Aluminum AC4CH-T71
Precip hard
JIS AC4CH · ASTM A356.0
T71 = solution heat treated and strongly overaged
Use where long-term dimensional stability and machining-stress freedom dominate over strength, e.g. optical/instrument housings.
Values for the T71 condition
Other AC4CH tempers and conditions
AC4CH is listed in 7 conditions; see the grade overview at AC4CH.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Lowest-cost condition for lightly loaded or non-structural castings where dimensional stability after machining is not critical. | 90 | 170 | 5 | 55 HB | 42 % IACS |
Solution heat treated and naturally aged | Choose when maximum ductility and impact energy are wanted with moderate strength, e.g. crash-relevant nodes that are later riveted or straightened. | 120 | 230 | 12 | 60 HB | 38 % IACS |
T71This page Solution heat treated and strongly overaged | Use where long-term dimensional stability and machining-stress freedom dominate over strength, e.g. optical/instrument housings. | 140 | 205 | 4 | 60 HB | 41 % IACS |
Cooled from hot working and artificially aged | Use when a strength/stability gain is needed without the distortion risk and cost of solution quenching. | 145 | 200 | 4 | 65 HB | 41 % IACS |
Solution heat treated and overaged (stabilized) | Select for dimensional/thermal stability and lower residual stress in precision or elevated-temperature parts, at some loss of strength. | 205 | 240 | 5 | 75 HB | 40 % IACS |
T6Default Solution heat treated and artificially aged | Default condition for structural and safety-critical castings needing the best combination of strength, elongation and fatigue life. | 210 | 280 | 8 | 85 HB | 39 % IACS |
T6 variant, underaged | Pick for the highest strength/hardness available from AC4CH (JIS min 260 MPa) where some ductility can be traded away. | 240 | 300 | 5 | 95 HB | 39 % IACS |
What is AC4CH-T71?
AC4CH-T71 is AC4CH in the T71 condition — use where long-term dimensional stability and machining-stress freedom dominate over strength, e.g. optical/instrument housings. AC4CH-T71 has a yield strength of 140 MPa (20.3 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 70% of aluminum grades. Elongation at break is 4% and the elastic modulus is 72.4 GPa (10.5 Msi). AC4CH-T71 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; T71 is available on request or by drawing note.
Advantages
- High service temperature — 175°C (347 °F), better than 83% of aluminum grades
- High electrical conductivity — 41 % IACS, better than 78% of aluminum grades
- Conducts heat well — 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades
AC4CH-T71 properties
Typical room-temperature values for AC4CH-T71; 22 are specific to this condition. Other listed values are AC4CH reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
AC4CH-T71 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
AC4CH-T71 has a yield strength of 140 MPa (20.3 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 70% of aluminum grades. Elongation at break is 4% and the elastic modulus is 72.4 GPa (10.5 Msi).
Thermal6
AC4CH-T71 is rated for continuous service to 175°C (347 °F). It conducts heat at 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades. Thermal expansion is 21.5 µm/m·K (11.9 µin/in·°F).
Electrical3
AC4CH-T71 conducts electricity at 41 % IACS, better than 78% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), better than 62% of aluminum grades.
Sustainability4
Producing a kilogram of AC4CH-T71 takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 20%.
Manufacturability8
AC4CH-T71's machinability is good (55/100, worse than 59% of aluminum grades); weldability very good (75/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AC4CH-T71
Is AC4CH easy to machine?
Machines cleanly with PCD or polished-flute carbide tooling, high speed and low feed; eutectic Si abrades HSS quickly and T6 gives better chip control than as-cast F.
Can AC4CH be welded?
Readily TIG/MIG welded with ER4043/ER4145 filler; re-solution + age locally welded structural castings and avoid weld porosity by degassing/pre-machining oxide skin.
Can AC4CH be formed, bent or molded?
Excellent fluidity and low hot-tearing tendency for sand, permanent-mold, low-pressure and squeeze casting; Sr modification plus Ti-B refinement and directional solidification are needed to keep porosity low for T6 properties.
What surface finishes work on AC4CH?
Chromate-free conversion coating or powder paint for cosmetics; hard anodize for wear surfaces (grey tone from Si), and shot peening markedly raises fatigue life of T6 castings.
AC4CH 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 |
|---|---|---|
| SiSr or Na modified for fine eutectic | 6.5 – 7.5 | 7 |
| MgMg2Si strengthening | 0.25 – 0.45 | 0.35 |
| Felow-Fe is the key difference vs AC4C; A356.2 ingot ≤0.12 | ≤ 0.2 | 0.12 |
| Cu | ≤ 0.2 | 0.05 |
| Mn | ≤ 0.1 | 0.03 |
| Zn | ≤ 0.1 | 0.03 |
| Tigrain refinement with Al-Ti-B | ≤ 0.2 | 0.12 |
| Ni | ≤ 0.05 | — |
| Cr | ≤ 0.05 | — |
| Al | balance | — |
AC4CH-T71 — frequently asked
What is AC4CH-T71 used for?
AC4CH-T71 is typically used for automotive suspension components, aerospace castings and high-strength wheels. In short: low-Fe high-integrity A356; highest elongation in family; safety-critical structural castings.
What is the yield strength of AC4CH-T71?
AC4CH-T71 has a typical yield strength of 140 MPa (20.3 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 70% of aluminum grades. Strength varies by condition: see the 7 listed tempers.
Is AC4CH-T71 easy to machine?
Reasonably — machinability is rated good (55/100, worse than 59% of aluminum grades). Machines cleanly with PCD or polished-flute carbide tooling, high speed and low feed; eutectic Si abrades HSS quickly and T6 gives better chip control than as-cast F.
Can AC4CH-T71 be welded?
Yes — weldability is rated very good (75/100). Readily TIG/MIG welded with ER4043/ER4145 filler; re-solution + age locally welded structural castings and avoid weld porosity by degassing/pre-machining oxide skin.
What surface finishes work on AC4CH-T71?
Chromate-free conversion coating or powder paint for cosmetics; hard anodize for wear surfaces (grey tone from Si), and shot peening markedly raises fatigue life of T6 castings.
Can AC4CH-T71 be formed, bent or molded?
Excellent fluidity and low hot-tearing tendency for sand, permanent-mold, low-pressure and squeeze casting; Sr modification plus Ti-B refinement and directional solidification are needed to keep porosity low for T6 properties.
What is the maximum service temperature of AC4CH-T71?
AC4CH-T71 is rated for continuous use to about 175°C (347 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AC4CH-T6 and AC4CH-F?
T6 is the default condition — default condition for structural and safety-critical castings needing the best combination of strength, elongation and fatigue life. F: lowest-cost condition for lightly loaded or non-structural castings where dimensional stability after machining is not critical. Yield strength is 210 MPa in T6 versus 90 MPa in F.
Sources
- JIS H 5202 Aluminium alloy castings — JSA (2010)
- ASTM B26/B26M & B108 (A356.0) / Aluminum Association Pink Sheets (A356.2 ingot) — ASTM / The Aluminum Association (2018)
- ASM Handbook Vol.2 — Properties of Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
- GB/T 1173 ZL101A comparable cast alloy data — SAC (2013)
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.