Aluminum 7108-O (Annealed)
Temper
AA 7108
Softest condition for severe forming or straightening before re-heat-treatment.
Values for the O condition
Other 7108 tempers and conditions
7108 is listed in 10 conditions; see the grade overview at 7108.
Compare all 10 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-heat-treatment. | 75 | 155 | 20 | 45 HB | 39 % IACS |
As fabricated | Mill state of press-exit material sold for further heat treatment or as non-structural sections. | 150 | 250 | 16 | 70 HB | 34 % IACS |
Solution heat treated and naturally aged | Use when sections must be bent, roll-formed or stretch-bent before final artificial aging. | 175 | 280 | 18 | 80 HB | 30 % IACS |
As-welded deposit | Design basis for welded joints in T6 profiles; strength largely recovers after several weeks of natural aging. | 205 | 290 | 10 | 85 HB | 32 % IACS |
Cooled from hot working and artificially aged | Cheapest strengthened condition for press-quenchable profiles where T6 dimensional accuracy is not required. | 295 | 335 | 11 | 100 HB | 33 % IACS |
Solution heat treated and overaged (stabilized) | Pick for thick welded sections or corrosive/humid service where SCC risk outweighs 10 % strength loss. | 295 | 335 | 13 | 100 HB | 37 % IACS |
Overaged for exfoliation-corrosion resistance | Intermediate overage: better exfoliation/SCC resistance than T6 with most of its strength. | 315 | 350 | 12 | 105 HB | 35 % IACS |
T6Default Solution heat treated and artificially aged | Default stocked condition: maximum strength for welded structural profiles and crash members. | 340 | 370 | 11 | 110 HB | 33 % IACS |
T6, stress relieved by stretching | Choose when machined parts must stay dimensionally stable after heavy stock removal. | 345 | 375 | 10 | 112 HB | 33 % IACS |
Very slightly overaged | Automotive bumper-beam/crash-box temper: near-T6 strength with improved bendability and crash folding behaviour. | 355 | 385 | 12 | 112 HB | 34 % IACS |
What is 7108-O?
7108-O is 7108 in the O temper — softest condition for severe forming or straightening before re-heat-treatment. 7108-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 155 MPa (22.5 ksi) — weaker than 91% of aluminum grades. Elongation at break is 20% and the elastic modulus is 70 GPa (10.2 Msi). 7108-O has a density of 2.78 g/cm³ (0.1 lb/in³), heavier than 74% of aluminum grades. It melts at 600°C (1,112 °F). T6 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- Forms and bends easily — 85/100, better than 91% of aluminum grades
- Ductile — tolerates forming and impact — 20%, better than 89% of aluminum grades
- Conducts heat well — 180 W/m·K (104 BTU/hr·ft·°F), better than 86% of aluminum grades
- Readily welded — 85/100, better than 79% of aluminum grades
Limitations
- Low strength — 75 MPa (10.9 ksi), worse than 91% of aluminum grades
- Difficult to machine — 35/100, worse than 86% of aluminum grades
7108-O properties
Typical room-temperature values for 7108-O; 20 are specific to this condition. Other listed values are 7108 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
7108-O has a density of 2.78 g/cm³ (0.1 lb/in³), heavier than 74% of aluminum grades. It melts at 600°C (1,112 °F).
Mechanical12
7108-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 155 MPa (22.5 ksi) — weaker than 91% of aluminum grades. Elongation at break is 20% and the elastic modulus is 70 GPa (10.2 Msi).
Thermal6
7108-O is rated for continuous service to 150°C (302 °F). It conducts heat at 180 W/m·K (104 BTU/hr·ft·°F), better than 86% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7108-O conducts electricity at 39 % IACS, better than 65% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (65/100), better than 71% of aluminum grades.
Sustainability4
Producing a kilogram of 7108-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
7108-O's machinability is fair (35/100, worse than 86% of aluminum grades); weldability excellent (85/100); formability excellent (85/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7108-O
Is 7108 easy to machine?
Machines well in T5/T6 with sharp polished-flute carbide tools, high speed and generous coolant; O/T4 tempers are gummy and give poor surface finish.
Can 7108 be welded?
Excellent MIG/TIG and FSW behaviour with 5356/5183 filler; HAZ softening is partly recovered by natural aging, but keep the HAZ out of sustained tensile short-transverse stress to avoid SCC.
Can 7108 be formed, bent or molded?
Best formed in T4/T5 (stretch-bending, roll-forming) with generous bend radii; T6/T79 tolerate only mild bends and press-quenching from the extrusion press is standard for thin profiles.
What surface finishes work on 7108?
Takes clear and hard anodizing well (slightly grey/yellow tint versus 6060/6063), chromate-free conversion coating and powder paint are common for automotive profiles.
7108 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 |
|---|---|---|
| Si | ≤ 0.1 | 0.06 |
| Femax (7108A allows up to 0.15) | ≤ 0.1 | 0.07 |
| Cumax; Cu-free class for weldability | ≤ 0.05 | 0.02 |
| Mn | ≤ 0.05 | 0.02 |
| Mg | 0.7 – 1.4 | 1 |
| Cr | ≤ 0.05 | 0.02 |
| Zn | 4.5 – 5.5 | 5 |
| Zrrecrystallisation control | 0.12 – 0.25 | 0.16 |
| Ti | ≤ 0.05 | 0.02 |
| Others (each)each | ≤ 0.05 | — |
| Others (total)total | ≤ 0.15 | — |
| Al | balance | — |
7108-O — frequently asked
What is 7108-O used for?
7108-O is typically used for welded structural extrusions, transport frames and ladders. In short: weldable 7000-series extrusion alloy; HAZ recovers by natural aging; stronger than 6082.
What is the yield strength of 7108-O?
7108-O has a typical yield strength of 75 MPa (10.9 ksi) and a tensile strength of 155 MPa (22.5 ksi) — weaker than 91% of aluminum grades. Strength varies by condition: see the 10 listed tempers.
Is 7108-O easy to machine?
Not especially — machinability is rated fair (35/100, worse than 86% of aluminum grades). Machines well in T5/T6 with sharp polished-flute carbide tools, high speed and generous coolant; O/T4 tempers are gummy and give poor surface finish.
Can 7108-O be welded?
Yes — weldability is rated excellent (85/100). Excellent MIG/TIG and FSW behaviour with 5356/5183 filler; HAZ softening is partly recovered by natural aging, but keep the HAZ out of sustained tensile short-transverse stress to avoid SCC.
What surface finishes work on 7108-O?
Takes clear and hard anodizing well (slightly grey/yellow tint versus 6060/6063), chromate-free conversion coating and powder paint are common for automotive profiles.
Can 7108-O be formed, bent or molded?
Best formed in T4/T5 (stretch-bending, roll-forming) with generous bend radii; T6/T79 tolerate only mild bends and press-quenching from the extrusion press is standard for thin profiles.
What is the maximum service temperature of 7108-O?
7108-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 7108-T6 and 7108-O?
T6 is the default condition — default stocked condition: maximum strength for welded structural profiles and crash members. O: softest condition for severe forming or straightening before re-heat-treatment. Yield strength is 340 MPa in T6 versus 75 MPa in O.
Sources
- 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 and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol. 13B: Corrosion — Materials (Al-Zn-Mg corrosion & SCC) — ASM International (2005)
- Extrusion alloy data for Al-Zn-Mg automotive profiles (7003/7108 class) — Hydro Aluminium Extrusion (2021)
- EN 755-2 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles: mechanical properties — CEN (2016)
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.