1. Introduction

Fundamentals of Materials Science and Engineering

About the Photo :

Materials Science and Engineering is similar with the chef. If you want to cook the yummy
cuisine, the raw materials are extremely important, and then the top secret closely-guarded
regime is the most important factor to make the gourmand satisfied. Think about the bomber
B-2 stealthy coating and HY-100 steel used on the aircraft carrier are also closely-guarded
secret.

Content :

1. Introduction
2. Atomic Structure and Interatomic Bonding
3. Structures of Metals and Ceramics
4. Polymer Structures
5. imperfection in Solids
6. Diffusion
7. Mechanical Properties
8. Deformation and Strengthening Mechanisms
9. Failure
10. Phase Diagrams
11. Phase Transformations
12. Electrical Properties
13. Types and Applications of Materials
14. Synthesis, Fabrication, and Processing of Materials
15. Composites
16. Corrosion and Degradation of Materials
17. Thermal Properties
18. magnetic Properties
19. Optical Properties
20. Materials Selection and Design Considerations
21. Economic, Environmental, and Societal Issues in Material Science and Engineering

 A familiar item that is fabricated from three different material types is the beverage
container. Beverages are marketed in aluminum (metal) cans (left), glass (ceramic) bottles
(center), and plastic (polymer) bottles (right).

After careful study of this chapter you should be able to do the following:

1. List six different property classifications of materials that determine their applicability.
2. Cite the four components that are involved in the design, production, and utilization of materials, and briefly describe the interrelationships between these components.
3. Cite three criteria that are important in the materials selection process. 
4. (a) List the three primary classifications of solid materials, and then cite the distinctive chemical feature of each. (b) Note the other three types of materials and, for each, its distinctive feature(s).

 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 (i.e., Stone Age, Bronze Age).

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 is, deciding from a given, rather limited set of materials the one that was 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 in the past 60 years or so, 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

The discipline of 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. Throughout this text we draw attention to the relationships between material properties and structural elements.

‘‘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. 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 indicate 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, viz. ‘‘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 linear, as depicted in the schematic illustration. Throughout this text we draw attention to the relationships among these four components in terms of the design, production, and utilization of materials.

Processing - Structure - Properties - Performance


Maize as the raw material and then different processing can be made for the Doritos or
Popcorn. Basically, the materials in the engineering can be analogized to the food materials,
we divide the food into the cereal, protein, vegetable ...

Photograph showing the light transmittance of three aluminum oxide specimens. From left to right: singlecrystal material (sapphire), which is transparent; a polycrystalline and fully
dense (nonporous) material, which is translucent; and a polycrystalline material that contains approximately 5% porosity, which is opaque.

It is obvious that the optical properties (i.e., the light transmittance) of each of the three materials are different; the one on the left is transparent (i.e., virtually all of the reflected light passes through it), whereas the disks in the center and on the right are, respectively, translucent and opaque. All of these specimens are of the same material, aluminum oxide, but the leftmost
one is what we call a single crystal—that is, it is highly perfect—which gives rise to its transparency. The center one is composed of numerous and very small single crystals that are all connected; the boundaries between these small crystals scatter a portion of the light reflected from the printed page, which makes this material optically translucent. And finally, the specimen on the right is composed not only of many small, interconnected crystals, but also of a large number of very small pores or void spaces. These pores also effectively scatter the reflected light and render this material opaque.

Thus, the structures of these three specimens are different in terms of crystal boundaries and pores, which affect the optical transmittance properties. Furthermore, each material was produced using a different processing technique. And, of course, if optical transmittance is an important parameter relative to the ultimate in-service application, the performance of each material will be different.

Diamonds are carbon based structures formed naturally under high pressure and temperatures by a geological process. They have excellent physical properties useful for industrial applications and employed for their unparalleled optical properties in the jewelry business.

1.3 Why Study Materials Science and Engineering ?

Why do we want to know to cook the food in our kitchen ? After you finished the delicious cuisine, you can take photos showing in the blog to your friends. Again, the same ideal,  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. If you want to become an excellent chef, you'd better understand Materials Science and Engineering,
not only for the food, but also can brew the beer or whiskey.

1.4 Classification of Materials

Solid materials have been conveniently grouped into three basic classifications: metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are some intermediates. In addition, there are three other groups of important engineering materials—composites, semiconductors, and biomaterials. Composites consist of combinations of two or more different materials, whereas semiconductors are utilized because of their unusual electrical characteristics; biomaterials are implanted into the human body. A brief explanation of the material ypes and representative characteristics is offered next.

Metals

Metallic materials are normally combinations of metallic elements. They have large numbers of nonlocalized electrons; that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. Metals are extremely good conductors of electricity and heat and are not transparent tovisible light; a polished metal surface has a lustrous appearance. Furthermore, metals are quite strong, yet deformable, which accounts for their extensive use in structural applications.

Ceramics

Ceramics are compounds between metallic and nonmetallic elements; they are mos frequently oxides, nitrides, and carbides. The wide range of materials that falls within this classification includes ceramics that are composed of clay minerals, cement, and glass. These materials are typically insulative to the passage of electricity and heat, and are more resistant to high temperatures and harsh environments than metals and polymers. With regard to mechanical behavior, ceramics are hard but very brittle.

Polymers

Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements; furthermore, they have very large molecular structures. These materials typically have low densities and may be extremely flexible.

Composites

A number of composite materials have been engineered that consist of more than one material type. Fiberglass is a familiar example, in which glass fibers are embedded within a polymeric material. A composite is designed to display a combination of the best characteristics of each of the component materials. Fiberglass acquires strength from the glass and flexibility from the polymer. Many of the recent material developments have involved composite materials.

Semiconductors

Semiconductors have electrical properties that are intermediate between the electrical
conductors and insulators. Furthermore, the electrical characteristics of these materials are extremely sensitive to the presence of minute concentrations of impurity atoms, which concentrations may be controlled over very small spatial regions. The semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past two decades.

Biomaterials

Biomaterials are employed in components implanted into the human body for replacement of diseased or damaged body parts. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions). All of the above materials—metals, ceramics, polymers, composites, and semiconductors—may be used as biomaterials.

1.5 Advanced Materials

Materials that are utilized in high-technology (or high-tech) applications are sometimes
termed advanced materials. By high technology we mean a device or product that operates or functions using relatively intricate and sophisticated principles; examples include electronic equipment (VCRs, CD players, etc.), computers, fiberoptic systems, spacecraft, aircraft, and military rocketry. These advanced materials are typically either traditional materials whose properties have been enhanced or newly developed, high-performance materials. Furthermore, they may be of all material types (e.g., metals, ceramics, polymers), and are normally relatively expensive. In subsequent chapters are discussed the properties and applications of a number of advanced materials—for example, materials that are used for lasers, integrated circuits, magnetic information storage, liquid crystal displays (LCDs), fiber optics, and the thermal protection system for the Space Shuttle Orbiter.