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MAE 301: Engineering

Materials Science

Introduction to Engineering

Materials Science

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2

Introduction Engineering Materials

Science

Course Objective...Introduce fundamental concepts in Materials

ScienceYou will learn about:

material structure how structure dictates properties how processing can change structure

This course will help you to: use materials properly realize new design opportunities

with materials

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3

Introduction to Engineering

Materials Science

Materials drive our society Materials are probably more deeply rooted in our

society than most realize (e.g. electronics,

communication, aerospace/transportation,housing, etc)

The development of many technologies have beenintimately associated with accessibility to newmaterials.

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These materials are used to create everything from those small things we don't

think about, such as dashboard needles and wiring, to the big stuff, such as

the engine block or the transmission gears.

Automobile Industry

Steel (including high-strength steels)

Aluminum

Plastics, rubber

Glass

Copper

Iron

Magnesium Composite materials

Materials Make Technology Possible

Examples:

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Materials Drive our Society

High-strength alloy steels are

used for Submarine hulls

Steel and Aluminum are used in

building Passenger Ships Nickel, Aluminum, Bronze alloys

are used for marine Propellers

High strength steel alloys,

Aluminum, Carbon fiber, and PVC-

related Plastics are used in High

Speed Rail

Transportation by Sea and Rail

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Materials Make Technology Possible

Al-Li alloys are used in jetliner airframes. Theyare superior to aluminum alloys in strength andstiffness, so can be used to save weight. But they

are ~ 3x as expensive.

Commercial Airplanes are mostly built using

Aluminum Alloys.

Newer planes are built with some Composite

Materials.

Jet engines often use Titanium. Some military

aircraft use Titanium for structural and body

pieces.

Special Ceramics are used for the heat shield

of the space shuttle

Aerospace Industry: Aerospace materials must be lightweight and strong.

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Materials in Sports Equipment

Sports equipment uses

almost advanced metal

alloys, ceramics, polymers,

and composites, as athletesand designers leverage

state-of-the-art materials to

maximize human efficiency,

performance, comfort and

safety.

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Prosthetic devices often

need to be lightweight.

They are typically made from

Polymeric materials(polyethylene, polypropylene,

acrylics, and polyurethane ),

Lightweight metals alloys of

titanium and aluminum, and

Composites (such as carbonfiber reinforced composites).

Materials in Biomedical Engineering

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Example Hip Implant

Adapted from Fig. 22.25, Callister 7e.

X-Rays of a normal hip joint (left) and a fractured hip joint (right). The

arrows show the two ends of the fracture line through the femoral neck.

With age or certain illnesses joints deteriorate, particularly joints withlarge loads (such as hip).

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Materials for Hip Implant

Materials Requirements

mechanical strength

(many cycles)

good lubricity

Biocompatibility

lightweight components

Reasonable cost

Adapted from Fig. 22.24, Callister 7e.

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Hip Implant

Adapted from Fig. 22.26, Callister 7e.(a) Schematic diagram and (b) x-ray of an artificial total hip replacement.

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Hip Implant

Key problems to overcome

fixation agent to hold

acetabular cup

cup lubrication material

femoral stem fixing agent

must avoid any debris in cup

FemoralStem

Ball

AcetabularCup and Liner

Adapted from chapter-opening photograph,

Chapter 22, Callister 7e.

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Hip Implant Materials

Femoral Stem: Materials used include:

Stainless steel, 316L (Cold worked)

Titanium-aluminum-vanadium Alloy, Ti-6Al-4V, (HotForged)

Cobalt-chromium-molybdenum Alloy, Co-28Cr-6Mo, (Cast)

Ball Component: Materials used include

high-purity, polycrystalline aluminum oxide orzirconium

oxide. These ceramic materials are harder and more wearresistant than metals, and generate lower frictional stressesat the joint.

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Hip Implant Materials

Acetabular Cup: The inner-cup is often made fromultra-high molecular weight polyethylene, which isvirtually inert in the body and has excellent wearresistance, and a low coefficient of friction with the ballmaterial. The outer cup is fabricated from one of themetal alloys used for the femoral stem.

Fixation Agent: The most common is polymethyl

methacrylate (acrylic) bone cement.

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Hip Implant Example

Hip Implant Example illustrated the need fortailor-made

materials for this human need.

