Sep 20 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Annealing
Cold Working
Welding
Forming
Machinability
Heat Treatment
Hardening
Applications
Introduction
Aluminium / Aluminum alloys are good low-temperature alloys that
gain strength when exposed to subzero temperatures. These alloys lose
their strength when exposed to high temperatures. Aluminium / Aluminum
alloys are sensitive to high temperatures ranging between 200 and 250°C
(392 and 482°F). They have strong corrosion resistance characteristics
and high electrical conductivity.
The following datasheet provides an overview of Aluminium / Aluminum
7178 alloy.
Chemical Composition
The chemical composition of Aluminium / Aluminum 7178 alloy is
outlined in the following table.
| Element |
Content
(%) |
| Aluminium / Aluminum, Al |
88.1 |
| Zinc, Zn |
6.8 |
| Magnesium, Mg |
2.7 |
| Copper, Cu |
2.0 |
| Chromium, Cr |
0.26 |
Physical Properties
The following table shows the physical properties of Aluminium /
Aluminum 7178 alloy.
| Properties |
Metric |
Imperial |
| Density |
2.82 g/cm3 |
0.1018 lb/in3 |
| Melting point |
482°C |
900°F |
Mechanical Properties
The mechanical properties of Aluminium / Aluminum 7178 alloy are
displayed in the following table.
| Properties |
Metric |
Imperial |
| Elastic modulus |
70-80 GPa |
10152-11603 ksi |
| Poisson's ratio |
0.33 |
0.33 |
Thermal Properties
The thermal properties of Aluminium / Aluminum 7178 alloy are given
in the following table.
| Properties |
Conditions |
| T
(ºC) |
Treatment |
| Thermal expansion |
23.4 (10-6/ºC) |
20-100 |
- |
Other Designations
Equivalent materials to Aluminium / Aluminum 7178 alloy are:
- ASTM B209
- ASTM B221
- ASTM B241
- ASTM B316
- QQ A-200/13
- QQ A-200/14
- QQ A-250/14
- QQ A-250/21
- QQ A-250/28
- QQ A-430
- SAE J454
Fabrication and Heat Treatment
Annealing
Aluminium / Aluminum 7178 alloy is annealed for 3 hours at 413°C
(775°F), cooled to 204°C (400°F) or even less, heated to 232°C (450°F),
held for 4 hours and finally cooled in air. This process produces O
temper and removes the solution heat treatment condition.
Cold Working
Aluminium / Aluminum 7178 alloy is difficult to be cold worked.
Welding
Aluminium / Aluminum 7178 alloy can be welded by resistance welding
methods.
Forming
Aluminium / Aluminum 7178 alloy is difficult to form, or work, in
any of the T tempers.
Machinability
Aluminium / Aluminum 7178 alloy has good machinability, especially
in the annealed state. Usage of oil lubricants is recommended for this
process.
Heat Treatment
Aluminium / Aluminum 7178 alloy can be heat treated at 468°C (875°F)
and then water quenched.
Hardening
The Aluminium / Aluminum 7178 alloy has precipitation hardening
characteristic.
Applications
Aluminium / Aluminum 7178 alloy is used in structures such as
aircrafts.