Metal Matrix Composite Research Assignment Paper (Essay Sample)

Metal Matrix Composite
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Abstract
The existing raw materials are wearing off in nature and even those that exist in abundance are losing their interest to engineers. This is because engineers are moving to better attractive materials that suit their purpose. These materials are inclusive of metal matrix composite. In particular, applications of MMCs, this article highlights the automobile field, power electronics, tank armors and cutting tools. MMCs are compared to other materials in terms of their properties and production processes. An analysis on the experiment carried out to select the best material for brake disc have been done on this booklet and it proves that MMCs are good materials for that application.
Introduction
Metal matrix composite is a material in which a metal is combined with another, either metallic or nonmetallic material, phases to produce a composite metal with specific desired mechanical and metallurgical properties. It consists of a metal matrix reinforced by a second phase such as particles of ceramics and fibers of various materials, including other ceramics, metals, boron and carbon. These types of additives phases used will make the metal matrix composite to be classified into cermet or fiber-reinforced metallic matrix composites and continuous reinforcement metallic matrix.
Cermet is a composite in which ceramic is used as the second phase in combination with the metal to form a metallic matrix. Ceramic forms the main phase of the mixture ranging up to ninety-six percent by volume. Cermet is divided further into cemented carbide and oxide-based cermet. Concreted carbides are encompassed of carbide combined with a metallic matrix. The most common type is tungsten carbide and chromium carbide. The major metallic bounders are nickel used for chromium carbide and cobalt for tungsten carbide, produced by particulate processing techniques. CITATION Gro \p 50 \l 1033 (Groover, p. 50)
According to CITATION Gro \l 1033 (Groover)fiber-reinforced metallic matrix composites combine the high tensile strength and modulus of elasticity of a fiber with metals of low density. The combinations helps in achieving a good strength-to-weight and modulus-to-weight ratios in the metal matrix composite formed. The metals used with low density are titanium and aluminum for example, whereas those sued for fiber are oxide of aluminum, carbon fibers and silicon just to mention a few. CITATION Joh \l 1033 (Kerns & Colella, 2008).
Thirdly, continuous reinforcement include magnesium composite, filament wound, carbon fiber and woven carbon fiber cloth reinforced aluminum alloys. Three or more constituents can form the metal matrix in order to improve the properties further. This kind of metal composite is referred to as hybrid composite metal matrix. The reinforcement materials and alloy mixtures can vary regarding to the applications and the suppliers of this materials do specify this specifications.
Generally, metal matrix composites are light in weight but have good mechanical properties that make them high performance materials, thereby attracting industrial applications. The structural and functional of these materials can be can be altered to meet the specific industrial application. For instance, these materials are easy to machine and attracts the application of new technologies like Hybrid electric discharge machining process. This makes the metal matrix composite materials to exhibits higher capability for machining complex shapes with highest precision and accuracy. CITATION Ade11 \l 1033 (Adebisi, Maleque, & Rahman, 2011).
The metallic part of the metal matrix composite, such as copper and aluminum, provides the toughness, which prevent the early failure and crack formation and propagation. Whereas, the nonmetallic part like ceramics, provides the hardness, oxidation resistance and erosion resistance properties into the composite. It also provides high thermal conductivity, which increase the life of the tools.
Metal Matrix Composite Properties
When an additive of different phase is added to a metal, it imparts its properties like softening, hardening, toughening and strengthening among others. For MMC, ceramics are usually added to the metal phase to alter the physical, mechanical and chemical properties of metals, in order to meet the specifically required property. The additives alter the metallurgical organizations of the grains hence changing their behavior. Some of the properties selected for this research include the high thermal deformation resistance, low fatigue resistance, high strength, fires resistance and no moisture absorptions. Some of the reinforcing materials’ mechanical properties are illustrated in the table below:
Table 1: illustrates the various reinforcing materials used in MMC and the corresponding properties. These properties will be reflected on the matrix of the composites formed.CITATION Mar06 \p 186 \l 1033 (Martin, 2006, p. 186) .