The solution required:

Knowledge of the responses of the various materials (e.g.Ti-6Al-4V, Al2O3, ZrO2, polyethylene, etc.) when exposed to external

stimuli (properties).

Knowledge of the effect of alloying elements and fabrication

processes (casting, forging, cold working,..) on the internal make-

up of the material (material structures).

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Materials Science and Engineering

The ability to fashion materials to fit a wide variety ofneeds is a capability unique to our modern society.

Early Metallurgy

Used metals like Copper, Tin, Silver, Iron Understood that material properties could be altered by alloying

and heat treatment

Modern Materials Science Involves the relationships between the underlying structures ofmaterials and the resultant properties

This knowledge allows materials to be tailor-made for a variety ofneeds.

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Materials Science and Engineering

Materials science

Involves investigating the relationship

between the structures of materials and their

properties

Materials Engineering

Engineering the structures of materials toproduce a predetermined set of properties

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Material Structures

This is the arrangement of the internal components of amaterial:

Subatomic structure: involve the electrons within the individualatoms and interactions with their nuclei

Atomic level Structure: the organization of atoms or moleculeswith respect to one another

Microscopic Structure: large groups of atoms that are

agglomerated together

Macroscopic Structure: Structural elements that can be viewedwith the naked eys

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Sub-Atomic Structure Atomic Structure

Microstructure Macrostructure

Material Structures

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Common Material Properties

Mechanical (deformation resulting from an applied load)

Electrical (e.g. Electrical Conductivity)

Thermal (Thermal conductivity, heat capacity)

Magnetic (Response to a magnetic field)

Optical (Response to an electromagnetic field. e.g.

reflection, transmission, refractive index)

Deteriorative (Corrosion, Response to chemical activity)

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Processing Structure

Properties Performance

Processing, Structure, Properties,

& Performance

Goal: To tailor-make/design materials with precise properties.

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ex: hardness vs structure of steel Propertiesdepend onstructure

Data obtained from Figs. 11.31(a)

and 11.33 with 4 wt% C composition,

and from Fig. 14.8 and associated

discussion, Callister & Rethwisch 3e.

Micrographs adapted from (a) Fig.

11.19; (b) Fig. 10.34;(c) Fig. 11.34;

and (d) Fig. 11.22, Callister & Rethwisch 3e.

ex: structure vs cooling rate of steel Processing can change structure

Structure-Property Relationships

H

ardness(BHN)

Cooling Rate (C/s)

100

2 00

3 00

4 00

5 00

6 00

0.01 0.1 1 10 100 1000

(d)

30mm

(c)

4mm

(b)

30mm

(a)

30mm

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Types of Materials Metals:

Composed of one or more metallic elements Strong, ductile, High thermal & electrical conductivity

Opaque, reflective.

Polymers: Very large molecular structures based on C, H, and nonmetals

Soft, ductile, low strength, low density, translucent or transparent

Thermal & electrical insulators, chemically inert

Ceramics: compounds of metallic & nonmetallic elements (oxides,carbides, nitrides, sulfides).

Stiff and strong (similar to metals). High temperature resistant.

Very hard, extremely brittle, Non-conducting (insulators)

Composites: Composed of two or more individual materials

(metals, ceramics, or polymers), with a combination of properties

not displayed by any single material.

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Metals

Typical Metal Items

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Examples of Ceramics

Silicon nitride (Si3N4) ceramics have goodshock resistance compared to other

ceramics. Si3N4 ball bearings are used in

the main engines of the Space Shuttle.

They areharder than metal

have 80% less friction;

last 3 to 10 times longer;

operate at 80% higher speed;

weigh 60% less;operate with lubrication starvation;

have higher corrosion resistance

higher operation temperature,

compared to metal bearings.

Typical Ceramic Items

Silicon Nitride Items

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Two main types of p olymers arethermosetsandthermoplast ics.

Thermosets are cross-linked polymers that form 3-D networks, hence are strong

and rigid.

Thermoplastics are long-chain polymers that slide easily past one another when

heated, hence, they tend to be easy to form, bend, and break.

Polymers

Typical Polymeric Items

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Materials Selection

Engineers will at one time or another have tomake design decisions involving materials.

