Comprehensive Analysis of Porous Aluminum Foam Sheet Plate

Foam aluminum has a series of excellent properties, such as high porosity, large specific surface area, high specific strength, high specific stiffness, good energy absorption, damping and shock absorption performance, corrosion resistance, high temperature resistance, electromagnetic shielding, non-toxic, easy processing, coating surface treatment, etc. Because of its excellent physical and mechanical properties, foam metal can be used as both structural materials and functional materials.

Chalco porous aluminum foam sheet plate products

Open-cell aluminum foam

Open-cell aluminum foam has interconnected pores, allowing fluids and gases to pass through easily. It's used in sound absorption, filtration, and cooling applications.

Closed-cell aluminum foam

Closed-cell aluminum foam has sealed pores, providing strength and impact resistance. It's ideal for thermal insulation and lightweight structural uses.

AFS aluminum foam sandwich

Foam aluminum sandwich panel is an innovative material with a three-layer structure. It is primarily composed of a formed aluminum core, perfectly sandwiched between two aluminum cover layers.The unique cover layers are made of metal material and are fused to the core layer without the need for adhesives, ensuring the stability and strength of the entire panel.

Porous aluminum plate

Perforated foam aluminum panels are lightweight aluminum materials with a porous structure that enhances breathability and reduces weight. They offer excellent energy absorption, fire resistance, and sound insulation, making them ideal for construction, transportation, and electronics.

Porous structure: the pores are small and numerous. Porous aluminum is extremely light, with a density of less than 1/10 of aluminum.

Specific surface area: 10-40 cm²/cm³ (more pores, larger surface area)

High damping performance: porous aluminum plates exhibit a delayed response when force is applied, slowing down impacts. This makes porous aluminum plates very useful in manufacturing impact-resistant components. Additionally, the effect of porous aluminum plates depends on the size of the pores, and this effect can be adjusted by modifying the gap.

Special acoustic properties: porous aluminum plates can absorb sound and reduce noise. Smaller pores result in better sound absorption, and this effect can be adjusted by changing the size and shape of the pores.

Excellent fluid permeability: porous aluminum plates act as filters, effectively removing solid particles from liquids or gases. The material is suitable for various filtration and flow control needs, such as high-temperature dust collectors.

Outstanding surface exchange capacity: the large surface area of porous aluminum plates significantly increases the contact area between fluid and material surface. Porous aluminum plates can be used as excellent materials for making heaters and heat exchangers.

Main performance parameters of Chalco foam aluminum

relative density ρ/ρS=0.02GPa～0.2GPa,

Young's modulus E=0.02GPa～210GPa,

shear modulus G=0.01GPa～1.0GPa,

bending modulus Ef=0.03GPa～3.3GPa,

Poisson's ratio υ= 0.31～0.34,

Compressive strength σ C=0.04MPa～7.0MPa,

tensile strength σ T=0105MPa～8.5MPa,

thermal conductivity λ= 0.3W/(m・K)～10W/(m・K).

Performance features of foam aluminum

• Lightweight: The density is only 10% - 40% of the metal aluminum;
• High specific stiffness: The bending stiffness is 1.5 times of steel;
• High damping and shock energy absorption: The damping performance is 5-10 times of that of metal aluminum;
• Good sound insulation (closed hole) and sound absorption (through hole): When the acoustic frequency is between 800~4000HZ, the sound insulation coefficient of closed cell foam aluminum is more than 0.9; When the sound frequency is between 125~4000HZ, the sound absorption coefficient of through-hole foam aluminum can reach 0.8;
• Excellent electromagnetic shielding performance: When the electromagnetic wave frequency is between 2.6~18 GHz. Electromagnetic shielding capacity of foam aluminum can reach 60~90dB ;
• Low thermal conductivity: Closed-cell foam aluminum has thermal conductivity similar to marble, while open-cell foam aluminum offers good heat dissipation. Foam performance depends on pore structure parameters, mainly influenced by the preparation process.

Structural characteristics of foam aluminum

• The metal skeleton composition and pore structure are controllable, which can meet different needs.
• Large aperture: 0.3-7mm;
• Diversified pore structure: closed cell, through-hole and micro through-hole foam aluminum;
• High and controllable porosity: 63%-90% ;
• Large specific surface area: 10-45cm/cm2.

