Metal matrix composite
Encyclopedia
A metal matrix composite (MMC) is composite material
with at least two constituent parts, one being a metal
. The other material may be a different metal or another material, such as a ceramic
or organic compound
. When at least three materials are present, it is called a hybrid composite. An MMC is complementary to a cermet
.
matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminum to generate a brittle and water-soluble compound Al4C3
on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel
or titanium boride
.
material into which the reinforcement is embedded, and is completely continuous. This means that there is a path through the matrix to any point in the material, unlike two materials sandwiched together. In structural applications, the matrix is usually a lighter metal such as aluminum
, magnesium
, or titanium
, and provides a compliant support for the reinforcement. In high temperature applications, cobalt
and cobalt-nickel alloy matrices are common.
coefficient, or thermal conductivity
. The reinforcement can be either continuous, or discontinuous. Discontinuous MMCs can be isotropic, and can be worked with standard metalworking techniques, such as extrusion, forging or rolling. In addition, they may be machined using conventional techniques, but commonly would need the use of polycrystaline diamond tooling (PCD).
Continuous reinforcement uses monofilament wires or fibers such as carbon fiber or silicon carbide
. Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength. One of the first MMCs used boron
filament as reinforcement. Discontinuous reinforcement uses "whiskers"
, short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide
.
Solid state methods
Liquid state methods
Vapor deposition
In situ fabrication technique
MMCs are nearly always more expensive than the more conventional materials they are replacing. As a result, they are found where improved properties and performance can justify the added cost. Today these applications are found most often in aircraft components, space systems
and high-end or "boutique" sports equipment. The scope of applications will certainly increase as manufacturing costs are reduced.
In comparison with conventional polymer matrix composites, MMCs are resistant to fire, can operate in wider range of temperatures, do not absorb moisture
, have better electrical and thermal conductivity, are resistant to radiation damage
, and do not display outgassing
. On the other hand, MMCs tend to be more expensive, the fiber-reinforced materials may be difficult to fabricate, and the available experience in use is limited.
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
with at least two constituent parts, one being a metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
. The other material may be a different metal or another material, such as a ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
or organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
. When at least three materials are present, it is called a hybrid composite. An MMC is complementary to a cermet
Cermet
A cermet is a composite material composed of ceramic and metallic materials. A cermet is ideally designed to have the optimal properties of both a ceramic, such as high temperature resistance and hardness, and those of a metal, such as the ability to undergo plastic deformation. The metal is used...
.
Composition
MMCs are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. For example, carbon fibers are commonly used in aluminumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminum to generate a brittle and water-soluble compound Al4C3
Aluminium carbide
Aluminium carbide, chemical formula Al4C3, is a carbide of aluminium. It has the appearance of pale yellow to brown crystals. It is stable up to 1400 °C. It decomposes in water with the production of methane.-Structure:...
on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
or titanium boride
Titanium boride
Titanium diboride is an extremely hard ceramic compound composed of titanium and boron which has excellent resistance to mechanical erosion...
.
Matrix
The matrix is the monolithicSingle crystal
A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
material into which the reinforcement is embedded, and is completely continuous. This means that there is a path through the matrix to any point in the material, unlike two materials sandwiched together. In structural applications, the matrix is usually a lighter metal such as aluminum
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, or titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, and provides a compliant support for the reinforcement. In high temperature applications, cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
and cobalt-nickel alloy matrices are common.
Reinforcement
The reinforcement material is embedded into the matrix. The reinforcement does not always serve a purely structural task (reinforcing the compound), but is also used to change physical properties such as wear resistance, frictionFriction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
coefficient, or thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
. The reinforcement can be either continuous, or discontinuous. Discontinuous MMCs can be isotropic, and can be worked with standard metalworking techniques, such as extrusion, forging or rolling. In addition, they may be machined using conventional techniques, but commonly would need the use of polycrystaline diamond tooling (PCD).
Continuous reinforcement uses monofilament wires or fibers such as carbon fiber or silicon carbide
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
. Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength. One of the first MMCs used boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
filament as reinforcement. Discontinuous reinforcement uses "whiskers"
Monocrystalline whisker
A monocrystalline whisker is a filament of material that is structured as a single, defect-free crystal. Typical whisker materials are graphite, alumina, iron, or silicon. Single-crystal whiskers of these materials are noted for having very high tensile strength...
, short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
.
Manufacturing and forming methods
MMC manufacturing can be broken into three types: solid, liquid, and vapor.Solid state methods
- Powder blending and consolidation (powder metallurgyPowder metallurgyPowder metallurgy is the process of blending fine powdered materials, pressing them into a desired shape , and then heating the compressed material in a controlled atmosphere to bond the material . The powder metallurgy process generally consists of four basic steps: powder manufacture, powder...
