Development and Characterization of Aluminium Metal Matrix Composite Reinforced with Fly Ash: A Sustainable Approach

Abstract

With the increasing demand for light, strong, and eco-friendly materials in engineering, there has been much research conducted on aluminium metal matrix composites (AMMCs). Aluminium-based composite materials reinforced with industrial waste materials have the advantage of being both eco-friendly and having improved material properties. Fly ash, which is produced from the burning of coal in thermal power plants, is rich in silica and other ceramic materials that can act as particulate reinforcement of aluminium matrix. The present study focuses on the development and characterization of aluminium–fly ash metal matrix composites with particular emphasis on the relationship between fly ash reinforcement and the resulting physical, mechanical, microstructural, and tribological properties. The composite material is developed through a powder metallurgy route involving powder blending, compaction, and sintering. The various levels of fly ash reinforcements will be taken into consideration to understand the effect of fly ash reinforcements on the properties such as density, impact strength, hardness, tensile strength, microstructure, and wear characteristics. The possible reasons that are expected to result in property improvement are the refining of grains, load transfer, dispersion strengthening, and presence of hard ceramic particles inside the aluminum matrix. However, at higher levels of reinforcement, particle agglomeration, high porosity, and weak interface bonding can lead to a decrease in strength and ductility of the composite. This paper reveals the capability of fly ash to be used as a sustainable reinforcement in aluminium-based metal matrix composites and a way to convert industrial waste into engineering materials.

Introduction

The text discusses the development of aluminium metal matrix composites (AMMCs) reinforced with fly ash to produce lightweight, strong, hard, and wear-resistant materials for applications such as automotive, aerospace, marine, defence, and other engineering fields.

Background

Aluminium is widely used because it has low density, good corrosion resistance, good machinability, and a high strength-to-weight ratio. However, conventional aluminium alloys have relatively low hardness, strength, and wear resistance. Adding hard ceramic reinforcement can improve these properties.

Common reinforcements include SiC, Al?O?, B?C, TiC, and graphite, but their high cost encourages the use of inexpensive waste materials. Fly ash, a waste product from coal-fired power plants, is particularly attractive because it is abundant, inexpensive, and contains hard ceramic compounds such as silica (SiO?) and alumina (Al?O?). Using fly ash also helps reduce environmental problems caused by its disposal.

Literature Review

Previous research shows that waste materials such as rice husk ash and fly ash can improve the mechanical and tribological properties of aluminium composites. However, excessive reinforcement may cause particle clustering and reduce properties such as tensile strength.

Several manufacturing methods can be used, including:

• Stir casting
• Squeeze casting
• Friction stir processing
• Powder metallurgy

The study focuses on powder metallurgy because it provides better control over reinforcement content and particle distribution and avoids some wetting problems associated with liquid-metal processing.

Materials and Method

The composite uses:

• Aluminium powder as the matrix.
• Fly ash as the reinforcement.

Five compositions were prepared:

The manufacturing process consists of weighing, powder mixing, compaction, sintering, cooling, specimen preparation, and characterization.

Main Results

1. Density:
Increasing fly ash reduced the composite density from 2.70 g/cm³ for A1 to 2.56 g/cm³ for A5, a reduction of about 5.19%. This confirms that fly ash can help produce lighter aluminium composites.

2. Hardness:
Hardness increased continuously with fly ash content, from 48 BHN for A1 to 68 BHN for A5. This represents an improvement of approximately 41.67%. The hard ceramic particles strengthen the aluminium matrix and restrict deformation.

3. Tensile Strength:
Tensile strength increased from 120 MPa for A1 to a maximum of 141 MPa for A4 (7% fly ash), representing a 17.5% improvement. At 10% fly ash, tensile strength decreased slightly to 138 MPa, suggesting that excessive reinforcement may cause particle clustering or defects.

4. Impact Strength:
Impact strength decreased as fly ash content increased, from 8.5 J for A1 to 6.5 J for A5. The reduction is attributed to the brittle nature of fly ash particles, which can act as stress-concentration and crack-initiation sites.

5. Wear Resistance:
The available results indicate that adding fly ash reduces the wear rate. For example, the wear rate decreased from 8.50 × 10?? mm³/N·m for A1 to 6.10 × 10?? mm³/N·m for A3 (5% fly ash), corresponding to approximately 28.24% reduction.

Conclusion

The present study investigates the development and characterization of sustainable aluminium metal matrix composites reinforced with fly ash using a powder metallurgy approach. Based on the experimental methodology and the established behaviour of aluminium–fly ash composites, the following conclusions can be drawn after validation with the experimental data: 1) Aluminium–fly ash metal matrix composites can be successfully developed through powder metallurgy by controlled powder mixing, compaction, and sintering. 2) The incorporation of fly ash provides a promising route for utilizing industrial waste as a low-cost particulate reinforcement. 3) Increasing fly ash content is expected to reduce the density of the composite, making the material potentially attractive for lightweight engineering applications. 4) The presence of hard ceramic constituents in fly ash can improve the hardness and wear resistance of the aluminium matrix when an optimum reinforcement concentration is used. 5) The microstructural distribution of fly ash particles plays a critical role in determining the final mechanical and tribological properties of the composite.

References

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Copyright

Copyright © 2026 Dibyendu Mondal, Soumya Mukherjee, Aaharit Dasgupta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.