spore: profile
id: aluminium-5251
spore_version: 0.2
family: aluminium-alloys
name: Aluminium alloy 5251
abbreviation: AlMg2
role: marine and sheet-metal structural alloy
category: metals
type: aluminium
summary: |
  Aluminium alloy 5251 (EN AW-5251, AlMg2Mn0.3) is a non-heat-treatable wrought aluminium-magnesium alloy with 1.70 to 2.40 wt% magnesium. Its density is 2.69 g/cm3 in the Aalco H22 datasheet. Cold work sets the H tempers: H22 has a minimum proof stress of 120 MPa and a tensile strength of 190 to 230 MPa, and H24 has 140 MPa and 210 to 250 MPa. Datasheets rate its corrosion resistance in marine air highly and call it readily weldable. Suppliers list it for boats, panelling and aircraft fuel tanks, and one supplier claims use in satellite shells.
best_for: Welded marine and sheet-metal structures where seawater corrosion resistance and weldability matter more than peak strength, at 2.69 g/cm3
weakest_at: 'Strength compared with heat-treatable alloys: H22 minimum proof stress is 120 MPa, and a good weld reaches only about 160 MPa (Smith)'
identity:
  formula: AlMg2Mn0.3 (aluminium with 1.70 to 2.40 wt% Mg, 0.10 to 0.50 wt% Mn, up to 0.50 wt% Fe, up to 0.40 wt% Si, balance Al; limits as printed to BS EN 573-3 in the Aalco H22 datasheet)
  source: aalco-5251-h22
  where: Chemical composition table (BS EN573-3:2009), rows Magnesium, Manganese, Iron and Silicon. The AlMg2Mn0.3 name is printed on the Modulus Metal page under the DIN 1725-1 entry.
  designations:
    - system: UNS
      code: A95251
      source: modulus-5251
      where: Designation table, UNS number row
    - system: EN
      code: '3.3525'
      source: modulus-5251
      where: Designation table, EN number row
    - system: EN name
      code: EN AW-5251
      source: modulus-5251
      where: Designation table, EN name row (EN AW-5251 (EN AW-Al Mg2))
    - system: DIN
      code: AlMg2Mn0.3
      source: modulus-5251
      where: Other designations list, Germany line (3.3525/AlMg2Mn0.3 to DIN 1725-1)
    - system: ISO
      code: AlMg2
      source: modulus-5251
      where: Other designations list, International line (AlMg2 to ISO 209-1)
    - system: BS
      code: NS4
      note: former British Standard designation; Smith says the previous BS specification was known as NS4 H3
      source: smith-5251
      where: Title line 5251 (NS4) and Technical Description
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - propulsion-and-tanks
    - thermal-control
properties:
  - benchmark: density
    label: Density, alloy 5251 (sheet and plate, H22 datasheet)
    value: 2.69
    unit: g/cm3
    scope: material
    conditions:
      grade: 5251 (AlMg2)
      temperature: not stated
      form: sheet and plate (H22 datasheet)
    method: Value printed in a stockholder datasheet, Physical Properties section
    status: ground
    source: aalco-5251-h22
    where: Physical Properties table, row Density
  - benchmark: density
    label: Density, alloy 5251 (typical values)
    value: 2680
    unit: kg/m3
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
      basis: typical values, as printed
    method: Typical value printed in a datasheet, Physical Properties (Typical values) table
    status: ground
    source: atlas-5251
    where: Physical Properties (Typical values) table, column Density (kg/m3), row 5251
  - benchmark: melting_point
    label: Melting range (solidus to liquidus), alloy 5251
    value: 605
    value_high: 650
    bound: range
    unit: °C
    scope: material
    conditions:
      grade: '5251'
      pressure: not stated
      note_on_form: solidification temperature and melting temperature as printed
    method: Solidus and liquidus printed as separate values in a datasheet
    status: ground
    source: euralliage-5251
    where: Table 2, Solidification temperature T_sol 605 and Melting temperature T_liq 650
  - benchmark: elastic_modulus
    label: Modulus of elasticity, alloy 5251
    value: 70
    unit: GPa
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
    method: Value printed in a stockholder datasheet, Physical Properties section
    status: ground
    source: aalco-5251-h22
    where: Physical Properties table, row Modulus of Elasticity
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 25 °C, alloy 5251 (typical values)
    value: 138
    unit: W/(m·K)
    scope: material
    conditions:
      grade: '5251'
      temperature: 25 °C
      basis: typical values, as printed
    method: Typical value printed in a datasheet
    status: ground
    note: Smith prints 149 W/m.K and Euralliage prints 149 W m-1 K-1 with no temperature, and Aalco prints 134 W/m.K with no temperature. The datasheets do not agree, so the rows are kept separate.
