T6
Peak strength for sheet and thinner plate used in controlled environments.
High-strength 7xxx sheet and plate
7A09 Aluminium Sheet & Plate
7A09, formerly LC9, is the GB-standard alloy that corresponds most closely to 7075: an Al-Zn-Mg-Cu alloy with high strength, good machinability and useful toughness. Metline supplies 7A09 sheet and plate in T6, T651 and over-aged tempers to GB/T 3880, certified and export-packed for customers worldwide.
- Alloy
- 7A09 (Al-Zn-Mg-Cu)
- Tempers
- O, T6, T651, T73
- Thickness
- About 1 – 200 mm
- Closest equivalent
- 7075
What is 7A09 aluminium?
7A09 is a heat-treatable 7xxx alloy whose composition limits overlap almost entirely with 7075. It was introduced to give Chinese aerospace a grade with better toughness and stress-corrosion behaviour than the older 7A04.
Its strength comes from fine MgZn2 precipitates formed during ageing. In the peak-aged T6 condition it offers tensile strength above 500 MPa; in over-aged T73 and T74 conditions it gives up some strength for much better resistance to stress-corrosion cracking and exfoliation. The alloy keeps its strength well at low temperatures but should not be used for long periods above about 120 – 150 °C, where over-ageing reduces strength.
In practice 7A09 is specified on drawings from Chinese standards for aircraft frames, beams and fittings, and as a general high-strength sheet and plate for tooling and machined parts. On international projects, 7075 in the matching temper is the usual substitute.
7A09 chemical composition (wt %)
| Element | 7A09 min | 7A09 max | 7075 range |
|---|---|---|---|
| Silicon (Si) | — | 0.50 | ≤ 0.40 |
| Iron (Fe) | — | 0.50 | ≤ 0.50 |
| Copper (Cu) | 1.2 | 2.0 | 1.2 – 2.0 |
| Manganese (Mn) | — | 0.15 | ≤ 0.30 |
| Magnesium (Mg) | 2.0 | 3.0 | 2.1 – 2.9 |
| Chromium (Cr) | 0.16 | 0.30 | 0.18 – 0.28 |
| Zinc (Zn) | 5.1 | 6.1 | 5.1 – 6.1 |
| Titanium (Ti) | — | 0.10 | ≤ 0.20 |
| Others, each / total | — | 0.05 / 0.10 | 0.05 / 0.15 |
| Aluminium (Al) | Remainder | Remainder |
7A09 limits per GB/T 3190; 7075 limits per the Aluminum Association registration.
Mechanical and physical properties
Minimum properties for 7A09 sheet and plate are set in GB/T 3880.2 by temper and thickness. The figures below are representative of T6 sheet; over-aged tempers sit roughly 10 – 15 % lower in strength.
| Temper | Tensile strength | Yield strength (0.2 %) | Elongation |
|---|---|---|---|
| O (annealed) | ≤ about 245 MPa | — | ≥ about 10 % |
| T6 / T651, representative minimum | ≈ 490 – 530 MPa | ≈ 400 – 440 MPa | ≥ 6 % |
| T73 (over-aged) | Roughly 10 – 15 % lower than T6 | Lower than T6 | Similar to T6 |
Physical properties (approximate)
- Density
- About 2.80 – 2.85 g/cm³
- Modulus of elasticity
- About 70 – 72 GPa
- Thermal conductivity
- About 130 – 160 W/m·K depending on temper
Which temper to order
T651
T6 plus stretching to relieve quench stress; the standard choice for plate that will be machined.
T73 / T74
Over-aged for stress-corrosion and exfoliation resistance in thick parts and outdoor service.
O
Annealed for forming; heat-treated to T6 afterwards.
7A09 sheet and plate sizes
Supply range
- Thickness
- About 1 – 200 mm (0.04 – 7.9 in)
- Common sizes
- 1500 × 3000 mm and 2000 × 4000 mm
- Processing
- Saw cutting and cut-to-size blanks
| Thickness (mm) | kg per m² (approx.) | 1500 × 3000 mm (kg) |
|---|---|---|
| 1 | 2.8 | 13 |
| 2 | 5.6 | 25 |
| 3 | 8.5 | 38 |
| 5 | 14.1 | 63 |
| 10 | 28.2 | 127 |
| 20 | 56.4 | 254 |
| 40 | 112.8 | 508 |
| 60 | 169.2 | 761 |
| 100 | 282.0 | 1269 |
Fabrication notes
- Machining: very good in T6 and T651, with short chips and fine surface finish.
- Welding: poor by fusion methods; join by riveting, bolting or bonding.
- Forming: in the annealed and freshly quenched states it is somewhat more ductile than 7A04 and slightly less ductile than 2A12.
- Corrosion: T6 can suffer stress-corrosion cracking; specify T73/T74 or protect by anodising and paint.
Where 7A09 is used
- Aircraft frames, beams, ribs and fittings machined from plate
- Highly loaded structural sheet parts in defence equipment
- Moulds, jigs and fixtures that need high strength and hardness
- Industrial parts where low weight and high strength are both required
How to order 7A09 sheet
- SpecifyTemper, thickness, width, length, quantity and governing standard.
- QuoteWe confirm availability, certificates and delivery terms (EXW, FOB, CIF or DAP).
- ShipPacked on wooden pallets or in cases with steel strapping, with the EN 10204 3.1 mill certificate.
References and standards
- GB/T 3190 – Wrought aluminium and aluminium alloys: chemical composition
- GB/T 3880 – Wrought aluminium and aluminium alloy plates, sheets and strips for general engineering
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
- ASM Handbook Vol. 2 – Properties of Wrought Aluminum Alloys
7A09 aluminium (aluminum) sheet: FAQs
Is 7A09 the same as 7075?
Very nearly. Zinc, copper and magnesium ranges match closely, so 7075 in the same temper is the usual international substitute. Check minor element limits if your specification is strict.
Can 7A09 be welded?
Not by fusion welding in structural applications; it cracks and loses strength. Use mechanical fastening or bonding.
Which temper resists stress corrosion best?
The over-aged T73 temper, followed by T74. T6 and T651 are stronger but more susceptible.
What does LC9 mean?
LC9 is the old Chinese designation; GB/T 3190 now calls the alloy 7A09.
How much does a 7A09 plate weigh?
About 2.82 kg per m² per millimetre. A 1500 × 3000 × 10 mm plate weighs roughly 127 kg.
Need 7A09 sheet or plate?
Send the temper, size, quantity and destination and we will quote with availability and documents.
