1.0 Introduction
1.1 Background of Study
In the modern era of engineering materials, there is a continuous demand for materials that exhibit superior mechanical performance, high strength-to-weight ratios, excellent wear resistance, and enhanced thermal stability. Conventional monolithic materials such as pure metals or alloys often fail to meet these complex requirements in high-performance applications such as aerospace, automotive, and defense industries. To bridge this performance gap, the development of metal matrix composites (MMCs) has become a major area of materials research and development (Callister et al., 2014).
According to Surappa (2003), aluminum metal matrix composites (Al-MMCs) have emerged as a prominent class of MMCs due to aluminum’s lightweight, corrosion resistance, and good machinability. However, aluminum alone may lack the required strength and wear resistance needed for high-performance applications. This has led to the reinforcement of aluminum with ceramic particles such as silicon carbide (SiC) to form composites that offer enhanced mechanical properties (Surappa, 2003). Silicon Carbide is particularly attractive due to its high hardness, thermal conductivity, and compatibility with the aluminum matrix, making it a commonly used reinforcement in Al-MMCs (Ravindran et al., 2013).
The weight percentage of silicon carbide plays a critical role in determining the effectiveness of reinforcement. Studies have shown that increasing the SiC content in the composite generally improves mechanical properties such as hardness, tensile strength, and wear resistance. However, higher weight fractions may also lead to challenges such as poor ductility, increased porosity, and difficulties in uniform distribution of the reinforcing particles (Kumar et al., 2016). Previous research has also indicated that the method of fabrication, particle size of the reinforcement, and processing conditions significantly influence the final properties of the composite (Prasad & Asthana, 2004). Among various fabrication techniques, stir casting is one of the most economical and widely used methods for preparing Al-SiC composites due to its simplicity and adaptability for mass production (Rajan et al., 2007).
Callister et al. (2014) stated that, a metal matrix composite (MMC) is a composite material in which a metal or alloy matrix is reinforced with another material typically ceramic or another metal to enhance its mechanical and physical properties (Callister & Rethwisch, 2014). One of the most widely studied and utilized forms of MMCs is the aluminum metal matrix composite (Al-MMC) due to aluminum’s low density, excellent corrosion resistance, and good thermal and electrical conductivity (Prasad & Asthana, 2004). The reinforcement materials are often ceramic particles such as silicon carbide (SiC), alumina (Al₂O₃), or boron carbide (B₄C), which provide improved mechanical strength, stiffness, wear resistance, and thermal stability to the matrix (Kumar et al., 2016). Among the different reinforcement materials, silicon carbide (SiC) is particularly popular because of its high hardness, high thermal conductivity, and excellent compatibility with aluminum matrices. The addition of SiC to aluminum significantly alters the mechanical properties of the composite, such as tensile strength, hardness, impact resistance, and wear behavior (Ravindran et al., 2013). However, the effect of the reinforcement is not uniform and largely depends on the weight percentage of SiC added to the aluminum matrix. Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the effect of weight percentage of silicon carbide on mechanical behavior of aluminum metal matrix composite.
1.2 Statement of Problems
Investigation revealed that the continuous quest for advanced engineering materials, aluminum metal matrix composites (Al-MMCs) reinforced with ceramic particles like silicon carbide (SiC) have gained significant attention (Surappa, 2003). The variation in SiC content is known to influence different mechanical behaviors such as tensile strength, hardness, ductility, and impact resistance. While an increase in SiC content typically leads to improved hardness and tensile strength, it often results in reduced ductility and increased brittleness (Ravindran et al., 2013). Inappropriate weight percentages of SiC also lead to problems such as particle agglomeration, poor interfacial bonding, and non-uniform distribution, which adversely affect the overall mechanical behavior of the composite (Kumar et al., 2016).
Furthermore, fabrication challenges such as porosity formation and inadequate wetting between the matrix and reinforcement are directly linked to the chosen reinforcement percentage (Rajan et al., 2007). The lack of a clearly defined standard for SiC weight percentage in Al-MMCs across different industries highlights the need for a focused investigation into how varying weight percentages affect mechanical properties. It is against the backdrop that this study seeks to explore how varying the weight percentage of SiC affects the mechanical behavior of aluminum-based composites.
