spore: profile
id: nitinol
spore_version: 0.2
family: nickel-titanium-alloys
name: Nitinol
abbreviation: NiTi
role: shape-memory and superelastic alloy for actuators and deployable parts
category: metals
type: shape-memory-alloys
summary: |
  Nitinol is a near-equiatomic nickel-titanium alloy, about 55 wt % nickel with titanium as the balance, that recovers a set shape on heating and springs back from large strains. A NASA 1972 review gives its density as 6.45 g/cm3 at 25 °C for a 55.1 wt % nickel alloy, and a melting range of 1240 to 1310 °C. Its two phases differ widely in stiffness: the austenite phase has an elastic modulus of 75 to 83 GPa and the martensite phase 28 to 40 GPa.
best_for: 'Parts that must change shape or spring back: shape-memory actuators, torque tubes and self-erectable structures, with a 6.45 g/cm3 density and a 75 to 83 GPa austenite modulus'
weakest_at: 'Nickel content and fatigue: the alloy is about half nickel, which an SDS classes with H317 and H351, and its transformation temperature moves with small composition changes'
identity:
  formula: NiTi, near-equiatomic nickel-titanium alloy with nickel nominally 54.5 to 57.0 wt % and titanium as the balance
  source: astm
  where: 'Abstract: nominally 54.5 % to 57.0 % nickel, made from nickel and titanium with no other intentional alloy additions'
  designations:
    - system: ASTM
      code: F2063
      note: wrought nickel-titanium shape memory alloys for medical devices and surgical implants
      source: astm
      where: Title and abstract of the F2063-26 store page
    - system: Trade name
      code: SE508
      note: Confluent Medical standard medical-device grade nitinol
      source: confluent
      where: Nitinol material page, grade list SE508 and SE508 ELI
    - system: Trade name
      code: 55-Nitinol
      note: named for 55 wt % nickel
      source: nasa1972
      where: Title and introduction, 55-Nitinol series
tags:
  environments: []
  stresses: []
  applications:
    - mechanisms
    - structures
properties:
  - benchmark: density
    label: Density, 55.1 wt % Ni alloy
    value: 6.45
    unit: g/cm3
    scope: material
    conditions:
      composition: 55.1 weight percent Ni alloy
      temperature: 25 °C
    method: Measured value cited in the NASA 1972 review, attributed there to Buehler and Wiley (ref. 74)
    status: ground
    source: nasa1972
    where: Density section, first paragraph
  - benchmark: melting_point
    label: Melting range, 55.1 wt % Ni alloy
    value: 1240
    value_high: 1310
    bound: range
    unit: °C
    scope: material
    conditions:
      composition: 55.1 weight percent Ni alloy
      pressure: not stated
    method: Range cited in the NASA 1972 review (ref. 74); the review says it is not a true temperature range but reflects uncertainty in the phase diagram, and that NiTi as a congruent melting compound should show a clear melting point
    status: ground
    source: nasa1972
    where: Melting Point section, first paragraph
  - benchmark: electrical_resistivity
    label: Electrical resistivity, high-temperature CsCl(B2) form
    value: 82
    unit: µΩ·cm
    scope: material
    conditions:
      composition: 50.0 atomic percent Ti
      heat_treatment: annealed 1 h at 900 °C, water quenched
      temperature: extrapolated to about 70 °C
      structure: CsCl(B2), high-temperature form
      unit_in_source: microhm-cm
    method: Value from the resistivity table in the NASA 1972 review, which cites Hanlon et al. (ref. 59)
    status: ground
    source: nasa1972
    where: Electrical Resistivity section, table column CsCl(B2) structure, first row
  - benchmark: electrical_resistivity
    label: Electrical resistivity, low-temperature structure
    value: 76
    unit: µΩ·cm
    scope: material
    conditions:
      composition: 50.0 atomic percent Ti
      heat_treatment: annealed 1 h at 900 °C, water quenched
      temperature: extrapolated to about 70 °C
      structure: low-temperature (martensite) structure
      unit_in_source: microhm-cm
    method: Value from the resistivity table in the NASA 1972 review, which cites Hanlon et al. (ref. 59)
    status: ground
    source: nasa1972
    where: Electrical Resistivity section, table column Low-temperature structure, first row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, austenite
