Aluminium-lithium alloy 2195 2195 (Al-Cu-Li)
Al balance
Alloy 2195 is an aluminium-copper-lithium alloy.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Strength at room temperature
80 ksi
Strength at -423 degF
95.5 ksi
Stiffness
75 GPa
Density
2.72 g/cm3
Recipe, share of the weight
- Al balance (the rest)Aluminium
- Cu 3.7 to 4.3%Copper
- Li 0.8 to 1.2%Lithium
- Mg 0.25 to 0.8%Magnesium
- Ag 0.25 to 0.6%Silver
- Zr 0.04 to 0.18%Zirconium
Best for
Welded cryogenic tanks where friction stir welding keeps most of the strength (NASA reports, 1998 to 2008)
Weakest at
Fusion welding, which hot-cracks and needs repairs, and corrosion resistance, which the supplier calls poor
Risk at a glance
- People None found. No hazard classification found
- If it fails Moderate. Hot cracking in fusion welds
- Corrosion Moderate. Friction stir welds of 2195 resist pitting better than the fusion-welded (VPPA) joints in the same test.
Quick facts: 2195 (Al-Cu-Li)
| Property | Value | Basis |
|---|---|---|
| Density | 2.66 to 2.72 g/cm³ | 2 sourced values across conditions |
| Yield strength | 252 to 510 MPa | 3 sourced values across conditions |
| Tensile strength | 303 to 560 MPa | 4 sourced values across conditions |
| Young's modulus | 75 to 75.8 GPa | 2 sourced values across conditions |
| Melting point | 549 °C | 1 sourced value |
What is the density of Aluminium-lithium alloy 2195?
Aluminium-lithium alloy 2195 has a density of 2.66 to 2.72 g/cm³. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the melting point of Aluminium-lithium alloy 2195?
Aluminium-lithium alloy 2195 has a melting point of 549 °C. The source and test conditions are listed in the properties table on this page.
What is the yield strength of Aluminium-lithium alloy 2195?
Aluminium-lithium alloy 2195 has a yield strength of 252 to 510 MPa. The range covers 3 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the tensile strength of Aluminium-lithium alloy 2195?
Aluminium-lithium alloy 2195 has a tensile strength of 303 to 560 MPa. The range covers 4 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the Young's modulus of Aluminium-lithium alloy 2195?
Aluminium-lithium alloy 2195 has a Young's modulus of 75 to 75.8 GPa. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is Aluminium-lithium alloy 2195 used for?
Uses recorded in the sources include Launch Vehicle Stage Adapter (LVSA) for the Space Launch System; Space Shuttle Super Lightweight External Tank; Falcon 9 propellant tanks (as reported by Wikipedia).
Why it exists
Alloy 2195 was used to save mass in large cryogenic tanks. Wikipedia describes it as stronger and less dense than 2219. It was adopted for the Space Shuttle Super Lightweight External Tank, where it replaced 2219 in several locations. Its drawback is that it hot-cracks in fusion welds, which led NASA Marshall to develop friction stir welding for it from 1997 onward.
Where it's used
Space Shuttle External Tank
The External Tank was made of 2195 and 2219 aluminium alloys, joined by automatic plasma arc welding. The Super Lightweight Tank then used 2195 at several locations on the liquid oxygen and liquid hydrogen tanks.
Space Launch System
The Launch Vehicle Stage Adapter, which connects the initial core stage to the upper stage, consists of 16 panels of 2195. The SLS core-stage tanks are 2219, not 2195, according to a 2013 magazine report.
Falcon 9
Wikipedia says 2195 is used for the propellant tanks of the Falcon 9. This was not checked against a SpaceX source.
Recipe
Al balance; 3.7 to 4.3 Cu, 0.8 to 1.2 Li, 0.25 to 0.8 Mg, 0.25 to 0.6 Ag, 0.04 to 0.18 Zr (wt%)
Alloy 2195 is an aluminium-copper-lithium alloy. Aluminium makes up the balance. Copper and lithium are the main alloying additions, with smaller additions of magnesium, silver and zirconium, as ranges given by Metal Suppliers Online.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Aluminium Al | balance (the rest) | The matrix of the alloy. |
| Copper Cu | 3.7 to 4.3% | Main alloying addition listed in the supplier's composition table. |
| Lithium Li | 0.8 to 1.2% | Main lithium addition, the element that gives the alloy its name. |
| Magnesium Mg | 0.25 to 0.8% | Minor addition listed in the composition table. |
| Silver Ag | 0.25 to 0.6% | Minor addition listed in the composition table. |
| Zirconium Zr | 0.04 to 0.18% | Minor addition listed in the composition table. Stanford Advanced Materials gives 0.08 to 0.16 wt%. |
Weight shares are as printed in the sources.
What it can do
Strength at room temperature
80 ksi
measured
The T8 temper is listed at 80 ksi ultimate tensile strength and 74 ksi yield at 70 degF. Friction stir welds of the 0.32 inch plate averaged 58.7 ksi at room temperature.
Strength at -423 degF
95.5 ksi
measured
Friction stir welds averaged 95.5 ksi ultimate tensile strength at -423 degF, a factor of 1.6 over room temperature as the report states. The fusion weld of the same plate reached 58 ksi at that temperature.
Stiffness
75 GPa
measured
The modulus is 75 GPa on one datasheet and 11 MSI on the other. Neither gives a temper for the value.
Density
2.72 g/cm3
measured
One datasheet gives 2.72 g/cm3. The other gives 0.096 lb/in3. The two do not agree, so use a certified specification.