    source: atlas-5251
    where: Physical Properties (Typical values) table, column Thermal Conductivity at 25 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, alloy 5251 (Smith typical values)
    value: 149
    unit: W/(m·K)
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
      basis: typical values, as printed
    method: Typical value printed in a datasheet, Typical Mechanical Properties table
    status: ground
    source: smith-5251
    where: Typical Mechanical Properties table, row Thermal conductivity W/m.K
  - benchmark: cte
    label: Mean coefficient of thermal expansion, 20 to 100 °C, alloy 5251
    value: 23.8
    unit: µm/m/°C
    scope: material
    conditions:
      grade: '5251'
      temperature_range: 20 to 100 °C
      basis: typical values, as printed
    method: Typical value printed in a datasheet
    status: ground
    source: atlas-5251
    where: Physical Properties (Typical values) table, column Mean Coefficient of Thermal Expansion 20-100°C
  - benchmark: specific_heat
    label: Specific heat capacity, alloy 5251
    value: 898
    unit: J/(kg·K)
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
      unit_in_source: J kg⁻¹ K⁻¹
    method: Value printed in a datasheet, Table 2 physical and elastic properties
    status: ground
    source: euralliage-5251
    where: Table 2, row Specific heat C_p
  - benchmark: electrical_resistivity
    label: Electrical resistivity, alloy 5251 (typical values)
    value: 50
    unit: nΩ·m
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
      basis: typical values, as printed
    method: Typical value printed in a datasheet
    status: ground
    source: atlas-5251
    where: Physical Properties (Typical values) table, column Electrical Resistivity (nΩ.m)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, alloy 5251 (% IACS)
    value: 39.4
    unit: '% IACS'
    scope: material
    conditions:
      grade: '5251'
      temperature: not stated
    method: Value printed in a datasheet, Typical Mechanical Properties table
    status: ground
    note: Electrical conductivity is not a canonical property name, so it is entered under its own name. Euralliage prints 37.5 %IACS, which is not entered as a separate row.
    source: smith-5251
    where: Typical Mechanical Properties table, row Electrical conductivity % IACS
  - benchmark: yield_strength
    label: Yield strength Rp0.2 minimum, H22 temper
    value: 120
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H22
      thickness: 0.2 to 25 mm
      standard: BS EN 485-2:2008
      measure: proof stress, minimum
      product_form: sheet and plate
    method: Minimum value printed in a stockholder datasheet that quotes the standard
    status: ground
    source: aalco-5251-h22
    where: Mechanical Properties table, row H22, column Proof Stress
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, H22 temper
    value: 190
    value_high: 230
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H22
      thickness: 0.2 to 25 mm
      standard: BS EN 485-2:2008
      product_form: sheet and plate
    method: Range printed in a stockholder datasheet that quotes the standard
    status: ground
    source: aalco-5251-h22
    where: Mechanical Properties table, row H22, column Tensile Strength
  - benchmark: yield_strength
    label: Yield strength Rp0.2 minimum, H24 temper
    value: 140
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H24
      thickness: 0.2 to 12.5 mm
      standard: BS EN 485-2:2008
      measure: proof stress, minimum
      product_form: sheet and plate
    method: Minimum value printed in a stockholder datasheet that quotes the standard
    status: ground
    source: aalco-5251-h24
    where: Mechanical Properties table, row H24, column Proof Stress
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, H24 temper
    value: 210
    value_high: 250
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H24
      thickness: 0.2 to 12.5 mm
      standard: BS EN 485-2:2008
      product_form: sheet and plate
    method: Range printed in a stockholder datasheet that quotes the standard
    status: ground
    source: aalco-5251-h24
    where: Mechanical Properties table, row H24, column Tensile Strength
  - benchmark: yield_strength
    label: Yield strength Rp0.2 minimum, O (annealed) temper
    value: 60
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: O (soft)
      thickness: 0.2 to 50 mm
      standard: BS EN 485-2:2008
