Chapter [1] Introduction to MSE

LECTURE 1

IN MSE 300

Introduction to Materials

Science and Engineering

MATERIALS ARE …

Engineered structures

Substances whose properties make them

useful in structures, machine, devices or

others products

Usually in the form of solids

Technology: development and transfer of knowledge and

techniques to provide society with its needs

and comforts.• To continue to offer what consumers expect and

need, designers must keep abreast with NEW

MATERIALS DEVELOPMENT

Materials Science: a discipline involving investigation of

relationships that exist between the

structure and properties of materials.

Engineering materials: materials whose structures are

designed to develop specific

properties for a given application.

Materials

Science and

Engineering

Materials

Science BASIC KNOWLEDGE

internal structure

properties

Materials

Engineering

APPLIED KNOWLEDGE

processing

performance

“The engineer’s expertise lies in adapting materials and energy to

society’s needs/demands.”

DENSITY OF WATER

Liquid Solid

1.00 g/mL 0.92 g/mL

Materials Science and Engineering:

- A major field of study involving generation and

application of knowledge relating the composition,

structure, and processing of materials to their

properties and uses.

Materials Engineering: deals with synthesis and use

of knowledge (structure,

properties, processing and

behavior) to develop,

prepare, modify and apply

materials to specific needs.


- A major field of study involving generation and application of knowledge relating

the composition, structure, and processing of materials to their properties and uses.

Materials Engineering: deals with synthesis and use of knowledge (structure, properties,

processing and behavior) to develop, prepare, modify

and apply materials to specific needs.

http://www.flickr.com/photos/brampitoyo/3636925679/


- A major field of study involving generation and application of knowledge relating

the composition, structure, and processing of materials to their properties and uses.

Materials Engineering: deals with synthesis and use of knowledge (structure, properties,

processing and behavior) to develop, prepare, modify

and apply materials to specific needs.

Components of Materials Science and Engineering

1. Processing – method by which a material is

manufactured

2. Structure – the arrangement of the internal

components of materials (subatomic, atomic,microscopic,

macroscopic)

3. Properties – materials response (type and magnitude)

to a specific stimulus

4. Performance – ability to conform to its intended use


The interrelationship is LINEAR (Callister, 2003)

Processing Structure Properties Performance


- an interactive information-transfer network, linking the

interrelationships among components, highlighting the

counter-current flows of scientific and empirical

knowledge (Van Vlack, 1989)

• Processing can change

structure.

– Ex. Structure vs. cooling rate

of steel.

100

200

300

400

500

600

700

800

0.01 0.1 1 10 100 1000

Cooling Rate [ C/s ]

Har

d n

ess

[ B

HN

]

cementitepearlite

Tempered

martensite

martensite

Structure, Processing and Properties

• Properties depend on structure.

– Ex. Hardness vs. structure of steel.

0 3 6

1.0

Composition [ wt% C ]

Bri

nel

l H

ard

nes

s

80

120

160

200

240

280

0.2 0.4 0.6 0.8

Spheroidite

Coarse

pearliteFine

pearlite

0

9 12 15

%Fe3C

Structure, Processing and Properties

STRUCTURE

Structural Feature Dimension [m]

Atomic Bonding < 1010

Missing 1 extra atom 1010

Crystals (ordered atoms) 108 101

Second phase particles 108 104

Crystal texturing > 106

STRUCTURE

Sub atomic

Atomic

Microstructure

Macrostructure

STRUCTURE

Sub atomic

STRUCTURE

Atomic

STRUCTURE

Microstructure

STRUCTURE

Macrostructure

Manganese nodules from the ocean floor (Whitten, 2007)

PROPERTIES

materials response (type and magnitude) to a

specific stimulus

Stimulus: Property:

Force Mechanical

Electric field Electrical

Heat Energy Thermal

Magnetic Field Magnetic

Light Optical

Chemical Deteriorative

ELECTRICAL

-250

0-400

Temperature [ C ]

0

1

-300 -200 -100 +100

-50-200 -150 -100 +500

Temperature [ F ]

Ele

ctri

cal re

sist

ivit

y [

10

8

-m]

2

3

4

5

6

• Electrical resistivity of copper

• Adding impurity atoms to Cu increases resistivity .

