Aluminium - Specifications, Properties, Classifications and Classes, Supplier Data by Aalco

Topics Covered

Background

Production Of Aluminium

Annual Demand of Aluminium

Applications of Aluminium

Alloy Designations

Physical Properties of Aluminium

Density of Aluminium

Strength of Aluminium

Corrosion Resistance of Aluminium

Thermal Conductivity of Aluminium

Electrical Conductivity of Aluminium

Reflectivity of Aluminium

Mechanical Properties of Aluminium

Aluminium Standards

Heat Treatment of Aluminium

Work Hardening of Aluminium

Background

Aluminium is the world’s most abundant metal and is the third most common element comprising 8% of the earth’s crust. The versatility of aluminium makes it the most widely used metal after steel.

Production of Aluminium

Aluminium is derived from the mineral bauxite. Bauxite is converted to aluminium oxide (alumina) via the Bayer Process. The alumina is then converted to aluminium metal using electrolytic cells and the Hall-Heroult Process.

Annual Demand of Aluminium

Worldwide demand for aluminium is around 29 million tons per year. About 22 million tons is new aluminium and 7 million tons is recycled aluminium scrap. The use of recycled aluminium is economically and environmentally compelling. It takes 14,000 kWh to produce 1 tonne of new aluminium. Conversely it takes only 5% of this to remelt and recycle one tonne of aluminium. There is no difference in quality between virgin and recycled aluminium alloys.

Applications of Aluminium

Pure aluminium is soft, ductile, corrosion resistant and has a high electrical conductivity. It is widely used for foil and conductor cables, but alloying with other elements is necessary to provide the higher strengths needed for other applications. Aluminium is one of the lightest engineering metals, having a strength to weight ratio superior to steel.

By utilising various combinations of its advantageous properties such as strength, lightness, corrosion resistance, recyclability and formability, aluminium is being employed in an ever-increasing number of applications. This array of products ranges from structural materials through to thin packaging foils.

Alloy Designations

Aluminium is most commonly alloyed with copper, zinc, magnesium, silicon, manganese and lithium. Small additions of chromium, titanium, zirconium, lead, bismuth and nickel are also made and iron is invariably present in small quantities.

There are over 300 wrought alloys with 50 in common use. They are normally identified by a four figure system which originated in the USA and is now universally accepted. Table 1 describes the system for wrought alloys. Cast alloys have similar designations and use a five digit system.

Table 1. Designations for wrought aluminium alloys.

Alloying Element

Wrought

None (99%+ Aluminium)

1XXX

Copper

2XXX

Manganese

3XXX

Silicon

4XXX

Magnesium

5XXX

Magnesium + Silicon

6XXX

Zinc

7XXX

Lithium

8XXX

For unalloyed wrought aluminium alloys designated 1XXX, the last two digits represent the purity of the metal. They are the equivalent to the last two digits after the decimal point when aluminium purity is expressed to the nearest 0.01 percent. The second digit indicates modifications in impurity limits. If the second digit is zero, it indicates unalloyed aluminium having natural impurity limits and 1 through 9, indicate individual impurities or alloying elements.

For the 2XXX to 8XXX groups, the last two digits identify different aluminium alloys in the group. The second digit indicates alloy modifications. A second digit of zero indicates the original alloy and integers 1 to 9 indicate consecutive alloy modifications.

Physical Properties of Aluminium

Density of Aluminium

Aluminium has a density around one third that of steel or copper making it one of the lightest commercially available metals. The resultant high strength to weight ratio makes it an important structural material allowing increased payloads or fuel savings for transport industries in particular.

Strength of Aluminium

Pure aluminium doesn’t have a high tensile strength. However, the addition of alloying elements like manganese, silicon, copper and magnesium can increase the strength properties of aluminium and produce an alloy with properties tailored to particular applications.

Aluminium is well suited to cold environments. It has the advantage over steel in that its’ tensile strength increases with decreasing temperature while retaining its toughness. Steel on the other hand becomes brittle at low temperatures.

Corrosion Resistance of Aluminium

When exposed to air, a layer of aluminium oxide forms almost instantaneously on the surface of aluminium. This layer has excellent resistance to corrosion. It is fairly resistant to most acids but less resistant to alkalis.

