Effects of Process Parameters on Scrap Aluminum–RHA Composites: Advancing Sustainable Evaporative Pattern Casting Technology

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The growing demand for lightweight, durable, and environmentally sustainable engineering materials has accelerated research into aluminum matrix composites reinforced with agricultural waste. One promising approach is the utilization of rice husk ash (RHA), an abundant silica-rich by-product, as a reinforcing material in recycled aluminum composites. The reviewed study investigates how pouring temperature, aluminum–RHA composition, and styrofoam pattern thickness influence the physical and mechanical properties of scrap aluminum composites fabricated using evaporative pattern casting (EPC). By combining recycled aluminum with agricultural waste, the research demonstrates an environmentally responsible manufacturing strategy while providing valuable insights into optimizing casting parameters for improved hardness, surface quality, porosity control, and casting fluidity. This work contributes to the development of sustainable metal matrix composite manufacturing for future engineering applications.

Bibliographic Information

Item Information
Article Title Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites
Authors Rudi Siswanto; Abdul Ghofur; Rachmat Subagyo; Mastiadi Tamjidillah; Mahmud; Ma’ruf; Adi Nordiman
Journal Teknomekanik
Volume & Issue Volume 9, Issue 1
Publication Date February 2026
Pages 91–109
DOI https://doi.org/10.24036/teknomekanik.v9i1.46072
Publisher Universitas Negeri Padang
License Creative Commons Attribution 4.0 International (CC BY 4.0)
ISSN (Online) 2621-8720
ISSN (Print) 2621-9980
Keywords evaporative casting; Al-RHA composite; pouring temperature; pattern thickness; physical-mechanical properties

1. Research Background

  • The demand for sustainable lightweight materials continues to increase. Modern engineering sectors—including automotive, aerospace, agriculture, and transportation—require materials that combine low weight, excellent mechanical properties, corrosion resistance, and cost efficiency. Aluminum matrix composites (AMCs) have become attractive candidates because of their favorable strength-to-weight ratio.
  • Agricultural waste has emerged as an environmentally friendly reinforcement material. Rice husk ash (RHA), which contains a high concentration of silica, offers an economical and sustainable alternative to conventional ceramic reinforcements. Utilizing RHA not only enhances composite performance but also reduces agricultural waste disposal.
  • Scrap aluminum supports circular manufacturing. Instead of relying on primary aluminum production, recycled aluminum provides substantial environmental and economic advantages by reducing energy consumption, production costs, and dependence on virgin raw materials while promoting circular economy principles.
  • Evaporative Pattern Casting (EPC) offers unique manufacturing advantages. Unlike conventional casting methods, EPC enables the production of complex geometries with fewer finishing operations because expendable polystyrene patterns vaporize during molten metal filling. Nevertheless, the quality of the final casting is highly sensitive to processing conditions.
  • Previous studies have rarely investigated the combined influence of critical EPC parameters. Most existing aluminum–RHA composite research has focused on stir casting or powder metallurgy using primary aluminum. Limited attention has been given to scrap aluminum composites produced through evaporative pattern casting while simultaneously evaluating pouring temperature, reinforcement ratio, and pattern thickness.
  • The study addresses this research gap. The authors systematically investigate how process parameters affect surface roughness, hardness, porosity, and fluidity, providing a comprehensive understanding of process optimization for sustainable aluminum composite manufacturing.
  • The novelty lies in integrating recycled materials, agricultural waste, and EPC technology. By combining scrap aluminum, rice husk ash reinforcement, and evaporative pattern casting, the study introduces a sustainable manufacturing approach capable of improving mechanical performance while reducing environmental impact.

2. Research Objective

  • To fabricate aluminum matrix composites reinforced with rice husk ash using scrap aluminum through the evaporative pattern casting process.
  • To investigate the influence of pouring temperature (650°C, 700°C, and 750°C) on the physical and mechanical characteristics of Al–RHA composites.
  • To evaluate the effects of different aluminum–rice husk ash composition ratios (70:30, 65:35, and 60:40) on hardness, porosity, surface roughness, and fluidity.
  • To examine how variations in styrofoam pattern thickness influence dimensional quality and casting surface characteristics during evaporative pattern casting.
  • To determine an optimal combination of process parameters capable of producing aluminum composites with balanced mechanical performance and casting quality while utilizing recycled materials.