Chalco foam aluminum sheet plate cooperative industries

Application of foam aluminum in auto industries

Application of foam aluminum in cars

The application of foam aluminum in the automotive industry mainly includes lightweight structure, energy absorption structure and damping heat transfer structure

Contact us now

This aluminum foam is produced by injecting gas into molten metal. First, the base material (aluminum or aluminum alloy) is melted using traditional casting equipment and mixed with 10%-30% (vol) of a thickening agent (SiC or Al2O3 particles). The mixture is poured into a container with a funnel, and gas is injected through a small nozzle to form dispersed bubbles. Bubble size is controlled by adjusting gas flow, mixer design, and mixing speed. Ceramic particles stabilize the bubbles, increase viscosity, and slow bubble rise. The molten foam is then cooled and solidified on a conveyor belt to form closed-cell foam.

The three circles represent different application fields, and the characters on the outside of the circle illustrate the advantages and characteristics of foam aluminum corresponding to the three application fields. The overlapping part of two circles represents the dual function integration of foam aluminum. The ideal application is the multi-function integration represented by three circles coincidence.

• Automotive Industry: Aluminum foam is widely used as a filler material in automotive products, including in German GAOFISHER vehicles.
• Engine Hoods: Engine hoods made from Zhongaluminum foam can withstand head impacts of up to 11 m/s, ensuring occupant protection.
• Impact Absorption Boxes: Impact absorption boxes filled with Zhongaluminum foam can resist impacts of up to 5 m/s.
• A and B Pillars: A and B pillars filled with Zhongaluminum foam have three times the bending strength of hollow pillars and allow for the casting of complex ribbed structures, simplifying mold design and manufacturing.

In addition to the applications identified in the figure, foam aluminum can also be used in the impact energy absorption structure between the front longitudinal beam, rear longitudinal beam, bumper and chassis, internal appliances and decorative parts, fender, top cover plate, top cover longitudinal beam, rear diaphragm, connecting rod, piston, lower control arm, transmission gear, cylinder block, brake cylinder piston, muffler, etc.

Application of foam aluminum sheet plate in construction

Foam aluminum panel in construction

Many buildings need lightweight, strong, and flame-retardant materials. Aluminum foam, with its light weight and fire-resistant properties, can replace traditional materials, making it ideal for fire doors and partitions.

Contact us now

• Ceilings and Partition Walls: Lightweight and aesthetically pleasing, providing fire resistance, sound insulation, noise reduction, and thermal insulation.
• Public Space Decorations: In venues like stadiums, swimming pools, concert halls, conference rooms, entertainment halls, and transportation hubs, aluminum foam effectively prevents sound resonance and echo.
• Elevator Cabins: Using aluminum foam panels reduces energy consumption and noise.
• Fire Doors and Partitions: The high-temperature resistance and non-flammable properties of aluminum foam make it an ideal material for fire doors and partitions.
• Building Exterior Walls: As an exterior wall material, aluminum foam not only enhances aesthetics but also improves thermal insulation and fire resistance.

Application of foam aluminum in high-speed railway and transportation

Anti crash structure of high-speed rail train and sound barrier on high-speed rail line

Aluminum foam enhances high-speed train safety with energy-absorbing columns and improves noise control with panels that reduce high-frequency noise by over 20 dB.

Aluminum foam used on aerospace

In aerospace, aluminum foam is valued for its lightweight strength, energy absorption, and thermal insulation, improving fuel efficiency, safety, and thermal protection.

School bus made by aluminum foam

Before and after, the school bus anti-collision beam uses aluminum foam-filled tubes with a 1-2mm steel plate surface. It absorbs most impact energy during collisions. The upright columns and cross beams, made of square steel tubes filled with aluminum foam, double the anti-rollover capability.

The aluminum foam sound barrier on highway and bridge

Aluminum foam sound barrier has been build in many cities, aluminium foam absorption board is 800mmx 2000mm, its cavity 70mm, the noise can be decreased 20dB.