1.3 Aim and Objectives of Study
This study aims to determine how different weight percentages of silicon carbide reinforcement alter the mechanical behavior of aluminum metal matrix composites. In achieving this aim, the following specific objectives were laid out as follows to:
- Investigate how selected SiC weight percentages affect key mechanical properties such as tensile strength, hardness, impact toughness, and elastic modulus.
- Characterize microstructural features including particle distribution, interfacial bonding, and porosity using optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS).
- Evaluate wear resistance at each reinforcement level through standardized pin-on-disc tests and correlate the results with microstructural observations.
- Develop empirical models or statistical correlations linking SiC weight fraction to measured mechanical properties, enabling performance prediction beyond the tested compositions.
- Identify the SiC weight-percentage window that delivers the most advantageous combination of mechanical performance and manufacturability, and propose practical processing guidelines for industry adoption.
1.4 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- How do varying weight percentages of silicon carbide influence the tensile strength, hardness, impact toughness, and elastic modulus of aluminum metal matrix composites?
- What microstructural changes occur in the aluminum matrix composite as the silicon carbide content increases, and how do these changes affect mechanical behavior?
- How does the wear resistance of aluminum metal matrix composites vary with different silicon carbide reinforcement levels?
- Is there a statistically significant correlation between silicon carbide weight percentage and the mechanical properties of the composite?
- What is the optimal weight percentage of silicon carbide that achieves a balance between enhanced mechanical performance and ease of fabrication?
1.5 Significance of Study
The outcome of this research will help researchers and engineers understand the trade-offs between strength, hardness, and ductility when adjusting the SiC content. The findings will assist in identifying the most effective SiC weight percentage that enhances performance while maintaining the workability and structural integrity of the composite.
The study will also contribute to the development of more reliable and cost-effective aluminum-based composites for critical applications in the aerospace, automotive, and structural engineering industries.
Furthermore, this research will guide academic researchers and students by expanding the body of knowledge in composite material science and providing a strong foundation for further research and innovation in reinforcement strategies.
1.6 Scope of Study
This study focuses on investigating the effect of varying weight percentages of silicon carbide on the mechanical behavior of aluminum metal matrix composites fabricated within Lagos State, Nigeria. The research will specifically examine composites produced using locally sourced aluminum alloys and silicon carbide particles, employing stir casting methods available in manufacturing facilities within the state.
1.7 Limitations of the Study
The study was limited by the availability of high-purity silicon carbide and aluminum alloy materials within the local market, which affected the consistency of the composite samples produced. The fabrication process was also restricted to stir casting due to the limited access to advanced manufacturing techniques such as powder metallurgy or squeeze casting in the selected laboratories.
Furthermore, testing equipment and facilities available in Lagos State were not always capable of conducting comprehensive mechanical and microstructural analyses, which constrained the depth of characterization. Environmental conditions such as temperature and humidity fluctuations during sample preparation and testing were not fully controlled, potentially influencing the results.
Lastly, the study was focused solely on the mechanical behavior of the composites, leaving other important properties such as corrosion resistance and thermal performance unexplored.
1.8 Definition of Terms
Aluminum Metal Matrix Composite (Al-MMC): A composite material consisting of an aluminum alloy matrix reinforced with ceramic or metallic particles, designed to enhance mechanical properties such as strength, hardness, and wear resistance. Al-MMCs are widely used in aerospace and automotive industries due to their lightweight and superior performance (Surappa, 2003).
Silicon Carbide (SiC): A hard ceramic material used as a reinforcement in metal matrix composites to improve mechanical properties. SiC particles increase the composite’s strength, hardness, and thermal stability but may affect ductility depending on their concentration (Ravindran et al., 2013).
Weight Percentage: The proportion of silicon carbide particles added to the aluminum matrix expressed as a percentage of the total composite weight. This measure is critical as it influences the overall mechanical behavior of the composite material (Kumar et al., 2016).
Mechanical Behavior: Refers to how a material responds to external forces, including properties such as tensile strength, hardness, impact resistance, and wear resistance. Understanding mechanical behavior is essential to tailor composites for specific engineering applications (Rajan et al., 2007).
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