      measure: proof stress, minimum
      product_form: sheet and plate
    method: Minimum value printed in an online article that tabulates BS EN 485-2 values by temper
    status: ground
    source: azom-5251
    where: Mechanical Properties by Temper table, row O (soft), column Proof Stress
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, O (annealed) temper
    value: 160
    value_high: 200
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: O (soft)
      thickness: 0.2 to 50 mm
      standard: BS EN 485-2:2008
      product_form: sheet and plate
    method: Range printed in an online article that tabulates BS EN 485-2 values by temper
    status: ground
    source: azom-5251
    where: Mechanical Properties by Temper table, row O (soft), column Tensile Strength
  - benchmark: elongation
    label: Elongation A minimum, H22/H32 temper (range by thickness)
    value: 4
    value_high: 12
    bound: range
    unit: '%'
    scope: material
    conditions:
      grade: '5251'
      temper: H22/H32
      thickness: 0.2 to 25.0 mm
      standard: EN 485-2 (as printed in table)
    method: Minimum elongation printed as a range by thickness in a datasheet
    status: ground
    source: euralliage-5251
    where: Table 3, Sheets (EN 485-2), row H22/H32, column A % min
  - benchmark: elongation
    label: Elongation A minimum, O/H111 temper (range by thickness)
    value: 13
    value_high: 18
    bound: range
    unit: '%'
    scope: material
    conditions:
      grade: '5251'
      temper: O/H111
      thickness: 0.2 to 12.5 mm
      standard: EN 485-2 (as printed in table)
    method: Minimum elongation printed as a range by thickness in a datasheet
    status: ground
    source: euralliage-5251
    where: Table 3, Sheets (EN 485-2), row O/H111, column A % min
  - benchmark: yield_strength
    label: Yield strength Rp0.2 minimum, H34 temper (AS/NZS 1734)
    value: 180
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H34
      standard: AS/NZS 1734 (Australia and New Zealand flat-rolled specification)
      measure: 0.2% proof, minimum
      product_form: flat rolled product
    method: Minimum value printed in a datasheet that quotes the Australian and New Zealand standard
    status: ground
    note: This is an Australia and New Zealand specification, not BS EN 485-2, so its limits are not interchangeable with the H22 and H24 rows above.
    source: atlas-5251
    where: Mechanical Property Specification table, row 5251-H34, column Yield Strength 0.2% Proof (MPa) min.
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, H34 temper (AS/NZS 1734)
    value: 235
    value_high: 285
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: '5251'
      temper: H34
      standard: AS/NZS 1734
      product_form: flat rolled product
    method: Range printed in a datasheet that quotes the Australian and New Zealand standard
    status: ground
    source: atlas-5251
    where: Mechanical Property Specification table, row 5251-H34, column Tensile Strength (MPa)
corrosion:
  - environment: Marine atmosphere and seawater spray
    headline: 5251 is described as highly corrosion resistant in marine environments.
    effect: Aalco says it has high corrosion resistance particularly in marine environments. Smith says it can be used in normal, industrial and marine environments without problems and is particularly suited to offshore applications. Atlas says it is acceptable in many marine environments.
    rating: low
    conditions:
      basis: datasheet statements; no exposure time, site or test data printed
    source: aalco-5251-h22
    where: Description paragraph (high corrosion resistance particularly in marine environments)
  - environment: Stress corrosion cracking
    headline: Low magnesium content keeps 5251 out of the stress corrosion cracking range of higher-magnesium alloys.
    effect: Atlas says the magnesium content is low enough that 5251 does not suffer from the stress corrosion cracking that can affect alloys with more than about 3.5 % Mg, such as 5083.
    rating: low
    conditions:
      basis: statement in datasheet; no test data printed
      threshold_in_source: more than about 3½ % Mg
    source: atlas-5251
    where: Corrosion Resistance section, first paragraph
  - environment: Industrial, sea and country atmospheres
    headline: Euralliage rates the corrosion indices for 5251 as very good in sea, industrial and country atmospheres.
