Recycling Particle Reinforced Aluminium Matrix Composite using Centrifugel Filtration

M.Sc. Shible Kavungal Kolparambath, Prof. Dr.-Ing. Michal Szucki, TU Bergakademie Freiberg, Foundry Institute.

Metal Matrix Composites (MMCs) are advanced materials in which a base alloy is reinforced with fibers, particles, or other structures to combine the advantageous properties of both the metal and the reinforcing material. Among the different types of MMCs, Aluminum Matrix Composites (AMCs) are the most widely used, accounting for approximately 40% of the global MMC market. When aluminum alloy is combined with particles such as silicon carbide (SiC), the resulting AMCs exhibit enhanced characteristics, such as a higher strength-to-weight ratio, improved wear resistance, and greater thermal stability. These properties make AMCs ideal for high-performance applications, including aerospace components like structural parts and landing gear, as well as automotive parts such as brake discs and engine components [1]. With the increasing demand for lightweight materials and advancements in AMC production, the use of AMC-related castings has significantly risen, leading to a growing accumulation of scrap. To maximize resource recycling and minimize waste, it is crucial to find ways to reuse this material.

To address these challenges, engineers and researchers are focusing on developing effective methods for recycling AMC scraps. Traditional recycling methods for metallic materials, such as simple remelting, have proven ineffective for AMCs. Multiple remelting cycles often result in non-uniform particle distribution and the formation of agglomerates, which negatively affect the material's properties and render it unsuitable for reuse [2]. An alternative approach involves filtering out the SiC particles to recover and reuse the aluminum matrix. A recent study examined this method using a standard 20 pores per inch (ppi) Al₂O₃ ceramic foam filter. However, the results showed a clogging effect caused by the SiC agglomerates, leading to incomplete mold filling and underscoring the need for a new filtration method [3].

To recycle AMC scraps and develop adequate cleaning technology, the Foundry Institute of TU Bergakademie Freiberg, in collaboration with ASK Chemicals GmbH, has proposed a rotational-assisted filtration technology. This filter system is currently used for cast steel and iron [4]. It utilizes centrifugal force to separate larger SiC particles and agglomerates, followed by the use of a ceramic foam filter to capture smaller particles.

The current research involves a series of numerical simulations using particles of various sizes to design an innovative centrifugal chamber. The chamber induces a circular motion, creating a vortex that generates centrifugal force. This force drives larger particles and agglomerates toward the chamber walls while preventing the introduction of new oxide bubbles into the system. Additionally, various test series will be conducted to identify the most effective filter structure, material, and coating for trapping smaller particles and achieving optimal filtration efficiency.

In preliminary casting trials with the newly developed geometry, a significant accumulation of particles was observed within the centrifugal chamber. Analysis indicated a reduction of approximately 35% in particle concentration in regions before and after filtration, highlighting the system's initial effectiveness in separating larger agglomerated particles. Furthermore, mechanical property evaluation showed a positive trend, with increases of up to 20% in ultimate tensile strength and hardness, supporting the efficacy of the filtration method in enhancing material properties.

To further optimize this process, additional experimental trials are planned using cylindrical filters, including the application of hybrid tubular filters with combined pores per inch (PPI) ratings, such as 20 and 30 ppi, aimed at improving filtration performance. By implementing rotational-assisted filtration technology, this approach offers a cost-effective solution for the recycling of particle- and fiber-reinforced aluminum matrix composites (AMCs) within the foundry industry. This method not only supports efficient particle separation but also adds value by enabling closed-loop material cycles, which is essential as AMC production and the accompanying scrap volume continue to increase.

The proposed technology addresses key sustainability goals, offering the flexibility to either recycle the metal matrix by removing particles completely or to produce new cast parts with a consistent particle distribution. In both applications, the use of this technology has potential benefits in lowering CO₂ emissions and reducing energy use, aligning with the industry's push for environmentally sustainable practices in AMC recycling and reuse.

References

1. Stojanovic, B., Ivanovic, L.: Application of aluminium hybrid composites in automotive industry, Tehnicki Vjesnik, Vol. 22, Issue 1, 2015, pp. 247-251.

2. A. Klasik, J. Sobczak, K. Pietrzak, Changes in properties of aluminium matrix composite reinforced with SiC particles after multiple remelting. Mater. Res. Innov. 15(1), 249–252 (2011).

3. Schoß, J.P., Baumann, B., Keßler, A. et al. Filtration Efficiency in the Recycling Process of Particle-Reinforced Aluminum Alloys Using Different Filter Materials. Inter Metalcast 17, 1681–1696 (2023)

4. ASK Chemicals GmbH: Product data sheet - Udicell_Exactflo_Overview_DE.pdf, 20 12 2017