Aluminum A242.0-T21
Heat-treated state
AA A242.0 · UNS A12420
T21 = annealed / partially solution treated and stabilised
Soft, highly stable condition used where machining accuracy and freedom from growth outweigh strength.
Values for the T21 condition
Other A242.0 tempers and conditions
A242.0 is listed in 7 conditions; see the grade overview at A242.0.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Raw casting before any thermal treatment; used only as an intermediate state or for non-structural parts. | 105 | 165 | 1.5 | 65 HB | 33 % IACS |
Annealed | Choose when maximum dimensional stability and lowest residual stress matter more than strength. | 124 | 186 | 1 | 70 HB | 44 % IACS |
T21This page Annealed / partially solution treated and stabilised | Soft, highly stable condition used where machining accuracy and freedom from growth outweigh strength. | 124 | 186 | 1.5 | 70 HB | 42 % IACS |
T75Default Solution heat treated and overaged/stabilised | Standard supply condition for A242.0: balanced strength with dimensional stability and creep resistance at 200–260 °C. | 145 | 214 | 2 | 75 HB | 36 % IACS |
Solution heat treated and fully overaged | Pick for parts that run hottest and longest — lowest growth and best residual-stress relief, at reduced strength. | 159 | 207 | 2 | 75 HB | 38 % IACS |
As-cast then artificially aged | Low-distortion route: no solution treatment, good stability and hardness for cylinder heads and pistons. | 207 | 221 | 0.7 | 90 HB | 34 % IACS |
T6 variant, underaged | Highest room-temperature strength and hardness, mainly on permanent-mold castings; ductility is minimal. | 234 | 276 | 0.5 | 105 HB | 33 % IACS |
What is A242.0-T21?
A242.0-T21 is A242.0 heat treated to T21 — soft, highly stable condition used where machining accuracy and freedom from growth outweigh strength. A242.0-T21 has a yield strength of 124 MPa (18 ksi) and a tensile strength of 186 MPa (27 ksi) — weaker than 76% of aluminum grades. Elongation at break is 1.5% and the elastic modulus is 71 GPa (10.3 Msi). A242.0-T21 has a density of 2.81 g/cm³ (0.102 lb/in³), heavier than 86% of aluminum grades. It melts at 528°C (982 °F). T75 is the default condition FabDigit quotes; T21 is available on request or by drawing note.
Advantages
- High service temperature — 300°C (572 °F), better than 99% of aluminum grades
- High electrical conductivity — 42 % IACS, better than 81% of aluminum grades
Limitations
- Limited ductility — 1.5%, worse than 91% of aluminum grades
- Needs corrosion protection — 34/100, worse than 89% of aluminum grades
- Low strength — 124 MPa (18 ksi), worse than 76% of aluminum grades
- Difficult to weld — 25/100, worse than 76% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
A242.0-T21 properties
Typical room-temperature values for A242.0-T21; 22 are specific to this condition. Other listed values are A242.0 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
A242.0-T21 has a density of 2.81 g/cm³ (0.102 lb/in³), heavier than 86% of aluminum grades. It melts at 528°C (982 °F).
Mechanical11
A242.0-T21 has a yield strength of 124 MPa (18 ksi) and a tensile strength of 186 MPa (27 ksi) — weaker than 76% of aluminum grades. Elongation at break is 1.5% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
A242.0-T21 is rated for continuous service to 300°C (572 °F). It conducts heat at 152 W/m·K (87.8 BTU/hr·ft·°F), better than 66% of aluminum grades. Thermal expansion is 22.5 µm/m·K (12.5 µin/in·°F).
Electrical3
A242.0-T21 conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (34/100), worse than 89% of aluminum grades.
Sustainability4
Producing a kilogram of A242.0-T21 takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 25%.
Manufacturability7
A242.0-T21's machinability is good (55/100, worse than 59% of aluminum grades); weldability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A242.0-T21
Is A242.0 easy to machine?
Machines well with sharp carbide tooling and high speeds; Al₃Ni and Al₂Cu particles are abrasive, so use PCD for long runs and flood coolant to avoid built-up edge.
Can A242.0 be welded?
Essentially non-weldable by fusion for structural joints — high Cu content causes hot cracking; repair only by qualified foundry weld procedures followed by re-heat treatment.
Can A242.0 be formed, bent or molded?
Sand and permanent-mold casting only; fluidity is fair and the alloy is hot-tear sensitive, so use generous fillets, chills and directional-solidification gating.
What surface finishes work on A242.0?
Anodizing gives dark, non-decorative films; specify chromate conversion plus primer/paint for corrosion protection, or hard anodize/plating for wear surfaces.
A242.0 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 | ≤ 0.6 | 0.3 |
| Feimpurity limit | ≤ 0.8 | 0.4 |
| Cuprimary strengthener (Al₂Cu) | 3.7 – 4.5 | 4.1 |
| Mn | ≤ 0.1 | 0.05 |
| Mgwith Cu forms S-phase | 1.2 – 1.8 | 1.5 |
| Crdispersoid former, thermal stability | 0.15 – 0.25 | 0.2 |
| NiAl₃Ni for hot strength | 1.8 – 2.3 | 2 |
| Zn | ≤ 0.1 | 0.03 |
| Tigrain refiner | 0.07 – 0.2 | 0.12 |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
A242.0-T21 — frequently asked
What is A242.0-T21 used for?
A242.0-T21 is typically used for cylinder heads, pistons, engine covers and aerospace elevated-temperature parts. In short: best hot-strength cast aluminum; 260 °C service capability; low ductility, not weldable.
What is the yield strength of A242.0-T21?
A242.0-T21 has a typical yield strength of 124 MPa (18 ksi) and a tensile strength of 186 MPa (27 ksi) — weaker than 76% of aluminum grades. Strength varies by condition: see the 7 listed tempers.
Is A242.0-T21 easy to machine?
Reasonably — machinability is rated good (55/100, worse than 59% of aluminum grades). Machines well with sharp carbide tooling and high speeds; Al₃Ni and Al₂Cu particles are abrasive, so use PCD for long runs and flood coolant to avoid built-up edge.
Can A242.0-T21 be welded?
Not readily — weldability is rated poor (25/100). Essentially non-weldable by fusion for structural joints — high Cu content causes hot cracking; repair only by qualified foundry weld procedures followed by re-heat treatment.
What surface finishes work on A242.0-T21?
Anodizing gives dark, non-decorative films; specify chromate conversion plus primer/paint for corrosion protection, or hard anodize/plating for wear surfaces.
Can A242.0-T21 be formed, bent or molded?
Sand and permanent-mold casting only; fluidity is fair and the alloy is hot-tear sensitive, so use generous fillets, chills and directional-solidification gating.
What is the maximum service temperature of A242.0-T21?
A242.0-T21 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A242.0-T75 and A242.0-T61?
T75 is the default condition — standard supply condition for A242.0: balanced strength with dimensional stability and creep resistance at 200–260 °C. T61: highest room-temperature strength and hardness, mainly on permanent-mold castings; ductility is minimal. Yield strength is 145 MPa in T75 versus 234 MPa in T61.
Sources
- Registration Record of International Alloy Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Pink Sheets) — The Aluminum Association (2019)
- 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 and Special-Purpose Materials — ASM International (1990)
- ASM Specialty Handbook — Aluminum and Aluminum Alloys — ASM International (1993)
- 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.