Direct answer: 7075-T6 aluminium is not stronger than all steels. It outperforms ordinary mild structural steel such as ASTM A36, and it wins clearly on strength per unit of mass, but quenched and tempered alloy steels such as AISI 4140 still reach roughly twice the tensile strength of 7075-T6 in absolute terms. The alloy's real advantage is high tensile strength combined with a density of about 2.81 g/cm3, against 7.85 g/cm3 for steel.
Export Control Compliance Notice - High-Strength Aluminum Alloys
Certain high-strength aluminum alloy products supplied by GNEE are subject to the export control regulations of the People's Republic of China for dual-use items and technologies. Under these regulations, the export, re-export, or transfer of such items generally requires an export license issued by the competent Chinese authorities. Unlicensed export of the controlled item categories is prohibited.
The alloys listed in the table below represent product categories commonly affected by these controls. Whether a specific inquiry or order is controlled depends on the alloy grade, temper, product form, dimensions, quantity, and intended end-use.
|
Alloy Grade |
Common Temper(s) |
Tensile Strength (MPa) - Reference |
|
7075 |
T6 / T651 |
540 – 570 |
|
7075 |
T73 / T7351 |
485 – 500 |
|
7075 |
T76 / T7651 |
500 – 515 |
|
7050 |
T7451 / T6 |
475 – 620 |
|
2024 |
T351 / T4 |
425 – 470 |
|
7A04 |
T6 |
≥ 530 |
|
2014 |
T6 |
≈ 460 – 500 |
|
2017 |
T4 |
≈ 390 – 480 (some specifications may reach higher) |
|
2195 |
- |
≈ 572 |
|
7068 |
- |
≈ 623 |
|
7055 |
- |
≈ 654 |
|
7150 |
- |
≈ 643 |
GNEE does not export to parties or destinations prohibited under applicable export control and international sanctions laws.
Chemical Composition of Alloy 7075
Alloy 7075 is a zinc-bearing 7xxx series alloy with magnesium and copper additions. Composition limits for rolled sheet and plate are specified in ASTM B209, and the same limits apply to extruded product under ASTM B221.
| Element | Content, % |
|---|---|
| Silicon | 0.40 max |
| Iron | 0.50 max |
| Copper | 1.2 - 2.0 |
| Manganese | 0.30 max |
| Magnesium | 2.1 - 2.9 |
| Chromium | 0.18 - 0.28 |
| Zinc | 5.1 - 6.1 |
| Titanium | 0.20 max |
| Aluminium | Remainder |
What the T6 Temper Delivers
T6 means solution heat treated and then artificially aged, with no cold working applied after ageing. The alloy is solution treated at elevated temperature, quenched, and aged so that fine precipitates carrying zinc, magnesium and copper form and lock the strength in place. Because the temper is defined by the thermal cycle rather than by cold reduction, mechanical property minima for sheet and plate are written directly into ASTM B209, and tension testing is carried out to ASTM E8/E8M.
7075-T6 Against Steel: Property Comparison
| Property | 7075-T6 | ASTM A36 mild steel | AISI 4140 quenched and tempered |
|---|---|---|---|
| Density, g/cm3 | 2.81 | 7.85 | 7.85 |
| Tensile strength, MPa | about 540 | 400 - 550 | about 1035 |
| 0.2 % yield strength, MPa | about 470 | 250 minimum | about 900 |
| Elongation, % | 5 - 11 | 20 - 23 | 10 - 12 |
| Hardness | about 150 HB | about 120 HB | about 300 HB |
Read the table by column, not by headline. In absolute strength, hardness and wear resistance, alloy steel wins. In strength divided by density, 7075-T6 wins by a wide margin: roughly 190 kN.m/kg against about 60 kN.m/kg for mild steel and about 130 kN.m/kg for quenched and tempered 4140.
Physical Limits That Decide the Application
Three limits dominate design. First, stiffness: the elastic modulus of aluminium is about 70 GPa against 210 GPa for steel, so deflection-controlled parts must be thicker even when strength is adequate. Second, welded joints in 7xxx alloys lose a large part of their strength in the heat affected zone, so structural assemblies are normally mechanically fastened or adhesively bonded rather than welded. Third, corrosion: the high copper and zinc content makes 7075 less resistant than 5052 or 6061 in marine and chemical service, and short-transverse stress corrosion resistance is limited, so continuous tensile stress through the plate thickness is avoided in design practice.
Applications Where 7075-T6 Is the Default Choice
Airframe structure: wing spars, ribs, stringers and machined fittings where mass saving is the primary driver.
Motorsport and high-performance automotive parts: suspension arms, drive shafts and wheel centres after a suitable protective finish.
Sporting equipment: bicycle frames, climbing hardware and archery risers that need stiffness at low mass.
Tooling and mould plates where high strength and good thermal conductivity are both required.
Where maximum hardness, abrasion resistance or low cost per kilogram dominate, carbon and alloy steels remain the correct choice.
Frequently Asked Questions
Q: Is 7075-T6 aluminium stronger than steel?
A: Against mild structural steel such as ASTM A36 it is stronger weight-for-weight and comparable in absolute terms. Against quenched and tempered alloy steels it is not, because those grades reach about 1035 MPa tensile against roughly 540 MPa for 7075-T6.
Q: Is 7075-T6 stronger than 6061-T6?
A: Yes, by a wide margin. 7075-T6 is typically quoted near 540 MPa tensile and 470 MPa yield, while 6061-T6 is typically 310 MPa tensile and 276 MPa yield.
Q: Can 7075-T6 be welded?
A: It is not normally welded for load-bearing service. Welding causes hot cracking and severe strength loss in the heat affected zone, so riveting, bolting or adhesive bonding are used instead.
Q: Does 7075-T6 corrode in marine service?
A: It needs protection. Copper and zinc reduce general corrosion resistance compared with 5052 or 6061, and chloride exposure causes pitting, so cladding, anodising or a painted system is applied.
Q: What is the density of 7075-T6?
A: About 2.81 g/cm3, roughly one third that of steel, which is the source of its specific strength advantage.
Q: Which tempers are supplied in 7075 sheet and plate?
A: Rolled product is commonly supplied in T6, T651 and T73 tempers, each with its own balance of strength and stress corrosion resistance in ASTM B209.
