**1. Introduction**

The choice of the right materials is an arduous engineering challenge to the materials engineer and, if done carefully, can be a springboard to the proper and successful implementation and subsequent operation of the design. There are a host of materials available to the designer, and making the right decision is a vital achievement in putting forth a successful design. Materials are required to perform according to the designer's expectations and must possess and retain the right properties in the working environment throughout the working period.

Material selection is in most cases a contradictory decision-making process. Light-weight materials will most likely not possess sufficient strength, and brittle materials will not necessarily be good in fatigue resistance, stiffness or toughness. It is also almost impossible to find a single monolithic material with the required property profile for engineering applications. Moreover, material properties are greatly affected by the working environment (such as temperature, pressure, humidity, etc.) and the nature of loading (gradual, fluctuating, impact, fatigue, etc.). There is need, therefore, to combine two or more materials, as alloys or composites so as to utilise the different useful properties offered by the different materials. Most engineering materials appear in this configuration, and very few applications utilise pure monolithic materials [1]. This is true of aluminium, the most abundant metallic element in the Earth's crust, accounting for 8% of the planet's soil and rocks. Aluminium has been a metal of tremendous importance to the domestic and manufacturing industries from the mediaeval period (fifth–fifteenth century) and played an important role in the early years of the industrial revolution. The successful extraction and the first commercial applications of aluminium took place in the nineteenth century, the period in which the enthusiasm for new materials and their possible uses was immense [2].

The first mention of aluminium as a metal of industrial importance indicated the metal was first utilised in the manufacture of household and ornamental items before becoming an important material in the construction of large industrial structures and machine components. With the advent of alloying technology, the use of aluminium was developed farther and positioned aluminium as the most utilised industrial metal for decades. The popularity of aluminium grew due to its good attributes related to its unique properties, mainly of light-weight combined with good thermal/electrical conduction and reasonably good strength and resistance to corrosion. With alloying, aluminium has found more applications than previously envisioned, making aluminium a serious competitor with (and sometimes a preferred alternative to) the traditional "strong" metals iron and steel [3].

Aluminium alloys and composites have, in most applications, exhibited superior performance compared to their rival metals. The choice of aluminium alloys and composites derives from one important attribute of aluminium metal—lightweight. Light-weight translates into many important outcomes in engineering applications. In the automotive industry, it means less dead weight, lower fuel consumption, lower emissions, increased payload (for passengers and cargo) and easier handling. In the aerospace and aircraft industry, it translates into more payload (cargo), less fuel and lower emissions. There are similar advantages in all areas where aluminium is utilised—marine, rail, packaging, thermal management, building and construction, sports and recreation, etc. Aluminium's good electrical and thermal conductivity have seen its increased use in electrical conductors, electronic packaging and thermal management. Nowadays, aluminium is viewed as an important material for energy conservation and environmental protection [4].

Modern technology aims at meeting the market whose standards are ever appreciating. The market demands faster, more comfortable and hassle-free transport, more compact and lighter machines and tools, more efficient methods of power generation, etc. Most engineered materials can easily meet or surpass design specifications that would not have been envisaged a few years back. Today's materials are subjected to more critical loads, more stresses and more severe operating conditions in an environment never experienced before. In a spacecraft, for example, the operating conditions experienced are quite unique and require special types of materials to withstand the severe stresses imposed on the spacecraft during take-off and maintenance in the orbiting space. Traditional materials have been found wanting in meeting these operating conditions and hence the need to intensify research and development (R&D) efforts in new and advanced materials for specific applications and efficiency improvement. Among the advanced materials on the R&D, the menu is the metal matrix micro- and nanocomposites. Metal matrix composites (MMCs) are metals or metal alloys that incorporate particles, whiskers, fibres or hollow microballoons made of a different material and offer unique opportunities to tailor materials to specific design needs [5]. In automotive applications, for example, these materials can be tailored to be light-weight and with various other useful properties including high specific strength and specific stiffness, high hardness and wear resistance, high thermal conductivity, high energy absorption and a damping capacity and low coefficients of friction and thermal expansion.

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*Novel Applications of Aluminium Metal Matrix Composites*

specified properties by the use of these techniques [1].

**2.1 An overview of metal matrix composites**

moduli, strengths and good ductility [6].

tion due to the lattice arrangement of their atoms [8].

MMCs, therefore, offer more possibilities for wider applications of materials by manipulating their processing to suit the requisite properties under different working environments. The design of composite materials with specific properties can, moreover, be accomplished with the use of finite element modelling techniques. It is possible to predict the properties of a certain material of specified composition by using these techniques. In the same way, it is possible to design materials to offer

**2. Types of metal matrix composites and their methods of production**

A composite is a mixture of two or more constituents or phases which are chemically distinct on a microscopic scale, separated by a distinct interface, and can easily be specified. In addition, other criteria are normally satisfied before a material can be called a composite. The constituents have to be present in reasonable proportions, and the constituent phases should have distinctly different properties, such that the properties of the composite are noticeably different from the properties of the constituents [4]. The constituent which is continuous and in most cases available in larger quantities is termed the *matrix*. It is commonly viewed that it is the properties of the matrix that are improved upon in the process of producing a composite. The second constituent is known as the reinforcing phase, or *reinforcement*, as it enhances or reinforces the mechanical properties of the matrix. In most cases the reinforcement is harder, stronger and stiffer than the matrix, although there are some exceptions. The matrix may be in form of a ceramic material, metallic or polymeric, with each of these three classes of materials having considerably different /unique mechanical properties. Generally, polymers have low Young's moduli and strengths; ceramics are strong, stiff and brittle; and metals have intermediate

