Metal matrix composite

Say the same using the Infinitives to shorten the phrases.

Model: If the processing requires to force out any air bubbles fromthemoulded mass engineers can apply pressure. –Pressure can be applied to force out any air bubbles / engineers can apply pressure to force out air bubbles from the moulded mass)

1. If the processing requires to force out any air bubbles from the molten mass engineers can apply pressure. 2. The main target of specialists is to produce composite materials with unique properties. That’s why they make different materialswork together. 3. The matrixmaterial for specific purposes must be softened and only then it can beshaped with tools.4. Ifwe want to repair such a composite it can be softened by suitable solvents. 5. The properties of composites are to meet specific requirements, so technologists try to tailor some of them. 6. One of the numerous tasks is to create the composite sheet which is very strong in one direction. Specialists manage it by aligning the fibres in a certain direction. 7. If the composite is to be exposed to high temperatures ceramics is often used for this purpose. 8. Technologists are tochoose an appropriate combination of reinforcement and matrix material if they need that material would fit exactly the requirements for a particular purpose.

20. Read the text without a dictionary using only the notes given below. Decide which parts of the text is possible to title as:

a) The composition of metal matrix composite

b) Reinforcement and its types

c) The types of manufacturing and forming methods

d) Matrix)

e) The application of the metal matrix composites

f) The definition ofa metal matrix composite

1. 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.

2. 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.

3. 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.

4. 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.

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.

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

Solid type implies powder blending and consolidation when powdered metal and dicontinuous reinforcement are mixed and then bonded through a process of compaction, air extraction and heating (possibly via hot isostatic pressing (HIP) or extruding). Foil diffusion bonding is the type manufacture in the processing of which layers of metal foil are sandwiched with long fibers, and then melted through to form a matrix.

Liquid type in turn is divided into stir casting. Stir casting employs discontinuous reinforcement stirred into molten metal which is allowed to solidify. Another liquid types include squeeze casting (molten metal is injected into a form with fibers preplaced inside it) and spray deposition (molten metal is sprayed onto a continuous fiber substrate). Recently due to advanced technologies one more promising method has appeared. It’s reactive processing when a chemical reaction occurs with one of the reactants forming the matrix and the other the reinforcement.

Physical vapor deposition is one of the latest methods. The fiber is passed through a thick cloud of vaporized metal, coating it.

6. 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. Thus the F-16 Fighting Falcon uses monofilament silicon carbide fibres in a titanium matrix for a structural component of the jet's landing gear. It is the imposing cost that allows MMCs to be used in high-end or "boutique" sports equipment. 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, allowing them to weigh as much as 50% less while increasing stiffness. Lotus Elise models have 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. It goes without saying that military industry engineers employ all the properties to improve military technique. 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. Carbide drills are often made from a soft cobalt matrix with tough tungsten carbide particles inside. The scope of applications will certainly increase as manufacturing costs are reduced.

Notes to the text:

1. to embed – укладывать, укреплять

2. compliant – податливый

3. filament – нитевидное волокно

4. foil – фольга

5. squeeze casting – литье под давлением

6.landing gear – передача/привод, используемые при приземлении

7. disc brake calipers – колодки дискового тормоза

8. sleeve – муфта, втулка

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