Aluminum Alloy Table
| Series | Major alloying element | Character and uses |
|---|---|---|
| 1000 | none (99%+ pure Al) | Work-hardens only; foil, chemical equipment, drawn tube (1050, 1060, 1100, 1199) |
| 2000 | copper | Heat-treatable strength; aerospace (2024, 2029 alclad) |
| 3000 | manganese | General sheet and pans; 3003 cookware, 3105 |
| 4000 | silicon | Filler and welding family |
| 5000 | magnesium | Marine plate and tanks |
| 6000 | magnesium + silicon | The extruder alloy (6061, 6063); structural frames |
| 7000 | zinc | Strongest commercial series; aerospace and forgings (7075, 7175) |
| 8000 | other elements | Specialty and packaging alloys outside the seven element families |
| Temper | Meaning |
|---|---|
| -F | As fabricated |
| -O | Full soft (annealed) |
| -H1x / H2x / H3x / H4x | Strain-hardened only / and partially annealed / and stabilized / then lacquered or painted |
| -W | Solution heat-treated only - expires in about 15 minutes at room temperature |
| -T4 | Solution heat-treated and naturally aged |
| -T6 | Solution heat-treated and artificially aged (6061-T6, 7075-T6) |
| -T651 | T6 plus stress relief by stretching |
| -T7 | Solution heat-treated and stabilized |
Every wrought aluminum alloy carries a four-digit number and usually a dash temper, and both halves are a readable spec sheet rather than a serial. The first digit names the major alloying element and therefore the personality: 1000 series is essentially pure aluminum (99 percent minimum, work-hardenable only), 2000 is copper-built aerospace strength, 3000 is manganese sheet metal, 4000 is silicon welding filler, 5000 is the magnesium marine family, 6000 is magnesium-plus-silicon - the extruder's alloy - and 7000 is zinc, the strongest commercial series. The second digit counts modifications of the alloy and the last two identify it within the series: alloy 3105 decodes as the manganese series (3), first modification of 3005 (1), fifth registered alloy (05).
The dash temper tells you the alloy's biography: what was done to it after casting. O is fully soft (annealed), F is as-fabricated off the mill, H is strain-hardened (with a second digit grading quarter-, half- and full-hard), and T is the heat-treated family - T4 solution-treated and naturally aged, T6 solution-treated and artificially aged, the combination behind the famous 6061-T6 and 7075-T6. The strangest entry is W: solution heat-treated only, a soft interim condition that at room temperature typically lasts about 15 minutes before natural aging takes over - a countdown timer, not a finished temper.
How to use
- Choose the series by its element, not its number's fame: 5000 for salt water, 6000 for extrusions and welding-friendly structure, 7000 for maximum strength, 1000 for conductivity and foil, 2000 where aerospace history lives.
- Read the temper as the price of strength: the same 6061 in O temper bends like butter while 6061-T6 springs back - order the temper your fabrication process can actually handle.
- Decode any unknown alloy on sight with the digit law: first digit = series element, second digit = modification count, last two = registry number, dash letter = post-cast treatment (the table gives the full H and T families).
Frequently asked questions
What does T6 mean in 6061-T6 or 7075-T6?
It is the alloy's heat-treatment biography, abbreviated. T means the material was heat-treated to produce a stable temper; the number 6 specifically means solution heat-treated and then artificially aged - held at elevated temperature so the alloying elements precipitate into tiny, strength-raising particles. That single step is why 6061-T6 is several times stronger than the same alloy in O temper, and why the designation is quoted like part of the metal's name: 6061-O, 6061-T4 and 6061-T6 are the same chemistry in three very different states. The nearby codes fill in the process details: T4 is solution-treated and naturally aged at room temperature (more formable, less peak strength), T651 adds stress relief by stretching, and T7 stabilizes rather than maximizes strength for heat-exposure service. When an order or a drawing says T6, it is specifying physics, not marketing - the fabrication shop plans around exactly that strength and springback.
How do I decode a four-digit aluminum alloy number?
Three moves, left to right. First digit: the series - 1000 is at least 99 percent pure aluminum, then the alloying elements run 2000 copper, 3000 manganese, 4000 silicon, 5000 magnesium, 6000 magnesium and silicon together, 7000 zinc, 8000 everything else. Second digit: a modification counter - 0 means the original alloy in the series, and any other digit counts registered variations; the textbook example is 3105, which reads as manganese series (3), first modification of 3005 (1), and 05 as its identity within the series. Last two digits: the registry number that pins the exact chemistry. The system is the International Alloy Designation System, and it applies to wrought alloys; cast alloys use their own three-digit-plus-decimal scheme, which is why casting numbers like 356.0 look different. With the digit law plus the temper table, any stamped number becomes a one-line material datasheet.
What is the -W temper, and why does it expire?
W means solution heat-treated and nothing more - the alloy has been soaked hot enough to dissolve its hardening particles into a solid solution, then quenched, and now it sits in a soft, unstable state waiting for natural aging to begin rebuilding strength. That waiting is the expiration: at ambient temperature the W condition typically lasts only about 15 minutes before aging transforms it, though refrigeration can stretch the clock dramatically (never indefinitely). The W window is a real manufacturing tool: rivets in some aerospace alloys are driven in the W state so they age-harden right in the hole, locking in the joint. You will almost never buy W-temper stock on purpose - it is a transition state, not a shipping condition - but it appears on processing paperwork and explains why heat-treated alloys arrive already at T4 or T6: the supplier did the clock management for you.
Which aluminum series do boats, planes and extrusion shops use?
Each market is basically one series with a supporting cast. Boats live on 5000-series magnesium alloys - marine grades chosen for saltwater corrosion resistance and weldability, which is why hull plate and fuel tanks are 5xxx. Aerospace runs two flags: 2000-series copper alloys like 2024 for airframe structure and 7000-series zinc alloys like 7075 - the strongest commercial family, with forging grades beside it - both heat-treated to T-tempers for service strength. The extrusion world is 6000 country: magnesium-plus-silicon alloys like 6061 and 6063 push through dies easily, heat-treat well, weld well, and cover everything from structural frames to window profiles. The 1000 and 3000 series fill the volume roles - foil, chemical equipment, drawn tube, general sheet (1100 holloware, 3003 pans) - where formability and corrosion resistance matter more than strength. The digit law from the first table is the whole answer: pick the element, then the temper sets the strength.