    value: 0.18
    unit: W/cm·K
    scope: material
    conditions:
      phase: austenite
      composition: not stated
      temper: not stated
      unit_in_source: W/cm·K
    method: Typical value in the Wikipedia nickel titanium property table (secondary source; the table gives no test standard)
    status: ground
    source: wiki
    where: Infobox material properties table, row Thermal conductivity (austenite)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, martensite
    value: 0.086
    unit: W/cm·K
    scope: material
    conditions:
      phase: martensite
      composition: not stated
      temper: not stated
      unit_in_source: W/cm·K
    method: Typical value in the Wikipedia nickel titanium property table (secondary source; the table gives no test standard)
    status: ground
    source: wiki
    where: Infobox material properties table, row Thermal conductivity (martensite)
  - benchmark: cte
    label: Coefficient of thermal expansion, austenite
    value: 11
    unit: ppm/K
    scope: material
    conditions:
      phase: austenite
      unit_in_source: 11 × 10−6/°C
    method: Typical value in the Wikipedia nickel titanium property table; the printed unit 10−6 per °C equals ppm per K
    status: ground
    source: wiki
    where: Infobox material properties table, row Coefficient of thermal expansion (austenite)
  - benchmark: cte
    label: Coefficient of thermal expansion, martensite
    value: 6.6
    unit: ppm/K
    scope: material
    conditions:
      phase: martensite
      unit_in_source: 6.6 × 10−6/°C
    method: Typical value in the Wikipedia nickel titanium property table; the printed unit 10−6 per °C equals ppm per K
    status: ground
    source: wiki
    where: Infobox material properties table, row Coefficient of thermal expansion (martensite)
  - benchmark: elastic_modulus
    label: Elastic modulus, austenite
    value: 75
    value_high: 83
    bound: range
    unit: GPa
    scope: material
    conditions:
      phase: austenite
      unit_in_source: 10.9 × 10^6 to 12.0 × 10^6 psi
    method: Typical range in the Wikipedia nickel titanium property table (secondary source; no test standard printed)
    status: ground
    source: wiki
    where: Infobox material properties table, row Elastic modulus (austenite)
  - benchmark: elastic_modulus
    label: Elastic modulus, martensite
    value: 28
    value_high: 40
    bound: range
    unit: GPa
    scope: material
    conditions:
      phase: martensite
      unit_in_source: 4.1 × 10^6 to 5.8 × 10^6 psi
    method: Typical range in the Wikipedia nickel titanium property table (secondary source; no test standard printed)
    status: ground
    source: wiki
    where: Infobox material properties table, row Elastic modulus (martensite)
  - benchmark: yield_strength
    label: Yield strength, austenite
    value: 195
    value_high: 690
    bound: range
    unit: MPa
    scope: material
    conditions:
      phase: austenite
      temper: not stated
      unit_in_source: 28.3 to 100.1 ksi
    method: Typical range in the Wikipedia nickel titanium property table (secondary source; no test standard or temper printed)
    status: ground
    source: wiki
    where: Infobox material properties table, row Yield strength (austenite)
  - benchmark: yield_strength
    label: Yield strength, martensite
    value: 70
    value_high: 140
    bound: range
    unit: MPa
    scope: material
    conditions:
      phase: martensite
      temper: not stated
      unit_in_source: 10 to 20 ksi
    method: Typical range in the Wikipedia nickel titanium property table (secondary source; no test standard or temper printed)
    status: ground
    source: wiki
    where: Infobox material properties table, row Yield strength (martensite)
  - benchmark: poissons_ratio
    label: Poisson's ratio
    value: 0.33
    unit: '-'
    scope: material
    conditions:
      phase: not stated
    method: Typical value in the Wikipedia nickel titanium property table (secondary source)
    status: ground
    source: wiki
    where: Infobox material properties table, row Poisson's ratio
  - benchmark: martensite_transformation_stress
    label: Stress needed for the martensitic transformation
    value: 69
    value_high: 138