    effect: Euralliage gives Very good for general corrosion, industrial, sea and country atmosphere corrosion, stress corrosion, exfoliation and intercrystalline corrosion. The page gives ratings only, with no rates or durations.
    rating: low
    conditions:
      basis: qualitative index ratings for information only; no exposure time printed
    source: euralliage-5251
    where: Corrosion (properties, for information only) list
risks:
  hazards:
    - text: 'Kaiser Aluminum SDS for aluminium and its alloys (a generic sheet, not 5251-specific): the product is solid metallic pieces and may form explosive dust/air mixtures if high concentrations of dust are suspended in air. Dust or fumes may irritate the eyes, skin and respiratory tract. The same sheet says the material is considered hazardous under 29 CFR 1910.1200, which conflicts with the Texarkana sheet below.'
      ghs: []
      source: kaiser-al-sds
      where: Section 2 Hazards Identification; Fire and explosion hazards; Component Information
    - text: 'Texarkana Aluminum SDS for 5xxx-series alloys (a family sheet, not 5251-specific): the formed solid as shipped is not hazardous, but processing can generate combustible dust. Signal word Warning, with the hazard statement May form combustible dust concentrations in air during processing and handling. Welding, cutting or processing may release hazardous dust or fumes.'
      ghs: []
      source: tex-5xxx-sds
      where: Section 2 Hazards Identification (signal word and hazard statement); Additional Information; Symptoms and Injuries
  failure_risks:
    - mode: Strength loss in welds of strain-hardened tempers
      trigger: Welding H22 or H24 sheet, with filler 5356 (Aalco) or 5056A or 5154A (Smith)
      consequence: Smith says a good weld is likely to have strength of up to 160 MPa maximum, depending on the welding type and quality. Atlas says welding strain-hardened tempers reduces strength in the heat-affected zone.
      severity: moderate
      source: smith-5251
      where: Welding section
    - mode: Softening by heating cold-worked sheet
      trigger: Heating cold-worked material to about 345 °C
      consequence: Atlas says 5251 can be annealed by heating to 345 °C, holding until the temperature is uniform, then cooling. The cold-work strength is lost. No hold time or property data after heating is printed.
      severity: low
      source: atlas-5251
      where: Heat Treatment section
    - mode: Age softening after cold work
      trigger: Standing at room temperature after cold work, before stabilisation
      consequence: Atlas says the alloy spontaneously age-softens right after cold work until it reaches a stable condition. Mill products are supplied with stable properties, so the effect applies to unstabilised cold-worked stock.
      severity: low
      source: atlas-5251
      where: Heat Treatment section, second paragraph
  side_effects: []
  handling:
    - text: Aalco rates brazability as poor. It recommends filler 5356 for welding 5251 to itself and to 6XXX, 7XXX and most other 5XXX alloys, and 4043 for welding to 5005, 5020, 1XXX or 3XXX alloys.
      source: aalco-5251-h22
      where: Weldability table and filler text
    - text: Atlas says machinability of the softer O and H32 tempers is poor, and that harder tempers such as H34 are somewhat easier to machine.
      source: atlas-5251
      where: Machining section
    - text: Prevent dust accumulation to minimise explosion hazard, and avoid generating dust (Texarkana SDS).
      source: tex-5xxx-sds
      where: Section 2 precautionary statements
  mitigations: []
uses:
  - application: structures
    device: Boats, marine structures, panelling and vehicle panels
    example: Aalco lists boats, panelling and pressings, marine structures, aircraft parts, vehicle panels, furniture tubing, silos and containers as typical uses of 5251. Atlas lists small marine craft (tinnies) as typical applications.
    source: aalco-5251-h22
    where: Typical Uses paragraph; Atlas Typical Applications section
  - application: propulsion-and-tanks
    device: Aircraft fuel tanks and oxygen cylinders (supplier claim)
    example: Chalco says 5251 sheet can be used to manufacture aircraft fuselage shells, fuel tanks and oxygen cylinders. This is a supplier product-page claim, not a qualification standard.
