Development trend and application of nickel-titanium alloy
Ni-Ti alloy, also known as memory alloy or SMA (Shape Memory Alloy), is a kind of metal material with shape memory ability, expansion rate of more than 20%, fatigue life up to 1 * 10 to the 7th power, damping characteristics than ordinary springs 10 times higher than its corrosion resistance is better than the best medical stainless steel, so it can meet the demand of all kinds of engineering and medical applications, it is a kind of Very excellent functional material. Under specific temperature conditions, it can show memory performance and super elasticity, and has the characteristics of biocompatibility, abrasion resistance and corrosion resistance, so it is widely used in aerospace, energy engineering and biomedical fields.
One
Material Characteristics
Nickel-titanium alloy its main material properties include the following aspects:
1, shape memory effect: this is the core characteristics of nickel-titanium alloy. Shape memory is when a certain shape of the parent phase by the Af temperature (nickel-titanium alloy phase transition temperature) above the cooling to the Mf temperature (martensitic transformation temperature) below the formation of martensite, will be martensite in the Mf below the temperature of deformation, by heating to the Af temperature below the accompanied by the inverse phase transition, the material will automatically restore its shape in the parent phase. In fact, the shape memory effect is a heat-induced phase transition process in Ni-Ti alloys.
2、Super elasticity: Nitinol has strong super elasticity, and its elasticity can reach 8%, which is much higher than that of common metal materials. This superelasticity makes Ni-Ti alloys able to undergo martensitic transformation when subjected to large stresses, from martensite to austenite, thus absorbing a large amount of energy and deformation, and when the stress is removed, it is able to return to the initial shape. Nickel titanium alloy demonstrates the super elasticity, so that it is widely used in the medical field.
3, wear resistance and corrosion resistance: nickel titanium alloy surface will form a layer of dense titanium dioxide (TiO2) oxide film, play the role of physical and chemical barriers, so that the nickel titanium alloy has excellent corrosion resistance, some studies show that the corrosion resistance of nickel titanium wire and stainless steel wire similar. Due to the superelastic and martensitic adaptive behavior of nickel titanium alloy, good strain hardening ability and fatigue resistance makes its wear resistance is higher than general materials.
4, biocompatibility: in terms of biocompatibility, compared with the clinical reference control material AISI 316L stainless steel, nickel titanium has no cytotoxicity, neurotoxicity, genotoxicity or allergenic, and nickel titanium stress - strain behavior is very similar to the bone and tendon, so the use of nickel titanium can shorten the healing time, reduce the trauma to the surrounding tissues and can be compatible with the human body tissues, will not cause obvious rejection or allergic reactions. This makes it safe to use in the manufacture of a variety of implants and medical devices, such as implants, stents, catheters and so on.
5, anti-toxicity: nickel-titanium shape memory alloy is a nickel-titanium equiatomic alloy, containing about 50% nickel, while nickel is known to have carcinogenic and cancer-promoting effects. Generally, the surface titanium oxide layer acts as a barrier to make the Ni-Ti alloy have good biocompatibility, and the surface layer of TixOy and TixNiOy can inhibit the release of Ni.
6, High Strength and Low Density: Ni-Ti alloy is characterized by high strength and light weight, able to provide sufficient strength while maintaining the light weight of devices and implants. This makes it useful in the manufacture of medical devices and implants that require strength and light weight.
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Application Areas
1. Biomedical field
Another important characteristic of NiTi is that its modulus of elasticity is as low as close to that of natural bone materials, and it has good biocompatibility and a unique stress/strain response, which makes its compressive strength higher than that of natural bone materials, and therefore it is widely used in a variety of biomedical applications, such as vascular stents and heart valves in medical devices, NiTi braces in orthodontics, and catheters in vascular interventional procedures.
2、Aerospace field
Due to its excellent mechanical properties and lightweight characteristics, nickel titanium alloy has been expanded in aerospace and defense applications, such as for wing regulators, fuel pipes and sensors and other key components. Nitinol is also used as a smart material in the aerospace field for adaptive structures, vibration damping systems and shape-variable components.
3、Smart materials and devices
Nitinol is used in the manufacture of flexible electronic devices, utilizing the flexibility and durability of Nitinol materials to make bendable displays and sensors.
III
Development trend
1、New alloy development
By adding other elements (such as silver, hafnium, tungsten, tantalum, etc.) to develop new NiTi alloys with better performance. There are related experiments to study the in vitro biocompatibility and corrosion behavior of NiTi-Ag intermetallic shape memory material, the corrosion resistance of nickel titanium will be significantly reduced in fluoride-containing saliva solution, and silver is known for its bactericidal properties, adding silver coating on a variety of bacteria has a good effect on the killing effect, so as to improve the corrosion and biocompatibility of nickel titanium. It has also been reported that NiTiTa has better corrosion resistance compared to NiTi.
2, ultra-pure nickel titanium materials research and development
Through the use of high-purity metallurgical processes, such as cold crucible induction melting (ISM) and electron beam melting (EBM), significantly reduce the impurity content of the alloy, improve the purity of nickel-titanium alloys, high-purity nickel-titanium alloys show a more excellent shape memory effect and superelasticity.
3、Composite material development
Nitinol and other high-performance materials (such as carbon fiber, ceramics) composite, the development of multifunctional composite materials, so that the material in the high temperature, high pressure and corrosive environments show more excellent performance.