Many time a materials problem is one of

selecting the right material for the design from amany alternatives

Rarely does a material possess the idealcombination of properties, and trade-off arenecessary. A material may have the idealcombination of properties but may beexpensiveand compromise is necessary.

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1. Pick Application Determine required Properties

Processing: changes structure and overall shapeex: casting, sintering, vapor deposition, doping

forming, joining, annealing.

Properties: mechanical, electrical, thermal,

magnetic, optical, deteriorative.

Material: structure, composition.2. Properties Identify candidate Material(s)3. Material Identify required Processing

The Materials Selection Process

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ELECTRICAL Electrical Resistivity of Copper:

Adding impurity atoms to Cu increases resistivity. Deforming Cu increases resistivity.

Adapted from Fig. 12.8, Callister &

Rethwisch 3e. (Fig. 12.8 adapted

from: J.O. Linde,Ann Physik5, 219

(1932); and C.A. Wert and R.M.

Thomson, Physics of Solids, 2nd

edition, McGraw-Hill Company, New

York, 1970.)

T(C)-200 -100 0

1

2

3

4

5

6

Resistivity,r

(10-8O

hm-m)

0

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THERMAL Space Shuttle Tiles:

-- Silica fiber insulation

offers low heat conduction.

Thermal Conductivity

of Copper:

-- It decreases whenyou add zinc!

Adapted from

Fig. 19.4W, Callister

6e. (Courtesy of

Lockheed Aerospace

Ceramics Systems,

Sunnyvale, CA)

(Note: "W" denotes fig.

is on CD-ROM.)

Adapted from Fig. 17.4, Callister & Rethwisch

3e. (Fig. 17.4 is adapted from Metals Handbook:

Properties and Selection: Nonferrous alloys and

Pure Metals, Vol. 2, 9th ed., H. Baker,

(Managing Editor), American Society for Metals,

1979, p. 315.)

Composition (wt% Zinc)

ThermalCond

uctivity

(W/m-K

)

400

300200

100

00 10 20 30 40

100mm

Adapted from chapter-

opening photograph,

Chapter 17, Callister &

Rethwisch 3e. (Courtesy

of Lockheed

Missiles and Space

Company, Inc.)

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MAGNETIC

Magnetic Permeabilityvs. Composition:-- Adding 3 atomic % Si

makes Fe a better

recording medium!

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.

Fig. 18.23, Callister & Rethwisch 3e.

(Fig. 18.23 is from J.U. Lemke, MRS Bulletin,

Vol. XV, No. 3, p. 31, 1990.)

Magnetic Storage:-- Recording medium

is magnetized by

recording head.

Magnetic FieldM

agnetization Fe+3%Si

Fe

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Transmittance:-- Aluminum oxide may be transparent, translucent, oropaque depending on the material structure.

Adapted from Fig. 1.2,

Callister & Rethwisch 3e.

(Specimen preparation,

P.A. Lessing; photo by S.

Tanner.)

single crystal

polycrystal:

low porosity

polycrystal:

high porosity

Example: Optical Properties of

Aluminum Oxide

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DETERIORATIVE Stress & Saltwater...

-- causes cracks!

Adapted from chapter-opening photograph,

Chapter 16, Callister & Rethwisch 3e.

(from Marine Corrosion, Causes, and

Prevention, John Wiley and Sons, Inc., 1975.)

4mm-- material:7150-T651 Al "alloy"

(Zn,Cu,Mg,Zr)

Adapted from chapter-opening

photograph, Chapter 11, Callister & Rethwisch 3e.(Provided courtesy of G.H. Narayanan and A.G. Miller,

Boeing Commercial Airplane Company.)

Heat treatment: slowscrack speed in salt water!

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.)

held at160C for 1 hrbefore testing

increasing loadcracks

peed(m/s)

as-is

10-10

10-8

Alloy 7178 tested insaturated aqueous NaClsolution at 23C

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Use the right material for the job.

Understand the relation between properties,structure, and processing.

Recognize new design opportunities offered

by materials selection.

Course Goals:

SUMMARY

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Review Assignment

Chapter 1

Question 1.1

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Reading Assignment

Chapter 2.1 2.8

Atomic Structures

Interatomic Bonding Forces and Energies Primary and Secondary Bonds