    bound: range
    unit: MPa
    scope: material
    conditions:
      phase: austenite to martensite under mechanical load
      temperature: not stated
    method: Range printed in the Wikipedia text on the martensitic transformation (secondary source); custom property name, see gaps
    status: ground
    source: wiki
    where: Section on the martensitic transformation, sentence beginning with the transformation requiring 69 to 138 MPa
  - benchmark: austenite_finish_temperature
    label: Austenite finish temperature Af, upper end of the printed range
    value: 110
    bound: upper
    unit: °C
    scope: material
    conditions:
      composition: varies with composition and processing
      note: range printed as about −20 to +110 °C; the lower end is not entered because the source writes it with a Unicode minus sign
    method: Upper end of the Af range printed in the Wikipedia composition section (secondary source); custom property name, see gaps
    status: ground
    source: wiki
    where: Composition section, sentence beginning with Transformation temperatures in nitinol can be controlled
  - benchmark: thermal_hysteresis
    label: Thermal hysteresis of the phase transformation
    value: 20
    value_high: 50
    bound: range
    unit: °C
    scope: material
    conditions:
      composition: depends on the precise composition and processing
    method: Typical range printed in the Wikipedia text on thermal hysteresis (secondary source); custom property name, see gaps
    status: ground
    source: wiki
    where: Thermal hysteresis paragraph, about 20 to 50 °C
corrosion:
  - environment: Physiological saline and buffer solutions, static, up to two years (nanostructured NiTi wire, laboratory)
    headline: Polishing cuts nickel release, and annealing weakens corrosion resistance.
    effect: Mechanical polishing reduced metal ion release by a factor of two to three, while annealing deteriorated corrosion resistance. Mechanically treated samples soaked in saline for two years formed a Ni-free surface with a protective 25 nm titanium oxide film.
    rating: moderate
    conditions:
      basis: long-term static immersion, two years
      material: nanostructured NiTi wire
      rating_note: assistant reading of the abstract; ion release still occurs
    source: pmc6915
    where: Abstract
  - environment: Heat-treated surface of medical nitinol, in tissue and body fluid
    headline: A thermal oxide layer of TiO2 acts as a barrier against nickel release.
    effect: During heat treatment nitinol forms a stable protective TiO2 layer that acts as a barrier against ion exchange, and nitinol releases nickel more slowly than stainless steel. A thicker oxide layer does not directly reduce nickel release in proportion.
    rating: low
    conditions:
      basis: medical device literature cited in the Wikipedia article
    source: wiki
    where: Nickel release paragraph in the Biocompatible and biomedical applications section
  - environment: In vivo, implanted medical device
    headline: In vivo corrosion can change the thermomechanical properties and the biocompatibility of a nitinol device.
    effect: FDA says the corrosion resistance of nitinol depends strongly on surface processing, and that in vivo corrosion may decrease the safety profile or performance of a device by adversely affecting thermomechanical properties or biocompatibility. The guidance gives no corrosion rate.
    rating: unknown
    conditions:
      basis: draft FDA guidance, no rate given
    source: fda
    where: Introduction, corrosion paragraph
risks:
  hazards:
    - text: 'Nitinol alloys SDS (2026): skin sensitisation Category 1 (H317, may cause an allergic skin reaction), carcinogenicity Category 2 (H351, suspected of causing cancer), STOT repeated exposure Category 1 (H372) and chronic aquatic hazard Category 1 (H410). Signal word Danger. Nickel is listed at 47.6 – 56 % by weight in the composition table.'
      ghs:
        - H317
        - H351
        - H372
        - H410
      source: sds-nitinol
      where: Sections 2 and 3, hazard statements and composition table
    - text: The same SDS says the product does not present hazards in its shipped form, and that downstream manipulation of the material gives the hazards listed.
