Aluminum 7A09-O (Annealed)
Temper
GB 7A09
Softest condition for deep forming, straightening or machining before heat treatment; must be re-solution treated and aged for service.
Values for the O condition
Other 7A09 tempers and conditions
7A09 is listed in 10 conditions; see the grade overview at 7A09.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page Annealed | Softest condition for deep forming, straightening or machining before heat treatment; must be re-solution treated and aged for service. | 105 | 230 | 16 | 60 HB | 47 % IACS |
T73, stress relieved by stretching | Thick plate for machined airframe fittings needing both low residual stress and SCC immunity. | 420 | 490 | 12 | 130 HB | 40 % IACS |
Solution heat treated and overaged for stress-corrosion resistance | Pick for short-transverse loaded forgings and fasteners in humid/marine service where SCC must be eliminated, accepting ~10% lower strength. | 435 | 505 | 11 | 135 HB | 40 % IACS |
T74, stress relieved by stretching | Thick plate version of T74 for machined spars/bulkheads balancing strength, toughness and SCC resistance. | 445 | 515 | 11 | 137 HB | 38 % IACS |
Overaged between T73 and T76 | Compromise temper for heavy forgings: most of the T73 SCC benefit with higher strength than T73. | 455 | 525 | 10 | 140 HB | 38 % IACS |
T76, stress relieved by stretching | Stress-relieved T76 for machined thin-web panels needing exfoliation resistance and dimensional stability. | 460 | 525 | 10 | 140 HB | 38 % IACS |
T6, heat treated by the user | Choose when parts are formed/forged soft and heat treated after machining; properties slightly below mill T6. | 470 | 545 | 7 | 145 HB | 33 % IACS |
Overaged for exfoliation-corrosion resistance | Sheet/extrusion temper for thin skins and stringers where exfoliation resistance is required but T73 strength loss is unacceptable. | 470 | 535 | 9 | 142 HB | 38 % IACS |
T6, stress relieved by stretching | Plate temper for thick machined structures where low residual stress and dimensional stability matter. | 495 | 560 | 9 | 148 HB | 33 % IACS |
T6Default Solution heat treated and artificially aged | Default stocked condition: maximum strength for bar, extrusion and forging where SCC exposure is controlled. | 505 | 570 | 8 | 150 HB | 33 % IACS |
What is 7A09-O?
7A09-O is 7A09 in the O temper — softest condition for deep forming, straightening or machining before heat treatment; must be re-solution treated and aged for service. 7A09-O has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 84% of aluminum grades. Elongation at break is 16% and the elastic modulus is 71 GPa (10.3 Msi). 7A09-O has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 477°C (891 °F). T6 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- High electrical conductivity — 47 % IACS, better than 88% of aluminum grades
- Ductile — tolerates forming and impact — 16%, better than 84% of aluminum grades
- Conducts heat well — 173 W/m·K (100 BTU/hr·ft·°F), better than 84% of aluminum grades
- Forms and bends easily — 60/100, better than 77% of aluminum grades
Limitations
- Difficult to weld — 18/100, worse than 94% of aluminum grades
- Low strength — 105 MPa (15.2 ksi), worse than 84% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
7A09-O properties
Typical room-temperature values for 7A09-O; 10 are specific to this condition. Other listed values are 7A09 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
7A09-O has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 477°C (891 °F).
Mechanical15
7A09-O has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 84% of aluminum grades. Elongation at break is 16% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
7A09-O is rated for continuous service to 120°C (248 °F). It conducts heat at 173 W/m·K (100 BTU/hr·ft·°F), better than 84% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7A09-O conducts electricity at 47 % IACS, better than 88% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 62% of aluminum grades.
Sustainability4
Producing a kilogram of 7A09-O takes about 210 MJ of energy and emits 12.5 kg of CO₂ — more than 88% of aluminum grades. Typical recycled content is 15%.
Manufacturability8
7A09-O's machinability is fair (45/100, worse than 72% of aluminum grades); weldability poor (18/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7A09-O
Is 7A09 easy to machine?
Excellent chip formation in T6/T73; use sharp carbide, high speed and flood coolant, and rough from stress-relieved (T651/T7351) stock to avoid distortion.
Can 7A09 be welded?
Not arc-weldable (hot cracking, severe HAZ SCC); join by fasteners, bonding or friction stir welding, and re-heat-treat if welded.
Can 7A09 be formed, bent or molded?
Form in O or freshly quenched W temper; hot forge/extrude at ~380–450 °C, then solution treat 465–475 °C, water quench and age (T6: ~120 °C; T73/T74: two-step overage).
What surface finishes work on 7A09?
Chromate/trivalent conversion coat or Type II/III anodize for corrosion protection; anodic film is grey-bronze, so decorative bright anodizing is not recommended.
7A09 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 | 5.1 – 6.1 | 5.6 |
| Mg | 2 – 3 | 2.5 |
| Cu | 1.2 – 2 | 1.6 |
| Crgrain-boundary control / SCC resistance | 0.16 – 0.3 | 0.22 |
| Mn | ≤ 0.15 | — |
| Feimpurity | ≤ 0.5 | — |
| Siimpurity | ≤ 0.5 | — |
| Ti | ≤ 0.1 | — |
| Other (each)total 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
7A09-O — frequently asked
What is 7A09-O used for?
7A09-O is typically used for aircraft structural parts, high-strength forgings and machined structural components. In short: highest-strength 7000-series grade; 7178-equivalent property level; low ductility, not weldable.
What is the yield strength of 7A09-O?
7A09-O has a typical yield strength of 105 MPa (15.2 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 84% of aluminum grades. Strength varies by condition: see the 10 listed tempers.
Is 7A09-O easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 72% of aluminum grades). Excellent chip formation in T6/T73; use sharp carbide, high speed and flood coolant, and rough from stress-relieved (T651/T7351) stock to avoid distortion.
Can 7A09-O be welded?
Not readily — weldability is rated poor (18/100). Not arc-weldable (hot cracking, severe HAZ SCC); join by fasteners, bonding or friction stir welding, and re-heat-treat if welded.
What surface finishes work on 7A09-O?
Chromate/trivalent conversion coat or Type II/III anodize for corrosion protection; anodic film is grey-bronze, so decorative bright anodizing is not recommended.
Can 7A09-O be formed, bent or molded?
Form in O or freshly quenched W temper; hot forge/extrude at ~380–450 °C, then solution treat 465–475 °C, water quench and age (T6: ~120 °C; T73/T74: two-step overage).
What is the maximum service temperature of 7A09-O?
7A09-O 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 7A09-T6 and 7A09-O?
T6 is the default condition — default stocked condition: maximum strength for bar, extrusion and forging where SCC exposure is controlled. O: softest condition for deep forming, straightening or machining before heat treatment; must be re-solution treated and aged for service. Yield strength is 505 MPa in T6 versus 105 MPa in O.
Sources
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys (7075/7178 data) — ASM International (1990)
- MMPDS-16 typical/design values for 7000-series wrought products — Battelle/FAA (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.