O
Annealed, for forming or as forging stock; heat-treated to T6 afterwards.
Aerospace · GB high-strength bar
7A04 Aerospace Aluminium Rod and Bar
7A04 (formerly LC4) rod and bar is a high-strength Al-Zn-Mg-Cu product from the Chinese GB system, used for aircraft fittings, frames, shafts and machined parts. In the T6 temper it reaches a minimum tensile strength of about 530 MPa. Metline supplies 7A04 extruded rod and bar in T6 and T6511 to GB/T 3191, and 7075 bar to ASTM and AMS where a Western specification is required, to customers worldwide.
- Alloy
- 7A04 (LC4)
- Tempers
- O, T6, T6511
- Diameter
- About 10 – 250 mm
- Standard
- GB/T 3191 · GB/T 3190
What 7A04 bar is used for
7A04 has been the main high-strength aluminium alloy in Chinese aircraft structures for decades. As extruded rod and bar it is machined into fittings, lugs, frames, shafts and brackets that need strength similar to 7075-T6.
Compared with 7075, 7A04 carries more manganese and a wider zinc range. The manganese adds strength and helps control grain structure in extruded bar, which develops a fine, partly unrecrystallised structure and a "press effect" that raises longitudinal strength. The trade-offs are the same as 7075-T6: low resistance to stress-corrosion cracking when loaded in the transverse direction, and no fusion weldability.
Buyers outside China meet 7A04 mainly on drawings for equipment built to GB or GJB standards. For new designs that must be certified to Western rules, 7075, 7050 or 7175 bar to AMS specifications is usually the better choice, and Metline can quote both.
| Grade | Former Chinese name | Nearest international grade | Comment |
|---|---|---|---|
| 7A04 | LC4 | 7075 (close, not identical) | Higher Mn, wider Zn range; related to the Russian V95 family |
| 7B04 | — | 7475 concept (high purity) | Low Fe and Si for toughness, mainly sheet, plate and wire |
| 7A09 | LC9 | 7075 | Chemistry overlaps 7075 almost completely |
| 7A03 | LC3 | 7050-type rivet use | Rivet wire alloy |
7A04 chemical composition (wt %)
| Element | Minimum | Maximum | Role |
|---|---|---|---|
| Silicon (Si) | — | 0.50 | Impurity |
| Iron (Fe) | — | 0.50 | Impurity |
| Copper (Cu) | 1.4 | 2.0 | Strength and SCC resistance |
| Manganese (Mn) | 0.20 | 0.60 | Higher than 7075; grain control and strength |
| Magnesium (Mg) | 1.8 | 2.8 | Forms MgZn2 with zinc |
| Chromium (Cr) | 0.10 | 0.25 | Grain control |
| Zinc (Zn) | 5.0 | 7.0 | Main strengthening element |
| Titanium (Ti) | — | 0.10 | Grain refiner |
| Others, each / total | — | 0.05 / 0.10 | |
| Aluminium (Al) | Remainder |
Limits as published in GB/T 3190. Check the current revision named on your order; minor limits for impurities can differ between editions.
Mechanical properties of 7A04 bar
GB/T 3191 specifies room-temperature minimum properties for extruded bar by temper and diameter band. For T6 bar the minimums are of the order shown below; larger diameters may have different values, so check the band in the current edition.
| Condition | Tensile strength | Yield strength | Elongation |
|---|---|---|---|
| 7A04-T6 / T6511, GB minimum (typical bands) | ≥ 530 MPa | ≥ 400 MPa | ≥ 5 % |
| 7A04-T6, approximate typical | About 560 – 600 MPa | About 480 – 530 MPa | About 8 – 10 % |
| 7075-T6511 extruded bar, typical | 572 MPa | 503 MPa | 11 % |
Physical properties
- Density
- About 2.80 – 2.85 g/cm³
- Modulus of elasticity
- About 70 – 72 GPa
- Electrical conductivity
- About 30 – 33 % IACS in T6
- Melting range
- About 475 – 640 °C
7A04 bar tempers
T6
Solution treated and artificially aged for peak strength. Standard for machined parts.