      ghs: []
      source: sds-nitinol
      where: Section 2 hazard summary
  failure_risks:
    - mode: Fatigue cracking in flexed devices
      trigger: Repeated large strains, for example peripheral stents, heart valves and smart actuators
      consequence: Wikipedia says fatigue failures have been observed in the most demanding applications, although strain-controlled fatigue performance of nitinol is described as superior to all other known metals.
      severity: high
      source: wiki
      where: Fatigue section
    - mode: Inclusions in the alloy
      trigger: Melting and processing of nickel-titanium ingot
      consequence: Inclusions of TiC and Ti2NiOx occur in nitinol, and their size, distribution and type can be controlled only to some extent; the literature disagrees on how far they affect fatigue durability.
      severity: moderate
      source: wiki
      where: Fatigue and inclusions discussion
    - mode: Shift of the transformation temperature
      trigger: Small changes in nickel content, oxygen or carbon pick-up from titanium, or aging
      consequence: The transformation temperature changes significantly with small composition changes, and aging increases it by removing nickel from the matrix, so a part can stop behaving as specified.
      severity: high
      source: wiki
      where: Composition and Heat treatment sections
    - mode: Nickel release into tissue or solution
      trigger: A thin, damaged or annealed surface oxide
      consequence: Nickel is an allergen and a possible carcinogen; the saline study found that annealing weakened corrosion resistance and that polishing cut ion release two to three times.
      severity: moderate
      source: pmc6915
      where: Abstract
  side_effects: []
  handling:
    - text: Control the nickel to titanium ratio tightly, because small composition changes shift the transformation temperature.
      source: wiki
      where: Composition section
    - text: Treat the shipped product as not hazardous in that form, but expect H317, H351, H372 and H410 once it is processed, and follow the supplier SDS.
      source: sds-nitinol
      where: Section 2 hazard summary
  mitigations:
    - text: Mechanical polishing reduced ion release by a factor of two to three in the saline study.
      source: pmc6915
      where: Abstract
uses:
  - application: mechanisms
    device: Torque-tube actuators in nitinol 55 and nickel-titanium-palladium
    example: NASA Glenn Research Center vacuum plasma sprayed NiTi torque tubes and tested them in torsion, for actuation in aircraft and aerospace controls.
    source: glenn2008
    where: Abstract
  - application: structures
    device: Self-erectable and expandable structures such as antennas
    example: A NASA 1972 review says 55-Nitinol structures such as antennas could be compacted in a satellite during launch and later expanded to full size by solar energy.
    source: nasa1972
    where: Chapter on applications for 55-Nitinol, paragraph beginning with another type of application
supply:
  - subject: Nickel, world mine production 2025e (3,900,000 t; Indonesia 2,600,000 t, Philippines 270,000 t, Russia 200,000 t, New Caledonia 140,000 t); shares calculated by Space Mushroom from the printed tonnages
    abundance: World nickel reserves above 140,000,000 t (USGS 2026, reserves table)
    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
      - country: New Caledonia
        share_percent: 3.6
        year: 2025
    critical_lists: []
    recycling: 'USGS 2026: most secondary nickel was recovered as nickel in stainless-steel scrap, and most recycled nickel went into new alloys.'
    substitutes: []
    source: usgs-ni
    where: World Mine Production and Reserves table, columns 2024 and 2025e
  - subject: Titanium sponge metal, world production 2025e (370,000 t; China 260,000 t, Japan 53,000 t, Kazakhstan 16,000 t); shares calculated by Space Mushroom from the printed tonnages
    abundance: The United States did not produce titanium sponge in 2025; U.S. sponge imports in 2021 to 2024 came from Japan (77 %), Saudi Arabia (13 %) and Kazakhstan (8 %)
    producers:
      - country: China
        share_percent: 70.3
        year: 2025
      - country: Japan
        share_percent: 14.3
        year: 2025
      - country: Kazakhstan
        share_percent: 4.3
        year: 2025
    critical_lists: []
    recycling: 'USGS 2026: consumption data for titanium scrap are limited because voluntary surveys had few responses.'
