Materials Science Engineering

The Science and Engineering of Materials, 5th ed Donald R. Askeland – Pradeep P. Phulé

Chapter 1 – Introduction to Materials Science and Engineering

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Objectives of Chapter 1 † Introduce the field of materials science and engineering (MSE) † Provide introduction to the classification of materials

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Outline † 1.1 What is Materials Science and Engineering? † 1.2 Classification of Materials † 1.3 Functional Classification of Materials † 1.4 Classification of Materials Based on Structure † 1.5 Environmental and Other Effects † 1.6 Materials Design and Selection

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What is Materials Science and Engineering? † Materials Science and Engineering Materials Science – emphasis on relationships between synthesis and processing, structure and properties

† † † †

Materials Engineering – emphasis on transforming materials into useful devices or structures Composition means the chemical make-up of a material. Structure means a description of the arrangements of atoms or ions in a material. Synthesis is the process by which materials are made from naturally occurring or other chemicals. Processing means different ways for shaping materials into useful components or changing their properties. 3

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Classification of Materials

‰ Metals and Alloys

‰ ‰ ‰ ‰

Ceramics, Glasses,and Glass-ceramics Polymers (plastics), Thermoplastics and Thermosets Semiconductors Composite Materials

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Functional Classification of Materials ‰ ‰ ‰ ‰ ‰ ‰ ‰ ‰

Aerospace Biomedical Electronic Materials Energy Technology and Environmental Technology Magnetic Materials Photonic or Optical Materials Smart Materials Structural Materials

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Section 1.4 Classification of Materials-Based on Structure ‰ Crystalline material is a material comprised of one or many crystals. In each crystal, atoms or ions show a long-range periodic arrangement. ‰ Single crystal is a crystalline material that is made of only one crystal (there are no grain boundaries). ‰ Grains are the crystals in a polycrystalline material. ‰ Polycrystalline material is a material comprised of many crystals (as opposed to a single-crystal material that has only one crystal). ‰ Grain boundaries are regions between grains of a polycrystalline material.

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Section 1.5 Environmental and Other Effects Effects of following factors must be accounted for in design to ensure that components do not fail unexpectedly: ‰ ‰ ‰ ‰

Temperature Corrosion Fatigue Strain Rate

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Materials Design and Selection

‰ Density is mass per unit volume of a material, usually expressed in units of g/cm3 or lb/in.3 ‰ Strength-to-weight ratio is the strength of a material divided by its density; materials with a high strengthto-weight ratio are strong but lightweight.

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The CES 4 EduPack Unit 1. Mapping the World of Materials: the first step in exploration and selection

New approaches to Materials Education - a course authored by Mike Ashby and Dave Cebon Cambridge, UK © 2002, M.F. Ashby and D. Cebon

Difficulty level 1

Materials, process and shape

Metals, ceramics, glasses

MATERIALS polymers composites... Casting , moulding

PROCESSES powder methods, machining...

Flat and dished sheet

SHAPES prismatic, 3-D

Unit 1, Frame 1.3

© 2002, M.F. Ashby and D. Cebon

The world of materials Steels Cast irons Al-alloys

Metals Cu-alloys Ni-alloys Ti-alloys PE, PP, PC PA (Nylon)

Alumina Si-Carbide

Ceramics, glasses Soda-glass Pyrex

Polymers, elastomers

GFRP CFRP

Butyl rubber Neoprene

Composites KFRP Plywood

Polymer foams Metal foams

Foams Ceramic foams Glass foams

Unit 1, Frame 1.4

Woods

Natural materials Natural fibres: Hemp, Flax, Cotton

© 2002, M.F. Ashby and D. Cebon

Basic material properties Mechanical properties

Thermal expansion

General Density ρ, Mg/m3

Expense:

Cost/kg Cm, $/kg

Mechanical Ductile materials Stress σ

Elastic limit,σy

Stiffness:

Young’s modulus E, GPa

Strength:

Elastic limit σy , MPa

Fracture strength: Tensile strength σts , MPa

lo

l

Thermal strain ε

Weight:

Expansion coefficient, α Temperature, T

Thermal conduction

Brittleness: Fracture toughness Kic , MPa.m1/2

Strain ε

Brittle materials Stress σ

∗ Tensile (fracture) strength, σts

∗ Young’s modulus, E

T1

Thermal Expansion: Expansion coeff. α, 1/K

Area A

To Q joules/sec

Conduction: Thermal conductivity λ, W/m.K Electrical Conductor? Insulator?

Heat flux, Q/A

Young’s modulus, E

x

Thermal conductivity, λ (T1 -T0)/x

Strain ε Unit 1, Frame 1.5

© 2002, M.F. Ashby and D. Cebon

Mechanical properties illustrated Stiff Strong Tough Light

All OK !

