What is Materials Science/Engineering?

Processing

Structure PropertiesMaterials

CeramicsMetalsPolymersSemiconductorsComposites

BondingOrder/disorderAtomic arrangementsDefects

MechanicalElectricalMagneticEnvironmentalOpticalThermal…Length scales: atom (Å) -> ~ mm

What is Materials Science?

Materials Structure

m10-18 10-14 10-10 10-6 10-2 102 104

1 m

PhilosophyNuclear�Physics

Materials�Science

Structural�Engineering

Solid State Physics

1 �

Turbine bladeCrystallites “grains”

Atom arrangements in a crystal nm - mm m

Å - nm

CHAPTER 1: MATERIALS SCIENCE & ENGINEERING

Materials are... engineered structures...not blackboxes!

Structure...has many dimensions...

Structural feature Dimension (m)

atomic bonding

missing/extra atoms

crystals (ordered atoms)

second phase particles

crystal texturing

< 10 -10

10-10

10-8-10-1

10-8-10-4

> 10-6

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Materials Structure - Course Outline

1. Bonding

2. The science of describing crystalline materials: Crystallography

3. Defects in materials

Aluminum - metallic Sodium chloride (salt) -ionic

1 nm

“seeing atom arrangements in crystals”: transmission electron

microscopy of thin Sc2O3 foil

Structure, Processing, & Properties

ex: hardness vs structure of steel• Properties depend on structure

Data obtained from Figs. 10.21(a)and 10.23 with 4wt%C composition,and from Fig. 11.13 and associateddiscussion, Callister 6e.Micrographs adapted from (a) Fig.10.10; (b) Fig. 9.27;(c) Fig. 10.24;and (d) Fig. 10.12, Callister 6e.

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

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Cooling Rate (C/s)

100

200

300

400

500

600

0.01 0.1 1 10 100 1000

(a)

30µm

(b)

30µm

(d)

30µm(c)

4µm

Ha

rdn

ess

(B

HN

)

The Materials Selection Process

Pick Application Determine required Properties1.Properties: mechanical, electrical, thermal,magnetic, optical, deteriorative.

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

Material Identify required Processing3.Processing: changes structure and overall shapeex: casting, sintering, vapor deposition, doping

forming, joining, annealing.

3

ELECTRICAL

T (°C)-200 -100 0

Cu + 3.32 at%Ni

Cu + 2.16 at%Ni

deformed Cu + 1.12 at%Ni

1

2

3

4

5

6

Re

sist

ivit

y, ρ

(1

0-8

Oh

m-m

)

0

Cu + 1.12 at%Ni

“Pure” Cu

• Electrical Resistivity of Copper:

Adapted from Fig. 18.8, Callister 6e.(Fig. 18.8 adapted from: J.O. Linde,Ann Physik 5, 219 (1932); andC.A. Wert and R.M. Thomson,Physics of Solids, 2nd edition,McGraw-Hill Company, New York,1970.)

• Adding “impurity” atoms to Cu increases resistivity.• Deforming Cu increases resistivity.

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THERMAL

• Space Shuttle Tiles:--Silica fiber insulation

offers low heat conduction.

• Thermal Conductivityof Copper:--It decreases when

you add zinc!

Composition (wt%Zinc)Th

erm

al C

on

du

cti

vity

(W

/m-K

)

400

300

200

100

00 10 20 30 40

5

Fig. 19.0, Callister 6e.(Courtesy of LockheedMissiles and SpaceCompany, Inc.)

100µm

Adapted fromFig. 19.4W, Callister 6e. (Courtesy of Lockheed Aerospace Ceramics Systems, Sunnyvale, CA)(Note: "W" denotes fig. is on CD-ROM.)

Adapted from Fig. 19.4, Callister 6e.(Fig. 19.4 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.)

MAGNETIC

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

makes Fe a betterrecording medium!

Fig. 20.18, Callister 6e.(Fig. 20.18 is from J.U. Lemke, MRS Bulletin,Vol. XV, No. 3, p. 31, 1990.)

• Magnetic Storage:--Recording medium

is magnetized byrecording head.

Magnetic FieldMa

gn

eti

zati

on

Fe+3%Si

Fe

Adapted from C.R. Barrett, W.D. Nix, andA.S. Tetelman, The Principles ofEngineering Materials, Fig. 1-7(a), p. 9,1973. Electronically reproducedby permission of Pearson Education, Inc.,Upper Saddle River, New Jersey.

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OPTICAL

• Transmittance:--Aluminum oxide may be transparent, translucent, or

opaque depending on the material structure.

Adapted from Fig. 1.2,Callister 6e.(Specimen preparation,P.A. Lessing; photo by J. Telford.)

single crystalpolycrystal:low porosity

polycrystal:high porosity

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DETERIORATIVE

• Stress & Saltwater...--causes cracks!

• Heat treatment: slowscrack speed in salt water!

“held at 160C for 1hr before testing”

increasing loadcra

ck

spe

ed

(m

/s)

“as-is”

10-10

10-8

Alloy 7178 tested in saturated aqueous NaCl solution at 23C

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.)

Adapted from Fig. 17.0, Callister 6e.(Fig. 17.0 is from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.) 4µm--material:

7150-T651 Al "alloy"(Zn,Cu,Mg,Zr)

8

Adapted from Fig. 11.24,Callister 6e. (Fig. 11.24 provided courtesy of G.H.Narayanan and A.G. Miller, Boeing CommercialAirplane Company.)

SUMMARY

Course Goals:

• Use the right material for the job.

• Understand the relation between properties,structure, and processing.

• Recognize new design opportunities offeredby materials selection.

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