): Powdered metal and discontinuous reinforcement are mixed and then bonded through a process of compaction, degassing, and thermo-mechanical treatment (possibly via hot isostatic pressingHot isostatic pressingHot isostatic pressing is a manufacturing process used to reduce the porosity of metals and influence the density of many ceramic materials. This improves the material's mechanical properties and workability....
(HIP) or extrusionExtrusionExtrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...
). - Foil diffusionDiffusionMolecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
bonding: Layers of metal foil are sandwiched with long fibers, and then pressed through to form a matrix.
Liquid state methods
- Electroplating / Electroforming: A solution containing metal ions loaded with reinforcing particles is co-deposited forming a composite material.
- Stir casting: Discontinuous reinforcement is stirred into molten metal, which is allowed to solidify.
- Squeeze casting: Molten metal is injected into a form with fibers preplaced inside it.
- Spray deposition: Molten metal is sprayed onto a continuous fiber substrate.
- Reactive processing: A chemical reactionChemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
occurs, with one of the reactants forming the matrix and the other the reinforcement.
Vapor deposition
- Physical vapor depositionPhysical vapor depositionPhysical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
: The fiber is passed through a thick cloud of vaporized metal, coating it.
In situ fabrication technique
- Controlled unidirectional solidification of a eutectic alloy can result in a two-phase microstructure with one of the phases, present in lamellar or fiber form, distributed in the matrix.
Applications
- Carbide drillDrillA drill or drill motor is a tool fitted with a cutting tool attachment or driving tool attachment, usually a drill bit or driver bit, used for drilling holes in various materials or fastening various materials together with the use of fasteners. The attachment is gripped by a chuck at one end of...
s are often made from a tough cobaltCobaltCobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
matrix with hard tungsten carbideTungsten carbideTungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
particles inside. - Some tank armors may be made from metal matrix composites, probably steel reinforced with boron nitrideBoron nitrideBoron nitride is a chemical compound with chemical formula BN, consisting of equal numbers of boron and nitrogen atoms. BN is isoelectronic to a similarly structured carbon lattice and thus exists in various crystalline forms...
. Boron nitride is a good reinforcement for steel because it is very stiff and it does not dissolve in molten steel. - Some automotiveAutomobileAn automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
disc brakeDisc brakeThe disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion.A brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or...
s use MMCs. Early Lotus EliseLotus EliseThe 1996 Lotus Elise weighed . Because of its relatively low weight, it was able to accelerate 0- in 5.8 seconds despite its relatively low power output of...
models used aluminum MMC rotors, but they have less than optimal heat properties and Lotus has since switched back to cast-iron. Modern high-performance sport cars, such as those built by PorschePorschePorsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....
, use rotors made of carbon fiber within a silicon carbide matrix because of its high specific heat and thermal conductivity. 3M3M3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
sells a preformed aluminum matrix insert for strengthening cast aluminum disc brake calipers http://www.3m.com/market/industrial/mmc/brake_caliper.html, allowing them to weigh as much as 50% less while increasing stiffness. 3M has also used alumina preforms for AMC pushrods. - Ford offers a Metal Matrix Composite (MMC) driveshaftDriveshaftA drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
upgrade. The MMC driveshaft is made of an aluminum matrix reinforced with boron carbideBoron carbideBoron carbide is an extremely hard boron–carbon ceramic material used in tank armor, bulletproof vests, and numerous industrial applications...
, allowing the critical speed of the driveshaft to be raised by reducing inertia. The MMC driveshaft has become a common modification for racers, allowing the top speed to be increased far beyond the safe operating speeds of a standard aluminum driveshaft. - HondaHondais a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...
has used aluminum metal matrix composite cylinder liners in some of their engines, including the B21A1Honda B20A enginePartially unrelated to the Honda B-series engines are the B20A and B21A. By some , these are not considered to be part of the B-series group of engines because they are not compatible with most of the other B-series parts and all of the other B series chassis.There were 2 versions of the B20A* The...
, H22A and H23AHonda H engineThe Honda H engine was Honda's high-performance engine family from the 1990s and early 2000s. It is largely derived from the Honda F engine with which it shares many design features. Like Honda's other 4-cylinder families of the 80s and 90s, it was replaced by the Honda K engine...
, F20C and F22CHonda F20C engineThe F20C and F22C1 are inline-4 engines produced by Honda. They are one of the few Honda 4-cylinder automobile engines that are designed to sit longitudinally for rear wheel drive....
, and the C32BHonda C engineHonda's first production V6 was the C series; it was produced in displacements from 2.0 liters to 3.5 liters. The C engine was produced in various forms for over 20 years...
used in the NSXHonda NSXThe Honda NSX, or Acura NSX, is a sports car that was produced between 1990 and 2005 by the Japanese automaker Honda. It is equipped with a mid-engine, rear-wheel drive layout, powered by an all-aluminium V6 gasoline engine featuring Honda's Variable Valve Timing and Lift Electronic Control ...