Thermal Conductivity of Aluminium

The thermal conductivity of aluminium is about three times greater than that of steel. This makes aluminium an important material for both cooling and heating applications such as heat-exchangers. Combined with it being non-toxic this property means aluminium is used extensively in cooking utensils and kitchenware.

Electrical Conductivity of Aluminium

Along with copper, aluminium has an electrical conductivity high enough for use as an electrical conductor. Although the conductivity of the commonly used conducting alloy (1350) is only around 62% of annealed copper, it is only one third the weight and can therefore conduct twice as much electricity when compared with copper of the same weight.

Reflectivity of Aluminium

From UV to infra-red, aluminium is an excellent reflector of radiant energy. Visible light reflectivity of around 80% means it is widely used in light fixtures. The same properties of reflectivity makes aluminium ideal as an insulating material to protect against the sun’s rays in summer, while insulating against heat loss in winter.

Table 2. Typical properties for aluminium.

Property

Value

Atomic Number

13

Atomic Weight (g/mol)

26.98

Valency

3

Crystal Structure

FCC

Melting Point (°C)

660.2

Boiling Point (°C)

2480

Mean Specific Heat (0-100°C) (cal/g.°C)

0.219

Thermal Conductivity (0-100°C) (cal/cms. °C)

0.57

Co-Efficient of Linear Expansion (0-100°C) (x10-6/°C)

23.5

Electrical Resistivity at 20°C (&#937.cm)

2.69

Density (g/cm3)

2.6898

Modulus of Elasticity (GPa)

68.3

Poissons Ratio

0.34

Mechanical Properties of Aluminium

Aluminium can be severely deformed without failure. This allows aluminium to be formed by rolling, extruding, drawing, machining and other mechanical processes. It can also be cast to a high tolerance.

Alloying, cold working and heat-treating can all be utilised to tailor the properties of aluminium.

The tensile strength of pure aluminium is around 90 MPa but this can be increased to over 690 MPa for some heat-treatable alloys.

Table 3. Mechanical properties of selected aluminium alloys.

Alloy

Temper

Proof Stress 0.2% (MPa)

Tensile Strength (MPa)

Shear Strength (MPa)

Elongation A5 (%)

Hardness Vickers (HV)

AA1050A

H12

H14

H16

H18

0

85

105

120

140

35

100

115

130

150

80

60

70

80

85

50

12

10

7

6

42

30

36

-

44

20

AA2011

T3

T6

290

300

365

395

220

235

15

12

100

115

AA3103

H14

0

140

45

155

105

90

70

9

29

46

29

AA4015

0

H12

H14

H16

H18

45

110

135

155

180

110-150

135-175

160-200

185-225

210-250

-

-

-

-

-

20

4

3

2

2

30-40

45-55

-

-

-

AA5083

H32

0/H111

240

145

330

300

185

175

17

23

95

75

AA5251

H22

H24

H26

0

165

190

215

80

210

230

255

180

125

135

145

115

14

13

9

26

65

70

75

46

AA5754

H22

H24

H26

0

185

215

245

100

245

270

290

215

150

160

170

140

15

14

10

25

75

80

85

55

AA6063

0

T4

T6

50

90

210

100

160

245

70

11

150

27

21

14

85

50

80

AA6082

0

T4

T6

60

170

310

130

260

340

85

170

210

27

19

11

35

75

100

AA6262

T6

T9

240

330

290

360

-

-

8

3

-

-

AA7075

0

T6

105-145

435-505

225-275

510-570

150

350

9

5

65

160

Aluminium Standards

The old BS1470 standard has been replaced by nine EN standards. The EN standards are given in table 4.

Table 4. EN standards for aluminium

Standard

Scope

EN485-1

Technical conditions for inspection and delivery

EN485-2

Mechanical properties

EN485-3

Tolerances for hot rolled material

EN485-4

Tolerances for cold rolled material

EN515

Temper designations

EN573-1

Numerical alloy designation system

EN573-2

Chemical symbol designation system

EN573-3

Chemical compositions

EN573-4

Product forms in different alloys

The EN standards differ from the old standard, BS1470 in the following areas:

  • Chemical compositions – unchanged.
  • Alloy numbering system – unchanged.
  • Temper designations for heat treatable alloys now cover a wider range of special tempers. Up to four digits after the T have been introduced for non-standard applications (e.g. T6151).
  • Temper designations for non heat treatable alloys – existing tempers are unchanged but tempers are now more comprehensively defined in terms of how they are created. Soft (O) temper is now H111 and an intermediate temper H112 has been introduced. For alloy 5251 tempers are now shown as H32/H34/H36/H38 (equivalent to H22/H24, etc). H19/H22 & H24 are now shown separately.
  • Mechanical properties – remain similar to previous figures. 0.2% Proof Stress must now be quoted on test certificates.
  • Tolerances have been tightened to various degrees.

