Types of Material

IE 351

Lecture 3

Why Materials ???

Ashby,: Material Selection in Mechanical Design

Engineering Materials

Materials

Nanomaterials, shape-memory alloys, superconductors, …

Ferrous metals: carbon-, alloy-, stainless-, tool-and-die steels

Non-ferrous metals: aluminum, magnesium, copper, nickel, titanium, superalloys, refractory metals, beryllium, zirconium, low-melting alloys, gold, silver, platinum, …

Plastics: thermoplastics (acrylic, nylon, polyethylene, ABS,…) thermosets (epoxies, Polymides, Phenolics, …) elastomers (rubbers, silicones, polyurethanes, …)

Ceramics, Glasses, Graphite, Diamond, Cubic Boron Nitride

Composites: reinforced plastics, metal-, ceramic matrix composites

Properties of materials

Mechanical properties of materialsStrength, Toughness, Hardness, Ductility,Elasticity, Fatigue and Creep

Chemical propertiesOxidation, Corrosion, Flammability, Toxicity, …

Physical propertiesDensity, Specific heat, Melting and boiling point,Thermal expansion and conductivity,Electrical and magnetic properties

Material Specification

• Chemical composition

• Mechanical properties – Strength, hardness (under various conditions: temperature, humidity, pressure)

• Physical properties – density, optical, electrical, magnetic

• Environmental – green, recycling

Metals

• Ferrous Metals– Cast irons– Steels

• Super alloys– Iron-based– Nickel-based– Cobalt-based

• Non-ferrous metals– Aluminum and its alloys– Copper and its alloys– Magnesium and its alloys– Nickel and its alloys– Titanium and its alloys– Zinc and its alloys– Lead & Tin– Refractory metals– Precious metals

General Properties and Applications of Ferrous Alloys

• Ferrous alloys are useful metals in terms of mechanical, physical and chemical properties.

• Alloys contain iron as their base metal.

• Carbon steels are least expensive of all metals while stainless steels is costly.

Carbon and alloy steels

Carbon steels

• Classified as low, medium and high:

1. Low-carbon steel or mild steel, < 0.3%C, bolts, nuts and sheet plates.

2. Medium-carbon steel, 0.3% ~ 0.6%C, machinery, automotive and agricultural equipment.

3. High-carbon steel, > 0.60% C, springs, cutlery, cable.

Carbon and alloy steels

Alloy steels

• Steels containing significant amounts of alloying elements.

• Structural-grade alloy steels used for construction industries due to high strength.

• Other alloy steels are used for its strength, hardness, resistance to creep and fatigue, and toughness.

• It may heat treated to obtain the desired properties.

Carbon and alloy steels

High-strength low-alloy steels

• Improved strength-to-weight ratio.

• Used in automobile bodies to reduce weight and in agricultural equipment.

• Some examples are:

1. Dual-phase steels

2. Micro alloyed steels

3. Nano-alloyed steels

Stainless steels• Characterized by their corrosion resistance,

high strength and ductility, and high chromium content.

• Stainless as a film of chromium oxide protects the metal from corrosion.

Stainless steels

• Five types of stainless steels:

1. Austenitic steels

2. Ferritic steels

3. Martensitic steels

4. Precipitation-hardening (PH) steels

5. Duplex-structure steels

Typical Selection of Carbon and Alloy Steels for Various Applications

TABLE 5.1Product Steel Product SteelAircraft forgings,

tubing, fittingsAutomobile bodiesAxlesBall bearings and racesBoltsCamshaftsChains (transmission)Coil springsConnecting rodsCrankshafts (forged)

4140, 8740

10101040, 4140521001035, 4042, 48151020, 10403135, 314040631040, 3141, 43401045, 1145, 3135, 3140

Differential gearsGears (car and truck)Landing gearLock washersNutsRailroad rails and wheelsSprings (coil)Springs (leaf)TubingWireWire (music)

40234027, 40324140, 4340, 87401060313010801095, 4063, 61501085, 4063, 9260, 615010401045, 10551085

Mechanical Properties of Selected Carbon and Alloy Steels in Various Conditions

TABLE 5.2 Typical Mechanical Properties of Selected Carbon and Alloy Steels in the Hot-Rolled,Normalized, and Annealed ConditionAISI Condition Ultimate

tensilestrength(MPa)

YieldStrength(MPa)

Elongation in50 mm (%)

Reduction ofarea (%)

Hardness(HB)