    substitutes: []
    source: usgs-ti
    where: Domestic Production and Use, Import Sources, and World Sponge Metal Production table
documents:
  - title: 'Wikipedia: Nickel titanium (nitinol composition, phases, property table, fatigue and biomedical use)'
    type: database
    url: https://en.wikipedia.org/wiki/Nickel_titanium
  - title: 'NASA NTRS 19720022818: 55-Nitinol, the alloy with a memory (1972 review)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19720022818/downloads/19720022818.pdf
    year: 1972
  - title: ASTM F2063 Standard Specification for Wrought Nickel-Titanium Shape Memory Alloys for Medical Devices and Surgical Implants (store page)
    type: standard
    url: https://store.astm.org/f2063-26.html
  - title: Confluent Medical, Nitinol Tubing and Wire and Nitinol material page
    type: datasheet
    url: https://confluentmedical.com/capabilities/nitinol-material/
  - title: 'FDA draft guidance: Nitinol Technical Guidance (2019)'
    type: report
    url: https://www.fda.gov/media/123272/download
    year: 2019
  - 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: Titanium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf
    year: 2026
  - title: Resonetics safety data sheet, Nitinol Alloys (2026)
    type: sds
    url: https://resonetics.com/wp-content/uploads/2024/12/SDS-Nitinol-Alloys-6-23-2026.pdf
    year: 2026
  - title: Ion release and surface characterization of nanostructured nitinol during long-term testing (PMC6915401, 2019)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC6915401
    year: 2019
  - title: Spray forming of NiTi and NiTiPd shape-memory alloys (NASA NTRS 20080047469, 2008)
    type: paper
    url: https://ntrs.nasa.gov/api/citations/20080047469/downloads/20080047469.pdf
    year: 2008
gaps:
  - The Johnson Matthey nitinol technical properties page returned a 404 to the fetch tool, and its raw page held no property text, so no value was taken from Johnson Matthey in this run.
  - No UNS, EN, EN name, W.Nr., JIS or AMS designation for nitinol was printed in a source read in this run, so none is listed. The ASTM F2063 code and the SE508 and 55-Nitinol names are the only designations recorded.
  - Transformation temperatures Ms, Mf, As and Af at a stated composition and heat treatment were not read as table values; only the Wikipedia Af range (about −20 to +110 °C, upper end entered) and the hysteresis range are recorded.
  - No ultimate tensile strength, elongation, fatigue limit or superelastic strain value with a stated temper or form was read in this run; the Wikipedia yield figures are phase-based with no temper stated.
  - No atomic oxygen erosion, outgassing or flight result for nitinol was found in a source read in this run.
  - 'No corrosion rate in micrometres per year or nickel release in micrograms per square centimetre was extracted: the PMC Table 2 ion concentrations did not parse cleanly from the HTML.'
  - 'Critical-mineral list status for nickel and titanium was not confirmed: the USGS nickel text mentions critical minerals only in the context of an executive order on seabed minerals, and the titanium text gives no list.'
  - Torque, actuation force and transformation values from the NASA Glenn 2008 paper were not extracted; the paper was read as an abstract and as a use reference only.
  - 'Custom property names used because no canonical name exists: martensite_transformation_stress, austenite_finish_temperature and thermal_hysteresis.'
  - FDA Nitinol Technical Guidance read is a 2019 draft, not a final guidance.
  - Wikipedia property values are secondary and carry no test standard or temper; they are recorded as typical values.