3. Why This Research Matters

  • Promotes sustainable manufacturing. The study demonstrates how recycled aluminum and agricultural waste can be transformed into high-value engineering materials, supporting resource efficiency and waste reduction.
  • Advances aluminum composite technology. Understanding the interactions among pouring temperature, reinforcement ratio, and pattern thickness provides valuable knowledge for optimizing evaporative pattern casting processes.
  • Supports circular economy initiatives. Reusing scrap aluminum while valorizing rice husk ash contributes to environmentally responsible manufacturing practices with reduced dependence on virgin materials.
  • Improves casting quality. Identifying suitable processing conditions enables manufacturers to produce composites with improved hardness, acceptable porosity, enhanced fluidity, and better surface finish.
  • Provides practical guidance for manufacturing engineers. The findings offer experimentally validated information that can assist foundries and materials engineers in selecting process parameters for producing aluminum matrix composites using evaporative pattern casting.
  • Expands knowledge on evaporative pattern casting. The research broadens current understanding of EPC by systematically evaluating multiple interacting process variables rather than focusing on a single manufacturing parameter.
  • Supports future development of eco-friendly engineering materials. The successful integration of recycled aluminum with rice husk ash reinforces the potential of biomass-derived reinforcements in next-generation sustainable composite manufacturing.

4. Research Methodology

  • Research Design

    The study employed an experimental factorial design to investigate the combined effects of three major evaporative pattern casting (EPC) parameters on the physical and mechanical properties of aluminum matrix composites reinforced with rice husk ash (RHA). The experimental approach enabled the researchers to evaluate not only the individual influence of each parameter but also their interactions in determining composite quality.

  • Raw Materials

    The matrix material consisted of recycled scrap aluminum obtained from discarded low-voltage aerial bundled electrical cables. Rice husk ash (RHA) served as the reinforcing material after undergoing a two-stage combustion process. Initially, rice husks were burned in open air at approximately 400°C before being ground and sieved through a 200-mesh screen. The ash was subsequently heated in a furnace at 900°C for two hours to obtain high-silica white ash suitable for composite reinforcement. Local silica sand (Palangka sand) was used as the molding material, while discarded Styrofoam packaging was fabricated into expendable casting patterns.

  • Composite Fabrication

    The composites were produced using the evaporative pattern casting method. Styrofoam patterns were embedded in dry silica sand before molten scrap aluminum was prepared in a crucible furnace. Rice husk ash was gradually introduced into the molten aluminum and continuously stirred at 150 rpm for two minutes to promote homogeneous particle distribution. The molten composite was then poured directly into the mold, where the Styrofoam pattern vaporized and was replaced by the molten metal. After approximately thirty minutes of solidification, the cast specimens were removed, cleaned, and prepared for characterization.

  • Experimental Variables

    Three independent variables were systematically investigated:

    • Pouring temperature: 650°C, 700°C, and 750°C.
    • Aluminum–RHA composition ratio: 70:30, 65:35, and 60:40 (wt.%).
    • Styrofoam pattern thickness: 1, 2, 3, 4, 5, 6, and 10 mm.

    The selected ranges enabled comprehensive evaluation of the principal process variables affecting evaporative pattern casting performance.

  • Material Characterization

    Prior to fabrication, both scrap aluminum and rice husk ash were characterized using Energy Dispersive X-ray Spectroscopy (EDX) to determine their elemental compositions. Scrap aluminum primarily consisted of aluminum with minor oxygen and iron, whereas rice husk ash exhibited a high silica content suitable for reinforcement. Silica sand was also characterized to confirm its chemical stability for mold preparation.

  • Performance Evaluation

    The fabricated composites were evaluated using four primary response variables:

    • Surface Roughness measured with a surface profilometer according to ASTM D441 Method C.
    • Brinell Hardness (HB) determined following ASTM E110.
    • Porosity calculated using pycnometric measurements in accordance with ASTM B962.
    • Fluidity Length measured using a standardized Qudong fluidity mold to determine the distance traveled by molten metal before solidification.
  • Microstructural Analysis

    Microstructural observations were conducted using optical microscopy at 365× magnification to examine grain morphology, reinforcement distribution, and pore formation. Scanning Electron Microscopy (SEM) was subsequently employed to obtain higher-resolution observations of particle dispersion, agglomeration, and interfacial characteristics between the aluminum matrix and rice husk ash.

  • Data Analysis

    Experimental observations from all parameter combinations were systematically compared to determine how pouring temperature, reinforcement ratio, and pattern thickness influenced the resulting composite properties. Relationships among microstructure, porosity, hardness, surface finish, and melt fluidity were interpreted to identify processing conditions that produced balanced mechanical and physical performance.

