spore: profile
id: mu-metal
spore_version: 0.2
family: magnet-and-superconducting-alloys
name: Mu-metal
abbreviation: Ni-Fe-Mo
role: magnetic shield
category: metals
type: magnet-alloys
summary: |
  Mu-metal is a soft nickel-iron-molybdenum alloy, nominally 80 % Ni and 5 % Mo (ASTM A753 Alloy 4), used to shield sensitive electronics from static and low-frequency magnetic fields. The Magnetic Shield Corporation sheet gives a DC permeability of at least 400,000 at 0.005 Oe, an AC permeability of at least 75,000 at 60 Hz and 0.4 A/m, a saturation induction of 0.75 T and a density of 8.7 g/cm3. Its strength is modest: a supplier page gives 530 MPa tensile and 160 MPa yield in the final annealed state.
best_for: 'Shielding sensitive electronics from static and low-frequency fields: DC permeability of at least 400,000 and AC permeability of at least 75,000 at 60 Hz in the MuMETAL sheet datasheet'
weakest_at: 'Strength and weight: 160 MPa yield in the final annealed state and 8.7 g/cm3 density, and the permeability falls after shock or plastic strain, which needs a re-anneal to recover'
identity:
  formula: Nickel-iron-molybdenum soft magnetic alloy, nominal 80 % Ni and 5 % Mo by weight, balance Fe, with Mn 0.50 % and Si 0.15 % nominal (CarTech HyMu 800 type analysis)
  source: carpenter-hymu800
  where: 'Type Analysis table: Carbon 0.01 %, Manganese 0.50 %, Silicon 0.15 %, Nickel 80.00 %, Molybdenum 5.00 %, Iron balance'
  designations:
    - system: UNS
      code: N14080
      source: msc-mumetal
      where: 'Specifications paragraph: meets ASTM-A-753 Alloy 4, UNS N14080'
    - system: ASTM
      code: A753
      note: Alloy 4
      source: carpenter-hymu800
      where: 'Other Information, Applicable Specifications: ASTM A753 Alloy 4'
    - system: DIN
      code: '17745'
      source: msc-mumetal
      where: 'Specifications paragraph: DIN 17745'
    - system: JIS
      code: C 2531
      source: matthey-permimphy
      where: 'International Standards table: JIS C 2531, row N14080 Type 4'
    - system: Trade name
      code: MuMETAL
      source: msc-mumetal
      where: 'Footer and product title: MuMETAL registered trademark of Magnetic Shield Corporation'
    - system: Trade name
      code: Mumetall
      source: wikipedia-mumetal
      where: 'Lead section: trade names such as MuMETAL, Mumetall and Mumetal2'
    - system: Trade name
      code: Permimphy
      source: matthey-permimphy
      where: 'Title and main technical properties: Permimphy N14080 type 4 alloy'
tags:
  environments: []
  applications:
    - electronics-and-chips
properties:
  - benchmark: saturation_induction
    label: Saturation induction, stress annealed sheet
    value: 0.75
    unit: T
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo, stress annealed sheet
      temperature: not stated
      unit_in_source: 7,500 G (0.75 T)
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Saturation Induction (Bs)
  - benchmark: saturation_induction
    label: Saturation induction at 20 °C
    value: 0.8
    unit: T
    scope: material
    conditions:
      grade: Permimphy N14080 type 4 (80 % Ni, 5 % Mo)
      temperature: 20 °C
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Physical properties table, row Saturation induction at 20ºC
  - benchmark: permeability_dc_min
    label: DC permeability at 0.005 Oe, minimum
    value: 400000
    bound: lower
    unit: '-'
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      field: 0.005 Oe (0.4 A/m)
      sample: stamped rings of 0.35 mm sheet after perfection annealing
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: DC Magnetic Properties, row Permeability at 0.005 Oe
  - benchmark: permeability_ac_60hz
    label: AC permeability at 60 Hz and 0.4 A/m, minimum
    value: 75000
    bound: lower
    unit: '-'
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      frequency: 60 Hz
      field: 0.4 A/m
      sample: stamped rings of 0.35 mm sheet after perfection annealing
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: AC (60 Hz) Magnetic Properties, row Permeability at 0.4 A/m
  - benchmark: permeability_dc
    label: DC permeability at 5 mOe, typical, 1.00 mm strip
    value: 470000
    unit: '-'
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      thickness: 1.00 mm
      field: 5 mOe (0.4 A/m)
      treatment: ring samples annealed at 1170 °C in dry pure hydrogen
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Magnetic properties table, DC row, thickness 1.00 - 0.04 mm
  - benchmark: permeability_dc
    label: DC permeability at 5 mOe, typical, 0.34 mm strip