Composite materials are usually classified according to the physical or chemical nature of the matrix, e.g. metal matrix, polymer matrix and ceramic composites. Additionally, the emergence of the intermetallic matrix and carbon matrix composites as reported by [7] has broadened the scope of composites. Intermetallic compounds are metal-based systems centred on the fixed atomic compositions occurring in metallic systems of aluminium with nickel (Ni), titanium (Ti) and niobium (Nb), such as Ni3Al, Ti3Al, TiAl and Nb3Al. Intermetallic compounds are of interest because they often exhibit higher melting points and less ease of deforma-

In certain applications, metal matrix composite materials, formed by combining two or more materials—one of which is a metal—exhibit a primary advantage over their counterpart organic matrix composites in regard to the maximum operating temperature. To support this point, [9] reports that the boron/aluminium composite offers useful mechanical properties up to a temperature of 510°C, whereas an equivalent boron/epoxy composite is limited to about 190°C. Furthermore, composites of graphite/aluminium, graphite/copper and graphite/magnesium exhibit higher thermal conductivity due to the significant contribution from the metallic matrix. A metal matrix composite retains the desirable properties of both the matrix and the reinforcement by combining the strength of its reinforcement with the ductility of its matrix [10]. The reinforcing constituent may be a particle, platelet, short fibre or continuous fibre and may range from sub-micrometre to millimetre in size. There is a difference between metal matrix composites and multiphase metallic alloys as the concept of MMCs introduces additional degrees of

*DOI: http://dx.doi.org/10.5772/intechopen.86225*

different useful properties offered by the different materials. Most engineering materials appear in this configuration, and very few applications utilise pure monolithic materials [1]. This is true of aluminium, the most abundant metallic element in the Earth's crust, accounting for 8% of the planet's soil and rocks. Aluminium has been a metal of tremendous importance to the domestic and manufacturing industries from the mediaeval period (fifth–fifteenth century) and played an important role in the early years of the industrial revolution. The successful extraction and the first commercial applications of aluminium took place in the nineteenth century, the period in which the enthusiasm for new materials and their possible uses was immense [2]. The first mention of aluminium as a metal of industrial importance indicated the metal was first utilised in the manufacture of household and ornamental items before becoming an important material in the construction of large industrial structures and machine components. With the advent of alloying technology, the use of aluminium was developed farther and positioned aluminium as the most utilised industrial metal for decades. The popularity of aluminium grew due to its good attributes related to its unique properties, mainly of light-weight combined with good thermal/electrical conduction and reasonably good strength and resistance to corrosion. With alloying, aluminium has found more applications than previously envisioned, making aluminium a serious competitor with (and sometimes a pre-

ferred alternative to) the traditional "strong" metals iron and steel [3].

Aluminium alloys and composites have, in most applications, exhibited superior performance compared to their rival metals. The choice of aluminium alloys and composites derives from one important attribute of aluminium metal—lightweight. Light-weight translates into many important outcomes in engineering applications. In the automotive industry, it means less dead weight, lower fuel consumption, lower emissions, increased payload (for passengers and cargo) and easier handling. In the aerospace and aircraft industry, it translates into more payload (cargo), less fuel and lower emissions. There are similar advantages in all areas where aluminium is utilised—marine, rail, packaging, thermal management, building and construction, sports and recreation, etc. Aluminium's good electrical and thermal conductivity have seen its increased use in electrical conductors, electronic packaging and thermal management. Nowadays, aluminium is viewed as an important material for energy conservation and environmental protection [4]. Modern technology aims at meeting the market whose standards are ever appreciating. The market demands faster, more comfortable and hassle-free transport, more compact and lighter machines and tools, more efficient methods of power generation, etc. Most engineered materials can easily meet or surpass design specifications that would not have been envisaged a few years back. Today's materials are subjected to more critical loads, more stresses and more severe operating conditions in an environment never experienced before. In a spacecraft, for example, the operating conditions experienced are quite unique and require special types of materials to withstand the severe stresses imposed on the spacecraft during take-off and maintenance in the orbiting space. Traditional materials have been found wanting in meeting these operating conditions and hence the need to intensify research and development (R&D) efforts in new and advanced materials for specific applications and efficiency improvement. Among the advanced materials on the R&D, the menu is the metal matrix micro- and nanocomposites. Metal matrix composites (MMCs) are metals or metal alloys that incorporate particles, whiskers, fibres or hollow microballoons made of a different material and offer unique opportunities to tailor materials to specific design needs [5]. In automotive applications, for example, these materials can be tailored to be light-weight and with various other useful properties including high specific strength and specific stiffness, high hardness and wear resistance, high thermal conductivity, high energy absorption and a damping capacity and low coefficients of friction and thermal expansion.

**72**

MMCs, therefore, offer more possibilities for wider applications of materials by manipulating their processing to suit the requisite properties under different working environments. The design of composite materials with specific properties can, moreover, be accomplished with the use of finite element modelling techniques. It is possible to predict the properties of a certain material of specified composition by using these techniques. In the same way, it is possible to design materials to offer specified properties by the use of these techniques [1].