1020

1080

3140

4340

8620

As-rolledNormalizedAnnealedAs-rolled

NormalizedAnnealed

NormalizedAnnealed

NormalizedAnnealed

NormalizedAnnealed

448441393

1010965615891689

1279744632536

346330294586524375599422861472385357

363536121124192412222631

596766172045575036495962

143131111293293174262197363217183149

AISI Designation for High-Strength Sheet Steel

TABLE 5.3Yield Strength Chemical

CompositionDeoxidation

Practice

psi x 103 MPa

35404550607080

100120140

240275310350415485550690830970

S = structural alloy

X = low alloy

W = weathering

D = dual phase

F = killed plus sulfide inclusion control

K = killed

O = nonkilled

Room-Temperature Mechanical Properties and Applications of Annealed Stainless Steels

TABLE 5.4 Room-Temperature Mechanical Properties and Typical Applications of Selected AnnealedStainless Steels

AISI(UNS)

Ultimatetensile

strength(MPa)

Yieldstrength(MPa)

Elongationin 50 mm

(%) Characteristics and typical applications303(S30300)

550–620 240–260 53–50 Screw machine products, shafts, valves, bolts,bushings, and nuts; aircraft fittings; bolts; nuts;rivets; screws; studs.

304(S30400)

565–620 240–290 60–55 Chemical and food processing equipment,brewing equipment, cryogenic vessels, gutters,downspouts, and flashings.

316(S31600)

550–590 210–290 60–55 High corrosion resistance and high creep strength.Chemical and pulp handling equipment,photographic equipment, brandy vats, fertilizerparts, ketchup cooking kettles, and yeast tubs.

410(S41000)

480–520 240–310 35–25 Machine parts, pump shafts, bolts, bushings, coalchutes, cutlery, tackle, hardware, jet engine parts,mining machinery, rifle barrels, screws, andvalves.

416(S41600)

480–520 275 30–20 Aircraft fittings, bolts, nuts, fire extinguisherinserts, rivets, and screws.

Tool and die steels

• Designed for high strength, impact toughness, and wear resistance at a range of temperatures.

Basic Types of Tool and Die Steels

TABLE 5.5Type AISIHigh speed

Hot work

Cold work

Shock resisting

Mold steels

Special purpose

Water hardening

M (molybdenum base)T (tungsten base)H1 to H19 (chromium base)H20 to H39 (tungsten base)H40 to H59 (molybdenum base)D (high carbon, high chromium)A (medium alloy, air hardening)O (oil hardening)SP1 to P19 (low carbon)P20 to P39 (others)L (low alloy)F (carbon-tungsten)W

Processing and Service Characteristics of Common Tool and Die Steels

TABLE 5.6 Processing and Service Characteristics of Common Tool and Die Steels

AISIdesignation

Resistance todecarburization

Resistance tocracking

Approximatehardness(HRC) Machinability Toughness

Resistance tosoftening

Resistance towear

M2 Medium Medium 60–65 Medium Low Very high Very highT1 High High 60–65 Medium Low Very high Very highT5 Low Medium 60–65 Medium Low Highest Very highH11, 12, 13 Medium Highest 38–55 Medium to high Very high High MediumA2 Medium Highest 57–62 Medium Medium High HighA9 Medium Highest 35–56 Medium High High Medium to

highD2 Medium Highest 54–61 Low Low High High to very

highD3 Medium High 54–61 Low Low High Very highH21 Medium High 36–54 Medium High High Medium to

highH26 Medium High 43–58 Medium Medium Very high HighP20 High High 28–37 Medium to high High Low Low to

mediumP21 High Highest 30–40 Medium Medium Medium MediumW1, W2 Highest Medium 50–64 Highest High Low Low to

medium

Source: Adapted from Tool Steels, American Iron and Steel Institute, 1978.

Aluminium and aluminium alloys• Factors for selecting are:

1. High strength to weight ratio

2. Resistance to corrosion

3. High thermal and electrical conductivity

4. Ease of machinability

5. Non-magnetic

Magnesium and magnesium alloys• Magnesium (Mg) is the lightest metal.

• Alloys are used in structural and non-structural applications.

• Typical uses of magnesium alloys are aircraft and missile components.

• Also has good vibration-damping characteristics.

Copper and copper alloys

• Copper alloys have electrical and mechanical properties, corrosion resistance, thermal conductivity and wear resistance.

• Applications are electronic components, springs and heat exchangers.

• Brass is an alloy of copper and zinc.

• Bronze is an alloy of copper and tin.

Nickel and nickel alloys

• Nickel (Ni) has strength, toughness, and corrosion resistance to metals.

• Used in stainless steels and nickel-base alloys.

• Alloys are used for high temperature applications, such as jet-engine components and rockets.

Superalloys• Superalloys are high-temperature alloys use

in jet engines, gas turbines and reciprocating engines.

