Aluminum AC4A-T7
Temper
JIS AC4A
T7 = solution heat treated and overaged (stabilized)
Pick for parts that run hot or must stay dimensionally stable after machining, accepting some strength loss.
Values for the T7 condition
Other AC4A tempers and conditions
AC4A is listed in 5 conditions; see the grade overview at AC4A.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Cheapest route for low-stress housings and covers where dimensional stability matters more than strength. | 90 | 170 | 4 | 58 HB | 40 % IACS |
Solution heat treated and naturally aged | Choose when maximum ductility and impact toughness are wanted with moderate strength. | 115 | 215 | 8 | 65 HB | 36 % IACS |
Cooled from hot working and artificially aged | Low-distortion strength boost without solution treatment; good for thin, dimension-critical castings. | 145 | 205 | 2.5 | 70 HB | 41 % IACS |
T7This page Solution heat treated and overaged (stabilized) | Pick for parts that run hot or must stay dimensionally stable after machining, accepting some strength loss. | 175 | 230 | 4 | 80 HB | 42 % IACS |
T6Default Solution heat treated and artificially aged | Default condition: highest strength and hardness for load-bearing engine, gearbox and structural castings. | 200 | 260 | 3 | 90 HB | 39 % IACS |
What is AC4A-T7?
AC4A-T7 is AC4A in the T7 temper — pick for parts that run hot or must stay dimensionally stable after machining, accepting some strength loss. AC4A-T7 has a yield strength of 175 MPa (25.4 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 55% of aluminum grades. Elongation at break is 4% and the elastic modulus is 71 GPa (10.3 Msi). AC4A-T7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 557°C (1,035 °F). T6 is the default condition FabDigit quotes; T7 is available on request or by drawing note.
Advantages
- Low embodied carbon — 9.5 kg CO₂/kg, better than 97% of aluminum grades
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
- High electrical conductivity — 42 % IACS, better than 81% of aluminum grades
Limitations
- Limited formability — 10/100, worse than 80% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
AC4A-T7 properties
Typical room-temperature values for AC4A-T7; 21 are specific to this condition. Other listed values are AC4A reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
AC4A-T7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 557°C (1,035 °F).
Mechanical13
AC4A-T7 has a yield strength of 175 MPa (25.4 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 55% of aluminum grades. Elongation at break is 4% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
AC4A-T7 is rated for continuous service to 200°C (392 °F). It conducts heat at 158 W/m·K (91.3 BTU/hr·ft·°F), better than 74% of aluminum grades. Thermal expansion is 21.5 µm/m·K (11.9 µin/in·°F).
Electrical3
AC4A-T7 conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), better than 67% of aluminum grades.
Sustainability4
Producing a kilogram of AC4A-T7 takes about 155 MJ of energy and emits 9.5 kg of CO₂ — less than 94% of aluminum grades. Typical recycled content is 70%.
Manufacturability8
AC4A-T7's machinability is fair (52/100, worse than 63% of aluminum grades); weldability good (65/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AC4A-T7
Is AC4A easy to machine?
Machinable but abrasive — use PCD or polished-flute carbide, high speed with flood coolant or MQL to avoid built-up edge from the eutectic Si.
Can AC4A be welded?
TIG/MIG weldable with ER4043 or ER4047 filler; preheat 150 °C for thick sections and re-solution/age afterwards to restore T6 properties in the HAZ.
Can AC4A be formed, bent or molded?
Foundry alloy with excellent fluidity for sand, permanent-mold and low-pressure casting; degas and Sr-modify the melt, and use directional solidification to avoid shrinkage porosity.
What surface finishes work on AC4A?
Hard anodize for wear (dark grey), chromate/Ti-Zr conversion coat plus powder paint for appearance; shot blasting or impregnation is common to seal microporosity before plating.
AC4A 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 |
|---|---|---|
| Siprimary fluidity/strength former; Sr or Na modification usual | 8 – 10 | 9 |
| MgMg2Si precipitation hardening | 0.3 – 0.6 | 0.45 |
| Mnneutralises Fe needles | 0.3 – 0.6 | 0.45 |
| Feimpurity | ≤ 0.55 | 0.35 |
| Cuimpurity; limits corrosion resistance | ≤ 0.25 | 0.1 |
| Znimpurity | ≤ 0.25 | — |
| Niimpurity | ≤ 0.1 | — |
| Tigrain refiner (Al-Ti-B) | ≤ 0.2 | 0.1 |
| Snimpurity | ≤ 0.05 | — |
| Pbimpurity | ≤ 0.1 | — |
| Al | balance | — |
AC4A-T7 — frequently asked
What is AC4A-T7 used for?
AC4A-T7 is typically used for engine housings, gearbox casings, wheels and structural castings. In short: general-purpose AC casting alloy; heat-treatable Al-Si-Mg; balanced strength and castability.
What is the yield strength of AC4A-T7?
AC4A-T7 has a typical yield strength of 175 MPa (25.4 ksi) and a tensile strength of 230 MPa (33.4 ksi) — weaker than 55% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is AC4A-T7 easy to machine?
Reasonably — machinability is rated fair (52/100, worse than 63% of aluminum grades). Machinable but abrasive — use PCD or polished-flute carbide, high speed with flood coolant or MQL to avoid built-up edge from the eutectic Si.
Can AC4A-T7 be welded?
Yes — weldability is rated good (65/100). TIG/MIG weldable with ER4043 or ER4047 filler; preheat 150 °C for thick sections and re-solution/age afterwards to restore T6 properties in the HAZ.
What surface finishes work on AC4A-T7?
Hard anodize for wear (dark grey), chromate/Ti-Zr conversion coat plus powder paint for appearance; shot blasting or impregnation is common to seal microporosity before plating.
Can AC4A-T7 be formed, bent or molded?
Foundry alloy with excellent fluidity for sand, permanent-mold and low-pressure casting; degas and Sr-modify the melt, and use directional solidification to avoid shrinkage porosity.
What is the maximum service temperature of AC4A-T7?
AC4A-T7 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AC4A-T6 and AC4A-F?
T6 is the default condition — default condition: highest strength and hardness for load-bearing engine, gearbox and structural castings. F: cheapest route for low-stress housings and covers where dimensional stability matters more than strength. Yield strength is 200 MPa in T6 versus 90 MPa in F.
Sources
- JIS H5202 Aluminium alloy castings — JSA (2010)
- GB/T 1173 (ZL104) — SAC (2013)
- EN 1706 Aluminium and aluminium alloys — Castings (EN AC-43000 AlSi10Mg) — CEN (2020)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
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.