Chapter 1: Introduction to Materials Science & Engineering
Chapter 1: Introduction to
Materials Science & Engineering
ISSUES TO ADDRESS...
• What is materials science and engineering?
• Why are materials important?
• Why is it important for engineers to understand
materials ?
Chapter 1 - 1
What is Materials Science & Engineering?
• Materials science
– Investigate relationships between structures and
properties of materials
– Design/develop new materials
• Materials engineering
– Create products from existing materials
– Develop materials processing techniques
Chapter 1 - 2
Why Are Materials Important?
• Materials drive advancements in our society
– Stone Age
– Bronze Age
– Iron Age
• What is today’s material age?
– Silicon (Electronic Materials) Age?
– Nanomaterials Age?
– Polymer Age?
Chapter 1 - 3
1
Chapter 1: Introduction to Materials Science & Engineering
Why is it Important for Engineers to
Understand Materials?
• Products/devices/components that engineers
design are all made of materials
• To select appropriate materials and
processing techniques for specific
applications engineers must
– have knowledge of material properties and
– understand the structure-property relationships
Chapter 1 - 4
Relationships Among Processing,
Structure, & Properties
• Processing (e.g., cooling rate of steel from high
temperature) affects structure (microstructure)
• Structure in turn effects hardness
(d)
Structure
Hardness (BHN)
Property
6 00
5 00
4 00
(a)
4 µm
3 00
2 00
30 µm
(c)
(b)
30 µm
30 µm
Data obtained from Figs. 10.32(a) and
10.33 with 4 wt% C composition, and from
Fig. 11.18, Callister & Rethwisch 10e.
Micrographs adapted from (a) Fig. 10.19;
(b) Fig. 9.30; (c) Fig. 10.34; and (d) Fig.
10.22, Callister & Rethwisch 10e. (Figures
10.19, 10.22, & 10.34 copyright 1971 by United
States Steel Corporation. Figure 9.30 courtesy
of Republic Steel Corporation.)
100
0.01 0.1
1
10 100 1000
Cooling Rate (ºC/s)
Processing
Chapter 1 - 5
Types of Materials
• Metals:
– Strong, ductile
– High thermal & electrical conductivities
– Opaque, reflective
• Polymers/plastics: compounds of non-metallic elements
– Soft, ductile, low strengths, low densities
– Low thermal & electrical conductivities
– Opaque, translucent or transparent
• Ceramics: compounds of metallic & non-metallic elements
(oxides, carbides, nitrides, sulfides)
– Hard, Brittle
– Low thermal & electrical conductivities
– Opaque, translucent, or transparent
Chapter 1 - 6
2
Chapter 1: Introduction to Materials Science & Engineering
Materials Selection
Engineers often solve materials selection problems.
Procedure:
1.
For a Specific Application
Determine Required Properties
• Properties: mechanical, electrical, thermal,
magnetic, optical, deteriorative.
2.
From List of Properties
Identify Candidate Material(s)
3.
Best Candidate Material
Specify Processing technique(s)
• To provide required set of properties
• To produce component having desired shape and size
• Example techniques: casting, mechanical forming, welding,
heat treating
Chapter 1 - 7
Material Property Types
Properties of materials fall into six categories as
follows:
• Mechanical
• Electrical
• Thermal
• Magnetic
• Optical
• Deteriorative
Chapter 1 - 8
Mechanical Properties
Affect of carbon content on the hardness of a
common steel:
Fig. 10.31, Callister & Rethwisch 10e.
[Data taken from Metals Handbook: Heat
Treating, Vol. 4, 9th edition, V. Masseria
(Managing Editor), 1981. Reproduced by
permission of ASM International, Materials Park,
OH.]
Brinell hardness
320
240
160
80
0
0.5
1 wt%C
• Increasing carbon content increases hardness of steel.
Chapter 1 - 9
3
Chapter 1: Introduction to Materials Science & Engineering
Electrical Properties
Factors that affect electrical resistivity – for copper:
6
Resistivity, ρ
(10-8 Ohm-m)
5
3
u+
a
.32
t%N
Fig. 18.8, Callister & Rethwisch 9e.
i
i
t%N
i
16 a
t%N
+ 2.
12 a
.
Cu
1
+
u
dC
i
rme
t%N
defo
12 a
+ 1.
Cu
Cu
re”
“Pu
C
4
3
2
1
[Adapted from: J.O. Linde, Ann Physik 5, 219
(1932); and C.A. Wert and R.M. Thomson,
Physics of Solids, 2nd edition, McGraw-Hill
Company, New York, 1970.]
0
-200
-100
0
T (°C)
• Increasing temperature increases resistivity.
• Increasing impurity content (e.g., Ni) increases resistivity.
• Deformation increases resistivity.
Chapter 1 - 10
Thermal Properties
Thermal Conductivity
(W/m-K)
Thermal Conductivity – measure of a material’s ability to
conduct heat
400
300
Fig. 19.4, Callister & Rethwisch 10e.
[Adapted from Metals Handbook: Properties
and Selection: Nonferrous alloys and Pure
Metals, Vol. 2, 9th ed., H. Baker, (Managing
Editor), ASM International, 1979, p. 315.]