Heat Treatment of Aluminium

A range of heat treatments can be applied to aluminium alloys:

  • Homogenisation – the removal of segregation by heating after casting.
  • Annealing – used after cold working to soften work-hardening alloys (1XXX, 3XXX and 5XXX).
  • Precipitation or age hardening (alloys 2XXX, 6XXX and 7XXX).
  • Solution heat treatment before ageing of precipitation hardening alloys.
  • Stoving for the curing of coatings
  • After heat treatment a suffix is added to the designation numbers.
  • The suffix F means “as fabricated”.
  • O means “annealed wrought products”.
  • T means that it has been “heat treated”.
  • W means the material has been solution heat treated.
  • H refers to non heat treatable alloys that are “cold worked” or “strain hardened”.

The non-heat treatable alloys are those in the 3XXX, 4XXX and 5XXX groups.

Table 5. Heat treatment designations for aluminium and aluminium alloys.

Term

Description

T1

Cooled from an elevated temperature shaping process and naturally aged.

T2

Cooled from an elevated temperature shaping process cold worked and naturally aged.

T3

Solution heat-treated cold worked and naturally aged to a substantially.

T4

Solution heat-treated and naturally aged to a substantially stable condition.

T5

Cooled from an elevated temperature shaping process and then artificially aged.

T6

Solution heat-treated and then artificially aged.

T7

Solution heat-treated and overaged/stabilised.

Work Hardening of Aluminium

The non-heat treatable alloys can have their properties adjusted by cold working. Cold rolling is a typical example.

These adjusted properties depend upon the degree of cold work and whether working is followed by any annealing or stabilising thermal treatment.

Nomenclature to describe these treatments uses a letter, O, F or H followed by one or more numbers. As outlined in Table 6, the first number refers to the worked condition and the second number the degree of tempering.

Table 6. Non-Heat treatable alloy designations

Term

Description

H1X

Work hardened

H2X

Work hardened and partially annealed

H3X

Work hardened and stabilized by low temperature treatment

H4X

Work hardened and stoved

HX2

Quarter-hard – degree of working

HX4

Half-hard – degree of working

HX6

Three-quarter hard – degree of working

HX8

Full-hard – degree of working

Table 7. Temper codes for plate

Code

Description

H112

Alloys that have some tempering from shaping but do not have special control over the amount of strain-hardening or thermal treatment. Some strength limits apply.

H321

Strain hardened to an amount less than required for a controlled H32 temper.

H323

A version of H32 that has been hardened to provide acceptable resistance to stress corrosion cracking.

H343

A version of H34 that has been hardened to provide acceptable resistance to stress corrosion cracking.

H115

Armour plate.

H116

Special corrosion-resistant temper.

Source: Aalco

For more information on this source please visit Aalco

DISCLAIMER

This Data is indicative only and must not be seen as a substitute for the full specification from which it is drawn. In particular, the mechanical property requirements vary widely with temper, product and product dimensions. The information is based on our present knowledge and is given in good faith. However, no liability will be accepted by the Company is respect of any action taken by any third party in reliance thereon.

As the products detailed may be used for a wide variety of purposes and as the Company has no control over their use; the Company specifically excludes all conditions or warranties expressed or implied by statute or otherwise as to dimensions, properties and/or fitness for any particular purpose.

Any advice given by the Company to any third party is given for that party’s assistance only and without liability on the part of the Company. Any contract between the Company and a customer will be subject to the company’s Conditions of Sale. The extent of the Company’s liabilities to any customer is clearly set out in those Conditions; a copy of which is available on request.

Date Added: May 17, 2005 | Updated: Jul 15, 2013
Comments
  1. Aslam Hameed Aslam Hameed Islamic Republic of Pakistan says:

    By nitriding can we increase hardness vicker of Al and by how much?

  2. Abdur Rehman Yousaf Abdur Rehman Yousaf Islamic Republic of Pakistan says:

    How can we soften hard aluminium material?

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