Table 1-2.—Designations for Aluminum Alloy Groups
In the 2xxx through 8xxx groups, the second digit
indicates alloy modifications. If the second digit in the
designation is zero, it indicates the original alloy, while
numbers 1 through 9, assigned consecutively, indicate
alloy modifications. The last two of the four digits have
no special significance, but serve only to identify the
different alloys in the group.
The temper designation follows the alloy
designation and shows the actual condition of the metal.
It is always separated from the alloy designation by a
dash.
The letter F following the alloy designation
indicates the “as fabricated condition, in which no
effort has been made to control the mechanical
properties of the metal,
The letter O indicates dead soft, or annealed,
condition.
The letter W indicates solution heat treated. Solution
heat treatment consists of heating the metal to a high
temperature followed by a rapid quench in cold water,
This in an unstable temper, applicable only to those
alloys that spontaneously age at room temperature,
Alloy 7075 may be ordered in the W condition.
The letter H indicates strain hardened, cold-worked,
hand-drawn, or rolled. Additional digits are added to the
H to indicate the degree of strain hardening. Alloys in
this group cannot be strengthened by heat treatment,
hence the term nonheat-treatable.
The letter T indicates fully heat treated. Digits are
added to the T to indicate certain variations in treatment.
Greater strength is obtainable in the heat-treatable
alloys. They are often used in aircraft in preference to
the nonheat-treatable alloys. Heat-treatable alloys
commonly used in aircraft construction (in order of
increasing strength) are 6061, 6062, 6063, 2017, 2024,
2014,7075, and 7178.
Alloys 6061, 6062, and 6063 are sometimes used
for oxygen and hydraulic lines and in some applications
as extrusions and sheet metal.
Alloy 2017 is used for rivets, stressed-skin
covering, and other structural members.
Alloy 2024 is used for airfoil covering and fittings.
It may be used wherever 2017 is specified, since it is
stronger.
Alloy 2014 is used for extruded shapes and
forgings. This alloy is similar to 2017 and 2024 in that
it contains a high percentage of copper. It is used where
more strength is required than that obtainable from 2017
or 2024.
Alloy 7178 is used where highest strength is
necessary, Alloy 7178 contains a small amount of
chromium as a stabilizing agent, as does alloy 7075.
Nonheat-treatable alloys used in aircraft
construction are 1100, 3003, and 5052. These alloys do
not respond to any heat treatment other than a softening,
annealing effect. They may be hardened only by
cold- working.
Alloy 1100 is used where strength is not an
important factor, but where weight, economy, and
corrosion resistance are desirable. This alloy is used for
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