Aluminum Alloys Guide
Wrought alloy families, tempers and machinability of 6061, 6063, 7075, 2024 and 5052
Aluminum alloys are grouped by alloying system: 1xxx pure, 2xxx copper, 5xxx magnesium, 6xxx magnesium-silicide and 7xxx zinc. The 6xxx series dominates machined parts because it combines good strength, excellent machinability, corrosion resistance and anodizability at moderate cost; 7075 and 2024 are chosen for high strength where weight matters most.
1. Alloy families and designations
Wrought aluminum is designated by the AA four-digit system: the first digit is the major alloying element, and the temper follows the alloy, e.g. 6061-T6 where T6 means solution heat-treated and artificially aged. Cast alloys use a three-digit plus decimal system (A356, A380) and behave differently in machining and finishing.
For machined parts the practical shortlist is 6061-T6 (general structural), 6063-T6 (extrusions and anodized trim), 7075-T6 (aerospace, high strength), 2024-T3 (fatigue-critical aircraft skins) and 5052-H32 (marine and sheet forming). All are available as bar, plate and billet.
2. Mechanical properties and tempers
6061-T6 delivers roughly 310 MPa ultimate tensile strength, 276 MPa yield and 12–17% elongation, with hardness about 95 HB; 7075-T6 nearly doubles the yield to ~503 MPa at the cost of toughness and weldability. Properties are stable in the T6 condition; soft (O, H112) tempers machine with stringy chips but cut faster.
Modulus of elasticity is ~68–70 GPa for all aluminum alloys — about one-third of steel — so stiffness-limited designs need thicker sections or ribs. Thermal conductivity is high (≈170 W/m·K for 6061), which matters for heat sinks but complicates welding and anodizing consistency.
3. Machining and finishing
Aluminum is the easiest structural metal to machine: high cutting speeds, excellent surface finish (Ra 0.8–1.6 µm readily), and no coolant requirement for most operations. Free-machining grades include 6061-T6511 (as extruded bar) and 2011-T3; 7075 machines well but produces fine chips that demand chip management.
Anodizing (Type II decorative, 5–25 µm; Type III hard coat, 25–75 µm) is the standard protective finish, dyed black or clear. Chromate conversion (chem film / alodine) is used under paint and for corrosion protection. ASTM B209 (sheet/plate) and B211 (bar) define supply specifications.
4. Selection guidance
Choose 6061-T6 unless the application needs higher strength (7075-T6), better fatigue (2024), corrosion/marine performance (5052) or maximum anodized aesthetics (6063). Weldability ranks 6061 (good with 5356 filler), 5052 (excellent), 7075 (poor — use mechanical joints).
For cost estimation, aluminum price index is among the lowest of the engineering metals; dimensional stability is good but thermal expansion (≈23 µm/m·K) must be considered in precision assemblies at temperature.
Quick reference
| Alloy | UTS MPa | Yield MPa | Elong % | Density g/cm³ | Best for |
|---|---|---|---|---|---|
| 6061-T6 | 310 | 276 | 12–17 | 2.70 | General machined parts |
| 6063-T6 | 241 | 214 | 12 | 2.70 | Extrusions, anodized trim |
| 7075-T6 | 572 | 503 | 11 | 2.81 | Aerospace high strength |
| 2024-T3 | 469 | 324 | 19 | 2.78 | Fatigue-critical, aircraft |
| 5052-H32 | 228 | 193 | 12 | 2.68 | Marine, sheet forming |
| 1100-O | 110 | 105 | 12–30 | 2.71 | Deep drawing, foil |
Sources & references
- ASTM B209 — Aluminum sheet and plate
- ASTM B211 — Aluminum bar, rod and wire
- AA Aluminum Alloy Designations
- Xometry Learning Center — Aluminum Guide (public engineering reference)