    source: chalco-5251-plate
    where: Stated applications list on the 5251 O/H16/H26 Aerospace Aluminum Sheet page
  - application: structures
    device: Satellite shells and missile structures (supplier claim)
    example: The same Chalco page says 5251 has also been used on spacecraft components such as satellite shells and missile structures. No spacecraft qualification data for 5251 was opened in this run.
    source: chalco-5251-plate
    where: Stated applications list, spacecraft sentence
  - application: thermal-control
    device: Heat transfer devices, pressure vessels and boilers
    example: Smith lists heat transfer devices, pressure vessels, boiler making, chemical industry and pharmaceutical work among typical applications for its 5251 sheet.
    source: smith-5251
    where: Typical Applications list
supply:
  - subject: Primary aluminium smelter production (world, 2025 estimated)
    producers:
      - country: China
        share_percent: 60.8
        year: 2025
      - country: India
        share_percent: 5.7
        year: 2025
      - country: Russia
        share_percent: 5.3
        year: 2025
      - country: Canada
        share_percent: 4.5
        year: 2025
    critical_lists: []
    recycling: 'USGS: in 2025 aluminium recovered from purchased scrap in the United States was about 3.6 million tons, 56 % from new scrap and 44 % from old scrap. Recovery from old scrap was equivalent to about 28 % of apparent consumption.'
    substitutes:
      - 'USGS: composites can substitute for aluminium in aircraft fuselages and wings. Magnesium, steel and titanium can substitute in ground transportation uses. Copper can replace aluminium in electrical and heat-exchange applications.'
    source: usgs-mcs2026-aluminum
    where: 'Smelter production table, column 2025e: China 45,000, India 4,200, Russia 3,900, Canada 3,300, world total 74,000 thousand t. Shares calculated by Space Mushroom from those printed values, not printed by USGS. Recycling paragraph; Substitutes paragraph.'
documents:
  - title: 'Aalco datasheet: Aluminium Alloy 5251 H22 Sheet and Plate (BS EN 573-3, BS EN 485-2)'
    type: datasheet
    url: https://www.aalco.co.uk/datasheets/Aluminium-Alloy-5251-H22-Sheet-and-Plate_150.ashx
  - title: 'Aalco datasheet: Aluminium Alloy 5251 H24 Sheet and Plate'
    type: datasheet
    url: https://www.aalco.co.uk/datasheets/Aluminium-Alloy-5251-H24-Sheet-and-Plate_151.ashx
  - title: 'Modulus Metal: Aluminum 5251 Material Data Sheet'
    type: datasheet
    url: https://www.modulusmetal.com/aluminum-5251-material-data-sheet/
  - title: 'Atlas Steels: Aluminium Alloy 5251 Data Sheet (revised 24/06/2021)'
    type: datasheet
    url: https://atlassteels.com.au/wp-content/uploads/2021/08/Aluminium-Alloy-5251-Data-Sheet-24-06-21.pdf
    year: 2021
  - title: 'Smiths Metal Centres: 5251 (NS4) Technical Datasheet'
    type: datasheet
    url: https://www.smithmetal.com/pdf/aluminium/5xxx/5251.pdf
    year: 2023
  - title: 'Euralliage: 5251 (AW-AlMg2) product datasheet'
    type: datasheet
    url: https://www.euralliage.com/5251_english.htm
  - title: 'AZoM: Aluminium Alloys, Aluminium 5251 Properties, Fabrication and Applications'
    type: database
    url: https://www.azom.com/article.aspx?ArticleID=2805
  - title: 'USGS Mineral Commodity Summaries 2026: Aluminum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
    year: 2026
  - title: 'Chalco: 5251 O/H16/H26 Aerospace Aluminum Sheet (supplier page)'
    type: datasheet
    url: https://www.chalcoaluminum.com/application/aluminum-aerospace/5251-plate/
  - title: Kaiser Aluminum safety data sheet, aluminum and alloys (2017, generic)
    type: sds
    url: https://www.kaiseraluminum.com/files/msds/2017-Aluminum-and-Alloys.pdf
    year: 2017
  - title: Texarkana Aluminum safety data sheet, 5xxx series alloys (Rev 5-14-2020, family sheet)
    type: sds
    url: https://www.texarkanaaluminum.com/PDF/Aluminum%205xxx%20Series%20Alloys%20SDS%20Rev%205-14-2020.pdf
    year: 2020
gaps:
  - No spacecraft qualification data for 5251 (AMS, ECSS or NASA material specification) was found. The satellite and missile use rests on a single supplier page (Chalco), and the fuel-tank and oxygen-cylinder uses are also supplier claims.