5. Key Findings

Higher Pouring Temperatures Improved Composite Performance

Increasing the pouring temperature significantly enhanced molten metal fluidity, allowing the aluminum–RHA mixture to fill mold cavities more completely. Improved flow characteristics produced denser castings and generally increased Brinell hardness. However, excessively high temperatures also promoted greater gas generation during Styrofoam decomposition, contributing to increased porosity in some specimens.

Rice Husk Ash Successfully Reinforced Scrap Aluminum

The incorporation of rice husk ash effectively strengthened the recycled aluminum matrix. As the reinforcement content increased, hardness improved because silica-rich RHA particles acted as strengthening phases within the composite. Nevertheless, higher reinforcement levels also promoted particle agglomeration and pore formation when dispersion became less uniform.

The 60:40 Aluminum–RHA Composition Produced the Highest Hardness

Among the investigated compositions, the 60:40 aluminum–RHA ratio produced the highest Brinell hardness value of approximately 45.6 HB. The increased silica reinforcement improved resistance to plastic deformation, although the accompanying increase in porosity indicated a trade-off between mechanical strengthening and internal structural integrity.

Fluidity Increased with Pouring Temperature

Fluidity length increased as pouring temperature rose because the molten composite remained liquid for a longer period before solidification. The maximum fluidity of approximately 252.65 mm was achieved at the highest pouring temperature and the highest reinforcement composition investigated, demonstrating improved mold-filling capability during evaporative pattern casting.

Pattern Thickness Influenced Surface Quality

Styrofoam pattern thickness strongly affected casting surface finish. Thicker patterns generated greater quantities of decomposition gases during casting, resulting in rougher casting surfaces. Conversely, thinner patterns generally produced smoother surfaces and improved dimensional consistency.

Microstructure Became Increasingly Heterogeneous with Higher RHA Content

Optical microscopy and SEM observations showed that increasing the RHA fraction resulted in greater particle dispersion throughout the aluminum matrix. At higher reinforcement levels, larger particle agglomerations and increased porosity became evident, demonstrating the importance of achieving homogeneous reinforcement distribution during mixing.

Porosity Represented the Principal Trade-Off

Although higher pouring temperatures and greater RHA contents improved hardness and fluidity, they simultaneously increased pore formation due to gas evolution and reinforcement clustering. Consequently, optimizing evaporative pattern casting requires balancing mechanical improvement with acceptable porosity levels.

Process Parameters Strongly Interacted

The results demonstrate that pouring temperature, reinforcement composition, and Styrofoam pattern thickness should not be optimized independently. Their combined interaction ultimately determines casting quality, mechanical performance, dimensional accuracy, and microstructural characteristics of Al–RHA composites.

6. Scientific Contribution

  • Introduces one of the first comprehensive investigations of scrap aluminum–RHA composites produced through evaporative pattern casting. Previous studies have primarily focused on stir casting or powder metallurgy using primary aluminum, whereas this research systematically evaluates recycled aluminum processed by EPC.
  • Provides a comprehensive assessment of multiple process parameters. The study simultaneously evaluates pouring temperature, aluminum–RHA composition ratio, and Styrofoam pattern thickness, allowing their combined influence on composite quality to be understood.
  • Demonstrates the feasibility of utilizing agricultural waste as composite reinforcement. The successful incorporation of rice husk ash confirms its potential as a sustainable silica-rich reinforcement capable of improving hardness while reducing dependence on synthetic ceramic particles.
  • Advances understanding of process–microstructure–property relationships. By correlating microstructural observations with hardness, porosity, surface roughness, and fluidity, the study explains how manufacturing conditions influence final composite performance.
  • Supports circular manufacturing strategies. Combining recycled aluminum with agricultural waste provides an environmentally responsible manufacturing approach aligned with sustainable engineering and resource efficiency.
  • Offers experimentally validated process optimization guidance. The findings provide practical recommendations for selecting casting parameters that balance mechanical improvement with acceptable casting quality in evaporative pattern casting operations.

7. Industrial Implications

  • Supports sustainable foundry operations. Manufacturers can utilize recycled aluminum and agricultural waste to reduce raw material consumption while producing value-added engineering composites.
  • Improves evaporative pattern casting practice. Understanding the interaction among pouring temperature, reinforcement ratio, and pattern thickness enables foundries to optimize production quality and reduce casting defects.
  • Provides an environmentally friendly reinforcement alternative. Rice husk ash offers an economical replacement for conventional ceramic reinforcements while simultaneously reducing agricultural waste disposal.
  • Supports lightweight engineering applications. The developed composites have potential applications in automotive, transportation, agricultural machinery, and general mechanical components where lightweight materials with improved hardness are desirable.
  • Enhances manufacturing efficiency. Improved understanding of fluidity behavior assists engineers in selecting casting conditions that minimize incomplete filling and casting defects.
  • Contributes to circular economy implementation. The simultaneous reuse of industrial scrap aluminum and agricultural biomass waste demonstrates a practical pathway toward resource-efficient manufacturing and reduced environmental impact.
  • Provides valuable reference data for composite manufacturing. The experimentally established relationships between processing conditions and material properties can support process optimization in future industrial production of aluminum matrix composites.

