Aluminum 204.0-T6
Temper
AA 204.0 · UNS A02040
T6 = solution heat treated and artificially aged
Pick when peak strength and hardness matter more than ductility and toughness; elongation drops sharply versus T4.
Values for the T6 condition
Other 204.0 tempers and conditions
204.0 is listed in 4 conditions; see the grade overview at 204.0.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Rarely supplied; as-cast 204.0 has low strength and is normally only an intermediate state before solution treatment. | 110 | 170 | 4 | 60 HB | 38 % IACS |
T4Default Solution heat treated and naturally aged | The standard commercial condition for 204.0 — best combination of high strength with useful ductility and toughness. | 195 | 320 | 8 | 95 HB | 33 % IACS |
Solution heat treated and overaged (stabilized) | Overaged condition used when dimensional stability at elevated temperature and reduced residual stress are more important than peak strength. | 250 | 300 | 5 | 105 HB | 40 % IACS |
T6This page Solution heat treated and artificially aged | Pick when peak strength and hardness matter more than ductility and toughness; elongation drops sharply versus T4. | 285 | 350 | 3 | 120 HB | 37 % IACS |
What is 204.0-T6?
204.0-T6 is 204.0 in the T6 temper — pick when peak strength and hardness matter more than ductility and toughness; elongation drops sharply versus T4. 204.0-T6 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 73% of aluminum grades. Elongation at break is 3% and the elastic modulus is 72 GPa (10.4 Msi). 204.0-T6 has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 571°C (1,060 °F). T4 is the default condition FabDigit quotes; T6 is available on request or by drawing note.
Advantages
- Easy to machine — 88/100, better than 96% of aluminum grades
- High service temperature — 175°C (347 °F), better than 83% of aluminum grades
Limitations
- Needs corrosion protection — 33/100, worse than 91% of aluminum grades
- Difficult to weld — 20/100, worse than 89% of aluminum grades
- Limited formability — 10/100, worse than 80% of aluminum grades
- Limited ductility — 3%, worse than 79% of aluminum grades
204.0-T6 properties
Typical room-temperature values for 204.0-T6; 15 are specific to this condition. Other listed values are 204.0 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
204.0-T6 has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 571°C (1,060 °F).
Mechanical12
204.0-T6 has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 73% of aluminum grades. Elongation at break is 3% and the elastic modulus is 72 GPa (10.4 Msi).
Thermal6
204.0-T6 is rated for continuous service to 175°C (347 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% of aluminum grades. Thermal expansion is 22.7 µm/m·K (12.6 µin/in·°F).
Electrical3
204.0-T6 conducts electricity at 37 % IACS, better than 58% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (33/100), worse than 91% of aluminum grades.
Sustainability4
Producing a kilogram of 204.0-T6 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 15%.
Manufacturability8
204.0-T6's machinability is excellent (88/100, better than 96% of aluminum grades); weldability poor (20/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 204.0-T6
Is 204.0 easy to machine?
Machines very well in T4/T6 with sharp carbide tools, high speed and moderate feed; chips break cleanly, use flood coolant to avoid built-up edge.
Can 204.0 be welded?
Poor fusion weldability — wide freezing range causes hot cracking; repair welds (4043/2319) require preheat, low restraint and post-weld re-solution treatment to restore properties.
Can 204.0 be formed, bent or molded?
Sand and permanent-mold casting only; needs generous risering, chills and controlled directional solidification because of high shrinkage and hot-tear sensitivity — do not specify for pressure-tight parts.
What surface finishes work on 204.0?
Take painting or chromate/anodize+seal for corrosion protection; sulfuric anodize gives a dark uneven film due to Cu, so use paint or conversion coat for cosmetic parts.
204.0 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 |
|---|---|---|
| Siimpurity limit | ≤ 0.2 | — |
| Fe0.15 max for premium/high-toughness practice | ≤ 0.35 | — |
| Cumain strengthening element | 4.2 – 5 | 4.6 |
| Mn | ≤ 0.1 | — |
| Mg | 0.15 – 0.35 | 0.25 |
| Ni | ≤ 0.05 | — |
| Zn | ≤ 0.1 | — |
| Sn | ≤ 0.05 | — |
| Tigrain refiner | 0.15 – 0.3 | 0.22 |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
204.0-T6 — frequently asked
What is 204.0-T6 used for?
204.0-T6 is typically used for aircraft wheels, structural castings and brackets. In short: high-strength Al-Cu casting; excellent machinability, rating 85; not for pressure-tight parts.
What is the yield strength of 204.0-T6?
204.0-T6 has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 73% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is 204.0-T6 easy to machine?
Yes — machinability is rated excellent (88/100, better than 96% of aluminum grades). Machines very well in T4/T6 with sharp carbide tools, high speed and moderate feed; chips break cleanly, use flood coolant to avoid built-up edge.
Can 204.0-T6 be welded?
Not readily — weldability is rated poor (20/100). Poor fusion weldability — wide freezing range causes hot cracking; repair welds (4043/2319) require preheat, low restraint and post-weld re-solution treatment to restore properties.
What surface finishes work on 204.0-T6?
Take painting or chromate/anodize+seal for corrosion protection; sulfuric anodize gives a dark uneven film due to Cu, so use paint or conversion coat for cosmetic parts.
Can 204.0-T6 be formed, bent or molded?
Sand and permanent-mold casting only; needs generous risering, chills and controlled directional solidification because of high shrinkage and hot-tear sensitivity — do not specify for pressure-tight parts.
What is the maximum service temperature of 204.0-T6?
204.0-T6 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 204.0-T4 and 204.0-T6?
T4 is the default condition — the standard commercial condition for 204.0 — best combination of high strength with useful ductility and toughness. T6: pick when peak strength and hardness matter more than ductility and toughness; elongation drops sharply versus T4. Yield strength is 195 MPa in T4 versus 285 MPa in T6.
Sources
- Registration Record of Aluminum Association Alloy Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Pink Sheets) — The Aluminum Association (2018)
- ASTM B26/B26M — Aluminum-Alloy Sand Castings — ASTM International (2018)
- ASTM B108/B108M — Aluminum-Alloy Permanent Mold Castings — ASTM International (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- EN 1706 — Aluminium and aluminium alloys: castings (AlCu4MgTi / AlCu4Ti) — CEN (2020)
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.