    value: 520000
    unit: '-'
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      thickness: 0.34 mm
      field: 5 mOe (0.4 A/m)
      treatment: ring samples annealed at 1170 °C in dry pure hydrogen
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Magnetic properties table, DC row, thickness 0.34 - 0.0134 mm
  - benchmark: permeability_max
    label: Maximum DC permeability after final heat treatment
    value: 350000
    value_high: 500000
    bound: range
    unit: '-'
    scope: material
    conditions:
      grade: Mu-metal, final heat treatment in dry hydrogen
      condition: typical DC magnetic properties after final heat treatment
    method: Range printed on a manufacturer web page
    status: ground
    source: msc-mumetal-web
    where: Typical Final Annealed Properties block, Typical Magnetic Properties (DC), row Permeability Mumax
  - benchmark: coercive_force
    label: Coercive force after final heat treatment
    value: 0.6
    unit: A/m
    scope: material
    conditions:
      condition: typical DC magnetic properties after final heat treatment
    method: Typical value printed on a manufacturer web page
    status: ground
    source: msc-mumetal-web
    where: Typical Magnetic Properties (DC) block, row Coercive Force
  - benchmark: curie_temperature
    label: Curie temperature
    value: 420
    unit: °C
    scope: material
    conditions:
      unit_in_source: 788 °F
    method: Value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Curie Temperature
  - benchmark: density
    label: Density, stress annealed sheet
    value: 8.7
    unit: g/cm3
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      unit_in_source: 0.316 lb/in3
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Density
  - benchmark: density
    label: Density, 80 Ni 5 Mo alloy (HyMu 800)
    value: 0.316
    unit: lb/in3
    scope: material
    conditions:
      grade: HyMu 800, 80 Ni 5 Mo
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: carpenter-hymu800
    where: Physical Properties, row Density
  - benchmark: melting_point
    label: Melting temperature
    value: 1450
    unit: °C
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Physical properties table, row Melting point
  - benchmark: thermal_conductivity
    label: Thermal conductivity, stress annealed sheet
    value: 19
    unit: W/(m·K)
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      temperature: not stated
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 80 Ni 5 Mo alloy (HyMu 800)
    value: 240
    unit: BTU-in/hr/ft2/°F
    scope: material
    conditions:
      grade: HyMu 800, 80 Ni 5 Mo
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: carpenter-hymu800
    where: Physical Properties, row Thermal Conductivity
  - benchmark: cte
    label: Thermal expansion coefficient, stress annealed sheet
    value: 12
    unit: 10-6/K
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Thermal Expansion
  - benchmark: cte
    label: Mean coefficient of thermal expansion, -90 to 400 °F
    value: 7.2
    unit: 10-6 in/in/°F
    scope: material
    conditions:
      grade: HyMu 800, 80 Ni 5 Mo
      temperature: '-90 to 400 °F'
    method: Value printed in a manufacturer datasheet
    status: ground
    source: carpenter-hymu800
    where: Physical Properties, row Mean CTE (-90 to 400°F)
  - benchmark: specific_heat
    label: Specific heat
    value: 460
    unit: J/(kg·K)
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Specific Heat
  - benchmark: electrical_resistivity
    label: Electrical resistivity, stress annealed sheet
    value: 60
    unit: µΩ·cm
    scope: material
    conditions:
      grade: MuMETAL, 80 Ni 5 Mo
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: msc-mumetal
    where: Physical Properties table, row Electrical Resistivity
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 70 °F, 80 Ni 5 Mo alloy (HyMu 800)
    value: 370
    value_high: 380
    bound: range
    unit: ohm-cir-mil/ft
    scope: material
    conditions:
      grade: HyMu 800, 80 Ni 5 Mo
      temperature: 70 °F
    method: Range printed in a manufacturer datasheet
    status: ground
    source: carpenter-hymu800
    where: Physical Properties, row Electrical Resistivity (70°F)
  - benchmark: elastic_modulus
    label: Modulus of elasticity, Permimphy strip
    value: 190
    value_high: 221
    bound: range
    unit: kN/mm2
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      temperature: not stated
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Physical properties table, row Modulus of elasticity