How it compares
Alloy 2195 is a lighter, stronger alternative to 2219 for the cryogenic tank application that NASA chose it for. It has a high alloying content, which gives it strength but poor corrosion resistance, according to the supplier. Its welded strength depends heavily on the welding process: friction stir welds keep much more strength than fusion welds of the same plate.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | 2195 (Al-Cu-Li) | 6061 | 7075-T6 | 2024 | 5052 | 5XXX | Al | 1050 | 2011 | 2014 | 2017 | 2017A | 2219 | 2319 | 2618A | 3003 | 3103 | 4047 | 5019 | 5056 | 5083 | AlMg2 | AlMg3 | 6013 | 6063 | 6082 | 6101 | AA7050 | AA8011 | Au-Al IMCs | Al master alloys |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | |||||||||||||||||||||||||||||||
| Melting point (single value listed) | 1020 degF2 | no data | 532 °C | no data | 607.2 to 649 °C | no data | 660 °C | 645 to 657 °C | 540 °C | 535 °C | 510 °C | 510 °C | 543 °C | 543 to 643 °C | 549 °C | 655 °C | 655 °C | 1068 to 1080 °F | 575 to 630 °C | 565 to 640 °C | 570 °C | 605 to 650 °C | 590 to 645 °C | 579 °C | 600 °C | 575 °C | 1090 °F | 490 °C | 640 to 655 °C | no data | 880 °C |
| Physical and electrical | |||||||||||||||||||||||||||||||
| Density, as printed by a metals supplierPhysical properties table, as printed | 0.096 lb/in3 | 2.7 g/cm³ | 2.8 Mg/m3 | 2.78 g/cc | 2.68 g/cc | 2.68 g/cm³ | 2.7 g/cm³ | 2.71 g/cm³ | 2.82 g/cm³ | 2.82 g/cm³ | 2.79 g/cm³ | 2.79 g/cm³ | 2.84 g/cm³ | 2.84 g/cm³ | 2.76 g/cm³ | 2.73 g/cm³ | 2.73 g/cm³ | 2.65 g/cm³ | 2.64 g/cm³ | 2.64 g/cm³ | 2.65 g/cm³ | 2.69 g/cm³ | 2.67 g/cm³ | 2.71 g/cm³ | 2700 kg/m3 | 2.7 g/cm³ | 0.097 lb/cu.in | 2.83 g/cm³ | 2.71 g/cm³ | no data | no data |
| Density, as printed by a second supplierDatasheet value, as printed | 2.72 g/cm³1 | 2.7 g/cm³ | 2.8 Mg/m3 | 2.78 g/cc | 2.68 g/cc | 2.68 g/cm³ | 2.7 g/cm³ | 2.71 g/cm³ | 2.82 g/cm³ | 2.82 g/cm³ | 2.79 g/cm³ | 2.79 g/cm³ | 2.84 g/cm³ | 2.84 g/cm³ | 2.76 g/cm³ | 2.73 g/cm³ | 2.73 g/cm³ | 2.65 g/cm³ | 2.64 g/cm³ | 2.64 g/cm³ | 2.65 g/cm³ | 2.69 g/cm³ | 2.67 g/cm³ | 2.71 g/cm³ | 2700 kg/m3 | 2.7 g/cm³ | 0.097 lb/cu.in | 2.83 g/cm³ | 2.71 g/cm³ | no data | no data |
| Other measurements | |||||||||||||||||||||||||||||||
| Modulus of elasticity, imperial unitsPhysical properties table, as printed | 11 MSI | 68.9 GPa | 71 GPa | 73.1 GPa | 70.3 GPa | 70.3 GPa | 69 GPa | 69000 MPa | 70 GPa | 71 GPa | 72 GPa | 72 GPa | 73.8 x10^3 N/mm2 | no data | 71 GPa | 69.5 GPa | 69.5 GPa | no data | 70 GPa | 71 GPa | 72 GPa | 70 GPa | 70 GPa | 71 GPa | 69.5 GPa | 70 GPa | no data | 71.5 GPa | 70 GPa | no data | no data |
| Elastic modulus, metric unitsDatasheet value, as printed | 75 GPa | 68.9 GPa | 71 GPa | 73.1 GPa | 70.3 GPa | 70.3 GPa | 69 GPa | 69000 MPa | 70 GPa | 71 GPa | 72 GPa | 72 GPa | 73.8 x10^3 N/mm2 | no data | 71 GPa | 69.5 GPa | 69.5 GPa | no data | 70 GPa | 71 GPa | 72 GPa | 70 GPa | 70 GPa | 71 GPa | 69.5 GPa | 70 GPa | no data | 71.5 GPa | 70 GPa | no data | no data |
| Tensile strength, T8 temper at 70 degF (listed)Mechanical properties table, as printed | 80 ksi3 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Yield strength, T8 temper at 70 degF (listed)Mechanical properties table, as printed | 74 ksi4 | 276 MPa | 503 MPa | 324 MPa | 13 ksi | 193 MPa | 29 MPa | > 85 MPa | 140 MPa | > 400 MPa | 276 MPa | 276 MPa | > 50 ksi | 70 MPa | 350 MPa | 50 MPa | > 110 MPa | 55 MPa | no data | no data | > 125 MPa | > 120 MPa | > 80 MPa | 350 MPa | 21 ksi | > 255 MPa | 28000 psi | > 414 MPa | no data | no data | no data |
| elongationMechanical properties table, as printed | 8 %5 | 17 % | 11 % | 19 % | 25 % | 12 % | 50 to 65 % | 4 to 8 % | 16 % | > 6 % | 18 % | 18 % | > 6 % | 12 % | > 5 % | 25 % | > 8 % | 12 % | > 2 % | 20 % | > 12 % | 4 to 12 % | > 12 % | 4 % | 8 % | > 9 % | > 8 % | > 7 % | > 1 % | no data | no data |
| Tensile strength, T8 minimum | > 560 MPa6 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Yield strength, T8 minimum (Rp0.2) | > 500 MPa7 | 276 MPa | 503 MPa | 324 MPa | 13 ksi | 193 MPa | 29 MPa | > 85 MPa | 140 MPa | > 400 MPa | 276 MPa | 276 MPa | > 50 ksi | 70 MPa | 350 MPa | 50 MPa | > 110 MPa | 55 MPa | no data | no data | > 125 MPa | > 120 MPa | > 80 MPa | 350 MPa | 21 ksi | > 255 MPa | 28000 psi | > 414 MPa | no data | no data | no data |
| Elongation, T8 minimum | > 6 %8 | 17 % | 11 % | 19 % | 25 % | 12 % | 50 to 65 % | 4 to 8 % | 16 % | > 6 % | 18 % | 18 % | > 6 % | 12 % | > 5 % | 25 % | > 8 % | 12 % | > 2 % | 20 % | > 12 % | 4 to 12 % | > 12 % | 4 % | 8 % | > 9 % | > 8 % | > 7 % | > 1 % | no data | no data |
| Friction stir weld, room temperature, average FtuAverage of tensile tests as printed in Table 1 | 58.7 ksi9 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Friction stir weld, room temperature, average FtyAverage of tensile tests as printed in Table 1 | 36.6 ksi10 | 276 MPa | 503 MPa | 324 MPa | 13 ksi | 193 MPa | 29 MPa | > 85 MPa | 140 MPa | > 400 MPa | 276 MPa | 276 MPa | > 50 ksi | 70 MPa | 350 MPa | 50 MPa | > 110 MPa | 55 MPa | no data | no data | > 125 MPa | > 120 MPa | > 80 MPa | 350 MPa | 21 ksi | > 255 MPa | 28000 psi | > 414 MPa | no data | no data | no data |
| Friction stir weld, cryogenic (-423 degF), average Ftu | 95.5 ksi11 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Friction stir weld, cryogenic (-423 degF), average Fty | 60 ksi12 | 276 MPa | 503 MPa | 324 MPa | 13 ksi | 193 MPa | 29 MPa | > 85 MPa | 140 MPa | > 400 MPa | 276 MPa | 276 MPa | > 50 ksi | 70 MPa | 350 MPa | 50 MPa | > 110 MPa | 55 MPa | no data | no data | > 125 MPa | > 120 MPa | > 80 MPa | 350 MPa | 21 ksi | > 255 MPa | 28000 psi | > 414 MPa | no data | no data | no data |
