NiTi / Nitinol
metalnickel-titanium shape-memory alloy
NitinolNiTi50Ni50TiSMA Ti-NiShape Memory Alloy Ti-NiNickel TitaniumNi55Ti (wt%)
Composition — ASTM F2063 (wrought medical NiTi reference)
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Ni | 54.50 | 56.500 | 55–56 wt% Ni (≈50.6–50.9 at%). CRITICAL: every 0.1 at% Ni shift changes Af by ~10°C. Superelastic grade typically 50.6–50.8 at% Ni; shape-memory grades 49–50.5 at% Ni. Ni evaporates during LPBF — must measure Af post-build by DSC |
| Ti | — | — | balance — typically 44–45.5 wt% |
| C | — | 0.050 | TiC inclusions form with excess C; degrade ductility and transformation behaviour |
| O | — | 0.050 | Oxide inclusions (Ti₄Ni₂Ox) promote crack initiation — strict atmosphere control mandatory |
Mechanical & thermal properties — 2 conditions
| Property | LPBF as-built (XY) — superelastic | LPBF shape-set annealed (450–500°C / 15–30 min) |
|---|---|---|
| Elastic modulus | 40–60 GPa | — |
| Ultimate tensile strength | 850–1200 MPa | 750–1100 MPa |
| Elongation at break | 3.0–10.0 % | 5.0–12.0 % |
| Hardness (HV) | 240–330 HV10 | — |
| Density | 6.45 g/cm³ | — |
| Relative density | 98.0–99.7 % | — |
| CTE | 10.0–12.0 µm/m·K | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Always measure Af by DSC on representative coupons from each build — do not specify nominal transformation temperature without characterisation
- Control laser power to minimise Ni evaporation: lower power with reduced scan speed is often preferable to high-power rapid scanning for NiTi
- Design for electropolishing access: medical NiTi parts require electropolishing for surface Ni removal and Ra control — internal channels must be accessible
- Superelastic NiTi stores large elastic energy — design for safe deflection limits and avoid stress concentrations that could trigger sudden fracture beyond the plateau
- For shape-memory actuators: design the shape-set geometry (training cycle) before committing to final AM geometry — iterative process
- Minimum feature size for functional superelastic behaviour: walls thinner than ~0.3 mm may have compromised transformation behaviour due to surface oxidation effects
- Fatigue life: cyclic strain amplitude <1% is generally considered safe for long-term medical device use; LPBF NiTi data is still emerging
- Shielding gas: use argon (not nitrogen) — Ti reacts with N₂ forming TiN inclusions that embrittle the part and shift transformation temperatures
Advantages
- Unique shape-memory effect and superelasticity — no other metal provides ~8% recoverable strain
- Biocompatible — TiO₂ / NiO passive film; ASTM F2063 qualified for medical devices
- AM enables complex 3D shape-memory structures impossible in wrought processing (e.g. 3D lattice actuators)
- High damping capacity — useful for vibration attenuation in aerospace structures
- Self-expanding medical devices deployable through small catheter/introducer systems
- Corrosion resistance in biological environments comparable to 316L stainless steel
Limitations
- Composition is extremely sensitive — 0.1 at% Ni shift changes transformation temperature by ~10°C; LPBF Ni evaporation is a critical quality risk
- Mandatory DSC characterisation of Af/As/Ms/Mf temperatures on every build — cannot rely on nominal composition alone after LPBF
- Limited LPBF parameter databases — narrow process window; every platform requires independent validation
- High raw material cost — NiTi powder is significantly more expensive than Ti-6Al-4V
- Nickel content raises regulatory/biocompatibility questions for some applications — Ni ion release testing required per ISO 10993-15
- Post-processing complexity — shape-setting anneal, electropolishing, and DSC validation each add cost and lead time
