Aluminum 2139-T4
Temper
AA 2139 · UNS A92139
T4 = solution heat treated and naturally aged
Use when moderate strength with better ductility is needed, or as the condition for forming before artificial ageing.
Values for the T4 condition
Other 2139 tempers and conditions
2139 is listed in 6 conditions; see the grade overview at 2139.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition for severe forming or intermediate processing; must be re-heat-treated to reach strength. | 85 | 195 | 18 | 50 HB | 47 % IACS |
T4This page Solution heat treated and naturally aged | Use when moderate strength with better ductility is needed, or as the condition for forming before artificial ageing. | 275 | 430 | 20 | 115 HB | 30 % IACS |
Solution heat treated, cold worked and naturally aged | Naturally aged plate/sheet condition when high toughness and formability matter more than peak yield strength. | 315 | 455 | 17 | 125 HB | 30 % IACS |
Solution heat treated and artificially aged | Peak-aged without prior stretching — used for forgings and machined parts where residual stress control is by machining strategy. | 415 | 470 | 9 | 130 HB | 36 % IACS |
T8, stress relieved by stretching | Choose for thick plate that will be heavily machined — stretch stress relief minimises distortion of machined structural parts. | 448 | 480 | 10 | 134 HB | 38 % IACS |
T8Default Solution heat treated, cold worked and artificially aged | The standard supply condition: best combination of strength, fracture toughness and fatigue crack growth resistance for fuselage and armour plate. | 450 | 485 | 11 | 135 HB | 37 % IACS |
What is 2139-T4?
2139-T4 is 2139 in the T4 temper — use when moderate strength with better ductility is needed, or as the condition for forming before artificial ageing. 2139-T4 has a yield strength of 275 MPa (39.9 ksi) and a tensile strength of 430 MPa (62.4 ksi) — stronger than 70% of aluminum grades. Elongation at break is 20% and the elastic modulus is 72 GPa (10.4 Msi). 2139-T4 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 507°C (945 °F). T8 is the default condition FabDigit quotes; T4 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 45 MPa·√m (41 ksi·√in), better than 100% of aluminum grades
- Ductile — tolerates forming and impact — 20%, better than 89% of aluminum grades
Limitations
- Needs corrosion protection — 32/100, worse than 94% of aluminum grades
- Limited service temperature — 100°C (212 °F), worse than 91% of aluminum grades
- Difficult to weld — 20/100, worse than 89% of aluminum grades
2139-T4 properties
Typical room-temperature values for 2139-T4; 11 are specific to this condition. Other listed values are 2139 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2139-T4 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 507°C (945 °F).
Mechanical12
2139-T4 has a yield strength of 275 MPa (39.9 ksi) and a tensile strength of 430 MPa (62.4 ksi) — stronger than 70% of aluminum grades. Elongation at break is 20% and the elastic modulus is 72 GPa (10.4 Msi).
Thermal6
2139-T4 is rated for continuous service to 100°C (212 °F). It conducts heat at 122 W/m·K (70.5 BTU/hr·ft·°F), worse than 74% of aluminum grades. Thermal expansion is 22.7 µm/m·K (12.6 µin/in·°F).
Electrical3
2139-T4 conducts electricity at 30 % IACS, worse than 73% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), worse than 94% of aluminum grades.
Sustainability4
Producing a kilogram of 2139-T4 takes about 205 MJ of energy and emits 12.5 kg of CO₂ — more than 76% of aluminum grades. Typical recycled content is 12%.
Manufacturability8
2139-T4's machinability is good (65/100, better than 62% of aluminum grades); weldability poor (20/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2139-T4
Is 2139 easy to machine?
Machines well in T8 with sharp carbide tooling, high speeds and flood coolant; low Fe/Si content gives clean surfaces, and stretch-relieved T851 plate is preferred for deep pocket milling to limit distortion.
Can 2139 be welded?
Not suitable for fusion (GTAW/GMAW) welding — hot cracking and toughness loss; join by riveting/bolting or use friction stir welding, which retains most base-metal properties.
Can 2139 be formed, bent or molded?
Form in O or T4/T3 condition; T8 plate has limited bend ductility and needs generous radii, warm forming or age-forming for contoured skins.
What surface finishes work on 2139?
Chromic or boric-sulphuric anodize plus epoxy primer, or Alclad/spray-coat protection; bare Cu-rich surfaces pit in chlorides, and cosmetic sulphuric anodize gives grey, non-uniform colour.
2139 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 |
|---|---|---|
| Cu | 4.5 – 5.5 | 5 |
| Mg | 0.2 – 0.8 | 0.5 |
| Agkey micro-alloying addition (Ω-phase former) | 0.15 – 0.6 | 0.4 |
| Mn | 0.2 – 0.6 | 0.3 |
| Siimpurity limit for toughness | ≤ 0.1 | — |
| Feimpurity limit for toughness | ≤ 0.15 | — |
| Zn | ≤ 0.25 | — |
| Ti | ≤ 0.15 | — |
| Others (each)others total 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
2139-T4 — frequently asked
What is 2139-T4 used for?
2139-T4 is typically used for fuselage plate, pressure bulkheads, machined skin panels with integral stiffeners, armor and blast-resistant structural plate, wing and fuselage frames and damage-tolerant structural fittings. In short: silver-modified Al-Cu plate; best machinability in group; damage-tolerant fuselage alloy.
What is the yield strength of 2139-T4?
2139-T4 has a typical yield strength of 275 MPa (39.9 ksi) and a tensile strength of 430 MPa (62.4 ksi) — stronger than 70% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 2139-T4 easy to machine?
Reasonably — machinability is rated good (65/100, better than 62% of aluminum grades). Machines well in T8 with sharp carbide tooling, high speeds and flood coolant; low Fe/Si content gives clean surfaces, and stretch-relieved T851 plate is preferred for deep pocket milling to limit distortion.
Can 2139-T4 be welded?
Not readily — weldability is rated poor (20/100). Not suitable for fusion (GTAW/GMAW) welding — hot cracking and toughness loss; join by riveting/bolting or use friction stir welding, which retains most base-metal properties.
What surface finishes work on 2139-T4?
Chromic or boric-sulphuric anodize plus epoxy primer, or Alclad/spray-coat protection; bare Cu-rich surfaces pit in chlorides, and cosmetic sulphuric anodize gives grey, non-uniform colour.
Can 2139-T4 be formed, bent or molded?
Form in O or T4/T3 condition; T8 plate has limited bend ductility and needs generous radii, warm forming or age-forming for contoured skins.
What is the maximum service temperature of 2139-T4?
2139-T4 is rated for continuous use to about 100°C (212 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 2139-T8 and 2139-O?
T8 is the default condition — the standard supply condition: best combination of strength, fracture toughness and fatigue crack growth resistance for fuselage and armour plate. O: softest condition for severe forming or intermediate processing; must be re-heat-treated to reach strength. Yield strength is 450 MPa in T8 versus 85 MPa in O.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS-style typical property data for 2000-series aerospace plate — Battelle/FAA (2023)
- 2139-T8 high-toughness aluminium plate data (Al-Cu-Mg-Ag) — Alcoa/Constellium (aerospace plate producers) (2016)
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.