Aluminum 2A21-T4
Temper · default condition
GB 2A21
T4 = solution heat treated and naturally aged
Standard supply condition for rivet wire — driven cold within the specified time window after quenching, then ages in place.
Values for the T4 condition
Other 2A21 tempers and conditions
2A21 is listed in 4 conditions; see the grade overview at 2A21.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition for wire drawing, cold heading of large rivets and intermediate processing before solution treatment. | 80 | 175 | 18 | 45 HB | 44 % IACS |
T4DefaultThis page Solution heat treated and naturally aged | Standard supply condition for rivet wire — driven cold within the specified time window after quenching, then ages in place. | 210 | 350 | 16 | 100 HB | 28 % IACS |
T6, heat treated by the user | Used when parts are formed or machined soft and then re-solution-treated and aged to full heat-resistant strength. | 275 | 390 | 11 | 115 HB | 30 % IACS |
Solution heat treated and artificially aged | Choose when the joint or part must keep strength at 200–250 °C; peak-aged θ' structure is thermally stable but ductility drops. | 290 | 400 | 10 | 118 HB | 30 % IACS |
What is 2A21-T4?
2A21-T4 is 2A21 in the T4 temper — standard supply condition for rivet wire — driven cold within the specified time window after quenching, then ages in place. 2A21-T4 has a yield strength of 210 MPa (30.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 56% of aluminum grades. Elongation at break is 16% and the elastic modulus is 73 GPa (10.6 Msi). 2A21-T4 has a density of 2.84 g/cm³ (0.103 lb/in³), heavier than 93% of aluminum grades. It melts at 543°C (1,009 °F).
Advantages
- Ductile — tolerates forming and impact — 16%, better than 84% of aluminum grades
- Tough — resists crack growth — 32 MPa·√m (29.1 ksi·√in), better than 83% 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
- Poor heat conductor — 116 W/m·K (67 BTU/hr·ft·°F), worse than 84% of aluminum grades
- Low electrical conductivity — 28 % IACS, worse than 82% of aluminum grades
2A21-T4 properties
Typical room-temperature values for 2A21-T4; 14 are specific to this condition. Other listed values are 2A21 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2A21-T4 has a density of 2.84 g/cm³ (0.103 lb/in³), heavier than 93% of aluminum grades. It melts at 543°C (1,009 °F).
Mechanical13
2A21-T4 has a yield strength of 210 MPa (30.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 56% of aluminum grades. Elongation at break is 16% and the elastic modulus is 73 GPa (10.6 Msi).
Thermal6
2A21-T4 is rated for continuous service to 175°C (347 °F). It conducts heat at 116 W/m·K (67 BTU/hr·ft·°F), worse than 84% of aluminum grades. Thermal expansion is 22.3 µm/m·K (12.4 µin/in·°F).
Electrical3
2A21-T4 conducts electricity at 28 % IACS, worse than 82% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (33/100), worse than 91% of aluminum grades.
Sustainability4
Producing a kilogram of 2A21-T4 takes about 210 MJ of energy and emits 12.5 kg of CO₂ — more than 88% of aluminum grades. Typical recycled content is 15%.
Manufacturability7
2A21-T4's machinability is good (58/100, worse than 54% of aluminum grades); weldability good (60/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2A21-T4
Is 2A21 easy to machine?
Machines like other 2000-series heat-treated Al — sharp uncoated carbide, high speed, generous coolant; T4/T6 chips well, annealed material is gummy.
Can 2A21 be welded?
One of the better-welding 2000-series types (2219-like): GTAW/GMAW with ER2319 filler, no hot-cracking filler needed from 4000 series; post-weld re-solution + age restores strength, do not weld in T6 without requalifying joint properties.
Can 2A21 be formed, bent or molded?
Cold-head or upset rivets in the freshly quenched T4 window (or refrigerate to hold the temper); annealed stock forms readily but requires full re-heat-treatment afterwards.
What surface finishes work on 2A21?
Chromic or sulfuric anodize plus chromate/primer for corrosion protection — expect a dull yellow-grey film; alclad or wet-installed sealant is standard where joints see moisture, and avoid direct contact with steel or carbon fibre.
2A21 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 |
|---|---|---|
| Cumain strengthening element, Al₂Cu/θ' | 5.8 – 6.8 | 6.3 |
| Mn | 0.2 – 0.4 | 0.3 |
| Tigrain refinement | 0.1 – 0.2 | 0.15 |
| Vraises recrystallisation/thermal stability | 0.05 – 0.15 | 0.1 |
| ZrAl₃Zr dispersoids | 0.1 – 0.25 | 0.18 |
| Siimpurity | ≤ 0.2 | — |
| Feimpurity | ≤ 0.3 | — |
| Mgimpurity | ≤ 0.02 | — |
| Znimpurity | ≤ 0.1 | — |
| Others (each)total ≤ 0.15 | ≤ 0.05 | — |
| Albalance, per GB/T 3190 Al-Cu-Mn-Ti-V-Zr type (2219 analogue) — verify against mill certificate | balance | — |
2A21-T4 — frequently asked
What is 2A21-T4 used for?
2A21-T4 is typically used for high-temperature aircraft rivets, engine mount fasteners, firewall and cowling riveted joints, riveted splices near heat sources, solid rivet wire and rod stock and riveted ducting and shroud assemblies. In short: best-welding 2000-series rivet alloy; strength to 175 °C; 2219-class rivet stock.
What is the yield strength of 2A21-T4?
2A21-T4 has a typical yield strength of 210 MPa (30.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 56% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is 2A21-T4 easy to machine?
Reasonably — machinability is rated good (58/100, worse than 54% of aluminum grades). Machines like other 2000-series heat-treated Al — sharp uncoated carbide, high speed, generous coolant; T4/T6 chips well, annealed material is gummy.
Can 2A21-T4 be welded?
Yes — weldability is rated good (60/100). One of the better-welding 2000-series types (2219-like): GTAW/GMAW with ER2319 filler, no hot-cracking filler needed from 4000 series; post-weld re-solution + age restores strength, do not weld in T6 without requalifying joint properties.
What surface finishes work on 2A21-T4?
Chromic or sulfuric anodize plus chromate/primer for corrosion protection — expect a dull yellow-grey film; alclad or wet-installed sealant is standard where joints see moisture, and avoid direct contact with steel or carbon fibre.
Can 2A21-T4 be formed, bent or molded?
Cold-head or upset rivets in the freshly quenched T4 window (or refrigerate to hold the temper); annealed stock forms readily but requires full re-heat-treatment afterwards.
What is the maximum service temperature of 2A21-T4?
2A21-T4 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 2A21-T4 and 2A21-O?
T4 is the default condition — standard supply condition for rivet wire — driven cold within the specified time window after quenching, then ages in place. O: softest condition for wire drawing, cold heading of large rivets and intermediate processing before solution treatment. Yield strength is 210 MPa in T4 versus 80 MPa in O.
Sources
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (2219 data used as analogue) — ASM International (1990)
- MMPDS-17 (2219 property basis) — Battelle/FAA (2022)
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.