  - No NASA outgassing data (total mass loss or collected volatile condensable material), atomic-oxygen erosion yield, radiation effects or cryogenic toughness for 5251 was found or opened.
  - Chalco prints fatigue strengths of 55 to 75 MPa for 5251 tempers. These are not entered, because the table gives no test standard, specimen or stress ratio.
  - PubChem's GHS record for aluminium was blocked by a verification page, and no 5251-specific SDS was found. The hazard entries rest on two generic or family SDS sheets (Kaiser and Texarkana) that disagree on classification of the solid.
  - The USGS aluminum summary read here does not name aluminium on a critical-minerals list, so critical_lists is left empty. The USGS text was read from the 2026 summary; the critical-minerals list itself was not opened.
  - 'Brinell hardness (Aalco H22 56 HB, H24 62 HB; AZoM O 44 HB) is not entered: ''hardness'' is not a canonical property name in this site''s property list.'
  - Smith's typical tensile range (200 to 240 MPa) and minimum yield (130 MPa, approximate only) are not entered, because Smith does not name the temper for those rows and its values differ from the BS EN 485-2 values for H22.
  - Euralliage prints electrical resistivity as 46 nW m, with the ohm sign missing, so that value is not entered. Its electrical conductivity of 37.5 %IACS is also not entered, since Smith's 39.4 %IACS is recorded.
  - Poisson's ratio (0.33, Euralliage) and shear strength (125 N/mm2, Smith) were read but are not entered. Neither is in the property canon as a Smith-supported row for this grade.
  - The AA (Aluminum Association) designation 5251 appears on the Modulus Metal page, but this site does not have an AA system code, so it is not entered. Atlas says 5251 is not in ASTM B209M, so no ASTM code is listed.
  - The casting and rolling route, and the melting practice, are not described in any source opened in this run.
sources:
  aalco-5251-h22:
    title: Aluminium Alloy 5251 H22 Sheet and Plate (Aalco commercial alloy datasheet)
    url: https://www.aalco.co.uk/datasheets/Aluminium-Alloy-5251-H22-Sheet-and-Plate_150.ashx
    kind: datasheet
    license: Stockholder datasheet (cited, not reproduced)
  aalco-5251-h24:
    title: Aluminium Alloy 5251 H24 Sheet and Plate (Aalco commercial alloy datasheet)
    url: https://www.aalco.co.uk/datasheets/Aluminium-Alloy-5251-H24-Sheet-and-Plate_151.ashx
    kind: datasheet
    license: Stockholder datasheet (cited, not reproduced)
  modulus-5251:
    title: Aluminum 5251 Material Data Sheet (Modulus Metal)
    url: https://www.modulusmetal.com/aluminum-5251-material-data-sheet/
    kind: datasheet
    license: Supplier web page (cited, not reproduced)
  atlas-5251:
    title: Aluminium Alloy 5251 Data Sheet (Atlas Steels, revised 24/06/2021)
    url: https://atlassteels.com.au/wp-content/uploads/2021/08/Aluminium-Alloy-5251-Data-Sheet-24-06-21.pdf
    year: 2021
    kind: datasheet
    license: Supplier data sheet (cited, not reproduced)
  smith-5251:
    title: 5251 (NS4) Technical Datasheet (Smiths Metal Centres)
    url: https://www.smithmetal.com/pdf/aluminium/5xxx/5251.pdf
    year: 2023
    kind: datasheet
    license: Supplier data sheet (cited, not reproduced)
  euralliage-5251:
    title: 5251 (AW-AlMg2) product datasheet (Euralliage)
    url: https://www.euralliage.com/5251_english.htm
    kind: datasheet
    license: Supplier web page (cited, not reproduced)
  azom-5251:
    title: 'Aluminium Alloys: Aluminium 5251 Properties, Fabrication and Applications (AZoM)'
    url: https://www.azom.com/article.aspx?ArticleID=2805
    kind: web
    license: Web article (cited, not reproduced)
  usgs-mcs2026-aluminum:
    title: 'Mineral Commodity Summaries 2026: Aluminum (USGS)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  chalco-5251-plate:
    title: 5251 O/H16/H26 Aerospace Aluminum Sheet (Chalco supplier page)
