Aluminum AC7A-O (Annealed)
Temper
JIS AC7A
Optional low-temperature anneal used to relieve casting and machining stresses and stabilise dimensions; slightly lowers strength and hardness.
Values for the O condition
Other AC7A tempers and conditions
AC7A is listed in 3 conditions; see the grade overview at AC7A.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page Annealed | Optional low-temperature anneal used to relieve casting and machining stresses and stabilise dimensions; slightly lowers strength and hardness. | 75 | 160 | 12 | 46 HB | 36 % IACS |
F-SDefault F | Standard supply condition for AC7A sand castings — marine fittings, decorative and food-contact parts needing corrosion resistance and polish. | 85 | 170 | 9 | 50 HB | 35 % IACS |
F | Choose for thinner, finer-grained sections and slightly higher strength/hardness than sand casting, in the same as-cast F condition. | 95 | 190 | 12 | 55 HB | 35 % IACS |
What is AC7A-O?
AC7A-O is AC7A in the O temper — optional low-temperature anneal used to relieve casting and machining stresses and stabilise dimensions; slightly lowers strength and hardness. AC7A-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 160 MPa (23.2 ksi) — weaker than 91% of aluminum grades. Elongation at break is 12% and the elastic modulus is 71 GPa (10.3 Msi). AC7A-O has a density of 2.65 g/cm³ (0.0957 lb/in³), lighter than 90% of aluminum grades. It melts at 599°C (1,110 °F). F-S is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 90/100, better than 98% of aluminum grades
- Good corrosion resistance — 80/100, better than 97% of aluminum grades
Limitations
- Low strength — 75 MPa (10.9 ksi), worse than 91% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
AC7A-O properties
Typical room-temperature values for AC7A-O; 22 are specific to this condition. Other listed values are AC7A reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
AC7A-O has a density of 2.65 g/cm³ (0.0957 lb/in³), lighter than 90% of aluminum grades. It melts at 599°C (1,110 °F).
Mechanical12
AC7A-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 160 MPa (23.2 ksi) — weaker than 91% of aluminum grades. Elongation at break is 12% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
AC7A-O is rated for continuous service to 120°C (248 °F). It conducts heat at 141 W/m·K (81.5 BTU/hr·ft·°F), better than 50% of aluminum grades. Thermal expansion is 24.3 µm/m·K (13.5 µin/in·°F).
Electrical3
AC7A-O conducts electricity at 36 % IACS, better than 55% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 97% of aluminum grades.
Sustainability4
Producing a kilogram of AC7A-O takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 55%.
Manufacturability7
AC7A-O's machinability is good (66/100, better than 66% of aluminum grades); weldability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AC7A-O
Is AC7A easy to machine?
Machines cleanly but is gummy — use sharp polished-flute carbide tools, high rake, high speed and generous coolant to avoid built-up edge and smeared surfaces.
Can AC7A be welded?
Readily TIG/MIG welded with 5356 or 5183 filler; no post-weld heat treatment required and weld corrosion resistance matches the base metal.
Can AC7A be formed, bent or molded?
Difficult to cast: low fluidity, heavy melt oxidation and hot-tearing tendency — use flux/cover gas or SF6-free protective melting, chills, generous risers and fast controlled pouring; avoid thin intricate sections.
What surface finishes work on AC7A?
Ideal for bright/decorative and clear anodizing and for high mechanical polish thanks to very low Si; also takes chemical conversion coating and paint well.
AC7A 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 |
|---|---|---|
| Mgprimary strengthening/solid-solution element | 3.5 – 5.5 | 4.5 |
| Sikept low for bright anodizing | ≤ 0.2 | 0.1 |
| Fe | ≤ 0.3 | 0.15 |
| Culimited to protect corrosion resistance | ≤ 0.1 | 0.03 |
| Mn | ≤ 0.6 | 0.15 |
| Ni | ≤ 0.05 | — |
| Zn | ≤ 0.15 | — |
| Tigrain refiner | ≤ 0.2 | 0.1 |
| Pb | ≤ 0.05 | — |
| Sn | ≤ 0.05 | — |
| Croptional, per equivalent EN AC-51000 | ≤ 0.15 | — |
| Al | balance | — |
AC7A-O — frequently asked
What is AC7A-O used for?
AC7A-O is typically used for marine fittings, decorative hardware, food equipment parts and architectural castings. In short: most corrosion-resistant AC grade; polishable silicon-free casting; poor castability trade-off.
What is the yield strength of AC7A-O?
AC7A-O has a typical yield strength of 75 MPa (10.9 ksi) and a tensile strength of 160 MPa (23.2 ksi) — weaker than 91% of aluminum grades. Strength varies by condition: see the 3 listed tempers.
Is AC7A-O easy to machine?
Reasonably — machinability is rated good (66/100, better than 66% of aluminum grades). Machines cleanly but is gummy — use sharp polished-flute carbide tools, high rake, high speed and generous coolant to avoid built-up edge and smeared surfaces.
Can AC7A-O be welded?
Yes — weldability is rated very good (80/100). Readily TIG/MIG welded with 5356 or 5183 filler; no post-weld heat treatment required and weld corrosion resistance matches the base metal.
What surface finishes work on AC7A-O?
Ideal for bright/decorative and clear anodizing and for high mechanical polish thanks to very low Si; also takes chemical conversion coating and paint well.
Can AC7A-O be formed, bent or molded?
Difficult to cast: low fluidity, heavy melt oxidation and hot-tearing tendency — use flux/cover gas or SF6-free protective melting, chills, generous risers and fast controlled pouring; avoid thin intricate sections.
What is the maximum service temperature of AC7A-O?
AC7A-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 AC7A F-S and AC7A F-P?
F-S is the default condition — standard supply condition for AC7A sand castings — marine fittings, decorative and food-contact parts needing corrosion resistance and polish. F-P: choose for thinner, finer-grained sections and slightly higher strength/hardness than sand casting, in the same as-cast F condition. Yield strength is 85 MPa in F-S versus 95 MPa in F-P.
Sources
- JIS H5202 — Aluminium alloy castings — Japanese Standards Association (2010)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys (514.0) — ASM International (1990)
- EN 1706 — Aluminium and aluminium alloys, castings (EN AC-51000 AlMg3 / AlMg5 family) — CEN (2020)
- Aluminum Association Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot — The Aluminum Association (2019)
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.