Conclusion
The research progress and development trend of nickel-titanium alloy materials are mainly focused on improving their performance, expanding application areas and reducing production costs. Through the optimization of material composition, improvement of manufacturing process and development of new composite materials, the application prospect of Ni-Ti alloys will be broader.
One
Material Characteristics
Nickel-titanium alloy its main material properties include the following aspects:
1, shape memory effect: this is the core characteristics of nickel-titanium alloy. Shape memory is when a certain shape of the parent phase by the Af temperature (nickel-titanium alloy phase transition temperature) above the cooling to the Mf temperature (martensitic transformation temperature) below the formation of martensite, will be martensite in the Mf below the temperature of deformation, by heating to the Af temperature below the accompanied by the inverse phase transition, the material will automatically restore its shape in the parent phase. In fact, the shape memory effect is a heat-induced phase transition process in Ni-Ti alloys.
2、Super elasticity: Nitinol has strong super elasticity, and its elasticity can reach 8%, which is much higher than that of common metal materials. This superelasticity makes Ni-Ti alloys able to undergo martensitic transformation when subjected to large stresses, from martensite to austenite, thus absorbing a large amount of energy and deformation, and when the stress is removed, it is able to return to the initial shape. Nickel titanium alloy demonstrates the super elasticity, so that it is widely used in the medical field.
3, wear resistance and corrosion resistance: nickel titanium alloy surface will form a layer of dense titanium dioxide (TiO2) oxide film, play the role of physical and chemical barriers, so that the nickel titanium alloy has excellent corrosion resistance, some studies show that the corrosion resistance of nickel titanium wire and stainless steel wire similar. Due to the superelastic and martensitic adaptive behavior of nickel titanium alloy, good strain hardening ability and fatigue resistance makes its wear resistance is higher than general materials.
4, biocompatibility: in terms of biocompatibility, compared with the clinical reference control material AISI 316L stainless steel, nickel titanium has no cytotoxicity, neurotoxicity, genotoxicity or allergenic, and nickel titanium stress - strain behavior is very similar to the bone and tendon, so the use of nickel titanium can shorten the healing time, reduce the trauma to the surrounding tissues and can be compatible with the human body tissues, will not cause obvious rejection or allergic reactions. This makes it safe to use in the manufacture of a variety of implants and medical devices, such as implants, stents, catheters and so on.
5, anti-toxicity: nickel-titanium shape memory alloy is a nickel-titanium equiatomic alloy, containing about 50% nickel, while nickel is known to have carcinogenic and cancer-promoting effects. Generally, the surface titanium oxide layer acts as a barrier to make the Ni-Ti alloy have good biocompatibility, and the surface layer of TixOy and TixNiOy can inhibit the release of Ni.
6, High Strength and Low Density: Ni-Ti alloy is characterized by high strength and light weight, able to provide sufficient strength while maintaining the light weight of devices and implants. This makes it useful in the manufacture of medical devices and implants that require strength and light weight.
II
Application Areas
1. Biomedical field
Another important characteristic of NiTi is that its modulus of elasticity is as low as close to that of natural bone materials, and it has good biocompatibility and a unique stress/strain response, which makes its compressive strength higher than that of natural bone materials, and therefore it is widely used in a variety of biomedical applications, such as vascular stents and heart valves in medical devices, NiTi braces in orthodontics, and catheters in vascular interventional procedures.
2、Aerospace field
Due to its excellent mechanical properties and lightweight characteristics, nickel titanium alloy has been expanded in aerospace and defense applications, such as for wing regulators, fuel pipes and sensors and other key components. Nitinol is also used as a smart material in the aerospace field for adaptive structures, vibration damping systems and shape-variable components.
3、Smart materials and devices
Nitinol is used in the manufacture of flexible electronic devices, utilizing the flexibility and durability of Nitinol materials to make bendable displays and sensors.
III
Development trend
1、New alloy development
By adding other elements (such as silver, hafnium, tungsten, tantalum, etc.) to develop new NiTi alloys with better performance. There are related experiments to study the in vitro biocompatibility and corrosion behavior of NiTi-Ag intermetallic shape memory material, the corrosion resistance of nickel titanium will be significantly reduced in fluoride-containing saliva solution, and silver is known for its bactericidal properties, adding silver coating on a variety of bacteria has a good effect on the killing effect, so as to improve the corrosion and biocompatibility of nickel titanium. It has also been reported that NiTiTa has better corrosion resistance compared to NiTi.
2, ultra-pure nickel titanium materials research and development
Through the use of high-purity metallurgical processes, such as cold crucible induction melting (ISM) and electron beam melting (EBM), significantly reduce the impurity content of the alloy, improve the purity of nickel-titanium alloys, high-purity nickel-titanium alloys show a more excellent shape memory effect and superelasticity.
3、Composite material development
Nitinol and other high-performance materials (such as carbon fiber, ceramics) composite, the development of multifunctional composite materials, so that the material in the high temperature, high pressure and corrosive environments show more excellent performance.
Conclusion
The research progress and development trend of nickel-titanium alloy materials are mainly focused on improving their performance, expanding application areas and reducing production costs. Through the optimization of material composition, improvement of manufacturing process and development of new composite materials, the application prospect of Ni-Ti alloys will be broader.
