Nickel titanium alloy, a metal with memory

NiTi alloy is a kind of shape memory alloy. Shape memory alloy is a special alloy that can automatically restore its plastic deformation to its original shape at a specific temperature. It has good plasticity.

In addition to the unique shape memory function, memory alloys also have excellent characteristics such as wear resistance, corrosion resistance, high damping and super elasticity.

Performance and characteristics

（1） Phase Transformation and Properties of Ni Ti Alloy

As the name implies, NiTi alloy is a binary alloy composed of nickel and titanium. Due to the change of temperature and mechanical pressure, there are two different crystal structural phases, namely austenite phase and martensite phase. The transformation sequence of Ni Ti alloy during cooling is parent phase - R phase - martensite phase. The R phase is rhombic, and the austenite is in the state when the temperature is high or the load is removed, cubic and hard. The shape is relatively stable. The martensite phase is the state of relatively low temperature or loading, hexagonal, with ductility, repeatability, instability and easy deformation.

（2） Special properties of ni ti alloy

Shape memory characteristics: shape memory refers to that when the parent phase of a certain shape is cooled from Af temperature to Mf temperature to form martensite, the martensite is deformed below Mf temperature and heated to below Af temperature. With reverse phase transformation, the material will automatically restore its shape in the parent phase.

Hyperelasticity: The so-called hyperelasticity refers to the phenomenon that the specimen produces a strain far greater than its elastic limit strain under the action of external force, and the strain can recover automatically when unloading.

Sensitivity to temperature changes in the oral cavity: The correction force of stainless steel wire and CoCr alloy dental orthopedic wire is basically not affected by the temperature in the oral cavity.

Corrosion resistance: research shows that the corrosion resistance of nickel titanium wire is similar to that of stainless steel wire

Toxicity resistance: NiTi shape memory alloy has a special chemical composition, that is, it is an atomic alloy such as NiTi, containing about 50% nickel. Nickel is known to have carcinogenic and cancer promoting effects.

Soft orthodontic force: At present, commercially applied dental orthopedic wires include austenitic stainless steel wire, cobalt chromium nickel alloy wire, nickel chromium alloy wire, Australian alloy wire, gold alloy wire and nickel titanium alloy wire.

Good shock absorption characteristics: the greater the vibration caused by chewing and night grinding to the arch wire, the greater the damage to the root and periodontal tissue.

Shape memory:

NiTi shape memory alloy will automatically restore its shape after certain heat treatment, which is the shape memory feature of NiTi shape memory alloy.

Hyperelasticity:

NiTi shape memory alloy will deform when it is subjected to external force, and will return to the original state after removing the external force, which is the super elastic feature of NiTi shape memory alloy.

Damping:

NiTi shape memory alloy has damping property because of the self adjustment of phase transformation and the interface and movement generated in phase transformation.

Resistivity:

During the deformation of martensitic NiTi shape memory alloy, the relationship between resistance and strain is linear. When the transformation occurs, the slope of the curve will decrease accordingly, however, the linear relationship will also be maintained before and after the martensite phase.

Real time control: automatically output different elastic force according to the temperature change to reduce the contact resistance of the connector.

Energy saving: when the temperature of the re joint exceeds the gasket phase change temperature (43 ℃± 2 ℃), the contact resistance of the joint decreases by more than 10% compared with the traditional gasket joint, saving electric energy and avoiding accidents caused by overheating of the joint.

Durable: mechanical performance, corrosion resistance and service life are better than spring steel gasket.

Product technical principle

Initial state of smart gasket installation,

The state of the smart gasket after installation,

When the connector temperature exceeds the phase change temperature of the smart gasket, the gasket will automatically output greater elasticity, making the connector link more tight,

product mix

De: Outer diameter of gasket A. E: tolerance

Di: inner diameter of gasket Hl: height after deformation

T: Gasket thickness Ho: stroke

Schematic Diagram for Use of Structural Dimensions Schematic Diagram for Fastening Components of Memory Alloy Smart Gasket

1: Screw 2: nut 3: smart gasket

4: Connected conductor 5: flat gasket

1. It is applicable to all bolted circuit connection parts.

2. The pre tightening force is the same as that required for traditional fasteners of the same specification.