10), pp. 12–19, 2017.

Publication Dates

• Publication in this collection
  16 May 2025
• Date of issue
  2025

History

• Received
  10 Dec 2024
• Accepted
  09 Apr 2025