| Fusion weld, room temperature, Ftu (comparison) | 44 ksi13 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Fusion weld, cryogenic (-423 degF), Ftu (comparison) | 58 ksi14 | 310 MPa | 572 MPa | 469 MPa | 28 ksi | 228 MPa | 88 MPa | 105 to 145 MPa | 300 MPa | > 460 MPa | 427 MPa | 427 MPa | > 62 ksi | 160 MPa | 420 MPa | 110 MPa | > 140 MPa | 124 MPa | 270 to 350 MPa | 300 MPa | 275 to 350 MPa | 190 to 230 MPa | 190 to 260 MPa | 410 MPa | 27 ksi | > 300 MPa | 32000 psi | > 483 MPa | 180 to 195 MPa | no data | no data |
| Cryogenic strength enhancement factor, friction stir weldFactor stated in the report text | 1.6 ratio | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data |
Why choose it, and why not
Good for
- Cryogenic tanks where weld strength at -423 degF matters. Friction stir welds averaged 95.5 ksi there.
- Structures that need a low density and high stiffness, such as the Launch Vehicle Stage Adapter panels.
Watch out for
- Fusion welding hot-cracks this alloy and leads to repairs with lower properties.
- Corrosion resistance is poor according to the supplier, and welded joints pit at their edges in chloride tests.
- Vendor composition and property pages disagree on some values, so check a certified specification.
Alloy 2195 is a good cryogenic tank alloy when it is friction stir welded. Its low weld tolerance and weak corrosion resistance mean the weld process and protective finishes need to be specified.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, as printed by a second supplier | — | form 2195 alloy, no temper stated | The two supplier pages do not agree on density (see the lb/in3 entry above). Use a certified specification for design. |
| 2 | Melting point (single value listed) | Physical properties table, as printed; the page gives one value, not a range | form 2195-T8 | — |
| 3 | Tensile strength, T8 temper at 70 degF (listed) | — | temper T8form plate and sheettemperature 70 degF | — |
| 4 | Yield strength, T8 temper at 70 degF (listed) | — | temper T8form plate and sheettemperature 70 degF | — |
| 5 | elongation | — | temper T8form plate and sheettemperature 70 degF | — |
| 6 | Tensile strength, T8 minimum | Minimum value as printed on a datasheet page; vendor page, not a standard | temper T8basis minimum (Rm) | — |
| 7 | Yield strength, T8 minimum (Rp0.2) | Minimum value as printed on a datasheet page; vendor page, not a standard | temper T8basis minimum (Rp0.2) | — |
| 8 | Elongation, T8 minimum | Minimum value as printed on a datasheet page; vendor page, not a standard | temper T8basis minimum (A) | — |
| 9 | Friction stir weld, room temperature, average Ftu | — | product 2195-T8 plate, 0.32 in. plate-to-plate friction stir weldtemperature room temperaturen 178basis average | — |
| 10 | Friction stir weld, room temperature, average Fty | — | product 2195-T8 plate, 0.32 in. plate-to-plate friction stir weldtemperature room temperaturen 178basis average | — |
| 11 | Friction stir weld, cryogenic (-423 degF), average Ftu | Average of cryogenic tensile tests as printed in Table 1 | product 2195-T8 plate, 0.32 in. plate-to-plate friction stir weldtemperature -423 degFn 149basis average | — |
| 12 | Friction stir weld, cryogenic (-423 degF), average Fty | Average of cryogenic tensile tests as printed in Table 1 | product 2195-T8 plate, 0.32 in. plate-to-plate friction stir weldtemperature -423 degFn 149basis average | — |
| 13 | Fusion weld, room temperature, Ftu (comparison) | Single result as printed in Table 1 (no yield value given) | product 2195-T8 plate, 0.32 in. fusion weldtemperature room temperaturen 1 | Only one fusion-weld specimen is listed in the table; treat it as indicative. |
| 14 | Fusion weld, cryogenic (-423 degF), Ftu (comparison) | Single result as printed in Table 1 (no yield value given) | product 2195-T8 plate, 0.32 in. fusion weldtemperature -423 degFn 1 | Only one fusion-weld specimen is listed in the table; treat it as indicative. |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Sodium chloride solution (3.5 per cent NaCl) with a scanning reference electrode | moderate | Friction stir welds of 2195 resist pitting better than the fusion-welded (VPPA) joints in the same test.1 |
| General service, as described by a metals supplier | moderate | The supplier calls 2195 poorly corrosion resistant, because its high alloying pushes it toward strength.2 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Sodium chloride solution (3.5 per cent NaCl) with a scanning reference electrode | NASA Marshall measured local surface potentials on 2195 welds. The paper reports that anodic regions sit at the edges of both weld types, and that corrosion and pitting occur at the edges of the fusion welds. The potential needed to reach the minimum detectable signal was 200 mV for the VPPA weld and 600 mV for the friction stir weld, which the authors read as the friction stir weld being less subject to corrosion. The study uses a micro-galvanic method, not a corrosion-rate test. | electrolyte 3.5 per cent NaCl solutionmethod scanning reference electrode technique, 2195 unwelded, VPPA-welded and friction stir weldedexposure not a long-term immersion test |
| 2 | General service, as described by a metals supplier | Metal Suppliers Online states that the alloy has bad workability and poor corrosion resistance, and that being highly alloyed it tends to fall on the higher-strength and lower-corrosion-resistance side. It gives no test data. Treat this as a qualitative warning for design, backed by the NASA pitting results above. | basis qualitative statement in a general encyclopedia article; no test conditions |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
No safety data sheet for the alloy was opened in this run, so this section is limited to what the sources say about handling the welded product.