Application of foam aluminum in military industry

Light missile manhole cover

The new missile manhole cover, made from armor plate and aluminum foam, is six times lighter than the original 600-ton concrete version, while offering superior anti-explosion and armor-piercing capabilities.

Wartime quick mounting large span bridge made of aluminum foam

In wartime, the armored forces need quick mounting support bridge to across the river and ditch. The quick mounting support bridge at home and abroad is made of steel, its maximum length is 53 meters. The 70 meters long bridge can be manufacture by aluminum foam materials, as shown below.

Light explosion door

The current explosion-proof door is 300-400mm thick, weighs 20-30 tons, and has a max antiknock capacity of 3 MPa. A new design using aluminum foam and 5mm carbon steel reduces weight to a few tons while increasing antiknock capacity to over 1000 MPa.

Aluminum foam sandwich flight deck of aircraft carrier

Using an aluminum foam sandwich flight deck reduces plane bounce by over 50%, improving the chances of cable arrest and ensuring a smoother landing. It also enhances blast resistance and anti-missile capabilities.

Preparation technology of foam aluminum

The preparation technology of foam has become a research focus in the field of new materials. The following is a detailed introduction to the preparation process of foam aluminum:

1. Solid metal sintering method

Most of the foam aluminum produced by this method has a through-hole structure. This is due to the fact that most of the aluminum particles are connected with each other through sintering, and the aluminum is always kept solid.

1.1 Powder metallurgy foaming method

The process principle is to mix aluminum powder and foaming agent powder and compress them to obtain a preform with a gas tight structure. Heating the preform will cause the foaming agent to decompose and release gas, forcing the preform to expand to obtain foam aluminum.

Process flow of powder metallurgy foaming method:

Features: First, compared with other methods, the available alloy composition is more extensive, which is conducive to improving the mechanical properties of foam aluminum; Second, it can directly manufacture components with complex shapes.

The disadvantage is that the process parameter range of this method is narrow, the cost is high, and the size of foam aluminum produced is limited.

1.2 Loose powder sintering

This method is mostly used to prepare foam copper. Because the dense oxide film on the surface of aluminum powder will prevent the particles from sintering together, it is relatively difficult to prepare foam aluminum by loose powder sintering method. At this time, the oxide film can be destroyed by means of deformation to make the particles stick together more easily; Or add magnesium, copper and other elements to form eutectic alloy when sintering at 595~625 ℃.

This production method includes three processes:

Features: The advantages are simple process and low cost. The disadvantages are low porosity and low material strength. If fiber is used instead of powder, porous materials can also be obtained.

1.3 Slurry molding method

The slurry forming method is to form a suspension of metal aluminum powder, foaming agent (hydrofluoric acid, aluminum hydroxide or orthophosphoric acid), reaction additive and organic carrier. Stir it into a state containing foam, and then put it into the mold for heating and roasting. Then the slurry starts to become sticky, and with the gas generated, it starts to expand, and finally gets foam aluminum with certain strength.

If the slurry is directly poured into the polymer foam, the polymer material can be pyrolyzed by heating up, and the open cell foam material can also be made after sintering.

This production method includes:

Features: The foam aluminum produced has low strength and cracks.

1.4 Sintering dissolution method

The aluminum powder and salt powder are evenly mixed and pressed into billets. During the pressing process, the salt powder basically keeps its original appearance. The aluminum powder undergoes plastic deformation and fills the gap between the salt particles to form a continuous network matrix. Then, the billets are sintered to combine the reticulated aluminum matrix into a whole. Finally, the sintered billet sample is placed in hot water, and the salt particles in the billet are filtered out to obtain uniform open cell foam aluminum parts.

The process includes:

Features: The advantage is that by selecting the shape and particle size of the salt powder, the shape and size of the holes can be controlled within a certain range; The porosity can be precisely controlled by the volume ratio of mixed powder; Can produce gradient foam materials; It can manufacture net products; The equipment is simple and easy to realize mass production.

The limitation is that only medium density foam aluminum with a pore range of 50%~80% can be obtained; Sodium chloride is easy to remain in the finished product, causing local corrosion of aluminum base; The process cycle is long.

1.5 Hollow three-dimensional skeleton method

The liquid metal is diecasted into a ceramic with a hollow skeleton 3D mesh structure, cooled, and then the skeleton is removed.