• Deforming Cu increases resistivity.

THERMAL

• Space Shuttle Tiles

– Silica fiber insulation offers low heat conduction

• Thermal conductivity of copper.

– It decreases when Zn is added.

Composition [ wt%Zn ]2010

Th

erm

al c

on

duct

ivit

y

[ W

/m

-K]

100

200

300

400

100

150

200

250

50

030 400

Th

erm

al c

on

duct

ivit

y

[ B

TU

/ft

-F]

Cu-Zn alloy

OPTICAL

• Transmittance:

– Aluminum oxide may be transparent, translucent, or opaque depending on material structure.

Single crystal

Polycrystal

Low porosity

Polycrystal

High porosity

MAGNETIC

• Magnetic storage:

– Recording medium is

magnetized by recording

head.

gapwidth

Recording

head

Signal

in

Signal

outreadwrite

Recording medium

• Magnetic permeability vs. composition

Magnetic Field

Mag

net

izat

on

Fe

– Adding 3 atomic % Si makes better Fe a better recording medium!

Fe+3%Si

DETERIORATIVE

• Stress and saltwater …. - causes cracks!

• Heat treatment: slows crack speed in saltwater

Increasing load

Cra

ck s

pee

d [

m/

s]

1010

108

Material: 7150 – T651 Al “alloy”

(Zn, Cu, Mg, Zr)

as is

held at 100C for 1 hr

before testing

MECHANICAL PROPERTIES

Stress (s or σ)

– a measure of force per unit area, F/A.

– commonly used units : N/m2, Pa, psi

Strength – critical stress to initiate failure.


Strain (e or δ)

– dimensional response to stress, expressed as a fraction or percent, and is therefore dimensionless, ΔL/L0.

positive (+) under tensile stress

negative (-) under compressive stress

elastic if reversible

plastic if permanent

STRESS-STRAIN DIAGRAM

Elastic limit

Slope = Young’s modulus

or modulus of elasticity

(measure of stiffness)

en

gin

eeri

ng

st

ress

engineering strain

Elastic limit – uppermost stress wherein the material will

return to its original length when the load is removed.

ELASTIC LIMIT

Proportional limit

Slope = Young’s modulusen

gin

eeri

ng

st

ress

engineering strain

Proportional limit - the limit of the proportional range of

the stress-strain curve

PROPORTIONAL LIMIT

A

B

C

YOUNG’S MODULUS

Young’s modulus or modulus of elasticity

– is the measure of stiffness of a material.

– ratio of stress to elastic strain

)/(

)/(

0LL

AF

e

sE

el

Young’s modulus

Slope = Young’s modulus

en

gin

eeri

ng

st

ress

engineering strain

Young’s modulus or modulus of elasticity is the measure of

stiffness of a material.

YOUNG’S MODULUS

A

B

C


Hardness – resistance of a material to penetration

Ductility – plastic strain that accompanies fracture

Toughness

– measure of the energy absorbed prior to fracture.

– proportional to the area under the stress-strain diagram.

Types of fracture in tension

(a) brittle fracture in polycrystalline metals; (b) shear fracture in ductile single crystals; (c) ductile cup-and-cone fracture in polycrystalline

metals; (d) complete ductile fracture in polycrystalline metals,

with 100% reduction of area.

Mechanical Properties

Sample problem

Which part has the greater stress:

(a) rectangular aluminum bar of 24.6 mm x 30.7 mm cross section, under a load of 7640 kg, or

(b) a round steel bar whose cross sectional diameter is 12.8 mm, under a 5000-kg load?


Sample problem

When the stress on the wire 1 mm in diameter is 37 Mpa, the elastic strain is 0.054%. What is the elastic modulus?

