NiTi / Nitinol

metal

nickel-titanium shape-memory alloy

NitinolNiTi50Ni50TiSMA Ti-NiShape Memory Alloy Ti-NiNickel TitaniumNi55Ti (wt%)

Density

6.45 g/cm³

UTS (LPBF as-built (XY) — superelastic)

850–1200 MPa

Elongation (LPBF as-built (XY) — superelastic)

3.0–10.0 %

Elastic modulus

40–60 GPa

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

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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	—

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

NiTi / Nitinol

Composition — ASTM F2063 (wrought medical NiTi reference)

Mechanical & thermal properties — 2 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Compatible AM processes (1)

Other metal materials

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