志联

　　Shape memory alloy, due to its ability to recover its shape over a million times, is often called a ""living alloy."" Because it is a ""living alloy,"" its shape change at a certain temperature allows for the design of various self-regulating devices, and its uses are constantly expanding.

　　Mechanical Applications

　　Shape memory alloys have a wide range of applications. For example, in machinery: locking pins, pipe joints; in electronic instruments and equipment: fire alarms, connectors, integrated circuit soldering; in medicine: artificial heart valves, spinal correction rods, skull repair and reshaping, orthodontic treatment, and maxillofacial surgery. It will also play a magical role in communication satellites, color televisions, temperature controllers, and toys, and will become a new type of material in modern navigation, aviation, aerospace, transportation, and light textile industries. Shape memory alloys have been used in pipeline connections and automation control. Sleeves made of shape memory alloy can replace welding. The method involves expanding the pipe end by about 4% at low temperatures. During assembly, they are connected together. Once heated, the sleeve contracts and returns to its original shape, forming a tight connection. The US Navy's aircraft hydraulic systems use 100,000 of these connectors, and there have been no oil leaks or damage over the years. Repairing damaged pipelines in ships and offshore oil fields with shape memory alloy components is very convenient. In some areas where construction is difficult, pins made of shape memory alloy are inserted into holes and heated, and their ends automatically curl open, forming a one-sided assembly.

　　Medical Applications

　　The application of shape memory alloys in medicine is also noteworthy. For example, bone plates used for bone setting not only fix the two broken bone segments but also generate compressive force during the process of restoring their original shape, forcing the broken bones to join together. Orthodontic wires, clips for ligating cerebral aneurysms and vas deferens, and spinal straightening plates are all activated by body temperature after being implanted. A blood clot filter is also a new shape memory alloy product. After a straightened filter is implanted into a vein, it gradually returns to a net-like shape, preventing 95% of blood clots from flowing to the heart and lungs.

　　An artificial heart is a more complex organ. A combination of shape memory alloy myofibers and elastomer membrane ventricles can mimic ventricular contraction. Successful water pumping has been achieved.

　　Because shape memory alloy is a ""living alloy,"" its shape change at a certain temperature allows for the design of various self-regulating devices, and its uses are constantly expanding.

　　Aerospace Applications

　　The most encouraging application of shape memory alloys is in aerospace technology. On July 20, 1969, Apollo 11 landed on the moon, realizing humanity's dream of the first lunar landing. After landing on the moon, the astronauts placed a hemispherical antenna several meters in diameter on the moon to send and receive information to Earth. The several-meter-diameter antenna was packed into the small lunar module and sent into space. The antenna was made of shape memory alloy, which had only recently been invented. Extremely thin shape memory alloy material was prepared according to predetermined requirements under normal conditions, then its temperature was lowered and it was compressed into a ball, packed into the lunar module, and taken to space. After being placed on the lunar surface, the temperature increased under sunlight. When the transformation temperature was reached, the antenna ""remembered"" its original appearance and transformed into a large hemisphere.

　　More Applications

　　Currently, shape memory effect and superelasticity are widely used in various medical and daily life fields. Examples include blood clot filters, spinal correction rods, bone plates, artificial joints, women's bras, and artificial hearts. They can also be widely used in various automatic adjustment and control devices. Shape memory films and filaments may become ideal materials for future ultra-miniature manipulators and robots. In particular, its light weight, high strength, and corrosion resistance make it favored in various fields.

　　A NiTinol pre-shaped into an ""ICE"" shape, if accidentally damaged, will immediately return to its original shape after being immersed in hot water.

　　An alloy pre-shaped with half NiTinol and half titanium, slowly fired at 400 degrees Celsius for ten minutes, can permanently maintain this shape (at this time it is called the high-temperature austenite form).

　　The main reason is that during the slow heating process of its crystallization, each metal atom has sufficient time to fill each gap. At this time, its arrangement is the tightest. This alloy solid is commercially known as shape memory alloy. If a shape memory alloy is deformed due to any external factors (the arbitrarily deformable configuration is called martensitic), that is, gaps are created in the crystal shape, it can be filled by slightly heating it above the transformation temperature, that is, it will return to its original state. This process is called shape memory.

　　Shape memory metal spinal orthosis