All data is for information only------(Home)
	PRODUCT DATA of Nitinol

Material

Nitinol

Product Datasheet

nitinol

General Information

Nitinol exhibits a unique phase transformation in the crystal structure when transitioning between the Austenite and Martensite phases. The Austenite phase being the high temperature, stronger state compared to the weaker, low temperature Martensite phase. The most common two terms used to describe this behavior are "Superelasticity" and "Shape Memory". Shape Memory occurs when a material is in its Martensitic (low temperature) phase and is deformed to a new shape. When the material is then heated above the Af temperature it changes back to Austenite and the deformation is lost as the material returns to its pre-deformed, original shape. Up to 8% shape recovery is possible. All nitinol exhibits BOTH superelastic and shape memory behavior. Alloy composition and the material's thermo-mechanical processing history dictate the temperatures where these properties exist. Austenite: Nitinol's stronger, higher temperature phase. Crystalline structure is body-centered cubic. Superelastic behavior is in the phase (over a 50-60C temperature spread). Martensite: Nitinol's weaker, lower temperature phase. Crystalline structure is twinned. Material easily deformed in this phase. Once deformed in martensite it will remain deformed until heated to austenite where it will return to its pre-deformed shape, i.e. "shape memory" effect.

Precautions

These values should only be used as guidelines for developing material specifications. Properties of Nitinol Alloys are strongly dependent on processing history and ambient temperature. The mechanical and superelastic properties shown here are typical for standard superelastic straight tubes at room temperature tested in uniaxial tension. Bending properties differ, and depend on specific geometries and applications. Modulus is dependent on temperature and strain.

Chemical Composition

53.5Ni-45Ti-1.5Fe

Name of Manufacturer

Nitinol Devices & Components 47533 Westinghouse Drive Fremont, California 94539 (510)683-2000 Fax: (510)683-2001 sales@nitinol.com www.nitinol.com

	PHYSICAL PROPERTIES

Specific Gravity

6.5

Phase changes

-200 to 110 °C Remark: Transformation Temperature

Magnetic Properties

Nonmagnetic

	ELASTIC PROPERTIES

Tensile Modulus

41 to 75 GPa Remark:Low value for martensite phase, while high value for austenite phase

Poisson Ratio

0.33

	MECHANICAL PROPERTIES

Ultimate Tensile Strength

800 to 1800 MPa Remark:Low value for martensite phase, while high value for austenite phase

Proof Stress (0.2%)

200 to 600 MPa Remark:Low value for martensite phase, while high value for austenite phase

Elongation

10 to 15 %

	ELECTRICAL PROPERTIES

Electrical Volume Resistivity

7.6e-7 to 8.2e-7 ohm.m

	THERMAL PROPERTIES

Thermal Expansion Coefficient

6.6 to 11 μstrain/°C Remark:Low value for martensite phase, while high value for austenite phase

Melting Range

1300 °C

	RELEVANT PROPERTIES FOR USE IN SPACE COMMUNITY

Machinability

Nitinol is a very abrasive material to machine due to its tough titanium oxide surface. Milling, turning, grinding are possible with excellent results but expect a lot of tool wear. Carbide tooling is highly recommended. During centerless grinding ensure adequate cooling lubricant is present. Nitinol can be EDM, water jet cut, and laser machined with excellent results.

Welding

Welding nitinol to itself is usually very effective if the weld is protected by an inert atmosphere and the heat effected zone is minimized. Laser, TIG, and resistance welding are all processes that have been successful. Nitinol welded to dissimilar metals, such as stainless steel, does not give acceptable results since the outcome is a brittle intermetallic interface which cannot be stress relieved.

Brazing

Brazing can only be accomplished after re-inforcement and plating

Soldering

Nitinol's tough oxide layer does not promote good solder wetting. An aggressive flux (Indium Corp. #2 flux) is required to remove the oxide, then a standard Sn-Ag solder can be used to attain good results.

Thermal Cycling

Thermal cycling both with or without applied load can result in degradation, such as shift in transformation temperature, reduction in available strain, changes in reset force and even to fracture.

	SPECIAL RECOMMENDATIONS

Special Recommendations

Nitinol can be bonded to other materials using epoxies and adhesives. Mechanical techniques such as crimping and swaging are possible. Another mechnical technique is to use nitinol's shape memory or superelastic properties to join materials. A nitinol tube connector can be expanded either mechanically or by cooling it to martensite than deforming it, inserted over another element, than allowing the connector to return to austenite and clamp down on the element. (cryofit connector)