8. Research Limitations

  • The study investigated only three major process parameters. Although pouring temperature, aluminum–RHA composition ratio, and Styrofoam pattern thickness are critical variables in evaporative pattern casting, other influential processing parameters—such as stirring speed, stirring duration, mold compaction, cooling rate, and mold permeability—were not examined.
  • The reinforcement composition was limited to relatively high RHA contents. The experimental investigation focused on aluminum–RHA ratios of 70:30, 65:35, and 60:40. Lower reinforcement fractions commonly reported in aluminum matrix composite studies were outside the scope of this research, limiting direct comparison across a wider composition range.
  • The investigation concentrated on selected physical and mechanical properties. Composite performance was evaluated using surface roughness, Brinell hardness, porosity, fluidity length, and microstructural observations. Other important engineering properties, including tensile strength, impact resistance, fatigue behavior, corrosion resistance, and wear performance, were not investigated.
  • The work focused exclusively on laboratory-scale fabrication. The evaporative pattern casting process was evaluated under controlled experimental conditions. Industrial-scale manufacturing variables, production repeatability, and large-volume process stability were beyond the scope of the present investigation.
  • Increasing reinforcement content introduced unavoidable trade-offs. Although higher rice husk ash contents improved hardness and fluidity, they also increased porosity and particle agglomeration. Consequently, optimization requires balancing multiple material properties rather than maximizing a single performance indicator.
  • The study did not include long-term service evaluation. The durability of the developed composites under prolonged mechanical loading, cyclic thermal exposure, or aggressive service environments remains unknown and requires further investigation.

9. Future Research Opportunities

  • Investigate broader aluminum–RHA composition ranges to determine the optimum reinforcement percentage that simultaneously maximizes hardness while minimizing porosity and particle agglomeration.
  • Evaluate additional evaporative pattern casting variables, including stirring speed, stirring duration, mold compaction density, cooling conditions, pouring rate, and mold permeability to further optimize composite quality.
  • Examine additional mechanical properties such as tensile strength, compressive strength, flexural strength, fracture toughness, fatigue resistance, and impact performance to provide a more comprehensive understanding of composite behavior.
  • Investigate tribological performance, including wear resistance and friction behavior, to assess the suitability of Al–RHA composites for moving mechanical components.
  • Study corrosion resistance and environmental durability under different service conditions to evaluate long-term reliability in industrial applications.
  • Explore alternative agricultural waste reinforcements or hybrid reinforcement systems to compare their effectiveness with rice husk ash in evaporative pattern casting.
  • Develop numerical simulations and computational models capable of predicting molten metal flow, heat transfer, gas evolution, and porosity formation during evaporative pattern casting.
  • Investigate industrial-scale implementation of scrap aluminum–RHA composite manufacturing to evaluate process repeatability, production efficiency, economic feasibility, and sustainability in commercial foundry operations.

10. Potential for Public Policy Citation

This research provides evidence supporting sustainable manufacturing policies that encourage the utilization of recycled metals and agricultural waste as engineering materials. The successful integration of scrap aluminum with rice husk ash demonstrates a practical example of circular economy implementation by simultaneously reducing industrial waste, agricultural residue disposal, and dependence on virgin raw materials.

Government agencies responsible for industrial development, environmental protection, and resource conservation may use the findings to promote cleaner manufacturing technologies, waste valorization programs, and environmentally responsible metal casting practices. The study also supports national initiatives related to sustainable materials engineering, green manufacturing, industrial decarbonization, and resource efficiency.

From an engineering perspective, the experimentally validated relationships between process parameters and composite properties provide useful technical references for developing manufacturing guidelines, industrial standards, and technology adoption programs aimed at expanding the use of recycled materials in advanced manufacturing industries.

