Wrought Alloys | 7xxx Al-Zn Alloys
- Heat treatable
- Very high strength;special high toughness versions
- Aerospace,automotive applications
- Representative alloys: 7005,7075, 7475, 7150
- Typical ultimate tensile strength range:32-88 ksi
There are several alloys in the series that are produced especially for their high toughness, notably 7150 and 7475, both with controlled impurity level to maximise the combination of strength and fracture toughness.
The widest application of the 7xxx alloys has historically been in the aircraft industry, where fracture-critical design concepts have provided the impetus for the high-toughness alloy development. These alloys are not considered wieldable by routine commercial processes, and are regularly used in riveted construction.
The atmospheric corrosion resistance of the 7xxx alloys is not as high as that of the 5xxx and 6xxx alloys, so in such service they are usually coated or, for sheet and plate, used in an alclad version. The use of special tempers such as the T73- type are required in place of T6-type tempers whenever stress corrosion cracking may be a problem.
Applications of 7xxx alloys include
- Aircraft structures are of 7xxx alloy sheet or extrusion construction; alloys like 7075-T73 or high-toughness alloys like 7050 or 7475 are among the principal choices.
- Lightweight 7029 or 7129 bumper structures help improve our gas mileage.