3-2. Aluminum alloys are produced and used in many shapes
and forms. The common forms are casting, sheet, plate, bar,
rod (round, hex, etc.), angles (extruded and rolled or drawn),
channels and forgings. The inherent advantages of this
atmosphere and many varieties of chemicals, thermal and
electrical conductivity, reflectivity for radiant energy of all
wave lengths and ease of fabrication.
3-3. The above factors plus the fact that some alloys of this
material can be formed in a soft condition and heat treated to
a temper comparable to structural steel make it very
adaptable for fabricating various aircraft and missile parts.
3-4. COMMERCIAL AND MILITARY DESIGNATIONS . The
present system utilized to identify aluminum alloys is the 4
digit designation system. The major alloy element for each
type is indicated by the first digit (see Table 3-1) i.e., 1XXX
indicates aluminum of 99.00% minimum, 2XXX indicates an
aluminum alloy in which copper is the main alloying element,
etc. Although most aluminum alloys contain several alloying
elements only one group the 6XXX designate more than one
alloying element. See Table 3-1 for complete listing.
TABLE 3-1 DESIGNATIONS FOR ALLOY GROUPS
The second digit of the destination indicates modification in
impurity limits. If the second digit is 0 it indicates that there is
no special control on the impurities, while numbers 1 9 which
are assigned consecutively as needed indicates special
control of one individual impurity. Thus 1040 indicates
99.40% minimum aluminum without special control on
individual impurities and 1140, 1240 etc. indicate same purity
with special control on one or more impurities.
3-5. The last two of the four digits in alloy groups 2XXX
through 8XXX have no special significance except that they
serve to designate the alloy by its former number, i.e., 243,
525, 758, etc.
3-6. Experimental alloys are, also, designated by this system
except that the 4 digit number is prefixed by an X.
TABLE 3-2 ALUMINUM ALLOY DESIGNATION AND
CONVERSIONS TO 4 DIGIT SYSTEM