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, soft annealed temper R500
    value: 500
    value_high: 700
    bound: range
    unit: N/mm2
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      temper: R500 soft annealed
      product_form: strip
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Mechanical properties of strips table, row R500 soft annealed, column Rm
  - benchmark: yield_strength
    label: Yield strength Rp0.2, soft annealed temper R500
    value: 200
    value_high: 450
    bound: range
    unit: N/mm2
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      temper: R500 soft annealed
      measure: Rp0.2
      product_form: strip
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Mechanical properties of strips table, row R500 soft annealed, column Rp0.2
  - benchmark: elongation
    label: Elongation A50mm, soft annealed temper R500, minimum
    value: 25
    bound: lower
    unit: '%'
    scope: material
    conditions:
      grade: Permimphy N14080 type 4
      temper: R500 soft annealed
      gauge_length: 50 mm
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: matthey-permimphy
    where: Mechanical properties of strips table, row R500 soft annealed, column A50mm
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, final annealed
    value: 530
    unit: MPa
    scope: material
    conditions:
      grade: Mu-metal
      temper: final annealed (after dry hydrogen heat treatment)
      form: typical final annealed properties
    method: Typical value printed on a manufacturer web page
    status: ground
    source: msc-mumetal-web
    where: Typical Final Annealed Properties block, row Tensile Strength
  - benchmark: yield_strength
    label: Yield strength 0.2 %, final annealed
    value: 160
    unit: MPa
    scope: material
    conditions:
      grade: Mu-metal
      temper: final annealed (after dry hydrogen heat treatment)
      measure: 0.2 % offset
    method: Typical value printed on a manufacturer web page
    status: ground
    source: msc-mumetal-web
    where: Typical Final Annealed Properties block, row 0.2 % Yield Strength
  - benchmark: elongation
    label: Elongation, final annealed
    value: 45
    unit: '%'
    scope: material
    conditions:
      grade: Mu-metal
      temper: final annealed (after dry hydrogen heat treatment)
    method: Typical value printed on a manufacturer web page
    status: ground
    source: msc-mumetal-web
    where: Typical Final Annealed Properties block, row Elongation
  - benchmark: ultimate_tensile_strength
    label: Tensile strength after in-process anneal, maximum
    value: 690
    bound: upper
    unit: MPa
    scope: material
    conditions:
      grade: HyMu 800, 80 Ni 5 Mo
      temper: after in-process strand anneal at 1000/1050 °C, before further cold rolling
    method: Maximum value printed in a manufacturer datasheet
    status: ground
    source: carpenter-hymu800
    where: Heat Treatment, In-Process Anneal paragraph (100 ksi (690 MPa) maximum)
corrosion:
  - environment: Uncoated, in ordinary air
    headline: The high nickel content lets the alloy be used without a corrosion-resistant coating.
    effect: The Permimphy datasheet says the high nickel content allows use of this material without a corrosion resistant coating. No corrosion rate, humidity test or salt-spray result is printed in the sources read.
    rating: low
    conditions:
      grade: Permimphy N14080 type 4
      exposure: not stated
      basis: manufacturer statement, no test data
    source: matthey-permimphy
    where: Main technical properties and features, first paragraph
risks:
  hazards:
    - text: PubChem's GHS record for nickel (CID 935) lists H317 (may cause an allergic skin reaction), H351 (suspected of causing cancer) and H372 (causes damage to organs through prolonged or repeated exposure), signal word Danger. These are the classes for nickel metal, not for the alloy, which is not separately classified in the sources read; the alloy is about 80 % nickel.
      ghs:
        - H317
        - H351
        - H372
      source: pubchem-ni
      where: GHS Classification section, Hazard Statements
  failure_risks:
    - mode: Permeability loss from shock or plastic strain
      trigger: Severe shock, forming or further mechanical working after the final anneal
      consequence: The Magnetic Shield page says the enlarged grains are susceptible to severe shocks or further mechanical working, and the permeability will decrease in those areas. A re-anneal can restore it.