sources:
  wiki:
    title: Nickel titanium (Nitinol), Wikipedia
    url: https://en.wikipedia.org/wiki/Nickel_titanium
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  nasa1972:
    title: 55-Nitinol, the alloy with a memory (NASA NTRS 19720022818, 1972 review)
    id: NTRS 19720022818
    url: https://ntrs.nasa.gov/api/citations/19720022818/downloads/19720022818.pdf
    year: 1972
    kind: report
    license: public domain (NASA)
  astm:
    title: ASTM F2063, Standard Specification for Wrought Nickel-Titanium Shape Memory Alloys for Medical Devices and Surgical Implants (store page, F2063-26)
    id: ASTM F2063-26
    url: https://store.astm.org/f2063-26.html
    kind: standard
    license: standard text not reproduced; abstract cited
  confluent:
    title: Confluent Medical, Nitinol Tubing and Wire (grades SE508, SE508 ELI, SE510)
    url: https://confluentmedical.com/capabilities/nitinol-material/
    kind: datasheet
    license: manufacturer web page (cited, not reproduced)
  fda:
    title: FDA draft guidance, Nitinol Technical Guidance (issued 19 April 2019)
    url: https://www.fda.gov/media/123272/download
    year: 2019
    kind: report
    license: US government work (cited, not reproduced)
  usgs-ni:
    title: Mineral Commodity Summaries 2026, Nickel (USGS, February 2026)
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-ti:
    title: Mineral Commodity Summaries 2026, Titanium (USGS, February 2026)
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  sds-nitinol:
    title: Safety data sheet, Nitinol Alloys (Resonetics, 29 CFR 1910.1200 format, 2026)
    url: https://resonetics.com/wp-content/uploads/2024/12/SDS-Nitinol-Alloys-6-23-2026.pdf
    year: 2026
    kind: datasheet
    license: manufacturer safety data sheet (cited, not reproduced)
  pmc6915:
    title: Ion release and surface characterization of nanostructured nitinol during long-term testing
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC6915401
    year: 2019
    kind: paper
    license: open access (cited, not reproduced)
  glenn2008:
    title: Spray forming of NiTi and NiTiPd shape-memory alloys (NASA Glenn, NTRS 20080047469)
    id: NTRS 20080047469
    url: https://ntrs.nasa.gov/api/citations/20080047469/downloads/20080047469.pdf
    year: 2008
    kind: paper
    license: public domain (NASA)
license: CC-BY-4.0
updated: '2026-10-25'
review:
  status: draft
  method: assistant
  checked_values: 16
  unreachable: 1
  caveats: 4
  note: 'Values were read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. Unreachable: the Johnson Matthey technical page. Caveats: Wikipedia property values are secondary and carry no temper or test standard; the Af upper bound is entered alone; the SDS nickel range is wide; the saline study is on nanostructured wire, not a standard grade.'
story:
  risk_groups:
    - title: For people
      lead: Nitinol is about half nickel, and the nitinol alloy SDS classes it with skin sensitisation and carcinogenicity codes. The hazard applies once the material is processed, not in its shipped form.
      level: 2
      verdict: Nickel-driven hazard
      points:
        - label: Codes on the SDS
          line: The nitinol alloys SDS lists H317 (allergic skin reaction), H351 (suspected of causing cancer), H372 (organ damage on repeated exposure) and H410 (very toxic to aquatic life), with nickel at 47.6 to 56 % by weight.
        - label: Shipped form
          line: The same SDS says the product does not present hazards in its shipped form, and that downstream manipulation brings the listed hazards.
    - title: If it fails
      lead: 'The sources name three failure routes: fatigue in flexed parts, inclusions in the alloy, and a shift of the transformation temperature with composition or aging.'
      level: 2
      verdict: Fatigue and composition
      points:
        - label: Fatigue
          line: Wikipedia says fatigue failures have been observed in the most demanding applications, such as heart valves and actuators, even though its strain-controlled fatigue performance is described as superior to other metals.
        - label: Composition drift
          line: Small changes in composition shift the transformation temperature, and aging raises it by taking nickel out of the matrix.
    - title: Handling and storage
      points:
        - label: Surface
          line: A polished surface released two to three times less metal ion in the saline study, while annealing weakened corrosion resistance.
        - label: Processing
          line: Titanium picks up oxygen and carbon in melting, which removes it from the NiTi lattice and shifts the transformation temperature.
  why: Nitinol is a nickel-titanium alloy that can be deformed, hold its shape, and recover it when heated, and that can spring back from large strains. Its austenite phase has an elastic modulus of 75 to 83 GPa, and its martensite phase 28 to 40 GPa, so the same alloy is stiff or soft depending on its phase. Its density is 6.45 g/cm3 at 25 °C for a 55.1 wt % nickel alloy, as the NASA 1972 review reports.
  uses:
    - where: Actuators
      line: NASA Glenn Research Center sprayed NiTi and NiTiPd torque tubes that were tested in torsion as actuators for aircraft and aerospace controls.