200
100
0
0
10
20
30
40
Composition (wt% Zinc)
• Increasing impurity content (e.g., Zn in Cu) decreases
thermal conductivity.
Chapter 1 - 11
Thermal Properties (continued)
Material used for space
shuttle
Courtesy of Lockheed Missiles and Space
Company, Inc.
Courtesy of Lockheed Aerospace Ceramics
Systems, Sunnyvale, CA
Highly porous materials are
poor conductors of heat
100 µm
• Ceramic Fibers:
– significant void space
– low thermal conductivity
• Demonstration:
– low thermal conductivity
of this material
Chapter 1 - 12
4
Chapter 1: Introduction to Materials Science & Engineering
Magnetic Properties
• Magnetic Storage:
• Magnetic Permeability
vs. Composition:
-- Adding 3 atomic % Si makes
Fe a better recording medium!
Fe+3%Si
Magnetization
-- Recording medium is
magnetized by recording
write head.
Fe
Magnetic Field
Fig. 20.23, Callister & Rethwisch 10e.
(Courtesy of HGST, a Western Digital Company.)
Adapted from C.R. Barrett, W.D. Nix, and
A.S. Tetelman, The Principles of Engineering
Materials, Fig. 1-7(a), p. 9, 1973.
(Electronically reproduced by permission of Pearson
Education, Inc., Upper Saddle River, New Jersey.)
Chapter 1 - 13
Optical Properties
• The light transmittance of some materials depend on their
structural characteristics:
Aluminum oxide
polycrystalline material
(having many small
grains)—is optically
translucent
Aluminum oxide
polycrystalline
material having some
porosity—is optically
opaque
(Specimen preparation, P.A. Lessing)
Aluminum oxide single
crystal (high degree of
perfection)—is optically
transparent
Chapter 1 - 14
Deteriorative Properties
• Small cracks formed in steel bar that was simultaneously
stressed and immersed in sea water
- Form of stress-corrosion cracking
Cracks
Fig. 17.21, Callister & Rethwisch 10e.
(from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.)
Chapter 1 - 15
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Chapter 1: Introduction to Materials Science & Engineering
Deteriorative Properties (cont.)
Crack Growth Rate (m/s)
• For stress-corrosion cracking, rate of crack growth is
diminished by heat treating
“as-received”
10-8
“heat treated”
Adapted from Fig. 11.20(b), R.W.
Hertzberg, "Deformation and
Fracture Mechanics of Engineering
Materials" (4th ed.), p. 505, John
Wiley and Sons, 1996. (Original
source: Markus O. Speidel, Brown
Boveri Co.)
10-10
load
For Aluminum alloy 7178 that is stressed while immersed in a
saturated aqueous NaCl solution, crack growth rate is reduced by
heat treating (160°C for 1 h prior to testing).
Chapter 1 - 16
Example of Materials Selection:
Artificial Hip Replacement
• Anatomy of a
human hip joint and
adjacent skeletal
features
Chapter 1 - 17
Materials: Artificial Hip Replacement
(cont.)
Hip joint problems can be painful and disabling
• Joint deterioration (loss of cartilage) as one ages
• Joint fracture
arrows point to
ends of fracture line
X-ray of normal hip joint
X-ray of fractured hip joint
Chapter 1 - 18
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Chapter 1: Introduction to Materials Science & Engineering
Materials: Artificial Hip Replacement
(cont.)
• Damaged and diseased hip joints can be
replaced with artificial ones
• Materials requirements for artificial joints
– Biocompatible – minimum rejection by surrounding
body tissues
– Chemically inert to body fluids
– Mechanical strength to support forces generated
– Good lubricity and high wear resistance between
articulating surfaces
Chapter 1 - 19
Materials: Artificial Hip Replacement
(cont.)
• Femoral stem — inserted
into top of hip bone (femur)
Head
(Ball)
• Head (Ball) — affixed to
femoral stem
• Shell — attached to pelvis
• Liner — into which head fits
Liner & Shell
(Acetabular)
Femoral
Stem
Photograph courtesy of
Zimmer, Inc., Warsaw, IN,
USA.
Chapter 1 - 20
Materials: Artificial Hip Replacement
(cont.)
• Materials used
- Femoral stem — titanium or CoCrMo alloy
- Head (Ball) — CoCrMo alloy or Al2O3 (ceramic)
- Shell — titanium alloy
- Liner — polyethylene (polymer) or Al2O3 (ceramic)
Chapter 1 - 21
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Chapter 1: Introduction to Materials Science & Engineering
Materials: Artificial Hip
Replacement (continued)
Head
(Ball)
Acetabular
shell and liner
Schematic diagram of an
artificial hip
X-ray of an implanted
artificial hip
Chapter 1 - 22
SUMMARY
• Appropriate materials and processing decisions
require engineers to understand materials and their
properties.
• Materials' properties depend on their structures;
structures are determined by how materials are
processed
• In terms of chemistry the three classifications of
materials are metals, ceramics, and polymers
• Most properties of materials fall into the following six
categories: mechanical, electrical, thermal, magnetic,
optical, and deteriorative.
• An important role of engineers is that of materials
selection.
Chapter 1 - 23
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