ALUMINUM - Materials for Civil and Construction Engineers - page 145

T ABLE 4.2 Designation System for Aluminum Alloys (Aluminum Association, 1993)

Wrought Aluminum Alloys Cast Aluminum Alloys

Alloy Description or Major Alloy Description or Major

Series Alloying Elements Series Alloying Elements

1xxx 99.00% Minimum 1xx.x 99.00% Minimum Aluminum

Aluminum

2xxx Copper 2xx.x Copper

3xxx Manganese 3xx.x Silicon plus copper and/or

magnesium

4xxx Silicon 4xx.x Silicon

5xxx Magnesium 5xx.x Magnesium

6xxx Magnesium and silicon 6xx.x Unused series

7xxx Zinc 7xx.x Zinc

8xxx Other element 8xx.x Tin

9xxx Unused Series 9xx.x Other element

last two digits of the code, expressed as a decimal fraction. For example, a
1060 contains a minimum aluminum content of 99.60%.
Cast alloys are assigned a three-digit number followed by one digit after
the decimal point, as shown in Table 4.2. The first digit represents the alloy
series. Note that series 3, 6, 8, and 9 have different meanings for cast versus
wrought alloys. The second and third digits are arbitrarily assigned to iden-
tify specific alloys. The digit after the decimal indicates whether the alloy
composition is for the final casting (xxx.0) or for ingot (xxx.1 and xxx.2).

■ 4.2.2 Temper Treatments

The mechanical properties of aluminum are greatly altered by both heat
treatment and strain hardening. Therefore, specification of an aluminum
material must include the manner in which the product was tempered. The
processes described in Table 4.3 define the types of tempering aluminum
products undergo.
Aluminum alloys used for structural applications are classified as being
either heat treatable or not. Non-heat-treatable or “common” alloys contain
elements that remain substantially in solid solution or that form insoluble
constituents. Thus, heat treatment does not influence their mechanical prop-
erties. The properties of these alloys are dependent on the amount of cold
working introduced after annealing. Heat-treatable or “strong” alloys contain
elements, groups of elements, or constituents that have a considerable solid
solubility at elevated temperatures and limited solubility at lower tempera-
tures. The strength of these alloys is increased primarily by heat treatment.