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Introduction of shape memory alloy

wallpapers News 2020-05-08
Shape memory alloys (SMA) are materials composed of two or more metal elements that have a shape memory effect (SME) through thermoelastic and martensitic transformation and their inversion. Shape memory alloy is the best shape memory material among shape memory materials. So far, it has been found that there are more than 50 alloys with shape memory effect, the most common is nitinol. There are many successful examples of applications in the aerospace field. The huge antenna on the artificial satellite can be made of memory alloy. Before launching the artificial satellite, the parabolic antenna is folded into the satellite body. After the rocket is lifted to send the artificial satellite to the predetermined orbit, it only needs to be heated. The folded satellite antenna naturally expands due to the "memory" function and restores the parabolic shape.

Shape memory alloy (shape memory alloy) has a wide range of applications in the field of clinical medicine, such as artificial bones, bone fixation pressurizers, dental orthodontics, various types of intraluminal stents, embolizers, heart repair devices, thrombosis filters , Interventional guide wires and surgical sutures, etc., memory alloys are playing an irreplaceable role in modern medicine. Memory alloys are also closely related to our daily lives.

In 1932, Swedelande first observed the "memory" effect in gold-cadmium alloys, that is, after the shape of the alloy was changed, once heated to a certain transition temperature, it could magically change back to the original Shape, people call this alloy with this special function shape memory alloy. The development of memory alloys has only been more than 20 years so far, but due to its special effects in various fields, it is gaining attention in the world and is known as "a magical functional material".

In 1963, Biller of the U.S. Naval Ordnance Research Institute discovered in a research work that a nitinol wire was fired into a spring in a certain temperature range higher than room temperature, and then straightened in cold water or Cast into square, triangle and other shapes, and then put in hot water above 40 ℃, the alloy wire will return to the original spring shape. Later, it was discovered that some other alloys also have similar functions. This type of alloy is called shape memory alloy. Each shape memory alloy composed of a certain element and a certain weight ratio has a transition temperature; above this temperature, the alloy is processed into a certain shape, and then cooled to below the transition temperature, and the shape is changed artificially. When heated above the transition temperature, the alloy will automatically return to its original shape processed above the transition temperature.

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Tag: shape memory   nitinol