Fatigue: When MMC are subjected to fluctuating stresses and strains, they resist fracture. To counter this limitation of a metal, a material phase that is fatigue resistant is introduced into the metal matrix, which imparts its properties in the process thereby forming an improved metal alloy.
Application of Metal Matrix Composite
They are used as a cutting tool. Cutting tools require special properties such as better hardness, high strength, wear resistance, toughness and ability to retards grain growth for better toughness. These properties are inflicted into the metal tool by the addition of a second phase material like a ceramic or carbides and others. Tungsten carbide is an example of normal cutting. Tungsten is used to increase hot hardness and stability of the tool at high temperatures, while the addition of carbon imparts the abrasion and self-lubricating properties. At very high temperatures of up to six hundred degrees Celsius, tungsten carbide decomposes to carbon and tungsten and these constituents are prone to oxidation. Fortunately, the cutting tool rarely reaches this high temperature, because it is used for cutting specific components that cannot raise temperatures to that quantity.
In automotive engineering, metal matrix composites are applied in making the brake discs. The commonly used MMC is the aluminum. CITATION Ade11 \l 1033 (Adebisi, Maleque, & Rahman, 2011). The aluminum MMC have become the most used materials for brake disc as compared to conventional materials. This is because it is light in weight, easy to machine and process thus making it cheaper, and a higher performance brake rotor can be achieved from this composite Aluminum MMC is produced by air casting techniques, that is of major advantageous as compared to conventional techniques. It is a sustainable method that is competitive in comparison to other techniques, easy to operate and do not eat out the quality of brake disc. CITATION MAM10 \l 1033 (M.A. Maleque, 2010)
Some of the material properties desired for a brake disc is illustrated in the table below.
Table 2: This table shows the MMCs with their corresponding mechanical properties as applied to the automobiles brakes. CITATION MAM10 \l 1033 (M.A. Maleque, 2010)
Dymalloy has been used in the power electronics applications. Dymalloy is a metal matrix composite having twenty percent copper and eighty percent silver alloy matrices. Dymalloy has been used in high power packaging having been developed as substrate materials. The main merit of this material is that it has high thermal conductivity, that is approximately double that of the present substrate materials and has a coefficient of thermal expansion that is adjustable to suit the conditions required. All of the above properties are better as compared to the conventional materials like silicon and gallium arsenide. CITATION Joh \l 1033 (Kerns & Colella, 2008)
Among other applications of MMC, boron nitride for instance is used in tank armors. Boron nitride is comparable to diamond in terms of its hardness and is used in making bulletproofs and tank armors because of this major property. It has a Mohs hardness of about 9.5, has a good resistance to acid, refractory and chemically inert but less resistance to oxidation as compared to silicon. These are the main properties that are obtained by combinations of boron metal and other nonmetals, which impart their features in the boron for better mechanical applications like tank armors.
Production of MMCs
Since MMCs can be categorized into those in which metallic matrix are introduced in a solid , particulate form and those in which the metal is melted, it means solid state, liquid state and semi-solid state manufacturing processes are applicable. Hot isostatic pressing, liquid metal techniques, powder metallurgy are the process that can be applied to MMCs materials. CITATION Mar06 \l 1033 (Martin, 2006)
Powder metallurgy is where conventional powder metallurgical techniques is applied in the manufacture of MMCs. Individual phases are mixed together in particulate form, and therefore, the homogeneously mixed powder are pressed in an appropriate mould, forming green compact, to form the shape required. Then the compacted component is sintered at elevated temperatures under pressure to form the final, dense composite. The cutting tools such as tungsten carbide are usually produced by this method. CITATION Mar06 \l 1033 (Martin, 2006)
Hot isostatic squeezing of MM composite is connected to materials contained in emptied jars. Last densification is more often than not by hot extrusion. It is utilized to counter the issue forced by sub-micron particles blended with metal powders by typical powder metallurgical strategies, which makes the particles to tend to group together with a weighty misfortune in properties. The uniform scattering of fine particles are accomplished all the mo...