The process includes:

Features: The porosity of foam is adjustable, the operation is cumbersome, the cost is slightly high, and the product range is limited, so its promotion and application are limited.

1.6 Fiber sintering

The process of this method is to first obtain aluminum wire by mechanical drawing or other methods, then make aluminum wire into felt ring by slurry casting or mechanical felt ring, and then sinter it to achieve the required strength and porosity.

The process is as follows:

The advantage of fiber sintering method is that it can obtain higher porosity than powder sintering. The structural properties of the material are maintained at the maximum porosity. At the same porosity, the strength and toughness of foam aluminum produced by this method are higher than those by powder metallurgy method. However, the cost of this method is high.

1.7 Slurry soaked sponge sintering method

The method is to make spongy organic substances into organic precursors of the desired shape, and then use the slurry containing the metal aluminum powder to be processed to penetrate (the carrier of the suspension is water and organic liquid). The soaked organic precursor is dried to remove solvent, sintered and cooled to obtain foam aluminum with high porosity and three-dimensional structure.

The process flow is roughly as follows:

Features: It is mainly affected by the selection and pretreatment of organic precursors, the composition of slurry, the selection of additives, sintering temperature and other factors.

2. Solidification of liquid metal

This method is to produce foam structure through liquid aluminum. It can be directly foamed through aluminum liquid; Porous materials can also be obtained by casting foam materials or closely packed pore forming agents.

2.1 Direct blowing foaming method

First, add the SiC, Al2O3, etc. into the molten metal, and uniformly dispersed to improve the melt viscosity. Then blow gas (such as nitrogen, inert gas, etc.) into the bottom of the melt. A large number of pores are formed in the liquid metal and then cooled and solidified.

Features: continuous preparation of products can be realized; Simple requirements for equipment; The porosity of the product is controllable; Low cost.

2.2 Foaming agent foaming method

Add foaming agent into the aluminum melt and stir it evenly. Heat it to make the foaming agent decompose to produce gas. The gas expands and foams. After cooling, foam metal is obtained. The foaming agent used is usually metal hydride such as TiH2 or ZrH2.

Features: simple equipment requirements, low cost, and continuous product preparation. Short foaming time interval, difficult control of foaming temperature, uneven bubble distribution, poor product reproducibility, etc.

2.3 Seepage casting

Percolation casting is to stack removable particles (such as NaCl) in the mold, press them into billets, pour metal after preheating, and then remove the particles to prepare a through-hole foam structure with interconnected holes.

Process principle:

Schematic Diagram of Vacuum Seepage Method Device

Features: The preparation process has controllable pore diameter parameters, high through-hole ratio, large specific surface area, low cost, and is suitable for large-scale industrial production. The disadvantage is that due to the high surface tension of liquid metal, the particles can not be completely wetted, so the gap between particles can not be completely filled.

2.4 Investment casting

The investment casting method is to immerse the molded polymer foam material into the liquid refractory to fill the gap of the refractory. After the refractory is hardened, heating will vaporize and decompose the foam material to form a three-dimensional framework with the shape of the original foam material. Pour the molten aluminum into the casting mold, remove the refractory after solidification, and then obtain foam aluminum with three-dimensional mesh through holes.

Schematic diagram of process principle:

Schematic Diagram of Porous Materials Prepared by Investment Casting

Advantages: various foam metals can be prepared; Opening structure, good production repeatability and relatively stable density.

Disadvantages: low output; high price.

2.5 Solid-gas eutectic solidification

Many metal liquids can form eutectic systems with gases (such as hydrogen). If these metals are melted in a high-pressure hydrogen atmosphere, a uniform melt containing supersaturated hydrogen can be obtained. In the subsequent cooling and solidification process, the melt will undergo eutectic transformation and decompose into solid and gas phases. During directional solidification, because the solubility of hydrogen in the solid phase and liquid phase differs greatly, the supersaturated hydrogen will separate from the solid phase to form bubbles, thus obtaining the required foam aluminum.

Schematic Diagram of Process Principle:

Schematic Diagram of Solid Gas Eutectic Solidification Process for Preparing Porous Materials

Features: High porosity foam aluminum with isotropic and anisotropic pore shapes can be obtained by precisely controlling cooling conditions (pressure, cooling rate, heat dissipation direction).

