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Shape-memory alloys

Shape-memory alloys are metals that, even if they become deformed at below a given temperature, they will return to their original shape before deformation simply by being heated. Alloys with this unusual characteristic are used as functional materials in temperature sensors, actuators, and clamping fixtures.

These metals also have a quality called superelasticity; like rubber, when it is bent or stretched, it will return to its original shape when the deforming force is removed. This characteristic of recovering shape despite substantial deformation is exploited in applications in products for daily life, in electrical and electronic appliances, and in the medical field.

There currently are several dozen types of alloys with such shape-memory properties and superelasticity, but Ni-Ti alloys have the best shape-recovery performance, durability, and corrosion-resistance.
Born of our wealth of titanium and titanium alloy melting and fabrication technology, KTS-SM alloy is one of the most reliable of the Ni-Ti alloys of this type of shape-memory and superelastic alloys.

Characteristics

Shape-memory alloys and superelastic alloys

The shape-memory effect and superelasticity are the result of thermo-elastic martensitic transformation, in which the shape-memory effect is expressed as phase transformation and reverse transformation from the parent phase (austenite) to and from the martensite phase. Superelasticity is expressed as stress-induced transformation from the parent phase to a martensite phase due to load stress in the parent phase state, and then as reverse transformation when unloaded.

Typical behaviors are explained below using a stress-strain curve:

  • Normally, metallic materials have a proportional relationship to deformation stress within the elastic range, but begin to yield when further deformed beyond the elastic range. After entering the yielding range, permanent deformation remains even after the strain is removed.
  • Even with the shape-memory effect, when the martensite phase is deformed in a low temperature phase, the deformation apparently remains beyond the yielding range even when unloaded, just as in normal metals. However, when heated above the transformation temperature, the strain is nullified and the shape returns to the original state, returning the alloy to the parent phase state.
  • In superelasticity as well, yielding occurs just as with normal metals, but when the load is removed, the material returns to its original shape in a phenomenon that is the reverse or that occurring under load. NiTi superelastic alloys will return to their original shape even when deformed under a nominal strain of around 8%.

Basic characteristics of KSM-SM alloy

Density 6.4～6.5 [g/cm3]
Specific heat 0.3 [kJ / (kg・K)]
Electric resistance 0.5～1.1 [10-6Ω・m]
Thermal Conductance 21 [W / (m・K )]
Linear expansion coefficient 10 [10-6 / K]
Modulus of transverse elasticity Martensite phase 5～10 [GPa]
Austenite phase 15～25 [GPa]
Young's modulus Martensite phase 15～30 [GPa]
Austenite phase 50～70 [GPa]
Hardness Martensite phase 180～300 [Hv]
Austenite phase 300～400 [Hv]
Rupture stress Martensite phase 700～1000 [MPa]
Austenite phase 1200～1500 [MPa]
Elongation Martensite phase ～30 [%]
Austenite phase ～20［％］

Metal alloys

We have prepared a line of KTS-SM alloys according to their shape-memory and superelasticity characteristics.

Effect Metal alloys Transformation temperature
(℃)		 Recoverable strain
(%)		 Temperature
hysteresis
(℃)		 Temperature
Cycle
Properties		 Application examples
Shape Memory Effect NiTi
NiTi-Co		 -20～70 1 2～3 ＞1,000,000 Sensor actuator
(Long life cycle)
NiTi-Cu 40～80 5～6 10～15 ＜50,000 Sensor actuator
(Large stroke)
NiTi -10～100 6～8 20～40 ＜100 connectors
Couplings
Superelasticity NiTi
NiTi-Co,V,Cr		 − 6～8 − − Various spring elements

Features of KSM-SM alloy

Substantial shape-memory, recoverable strain

Substantial shape-memory and recoverable strain.

Superb corrosion resistance

These alloys have superb corrosion resistance and wear resistance that is nearly equivalent to those of titanium and titanium alloys. They also have vastly superior wear resistance to wear-resistant materials such as titanium and nickel alloys.

Quality assurance through our integrated manufacturing system

We aspire to a total quality control system through an integrated manufacturing system from melting the parent material to the final treated shape-memory product.

High-precision device design

We can use our accumulated database to consult with customers to meet their needs from device design through prototyping.

Diverse shapes

We can provide a variety of diverse shapes, including round wire, square wire, ultrafine wire (from φ0.02mm), ribbon, coil springs, and 3D shapes.

Ultrafine wire
Ultrathin sheets
Wire
Various springs

Explore

KSM-SM alloy fields of application

  Shape-memory alloys Superelastic alloys
Consumer electronics Coffee makers Mobile phone antennas
Industrial machinery Pipe seams, fire dampers  
Household equipment Mixing water faucets, gas water heaters, water regulator valves,
subfloor vents, hot water shutoff valves for water purifiers		  
Transport machinery and equipment Evaporative emission control systems  
Personal accessories   Brassiere underwires, eyeglass frames,
shoulder pad wires, petticoats, accessories
Medical equipment Dental implants Orthodontic braces wire, Guide wires
Hobbies Toys Spinner lures, fishing through-wire
Eyeglass frames

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