      severity: moderate
      source: msc-mumetal-web
      where: Heat treatment paragraph after the dry hydrogen anneal description
    - mode: Contamination or oxidation during the anneal
      trigger: Heat treatment without a protective atmosphere, or with parts not cleaned or handled with care
      consequence: Permimphy says a protective atmosphere is essential to avoid oxidation, that treated parts must avoid plastic deformation which degrades the magnetic properties, and that parts must be degreased and cleaned first.
      severity: moderate
      source: matthey-permimphy
      where: Heat treatment of finished parts paragraph
  side_effects:
    - text: The MuMETAL sheet gives a density of 8.7 g/cm3, so shields and cored components add mass.
      affects: Mass of a shield or cored component
      source: msc-mumetal
      where: Physical Properties table, row Density
  handling:
    - text: The Carpenter sheet says oil, grease, lacquer and all other contaminants must be removed before annealing, and parts should be separated by an inert powder such as magnesium or aluminium oxide during the hydrogen anneal. It recommends an oxygen-free, dry hydrogen anneal with a dew point below -40 °C, at 2050/2150 °F (1120/1177 °C), held 2 to 4 hours.
      source: carpenter-hymu800
      where: Heat Treatment, Thermal Treatment for Magnetic Properties paragraph
    - text: The Permimphy sheet recommends pure dry hydrogen for the anneal, between 800 and 1150 °C, with anhydrous inert powder to keep parts apart.
      source: matthey-permimphy
      where: Heat treatment of finished parts paragraph
uses:
  - application: electronics-and-chips
    device: Magnetic shielding for sensitive electronics, current sensors and current transformer cores
    example: The MuMETAL sheet datasheet says MuMETAL bar is used in high quality magnetic shielding, current sensors, high precision current transformer cores and ground fault circuit breaker relay parts.
    source: msc-mumetal
    where: Description paragraph
  - application: electronics-and-chips
    device: Relays, stepper motors and magnetic sensors
    example: Permimphy's main applications include relays for ground fault circuit breakers and railway signalling, stepper motors for watches, shielding and magnetic sensors for current, angular position and displacement.
    source: matthey-permimphy
    where: Typical uses paragraph
  - application: electronics-and-chips
    device: Spacecraft magnetic cleanliness, soft magnetic parts near magnetometers
    example: NASA SP-8018, a 1969 spacecraft design criteria document, names Mu-metal, with mild steel, as an example of a soft magnetic material in its guidance on magnetic cleanliness. It warns that enclosing a component in a highly permeable container can create problems for the shielded component.
    source: nasa-sp8018
    where: Section on magnetic materials, paragraph on hard and soft materials; Shielding paragraph (reference 37)
supply:
  - subject: Nickel (about 80 % of the alloy)
    producers:
      - country: Indonesia
        share_percent: 66.7
        year: 2025
      - country: Philippines
        share_percent: 6.9
        year: 2025
      - country: Russia
        share_percent: 5.1
        year: 2025
    critical_lists: []
    recycling: 'USGS: in 2025 nickel recovered from scrap accounted for approximately 60 % of apparent consumption, and most secondary nickel was in the form of stainless steel scrap.'
    substitutes: []
    source: usgs-mcs2026-nickel
    where: 'World Mine Production and Reserves table, 2025e column, metric tons of nickel content: Indonesia 2,600,000; Philippines 270,000; Russia 200,000; world total 3,900,000 (shares calculated by Space Mushroom from these figures). Recycling paragraph.'
  - subject: Molybdenum (about 5 % of the alloy)
    producers:
      - country: China
        share_percent: 37.3
        year: 2025
      - country: Chile
        share_percent: 16.2
        year: 2025
      - country: Peru
        share_percent: 15
        year: 2025
    critical_lists: []
    recycling: 'USGS: molybdenum is recycled as a component of catalysts, ferrous scrap and superalloy scrap, and the molybdenum content of recycled alloys is significant and reused.'
    substitutes:
      - 'USGS: there is little substitution for molybdenum in its major application in steels and cast irons.'
    source: usgs-mcs2026-molybdenum
    where: 'World Mine Production and Reserves table, 2025e column, thousand metric tons: China 97,000; Chile 42,000; Peru 39,000; world total 260,000 (shares calculated by Space Mushroom). Events, Trends and Issues: China, Chile, the United States, Peru and Mexico produced 90 % of world output in 2025.'
