What is Aluminum Foam?

Aluminum foam (porous metal based on aluminum and its alloys) has been known for over half a century. However, its applications remain relatively limited due to challenges in achieving repeatability in structure and material properties during production. Advances in aluminum foam technology have addressed some of these issues, leading to the development and investigation of various production processes.

Inspiration and Characteristics

The inventors of aluminum foam were inspired by natural porous materials such as wood, bone, coral, pumice, and other porous minerals. These materials share common features: high strength, low specific weight, and excellent energy absorption. Today, aluminum foam manufacturers can produce metals with similar properties relatively easily. Aluminum foam now has a much wider range of applications across dozens of industries.

Porous metals can have either open or closed pores, depending on the production technology. Open-pored materials are called cellular metals, while closed-pored materials are referred to as metal foams. Each group contains variations that result in a broad spectrum of aluminum foam types with different properties.

Production of Aluminum Foam

Various methods are used to produce aluminum foams, including:

1. From Molten Metal:
   Aluminum foam is obtained from molten metal using different methods. The foam stabilizes as the aluminum cools and solidifies. Gas flows or blowing agents are used to create the foam. Under specific conditions, the blowing agent decomposes and emits gases, forming bubbles. To prevent bubble collapse before solidification, special additives are sometimes used. This process is suitable for producing aluminum foam sheets, simple-shaped products, and aluminum foam sandwiches, which feature a metal foam core enclosed by solid aluminum layers.

2. Casting with Fillers:
   Materials like salt grains can serve as fillers, which are washed out from the aluminum matrix, leaving behind pores. Heat-resistant coated polyurethane foams, which burn out during heat treatment, are also used as fillers.

3. Hollow Spheres:
   In this method, hollow ceramic or metal spheres are embedded into the metal matrix to create the foam structure.

4. Injection Molding:
   Polymer granules can be used to create pores during the injection molding process. Due to the short processing time, these granules do not decompose under high temperatures. They either remain within the metal matrix or are removed through prolonged heat treatment, resulting in open-pored aluminum foam.

5. Powder Metallurgy:
   Aluminum powder mixed with special additives is heated, leading to foaming and sintering processes that produce different types of aluminum foam upon cooling.

6. Additive Manufacturing:
   The most modern method for producing porous metals is additive manufacturing. This approach allows precise control over the component’s shape and 3D structure. However, it remains costly and is currently limited to specific metals.

Properties and Applications

Closed-Pore Aluminum Foam

• Porosity: 80% to 98%.
• Strength: Significantly higher than solid metal of the same weight.
• Applications:
  • Transportation: Reduces vehicle weight, enhancing fuel efficiency or increasing payload capacity.
  • Impact Absorption: Ideal for armor and explosion protection due to its energy absorption capabilities.
  • Sound Reduction: Can be used as noise-absorbing walls along roads and railways, or as acoustic insulation in cinemas and concert halls.
  • Interior/Exterior Design: Lightweight and aesthetically appealing surfaces.

Open-Pore Aluminum Foam

• Features: Allows gases and liquids to pass through, combining low weight with high structural durability.
• Applications:
  • Filters: For gases and liquids.
  • Noise Reduction: In pneumatic devices.
  • Heat Exchangers: Various configurations for efficient thermal management.
  • Vacuum Tables: For forming EPP/EPS products.

Advantages of Porous Aluminum

Thanks to its high flexibility and adaptability, porous aluminum competes effectively with other porous materials across a range of applications. In many cases, it replaces sintered metals, porous ceramics, porous plastics, meshes, and wire materials.

For more information about our technology, the properties, and the applications of porous aluminum, please visit our website.