The document discusses the history of materials used by human civilization and the development of materials science and engineering. It describes how early civilizations progressed from the Stone Age to the Bronze Age to the Iron Age based on their ability to produce and use increasingly advanced materials. More recently, the development of advanced materials like ceramics, polymers, composites, and semiconductors has driven technological progress. The core components of materials science are described as structure, properties, processing, and performance, and how they interrelate.

1. By Leliso H..
Mettu University
Faculty of Engineering and Technology
Department of Mechanical engineering
Engineering Material

2. 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 and the
historians have identified early periods of civilization
by the name of most significantly used material
(Stone Age, Bronze Age, Iron Age).

3. Contd.
 Stone →Bronze →Iron →Advanced materials
 From the historical point of view, it can be said that
human civilization started with Stone Age where
people used only natural materials, like stone, clay,
skin, and wood for the purposes like to make
weapons, instruments, shelter, etc.
 Thus the sites of deposits for better quality stones
became early colonies of human civilization.

4. Contd.
 However, the increasing need for better quality tools
brought forth exploration that led to Bronze Age.
 The Stone Age ended about 5000 years ago with
introduction of Bronze in the Far East.
 When people found copper and how to make it
harder by alloying, the Bronze Age started about
3000 BC
 Bronze is an alloy (a metal made up of more than
one element), copper + < 25% of tin + other
elements.
 Bronze: can be hammered or cast into a variety of
shapes, can be made harder by alloying, corrode
only slowly after a surface oxide film forms.

5. Contd.
 The Iron Age began about 3000 years ago and
continues today. Use of iron and steel, a stronger
and cheaper material changed drastically daily life of
a common person.
 The use of iron and steel, a stronger material that
gave advantage in wars started at about 1200 BC.
 Iron was abundant and thus availability is not limited
to the affluent.
 This commonness of the material affected every
person in many aspects, gaining the name
democratic material.

6. Contd.
 Age of Advanced materials: throughout the Iron
Age many new types of materials have been
introduced (ceramic, semiconductors, polymers,
composites…).
 This age is marked by many technological
developments towards development materials
resulting in stronger and light materials like
composites, electronic materials like
semiconductors, materials for space voyage like high
temperature ceramics, biomaterials, etc.

7. MATERIALS SCIENCE AND
ENGINEERING
 Sometimes it is useful to subdivide the discipline of
materials science and engineering into materials
science and materials engineering sub disciplines.
 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.
 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.

8. Contd.
 Four Major Components of Material Science and
Engineering:
 Structure of Materials
 Properties of Materials
 Processing of Materials
 Performance of Materials
 “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.”

9. 9
• Subatomic level Electronic structure of
individual atoms that defines interaction among
atoms (interatomic bonding).
• Atomic level Arrangement of atoms in materials
(for the same atoms can have different properties,
e.g. two forms of carbon: graphite and diamond)
• Microscopic structure Arrangement of small
grains of material that can be identified by
microscopy.
• Macroscopic structure
Structural elements that may be viewed with the
naked eye.
Structure
Annealing of a polycrystalline grain structure
2D simulation using Monte Carlo Potts model.
2D simulations involve 40,000 sites and takes a day to run on a fast
workstation, 3D simulations involve 64 million sites, runs on 1000
processors of ASCI-Red.
Monarch butterfly
~ 0.1 m

10. 10
Properties are the way the material responds to the environment and
external forces.
Mechanical properties – response to mechanical forces, strength, etc.
Electrical and magnetic properties - response electrical and magnetic
fields, conductivity, etc.
Thermal properties are related to transmission of heat and heat capacity.
Optical properties include to absorption, transmission and scattering of
light.
Chemical stability in contact with the environment - corrosion
resistance.
Properties

11. Contd.
 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 below.

12. Contd.
We now present an example of these processing-structure-properties-
performance principles with Figure below

13. Contd.
 From the above photograph of three thin disk
specimens of aluminum oxide, which have been
placed over a printed page in order to demonstrate
their differences in light-transmittance characteristics.
 The disk on the left is transparent (that is, virtually all
light that is reflected from the page passes through it),
 whereas the one in the center is translucent
(meaning that some of this reflected light is
transmitted through the disk).
 And, the disk on the right is opaque—i.e., none of
the light passes through it. These differences in
optical properties are a consequence of differences in
structure of these materials, which have resulted from
the way the materials were processed.

