The main applications of metal foams and porous metals are listed below:
- The closed variety is used for structural applications requiring load-bearing features, and for weight-saving and...
- The open variety is ideal for vibration and sound absorption, filtration and catalysis at high temperatures, for heat...
- The open variety is also useful in functional applications...
What is foam metal used for in everyday life?
The open variety is ideal for vibration and sound absorption, filtration and catalysis at high temperatures, for heat exchange and in medical devices. The open variety is also useful in functional applications such as filtration and damping. Foam metal is being used as an experimental prosthetic in animals.
What is the purpose of using metallic foam in vehicles?
The main goal of the use of metallic foams in vehicles is to increase sound dampening, reduce the weight of the automobile, and increase energy absorption in case of crashes, or in military applications, to combat the concussive force of IEDs.
Why are metal foams used in heat exchangers?
Metal foams are used in compact heat exchangers to increase heat transfer at the cost of reduced pressure. However, their use permits substantial reduction in physical size and fabrication costs.
What are the advantages and disadvantages of metal foam?
The advantage of metal foams is that the reaction is constant, regardless of the direction of the force. Foams have a plateau of stress after deformation that is constant for as much as 80% of the crushing.
What are metal foams for?
Metal foams are used in compact heat exchangers to increase heat transfer at the cost of reduced pressure. However, their use permits substantial reduction in physical size and fabrication costs. Most models of these materials use idealized and periodic structures or averaged macroscopic properties.
Are metal foams used in vehicles?
The automotive industry was the largest consumer of metal foams globally, both in terms of value and volume, in 2016. Metals foams are increasingly used in anti-intrusion bars and bumpers in the automotive industry.
What can metal foam be used for in the future?
It can be used in many fields such as construction, aviation, computer, transportation and packaging industry, and with the continuous improvement of foam metal production technology and the continuous deepening of its research and development, The application field of foam metal is still expanding.
How strong is metal foam?
The defining characteristic of metal foams is a very high porosity: typically 75–95% of the volume consists of void spaces. The strength of foamed metal possesses a power law relationship to its density; that is, a 20% dense material is more than twice as strong as a 10% dense material.
How is metal foam effective at absorbing the impact of a car crash?
Popular Answers (1) The expanded structure of foam transmits the energy of a crash much less efficiently than a solid member. At the area of impact, the foam readily conforms to the impacting object. This plastic deformation absorbs the mechanical energy locally.
How will metal foam change the future for better?
Due to its looseness and porousness, the foamed metal can also be used to make artificial bones with its sound absorption and sound insulation properties, which also ensures that the foamed metal can be used as a noise reduction material; it has a very wide range of applications and application prospects.
Is metal foam bullet proof?
If you make that foam out of metal, it turns out, it can stop a projectile. Researchers from North Carolina State University have created just such a foam, and it can freeze the trajectory of a . 50 caliber bullet better than the current armor used by the military—thick slabs of steel—at half the weight.
Is metal foam a natural material?
Metal foams are lightweight cellular materials inspired by nature. Wood, bones and sea sponges are some well-known examples of these types of structures. In fact, solid metallic foams are the conserved image of the corresponding liquid metallic foam.
What are cons of metal foam?
Conventional metal foams have gas-filled pores within the metal, which reduce weight but pose some drawbacks, such as difficulty in controlling the size and shape of the pores during manufacturing. By contrast, metal matrix syntactic foams incorporate porosity in their foam-like structure with hollow particles.
What is aluminum foam used for?
They are used in structures such as heat sinks and exchangers, chemical beds and scrubbers, filters and mist eliminators, and battery plates. Like closed cell foams, they continue to find use in applications where vibration and sound absorption is needed.
Who makes metal foam?
Some of the key players in the metal foam market are ERG Aerospace Corporation (US), CYMAT Technologies Ltd. (Canada), Alantum (South Korea), Mott Corporation (US), Liaoning Rontec Advanced Material Technology Co., Ltd. (China), Shanxi Putai Aluminum Foam Manufacturing Co., Ltd. (China), Mayser GmbH & Co.
What are the uses of metal foam?