- Welding
- Friction stir welding is the route NASA chose for this alloy because fusion welds hot-crack and need repairs.
- Fumes and dust
- No fume or dust data for the alloy were read. Treat machining swarf with the care given to any aluminium-lithium material until a safety data sheet is checked.
If a joint fails or corrodes
These results are from laboratory and design tests, not from flight failures.
- Fusion welds
- NASA reports that fusion welds of 2195 hot-crack and need more repairs. The repairs leave reduced properties, which is why the External Tank programme moved to friction stir welding.
- Pitting
- In a chloride test, the fusion-welded joints pitted at their edges, and a higher potential was needed to reach the detection level for friction stir welds.
Handling and storage
- Repair welds
- NASA's repair study found room-temperature and cryogenic FSW repair welds met the minimum design strength, with an allowable about 5 ksi lower at -423 degF than the initial weld.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Hot cracking in fusion weldsmoderate severity | Fusion welding (automatic plasma arc welding) of 2195 during Space Shuttle External Tank manufactureNASA reports that 2195 is more susceptible to hot cracking during fusion welding than 2219, so it needs more repairs, and the repairs leave reduced weld properties. This led MSFC to start friction stir welding for 2195 in 1997. |
| Pitting at weld edgesmoderate severity | Exposure of fusion-welded 2195 to chloride solution in a micro-galvanic testAnodic zones at the weld edges corroded and pitted in the test, and the VPPA weld needed a much lower potential to reach the detection level than the friction stir weld. |
Handling and storage
- Friction stir welds of 0.32 inch plate averaged 58.7 ksi at room temperature, against 44 ksi for the fusion weld listed. NASA reports room-temperature and cryogenic FSW repair welds exceeding the minimum design strength, though with an allowable roughly 5 ksi lower at -423 degF than the initial weld.
Mitigations
- Friction stir welding replaces fusion welding for 2195 joints, and the report records that repaired FSW joints still met design minimums at both temperatures.
Supply and geography
How common the raw materials are and where they come from.
Aluminium (primary smelter production, the main metal of the alloy)
- Top producers (2025)
- China 60.8%, Russia 5.3%, India 5.7%, Canada 4.5%
- Recycling
- USGS aluminum chapter describes secondary production from old and new scrap, which decreased slightly in 2025 in the United States.
- Substitutes
- USGS: composites can substitute for aluminum in aircraft fuselages and wings, and copper can replace aluminum in electrical and heat-exchange applications.
Bauxite (aluminium feedstock)
USGS: global bauxite resources are estimated at 55 billion to 75 billion tons, sufficient to meet world aluminium demand well into the future.
Lithium
20 ppm in the Earth's crust (USGS table of crustal abundances, citing Jefferson Science Associates, 2014)
- Top producers (2025)
- Australia 31.7%, China 21.4%, Chile 19.3%, Zimbabwe 9.7%, Argentina 7.9%
- Critical mineral lists
- US: listed, EU: listed
- Recycling
- USGS: construction of lithium battery recycling plants continued throughout 2025.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
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spore: profile
id: aluminium-lithium-2195
spore_version: 0.2
family: aluminium-alloys
name: Aluminium-lithium alloy 2195
abbreviation: "2195 (Al-Cu-Li)"
role: structural alloy
category: metals
type: aluminium
summary: >
Alloy 2195 is an aluminium-copper-lithium alloy. Wikipedia describes it as lighter and stronger than 2219 for cryogenic
tanks. The Space Shuttle Super Lightweight External Tank used it, and NASA reports say it is more susceptible to hot
cracking in fusion welds than 2219, which is why friction stir welding was adopted for it. In NASA-funded tests, friction
stir welds in 0.32 inch plate reached 95.5 ksi ultimate tensile strength at -423 degF, against 58 ksi for a single
fusion weld of the same plate.
best_for: "Welded cryogenic tanks where friction stir welding keeps most of the strength (NASA reports, 1998 to 2008)"
weakest_at: "Fusion welding, which hot-cracks and needs repairs, and corrosion resistance, which the supplier calls poor"
identity:
formula: "Al balance; 3.7 to 4.3 Cu, 0.8 to 1.2 Li, 0.25 to 0.8 Mg, 0.25 to 0.6 Ag, 0.04 to 0.18 Zr (wt%)"
source: msonline-2195
where: "Chemical composition table (Metal Suppliers Online, Aluminum 2195-T8 page)"
tags:
environments: []
stresses: [extreme-cold]
applications: [propulsion-and-tanks, structures, cryogenic-fuel]
properties:
- benchmark: density
label: Density, as printed by a metals supplier
value: 0.096
unit: lb/in3
scope: material
conditions: {form: "2195-T8, plate and sheet", temperature: "not stated"}
method: Physical properties table, as printed
status: ground
source: msonline-2195
where: "Physical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: density
label: Density, as printed by a second supplier
value: 2.72
unit: g/cm3
scope: material
conditions: {form: "2195 alloy, no temper stated"}
method: Datasheet value, as printed
status: ground
note: The two supplier pages do not agree on density (see the lb/in3 entry above). Use a certified specification for design.
