Aluminum 7A04
GB 7A04
7A04 (LC4) is a high-strength Al-Zn-Mg-Cu alloy of the GB/T 7000-series family, strengthened by MgZn2-type precipitation and dimensionally close to 7075/V95 in role and property level.
Reference datasheet — 7A04 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the T6 condition
7A04 tempers and conditions
7A04 is supplied in 9 conditions, soft to hard. T6 is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest state for deep forming, bending or straightening before re-heat-treatment. | 110 | 235 | 16 | 60 HB | 45 % IACS |
As fabricated | Mill state of forging stock and hot-rolled slabs, bought for subsequent forging plus full heat treatment. | 200 | 320 | 12 | 90 HB | 40 % IACS |
Solution heat treated and naturally aged | Intermediate strength with better formability than T6; used when parts are formed after quenching and later artificially aged. | 300 | 470 | 13 | 120 HB | 32 % IACS |
T73, stress relieved by stretching | Thick-plate over-aged temper for machined aerospace fittings needing both low residual stress and SCC resistance. | 420 | 490 | 9 | 132 HB | 40 % IACS |
Solution heat treated and overaged for stress-corrosion resistance | Pick when stress-corrosion cracking or exfoliation risk (thick sections, sustained tension, marine/humid service) outweighs the ~8 % strength loss. | 430 | 500 | 10 | 135 HB | 40 % IACS |
Overaged for exfoliation-corrosion resistance | Compromise temper: most of T6 strength with much better exfoliation resistance in thin plate and extrusions. | 450 | 520 | 9 | 140 HB | 38 % IACS |
T6, heat treated by the user | Used when parts are formed in the O/F state and then given a full T6 treatment by the fabricator. | 460 | 530 | 8 | 145 HB | 33 % IACS |
T6, stress relieved by stretching | Thick plate temper of choice when large amounts of metal are machined away and distortion must be minimized. | 470 | 540 | 8 | 148 HB | 33 % IACS |
T6Default Solution heat treated and artificially aged | Standard peak-strength condition for machined structural parts, extrusions and forgings; default stock temper. | 475 | 545 | 8 | 150 HB | 33 % IACS |
What is 7A04?
7A04 (LC4) is a high-strength Al-Zn-Mg-Cu alloy of the GB/T 7000-series family, strengthened by MgZn2-type precipitation and dimensionally close to 7075/V95 in role and property level. In its default aged condition it gives 475 MPa yield, 545 MPa tensile, 8 % elongation and about 150 HB, and is supplied as thick plate, extrusions, die forgings and bar for machined structural parts. It is not suitable for fusion welding, service is limited to about 120 °C, and corrosion/SCC resistance is modest (score 35), so over-aged T73/T7351 tempers are used for thick sections. 7075 is the direct alternative where an international designation is required. 7A04 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 477°C (891 °F). 7A04 has a yield strength of 475 MPa (68.9 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 94% of aluminum grades. Elongation at break is 8% and the elastic modulus is 71 GPa (10.3 Msi).
What is 7A04 used for?
- aircraft structural forgings
- high-strength machined parts
- landing gear components
Advantages
- High strength — 475 MPa (68.9 ksi), better than 94% of aluminum grades
- Easy to machine — 72/100, better than 80% of aluminum grades
Limitations
- High embodied carbon — 14 kg CO₂/kg, worse than 95% of aluminum grades
- Difficult to weld — 20/100, worse than 89% of aluminum grades
- Needs corrosion protection — 35/100, worse than 85% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
7A04 properties
Typical room-temperature values for 7A04-T6; bars are the position among aluminum grades.
Physical3
7A04 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 477°C (891 °F).
Mechanical14
7A04 has a yield strength of 475 MPa (68.9 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 94% of aluminum grades. Elongation at break is 8% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
7A04 is rated for continuous service to 120°C (248 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7A04 conducts electricity at 33 % IACS, worse than 57% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 85% of aluminum grades.
