What is Materials Sicence and Engineering

 Materials Science and Engineering is an interesting, multidisciplinary area to study

In studying materials, there are elements of physics, mathematics, biology and chemistry, all taught in a cohesive, and self-contained way within the course. This makes for a varied and stimulating experience, giving you the tools to make a real difference in industry and research. Some of the themes prominent at the moment are biomaterials, nanomaterials, advanced manufacturing, smart materials, composites, energy generation and storage, green and sustainable materials.

There are lots of jobs in the area of Materials Science and Engineering

The ability to create new materials and to make existing materials perform better is the key to many advances in areas of science and engineering, be it in industry or research organisations. There are smaller numbers of materials graduates than other disciplines which, combined with a strong need from industry and research for these people, means that most of our students get good jobs in their final year.

1.1 HISTORICAL PERSPECTIVE

Materials are probably more deep-seated in our culture than most of us realize.

Transportation, housing, clothing, communication, recreation, and food production—

virtually every segment of our everyday lives is influenced to one degree or another

by materials. Historically, the development and advancement of societies have been

intimately tied to the members’ ability to produce and manipulate materials to fill

their needs. In fact, early civilizations have been designated by the level of their

materials development (Stone Age, Bronze Age, Iron Age).1

The earliest humans had access to only a very limited number of materials,

those that occur naturally: stone, wood, clay, skins, and so on. With time they discovered techniques for producing materials that had properties superior to those

of the natural ones; these new materials included pottery and various metals. Furthermore, it was discovered that the properties of a material could be altered by

heat treatments and by the addition of other substances. At this point, materials utilization was totally a selection process that involved deciding from a given, rather

limited set of materials the one best suited for an application by virtue of its characteristics. It was not until relatively recent times that scientists came to understand

the relationships between the structural elements of materials and their properties.

This knowledge, acquired over approximately the past 100 years, has empowered

them to fashion, to a large degree, the characteristics of materials.Thus, tens of thousands of different materials have evolved with rather specialized characteristics that

meet the needs of our modern and complex society; these include metals, plastics,

glasses, and fibers.

The development of many technologies that make our existence so comfortable has been intimately associated with the accessibility of suitable materials.

An advancement in the understanding of a material type is often the forerunner to the stepwise progression of a technology. For example, automobiles

would not have been possible without the availability of inexpensive steel or

some other comparable substitute. In our contemporary era, sophisticated electronic devices rely on components that are made from what are called semiconducting materials.

1.2 MATERIALS SCIENCE AND ENGINEERING

Sometimes it is useful to subdivide the discipline of materials science and engineering into materials science and materials engineering subdisciplines. Strictly

speaking, “materials science” involves investigating the relationships that exist

between the structures and properties of materials. In contrast, “materials engineering” is, on the basis of these structure–property correlations, designing or engineering the structure of a material to produce a predetermined set of properties.2

From a functional perspective, the role of a materials scientist is to develop or synthesize new materials, whereas a materials engineer is called upon to create new

products or systems using existing materials, and/or to develop techniques for processing materials. Most graduates in materials programs are trained to be both

materials scientists and materials engineers.

“Structure” is at this point a nebulous term that deserves some explanation. In

brief, the structure of a material usually relates to the arrangement of its internal

components. Subatomic structure involves electrons within the individual atoms and

interactions with their nuclei. On an atomic level, structure encompasses the organization of atoms or molecules relative to one another. The next larger structural

realm, which contains large groups of atoms that are normally agglomerated together, is termed “microscopic,” meaning that which is subject to direct observation

using some type of microscope. Finally, structural elements that may be viewed with

the naked eye are termed “macroscopic.”

The notion of “property” deserves elaboration. While in service use, all materials are exposed to external stimuli that evoke some type of response. For example, a specimen subjected to forces will experience deformation, or a polished metal

surface will reflect light. A property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus. Generally, definitions of properties are made independent of material shape and size.

Virtually all important properties of solid materials may be grouped into six different categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative.

For each there is a characteristic type of stimulus capable of provoking different responses. Mechanical properties relate deformation to an applied load or force; examples include elastic modulus and strength. For electrical properties, such as electrical

conductivity and dielectric constant, the stimulus is an electric field. The thermal behavior of solids can be represented in terms of heat capacity and thermal conductivity. Magnetic properties demonstrate the response of a material to the application of

a magnetic field. For optical properties, the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties. Finally,

deteriorative characteristics relate to the chemical reactivity of materials.The chapters

that follow discuss properties that fall within each of these six classifications.

In addition to structure and properties, two other important components are

involved in the science and engineering of materials—namely, “processing” and

“performance.”With regard to the relationships of these four components, the structure of a material will depend on how it is processed. Furthermore, a material’s performance will be a function of its properties. Thus, the interrelationship between

processing, structure, properties, and performance is as depicted in the schematic

illustration shown in Figure 1.1. Throughout this text we draw attention to therelationships among these four components in terms of the design, production, and

utilization of materials

1.3 WHY STUDY MATERIALS SCIENCE

AND ENGINEERING?

Why do we study materials? Many an applied scientist or engineer, whether mechanical, civil, chemical, or electrical, will at one time or another be exposed to a

design problem involving materials. Examples might include a transmission gear,

the superstructure for a building, an oil refinery component, or an integrated circuit

chip. Of course, materials scientists and engineers are specialists who are totally

involved in the investigation and design of materials.

Many times, a materials problem is one of selecting the right material from the

many thousands that are available. There are several criteria on which the final

decision is normally based. First of all, the in-service conditions must be characterized, for these will dictate the properties required of the material. On only rare

occasions does a material possess the maximum or ideal combination of properties.

Thus, it may be necessary to trade off one characteristic for another. The classic example involves strength and ductility; normally, a material having a high strength

will have only a limited ductility. In such cases a reasonable compromise between

two or more properties may be necessary.

A second selection consideration is any deterioration of material properties that

may occur during service operation. For example, significant reductions in mechanical

strength may result from exposure to elevated temperatures or corrosive environments.

Finally, probably the overriding consideration is that of economics: What will

the finished product cost? A material may be found that has the ideal set of properties but is prohibitively expensive. Here again, some compromise is inevitable.

The cost of a finished piece also includes any expense incurred during fabrication

to produce the desired shape.

The more familiar an engineer or scientist is with the various characteristics

and structure–property relationships, as well as processing techniques of materials,

the more proficient and confident he or she will be to make judicious materials

choices based on these criteria.