source: samat-2195
where: "Physical properties (Stanford Advanced Materials, 2195 Aluminum Lithium Alloy page)"
- benchmark: elastic_modulus
label: Modulus of elasticity, imperial units
value: 11
unit: MSI
scope: material
conditions: {form: "2195-T8, plate and sheet"}
method: Physical properties table, as printed
status: ground
source: msonline-2195
where: "Physical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: elastic_modulus
label: Elastic modulus, metric units
value: 75
unit: GPa
scope: material
conditions: {form: "2195 alloy, no temper stated"}
method: Datasheet value, as printed
status: ground
source: samat-2195
where: "Physical properties (Stanford Advanced Materials, 2195 Aluminum Lithium Alloy page)"
- benchmark: melting_point
label: Melting point (single value listed)
value: 1020
unit: degF
scope: material
conditions: {form: "2195-T8"}
method: Physical properties table, as printed; the page gives one value, not a range
status: ground
source: msonline-2195
where: "Physical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: ultimate_tensile_strength
label: Tensile strength, T8 temper at 70 degF (listed)
value: 80
unit: ksi
scope: material
conditions: {temper: "T8", form: "plate and sheet", temperature: "70 degF"}
method: Mechanical properties table, as printed
status: ground
source: msonline-2195
where: "Mechanical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: yield_strength
label: Yield strength, T8 temper at 70 degF (listed)
value: 74
unit: ksi
scope: material
conditions: {temper: "T8", form: "plate and sheet", temperature: "70 degF"}
method: Mechanical properties table, as printed
status: ground
source: msonline-2195
where: "Mechanical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: elongation
value: 8
unit: "%"
scope: material
conditions: {temper: "T8", form: "plate and sheet", temperature: "70 degF"}
method: Mechanical properties table, as printed
status: ground
source: msonline-2195
where: "Mechanical properties table (Metal Suppliers Online, Aluminum 2195-T8)"
- benchmark: ultimate_tensile_strength
label: Tensile strength, T8 minimum
value: 560
bound: lower
unit: MPa
scope: material
conditions: {temper: "T8", basis: "minimum (Rm)"}
method: Minimum value as printed on a datasheet page; vendor page, not a standard
status: ground
source: samat-2195
where: "T8 mechanical minimums (Stanford Advanced Materials, 2195 page)"
- benchmark: yield_strength
label: Yield strength, T8 minimum (Rp0.2)
value: 500
bound: lower
unit: MPa
scope: material
conditions: {temper: "T8", basis: "minimum (Rp0.2)"}
method: Minimum value as printed on a datasheet page; vendor page, not a standard
status: ground
source: samat-2195
where: "T8 mechanical minimums (Stanford Advanced Materials, 2195 page)"
- benchmark: elongation
label: Elongation, T8 minimum
value: 6
bound: lower
unit: "%"
scope: material
conditions: {temper: "T8", basis: "minimum (A)"}
method: Minimum value as printed on a datasheet page; vendor page, not a standard
status: ground
source: samat-2195
where: "T8 mechanical minimums (Stanford Advanced Materials, 2195 page)"
- benchmark: ultimate_tensile_strength
label: Friction stir weld, room temperature, average Ftu
value: 58.7
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. plate-to-plate friction stir weld", temperature: "room temperature", n: 178, basis: "average"}
method: Average of tensile tests as printed in Table 1
status: ground
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P 0.32 in., RT Ftu"
- benchmark: yield_strength
label: Friction stir weld, room temperature, average Fty
value: 36.6
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. plate-to-plate friction stir weld", temperature: "room temperature", n: 178, basis: "average"}
method: Average of tensile tests as printed in Table 1
status: ground
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P 0.32 in., RT Fty"
- benchmark: ultimate_tensile_strength
label: Friction stir weld, cryogenic (-423 degF), average Ftu
value: 95.5
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. plate-to-plate friction stir weld", temperature: "-423 degF", n: 149, basis: "average"}
method: Average of cryogenic tensile tests as printed in Table 1
status: ground
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P 0.32 in., CRYO Ftu"
- benchmark: yield_strength
label: Friction stir weld, cryogenic (-423 degF), average Fty
value: 60.0
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. plate-to-plate friction stir weld", temperature: "-423 degF", n: 149, basis: "average"}
method: Average of cryogenic tensile tests as printed in Table 1
status: ground
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P 0.32 in., CRYO Fty"
- benchmark: ultimate_tensile_strength
label: Fusion weld, room temperature, Ftu (comparison)
value: 44
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. fusion weld", temperature: "room temperature", n: 1}
method: Single result as printed in Table 1 (no yield value given)
status: ground
note: Only one fusion-weld specimen is listed in the table; treat it as indicative.
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P Fusion, RT Ftu"
- benchmark: ultimate_tensile_strength
label: Fusion weld, cryogenic (-423 degF), Ftu (comparison)
value: 58
unit: ksi
scope: material
conditions: {product: "2195-T8 plate, 0.32 in. fusion weld", temperature: "-423 degF", n: 1}
method: Single result as printed in Table 1 (no yield value given)
status: ground
note: Only one fusion-weld specimen is listed in the table; treat it as indicative.
source: nasa-ftn-1999
where: "Table 1, FSW Average Tensile Properties, row 2195P Fusion, CRYO Ftu"
- benchmark: cryogenic_strength_enhancement
label: Cryogenic strength enhancement factor, friction stir weld
value: 1.6
unit: ratio
scope: material
conditions: {basis: "ratio of cryogenic to room-temperature strength for the 0.32 in. FSW plate, as stated in the report"}
method: Factor stated in the report text
status: ground
source: nasa-ftn-1999
where: "Results, FSW 0.320 in. plate-to-plate (Figure and text), and Summary"
corrosion:
- environment: "Sodium chloride solution (3.5 per cent NaCl) with a scanning reference electrode"
headline: "Friction stir welds of 2195 resist pitting better than the fusion-welded (VPPA) joints in the same test."
effect: "NASA Marshall measured local surface potentials on 2195 welds. The paper reports that anodic regions sit at the edges of both weld types, and that corrosion and pitting occur at the edges of the fusion welds. The potential needed to reach the minimum detectable signal was 200 mV for the VPPA weld and 600 mV for the friction stir weld, which the authors read as the friction stir weld being less subject to corrosion. The study uses a micro-galvanic method, not a corrosion-rate test."
rating: moderate
conditions: {electrolyte: "3.5 per cent NaCl solution", method: "scanning reference electrode technique, 2195 unwelded, VPPA-welded and friction stir welded", exposure: "not a long-term immersion test"}
source: nasa-sret-1998
where: "Potential maps and results, Figures 2 to 7 and surrounding text"
- environment: "General service, as described by a metals supplier"
headline: "The supplier calls 2195 poorly corrosion resistant, because its high alloying pushes it toward strength."
effect: "Metal Suppliers Online states that the alloy has bad workability and poor corrosion resistance, and that being highly alloyed it tends to fall on the higher-strength and lower-corrosion-resistance side. It gives no test data. Treat this as a qualitative warning for design, backed by the NASA pitting results above."
rating: moderate
conditions: {basis: "qualitative statement in a general encyclopedia article; no test conditions"}
source: wiki-2195
where: "Article text on properties (Wikipedia, 2195 aluminium alloy)"
risks:
hazards:
- text: "PubChem aggregated GHS for aluminium metal (CID 5359268; 4079 company reports): H228 flammable solid (60.6%); H250 catches fire spontaneously if exposed to air (34.2%); H261 in contact with water releases flammable gas (90.8%). Signal word Danger. The record does not state the physical form, so treat these as relevant to fine powder, flake and swarf."