documents:
  - title: Magnetic Shield Corporation, MuMETAL stress annealed sheet data
    type: datasheet
    url: https://www.magnetic-shield.com/content/MuMetal%20Stress%20Annealed%20Sheet%20Data.pdf
  - title: CarTech HyMu 800 alloy datasheet (Carpenter Technology, 2020 copyright)
    type: datasheet
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/HyMu%20800.pdf
    year: 2020
  - title: Lamineries Matthey, Mumetal Permimphy datasheet
    type: datasheet
    url: https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/EN/Permimphy_v22E.pdf
  - title: 'Wikipedia: Mu-metal'
    type: report
    url: https://en.wikipedia.org/wiki/Mu-metal
  - title: NASA SP-8018, Space Vehicle Design Criteria (Guidance and Control), NTRS 19690020961
    type: report
    url: https://ntrs.nasa.gov/citations/19690020961
    year: 1969
  - title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
  - title: PubChem compound record for nickel (CID 935), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Nickel
gaps:
  - No flight-proven mu-metal magnetic shield on a named spacecraft was found in this run. MAVEN and MMS magnetometer papers mention mu-metal test chambers, but the full texts were not read (the Springer PDF was blocked), so the only space use entered is the NASA SP-8018 design guidance.
  - The DAMPE satellite calorimeter (arXiv 1309.7638) shielded a photomultiplier with a permalloy cylinder, not mu-metal, so it is not entered as a mu-metal use.
  - The MuMETAL sheet mechanical table (tensile 650 MPa, yield 280 MPa, elongation 35 %, hardness 130 to 170 HV) gives no temper, so it is not entered. The Permimphy and final-annealed values are used instead.
  - The HyMu 800 magnetic curves (DC, 60 Hz and 400 Hz permeability and core loss) are graphs with no printed table in the PDF, so no values were taken from them.
  - The Permimphy electrical resistivity is printed as 55 with no unit, so it is not entered. The MuMETAL sheet gives 60 µΩ·cm.
  - The mumetal.co.uk page gives 4.5 % molybdenum, which conflicts with 5 % in the other sources, so its composition is not used. The Wikipedia range of 12 to 15 % iron is a different formulation and is not used.
  - Corrosion rate and salt-spray or humidity data for mu-metal were not found. The only corrosion statement is a manufacturer claim that the high nickel content needs no coating.
  - No ASTM A753 standard text was opened, so the grade limits for Alloy 4 are taken from the Carpenter and Matthey datasheets only. The Fabdigit page was blocked by a security checkpoint.
  - The GHS hazard codes are for nickel metal (PubChem CID 935). No hazard classification of the 80Ni-5Mo alloy itself was found.
  - Whether nickel or molybdenum is on the U.S. 2025 final critical minerals list was not confirmed in the USGS text read, so critical_lists is empty for both.
  - Radiation effects, cold-welding and outgassing data for mu-metal were not looked up.
  - 'Dates for the HyMu 800 datasheet: the PDF gives an edition date of 11/01/1991 and a 2020 copyright, so the version is uncertain.'