Titanium and titanium alloys

• Titanium (Ti) is expensive, has high strength-to-weight ratio and corrosion resistance.

• Used as components for aircrafts, jet-engines, racing-cars and marine crafts.

Refractory metals

• Refractory metals have a high melting point and retain their strength at elevated temperatures.

• Applications are electronics, nuclear power and chemical industries.

• Molybdenum, columbium, tungsten, and tantalum are referred to as refractory metal.

Other nonferrous metals

1. Beryllium

2. Zirconium

3. Low-melting-point metals: - Lead- Zinc- Tin

4. Precious metals: - Gold - Silver- Platinum

Special metals and alloys

1. Shape-memory alloys (i.e. eyeglass frame, helical spring)

2. Amorphous alloys (Metallic Glass)

3. Nanomaterials

4. Metal foams

Heat Treatment of Metals

• Annealing– Full annealing– Normalising (faster rate of cooling)– Recovery annealing (longer holding time, slower

rate of cooling,)– Stress relieving (lower temperature)

• Martensite formation in steel– Austenitizing (conversion to austenite)– Quenching (control cooling rate– Tempering (reduce brittleness)

Heat Treatment of Metals

• Precipitation hardening– Solution treatment (-phase conversion)– quenching– precipitation treatment (aging)

• Surface hardening– Carburizing– Nitriding– Carbonitriding– Chromizing and Boronizing

Heat Treatment of Steel

Precipitation Hardening

Solution treatment

Quenching

Precipitation treatment

Furnaces for Heat Treatment

• Fuel fire furnaces– gas– oil

• Electric furnaces– batch furnaces

• box furnaces - door

• car-bottom furnaces - track for moving large parts

• bell-type furnaces - cover/bell lifted by gantry crane

– continuous furnaces

Furnaces for Heat Treatment

• Vacuum furnaces

• Salt-bath furnaces

• Fluidized-bed furnaces

Some of the furnaces have special atmosphere requirements, such as carbon- and nitrogen- rich atmosphere.

Surface Hardening Methods

• Flame hardening

• Induction heating

• High-frequency resistance heating

• Electron beam heating

• Laser beam heating

Surface Hardening Methods

Inductionheating

High frequencyresistanceheating

Classification of Ceramics

• Ceramics– Traditional ceramics– New ceramics– Glass

Ceramics

• Traditional ceramics– clays: kaolinite– silica: quartz, sandstone– alumina– silicon carbide

• New ceramics– oxide ceramics : alumina– carbides : silicon carbide, titanium carbide, etc.– nitrides : silicon nitride, boron nitiride, etc.

Glass

• Glass products– window glass– containers– light bulb glass– laboratory glass– glass fibers– optical glass

• Glass ceramics - polycrystalline structure

Classification of Polymers

– Thermoplastics

– Thermosets

– Elastomers

Polymers

• Thermoplastics - reversible in phase by heating and cooling. Solid phase at room temperature and liquid phase at elevated temperature.

• Thermosets - irreversible in phase by heating and cooling. Change to liquid phase when heated, then follow with an irreversible exothermic chemical reaction. Remain in solid phase subsequently.

• Elastomers - Rubbers

Thermoplastics

– Acetals– Acrylics - PMMA– Acrylonitrile-Butadiene-Styrene - ABS– Cellulosics– Fluoropolymers - PTFE , Teflon– Polyamides (PA) - Nylons, Kevlar– Polysters - PET– Polyethylene (PE) - HDPE, LDPE– Polypropylene (PP)– Polystyrene (PS)– Polyvinyl chloride (PVC)

Thermosets

• Amino resins

• Epoxies

• Phenolics

• Polyesters

• Polyurethanes

• Silicones

Elastomers• Natural rubber

• Synthetic rubbers– butadiene rubber– butyl rubber– chloroprene rubber– ethylene-propylene rubber– isoprene rubber– nitrile rubber– polyurethanes– silicones– styrene-butadiene rubber– thermoplastic elastomers

Classification of Composite Materials

– Metal Matrix Composites

– Ceramic Matrix Composites

– Polymer Matrix Composites

Composite Materials

• Metal Matrix Composites (MMC)Mixture of ceramics and metals reinforced by strong,

high-stiffness fibers

• Ceramic Matrix Composites (CMC)Ceramics such as aluminum oxide and silicon carbide

embedded with fibers for improved properties, especially high temperature applications.

• Polymer Matrix Composites (PMC)Thermosets or thermoplastics mixed with fiber

reinforcement or powder.

Composite Materials

1D fibre

Woven fabric

Random fibre

Composite Materials

Taxonomy of Materials Selection

Ashby,: Material Selection in Mechanical Design