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Lecture 3

Types of metals alloys

General Material Classifications

Metals

Ferrous Alloys

 Those with iron as prime constituent (except for high alloy steel)
 Important as engineering construction material (especially steel Fe-C) is

because:

 They important – Abundant within the earth-crust – low cost
 Easier to be produced
 Good strength toughness and ductility
 Versatile – wide range of mechanical and physical properties

Lecture 3

Types of metals alloys

Can be alloyed and heat treated to get desired mechanical properties

 Alloying is combining or mixing other material like carbon or other

metals to iron

 Heat treatment is a process of heating and cooling a metal to achieve

specific microstructure which in turns display specific mechanical

properties (e.g. Quenching austenite gives martensite witch be treated

to martensite which is can heat (tempered) produced tempered more

ductile

Nomenclature of Ferrous Alloys

Nomenclature AISI (American Iron and Steel Institute) & SAE (Society of

Automotive Engineers)

10xx Plain Carbon Steels

11xx Plain Carbon Steels (resulfurized for machinability)

15xx Mn (10 ~ 20%)

40xx Mo (0.20 ~ 0.30%)

43xx Ni (1.65 - 2.00%), Cr (0.4 - 0.90%), Mo (0.2 - 0.3%)

44xx Mo (0.5%)

where xx is wt% C x 100

example: 1060 steel – plain carbon steel with 0.60 wt% C

Stainless Steel -- >11% Cr – AISI number e.g. 409

Iron-C phase Digram

Lecture 3

Types of metals alloys

Low Carbon steel

 Alloys of low carbon steel being produced in the greatest quantity
 <0.25wt %C
 Consists of ferrites and pearlites and weak but can be treated to achieve high

strength

 Machineable, weldable and cheaper to be produced
 Types:

Plain low carbon steel

 no alloying, variable tensile strength (TS) (415-550)MPa and Yield Strength

(YS) = 275MPa

 Applications –– crankshafts, bolts, hammers, hand tools, gears, knives

High strength low allow (HSLA)

 with alloying, higher TS and YS
 Applications –– automobiles opines, nails, wire, pipe structural and sheet,

steel, railway cars

Medium Carbon Steel

 0.25 –– 0.6 wt %C
 Heat treated to achieve good mechanical properties
 Used tampered condition (tampered martinsitic)
 Strength - ductility combination can be tailored by heat treatment and alloying

(with Ni, Cr and Mo)

 Applications: high strength structural components –– railway wheels, tracks,

crankshafts

High Carbon Steel

 0.6 –– 1.4 %C wt
 Hardest, strongest and least ductile carbon steel
 Used in harden and tempered conditions
 Can be alloyed with carbon and other metals to form vary hard and wear

resistance material (e.g C, Cr, Ni, W, Mo and V)

 Applications: cutting tools, drills, embossing dies, saws, cutlery, paper cutters,

concrete drill, blacksmith tools.

Lecture 3

Types of metals alloys

Stainless--Steels

 Highly resistance alloy to corrosion (rusting) in a variety of environment.

Mechanical integrity maintains

 Consisting of iron-- carbon and > 11 wt% Cr. Ni, Mn may also be present
 Example 0.08 C, 11.0 Cr, 1. Mn, 0.50 Ni, 0.75 Ti : S40900

Cast Irons

 3.0-4.5 wt% C
 Liquid at 1150-1300

 Easily melted and amenable to casting

Gray Iron

 graphite flakes
 weak& brittle under tension
 stronger under compression
 excellent vibrational dampening
 wear resistant
 used e.g. as base structure for machines and heavy equipment

Ductile Iron

 add Mg or Ce
 graphite in nodules not flakes
 matrix often pearlite- better ductility
 Applications: valves, pump bodies, gears, crankshafts