14. Contd.
single crystal
polycrystal:
low porosity
polycrystal:
high porosity

15. Contd.
 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.
 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

16. Contd.
 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.

17. Why Study Materials Science and
Engineering?
 Innovation in engineering often means the clever use
of a new material for a specific application. For
example: plastic containers in place of age-old
metallic containers.
 It is well learnt lesion that engineering disasters are
frequently caused by the misuse of materials.
 So it is vital that the professional engineer should
know how to select materials which best fit the
demands of the design - economic and aesthetic
demands, as well as demands of strength and
durability.

18. Contd.
 Beforehand the designer must understand the
properties of materials, and their limitations.
 Thus it is very important that every engineer must
study and understand the concepts of Materials
Science and Engineering.
 This enables the engineer
 • To select a material for a given use based on
considerations of cost and performance.
 • To understand the limits of materials and the
change of their properties with use.
 • To be able to create a new material that will have
some desirable properties.
 • To be able to use the material for different

19. Classification of Engineering
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 the composites, combinations
of two or more of the above three basic material
classes.
 Another classification is advanced materials—those
used in high-technology applications—viz.
semiconductors, biomaterials, smart materials, and

20. Contd.
Metals
 Materials in this group are composed of one or more
metallic elements (such as iron, aluminum, copper,
titanium, gold, and nickel), and often also nonmetallic
elements (for example, carbon, nitrogen, and oxygen) in
relatively small amounts.
 The term metal alloy is used in reference to a metallic
substance that is composed of twoor more elements.
 Atoms in metals and their alloys are arranged in a very
orderly manner and in comparison to the ceramics and
polymers, are relatively dense.
 With regard to mechanical characteristics, these
materials are relatively stiff and strong, yet are ductile
(i.e., capable of large amounts of deformation without
fracture), and are resistant to fracture, which accounts for
their widespread use in structural applications.

21. Contd.
 These materials are characterized by high thermal
and electrical conductivity; strong yet deformable
under applied mechanical loads; opaque to light
(shiny if polished).
 These characteristics are due to valence electrons
that are detached from atoms, and spread in an
electron sea that glues the ions together, i.e. atoms
are bound together by metallic bonds and weaker
van der Waalls forces.
 In addition, some of the metals (viz., Fe, Co, and Ni)
have desirable magnetic properties.

22. Contd.

23. Contd.

24. Contd.

25. Contd.
Ceramics
 Ceramics are compounds between metallic and
nonmetallic elements; they are most frequently oxides,
nitrides, and carbides.
 For example, some of the common ceramic materials
include aluminum oxide (or alumina,Al2O3), silicon
dioxide (or silica,SiO2), silicon carbide (SiC), silicon
nitride (Si3N4), and, in addition, what some refer to as
the traditional ceramics—those composed of clay
minerals (i.e., porcelain), as well as cement, and glass.
 With regard to mechanical behavior, ceramic materials
are relatively stiff and strong—stiffnesses and strengths
are comparable to those of the metals. In addition,
ceramics are typically very hard.
 On the other hand, they are extremely brittle (lack

26. Contd.
 These materials are typically insulative to the passage of
heat and electricity (i.e., have low electrical
conductivities), and are more resistant to high
temperatures and harsh environments than metals and
polymers.
 With regard to optical characteristics, ceramics may be
transparent, translucent, or opaque, and some of the
oxide ceramics (e.g., Fe3O4) exhibit magnetic behavior.

27. Contd.

28. Contd.

29. Contd.

30. Contd.
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 (viz. O, N, and Si).
 Furthermore, they have very large molecular structures,
often chain-like in nature that have a backbone of carbon
atoms.
 Some of the common and familiar polymers are
polyethylene (PE), nylon, poly(vinyl chloride) (PVC),
polycarbonate (PC), polystyrene (PS), and silicone rubber.
 These materials typically have low densities, whereas their
mechanical characteristics are generally dissimilar to the
metallic and ceramic materials—they are not as stiff nor as
strong as these other material types

31. Contd.
 In addition, many of the polymers are extremely
ductile and pliable (i.e., plastic), which means they
are easily formed into complex shapes.
 In general, they are relatively inert chemically and
unreactive in a large number of environments.
 One major drawback to the polymers is their
tendency to soften and/or decompose at modest
temperatures, which, in some instances, limits their
use.
 Furthermore, they have low electrical conductivities
and are nonmagnetic.

