Which aluminium alloy to choose: 6061, 7075, 5052, 5083 and more

At a glance (2195 is left out because its profile ranges include weld values)

Which aluminium alloy is strongest?

7075 and 2195 lead, and our data cannot separate them. 7075 has a typical T6 tube yield of 503 MPa and a tensile strength of 572 MPa. 2195 is listed at 74 ksi yield and 80 ksi tensile for T8 plate (the 510 MPa on the chart) and at minimums of 500 MPa and 560 MPa by another supplier. 7075 is 1.8 times the 6061 typical T6 yield of 276 MPa, a figure whose product form is not stated.

2024 runs 260 to 324 MPa, mixing a typical T4 value, a forged T4 lower bound and T351 plate minimums. Among the medium-strength alloys, 5083 shows 125 to 215 MPa (minimum proof stress in O/H111, H32 and H116, plus one datasheet value), 5052 runs 89.6 to 255 MPa from annealed to H38, and 6063 runs 90 to 214 MPa from a T4 minimum to a typical T6 value. 6061 is 1.3 times the 6063 figure on a typical T6 basis, though the two come from different sources (a typical value for 6061, an approximate printed figure for 6063).

3003 (34.5 to 165 MPa) is the soft end of the alloys. The Aluminium row is commercially pure 1100-O, annealed (29 MPa), not a fair comparison with a T6 alloy.

Which aluminium alloy is lightest, and does weight decide the choice?

Weight rarely decides it. Density runs from 2.65 g/cm³ for 5083 to 2.8 g/cm³ for 7075, which is about 6 % denser, with 5052 at 2.68 g/cm³, 6061 at 2.7 g/cm³, 3003 at 2.73 g/cm³ and 2024 at 2.78 g/cm³. Pure aluminium has 2.7 g/cm³, so alloying and temper add strength at almost no weight cost.

2195 needs a caution. The profile describes it as lighter and stronger than 2219, but its density here is 2.66 to 2.72 g/cm³, inside the range of the others, and the two suppliers disagree. Its modulus (75 to 75.8 GPa) is only a few percent above 2024 (73.1 GPa), 7075 (71 to 71.7 GPa) and 5083 (72 GPa), so treat stiffness as a small advantage.

Which aluminium alloy resists corrosion best?

In air, 6061 has the best-supported record. In sea water, 5083 and 5052 are the choices on supplier ratings. Avoid stressed 7075 and 2024 plate in salt exposure. Most entries are supplier or handbook ratings, not measured rates.

The 1972 NASA handbook ranks 6061 the best-resisting heat-treatable alloy in air and says its resistance does not depend on temper. Aluminium is anodic to most common metals, so in wet or salty contact with a nobler metal it corrodes first, and strong alkalis and hydrochloric and hydrofluoric acids attack it.

Suppliers call 5083 highly resistant to sea water and industrial chemicals, and rate 5052-H32 very good; neither has a measured rate. 3003 is rated very good or excellent in air with no sea-water rating, and 6063 has high corrosion resistance with no environment named.

The weak spots are in the strongest alloys. 7075 is attacked in industrial and marine environments, and T6 is susceptible to stress-corrosion cracking in the short transverse direction. A producer's datasheet (Kaiser) rates T6 C and T73 B for stress corrosion in 3.5% sodium chloride alternate immersion; C is the worse of the two, and the profile does not print the full scale. A 1981 NASA seacoast test, recorded in the 2024 profile, found 2024-T351 and 7075-T651 plate highly susceptible. 2024-T351 failed after very short exposure, and 2024-T851 showed moderate resistance, failing at 75 percent of yield, on limited lots of plate.

2195 is called poorly corrosion resistant by a supplier, though its friction stir welds pitted less than fusion welds in a chloride test. Pure aluminium is protected by its oxide film in moist air but attacked by dilute acids and alkalis.