Not stiff enough (need bigger E)

Not strong enough (need bigger σy )

Not tough enough (need bigger Kic)

Too heavy (need lower ρ)

Unit 1, Frame 1.6

© 2002, M.F. Ashby and D. Cebon

Materials information for design The goal of design: “To create products that perform their function effectively, safely, at acceptable cost” What do we need to know about materials to do this? Statistical analysis

Data capture

More than just test data.

Selection of material and process

Economic analysis and business case

Mechanical Properties Bulk Modulus Compressive Strength Ductility Elastic Limit Endurance Limit Fracture Toughness Hardness Loss Coefficient Modulus of Rupture Poisson's Ratio Shear Modulus Tensile Strength Young's Modulus

Test

Test data

Characterisation

Unit 1, Frame 1.7

4.1 55 0.06 40 24 2.3 100 0.00950 0.38 0.85 45 2.5 -

4.6 GPa 60 MPa 0.07 45 MPa 27 MPa 2.6 MPa.m1/2 140 MPa 0.026 55 MPa 0.42 0.95 GPa 48 MPa 2.8 GPa

Design data

$ Potential applications

Successful applications

Selection and implementation

© 2002, M.F. Ashby and D. Cebon

Data organisation: materials

Kingdom

Family

• Ceramics • Polymers

Materials

• Metals • Natural • Foams • Composites

Class

Steels Cu-alloys Al-alloys Ti-alloys Ni-alloys Zn-alloys

Member

1000 2000 3000 4000 5000 6000 7000 8000

Attributes

Density Mechanical props. Thermal props.

Structured information

Electrical props. Optical props. Corrosion props. Supporting information -- specific

Unstructured information

-- general

A material record

Unit 1, Frame 1.9

© 2002, M.F. Ashby and D. Cebon

Structured data for ABS* Acrylonitrile-butadiene-styrene (ABS) - (CH2-CH-C6H4)n General Properties Density

1.05 -

1.07 Mg/m^3

Electrical Properties

Price

2.1

2.3

Conductor or insulator?

-

US $/kg

Good insulator

Optical Properties Mechanical Properties

Transparent or opaque?

Young's Modulus

1.1

-

2.9

GPa

Elastic Limit

18

-

50

MPa

Tensile Strength

27

-

55

MPa

Elongation

6

-

8

%

Hardness - Vickers

6

-

15

HV

Endurance Limit

11

-

22

MPa

Fracture Toughness

1.2

-

4.2

MPa.m1/2

Corrosion and Wear Resistance

Thermal Properties Max Service Temp

350 -

370 K

Thermal Expansion

70

75

Specific Heat

1500 -

1510 J/kg.K

Thermal Conductivity 0.17 -

0.24 W/m.K

-

Opaque

10-6/K

Flammability Fresh Water Organic Solvents Oxidation at 500C Sea Water Strong Acid Strong Alkalis UV Wear Weak Acid Weak Alkalis

Average Good Average Very Poor Good Good Good Good Poor Good Good

*Using the CES 4 Level 2 DB Unit 1, Frame 1.10

© 2002, M.F. Ashby and D. Cebon

Unstructured data for ABS* What is it? ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient, and easily molded. It is usually opaque, although some grades can now be transparent, and it can be given vivid colors. ABS-PVC alloys are tougher than standard ABS and, in self-extinguishing grades, are used for the casings of power tools.

Design guidelines. ABS has the highest impact resistance of all polymers. It takes color well. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UV resistant for outdoor application if stabilizers are added. It is hygroscopic (may need to be oven dried before thermoforming) and can be damaged by petroleum-based machining oils. ABS can be extruded, compression moulded or formed to sheet that is then vacuum thermoformed. It can be joined by ultrasonic or hot-plate welding, or bonded with polyester, epoxy, isocyanate or nitrile-phenolic adhesives.

Technical notes. ABS is a terpolymer - one made by copolymerising 3 monomers: acrylonitrile, butadiene and syrene. The acrylonitrile gives thermal and chemical resistance, rubber-like butadiene gives ductility and strength, the styrene gives a glossy surface, ease of machining and a lower cost. In ASA, the butadiene component (which gives poor UV resistance) is replaced by an acrylic ester. Without the addition of butyl, ABS becomes, SAN - a similar material with lower impact resistance or toughness. It is the stiffest of the thermoplastics and has excellent resistance to acids, alkalis, salts and many solvents.

Typical Uses. Safety helmets; camper tops; automotive instrument panels and other interior components; pipe fittings; home-security devices and housings for small appliances; communications equipment; business machines; plumbing hardware; automobile grilles; wheel covers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boat hulls; large components for recreational vehicles; weather seals; glass beading; refrigerator breaker strips; conduit; pipe for drain-waste-vent (DWV) systems.

The environment. The acrylonitrile monomer is nasty stuff, almost as poisonous as cyanide. Once polymerized with styrene it becomes harmless. ABS is FDA compliant, can be recycled, and can be incinerated to recover the energy it contains.