)/(

)/(

0LL

AF

e

sE

el


Sample problem

If the average modulus of elasticity of the steel used is 205,000 MPa, by how much will a wire 2.5 mm in diameter and 3 m long be extended when it supports a load of 500 kg?

)/(

)/(

0LL

AF

e

sE

el


Sample problem

An iron 0.50 inch in diameter supports a load elastically of 1540 lbm.

(a) What is the stress placed on the rod in MPa?

(b) How much will the rod be strained by that load?

Electrical Properties

The resistance of a wire in a circuit is a function of the size of the wire as well as the material.

R = electrical resistance, ohm

ρ = resistivity, ohm-m

L = length, m

A = cross sectional area, m2

σ = electrical conductivity, 1/ρ, ohm-1-m-1

A

LR


Sample problem

A copper (ρ = 17 ohm-nm) wire has a diameter of 0.9 mm

(a) What is the resistance of a 30-cm wire?

(b) What must be the length of the wire describe above to have an end-to-end resistance of 0.015 ohm?


Sample problem

What is the difference in the end-to-end resistance of a 2-mm in diameter aluminum (ρ = 29 ohm-nm) wire that is 30.5 m in length and a copper (ρ = 17 ohm-nm) wire with the same dimensions?

Thermal Properties

Thermal Conductivity is expressed as power per unit area along a temperature gradient (W/m-K).

Thot Tcold

Thermal Conductivity (k) varies with temperature.

X

q

dx

dTk

A

q

Thermal Properties

Heat Capacity – quantity of heat required to change the temperature of a SYSTEM by one degree.

If the system is one mole of a substance, therefore it is

termed as molar heat capacity.

Specific heat capacity or specific heat…If the system is one gram of a substance

Thermal Properties

Sample problem

Determine the thermal conductivity of the following engineering materials. (Use Appendix B of Callister)

(a) steel alloy A36

(b) Gold (pure)

(c) Tungsten (pure)

(d) Aluminum oxide

(e) Borosilicate glass

(f) Nylon 6,6

(g) Red oak (12% moisture)

Thermal Properties

Sample problem

Using the data below, estimate the thermal conductivity of Copper at 350K, 745K,and 868K.

Thermal conductivity of Copper at different temperatures

T, K 300 400 600 800 1000 1200

k, W/mK 398 392 383 371 357 342

Thermal Properties

Sample problem

A cylindrical iron sample (height to diameter ratio is 2:1)is heated to 97.5°C, then immersed in 247 mL of wateroriginally at 20.7°C. When thermal equilibrium has beenreached, the water and iron are both at 36.2°C. Calculatethe dimensions (diameter and height) of the iron sample.

Properties of Iron:

Specific heat = 0.45 J/g°C

Density = 7.87 g/cm3

Properties of Water


Density = 1.0 g/cm3

Thermal Properties

Sample problem

A spherical iron sample is heated to 97.5°C, thenimmersed in 247 mL of water originally at 20.7°C. Whenthermal equilibrium has been reached, the water and ironare both at 36.2°C. Calculate the radius (in inches) of theiron sample.

Properties of Iron:


Density = 7.87 g/cm3

Properties of Water


Density = 1.0 g/cm3

Extracting

raw materials

Creating bulk materials,

components and devices

Manufacturing

engineered materials

Fabricating products

and systems

Services of products

and systems

Recycling/disposing of

used products and systems

MATERIALS CYCLE

Creating bulk materials,

components and devices

Manufacturing

engineered materials

Fabricating products

and systems

Recycling/disposing of

used products and systems

Material

Science

Engineering

Mechanics DurabilityEngineering

Design

Life-cycle concerns

Fundamental laws

Interactions between material

components

Quality

Reliability

Cost

MANUFACTURING

ROLES OF ENGINEERS IN

MANUFACTURING

Manufacturing Engineers – select and coordinate specific processes and equipment to be used.

Design Engineers – design the machines and equipment used in manufacturing, select and specify the materials to be used in order to meet the requirements.