32. Contd.

33. Contd.
Composites
 A composite is composed of two (or more) individual
materials, which come from the categories discussed
above—viz., metals, ceramics, and polymers.
 The design goal of a composite is to achieve a
combination of properties that is not displayed by any
single material, and also to incorporate the best
characteristics of each of the component materials.
 A large number of composite types exist that are
represented by different combinations of metals,
ceramics, and polymers.
 Furthermore, some naturally-occurring materials are also
considered to be composites—for example, wood and
bone. However, most of those we consider in our
discussions are synthetic (or man-made) composites.

34. Contd.
 One of the most common and familiar composites is
fiberglass, in which small glass fibers are embedded
within a polymeric material (normally an epoxy or
polyester).
 The glass fibers are relatively strong and stiff (but also
brittle), where as the polymer is ductile (but also weak
and flexible). Thus, the resulting fiberglass is relatively
stiff, strong, (Figures 1.4 and 1.5) flexible, and ductile. In
addition, it has a low density (Figure 1.3).
 Another of these technologically important materials is
the “carbon fiber reinforced polymer” (or “CFRP”)
composite—carbon fibers that are embedded within a
polymer.
 These materials are stiffer and stronger than the glass
fiber-reinforced materials (Figures 1.4 and 1.5), yet they
are more expensive. The CFRP composites are used in
some aircraft and aerospace applications, as well as
high-tech porting equipment (e.g., bicycles, golf clubs,

35. 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
(camcorders, CD/DVD players, etc.), computers, fiber-optic
systems, spacecraft, aircraft, and military rocketry.
 These advanced materials are typically traditional materials
whose properties have been enhanced, and, also newly
developed, high-performance materials.
 Furthermore, they may be of all material types (e.g., metals,
ceramics, polymers), and are normally expensive.
 Advanced materials include semiconductors, biomaterials, and
what we may term “materials of the future” (that is, smart
materials and nano engineered materials).
 The properties and applications of a number of these
advanced materials—for example, materials that are used for
lasers, integrated circuits, magnetic information storage, liquid

36. Contd.
Semiconductors
 Semiconductors have electrical properties that are
intermediate between the electrical conductors (viz.
metals and metal alloys) and insulators (viz.
ceramics and polymers)—Figure 1.7.
 Furthermore, the electrical characteristics of these
materials are extremely sensitive to the presence of
minute concentrations of impurity atoms, for which
the concentrations may be controlled over very small
spatial regions.
 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 three decades.

37. Contd.
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.
 For example, some of the biomaterials that are
utilized in artificial hip replacements

38. Contd.
Advanced Materials
 These are materials used in High-Techdevices those
operate based on relatively intricate and sophisticated
principles (e.g. computers, air/space-crafts, electronic
gadgets, etc.).
 These materials are either traditional materials with
enhanced properties or newly developed materials with
high-performance capabilities.
 Hence these are relatively expensive. Typical
applications: integrated circuits, lasers, LCDs, fiber
optics, thermal protection for space shuttle, etc.
Examples: Metallic foams, inter-metallic compounds,
multi-component alloys, magnetic alloys, special

39. Future Materials
Smart materials
 Group of new and state-of-the-art materials now being
developed, and expected to have significant influence on
present-day technologies, especially in the fields of medicine,
manufacturing and defense. Smart/Intelligent material system
consists some type of sensor (detects an input) and an actuator
(performs responsive and adaptive function).
 Actuators may be called upon to change shape, position, natural
frequency, mechanical characteristics in response to changes in
temperature, electric/magnetic fields, moisture, pH, etc.
 Four types of materials used as actuators: Shape memory
alloys, Piezo-electric ceramics, Magnetostrictive materials,
Electro-/Magneto-rheological fluids.

40. Contd.
Nanoengineered Materials
 With the advent of scanning probe microscopes,
which permit observation of individual atoms and
molecules, it has become possible to manipulate and
move atoms and molecules to form new structures
and, thus, design new materials that are built from
simple atomic-level constituents (i.e., “materials by
design”).
 This ability to carefully arrange atoms provides
opportunities to develop mechanical, electrical,
magnetic, and other properties that are not otherwise
possible.
 The study of the properties of these materials is
termed “nanotechnology”; the “nano” prefix denotes
that the dimensions of these structural entities are on

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