. - Toyota has since used metal matrix composites in the YamahaYamahaYamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...
-designed 2ZZ-GE engine which is used in the later Lotus Lotus Elise S2 versions as well as Toyota car models, including the eponymous Toyota MatrixToyota MatrixThe Toyota Matrix, sometimes officially referred to as the Toyota Corolla Matrix, is a compact hatchback manufactured by the Toyota Motor Corporation in Canada, to be sold in the United States, Canada, and Mexico...
. Porsche also uses MMCs to reinforce the engine's cylinder sleeves in the BoxsterPorsche BoxsterThe Porsche Boxster is a mid-engined roadster built by Porsche. The Boxster is Porsche's first road vehicle to be originally designed as a roadster since the 550 Spyder....
and 911Porsche 911The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
. - The F-16 Fighting FalconF-16 Fighting FalconThe General Dynamics F-16 Fighting Falcon is a multirole jet fighter aircraft originally developed by General Dynamics for the United States Air Force . Designed as an air superiority day fighter, it evolved into a successful all-weather multirole aircraft. Over 4,400 aircraft have been built since...
uses monofilament silicon carbide fibers in a titanium matrix for a structural component of the jet's landing gearLanding GearLanding Gear is Devin the Dude's fifth studio album. It was released on October 7, 2008. It was his first studio album since signing with the label Razor & Tie. It features a high-profile guest appearance from Snoop Dogg. As of October 30, 2008, the album has sold 18,906 copies.-Track...
. - Specialized BicyclesSpecialized Bicycle ComponentsSpecialized Bicycle Components, more commonly known simply as Specialized, is a major American brand of bicycles and related products. It was founded in 1974 by Mike Sinyard and is based in Morgan Hill, California-History:...
has used aluminum MMC compounds for its top of the range bicycleBicycleA bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
frames for several years. Griffen Bicycles also makes boron carbide-aluminum MMC bike frames, and UnivegaUnivegaUnivega is a brand of bicycles, created during the bike boom of the 1970s by Ben Lawee , who founded Lawee Inc. to design, specify, and import bicycles initially manufactured in Italy by Italvega, and subsequently in Japan by Miyata....
briefly did so as well. - Some equipment in particle acceleratorParticle acceleratorA particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s such as Radio Frequency Quadrupoles (RFQs)Radio Frequency QuadrupoleA radio frequency quadrupole is a linear accelerator component generally used at low beam energies, roughly 50keV to 3MeV...
or electron targets use copper MMC compounds such as GlidcopGlidcopGlidcop is the registered trademark name of SCM Metal Products, Inc. that refers to a family of copper-based metal matrix composite alloys mixed primarily with aluminum oxide ceramic particles...
to retain the material properties of copper at high temperatures and radiation levels. - CopperCopperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
-silverSilverSilver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
alloy matrix containing 55 vol.% diamondDiamondIn mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
particles, known as DymalloyDymalloyDymalloy is a metal matrix composite consisting of 20% copper and 80% silver alloy matrix with type I diamond. It has very high thermal conductivity of 420 W/, and its thermal expansion can be adjusted to match other materials, e.g. silicon and gallium arsenide chips...
, is used as a substrate for high-power and high density multi-chip moduleMulti-Chip ModuleA multi-chip module is a specialized electronic package where multiple integrated circuits , semiconductor dies or other discrete components are packaged onto a unifying substrate, facilitating their use as a single component...
s in electronics for its very high thermal conductivity.
MMCs are nearly always more expensive than the more conventional materials they are replacing. As a result, they are found where improved properties and performance can justify the added cost. Today these applications are found most often in aircraft components, space systems
Space technology
Space technology is technology that is related to entering, and retrieving objects or life forms from space."Every day" technologies such as weather forecasting, remote sensing, GPS systems, satellite television, and some long distance communications systems critically rely on space infrastructure...
and high-end or "boutique" sports equipment. The scope of applications will certainly increase as manufacturing costs are reduced.
In comparison with conventional polymer matrix composites, MMCs are resistant to fire, can operate in wider range of temperatures, do not absorb moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
, have better electrical and thermal conductivity, are resistant to radiation damage
Radiation damage
Radiation damage is a term associated with ionizing radiation.-Causes:This radiation may take several forms:*Cosmic rays and subsequent energetic particles caused by their collision with the atmosphere and other materials....
, and do not display outgassing
Outgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...
. On the other hand, MMCs tend to be more expensive, the fiber-reinforced materials may be difficult to fabricate, and the available experience in use is limited.
See also
- Advanced composite materialsAdvanced composite materials (science & engineering)Advanced composite materials are also known as Advanced polymer matrix composites. These are generally characterized or determined by unusually high strength fibres with unusually high stiffness, or modulus of elasticity characteristics, compared to other materials, while bound together by...
- Babbitt (metal)