    url: https://www.chalcoaluminum.com/application/aluminum-aerospace/5251-plate/
    kind: web
    license: Supplier web page (cited, not reproduced)
  kaiser-al-sds:
    title: 'Safety Data Sheet: Aluminum and Alloys (Kaiser Aluminum, generic, 2017)'
    url: https://www.kaiseraluminum.com/files/msds/2017-Aluminum-and-Alloys.pdf
    year: 2017
    kind: datasheet
    license: Manufacturer safety data sheet (cited, not reproduced)
  tex-5xxx-sds:
    title: 'Safety Data Sheet: Aluminum 5xxx Series Alloys (Texarkana Aluminum, Rev 5-14-2020, family sheet)'
    url: https://www.texarkanaaluminum.com/PDF/Aluminum%205xxx%20Series%20Alloys%20SDS%20Rev%205-14-2020.pdf
    year: 2020
    kind: datasheet
    license: Manufacturer safety data sheet (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 20
  unreachable: 3
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: the MakeItFrom 5251 page (403), the PubChem aluminium record (verification page), and the Smith and Kaiser PDFs were read as text with pdftotext. Caveats: the H22 and H24 strength values are BS EN 485-2 minima from one stockholder; the H34 values are an Australian and New Zealand specification; the thermal conductivity differs between datasheets (134, 138 and 149 W/(m·K)); the space uses are one supplier''s claim; the hazard entries rest on two sheets that are not 5251-specific.'
story:
  risk_groups:
    - title: For people
      lead: The solid alloy is described as not hazardous in one sheet, but processing dust and welding fume are the real concern.
      level: 1
      verdict: Low as solid sheet, higher for dust and fume
      points:
        - label: Solid sheet
          line: The Texarkana 5xxx-series sheet says the formed solid as shipped is not hazardous. The Kaiser sheet says the material is considered hazardous under US hazard communication rules, so the two family sheets disagree on the solid's status.
        - label: Dust and fumes
          line: Kaiser says dust may irritate the eyes, skin and airways, and Texarkana notes combustible dust concentrations during processing. Welding and cutting may release hazardous fumes.
    - title: If it fails
      lead: The failure routes in the sources are weld strength loss and softening by heat. No spacecraft service data for 5251 was found.
      points:
        - label: Weld zone
          line: Smith says a good weld is likely to have strength of up to 160 MPa maximum, against a minimum tensile strength of 190 MPa for H22 sheet (Aalco).
        - label: Heat
          line: Atlas says heating cold-worked sheet to about 345 °C softens it, so the cold-work strength is removed.
    - title: Handling and storage
      points:
        - label: Pick the temper
          line: The datasheets quote the temper by thickness. H22 has a minimum proof stress of 120 MPa, H24 of 140 MPa and O of 60 MPa.
        - label: Filler
          line: Aalco recommends 5356 filler for welding 5251 to itself and to most other 5XXX and 6XXX alloys.
  why: Aluminium alloy 5251 is chosen for sheet work that has to bend and weld and resist seawater, with more strength than pure aluminium. Its magnesium content is low enough that Atlas says it avoids the stress corrosion cracking of alloys with more than about 3.5 % Mg. At 2.69 g/cm3 (Aalco H22) it is light compared with steel. Suppliers list it for boats, panelling, pressure work, fuel tanks and, in one supplier's claim, satellite shells.
  uses:
    - where: Marine and sheet metal work
      line: Aalco lists boats, panelling and pressings, marine structures, vehicle panels and containers as typical uses.
    - where: Aircraft and spacecraft parts (supplier claims)
      line: Chalco says 5251 can be used for aircraft fuselage shells, fuel tanks and oxygen cylinders, and that it has been used for satellite shells and missile structures. These are supplier claims, and no qualification data was opened.
