Wrought Aluminium Alloys

Sheets and extrusion ingots are cast through semi-continuous direct chill method. The sheet ingots are scalped wherein about 12 mm of ingot surface is removed. The scappled ingots are preheated to homogenise the structure by heating to a high temperature and soaking there for 10-24 hours. The preheating is done at a temperature below the lowest melting point of the constituents. The ingots are then hot rolled to about 75 mm thickness in 4 high reversed rolling stand. Thereafter the rolled sheet is further reheated to the same temperature and further hot rolled to 18 mm to 25 mm thickness. Further thickness reduction may be achieved through cold rolling. The products obtained this way are termed wrought alloys and normally are inform of sheet, plate, rod, wire and extruded sections.

The wrought alloys are identified by a four digit code out of which the first digit signifies the aluminium purity (if pure aluminium) or the major alloying element. The second digit indicates the modification of alloy. The third and fourth digits indicate the minimum amount of aluminium in the alloy. The first digit indicates following :

a.    Aluminium is pure no alloying element.
b.    Alloying element copper but magnesium is also added.
c.    Alloying element manganese.
d.    Alloying element silicon.
e.    Alloying element magnesium.
f.    Main alloying elements are magnesium and silicon.
g.    Main alloying elements are zinc, magnesium and copper.