Aspects of Metallurgy
There are a number of different factors that affect the performance of aluminium. We have therefore included a brief overview of the metallurgy of this versatile metal.
In commercially pure form aluminium has relatively low strength and is fairly soft and ductile.
By adding small amounts of other elements to aluminium significant improvements to its properties are made. These metals include copper, magnesium, manganese, silicon and zinc. Primarily these alloy modifications result in enhanced corrosion and heat resistance, machinability and tensile strength.
There has been much research and development carried out into the composition of alloys, techniques of working aluminium and heat treatment processes.
By optimising all these factors metallurgists have created an extensive range of material specifications that are best suited for specific applications.
Alloys are classified into two groups:
work hardening and heat-treatable.
Work hardening alloys:
Initial strength is achieved by the addition of particular alloys either singly or in various combinations.
Further strength is developed by the work hardening that results from the mechanical shaping of the metal during manufacture. The required amount of strength and hardness is achieved by controlling the amount of working during the process. These non-heat-treatable alloys are generally less expensive than those requiring heat treatment and are widely used in architectural sheet metal work.
1000 series* Aluminium with a minimum purity of 99% has many general uses. It also has excellent corrosion resistance.
5000 series* These alloys provide significant increases in strength and possess good welding characteristics. Often used for applications requiring a high quality anodised finish.
The strongest of the aluminium alloys are those that increase strength through heat treatment combined with subsequent rapid quenching, normally in water.
By heating for a time at slightly elevated temperatures (artificial ageing) it is possible to stabilise the metal’s properties and consequently to further increase strength. The gain in strength however is usually offset by a loss in ductility.
6000 series* With good medium strength the 6000 series are suitable for a wide range of general applications. Useful welding and working qualities.
* These alloy series relate to the specifications shown in the GA Handbook. For more specific information on particular specifications and standards see below.