    - where: Heat transfer and pressure work
      line: Smith lists heat transfer devices, pressure vessels, boiler making and chemical industry work among typical uses of its 5251 sheet.
  can_do:
    - label: Carry heat
      value: 138 W/(m·K)
      benchmark: thermal_conductivity
      line: Atlas gives 138 W/(m·K) at 25 °C as a typical value. Smith prints 149 and Aalco prints 134, both without a stated temperature, so the datasheets differ.
    - label: Strength when soft
      value: 60 MPa proof stress (O)
      benchmark: yield_strength
      line: The O temper has a minimum proof stress of 60 MPa and a tensile strength of 160 to 200 MPa, per the BS EN 485-2 values in the AZoM table.
    - label: Strength after cold work
      value: 120 MPa proof stress (H22)
      benchmark: yield_strength
      line: H22 has a minimum proof stress of 120 MPa and a tensile strength of 190 to 230 MPa. H24 has 140 MPa and 210 to 250 MPa.
    - label: Weight
      value: 2.69 g/cm3
      benchmark: density
      line: Density is 2.69 g/cm3 in the Aalco datasheet. Atlas gives 2680 kg/m3 as a typical value.
    - label: Melting
      value: 605 to 650 °C
      benchmark: melting_point
      line: Euralliage gives a solidus of 605 °C and a liquidus of 650 °C.
    - label: Expansion
      value: 23.8 µm/m/°C
      benchmark: cte
      line: Atlas gives a mean thermal expansion of 23.8 µm/m/°C between 20 and 100 °C.
  compare: Atlas says the specified yield strength of this alloy in the H32 and H34 tempers is substantially lower than that of its sister alloy in the same tempers, so substitution needs care. The USGS says copper can replace aluminium in electrical and heat-exchange applications, so the two metals compete in conductors and heat exchangers.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Specify the temper and thickness, because the minimum strengths change with both.
    - Weld with 5356 filler, and plan for weld strength of up to about 160 MPa (Smith).
    - Control dust during cutting, grinding and welding (Texarkana).
  good_for:
    - Marine and sheet-metal structures, where seawater and atmospheric corrosion resistance matter (Aalco, Atlas).
    - 'Formed and welded sheet: H22 and H24 are readily weldable (Aalco) and have good formability (Euralliage).'
    - 'Anodising for decorative and technical finishes (Smith: very good anodising properties).'
  watch_out:
    - 'Strength is modest: 120 MPa minimum proof stress in H22.'
    - 'Welds lose strength: a good weld reaches up to about 160 MPa (Smith).'
    - The fuel-tank and satellite uses rest on supplier claims; no spacecraft qualification standard for 5251 was found in this run.
    - The two SDS family sheets disagree on the solid's hazard status, and neither is specific to 5251.
    - Datasheets quote different standards (BS EN 485-2 and AS/NZS 1734), so the limits are not interchangeable.
  verdict: Aluminium alloy 5251 is a weldable, corrosion-resistant magnesium alloy for marine and sheet-metal structures, with a minimum H22 proof stress of 120 MPa at 2.69 g/cm3. Its spacecraft uses are one supplier's claim, and the profile has no spacecraft qualification, outgassing, atomic-oxygen or radiation data.
  recipe:
    line: Wrought aluminium alloy AlMg2Mn0.3, with magnesium as the main alloying element and manganese as the second (Atlas describes it as a 2 % magnesium, 0.3 % manganese alloy). It is not heat-treatable; strength comes from cold rolling into the H tempers and partial annealing (Atlas). Composition limits are from Aalco (BS EN 573-3). The datasheets do not describe the casting route.
    parts:
      - name: Aluminium
        symbol: Al
        share: balance
        role: Matrix metal. Aalco prints aluminium as the balance of the composition.
      - name: Magnesium
        symbol: Mg
        share: 1.70 to 2.40 wt%
        role: Main alloying element; the alloy is non-heat-treatable and its strength comes from cold work (Atlas).
      - name: Manganese
        symbol: Mn
        share: 0.10 to 0.50 wt%
        role: Alloying element, printed with magnesium in the designation AlMg2Mn0.3 (Modulus Metal, DIN 1725-1).