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Basic knowledge of nickel titanium memory alloy spring

wallpapers News 2020-05-07
In recent years, the application fields of shape memory alloys have been expanding. For example, nitinol has been made into a hydraulic system catheter of a jet fighter; a solid engine using low-quality energy; a foldable aerospace line in aerospace engineering; a dental orthodontic arch wire for medical use; a Hastelloy rod to correct the spine; Automatic contact, security device; thermal element on control, temperature switch; up to toys and daily necessities.

The development of metal springs has a long history, the earliest existence in the bronze age. With the development of human society, metal springs are active in people's daily life due to their toughness, torsion resistance, flexibility and long-term preservation. In the 14th century, precise timepieces made precision springs inevitable for the first time.

The advent of the industrial age in the eighteenth century made metal springs develop rapidly and rapidly. In modern times, the output of springs has risen sharply. Metal springs have also gradually evolved from the basic elastic functions possessed at the beginning and developed springs with different characteristics and uses.
 
The connection between metals is a metal bond. One metal can be reorganized and improved with another metal to derive new functions. For example, nickel-titanium alloy (NITI), which has a function that general springs do not have-shape memory function. Nitinol is a kind of shape memory alloy. The spring made of it can show different states under different water temperatures through the shape memory effect. If you put it in hot water, the length of the spring will immediately stretch, if you put it in cold water, it will immediately restore its shape.

The heat treatment of nickel titanium memory alloy is mainly developed around its thermoelastic martensite transformation. The meaning of shape memory effect is: some alloy materials with thermoelastic martensite phase change, in the martensite state, after a certain deformation or deformation-induced martensite, then in the subsequent heating process, when the temperature exceeds At the temperature at which the martensite phase disappears, the material can fully recover the shape and volume before deformation.
 
Martensitic transformation was originally found in steel and was studied as the basis of steel heat treatment technology; while the memory effect of shape memory alloys is generated by the thermoelastic martensitic transformation in the material. It has become the most important research topic in the field of martensite transformation, and opened up a new field of martensite application research. Now there are more than ten series of Ti-Ni, Au-Cd, Cu-Zn, Ag-Cd, Ni-Al, Co-Ni, Fe-Ni and so on. Martensitic phase transition is a solid phase transition, a phase transition caused by pseudo-shear causing short-range diffusion of atoms. Through the study of shape memory alloys, it is believed that only if the martensite transformation is thermoelastic and martensite belongs to a lattice structure with low symmetry, and the mother phase crystal has a cubic lattice structure with high symmetry, The memory effect is only when the conditions are orderly.


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Tag: nickel-titab   nitinol