The main applications of metal foams and porous metals are listed below: 1 The closed variety is used for structural applications requiring load-bearing features, and for weight-saving and impact-absorbing structures in vehicles 2 The open variety is ideal for vibration and sound absorption, filtration and catalysis at high temperatures, for heat exchange and in medical devices. 3 The open variety is also useful in functional applications such as filtration and damping. 4 Foam metal is being used as an experimental prosthetic in animals. 5 Metal foams with high strengths can act as high-capacity impact-energy absorbers. 6 Automotive industry - the foams reduce the number of parts in the car frame, facilitate assembly, thereby reducing costs and improving performance.
How does a metallic melt foam?
Metallic melts can be foamed by creating gas bubbles in the liquid. These gas bubbles in the metallic melt tend to rise to the surface due to the high buoyancy forces in the high-density liquid. In order to prevent this from happening, the viscosity of the molten metal has to be increased.
What is the blowing agent used to melt hydrogen gas?
Once the viscosity reaches the desired value, titanium hydride as a blowing agent is added serving to release hydrogen gas in the hot viscous liquid. The melt then begins to expand slowly and gradually, filling the foaming vessel. The foaming has to take place at constant pressure.
How is a melt foamed?
The melt is then foamed by injecting gases, namely, air, nitrogen, and argon into it using rotating impellers or vibrating nozzles.
How to foam metallic melts?
Three ways of foaming metallic melts are listed below: Injecting gas into the liquid metal from an external source. Causing the precipitation of gas that had just been dissolved in the liquid. Causing an in-situ gas formation in the liquid by admixing gas-releasing blowing agents to the melt.
What is closed cell foam?
The closed-cell foam is referred to as metal foams, while the open-cell foam is referred to simply as porous metal.
Where are Shinko wire foams made?
Shinko Wire Company, Amagasaki, Japan, has been producing foams using this method. About 1.5 wt.% calcium metal is added to an aluminium melt at 680°C (1256F°). The melt is mixed well and the viscosity starts to increase due to the formation of calcium oxide, calcium aluminum oxide, or Al 4 Ca intermetallics.
How are metal foams made?
Metal foams are produced by creating a multitude of gas-filled bubbles in a metallic melt and allowing these to agglomerate, after which the liquid is solidified to a solid foam. There are different ways to form such foams, differing by the type of gas source, the state of metal used (solid or liquid), the way the bubbles are stabilized and by the procedures applied. Beside the common aluminum alloys, a range of metals and alloys can be processed to foams. This chapter will review the most important production methods for metal foams and explain the background of each method.
What is an amorphous metal foam?
Amorphous metal foam (AMF) or porous metallic glass (PMG) materials have the combined advantages of metal foams and amorphous metals, which include the high compressive plastic strain and high energy absorption capacity of metal foams and the high strength, wear resistance, and low processing temperature of amorphous metals [27]. In order to form pores in amorphous metals, both the liquid state and supercooled liquid state could have been used as pore-forming techniques with the aid of pore-formers like gas-generating additives, soluble placeholders, and hollow carbon spheres. These pore-formers interact with the alloy melt, thus reducing the foaming ability of the glassy metals. This problem could be overcome by dealloying to form the porous structure of glassy alloys. This dealloying technique has been widely applied to fabricating nanoporous metal, metal-oxide, and metal-metalloid architectures, selectively dissolving the most electrochemically active component in those crystalline systems. In this dealloying process, some important parameters must be controlled, such as the alloy composition, the kind of electrolyte, and the electrochemical potential, and structural defects, including segregation, grain boundary, and slip band, serve as the initiation site. It is difficult to dealloy single-phase amorphous metals because of the structural homogeneity, whereas two-phase amorphous alloys can allow for good selective dissolution because they are structurally heterogeneous.
What is the specific stiffness of metal foam?
Metal foams have great specific stiffness (ratio of stiffness to weight), and an almost reversible quasi-elastic zone, so they are applicable to the light structure [2]. For metal foams with a 1/5 density, the specific stiffness is five times that of normally dense metal with the same weight. If the proper shell thickness ...
What is the surface of a solidified foam panel?