sources:
  msc-mumetal:
    title: Magnetic Shield Corporation, MuMETAL stress annealed sheet data sheet
    url: https://www.magnetic-shield.com/content/MuMetal%20Stress%20Annealed%20Sheet%20Data.pdf
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  msc-mumetal-web:
    title: Magnetic Shields Limited, Mu Metal specifications page (mumetal.co.uk)
    url: https://mumetal.co.uk/?p=100
    kind: web
    license: Manufacturer web page (cited, not reproduced)
  carpenter-hymu800:
    title: CarTech HyMu 800 alloy data sheet, Carpenter Technology
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/HyMu%20800.pdf
    kind: datasheet
    license: Manufacturer data sheet, typical values (cited, not reproduced)
  matthey-permimphy:
    title: Lamineries Matthey, Mumetal Permimphy N14080 type 4 datasheet
    url: https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/EN/Permimphy_v22E.pdf
    kind: datasheet
    license: Manufacturer data sheet (cited, not reproduced)
  wikipedia-mumetal:
    title: 'Wikipedia: Mu-metal'
    url: https://en.wikipedia.org/wiki/Mu-metal
    kind: web
    license: CC BY-SA (cited, not reproduced)
  nasa-sp8018:
    title: NASA SP-8018, Space Vehicle Design Criteria (Guidance and Control), magnetic materials and shielding sections
    id: NTRS 19690020961
    url: https://ntrs.nasa.gov/citations/19690020961
    year: 1969
    kind: report
    license: NASA public document (cited, not reproduced)
  usgs-mcs2026-nickel:
    title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: Public domain (USGS)
  usgs-mcs2026-molybdenum:
    title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
    kind: report
    license: Public domain (USGS)
  pubchem-ni:
    title: 'PubChem compound record: Nickel (CID 935), GHS classification'
    id: CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Nickel
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and notifiers
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 27
  unreachable: 2
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-26 from the datasheets, web pages and reports named in each entry. Unreachable: the MAVEN and MMS Springer full texts (blocked) and the Fabdigit page (security checkpoint). Caveats: the 80Ni-5Mo values come from three manufacturers and a supplier web page with typical or nominal figures; the permeability and strength values are typical, not guaranteed; the spacecraft use is design guidance, not a flight record; the hazard codes are for nickel metal; the supply shares are calculated from USGS tonnages.'
story:
  risk_groups:
    - title: For people
      lead: The hazard classes in the sources are for nickel metal, which makes up about 80 % of the alloy. No separate classification of the alloy was found.
      level: 1
      verdict: Nickel classes
      points:
        - label: Nickel as a substance
          line: PubChem's GHS record for nickel lists H317 allergic skin reaction, H351 suspected cancer and H372 organ damage from repeated exposure, with signal word Danger.
        - label: Alloy as handled
          line: No health classification of the 80Ni-5Mo alloy itself was found in the sources read.
    - title: If it fails
      lead: The failure routes in the sources are mechanical and thermal. None of them is a flight result for mu-metal.
      points:
        - label: Shock and forming
          line: Severe shock or further mechanical working after the anneal lowers the permeability in the affected areas. A re-anneal can restore it.
        - label: Poor anneal
          line: Oxidation or contamination during the hydrogen anneal, or plastic deformation of the treated part, degrades the magnetic properties.
        - label: Mass
          line: At 8.7 g/cm3 the alloy is heavy, so a shield adds mass to the spacecraft or instrument.
    - title: Handling and storage
      points:
        - label: Clean before anneal
          line: Remove oil, grease, lacquer and contaminants before annealing. Separate parts with inert powder such as magnesium or aluminium oxide.
        - label: Anneal in dry hydrogen
          line: The HyMu 800 datasheet recommends an oxygen-free, dry hydrogen anneal with a dew point below -40 °C, held 2 to 4 hours at 1120 to 1177 °C (2050/2150 °F).
  why: Mu-metal is used to shield sensitive electronics from static and low-frequency magnetic fields. It is a soft nickel-iron-molybdenum alloy with nominal 80 % Ni and 5 % Mo, and its high permeability gives a low-reluctance path for the field. The MuMETAL sheet datasheet gives a DC permeability of at least 400,000 at 0.005 Oe and an AC permeability of at least 75,000 at 60 Hz. The saturation induction is 0.75 T, and the Curie temperature is 420 °C. The sources read give it a yield strength of 160 MPa in the final annealed state, so it is chosen for its magnetic performance, not for its strength.
  uses:
    - where: Magnetic shields and sensors
      line: MuMETAL is used in high quality magnetic shielding, current sensors and high precision current transformer cores. Permimphy is used for relays, stepper motors and magnetic sensors.
    - where: Spacecraft magnetic cleanliness
      line: NASA SP-8018 lists Mu-metal as an example of a soft magnetic material to consider for spacecraft magnetic cleanliness, and warns that shielding by a highly permeable container can create problems.
  can_do:
    - label: Shield a field
      value: 400000 DC permeability
      benchmark: permeability_dc_min
      line: The MuMETAL sheet gives a DC permeability of at least 400,000 at 0.005 Oe, and at least 75,000 at 60 Hz and 0.4 A/m for AC.
