Classification of Materials.

Aluminium and its alloys are divided into two broad classes - castings and wrought (mechanically worked) products. The latter class is sub-divided into non-heat treatable and heat treatable alloys, and into the various forms produced by mechanical working. Among the series of British Standards covering aluminium material the following are frequently encountered :-

Castings
Casting alloys for general engineering use, specified in BS1490, are numbered in the range 0 to 30, the number being prefixed by LM. The Condition of the casting is indicated by a suffix:

M = As Cast
TF = Solution treated and artificially aged (to give greater strength)

A selection of aluminium alloys commonly encountered is shown below.

Wrought Products
The homogeneity and mechanical properties of cast metal are improved by mechanical working such as rolling, forging or extrusion. The non-heat treatable alloys are strengthened by alloying and/or cold working. Heat treatable alloys can be strengthened by a range of heat treatment processes, and these always develop the highest strength.

A selection of aluminium alloys commonly encountered is shown below.

PREFIX
N = Non-heat treatable
H = Heat treatable
E = Extrusion or Bar
P = Plate
S = Sheet
F = Forging
FC = Free cutting

SUFFIX
M = As Cast
O = Annealed (soft)
H2 = Quarter Hard
H4 = Half Hard
H6 = Three-quarter hard
H8 = Fully hard
TB = Solution treated
TF = Solution treated, artificially aged.

Alloy Designation System for Wrought Aluminium
Wrought aluminium and its alloys, specified in a series of British Standards, are classified by chemical composition in an internationally agreed four-digit system that has replaced the former BS designations. The alloy group, defined according to the major alloying element(s), is indicated by the first digit as shown below:-

1XXX Aluminium of 99.0% purity and higher
2XXX Copper
3XXX Manganese
4XXX Silicon
5XXX Magnesium
6XXX Magnesium + Silicon
7XXX Zinc
8XXX Other element(s)

The remaining three digits are used to indicate different alloys in the group and alloy modifications.