- Fatigue life under cyclic loading is highly sensitive to LPBF porosity — CT scanning of every part recommended for life-critical medical use
- Limited to LPBF only — EBM and DED not yet established for NiTi due to composition control challenges in higher-temperature or wire processes
Typical applications
Medical stents (cardiovascular, peripheral, biliary) — superelastic self-expanding deploymentOrthodontic archwires — superelastic for constant-force tooth movement across large deflectionsEndoscopic and minimally invasive surgical instrumentsShape-memory actuators for aerospace morphing structures and deployable mechanismsAnti-vibration couplings and damping elementsLattice and auxetic structures for energy absorption (AM-specific)Orthopedic staples and fixation devices for bone fragment repairMicro-electro-mechanical systems (MEMS) and microactuators
Industries
medicalaerospaceindustrialconsumer
Compatible AM processes (1)
Other metal materials
Ti-6Al-4V Grade 5titanium alloy — alpha-betaTi-6Al-4V ELI (Grade 23)titanium alloy — alpha-beta (extra low interstitial)CP-Titanium Grade 2commercially pure titanium — alphaCP-Ti Grade 4titanium — commercially pure alphaTi-6Al-2Sn-4Zr-2Motitanium alloy — near-alpha316L Stainless Steelaustenitic stainless steel304L Stainless Steelaustenitic stainless steel17-4PH Stainless Steelmartensitic precipitation-hardening stainless steel15-5 PH Stainless Steelmartensitic precipitation-hardened stainless steel420 Stainless Steelmartensitic stainless steelAlSi10Mgaluminium-silicon alloy (cast grade adapted for AM)AlSi7Mg Aluminium Alloyhypoeutectic Al-Si-Mg precipitation-hardenable aluminium alloyScalmalloy®aluminium alloy — Al-Mg-Sc-ZrAlSi12aluminium — hypoeutectic/eutectic Al-SiInconel 718nickel superalloy — precipitation-hardenedInconel 625nickel superalloy — solid-solution-strengthenedInconel 939nickel superalloy — γ'-precipitation-hardened (high Al+Ti)Hastelloy® Xnickel superalloy — solid-solution strengthenedWaspaloy®nickel superalloy — γ'-precipitation-hardenedHaynes 282nickel superalloy — γ' precipitation-hardenedCoCrMocobalt-chromium alloy (biomedical and aerospace grade)Maraging Steel MS1 (18Ni-300)maraging steel (ultra-high-strength, precipitation-hardened)M300 Tool Steel (18Ni-300 Maraging Steel)maraging steel — tooling grade (ultra-high-strength, precipitation-hardened)H13 Tool Steelchromium-molybdenum hot-work tool steelCuCrZrcopper alloy — precipitation-hardenedCu-CP (Commercially Pure Copper)copper alloy — commercially pureCuSn10 (Bronze)copper alloy — tin bronzeGRCop-84copper alloy — dispersion/precipitation strengthenedInvar 36iron-nickel low-expansion alloy
Related calculators
LPBF Porosity PredictorPredict lack-of-fusion and keyhole porosity from laser parameters. Maps VED and normalised enthalpy to relative density and flags dangerous regimes.Powder Characterisation TrackerScore a powder batch against key qualification metrics — particle size distribution, flowability, apparent/tap density, moisture, and oxygen content.Surface Treatment SelectorRank post-print surface treatments (shot peening, electropolishing, tumbling, PVD, and more) against Ra target, material, fatigue criticality, and corrosion requirements.NDT SelectorSelect the right non-destructive testing method for your AM part. Inputs: material class, defect focus, geometry, production volume, and criticality. Ranked scorecard across CT, X-ray, UT, FPI, MPI, eddy current, and visual inspection with detection limits and standard references.Laser ParamsDerive LPBF process parameters from target VED and melt-pool stability constraints. Power–speed–hatch–layer sensitivity matrix with keyholing and balling risk zones.
Last reviewed: 2026-05-13 · v1 · Sources: elahinia-2016-niti-review, zhao-2019-niti-lpbf, nitinol-devices-niti-data-2022
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