ghs: [H228, H250, H261]
source: pubchem-al-li
where: Safety and Hazards, GHS Classification (CID 5359268)
- text: "PubChem aggregated GHS for lithium metal (CID 3028194; 549 company reports): H260 in contact with water releases flammable gases which may ignite spontaneously (100%); H314 causes severe skin burns and eye damage (100%); H318 causes serious eye damage (20.8%). Signal word Danger."
ghs: [H260, H314, H318]
source: pubchem-al-li
where: Safety and Hazards, GHS Classification (CID 3028194)
- text: "Fire: aluminium and lithium are both listed as reacting with water to give flammable gas, and lithium can ignite spontaneously in contact with water. Machining swarf and dust therefore need dry, Class D or metal-fire handling. No machining or fume exposure limit was read for the alloy."
ghs: []
source: pubchem-al-li
where: GHS entries for CID 5359268 and CID 3028194 (H261 and H260 rows)
failure_risks:
- mode: Hot cracking in fusion welds
trigger: "Fusion welding (automatic plasma arc welding) of 2195 during Space Shuttle External Tank manufacture"
consequence: "NASA reports that 2195 is more susceptible to hot cracking during fusion welding than 2219, so it needs more repairs, and the repairs leave reduced weld properties. This led MSFC to start friction stir welding for 2195 in 1997."
severity: moderate
source: nasa-fsw-dev-2002
where: "External Tank section of the MSFC friction stir welding development paper"
- mode: Pitting at weld edges
trigger: "Exposure of fusion-welded 2195 to chloride solution in a micro-galvanic test"
consequence: "Anodic zones at the weld edges corroded and pitted in the test, and the VPPA weld needed a much lower potential to reach the detection level than the friction stir weld."
severity: moderate
source: nasa-sret-1998
where: "Discussion of potential maps for VPPA and friction stir welds"
side_effects: []
handling:
- text: "Friction stir welds of 0.32 inch plate averaged 58.7 ksi at room temperature, against 44 ksi for the fusion weld listed. NASA reports room-temperature and cryogenic FSW repair welds exceeding the minimum design strength, though with an allowable roughly 5 ksi lower at -423 degF than the initial weld."
source: nasa-repair-2008
where: "Summary and Tensile testing sections"
mitigations:
- text: "Friction stir welding replaces fusion welding for 2195 joints, and the report records that repaired FSW joints still met design minimums at both temperatures."
source: nasa-repair-2008
where: "Results, FSW restart and reweld repair allowables"
uses:
- application: structures
device: "Launch Vehicle Stage Adapter (LVSA) for the Space Launch System"
example: "The LVSA, which connects the initial version of the core stage to the upper stage, consists of 16 aluminium-lithium 2195 alloy panels (Boeing)."
source: boeing-sls
where: "LVSA description on the Boeing SLS launch vehicle page"
- application: propulsion-and-tanks
device: "Space Shuttle Super Lightweight External Tank"
example: "The External Tank of the Space Transportation System is made of 2195 aluminium-lithium and 2219 aluminium alloys, joined by automatic plasma arc welding. The Super Lightweight Tank used 2195 in place of 2219 at several locations on the liquid oxygen and liquid hydrogen tanks (Space Safety Magazine)."
source: nasa-fsw-dev-2002
where: "External Tank section of the MSFC friction stir welding development paper; second sentence from the Space Safety Magazine article on the SLWT"
- application: propulsion-and-tanks
device: "Falcon 9 propellant tanks (as reported by Wikipedia)"
example: "Wikipedia states that 2195 is used for the propellant tanks of the Falcon 9 Full Thrust orbital launcher. The claim is not checked against a SpaceX source."
source: wiki-2195
where: "Applications section (Wikipedia, 2195 aluminium alloy)"
supply:
- subject: Aluminium (primary smelter production, the main metal of the alloy)
producers:
- {country: China, share_percent: 60.8, year: 2025}
- {country: Russia, share_percent: 5.3, year: 2025}
- {country: India, share_percent: 5.7, year: 2025}
- {country: Canada, share_percent: 4.5, year: 2025}
critical_lists: []
recycling: "USGS aluminum chapter describes secondary production from old and new scrap, which decreased slightly in 2025 in the United States."
substitutes: ["USGS: composites can substitute for aluminum in aircraft fuselages and wings, and copper can replace aluminum in electrical and heat-exchange applications."]
source: usgs-mcs2026-aluminum
where: "World Smelter Production and Capacity table, 2025e; world total 74,000 thousand t; shares calculated by Space Mushroom against that total; recycling and substitutes sections"
- subject: Bauxite (aluminium feedstock)
abundance: "USGS: global bauxite resources are estimated at 55 billion to 75 billion tons, sufficient to meet world aluminium demand well into the future."
producers: []
critical_lists: []
recycling: ""
substitutes: []
source: usgs-mcs2026-aluminum
where: "World Resources paragraph of the aluminum chapter (refers to the Bauxite and Alumina chapter for production)"
- subject: Lithium
abundance: "20 ppm in the Earth's crust (USGS table of crustal abundances, citing Jefferson Science Associates, 2014)"
producers:
- {country: Australia, share_percent: 31.7, year: 2025}
- {country: China, share_percent: 21.4, year: 2025}
- {country: Chile, share_percent: 19.3, year: 2025}
- {country: Zimbabwe, share_percent: 9.7, year: 2025}
- {country: Argentina, share_percent: 7.9, year: 2025}
critical_lists:
- {list: "USGS 2025 List of Critical Minerals", listed: true}
- {list: "EU critical raw materials list (Regulation (EU) 2024/1252)", listed: true}
recycling: "USGS: construction of lithium battery recycling plants continued throughout 2025."
substitutes: []
source: usgs-mcs2026-lithium
where: "World Mine Production and Reserves table, 2025 (world total 290,000 t, rounded; shares calculated by Space Mushroom). Critical lists: the USGS and European Commission pages."
