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."