T6511
T6 with stretch stress relief and minor straightening; preferred where heavy machining could cause distortion.
Not applicable
Designations such as T3 or T8 apply to 2xxx alloys, not 7A04. Clarify any order that lists them.
7A04 rod and bar sizes
Supply range
- Round bar
- About 10 – 250 mm diameter
- Square, flat and hexagon bar
- Per drawing
- Length
- Typically 2 – 6 m, or cut to length
- Surface
- As extruded; peeled or turned on request
| Diameter (mm) | kg per metre (2.85 g/cm³) | kg per 3 m bar |
|---|---|---|
| 10 | 0.22 | 0.7 |
| 16 | 0.57 | 1.7 |
| 20 | 0.90 | 2.7 |
| 25 | 1.40 | 4.2 |
| 30 | 2.01 | 6.0 |
| 40 | 3.58 | 10.7 |
| 50 | 5.60 | 16.8 |
| 60 | 8.06 | 24.2 |
| 80 | 14.33 | 43.0 |
| 100 | 22.38 | 67.2 |
| 120 | 32.23 | 96.7 |
| 150 | 50.36 | 151.1 |
| 200 | 89.54 | 268.6 |
| 250 | 139.90 | 419.7 |
Machining and protection
Machining
Machines like 7075-T6: short chips, good finish, accurate threads.
Joining
Bolted or riveted; not fusion-welded.
Stress corrosion
Avoid sustained tensile stress across the grain; shot peen and protect critical parts.
Finishing
Sulphuric or chromic acid anodise; conversion coat and prime.
Applications
- Airframe: fittings, lugs, frames and beams machined from bar
- Landing gear and controls: brackets, links and shafts
- Defence: high-strength components made to GB or GJB drawings
- Industrial: high-strength tooling and fixtures where 7075-class bar is needed
How to order 7A04 bar
- SpecifyAlloy and temper, diameter or section, length, quantity and the governing specification with its revision letter (GB/T 3191 with GB/T 3190 chemistry, or ASTM/AMS for a 7075 alternative). Add any customer or prime-contractor material specification that sits on top of the AMS.
- ConfirmWe confirm the specification can be met, the tolerance class, any extra tests (ultrasonic class, conductivity, fracture toughness, grain flow) and the delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions, surface condition and marking; tests named on the order are carried out or arranged with an independent laboratory.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 giving chemistry, mechanical results and heat-treatment lot, traceable to the cast number.
- Pack and shipExport packing in sealed, moisture-protected wooden cases or on pallets, shipped by sea or air to your port or door.
References and standards
- GB/T 3190 – Wrought aluminium and aluminium alloys: chemical composition
- GB/T 3191 – Aluminium and aluminium alloy extruded bars
- GB/T 16475 – Temper designation system for wrought aluminium and aluminium alloys
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
7A04 aerospace aluminium (aluminum) bar: FAQ
What is the minimum strength of 7A04-T6 bar?
For common diameter bands, GB/T 3191 requires about 530 MPa tensile and 400 MPa yield strength with at least 5 % elongation. Check the band for your size in the current edition.
Is 7A04 equivalent to 7075?
It is close in strength and use, but not identical in chemistry. 7A04 has more manganese and a wider zinc range.
Does 7A04 have a UNS number?
No. 7A04 is a GB designation and is not registered with a UNS number. Certificates should cite GB/T 3190 and the product standard.
Can 7A04 bar be welded?
No. It is joined mechanically.
Can you supply 7075 instead with AMS certification?
Yes. We can supply 7075-T6 or T7351 bar to AMS 4122, AMS 4124 or ASTM B211/B221 where the drawing allows.
Need 7A04 rod or bar?
Send diameter, temper, length and standard. We will confirm availability and a delivered price.
