Building Design and Construction Handbook - Merritt - Ventech!

BUILDING MATERIALS 4.77
TABLE 4.21 Basic Temper Designations for Wrought Aluminum Alloys*
�F As fabricated. This designation applies to the products of shaping processes in
which no special control over thermal conditions or strain hardening is
employed. For wrought products, there are no mechanical property limits.
�O Annealed. This designation applies to wrought products annealed to obtain the
lowest-strength temper, and to cast products annealed to improve ductility and
dimensional stability.
�H† Strain hardened (wrought products only). This designation applies to products
that have their strength increased by strain hardening, with or without
supplementary thermal treatments to produce some reduction in strengths. The H
is always followed by two or more digits.
�W Solution heat treated. An unstable temper applicable only to alloys that
spontaneously age at room temperature after solution heat treatment. This
designation is specific only when the period of natural aging is indicated: for
example W 1 ⁄2 hr.
�T‡ Thermally treated to produce stable tempers other than F, O, or H. This
designation applies to products that are thermally treated, with or without
supplementary strain hardening, to produce stable tempers. The T is always
followed by one or more digits.
* Recommended by the Aluminum Association.
† A digit after H represents a specific combination of basic operations, such as H1—strain hardened
only. H2—strain hardened and partly annealed, and H3—strain hardened and stabilized. A second digit
indicates the degree of strain hardening, which ranges from 0 for annealing to 9 in the order of increasing
tensile strength.
‡ A digit after T indicates a type of heat treatment, which may include cooling, cold working, and aging.
There are economic advantages in selecting structural aluminum shapes more
efficient for specific purposes than the customary ones. For example, sections such
as hollow tubes, shapes with stiffening lips on outstanding flanges, and stiffened
panels can be formed by extrusion.
Aluminum alloys generally weigh about 170 lb/ft 3 , about one-third that of structural
steel. The modulus of elasticity in tension is about 10,000 ksi, compared with
29,000 ksi for structural steel. Poisson’s ratio may be taken as 0.50. The coefficient
of thermal expansion in the 68 to 212�F range is about 0.000013 in/in � �F, about
double that of structural steel.
Alloy 6061-T6 is often used for structural shapes and plates. ASTM B308 specifies
a minimum tensile strength of 38 ksi, minimum tensile yield strength of 35
ksi, and minimum elongation in 2 in of 10%, but 8% when the thickness is less
than 1 ⁄4 in.
The preceding data indicate that, because of the low modulus of elasticity, aluminum
members have good energy absorption. Where stiffness is important, however,
the effect of the low modulus should be taken into account. Specific data for
an application should be obtained from the producers.
4.54 WELDING AND BRAZING OF ALUMINUM
Weldability and brazing properties of aluminum alloys depend heavily on their
composition and heat treatment. Most of the wrought alloys can be brazed and
welded, but sometimes only by special processes. The strength of some alloys