Aluminum 2198-T4
Temper
AA 2198 · UNS A92198
T4 = solution heat treated and naturally aged
Unstretched naturally aged condition used for formed details before final artificial ageing.
Values for the T4 condition
Other 2198 tempers and conditions
2198 is listed in 8 conditions; see the grade overview at 2198.
Compare all 8 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-solution treated and aged for service strength. | 130 | 250 | 22 | 70 HB | 35 % IACS |
T4This page Solution heat treated and naturally aged | Unstretched naturally aged condition used for formed details before final artificial ageing. | 230 | 360 | 22 | 100 HB | 23 % IACS |
Solution heat treated, cold worked and naturally aged | Formable sheet condition for skins that will be stretch-formed or bent, then optionally aged to T8. | 270 | 395 | 20 | 110 HB | 23 % IACS |
T3, stress relieved by stretching | Low-residual-stress plate for machined parts that will be aged after rough machining, or used as-is for high-toughness applications. | 280 | 405 | 18 | 115 HB | 23 % IACS |
Solution treated, ~1 % cold worked and artificially aged | Thin-gauge variant of the aged temper where only light stretching is applied; slightly lower strength, better flatness. | 415 | 470 | 10 | 142 HB | 28 % IACS |
T8Default Solution heat treated, cold worked and artificially aged | Standard supply condition for 2198 fuselage/skin sheet: peak-strength, damage-tolerant, corrosion-stable. | 430 | 480 | 11 | 145 HB | 28 % IACS |
T8, stress relieved by stretching | Peak-aged, low-residual-stress plate for machined ribs, floor beams and integrally machined panels. | 450 | 500 | 8 | 152 HB | 29 % IACS |
Extruded, stretched and artificially aged | Extruded stringers and stiffeners in peak-aged condition where straightness and low residual stress matter. | 470 | 510 | 8 | 155 HB | 29 % IACS |
What is 2198-T4?
2198-T4 is 2198 in the T4 temper — unstretched naturally aged condition used for formed details before final artificial ageing. 2198-T4 has a yield strength of 230 MPa (33.4 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 60% of aluminum grades. Elongation at break is 22% and the elastic modulus is 76 GPa (11 Msi). 2198-T4 has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 560°C (1,040 °F). T8 is the default condition FabDigit quotes; T4 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 46 MPa·√m (41.9 ksi·√in), better than 100% of aluminum grades
- Ductile — tolerates forming and impact — 22%, better than 91% of aluminum grades
- Forms and bends easily — 65/100, better than 80% of aluminum grades
Limitations
- Poor heat conductor — 85 W/m·K (49.1 BTU/hr·ft·°F), worse than 100% of aluminum grades
- Low electrical conductivity — 23 % IACS, worse than 97% of aluminum grades
- Limited service temperature — 100°C (212 °F), worse than 91% of aluminum grades
- Needs corrosion protection — 40/100, worse than 75% of aluminum grades
2198-T4 properties
Typical room-temperature values for 2198-T4; 20 are specific to this condition. Other listed values are 2198 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2198-T4 has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 560°C (1,040 °F).
Mechanical14
2198-T4 has a yield strength of 230 MPa (33.4 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 60% of aluminum grades. Elongation at break is 22% and the elastic modulus is 76 GPa (11 Msi).
Thermal6
2198-T4 is rated for continuous service to 100°C (212 °F). It conducts heat at 85 W/m·K (49.1 BTU/hr·ft·°F), worse than 100% of aluminum grades. Thermal expansion is 23 µm/m·K (12.8 µin/in·°F).
Electrical3
2198-T4 conducts electricity at 23 % IACS, worse than 97% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (40/100), worse than 75% of aluminum grades.
Sustainability4
Producing a kilogram of 2198-T4 takes about 215 MJ of energy and emits 13.5 kg of CO₂ — more than 93% of aluminum grades. Typical recycled content is 5%.
Manufacturability8
2198-T4's machinability is fair (50/100, worse than 65% of aluminum grades); weldability poor (30/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2198-T4
Is 2198 easy to machine?
Machines like a hard 2000 series: sharp polished-flute carbide, high speed, generous coolant; T8/T851 gives good chip control, but keep Li-bearing fines wet and segregated from other Al swarf.
Can 2198 be welded?
Not recommended for conventional MIG/TIG (hot cracking, Li oxidation); friction stir welding and laser beam welding with 4047/4000-series-type filler are the qualified joining routes, otherwise rivet/bolt.
Can 2198 be formed, bent or molded?
Form in T3/T4/O; T8 has limited bend ductility and pronounced planar anisotropy, so orient blanks to rolling direction and allow generous bend radii.
What surface finishes work on 2198?
Standard aerospace chain: alkaline clean, deoxidize, tartaric-sulfuric or chromic anodize, chromate-free conversion coat plus epoxy primer; avoid bare contact with steel or CFRP without sealant.
2198 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 | 2.9 – 3.5 | 3.2 |
| Liprincipal density-reducing / modulus-raising addition | 0.8 – 1.1 | 0.95 |
| Mg | 0.25 – 0.8 | 0.5 |
| Agpromotes fine T1 precipitation | 0.1 – 0.5 | 0.3 |
| Zrgrain-structure control | 0.04 – 0.18 | 0.11 |
| Mn | ≤ 0.5 | — |
| Zn | ≤ 0.35 | — |
| Ti | ≤ 0.1 | — |
| Feimpurity limit | ≤ 0.1 | — |
| Siimpurity limit | ≤ 0.08 | — |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
2198-T4 — frequently asked
What is 2198-T4 used for?
2198-T4 is typically used for fuselage skin, aerospace sheet structure, laser-welded stiffened skin panels, lower wing skin panels, formed frames and clips and extruded stringers for welded panels. In short: most formable Al-Li sheet here; weight saving over 2024; laser and FSW weldable.
What is the yield strength of 2198-T4?
2198-T4 has a typical yield strength of 230 MPa (33.4 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 60% of aluminum grades. Strength varies by condition: see the 8 listed tempers.
Is 2198-T4 easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 65% of aluminum grades). Machines like a hard 2000 series: sharp polished-flute carbide, high speed, generous coolant; T8/T851 gives good chip control, but keep Li-bearing fines wet and segregated from other Al swarf.
Can 2198-T4 be welded?
Not readily — weldability is rated poor (30/100). Not recommended for conventional MIG/TIG (hot cracking, Li oxidation); friction stir welding and laser beam welding with 4047/4000-series-type filler are the qualified joining routes, otherwise rivet/bolt.
What surface finishes work on 2198-T4?
Standard aerospace chain: alkaline clean, deoxidize, tartaric-sulfuric or chromic anodize, chromate-free conversion coat plus epoxy primer; avoid bare contact with steel or CFRP without sealant.
Can 2198-T4 be formed, bent or molded?
Form in T3/T4/O; T8 has limited bend ductility and pronounced planar anisotropy, so orient blanks to rolling direction and allow generous bend radii.
What is the maximum service temperature of 2198-T4?
2198-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 2198-T8 and 2198-O?
T8 is the default condition — standard supply condition for 2198 fuselage/skin sheet: peak-strength, damage-tolerant, corrosion-stable. O: softest condition for severe forming or intermediate processing; must be re-solution treated and aged for service strength. Yield strength is 430 MPa in T8 versus 130 MPa in O.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- AIRWARE 2198 sheet/plate technical data — Constellium (2021)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS — Metallic Materials Properties Development and Standardization (Al-Li chapters) — Battelle/FAA (2023)
- AMS 4472 / AMS 4473 — Aluminum-Lithium alloy sheet and plate — SAE International (2019)
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.