White Iron

 < 1wt% Si so harder but brittle
 more cementite
 Typical applications: connecting rods, transmission gears, pipe fittings,

flanges

Malleable Iron

- heat treat at 800-900

- graphite in rosettes
- more ductile

Lecture 3

Types of metals alloys

Nonferrous alloys

Aluminum and its Alloys

Pure aluminum is a silvery-white metal with many desirable characteristics. It is light,

nontoxic (as the metal), nonmagnetic and nonsparking. It is easily formed, machined,

and cast. Pure aluminum is soft and lacks strength, but alloys with small amounts of

copper, magnesium, silicon, manganese, and other elements have very useful

properties. Aluminum is an abundant element in the earth's crust, but it is not found

free in nature. The Bayer process is used to refine aluminum from bauxite, an

aluminum ore. Because of aluminum's mechanical and physical properties, it is an

extremely convenient and widely used metal. Aluminium alloys can be classified as;

cast or wrought alloys, examples are; Al--Li, Al-Cu-Si etc

Properties



Very lightweight (about 1/3 the mass of an equivalent volume of steel or

copper) but with alloying can become very strong.



excellent thermal conductor



excellent electrical conductor (on a weight-for-mass basis, aluminium will

conduct more than twice as much electricity as copper)



highly reflective to radiant energy in the electromagnetic spectrum



highly corrosion resistant in air and water (including sea water)



highly workable and can be formed into almost any structural shape



non-magnetic



non-toxic

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Types of metals alloys

Applications

 door and window frames
 high tension power lines, wires, cables, bus bars, components for television,

radios, refrigerators and air-conditioners

 beverage cans, bottle tops
 propellers, airplane and vehicle body sheet, gear boxes, motor parts
 Al-Cu food/ chemicals handing and storage equipments.
 Al-Cu-Mn-Zn- Cooking utensils.
 Al-Zn-Mg-Cu-Cr

Aircraft structural parts

Copper and its Alloys

Properties

 Good thermal and electrical conductivity
 Ease of forming, ease of joining, and color.
 However, copper and its alloys have relatively low strength-to-weight ratios
 Low strengths at elevated temperatures.
 Copper is resistant to corrosion in most atmospheres including marine and

industrial environments. It is corroded by oxidizing acids, halogens, sulphides

and ammonia based solutions

 Copper and its alloys -- the brasses and bronzes -- are available in rod, plate,

strip, sheet, tube shapes, forgings, wire, and castings.

Applications

 Pure Cu

Electrical and thermal conductors (cast Cu), transistor components,

coaxial cables rectifiers, lead in wires (cold--worked Cu)

 Cu- Be- Co

moulds for plastic parts, bearings, valves, gears(cast Cu)

 Cu--30Zn & Cu --40Zn (cold --work brass)

fasteners, locks, heal exchange

components, large nuts and bolts, plumbing accessories, pints and rivets.

 Cu--4Si

bearing, belts, marine fittings

Lecture 3

Types of metals alloys

Magnesium and its Alloys

Properties

 Low density metal (1.7g/cm

)

 limited cold working
 Relatively soft low elastic modulus
 Easily oxidized
 Magnesium is expensive compared to Al
 Mg is difficult to cast and it burn in air (handling must be with care and cannot

be used temperature at high)

 Mg- Al- Zn alloys –– improve strength

Applications

 Mg--alloys replace engineering plastics that have similar densities
 Handheld devices (chain saw, power told etc)
 Automobiles (steering wheels, tyre ream, seat, frames)
 Laptop computers, cam coders, TV etc

Titanium and its Alloys

Properties

 Low density metal (4.5 g/cm cm

)

 High melting point = 1668

 elastic modulus = 107MPa
 Chemical reactivity with other material at elevated temperatures
 Corrosion resistance
 Ti—alloys ,very high elastic modulus ~1400MPa, easily forged and machined,

high ductility

Applications

•

Pure Ti - Jet engine cases and airframe skins, corrosion--resistance equipment

for marine's applications chemical processing, industries.

•

Ti--5Al--2.55Sn – Gas turbine engine casing

•

Ti--6Al-4V – High strength prosthetic implants, orthopedics, airframe

structured components

Lecture 3

Types of metals alloys

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.

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

Lecture 3

Types of metals alloys