Table 2-2.--Designation for Aluminum Alloy Groups
Aluminum--99.0 percent minimum and greater .............................................1xxx
Aluminum alloys, grouped by major alloying element:
Copper ......................................................................................................2xxx
Manganese ..............................................................................................3xxx
Silicon ........................................................................................................4xxx
Magnesium ................................................................................................5xxx
Magnesium and silicon ..............................................................................6xxx
Zinc ............................................................................................................7xxx
Other elements ...........................................................................................8xxx
The letter W indicates solution heat treated.
copper is the major alloying element; 3xxx indicates an
Solution heat treatment consists of heating the metal to
aluminum alloy with manganese as the major alloying
a high temperature followed by a rapid quench in cold
element; etc. Although most aluminum alloys contain
water. This in an unstable temper, applicable only to
several alloying elements, only one group (6xxx)
those alloys that spontaneously age at room
designates more than one alloying element.
temperature. Alloy 7075 may be ordered in the W
In the 1xxx group, the second digit in the
condition.
designation indicates modifications in impurity limits.
The letter H indicates strain hardened,
If the second digit is zero, it indicates that there is no
cold-worked, hand-drawn, or rolled. Additional digits
special control on individual impurities. The last two of
are added to the H to indicate the degree of strain
the four digits indicate the minimum aluminum
hardening. Alloys in this group cannot be strengthened
percentage. Thus, alloy 1030 indicates 99.30 percent
by heat treatment, hence the term nonheat-treatable.
aluminum without special control on impurities. Alloys
1130, 1230, 1330, etc., indicate the same aluminum
The letter T indicates fully heat treated. Digits are
purity with special control on one or more impurities.
added to the T to indicate certain variations in
Likewise, 1075, 1175, 1275, etc., indicate 99.75
treatment.
percent aluminum.
Greater strength is obtainable in the heat-treatable
In the 2xxx through 8xxx groups, the second digit
alloys. They are often used in aircraft in preference to
indicates alloy modifications. If the second digit in the
the nonheat-treatable alloys. Heat-treatable alloys
designation is zero, it indicates the original alloy, while
commonly used in aircraft construction (in order of
numbers 1 through 9, assigned consecutively, indicate
increasing strength) are 6061, 6062, 6063, 2017, 2024,
alloy modifications. The last two of the four digits have
2014, 7075, and 7178.
no special significance, but serve only to identify the
Alloys 6061, 6062, and 6063 are sometimes used
different alloys in the group.
for oxygen and hydraulic lines and in some applications
The temper designation follows the alloy
as extrusions and sheet metal.
designation and shows the actual condition of the
Alloy 2017 is used for rivets, stressed-skin
metal. It is always separated from the alloy designation
covering, and other structural members.
by a dash.
Alloy 2024 is used for airfoil covering and fittings.
The letter F following the alloy designation
It may be used wherever 2017 is specified, since it is
indicates the "as fabricated" condition, in which no
stronger.
effort has been made to control the mechanical
properties of the metal.
Alloy 2014 is used for extruded shapes and
forgings. This alloy is similar to 2017 and 2024 in that it
The letter O indicates dead soft, or annealed,
contains a high percentage of copper. It is used where
condition.
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