Aluminum generally

Aluminum generally



Due to its characteristics aluminium (chem. symbol Al) is also called the material of the 21st century. Pure aluminium is a silvery-white shiny metal with several outstanding features - lightweight, non-toxic, non-magnetic, non-combustible. It has a solid state, and belongs to metals. Pure aluminium is a quite soft metal. To ensure the required mechanical properties it can be alloyed with other metals - alloying elements.



Main areas of current use of aluminium


  • transport
  • construction
  • machinery and metallurgical industry
  • energy and electrical engineering industry
  • food industry
  • chemical industry (pipes, heat exchangers)
  • recreation industry and sports
  • other application areas (jewellery)
Chemical symbol Al
Lattice K12
Density 2.6989 (pri 0 °C)
Melting point 660.4 °C
Boiling point 2494 °C
Thermal conductivity 247 W.m-1 (pri 25 °C)




Classification of aluminium alloys according to alloying


1xxx group 


This group contains high-quality unalloyed aluminium with a purity of 99.00% or higher. Non-alloyed aluminium is used in a number of areas, particularly in the electrical engineering and chemical industry. It is characterized by its excellent resistance to corrosion, low values of mechanical properties and excellent formability. The most important pollutants are iron and silicon. Typical areas of application are chemical devices, flash lights, heat exchangers, packing material and so on. Strength of around 40 – 60 MPa.



2xxx group


Copper (Cu) is the principal alloying component often with magnesium as the second alloying element. After processing by solution annealing and after work-hardening their mechanical properties are the same as in non-alloy low-carbon steel. Their corrosion resistance can be improved by coating, e.g. by a layer of pure aluminium. The alloys from the 2xxx group are particularly suitable for components and structures requiring a high ratio of strength and weight values. Strength of around 400 MPa.




3xxx group


The principal alloying element is manganese (Mn). For technical reasons, only about 1.5% of manganese may be added to aluminium by alloying, therefore manganese is added as a main ingredient only into several alloys. They are used for the manufacture of measuring instruments, beverage cans, kitchen utensils, canisters and traffic signs.



4xxx group


The principal alloying element is silicon (Si). This can be added in sufficient quantity (up to 12%), to achieve a substantial reduction of the melting point, without increasing fragility. For these reasons, alloys of aluminium and silicon are often used as auxiliary materials in welding and as fasteners. Most of the alloys of this group are not hardened by heat treatment. In anodic oxidation alloys with sufficient quantity of silicon change colour to dark grey up to anthracite and therefore are mainly used in architecture.




5xxx group


The principal alloying element is magnesium (Mg). In combination with manganese (Mn) after hardening the alloy can achieve moderate to high strength. Alloys of this group have a good resistance against corrosion in marine environment. Alloys of this group are used in architecture as decorative frames, as beverage cans, in shipbuilding, for cryogenic purposes, etc. Strength of around 200-350 MPa.



6xxx group

Alloys of the 6xxx group contain silicon and magnesium as alloying elements. After processing by solution annealing (T4) alloys of this group may be formed, and finally by hardening may be transferred to the T6 temper (high strength). In the T4 temper the material is well formable. Typically these alloys have good weldability, machinability, and corrosion resistance. They are used in the manufacture of bicycle frames, means of transport, rails (bridges), etc. Alloys of the 6xxx group are suitable for a surface treatment by anodizing technology. Strength of around 200 – 350 MPa




7xxx group

Zinc is the principal alloying element. Alloys of this group are the strongest of all groups, their strength being in the range of 450-500 MPa, and in some cases it may be 600 MPa. These alloys are susceptible to intergranular corrosion in particular after welding.



8xxx group


Alloys containing other alloying elements (including lithium).




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