General engineering knowledge, not in our data: H116 and H321 are tempers generally specified for marine 5083 plate (our data holds H116 only); 2024 is usually clad or coated; 7075 plate is normally specified in T73-type tempers, which give up some yield strength; and stainless fasteners in aluminium need checking for galvanic attack and galling.

Which aluminium alloy welds and forms best?

Our data gives a clear welding answer for only some alloys: 5083 and 6063 carry explicit ratings, datasheets describe 3003 and 5052 as weldable, 2195 needs friction stir welding, and the profiles hold no welding or forming data for 6061, 7075 or 2024. A rating is about weldability, not as-welded strength.

5083 is rated excellent for arc and resistance welding, average for gas welding and poor for brazing, and suppliers say it keeps its strength after welding. A materials-information site (AZoM) recommends filler 5183. 6063 has the broadest excellent ratings: gas, arc and resistance welding and brazing, with filler 5183 or 4043 in general.

For forming, 3003 is the clearest case. Elongation falls from 25 % in the soft O temper to 4 % in H16 and H18. The minimum 90-degree bend radius for 0.064 in (about 1.6 mm) sheet rises from 0 T, meaning zero times the sheet thickness, in O, H12 and H14 to 1/2 to 1 1/2 T in H16 and 1 1/2 to 3 T in H18. A datasheet rates its weldability very good. 5052 is described as having good workability.

2195 is the special case. NASA reports it is more susceptible to hot cracking in fusion welds than 2219, so the Marshall centre began friction stir welding it in 1997. In plate 0.32 in (about 8 mm) thick, friction stir welds averaged 58.7 ksi tensile at room temperature (a little over 400 MPa) and 95.5 ksi at -423 °F, the temperature of liquid hydrogen (a little over 650 MPa). A single fusion weld gave 44 ksi (about 300 MPa) and 58 ksi (about 400 MPa) in the same two conditions, which is one test and only a direction.

General engineering knowledge, not in our data: heat-treatable T6 alloys such as 6061 and 6063 lose a large share of their strength in the zone beside a fusion weld, so design welded T6 parts on the weakened value. Non-heat-treatable 5083 and 5052 suffer less. Fusion welding of 7075 is generally avoided.

Which aluminium alloy conducts heat best, and what do the data say about heat?

Our data covers conduction, melting range and one service limit, but no strength-at-temperature curve for any alloy, so it cannot say which alloy keeps its strength best when hot.

Pure aluminium (1100-O, annealed) conducts best at 220 W/(m·K), then 6063 at 200 W/(m·K) and 3003 at 190 W/(m·K) in the O condition. 6061 gives 167 W/(m·K). The strong alloys conduct less: 130 W/(m·K) for 7075, 121 W/(m·K) for 5083 and 120 to 121 W/(m·K) for 2024. General engineering knowledge, not in our data: strength and conduction tend to trade against each other, which is why 6063 suits heat sinks.

Melting starts at 502 °C for 2024, 532 °C for 7075, 582 °C for 6061 and 607.2 °C for 5052, and ends between 635 and 652 °C for those four. The single values are 570 °C for 5083, 600 °C for 6063, 655 °C for 3003 and 660 °C for pure aluminium. A melting point is not a service limit. The only service limit in our data is for 5083: three suppliers advise against use above 65 °C and none names the reason. General engineering knowledge, not in our data: the limit is generally attributed to sensitisation.

Heat also erases cold-work strength: in a NASA test, 1 hour at 400 °F (about 200 °C) cost stabilised 5052 H39 foil about 10 % of its room-temperature tensile strength, and the profile separately warns that unstabilised H19 and H191 tempers soften during panel cure. Expansion is similar across the alloys but measured over different ranges: 22.9 to 23.2 ppm/K for 2024 (20 to 100 °C), 24.8 ppm/K for 5052 (20 to 200 °C) and 25 ppm/K for 5083 (not stated).

Does anodising change which aluminium alloy to choose?