media: []
documents:
- {title: "Metal Suppliers Online: Aluminum 2195-T8 (composition, physical and mechanical properties)", type: datasheet, url: "https://www.metalsuppliersonline.com/browse/aluminum/2195-t8", year: 2026}
- {title: "Stanford Advanced Materials: 2195 Aluminum Lithium Alloy (composition, properties, T8 minimums)", type: datasheet, url: "https://www.samaterials.com/aluminium/1774-2195-aluminum-lithium-alloy.html", year: 2026}
- {title: "NASA Technical Reports Server 19990064489: Friction Stir Welds in A12195-T8 (Lockheed Martin Michoud study for NASA)", type: report, url: "https://ntrs.nasa.gov/citations/19990064489", year: 1999}
- {title: "NASA Technical Reports Server 20020015869: Friction Stir Welding Development at NASA Marshall Space Flight Center", type: report, url: "https://ntrs.nasa.gov/api/citations/20020015869/downloads/20020015869.pdf", year: 2002}
- {title: "NASA Technical Reports Server 20080036249: Friction stir weld restart and reweld repair allowables", type: report, url: "https://ntrs.nasa.gov/citations/20080036249", year: 2008}
- {title: "NASA Technical Reports Server 19980046577: A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique", type: report, url: "https://ntrs.nasa.gov/citations/19980046577", year: 1998}
- {title: "USGS Mineral Commodity Summaries 2026: Aluminum", type: report, url: "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf", year: 2026}
- {title: "USGS Mineral Commodity Summaries 2026: Lithium", type: report, url: "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf", year: 2026}
- {title: "PubChem: aluminium metal (CID 5359268) and lithium metal (CID 3028194), GHS", type: database, url: "https://pubchem.ncbi.nlm.nih.gov/compound/5359268", year: 2026}
gaps:
- "PubChem GHS was read for aluminium and lithium metal, not for the alloy itself. No alloy SDS, machining-dust exposure limit or fume data was read, so dust and swarf hazards are only partly sourced."
- "The user brief lists SLS as a user of 2195. The SLS core-stage tanks are 2219 (Space Safety Magazine, 2013). The only SLS use of 2195 found is the Launch Vehicle Stage Adapter panels (Boeing). A NASA report proposing 2195 gores for the core stage domes (NTRS 20160008018) was not opened."
- "Falcon 9 tank use rests on Wikipedia alone; no SpaceX source was opened."
- "No cryogenic base-metal (non-welded) tensile data was read. The cryogenic values are for friction stir welds only."
- "Elongation and yield at -423 degF for the friction stir weld were not listed in the report's table as printed."
- "Tensile and yield values from two vendor pages do not match each other in every case (for example, the Stanford minimums are in MPa, the Metal Suppliers Online values in ksi). Only the printed values are used."
- "Zirconium range differs between sources: 0.04 to 0.18 wt% (Metal Suppliers Online) and 0.08 to 0.16 wt% (Stanford). The profile uses the Metal Suppliers Online range."
- "No USGS or EU critical-mineral listing was checked for aluminium or copper, so critical_lists for the aluminium entry is empty."
- "The fatigue crack growth report (NTRS 20000052923) was located but its tables were not read in this run."
- "Density and modulus disagree between the two vendor datasheets; a certified specification such as AMS 4474 was not found in this run."
sources:
msonline-2195:
title: "Aluminum 2195-T8: composition, physical and mechanical properties"
id: "Metal Suppliers Online, aluminum/2195-t8"
url: https://www.metalsuppliersonline.com/browse/aluminum/2195-t8
year: 2026
kind: datasheet
license: "supplier page, cited not reproduced"
samat-2195:
title: "2195 Aluminum Lithium Alloy (composition, density, modulus, T8 minimums)"
id: "Stanford Advanced Materials, product 1774"
url: https://www.samaterials.com/aluminium/1774-2195-aluminum-lithium-alloy.html
year: 2026
kind: datasheet
license: "supplier page, cited not reproduced"
wiki-2195:
title: 2195 aluminium alloy
id: "Wikipedia, 2195 aluminium alloy"
url: https://en.wikipedia.org/wiki/2195_aluminium_alloy
year: 2026
kind: web
license: CC BY-SA 4.0
nasa-ftn-1999:
title: "Friction Stir Welds in A12195-T8 (Lockheed Martin Michoud study for NASA)"
id: "NTRS 19990064489"
url: https://ntrs.nasa.gov/citations/19990064489
year: 1999
kind: report
license: public domain (NASA)
nasa-fsw-dev-2002:
title: "Friction Stir Welding Development at NASA Marshall Space Flight Center"
id: "NTRS 20020015869"
url: https://ntrs.nasa.gov/api/citations/20020015869/downloads/20020015869.pdf
year: 2002
kind: report
license: public domain (NASA)
nasa-repair-2008:
title: Friction stir weld restart and reweld repair allowables
id: "NTRS 20080036249"
url: https://ntrs.nasa.gov/citations/20080036249
year: 2008
kind: report
license: public domain (NASA)
nasa-sret-1998:
title: "A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique"
id: "NTRS 19980046577"
url: https://ntrs.nasa.gov/citations/19980046577
year: 1998
kind: report
license: public domain (NASA)
boeing-sls:
title: "Boeing: SLS rocket components (Launch Vehicle Stage Adapter and core stage)"
id: "Boeing SLS launch vehicle page"
url: https://www.boeing.com/space/space-launch-system/launch/rocket.html
year: 2026
kind: web
license: "company web page, cited not reproduced"
spacesafety-sls:
title: "SLS external tank reverts to hard alloy (Space Safety Magazine)"
id: "Space Safety Magazine, 18 March 2013"
url: https://www.spacesafetymagazine.com/aerospace-engineering/rocketry/sls-external-tank-reverts-hard-alloy/
year: 2013
kind: web
license: "magazine web page, cited not reproduced"
usgs-mcs2026-aluminum:
title: "Mineral Commodity Summaries 2026: Aluminum"
id: "USGS MCS 2026, February 2026"
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-mcs2026-lithium:
title: "Mineral Commodity Summaries 2026: Lithium"
id: "USGS MCS 2026, February 2026"
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-crit2025:
title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
id: "Final 2025 List of Critical Minerals, November 2025"
url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
year: 2025
kind: web
license: public domain (USGS)
ec-crm:
title: Critical raw materials (European Commission, list under Regulation (EU) 2024/1252)
id: "Regulation (EU) 2024/1252"
url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
year: 2024
kind: web
license: European Commission web page
pubchem-al-li:
title: "PubChem GHS classification for aluminium metal and lithium metal"
id: "PubChem CID 5359268 (Aluminum) and CID 3028194 (Lithium), read via the PUG REST API"
url: https://pubchem.ncbi.nlm.nih.gov/compound/5359268
kind: database
license: "PubChem, cited not reproduced"
license: CC-BY-4.0
updated: "2026-10-19"
review:
status: draft
method: assistant
checked_values: 18
unreachable: 0
caveats: 3
note: "Read by an AI assistant on 2026-10-19 from the cited pages and NASA PDFs (text extracted with pdftotext). Composition ranges from Metal Suppliers Online, with a Zr conflict noted. Density and modulus conflict between two vendor pages. SLS core-stage tanks are 2219, not 2195; only the LVSA is 2195 per Boeing."