    - label: Saturate at low field
      value: 0.75 T
      benchmark: saturation_induction
      line: Saturation induction is 0.75 T in the MuMETAL sheet and 0.8 T at 20 °C in the Permimphy datasheet. The alloy saturates at low fields, which keeps its hysteresis loss low in AC circuits.
    - label: Weight
      value: 8.7 g/cm3
      benchmark: density
      line: Density is 8.7 g/cm3 in the MuMETAL sheet, and 0.316 lb/in3 in the HyMu 800 datasheet.
    - label: Strength when annealed
      value: 530 MPa tensile
      benchmark: ultimate_tensile_strength
      line: In the final annealed state a supplier page gives 530 MPa tensile, 160 MPa yield and 45 % elongation. Soft annealed strip in the Permimphy datasheet has a tensile strength of 500 to 700 N/mm2.
  compare: The alloy is chosen to shield a field, not to carry a load, so its low yield strength matters less than its permeability. The density of 8.7 g/cm3 is the figure to weigh against any alternative shield.
  compare_rows:
    - label: Density
      benchmark: density
    - label: DC permeability
      benchmark: permeability_dc_min
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Anneal in dry hydrogen with a dew point below -40 °C, after removing all oil and contaminants.
    - Avoid shock and plastic deformation after the anneal, because the permeability falls and needs a re-anneal to recover.
    - The only hazard codes found are for nickel metal (PubChem); treat the alloy with the same care until a supplier classification is found.
  good_for:
    - 'Shielding sensitive electronics from static and low-frequency fields: at least 400,000 DC permeability and 75,000 AC permeability at 60 Hz.'
    - Current transformer cores and relay parts, as the datasheets list.
    - Spacecraft magnetic cleanliness design, where soft magnetic parts must be chosen with care.
  watch_out:
    - 'Soft and weak: 160 MPa yield in the final annealed state.'
    - 'Heavy: 8.7 g/cm3, so a shield adds mass.'
    - Permeability is lost after shock or forming, and the alloy needs a re-anneal to recover.
    - No corrosion rate or flight record was found for the alloy; the only statement is a manufacturer's claim that no coating is needed.
    - The only hazard codes found are for nickel metal, not for the alloy.
  verdict: Mu-metal is a soft nickel-iron-molybdenum alloy with very high permeability, nominally 80 % Ni and 5 % Mo, used to shield sensitive electronics. It is heavy and weak, and its permeability depends on a careful dry hydrogen anneal and on keeping the part free of shock and deformation. Spacecraft use is documented as design guidance; no flight record was found in this run.
  recipe:
    line: Mu-metal is a nickel-iron-molybdenum alloy, nominally 80 % Ni and 5 % Mo, with balance Fe and small manganese and silicon (CarTech HyMu 800 type analysis; MuMETAL sheet typical composition 80 Ni, 5.0 Mo, Mn 0.3 to 0.5, Si 0.1 to 0.4). Its magnetic properties come from a final anneal in dry hydrogen; the HyMu 800 datasheet gives 2050/2150 °F (1120/1177 °C) for low-frequency response, and the Permimphy datasheet gives 800 to 1150 °C.
    parts:
      - name: Nickel
        symbol: Ni
        share_percent: 80
        share_note: nominal, 80.00 % in the type analysis
        role: Main element of the alloy, nominal 80 %
        source: carpenter-hymu800
        where: Type Analysis table, Nickel 80.00 %
      - name: Molybdenum
        symbol: Mo
        share_percent: 5
        share_note: nominal, 5.00 % in the type analysis
        role: Alloying element; the Permimphy datasheet says molybdenum increases magnetic permeability
        source: carpenter-hymu800
        where: Type Analysis table, Molybdenum 5.00 %
      - name: Manganese
        symbol: Mn
        share_percent: 0.5
        share_note: nominal, 0.50 %
        role: Minor element, nominal
        source: carpenter-hymu800
        where: Type Analysis table, Manganese 0.50 %
      - name: Silicon
        symbol: Si
        share_percent: 0.15
        share_note: nominal, 0.15 %
        role: Minor element, nominal
        source: carpenter-hymu800
        where: Type Analysis table, Silicon 0.15 %
      - name: Iron
        symbol: Fe
        share_note: balance
        role: Balance of the alloy
        source: carpenter-hymu800
        where: Type Analysis table, Iron Balance