    - where: Deployable structures
      line: A NASA 1972 review describes self-erectable 55-Nitinol structures, such as antennas, that are compacted in a satellite at launch and expanded later by solar energy.
  can_do:
    - label: Recover its shape
      line: Heating through its transformation range restores the shape it was set in. The martensitic transformation needs 69 to 138 MPa of stress.
      value: 69 to 138 MPa
    - label: Carry heat
      line: Thermal conductivity is 0.18 W/cm·K in the austenite phase and 0.086 W/cm·K in the martensite phase, from the Wikipedia property table.
      value: 0.18 and 0.086 W/cm·K
    - label: Weight
      line: Density is 6.45 g/cm3 at 25 °C for the 55.1 wt % nickel alloy in the NASA 1972 review.
      value: 6.45 g/cm3
    - label: Stiffness
      line: The austenite modulus is 75 to 83 GPa, and the martensite modulus 28 to 40 GPa, a wide swing with phase.
      value: 75 to 83 GPa austenite
    - label: Phase change
      line: The austenite finish temperature runs from about −20 to +110 °C with composition, and thermal hysteresis is about 20 to 50 °C.
      value: −20 to +110 °C
  compare: 'The two phases differ the most in this record: austenite has 75 to 83 GPa modulus and 0.18 W/cm·K thermal conductivity, against 28 to 40 GPa and 0.086 W/cm·K for martensite. The rows below compare density, thermal conductivity and thermal expansion, read from the record.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Control the nickel to titanium ratio tightly, because small composition changes shift the transformation temperature.
    - Treat the shipped product as not hazardous in that form, but expect H317, H351, H372 and H410 once it is processed, and follow the supplier SDS.
    - Polishing reduces nickel release, while annealing weakens corrosion resistance in the saline study.
  good_for:
    - Shape-memory actuators and superelastic parts, with a 6.45 g/cm3 density and a 75 to 83 GPa austenite modulus.
    - Medical devices where the NASA and Wikipedia sources rate biocompatibility as high, such as catheters and stents.
    - Self-erectable structures that must fold for launch and expand in orbit, per the NASA 1972 review.
  watch_out:
    - 'Nickel: the alloy is about half nickel, and the SDS classes it with H317 and H351.'
    - 'Fatigue: failures have been observed in the most demanding applications.'
    - 'Composition sensitivity: the transformation temperature moves with small composition changes.'
    - No flight, outgassing or atomic-oxygen data for nitinol was found in this record.
  verdict: Nitinol is a nickel-titanium alloy whose shape memory and superelasticity come from a reversible phase change. Its density is 6.45 g/cm3, and its phases differ in stiffness, 75 to 83 GPa against 28 to 40 GPa. The record still lacks UNS and EN designations, tensile and fatigue values with temper, and space-environment data, so it is a draft.
  recipe:
    line: Nitinol is made by melting nickel and titanium ingot with no other intentional additions, under vacuum or an inert atmosphere (ASTM F2063 abstract). Vacuum arc remelting and vacuum induction melting are the two main methods (Wikipedia). Titanium is so reactive that oxygen or carbon pick-up takes titanium out of the lattice and shifts the transformation temperature (Wikipedia).
    parts:
      - name: Nickel
        symbol: Ni
        role: Sets the transformation temperature; typically about 50 to 51 atomic percent, or 55 to 56 weight percent, in the alloy (Wikipedia)
        share_percent: 54.5
        share_high: 57
        source: astm
        where: 'Abstract: nominally 54.5 % to 57.0 % nickel'
      - name: Titanium
        symbol: Ti
        role: Balance of the alloy; the reactive element that picks up oxygen and carbon during melting
        share_note: balance
        source: astm
        where: 'Abstract: no other intentional alloy additions'