Materials Engineers – devote their major efforts toward developing new and better materials for use in commercial products.

Materials Scientists – study how the structure of materials

relates to their properties

Materials Selection

• What selection criteria are important to suit the requirements of products needed.

• How do designers select to arrive at the best material?

• What is an ideal material?

In materials selection,

COMPROMISE is the rule not

the exception.

The Materials Selection Process

1. Pick Application Determine required properties

Properties : Mechanical, electrical, thermal, magnetic, optical, deteriorative.

2. Properties Identify candidate material/s

Material: structure, composition

3. Materials Identify required processing

Processing: changes structure and overall shape.

Ex. Castings, sintering, vapor deposition, doping, forming, joining, annealing

4. Additional selection criteria

CHARACTERISTICS OF AN IDEAL

MATERIAL

endless and readily available source of supply

cheap to refine and produce

energy efficient

strong, stiff, and dimensionally stable at all temperatures

lightweight

corrosion resistant

no harmful effects on the environment or people

biodegradable

numerous secondary uses

SELECTION TOOLS AND FACTORS

Availability – material must be

available at a reasonable cost and in the

desired form (if not available in the

desired state, the material should be

convertible to the desired form).

Economics – cost of materials and

processing must be considered.

Properties – materials performance

characteristics

ALGORITHMS OR STEPS:

Selection Tools

Properties of materials

Materials systems

Additional Selection Criteria

existing specifications

availability

Processibility

Near-net-shape production

Quality and performance

Consumer acceptance

Design for assembly

BASIC APPROACHES TO

FINAL MATERIALS SELECTION

minimum investment and high maintenance

high investment and low maintenance

optimum investment and maintenance

REASONS WHY MATERIAL SELECTION DECISIONS

ARE AMONG THE MOST IMPORTANT THE DESIGN

ENGINEER MUST MAKE:

The number of materials available is large and constantly increasing.

Domestic and foreign competitions increasingly require product reevaluation.

Service requirements and consumer demands for reliability as well as function have become more severe.

In many cases, the material has a direct relationship to the appearance of the product and its sales appeal.

In many cases, the material dictates what processing must be used in order to manufacture the product.

Because of strict and comprehensive product-liability laws, failure of products can result in very costly litigation and damages.

AIDS TOMATERIALS

SELECTION

A broad basic understanding of the nature, properties and processing of materials.

Tables of properties of engineering materials. Data must be computerized to allow easier access)

Magazines, periodicals, books, journals, compilation of current lists or charts of cost indices and quotations.

Rating charts.

Three materials X, Y, and Z are available for a certain

usage. Any material selected must have a good weldability. Tensile

strength, stiffness, stability and fatigue strength are required with

fatigue strength considered being the most important and stiffness

the least important of these factors. The three materials are rated as

follows in these factors.

Properties X Y Z

Weldability E P G

Tensile strength G E Fair

Stiffness VG G G

Stability G E G

Fatigue strength Fair G E

Which material should be selected?

Classification of Materials

1. Metals

2. Ceramics

3. Polymers

4. Composites

5. Electronic-related materials

6. Biomaterials

Summary

Course Goals

• Use the right material for the job.

• Understand the relation between

properties, structure and processing.

• Recognize new design opportunities

offered by materials selection.

References:

[1] de Garmo, Paul E., Temple J. Black, and Ronald A.

Kohser, Engineering Materials and Processes 8th ed., John Wiley and

Sons, Inc., New York (1999).

[2] Callister, William D. Jr., Materials Science and

Engineering, 6th ed., John Wiley and Sons, Inc.,Singapore

(2009).

[3] Shackelford, James F., Introduction to Materials Science for

Engineers, Pearson Education Inc., Upper Saddle River, NJ

(2004).

[4] Van Vlack, Lawrence H., Materials Science for Engineers, 4th

ed., Addison-wesley Publishing Co., Inc., Philippines (1980).

Chapter [1] Introduction to MSE

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