The surface of solidified foam panels always comprises a dense skin. Sandwich panels with foamed cores can also be produced via baking of the precursor between metal sheets (aluminum or steel). The liquid foam adheres to the solid sheets in the course of expansion, forming a diffusion bond.
Why are metallic foams so popular?
Metallic foams have attracted considerable interest—partly because processing advances have led to material becoming available at competitive cost and partly because attractive property combinations can be obtained, particularly in terms of specific stiffness and specific energy absorption.
How is metallic foam made?
Metallic foams can also be made by using a chemical blowing agent which decomposes to form a gas. For instance, titanium hydride decomposes to give off hydrogen gas at 400°C; it can be used as a blowing agent for aluminum (melting point of 660°C).
What is open cell foam?
An abbreviated outline is presented here. Open cell metallic foams can be made using open cell polymer foams as a form. The voids of the polymer foam are filled with a heat resistant material such as plaster, the polymer is burned off and molten metal is cast into the resulting form.
How to make open cell metallic foam?
Open-cell metallic foams can be produced by investment casting techniques, in which a disposable pattern with the requisite shape is coated with refractory material by repeatedly dipping into a slurry and drying the absorbed layer. Such procedures are in common industrial use for the production of complex shapes with re-entrant angles, hollow passageways, etc. In the lost wax method, for example, which is extensively used to produce turbine blades, the wax pattern is removed prior to the casting operation by heating in an oven so that melting and evaporation take place. A variant of this, often termed the filled mold technique, involves creating a pattern from a polymeric foam (commonly expanded polystyrene), which is then driven off by contact with the molten metal as it enters the mold. The refractory mold material is mechanically removed after the casting has solidified. This concept can be applied to create open-cell metallic foams, since the removable pattern can itself be in the form of a network or sponge of some sort. The process offers a large degree of flexibility in terms of the choice of metal.
What is metal powder?
A metal powder can be encased in a can which is then filled with an inert gas, pressurized to entrap the gas within the solid powder, and heated to expand the gas; this process has been used to make porous titanium alloy ( Schwartz et al., 1998 ).
Is metallic foam a composite?
It is possible to consider a metallic foam as a composite with metallic and gaseous constituents, i.e., an MMC with a gas as the “reinforcing” constituent. Indeed, this is a sensible approach to the prediction of many of the properties of metallic foams. If the gas is taken to have a Young’s modulus of zero and a very low bulk modulus, then predictions of the elastic properties of the foam, using well-established methods, should be quite reliable. For other properties, such as the thermal conductivity, the fact that the reinforcement is a gas becomes relevant, since convection may have a significant effect – particularly in open cell foams.75
What is metal foam?
Actually, the common use generically leads to consider “metal foams” the uniform dispersions of the gaseous phase in a liquid or in a solid, with the gas occupying over 70% of the volume.
What are the three macro groups of foams?
Starting from their classification, foams can be grouped according to their structure, so defining three macro-groups: isotropic, anisotropic and orthotropic foams. Naturally, each group will be characterized by different properties, performances and applications.
Is metal foam a cellular material?
Yes, metallic. Materials recently conceived, with peculiar characteristics, metal foams are arousing the interest of several sectors, constantly identifying new application sectors. Foams belong to the category of cellular materials, that is to say that class of materials characterized by low densities coupled with interesting mechanical, ...
Open-cell
Open celled metal foam, also called metal sponge, can be used in heat exchangers (compact electronics cooling, cryogen tanks, PCM heat exchangers), energy absorption, flow diffusion, and lightweight optics. The high cost of the material generally limits its use to advanced technology, aerospace, and manufacturing.
Closed-cell
Closed-cell metal foam was first reported in 1926 by Meller in a French patent where foaming of light metals, either by inert gas injection or by blowing agent, was suggested. Two patents on sponge-like metal were issued to Benjamin Sosnik in 1948 and 1951 who applied mercury vapor to blow liquid aluminium.
Composites
Composite metal foam (CMF) is formed from hollow beads of one metal within a solid matrix of another, such as steel within aluminium, show 5 to 6 times greater strength to density ratio and more than 7 times greater energy absorption than previous metal foams.
Stochastic and regular foams
A foam is said to be stochastic when the porosity distribution is random. Most foams are stochastic because of the method of manufacture:
