Aluminium/Titanium oxide formulation for composite materials
Metal matrix composites (MMCs) are widely used in applications where mechanical properties like strength, stiffness, wear resistance, thermal resistance, or lightness are required. MMCs are composed of a metal matrix and reinforcement. Aluminium is one of the most popular matrix metals and ceramics are typically used as reinforcements.
It is often difficult to choose the optimal reinforcement and metal materials as some candidates react with each other. Reinforcements may be coated to prevent such reactions, but coatings increase cost and complexity of MMC production.
Among the various fabrication routes, liquid processing by stir casting is the simplest and cheapest. With this route, integrating ceramic particles in the molten metal is often an issue.
However, it was recently identified that MMC formulation combining calcium with ceramic particles not only provides wetting with liquid aluminium but also promotes binding of the particles with the matrix. A production technique has been developed and it has shown ability to incorporate either small or large amounts of ceramic into the metal. The production technique improves the integrity of the MMC while reducing processing costs.
This technology is available for licensing, or for further development through a collaborative research agreement with NRC. The business opportunity may be referred to by its NRC ID: 12539
This technology is especially interesting to automotive parts and vehicle manufacturers, specialized recreational equipment and tool manufacturers, as well as electrical conductor manufacturers. The new approach promises to decrease their manufacturing costs while improving composite properties.
How it works
There are many fabrication routes for generating MMCs. Stir casting is the lowest cost production method. It involves melting the metal, adding powdered ceramics, stirring and then casting the mixture in the desired shape.
However, some reinforcement and metal combinations may react with each other. For example, it was natural to try carbon fibers in aluminium, as they are both readily used in the aerospace industry. However, aluminium reacts with carbon to form brittle and moisture-sensitive aluminium carbide. For this reason, the reinforcement is often coated to prevent a chemical reaction. Such coatings add cost and difficulties to the production of MMCs, and often introduce additional problems.
Even when the reinforcement is chosen so that it does not react with the molten metal, integration still remains a large issue in the production of the MMC. In the stir casting production method, liquid metals typically exhibit poor wetting with reinforcement particles and separation often occurs. Wetting agents must be added in liquid metal and ceramic mixtures to promote intimate contact between the ceramic powders and metal. For example, magnesium is usually used as a preferred wetting agent, particularly in MMCs with aluminium as the metal and rutile titania powders as the reinforcement.
While other wetting agents have been tested, there is still a need for improved integration of ceramic powders. This is particularly true when producing MMCs that can be stir cast and that allow for the integration of a greater amount of the ceramic powders. The greater amounts of ceramic lead to much stronger MMCs.
A novel MMC production technique has been developed that combines calcium (Ca) with ceramic particles and allows for incorporation of small and large amounts of reinforcement into aluminium, or its alloys. Improved integration of ceramics in liquid aluminium is obtained compared to other techniques. Improved integrity of the MMC is also obtained as the formulation produces a chemically reacted binding layer between the particles and the aluminium.
Stir casting seldom produces more than 25 vol. % of ceramic in the metal matrix and techniques for obtaining greater than 35 vol. % are vastly more expensive and less reliable. This novel technology, remarkably, can achieve formulations beyond 50 vol. % of ceramic by combining calcium with the low-cost ceramic, rutile titania. The production technique reduces melt loss, energy, labour, and MMC processing costs.
- Method can achieve beyond 50 vol. % of ceramic integration using low-cost stir-casting production process of MMCs
- Combination of calcium with ceramics improves the integrity of the MMCs
- Method reduces melt loss, energy, labour, and, in turn, processing costs.
- NRC file 12539: The patent is pending in Canada, the US and Europe.
To inquire about this technology, please contact:
David Fraser, Business Advisor
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