*Using the CES 4 Level 2 DB Unit 1, Frame 1.11

© 2002, M.F. Ashby and D. Cebon

Data, perspective and comparisons z

Handbooks, compilations (see Chapter 13 of The Text)

z

Suppliers’ data sheets

z

The Worldwide Web (e.g. www.matweb.com)

BUT: no perspective, or comparison between material classes

Example: Typical properties of wrought Al-alloys (extract)

Unit 1, Frame 1.12

© 2002, M.F. Ashby and D. Cebon

Using CES 4 to find data

z

Three levels of database (levels 1,2 and 3) Finding data (“browsing”): z

Locate candidate on MATERIALS tree and double click, or

Use the SEARCH facility to find all records contain candidate name, or trade-name, or application z

Demo: finding data for materials

Relationships and comparisons

Unit 1, Frame 1.13

z

Material bar-charts

z

Material property charts

© 2002, M.F. Ashby and D. Cebon

Relationships: property bar-charts

WC

Steel Copper

Young’s modulus, GPa

CFRP Alumina

Zinc

PEEK Glass PP

Fibreboard

Lead PTFE

Metals

Unit 1, Frame 1.14

GFRP

Aluminum

Polymers

Ceramics

Composites

© 2002, M.F. Ashby and D. Cebon

Bar- chart created with CES 4 (Edu1) Low alloy steel

WC BC SiC

High carbon steel Stainless steel

1000

Alumina

Ti-alloys

Young’s modulus (GPa) Young's Modulus (GPa)

100

Cu-alloys Zn-alloys Al-alloys Mg-alloys

10

CFRP Glass Ceramic Acetal, POM Polyester, rigid PS ABS

Silica glass Soda-Lime glass

PUR PE

PC PP

1

Al-SiC Composite

KFRP GFRP Plywood

PTFE Ionomer

0.1

EVA 0.01

Polyurethane Natural Rubber (NR)

1e-003

Neoprene

Metals

Polymers

Ceramics & glass

Composites

1e-004 Materials:\METALS

Materials:\POLYMERS

Materials:\CERAMICS and GLASSES

Materials:\COMPOSITES

Untitled

Unit 1, Frame 1.15

z

Explore relationships

z

Elementary selection (“Find materials with large elastic limit”) © 2002, M.F. Ashby and D. Cebon

Material property- charts: Modulus - Density 1000 Ceramics

Young’s modulus E, (GPa)

100 Composites Woods

10

Metals 1 Foams

Polymers

0.1 Elastomers

0.01 0.1 Unit 1, Frame 1.16

10 1 Density (Mg/m3)

100 © 2002, M.F. Ashby and D. Cebon

Property chart created with CES 4, Level 1

1000

Silicon Carbide Alumina Boron Carbide

Modulus - Density

Silicon

Tungsten Carbides

Steels

Nickel alloys

Al alloys

Copper alloys

Mg alloys

100

Bamboo

CFRP GFRP

Zinc alloys Titanium

Young’s modulus (GPa) Young's Modulus (typical) (GPa)

Wood Lead alloys

Concrete

10

Plywood

PET PVC PUR

PP 1

PE PTFE

Rigid Polymer Foams 0.1

EVA Silicone

Cork 0.01

Flexible Polymer Foams

Polyisoprene Polyurethane Butyl Rubber

1e-003

Neoprene 1e-004 0.01

0.1

1

10

Density (typical) (Mg/m^3)

Density (Mg/m3) Unit 1, Frame 1.18

© 2002, M.F. Ashby and D. Cebon

Property chart created with CES 4, Level 1 1000

Neoprene Flexible foam

Silicone elastomers

Isoprene

Cork Polyoxymethylene (Acetal, POM) 100

Thermalexpansion Expansion (µstrain/K) Thermal (10-6/K)

Mg alloys GFRP (isotropic)

Lead alloys

Zinc alloys

Ni alloys

Al alloys

Stainless steel Ti alloys

Rigid foam

Cu alloys

10

AlN

Wood Bamboo

WC SiC BC

Balsa (l) (ld)

Borosilicate glass

1

CFRP Silica glass Glass Ceramic 0.1

0.01

0.1

1

10

Conductivity Expansion 100

100

Thermal Conductivity (W/m.K)

Thermal conductivity (W/m.K) Unit 1, Frame 1.20

© 2002, M.F. Ashby and D. Cebon

The main points

• A classification system for materials allows data for them to be organised • The data takes several forms: (a) numeric, non-numeric data that can be structured in a uniform way for all materials (b) supporting information specific to a single material, best stored as text and images • The organization allows information to be retrieved accurately and efficiently • Visual presentation of data as bar-charts and property (bubble) charts reveals relationships and allows comparisons

Demo: creating bar and bubble charts with CES 4 Unit 1, Frame 1.21

© 2002, M.F. Ashby and D. Cebon

Some Project Examples

© 2002, M.F. Ashby and D. Cebon