story:
recipe:
line: "Alloy 2195 is an aluminium-copper-lithium alloy. Aluminium makes up the balance. Copper and lithium are the main alloying additions, with smaller additions of magnesium, silver and zirconium, as ranges given by Metal Suppliers Online."
parts:
- name: Aluminium
symbol: Al
share_note: balance (the rest)
role: The matrix of the alloy.
- name: Copper
symbol: Cu
share_percent: 3.7
share_high: 4.3
role: Main alloying addition listed in the supplier's composition table.
- name: Lithium
symbol: Li
share_percent: 0.8
share_high: 1.2
role: Main lithium addition, the element that gives the alloy its name.
- name: Magnesium
symbol: Mg
share_percent: 0.25
share_high: 0.8
role: Minor addition listed in the composition table.
- name: Silver
symbol: Ag
share_percent: 0.25
share_high: 0.6
role: Minor addition listed in the composition table.
- name: Zirconium
symbol: Zr
share_percent: 0.04
share_high: 0.18
role: Minor addition listed in the composition table. Stanford Advanced Materials gives 0.08 to 0.16 wt%.
risk_groups:
- title: For people
level: 0
verdict: "No hazard classification found"
lead: "No safety data sheet for the alloy was opened in this run, so this section is limited to what the sources say about handling the welded product."
points:
- label: Welding
line: "Friction stir welding is the route NASA chose for this alloy because fusion welds hot-crack and need repairs."
- label: Fumes and dust
line: "No fume or dust data for the alloy were read. Treat machining swarf with the care given to any aluminium-lithium material until a safety data sheet is checked."
- title: If a joint fails or corrodes
lead: "These results are from laboratory and design tests, not from flight failures."
points:
- label: Fusion welds
line: "NASA reports that fusion welds of 2195 hot-crack and need more repairs. The repairs leave reduced properties, which is why the External Tank programme moved to friction stir welding."
- label: Pitting
line: "In a chloride test, the fusion-welded joints pitted at their edges, and a higher potential was needed to reach the detection level for friction stir welds."
- title: Handling and storage
points:
- label: Repair welds
line: "NASA's repair study found room-temperature and cryogenic FSW repair welds met the minimum design strength, with an allowable about 5 ksi lower at -423 degF than the initial weld."
why: >-
Alloy 2195 was used to save mass in large cryogenic tanks. Wikipedia describes it as stronger and less dense than 2219. It was adopted for the Space Shuttle Super Lightweight External Tank, where it replaced 2219 in
several locations. Its drawback is that it hot-cracks in fusion welds, which led NASA Marshall to develop friction stir
welding for it from 1997 onward.
uses:
- where: Space Shuttle External Tank
line: >-
The External Tank was made of 2195 and 2219 aluminium alloys, joined by automatic plasma arc welding. The Super
Lightweight Tank then used 2195 at several locations on the liquid oxygen and liquid hydrogen tanks.
- where: Space Launch System
line: >-
The Launch Vehicle Stage Adapter, which connects the initial core stage to the upper stage, consists of 16 panels of
2195. The SLS core-stage tanks are 2219, not 2195, according to a 2013 magazine report.
- where: Falcon 9
line: >-
Wikipedia says 2195 is used for the propellant tanks of the Falcon 9. This was not checked against a SpaceX source.
can_do:
- label: Strength at room temperature
benchmark: ultimate_tensile_strength
value: 80 ksi
line: >-
The T8 temper is listed at 80 ksi ultimate tensile strength and 74 ksi yield at 70 degF. Friction stir welds of the
0.32 inch plate averaged 58.7 ksi at room temperature.
- label: Strength at -423 degF
benchmark: ultimate_tensile_strength
value: 95.5 ksi
line: >-
Friction stir welds averaged 95.5 ksi ultimate tensile strength at -423 degF, a factor of 1.6 over room temperature
as the report states. The fusion weld of the same plate reached 58 ksi at that temperature.
- label: Stiffness
benchmark: elastic_modulus
value: 75 GPa
line: >-
The modulus is 75 GPa on one datasheet and 11 MSI on the other. Neither gives a temper for the value.
- label: Density
benchmark: density
value: 2.72 g/cm3
line: >-
One datasheet gives 2.72 g/cm3. The other gives 0.096 lb/in3. The two do not agree, so use a certified specification.
compare: >-
Alloy 2195 is a lighter, stronger alternative to 2219 for the cryogenic tank application that NASA chose it for. It has
a high alloying content, which gives it strength but poor corrosion resistance, according to the supplier. Its welded
strength depends heavily on the welding process: friction stir welds keep much more strength than fusion welds of the
same plate.
compare_rows:
- {label: Ultimate tensile strength (T8), benchmark: ultimate_tensile_strength}
- {label: Yield strength (T8), benchmark: yield_strength}
- {label: Density, benchmark: density}
handling:
- "Weld the alloy by friction stir welding where possible. Fusion welds hot-crack and need repair."
- "Expect cryogenic strength to be higher than room-temperature strength for welded plate."
- "Use a certified specification for density and modulus, because the vendor sources differ."
good_for:
- "Cryogenic tanks where weld strength at -423 degF matters. Friction stir welds averaged 95.5 ksi there."
- "Structures that need a low density and high stiffness, such as the Launch Vehicle Stage Adapter panels."
watch_out:
- "Fusion welding hot-cracks this alloy and leads to repairs with lower properties."
- "Corrosion resistance is poor according to the supplier, and welded joints pit at their edges in chloride tests."
- "Vendor composition and property pages disagree on some values, so check a certified specification."
verdict: "Alloy 2195 is a good cryogenic tank alloy when it is friction stir welded. Its low weld tolerance and weak corrosion resistance mean the weld process and protective finishes need to be specified."
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.