2.6 Ball feeding method

The method of adding ball material is to add particles or hollow balls into the aluminum alloy melt and strengthen the stirring. And casting while the melt is still in relative flow to obtain the composite of aluminum alloy and particles. Then the soluble particles in the aluminum alloy collective are dissolved and removed, and finally a connected porous foam aluminum is obtained.

The process flow is roughly as follows:

Features: The surface tension of liquid metal is high, and the particles or hollow balls cannot be completely wetted, so the gaps between particles cannot be completely filled. The structural continuity of the obtained foam aluminum is poor.

3. Metal deposition

3.1 Electrodeposition

The principle is that foam aluminum is electroplated in alkyl aluminum solution with pretreated foam plastic as cathode and industrial pure aluminum plate as anode.

Process flow of electrodeposition method:

Features: easy to control pore structure, small pore size, uniform pore size, high porosity, and its heat insulation and damping characteristics are better than that of foam aluminum produced by casting method. However, this method has long process, complicated operation, slightly high cost and limited product thickness, so its popularization and application are limited.

3.2 Vapor phase evaporation deposition method

This method is to slowly evaporate the metal aluminum in a high inert atmosphere (102~104Pa). The evaporated metal atoms collide and scatter with the inert gas molecules, rapidly losing kinetic energy. This process is shown in the macroscopic view as the metal vapor temperature decreases. Then the evaporated metal atoms combine with each other to form atomic clusters before reaching the substrate, so "metal smoke" can be seen in the evaporation process. These clusters continue to cool down and deposit on the substrate with inert gas. Because atoms at low temperature are difficult to migrate or diffuse, "metal smoke" particles are loosely stacked to form a hollow foam structure.

Schematic Diagram of Process Principle:

Schematic Diagram of Vapor Phase Evaporative Deposition Process

Features: The formation of metal foam is affected by many factors, such as metal materials, heating power, inert gas pressure, type of vaporization source heater and its distance from the substrate, and substrate materials. The heating power, inert gas pressure and inert gas flow rate are the most important control parameters.

3.3 Splash deposition

Splashing deposition is to evenly spray the powder with inert gas onto the aluminum alloy metal by using the spraying technology. Then it is heated to the melting point of the metal, so that the gas added to the metal expands and forms uniformly distributed and dense holes. After cooling, it is made of foam aluminum products with dense network.

Schematic diagram of process principle:

Schematic Diagram of Splash Deposition

Features: By controlling the partial pressure of inert gas in deposition, the volume fraction of pores of the obtained product can be controlled.

3.4 Molten salt electroplating

Foam aluminum is prepared by electrodeposition in molten salt with foamed plastic as cathode and aluminum plate as anode.

Schematic diagram of process principle:

Schematic Diagram of Electroplating Process Principle

Features: foam aluminum has high porosity and even pores.

4. Others

The following methods are mainly used for scientific research or small batch trial production, and are not widely used in industrial production.

4.1 Secondary foaming method

The secondary foaming method is a preparation method of foam aluminum that combines the advantages of powder metallurgy foaming method and melt foaming method. The technical process is to add viscosity increasing agent (Ca, Al2O3, etc.) into the aluminum melt and stir it evenly. Add foaming agent (pretreated TiH2) under appropriate temperature and viscosity conditions. It is uniformly dispersed, and the melt is cast into the mold for rapid cooling and solidification before TiH2 is decomposed to obtain foaming precursor. When the foaming precursor is heated to a certain temperature, TiH2 in the precursor begins to decompose and foam, and finally foam aluminum is prepared.

4.2 Metal hollow ball method

The method is to form a porous structure by bonding metal hollow spheres together through sintering. Metal hollow spheres can be obtained by chemical synthesis and electrodeposition of a layer of metal on the surface of polymer spheres, and then the polymer spheres are removed.

There are many preparation processes of foam aluminum, and each method has its own advantages and disadvantages. In practical production, melt foaming method, percolation casting method, powder metallurgy foaming method and electrochemical method are widely used. Other processes are mainly used for scientific research or small batch trial production.