Cast supealoyCobalt based alloyPrecision alloySUPER ALLOY
Refractory metal
Titanium & Zirconium alloy
Sputtering taget
Nitinol Nickel-Titanium Shape Memory Alloy
1. Product Overview
Nitinol is an intermetallic functional material composed of nickel and titanium in a near-equiatomic ratio; its name is derived from Nickel, Titanium, and the Naval Ordnance Laboratory, where it was discovered. Nitinol (nickel-titanium shape memory alloy) is a metallic functional material that can recover 6%–8% strain without permanent deformation. It combines the shape memory effect and superelasticity with corrosion resistance, high damping, weak magnetic properties, and good biocompatibility (medical grade), and is widely used in minimally invasive medical devices, aerospace pipe couplings, thermostatic actuation, and elastic parts for consumer electronics.
Shape memory effect (SME): deformation at low temperature is followed by automatic recovery of the original shape when heated above the transformation temperature.
Superelasticity (SE): when used above the transformation temperature, it can withstand elastic strain far beyond that of conventional metals and spring back completely, resisting kinking.
Typical product forms include wire, bar, tube (including ultra-thin-wall capillary and hypotube), plate, strip, foil, as well as pre-shaped springs, actuation elements, and custom memory-alloy parts made to drawing.
Quick Reference Table
Item | Content | ||
Material category | Nickel-titanium shape memory alloy (NiTi / Nitinol) | ||
Core properties | Shape memory effect · Superelasticity · Corrosion resistance · High damping | ||
Available forms | Wire · Bar · Tube · Plate · Strip · Foil · Custom shaped components | ||
Industries served | Medical devices · Aerospace · Automotive · Consumer electronics · Robotics | ||
Recoverable strain | Tensile strength of medical wire | Customized Af range | High-cycle fatigue life |
6%–8% | ≥1070 MPa | −30 ~ +100 °C | 10⁷ order of magnitude |
Superelastic, recoverable | Typical acceptance criteria | Standard tolerance ±5 °C | High-cycle cycling |
2. Chemical Composition
Chemical composition requirements (ASTM F2063 framework)
Element | Content requirement (wt%) | Element | Content requirement (wt%) |
Ni | 54.5–57.0 | Fe | ≤ 0.050 |
Ti | Balance | Co | ≤ 0.050 |
C | ≤ 0.040 | Cu | ≤ 0.010 |
O | ≤ 0.040–0.050 | Cr | ≤ 0.010 |
N | ≤ 0.005 | Nb | ≤ 0.025 |
H | ≤ 0.005 | Inclusion area fraction | ≤ 2.8% |
Note on nickel sensitivity: a change of about 0.1 at% in Ni content can shift Af by more than ten degrees Celsius. This is why grade classification and the melting composition window must be tightly controlled. |
3. Grade and Transformation Temperature Selection
Selecting a grade essentially means selecting a transformation temperature. The table below lists commonly used binary NiTi grades with their reference transformation temperature ranges, together with the corresponding Af values under the ASTM F2063 alloy code system, for reference during selection.
(1) Common domestic grades
Reference transformation temperatures of common binary NiTi grades
Grade | Transformation temperature range | Type | Typical applications |
TiNi-01 | 20 °C – 40 °C | Shape memory | Temperature control elements, actuators, general memory parts |
TiNi-02 | 45 °C – 90 °C | Shape memory | High-temperature overheat protection, thermal switches |
TiNi-SS | 5 °C – 15 °C | Superelastic | Room-temperature superelastic structural parts, eyeglass frames |
TiNi-03 | < 5 °C | Superelastic (low temperature) | Superelastic parts for low-temperature environments, cold chain and outdoor equipment |
TiNi-YY (medical) | 33 °C ± 3 °C | Superelastic | Implants used at body temperature, orthodontic archwires |
TiNiCu | As−Ms ≤ 5 °C | Narrow-hysteresis memory alloy | High-frequency response actuators, thermal switches |
TiNiNb | As−Ms up to 150 °C | Wide-hysteresis memory alloy | Pipe couplings, fasteners (stored at room temperature, assembled by heating) |
(2) ASTM F2063 alloy codes
Correspondence between alloy codes and Af after heat treatment
Code | Af (°C) | Code | Af (°C) |
A | 70 ± 10 | E | 5 ± 10 |
B | 30 ± 10 | J | −30 ± 10 |
S | 25 ± 5 | K | 30 ± 10 |
C | 17 ± 7 | L | −20 ± 10 |
D | 10 ± 10 | — | — |
Examples of mechanical property classification: code D (tensile strength ≥1300 MPa, upper plateau ≥480 MPa), code C (≥1150/≥440 MPa), code S (≥1000/≥400 MPa); elongation is ≥10% and residual strain <0.5% in all cases.