6063 is the clear anodising choice in our data: suppliers call its anodised finish excellent and say it anodises easily, which is why the profile calls it the architectural extrusion alloy. 7075-T6 appears in the hard-coat data, and 6061 was the alloy in a laboratory salt-spray paper. The profiles hold no anodising data for 2024, 5083 or 3003.

Anodising grows a hard, insulating oxide film. A Type II film is 0.0001 to 0.001 in thick and a Type III hard-coat film is 0.0005 to 0.004 in, according to a summary of MIL-A-8625F,. In one 2026 laboratory salt-spray paper (6061 and a second alloy, up to 80 days), thin sulphuric films of 3 to 5 µm pitted and 6061 pitted less than the other alloy, while thick films of 15 to 20 µm were not penetrated.

Anodized aluminium is a finish, not an alloy, so choose the base alloy by strength, corrosion and welding first. General engineering knowledge, not in our data: hard anodising 7075 or 2024 lowers fatigue strength.

Terms used

Yield strength

the stress at which a metal starts to deform for good. Proof stress is the same idea, measured at a set small permanent stretch.

Temper

the code after the alloy number, such as T6, T651, H32, H116 or O, that records heat treatment or cold work.

Heat-treatable alloy

an alloy that gets its strength from heat treatment, such as 6061 and 7075. A non-heat-treatable alloy, such as 5083, gets it from alloying and cold work.

Stress-corrosion cracking

cracking caused by steady tensile stress and a corrosive environment together.

Short transverse direction

the thickness direction of plate or forging, where high-strength alloys crack most easily.

Galvanic corrosion

extra attack on the less noble metal when two different metals touch in a conductive liquid such as sea water.

Friction stir welding

a solid-state weld made by a rotating tool that stirs the joint without melting it, which avoids the hot cracking of fusion welds.

Filler metal

the wire or rod melted into a weld. 5183 and 4043 are filler alloy grades named in our data.

Sensitisation

a change at the grain boundaries after long warm exposure that makes some magnesium alloys prone to cracking and corrosion.

What to check before you order

1. Name the alloy, the temper (for example T6, T651, H32, H116, O) and the product form on the order and check them on receipt. Our values change across all three.
2. Ask for the certified minimum strength for your form; the numbers here are typical or supplier values, mostly marked not for design.
3. For 7075 and 2024 plate or forgings under sustained tension, ask for stress-corrosion test results in the short transverse direction, and ask whether a more resistant temper such as 7075-T73 is available.
4. For plate to be machined, ask for a stress-relieved temper such as T651, because thick plate can move when large volumes are removed.
5. For 5083, confirm the temper (O/H111, H32 or H116), and keep service at or below 65 °C unless the supplier gives a written higher limit. For any welded part, ask for the filler, the procedure and the tested joint strength, and design on the weaker zone beside the weld.
6. Where aluminium touches steel, copper or carbon in a wet or salty joint, ask how it will be isolated.
7. For anodised parts, state the type (II or III), the class, the film thickness and the sealing on the drawing, and ask for hours-to-failure salt-spray and wear results. Read the supplier safety data sheet before cutting, grinding or welding.

What do we not know yet?

• No welding, brazing or forming data for 6061, 7075 or 2024, and no strength-loss figure beside the weld for any alloy. Weld-zone softening, 5083 sensitisation, the 7075-T73 yield penalty and hard-anodising fatigue loss are general engineering knowledge here, not profile data.
• No design-allowable or ASTM minimum strengths (for example B209 or B221) for most alloys; the charts show ranges from mixed tempers and forms, not like-for-like grades.
• No measured sea-water corrosion rate for 5083, 5052, 3003 or 6063, and no H321 values for 5083. The sea-water statements are supplier ratings.
• No strength-at-temperature, creep or elevated-temperature fatigue data for any alloy, and no 2195 base-metal cryogenic data or thermal conductivity.
• No data on how 2024, 5083 or 3003 anodise, and no cost, lead time or availability data by alloy.

Questions people ask