Aluminum alloys

The material. Aluminum was once so rare and precious that the Emperor Napoleon III of France had a set of cutlery made from it that cost him more than silver. But that was 1860; today, nearly 150 years later, aluminum spoons are things you throw away—a testament to our ability to be both technically creative and wasteful. Aluminum, the first of the "light alloys" (with magnesium and titanium), is the third most abundant metal in the Earth’s crust (after iron and silicon), but extracting it costs much energy. It has grown to be the second most important metal in the economy (steel comes first) and the mainstay of the aerospace industry.

Composition

Al + alloying elements, e. g., Mg, Mn, Cr, Cu, Zn, Zr, Li

General properties

Density

2500 –

2900

kg/m3

Price

2.5 –

2.8

USD/kg

Mechanical properties

Young’s modulus

68 –

82

GPa

Yield strength (elastic limit)

30 –

550

MPa

Tensile strength

58 –

550

MPa

Elongation

1 –

44%

Hardness—Vickers

12 –

150

HV

Fatigue strength at 107 cycles

22 –

160

MPa

Fracture toughness

22 –

35

MPa. m1/2

Thermal properties

Melting point

495 –

640

°C

Service temperature

120 –

200

°C Maximum

Thermal conductor or insulator?

Good conductor

Thermal conductivity

76 –

240

W/m. K

Specific heat capacity

860 –

990

J/kg. K

Thermal expansion coefficient

21 –

24

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Good conductor

Electrical resistivity

2.5 –

6

puhm. cm

Cast and wrought aluminum alloys, examples of the wide range of properties of this, the most widely used light alloy.

Ecoproperties: material

Annual world production

33 X 106 –

34 X 106

tonne/yr

Reserves

20 X 109 –

2.2 X 109

tonne

Embodied energy, primary production

200 –

240

MJ/kg

CO2 footprint, primary production

11 –

13

kg/kg

Water usage

*125 –

375

l/kg

Eco-indicator

740 –

820

millipoints/kg

Ecoproperties: processing

Casting energy

*2.4 –

2.9

MJ/kg

Casting CO2 footprint

*0.14 –

0.17

kg/kg

Deformation processing energy

*2.4 –

2.9

MJ/kg

Deformation processing CO2 footprint

*0.19 –

0.23

kg/kg

Recycling

Embodied energy, recycling

18 –

21

MJ/kg

CO2 footprint, recycling

1.1 –

1.2

kg/kg

Recycle fraction in current supply

33 –

55

%

Typical uses. Aerospace engineering; automotive engineering—pistons, clutch housings, exhaust manifolds; sports equipment such as golf clubs and bicycles; die-cast chassis for household and electronic products; siding for buildings; reflecting coatings for mirrors; foil for containers and packag­ing; beverage cans; electrical and thermal conductors.