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Alloying and Property Examples
For many aluminium products, the pure metal cannot be used. For example for casting applications, the addition of alloying elements is required to improve castability. For wrought apllications, the addition of alloying elements improves mostly the mechanical properties i.e. higher strengths can be obtained, but also other properties are affected. The alloys of the 8 series can have very different mechanical, physical and corrosion properties, and consequently very different behaviour during service, surface treatments, welding, forming etc.
These differences are achieved through one of two ways:
This is illustrated for some properties in the next diagrams as an introduction to the later sections where the alloy influences will be explained in more detail.
Aside from the alloying elements intentionally added to the molten metal for the improvement of various functional (mostly mechanical) or other properties (for example, grain refiners during solidification), there are always trace elements present from the ore, or from the electrolysis process of the aluminium, that can not be easily removed, for example Fe, Pb, Bi,….
Although initially present in the primary aluminium at trace levels, the amounts of these elements may increase in recycled aluminium. These elements may also influence certain properties, for example the corrosion susceptibility, fatigue and fracture behaviour. As a result, special attention needs to be focussed on the behaviour of these trace elements during recycling and their possible influence on the properties of recycled aluminium.