Aluminium
Property
Constituents
Aluminium is not found in its pure state, but i combination with other elements. It contains approximately 15% of Al2O3 (8% aluminium) [3].
Typical composition of commercially pure aluminium:
| Al | Si | Fe | Cu | Mn | Mg | Zn | Ti |
| 99.5% | 0.2% | 0.2 % max | 0.04% max | 0.03 % max | 0.03 % max | 0.03 % max | 0.03 % max |
Alloy Types
- Copper
- Manganese
- Silicon
- Magnesium
- Zinc
Classification
According to BS 1490, casting alloys are designated by numbers in sequence of development which would be preceded by the letters LM (light metal), i.e. LM6.
Dimension
BS 1161 standard extruded sections – range of sizes:
| Section type | Size range (mm) |
| Equal angles | 30 x 30-120 x 120 |
| Unequal angles | 50 x 38-140 x 105 |
| Channels | 60 x 30-240 x 100 |
| T-sections | 50 x 38-120 x 90 |
| I-sections | 60 x 30-160 x 80 |
| Equal bulb angles | 50 x 50-120 x 120 |
| Unequal bulb angles | 50 x 37.5-140 x 105 |
| Lipped channels | 80 x 40-140 x 70 |
| Bulb T-sections | 90 x 75-180 x 150 |
For curtain wall and cladding framing member, the dimension of the aluminium extrusion would be modified and custom-made.
Workability
It can be riveted, bolted, welded, brazed and soldered.
Solubility of other metals
Silicon, copper, iron, zinc, tin, manganese dissolve readily in aluminium. Sodium and potassium are practically insoluble in it, and titanium, vanadium, boron, nickel, and chromium have low solubility. Hydrogen is the only gas soluble in aluminium to any extent.
| Physical Properties | Pure aluminium | Alloys |
| Density | 2.6898 g/cm-3 | Cast and wrought alloys: 2.66-2.80 g/cm-3 |
| Elastic Modulus | 68.3GPa | High strength copper bearing alloys: 74 GPa |
| Thermal Expansion | 23.5 x 10-6 /ºC ( 10-100 ºC) | Casting alloys: 20-25 x 10-6 /ºC
Wrought alloys: 20-24 x 10-6 /ºC |
| Thermal Conductivity | 244 W/m ºC | Casting alloys: < 100 W/m ºC f
Wrought alloys: 109 W/m ºC |
| Electrical
– Conductivity – Resistivity |
63% of IACS 2.69 µ cm at 20ºC |
< 28% IACS > 6 µ cm at 20ºC |
| Melting Point | 660ºC | 530ºC |
| Reflectivity | 80%-85% of visible incident radiation and about 90%of heat will be reflected if it is with a clean bright surface.
Emissivity: 0.30 for a wavelength of 0.65 µmm. |
|
| Creep | significant at room temperature | significant at 200-250ºC |
| Fatigue Strength | 20MPa at 50 x 106 cycles range | High manganese contents will exhibit higher values. It may be drastically reduced by unsatisfactory weld details. |
| Properties at elevated temperatures | > 100ºC: strength reduction
200ºC: half strength of that at room temperature |
> 100ºC: strength reduction
200ºC: half strength of that at room temperature 350ºC: lose strength |
| Properties at low temperatures | < 0ºC: Higher tensile strength and elongations than of that at room temperature. | |
| Fire | Where fire resistance is required, sufficient insulation must be provided to prevent the temperature of metal from rising above 200ºC | |