Sustainability4
Producing a kilogram of 7A04 takes about 200 MJ of energy and emits 14 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 10%.
Manufacturability6
7A04's machinability is very good (72/100, better than 80% of aluminum grades); weldability poor (20/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 7A04 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 7A04
Is 7A04 easy to machine?
Machines very freely in T6/T73 with sharp polished-flute carbide tools, high speeds and flood coolant/MQL; watch residual-stress distortion on thick plate — use T651/T7351 and symmetric roughing passes.
Can 7A04 be welded?
Not suitable for fusion welding (hot cracking, severe HAZ strength loss); join by riveting, bolting or adhesive, or use friction-stir/resistance spot welding with post-weld property allowance.
Can 7A04 be formed, bent or molded?
Form in O or T4 (or hot-form 200–350 °C) with generous bend radii; T6 material is prone to cracking, and forgings need controlled 400–460 °C forging plus solution quench.
7A04 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Zn | 5 – 7 | 6 |
| Mg | 1.8 – 2.8 | 2.3 |
| Cu | 1.4 – 2 | 1.7 |
| Mn | 0.2 – 0.6 | 0.4 |
| Cr | 0.1 – 0.25 | 0.17 |
| Feimpurity limit | ≤ 0.5 | |
| Siimpurity limit | ≤ 0.5 | |
| Tigrain refiner / impurity | ≤ 0.1 | |
| Niimpurity limit | ≤ 0.1 | |
| others (each)total 0.10 max | ≤ 0.05 | |
| Al | balance |
What surface finishes work on 7A04?
Anodize (sulfuric, chromic or hard Type III), chromate/trivalent conversion coat plus epoxy primer for aerospace; avoid strong alkaline cleaners and give shot-peening on fatigue-critical surfaces.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 7A04 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- GB (China)
- LC4
- Other
- 7075
How much does 7A04 cost?
7A04 is a premium-cost aluminum ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
7A04 — frequently asked
What is 7A04 used for?
7A04 is typically used for aircraft structural forgings, high-strength machined parts and landing gear components. In short: 7075-class strength level; high-strength forging grade; not fusion weldable.
What is the yield strength of 7A04?
7A04 has a typical yield strength of 475 MPa (68.9 ksi) and a tensile strength of 545 MPa (79 ksi) — stronger than 94% of aluminum grades. Strength varies by condition: see the 9 listed tempers.
Is 7A04 easy to machine?
Yes — machinability is rated very good (72/100, better than 80% of aluminum grades). Machines very freely in T6/T73 with sharp polished-flute carbide tools, high speeds and flood coolant/MQL; watch residual-stress distortion on thick plate — use T651/T7351 and symmetric roughing passes.
Can 7A04 be welded?
Not readily — weldability is rated poor (20/100). Not suitable for fusion welding (hot cracking, severe HAZ strength loss); join by riveting, bolting or adhesive, or use friction-stir/resistance spot welding with post-weld property allowance.
What surface finishes work on 7A04?
Anodize (sulfuric, chromic or hard Type III), chromate/trivalent conversion coat plus epoxy primer for aerospace; avoid strong alkaline cleaners and give shot-peening on fatigue-critical surfaces.
Can 7A04 be formed, bent or molded?
Form in O or T4 (or hot-form 200–350 °C) with generous bend radii; T6 material is prone to cracking, and forgings need controlled 400–460 °C forging plus solution quench.
What is the maximum service temperature of 7A04?
7A04 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7A04-T6 and 7A04-O?
T6 is the default condition — standard peak-strength condition for machined structural parts, extrusions and forgings; default stock temper. O: softest state for deep forming, bending or straightening before re-heat-treatment. Yield strength is 475 MPa in T6 versus 110 MPa in O.
How much does 7A04 cost?
7A04 is a premium-cost aluminum ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys (7075) — ASM International (1990)
- MMPDS-17 Metallic Materials Properties Development and Standardization — Battelle/FAA (2022)
- Aluminum Association Teal Sheets — registered alloy/temper data — The Aluminum Association (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.