4. Key Performance Parameters
Note: the values below are typical references; actual values vary significantly with minor composition adjustments, processing history, heat treatment condition, and test temperature. For medical implant grades, ASTM F2063 and the supplier's material certificate (MTC) apply. |
(1) Physical properties
Typical physical properties of Nitinol
Item | Typical value | Remarks |
Density | 6.45–6.5 g/cm³ | Between those of titanium and stainless steel |
Melting point | Approx. 1310 °C | Melting must be carried out under vacuum |
Electrical resistivity | Approx. 76 µΩ·cm (martensite) / approx. 82 µΩ·cm (austenite) | Physical basis for Joule-heating actuation |
Elastic modulus | 28–41 GPa (martensite) / approx. 75–83 GPa (austenite) | Lower apparent modulus on unloading, for a softer feel |
Coefficient of linear thermal expansion (CTE) | 6.6×10⁻⁶ /°C (martensite) / approx. 11×10⁻⁶ /°C (austenite) | Verify when joining to dissimilar materials |
Thermal conductivity | Approx. 8.6 W/(m·K) (martensite) / approx. 18 W/(m·K) (austenite) | Relatively low thermal conductivity; control heat input during cutting and welding |
Specific heat capacity | Approx. 0.32 J/(g·K) | Fast response for Joule-heating actuation |
Latent heat of transformation | Approx. 20–25 J/g | Affects the thermal response time of actuators |
Magnetic properties | Weakly magnetic / essentially non-magnetic | Better imaging compatibility than iron-containing alloys |
Damping characteristics | About 10 times that of ordinary spring steel | Suitable for vibration-damping and shock-resistant components |
(2) Mechanical properties
Room-temperature mechanical properties in the superelastic state (reference per ASTM F2063)
Item | Typical value |
Tensile strength | ≥ 1000–1300 MPa (common for medical superelastic wire ≥1070 MPa) |
Elongation at break | ≥ 10% |
Upper plateau stress (loading plateau) | ≥ 400–480 MPa (graded by alloy code) |
Recoverable strain | 6%–8% (single-cycle memory recovery strain ≤ 8%) |
Residual deformation after 6% strain | Commonly ≤ 0.3% (tighter control for higher-grade products) |
Constrained recovery stress | Approx. 500–800 MPa |
Fatigue life | Up to the 10⁷ order of magnitude (strongly dependent on strain level and surface condition) |
5. Available Forms and Specification Range
Nitinol available forms, specifications, and surface conditions
Form | Common specifications | Surface condition | Typical applications |
Round wire (straight / coil) | φ0.013 mm – φ7.0 mm | Black oxide, bright, ground, electropolished | Guidewires, orthodontic archwires, braided stents, actuation wire |
Bar | φ3 mm – φ50 mm (customizable) | Turned, ground | Orthopedic implants, machining blanks |
Tube / hypotube | OD 0.15 mm – 12 mm, wall thickness 0.02 mm – 1.0 mm | Bright, electropolished | Stent mother tube, interventional catheter shaft, delivery systems |
Plate / strip / foil | Thickness from 0.05 mm, width as required | Pickled, cold-rolled bright | Thermal control plates, etched parts, spring contacts, SIM card trays |
Shaped components | Springs, rings, plates, and wire parts | Per drawing requirements | Actuators, thermal control valves, orthopedic components |
Nitinol round wire diameter tolerance reference (ASTM F2063 system, mm)
Diameter range | Tolerance | Diameter range | Tolerance |
4.000 – 2.000 | ± 0.020 | 0.260 – 0.150 | ± 0.005 |
2.000 – 1.000 | ± 0.010 | 0.150 – 0.080 | ± 0.004 |
1.000 – 0.350 | ± 0.010 | 0.080 – 0.050 | ± 0.003 |
0.350 – 0.260 | ± 0.007 | 0.050 – 0.013 | ± 0.002 |
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