A metal matrix composite (MMC) is a type of 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. Composite materials (or composites for short) are engineered materials made from two or more constituent materials that remain separate and distinct on a macroscopic level while forming a single component. ... Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) surrounded by a sea of delocolised... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικος (keramikos, having to do with pottery). The term covers inorganic non-metallic materials whose formation is due to the action of heat. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... A Cermet is a composite material composed of ceramic (cer) and metallic (met) materials. ...

Composition

Each part of the material is either the matrix or a reinforcement. The reinforcement surface can be coated to prevent a chemical reaction with the matrix.

Matrix

The matrix is the "frame" 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. The matrix is usually a lighter metal such as aluminum, magnesium, or titanium, and provides a compliant support for the reinforcement. Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Atomic mass 47. ...

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, friction coefficient, or thermal conductivity. The reinforcement can be either continuous, or discontinuous. Discontinuous MMCs are isotropic, and can be worked with standard metalworking techniques. Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. ... In physics, thermal conductivity, λ or k, is the intensive property of a material which relates its ability to conduct heat. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ...

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. Carbon fiber composite is a strong, light and very expensive material. ... Silicon carbide (SiC), also known as moissanite, is a ceramic compound of silicon and carbon. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Atomic mass 10. ...

Manufacturing and forming methods

MMC manufacturing can be broken into three types: solid, liquid, and vapor.

Solid state methods

• Powder blending and consolidation (Powder Metallurgy): Powdered metal and dicontinuous reinforcement are mixed and then bonded through a process of compaction, degassing, and thermo-mechanical treatment (possibly via hot isostatic pressing (HIP) or extrusion).
• Foil diffusion bonding: Layers of metal foil are sandwiched with long fibers, and then pressed through to form a matrix.

Liquid state methods

• 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 reaction occurs, with one of the reactants forming the matrix and the other the reinforcement.

Vapor deposition A chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ...

• Physical Vapor Deposition: The fiber is passed through a thick cloud of vaporized metal, coating it. [1]

Applications

• Carbide drills are often made from a soft cobalt matrix with tough tungsten carbide particles inside.
• Some tank armors may be made from metal matrix composites, probably steel reinforced with boron nitride. Boron nitride is a good reinforcement for steel because it is very stiff and it does not dissolve in molten steel.
• Some automotive disc brakes use MMCs. Early Lotus Elise 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 Porsche, use rotors made of carbon fiber within a silicon carbide matrix because of its high specific heat and thermal conductivity. 3M sells a preformed aluminum matrix insert for strengthening cast aluminum disc brake calipers [2], allowing them to weigh as much as 50% less while increasing stiffness.
• Toyota has since used metal matrix composites in the 2ZZ-GE engine block, and the Porsche Boxster and 911 use MMCs to reinforce the engine's cylinder sleeves. (Lotus uses the 2ZZ-GE in later Elise S2 versions). The 2ZZ-GE engine is actually designed and built by Yamaha, as were the Iron-block Toyota 4A-GE, etc. Prior, Honda had already used Aluminum MMC in its high-performance engine blocks such as the H22 and later the K20.
• The F-16 Fighting Falcon uses monofilament silicon carbide fibres in a titanium matrix for a structural component of the jet's landing gear.
• Specialized Bicycles have used aluminium MMC compounds for their top of the range bicycle frames for several years.

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. A drill is a tool with a rotating drill bit used for drilling holes in various materials. ... Tungsten carbide, WC or W2C, is a chemical compound containing tungsten and carbon, similar to titanium carbide. ... Boron nitride is a binary chemical compound, consisting of equal proportions of boron and nitrogen, with formula BN. Structurally, it is isoelectronic to carbon and takes on similar physical forms: a hexagonal, graphite-like one, and a cubic, diamond-like one. ... An automobile is a wheeled vehicle that carries its own motor. ... Close-up of a disc brake on a car On automobiles, disc brakes are often located within the wheel The disc brake is a device for slowing or stopping the rotation of a wheel. ... The Lotus Elise The Lotus Elise is a roadster conceived in early 1994 and released in September 1995 by the English manufacturer Lotus Car. ... A Honda NSX sports car A TVR Tuscan sports car A sports car is a car designed for sporting performance above utility. ... Porsche (), properly pronounced as a two syllable word (porsh-eh, IPA: ) , is a German manufacturer of sports cars, founded in 1931 by Ferdinand Porsche, the engineer who created the first Volkswagen. ... Carbon fiber composite is a strong, light and very expensive material. ... In physics, thermal conductivity, λ or k, is the intensive property of a material which relates its ability to conduct heat. ... This article is about the American company, for the Russian company involved in a pyramid scheme, see MMM (pyramid) 3M Company NYSE: MMM (formerly Minnesota Mining and Manufacturing Company until 2002) is an American corporation with a worldwide presence that produces over 55,000 products, including adhesives, abrasives, laminates, electronic... The Porsche Boxster is a convertible sports car released in late 1996. ... Porsche 911 A 1973 Porsche 911 Carrera RS The Porsche 911 is a sports car made by Porsche AG of Stuttgart, Germany. ... F-16 Fighting Falcon over Iraq The F-16 Fighting Falcon is a modern multi-role jet fighter aircraft designed in the United States. ... Specialized Bicycle Components is a major manufacturer of bicycles and bicycle equipment, based in Morgan Hill, California. ... This racing bicycle is built using lightweight, shaped aluminium tubing and carbon fiber stays and forks. ...

See also

• organic matrix composite
• cermet

A Cermet is a composite material composed of ceramic (cer) and metallic (met) materials. ...

External links

• Closeup photos of MMCs
• Assessment of Metal Matrix Composites for Innovations
• Space application of MMCs