소개
7055 is the strongest of the common aluminum alloys, developed by Alcoa in 1991 for aircraft upper wing skins. It pushes zinc, magnesium, and copper higher than 7075 알루미늄. The real decision is whether you need its peak strength enough to accept limited corrosion resistance and a structure that is not welded for primary load paths.
7055 알루미늄 합금이란?
7055 is a 7xxx-series alloy with zinc, magnesium, and a higher copper content than 7075. Zirconium refines the grain structure. Typical composition: Zn 7.6-8.4%, Mg 1.8-2.3%, Cu 2.0-2.6%, Zr 0.08-0.15%, balance aluminum. Density is about 2.82 g/cm3 – slightly higher than other 7xxx grades because of the copper and zinc load.
Typical Properties by Temper
| 성질 | Ultimate Tensile (MPa) | 항복 강도 (MPa) | 연신율 (%) | Note |
|---|---|---|---|---|
| T7751 | ~600 | ~560 | ~8 | Maximum strength (overaged for SCC control) |
| T7451 | ~590 | ~540 | ~9 | Better corrosion resistance, slightly lower strength |
| T7651 | ~580 | ~530 | ~9 | Balance of strength and corrosion |
Values are representative typical figures; common specs list a minimum ultimate tensile strength around 593 MPa for T7751. Confirm against the mill test certificate.
7055 vs 7075 vs 6061
| 합금 | 항복 강도 (MPa) | Ultimate Tensile (MPa) | 용접성 | Corrosion | Best fit |
|---|---|---|---|---|---|
| 6061-T6 | ~276 | ~310 | 우수 | Good | General structural, welded fabrications |
| 7075-T6 | ~503 | ~572 | Poor | 제한적 | Aerospace, high strength |
| 7055-T7751 | ~560 | ~600 | Poor | 제한적 | Highest-strength aircraft structure |
애플리케이션
- Aircraft upper wing skins and fuselage structure
- High-stress brackets and fittings on commercial airframes (used on 777 and 787 class aircraft)
- Thick plate and forged structural components where strength-to-weight dominates
Welding, Machining, and Corrosion Limits
7055 is not welded for primary load paths: the heat-affected zone loses strength and the alloy carries a stress-corrosion cracking (SCC) risk. Machining is good but produces gummy chips, so use sharp tooling and reliable coolant. Corrosion resistance is limited – bare 7055 is not suitable for marine or chloride-rich service. Aerospace use relies on cladding, T77 overaging, protective coatings, and thick-plate design to manage SCC.
Go/No-Go Limits
Use this quick reference to decide whether 7055 fits your part.
Go – use 7055 when:
- Yield above ~550 MPa is required in a machined or bonded aircraft structure – 7055-T7751 is the standard peak-strength grade.
- Weight savings outweigh corrosion and welding constraints – design uses cladding and coating to manage the environment.
- The part is thick plate or forging joined by fasteners or adhesive, not welding.
No-Go – do not use 7055 when:
- Welding is the primary joining method – strength loss and SCC risk make it unsuitable for welded structures.
- Bare exposure to marine, saltwater, or chloride environments is expected – choose 5083 or a properly protected 6000-series grade.
- Moderate strength with easy fabrication is enough – 6061 or 7005 cost less and process more easily.
결론
7055 is the peak-strength aluminum grade, but its limited corrosion resistance, SCC risk, and no-weld rule for primary structure mean the environment and joining method must be designed around it – and mill stock of non-standard tempers is tight. Linsy Aluminum stocks 7055 plate, bar, and extruded profiles and supplies custom dimensions at low minimum order quantities, with full MTC documentation and in-house processing and surface treatment. If your part sits between strength and weldability on the 7xxx curve, send the drawing for a grade-fit and temper review.
자주 묻는 질문
Is 7055 stronger than 7075?
Yes. 7055-T7751 reaches about 560 MPa yield and 600 MPa ultimate tensile, roughly 10-15% above 7075-T6, which is why it replaced 7075 in upper wing skins on newer airframes.
Can 7055 be welded?
Not for primary load paths. The weld heat-affected zone loses strength and the alloy carries an SCC risk, so 7055 structures are joined by fasteners or adhesive, not welding.
Which temper is best for aerospace?
T7751 gives maximum strength for wing skins; T7451 trades some strength for better corrosion resistance when the part sees a harsher environment.
How well does 7055 resist corrosion?
Limitations are real. Bare 7055 is not suitable for marine or chloride-rich service; aerospace use depends on cladding, T77 overaging, and protective coatings to control stress-corrosion cracking.
What documents come with an order?
Linsy issues an MTC for every order. SGS chemical, mechanical, ultrasonic, and RoHS+REACH test reports are available on request at extra cost.
