Aluminum and its alloys
General characteristics of aluminium
Due to its properties, aluminium ( Aluminium - chem. mark Al) is also called the material of the 21st century. Pure aluminium is a silvery metal with several excellent properties - lightweight, non-toxic, non-magnetic, non-flammable. It is a solid state metal. Pure aluminium is a relatively soft metal. It can be alloyed with other metals - alloying elements - to provide the required mechanical properties.
The main areas of application of aluminium today
- transport
- construction
- engineering and metallurgical industry
- energy and electrical industry
- food industry
- chemical industry (pipelines, exchangers)
- recreational industry and sport
- other applications (jewellery)
- division of aluminium alloys according to alloying
1xxx group
This group contains high quality unalloyed aluminium with a purity of 99.00% or higher. Unalloyed aluminium is used in many areas, especially in the electrical and chemical industries. It is characterised by excellent corrosion resistance, low mechanical properties and excellent formability. The most important contaminants are iron and silicon. Typical areas of application are chemical instruments, reflectors, heat exchangers, packaging material, etc. Strength around 40 - 60 MPa.
2xxx group
Copper (Cu) is the main alloying element, often with magnesium as a second alloying element. After processing by dissolution annealing and after cold hardening, their mechanical properties are the same as those of non-alloyed low carbon steels. Their corrosion resistance can be improved by coating them with, for example, a layer of pure aluminium. Alloys of the 2xxx group are particularly suitable for parts and structures that require a high strength-to-weight ratio. A strength of around 400 MPa.
3xxx group
The main alloying element is manganese (Mn. For technical reasons, only about 1.5% manganese can be added to aluminium by alloying, so manganese is added as a major component in only a few alloys. They are used to make gauges such as beverage cans, kitchen utensils, jerry cans and road signs.
4xxx group
The main alloying element is silicon (Si). This can be added in sufficient quantities (up to 12%) to achieve a substantial lowering of the melting point without increasing embrittlement. For these reasons, aluminium-silicon alloys are often used as welding additives and as fasteners. Most alloys in this group are not hardened by heat treatment. Alloys with sufficient silicon will turn dark grey to anthracite in colour on anodic oxidation and are therefore used mainly in architecture.
5xxx group
The main alloying element is magnesium (Mg). In combination with manganese (Mn), the alloy can achieve average to high hardness after hardening. Alloys from this group have good corrosion resistance in the marine environment. Alloys of this group are used in architecture, as decorative frames, as beverage cans, in shipbuilding, for cryogenic purposes, etc. Strength around 200-350 MPa.
6xxx group
Alloys of the 6xxx group contain the alloying elements silicon and magnesium. Alloys of this group can be shaped after processing by solution annealing (T4 state) and finally can be converted to the T6 state (high hardness) by hardening. In the T4 state the material is well formable. Usually the weldability, corrosion resistance and machinability of these alloys are good. They are used in the manufacture of bicycle frames, vehicle frames, railings (bridges), etc. Alloys of the 6xxx group are suitable for surface treatment by anodic oxidation technology. Strength around 200 - 350 MPa.
7xxx group
The alloying element is zinc. The alloys of this group are the strongest alloys of all the groups, with strengths in the range of 450-500 MPa and in some cases can be 600 MPa. These alloys are susceptible to intergranular corrosion especially after welding.
8xxx group
Alloys containing other alloying elements (including lithium).