Aluminum 7108A-O (Annealed)
Temper
AA 7108A · EN AlZn5Mg1Zr, AW-7108A
Softest condition for severe forming or straightening before re-solution treatment and aging.
Values for the O condition
Other 7108A tempers and conditions
7108A is listed in 6 conditions; see the grade overview at 7108A.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page Annealed | Softest condition for severe forming or straightening before re-solution treatment and aging. | 90 | 200 | 20 | 50 HB | 42 % IACS |
Solution heat treated and naturally aged | Formable intermediate condition; strength continues to climb slowly at room temperature, so fabricate then artificially age. | 190 | 300 | 18 | 78 HB | 31 % IACS |
Cooled from hot working and artificially aged | Economical press-quench temper for thin-wall sections where full T6 solution treatment is not required. | 280 | 335 | 11 | 98 HB | 34 % IACS |
Slightly overaged | Choose when sustained tensile loads in humid/chloride service make SCC resistance more important than the last few percent of strength. | 300 | 350 | 12 | 100 HB | 37 % IACS |
T6Default Solution heat treated and artificially aged | Standard stocked condition for welded structural extrusions needing peak strength with good HAZ recovery. | 315 | 360 | 12 | 105 HB | 35 % IACS |
T6 with improved mechanical properties | Tightly controlled T6 aging route guaranteeing higher minimum strengths for crash and load-bearing extrusions. | 350 | 390 | 10 | 115 HB | 34 % IACS |
What is 7108A-O?
7108A-O is 7108A in the O temper — softest condition for severe forming or straightening before re-solution treatment and aging. 7108A-O has a yield strength of 90 MPa (13.1 ksi) and a tensile strength of 200 MPa (29 ksi) — weaker than 87% of aluminum grades. Elongation at break is 20% and the elastic modulus is 70 GPa (10.2 Msi). 7108A-O has a density of 2.78 g/cm³ (0.1 lb/in³), heavier than 74% of aluminum grades. It melts at 610°C (1,130 °F). T6 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 45 MPa·√m (41 ksi·√in), better than 100% of aluminum grades
- Readily welded — 90/100, better than 90% of aluminum grades
- Ductile — tolerates forming and impact — 20%, better than 89% of aluminum grades
- Forms and bends easily — 80/100, better than 89% of aluminum grades
- Conducts heat well — 175 W/m·K (101.1 BTU/hr·ft·°F), better than 85% of aluminum grades
Limitations
- Low strength — 90 MPa (13.1 ksi), worse than 87% of aluminum grades
- Difficult to machine — 35/100, worse than 86% of aluminum grades
7108A-O properties
Typical room-temperature values for 7108A-O; 21 are specific to this condition. Other listed values are 7108A reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
7108A-O has a density of 2.78 g/cm³ (0.1 lb/in³), heavier than 74% of aluminum grades. It melts at 610°C (1,130 °F).
Mechanical13
7108A-O has a yield strength of 90 MPa (13.1 ksi) and a tensile strength of 200 MPa (29 ksi) — weaker than 87% of aluminum grades. Elongation at break is 20% and the elastic modulus is 70 GPa (10.2 Msi).
Thermal6
7108A-O is rated for continuous service to 150°C (302 °F). It conducts heat at 175 W/m·K (101.1 BTU/hr·ft·°F), better than 85% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7108A-O conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), better than 62% of aluminum grades.
Sustainability4
Producing a kilogram of 7108A-O takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 25%.
Manufacturability8
7108A-O's machinability is fair (35/100, worse than 86% of aluminum grades); weldability excellent (90/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7108A-O
Is 7108A easy to machine?
Machines cleanly in T5/T6/T66 with sharp polished-flute carbide tooling, high speed and generous coolant; annealed and T4 material tends to smear and build up on edges.
Can 7108A be welded?
Designed for MIG/TIG welding with 5356 or 5183 filler — the HAZ naturally re-ages over several weeks to recover roughly 70–80 % of parent strength; avoid excessive heat input and allow post-weld natural aging before proof loading.
Can 7108A be formed, bent or molded?
Extrude and form in O or T4; bending in T6/T66 needs generous radii (≥3–4 t) and preferably a stress-relieved section, and heavy cold work after aging risks cracking.
What surface finishes work on 7108A?
Takes protective sulphuric anodising and powder coating well after alkaline etch and desmut; decorative bright anodising is duller than 6000 series and welds anodise a different shade.
7108A 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 |
|---|---|---|
| ZnPrimary hardener with Mg (MgZn2) | 4.5 – 5.2 | 4.8 |
| Mg | 0.7 – 1.4 | 1 |
| ZrAl3Zr dispersoids control recrystallisation and grain size | 0.12 – 0.25 | 0.16 |
| Si | ≤ 0.1 | 0.05 |
| FeA-variant allows a higher Fe ceiling than base 7108 | ≤ 0.25 | 0.15 |
| Cumax — kept low for weldability/corrosion | ≤ 0.05 | 0.02 |
| Mn | ≤ 0.05 | 0.02 |
| Cr | ≤ 0.05 | 0.01 |
| Ti | ≤ 0.05 | 0.02 |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
7108A-O — frequently asked
What is 7108A-O used for?
7108A-O is typically used for welded structural extrusions, bicycle components and transport frames. In short: weldable high-strength 7000 series; zr-refined fine grain; HAZ re-ages naturally.
What is the yield strength of 7108A-O?
7108A-O has a typical yield strength of 90 MPa (13.1 ksi) and a tensile strength of 200 MPa (29 ksi) — weaker than 87% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 7108A-O easy to machine?
Not especially — machinability is rated fair (35/100, worse than 86% of aluminum grades). Machines cleanly in T5/T6/T66 with sharp polished-flute carbide tooling, high speed and generous coolant; annealed and T4 material tends to smear and build up on edges.
Can 7108A-O be welded?
Yes — weldability is rated excellent (90/100). Designed for MIG/TIG welding with 5356 or 5183 filler — the HAZ naturally re-ages over several weeks to recover roughly 70–80 % of parent strength; avoid excessive heat input and allow post-weld natural aging before proof loading.
What surface finishes work on 7108A-O?
Takes protective sulphuric anodising and powder coating well after alkaline etch and desmut; decorative bright anodising is duller than 6000 series and welds anodise a different shade.
Can 7108A-O be formed, bent or molded?
Extrude and form in O or T4; bending in T6/T66 needs generous radii (≥3–4 t) and preferably a stress-relieved section, and heavy cold work after aging risks cracking.
What is the maximum service temperature of 7108A-O?
7108A-O is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7108A-T6 and 7108A-O?
T6 is the default condition — standard stocked condition for welded structural extrusions needing peak strength with good HAZ recovery. O: softest condition for severe forming or straightening before re-solution treatment and aging. Yield strength is 315 MPa in T6 versus 90 MPa in O.
Sources
- EN 573-3 Aluminium and aluminium alloys — Chemical composition of wrought products — CEN (2019)
- EN 755-2 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles: mechanical properties — CEN (2016)
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (Al-Zn-Mg SCC behaviour) — ASM International (2005)
- Al-Zn-Mg weldable extrusion alloy datasheets (7005/7020/7108 class) — Hydro / Constellium extrusion divisions (2022)
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.