11. Who Should Read This Paper?

  • Researchers working in aluminum matrix composites, metal matrix composites, sustainable materials engineering, and advanced manufacturing technologies.
  • Materials scientists investigating biomass-derived reinforcement materials and environmentally friendly composite fabrication.
  • Mechanical, manufacturing, and metallurgical engineers involved in metal casting, foundry technology, and composite material development.
  • Foundry engineers seeking optimized evaporative pattern casting parameters for producing high-quality aluminum components.
  • Industrial practitioners interested in implementing circular manufacturing strategies through recycled aluminum and agricultural waste utilization.
  • Graduate students and academics studying sustainable manufacturing, metal casting processes, and composite materials.
  • Government agencies, policy makers, and industrial organizations promoting green manufacturing, waste utilization, and resource-efficient production systems.

12. Final Thoughts

This study presents a comprehensive experimental investigation into the fabrication of aluminum matrix composites reinforced with rice husk ash using evaporative pattern casting. By systematically examining the influence of pouring temperature, reinforcement composition, and Styrofoam pattern thickness, the research demonstrates how processing parameters directly affect microstructure, hardness, surface quality, porosity, and fluidity.

A significant contribution of the work lies in its integration of two sustainable resources—recycled scrap aluminum and agricultural waste—into a single engineering material capable of delivering improved mechanical performance. The findings show that increasing reinforcement content and pouring temperature enhances hardness and mold-filling capability, although these improvements must be balanced against the accompanying increase in porosity.

Beyond its experimental findings, the study provides valuable guidance for researchers and manufacturing engineers seeking to optimize evaporative pattern casting processes. It also reinforces the broader concept that sustainable material development can simultaneously improve engineering performance while supporting circular economy principles. Consequently, this work represents an important contribution to environmentally responsible composite manufacturing and offers a strong foundation for future investigations into high-performance recycled aluminum composites.

 


13. Suggested Citations

Teknomekanik (UNP) Style

Siswanto, R., Ghofur, A., Subagyo, R., Tamjidillah, M., Mahmud, Ma’ruf, & Nordiman, A. (2026). Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites. Teknomekanik, 9(1), 91–109. https://doi.org/10.24036/teknomekanik.v9i1.46072

APA (7th Edition)

Siswanto, R., Ghofur, A., Subagyo, R., Tamjidillah, M., Mahmud, Ma’ruf, & Nordiman, A. (2026). Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites. Teknomekanik, 9(1), 91–109. https://doi.org/10.24036/teknomekanik.v9i1.46072

IEEE Style

R. Siswanto, A. Ghofur, R. Subagyo, M. Tamjidillah, Mahmud, Ma’ruf, and A. Nordiman, "Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites," Teknomekanik, vol. 9, no. 1, pp. 91–109, Feb. 2026, doi: 10.24036/teknomekanik.v9i1.46072.

Harvard Style

Siswanto, R., Ghofur, A., Subagyo, R., Tamjidillah, M., Mahmud, Ma’ruf & Nordiman, A. (2026) 'Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites', Teknomekanik, 9(1), pp. 91–109. Available at: https://doi.org/10.24036/teknomekanik.v9i1.46072.

Vancouver Style

Siswanto R, Ghofur A, Subagyo R, Tamjidillah M, Mahmud, Ma’ruf, Nordiman A. Effects of process parameters on the evaporative pattern casting of scrap aluminum–RHA composites. Teknomekanik. 2026;9(1):91–109. doi:10.24036/teknomekanik.v9i1.46072.

Chicago (Author–Date)

Siswanto, Rudi, Abdul Ghofur, Rachmat Subagyo, Mastiadi Tamjidillah, Mahmud, Ma’ruf, and Adi Nordiman. 2026. "Effects of Process Parameters on the Evaporative Pattern Casting of Scrap Aluminum–RHA Composites." Teknomekanik 9 (1): 91–109. https://doi.org/10.24036/teknomekanik.v9i1.46072.

MLA (9th Edition)

Siswanto, Rudi, et al. "Effects of Process Parameters on the Evaporative Pattern Casting of Scrap Aluminum–RHA Composites." Teknomekanik, vol. 9, no. 1, 2026, pp. 91–109. https://doi.org/10.24036/teknomekanik.v9i1.46072.

14. Editorial Note

This review has been independently prepared by Engineering Research Insights to communicate recent advances in engineering research to a broader academic and professional audience. The scientific analysis presented in this article is derived exclusively from the original peer-reviewed publication and is intended for educational and scholarly communication purposes. Bibliographic metadata have been verified using the official journal webpage, while the scientific interpretation is based solely on the published article. Readers are encouraged to consult the original paper for complete experimental details, datasets, figures, and supplementary information.

15. SEO Meta Description

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16. SEO Keywords

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