The shape memory alloy is an alloy material which can completely eliminate other deformations occurring at a lower temperature after heating and recovering the original shape before deformation. The earliest report on shape memory effects was made in 1952 by Chang and Read et al. They observed the reversibility of the phase transition in the Au-Cd alloy. The same phenomenon was found in the Cu-Zn alloy, but it did not attract widespread attention. It was not until 1962 that Buehler and his collaborators observed a memory effect with macroscopic shape changes in an equiatomic ratio Ti-Ni alloy, which attracted the attention of the scientific community and industry. In addition to its use in the construction sector, this new functional material is now widely used in the fields of electronics, automotive, medical devices, space technology and energy development.

 

Medical aspects:

Ni-Ti alloy is a leader in medical biomaterials and is widely used in clinical medicine and medical devices. For example, in interventional therapy, various types of human body cavity stents can be placed in various narrow parts such as human blood vessels, digestive tract, respiratory tract, and urethra through a small cavity after pre-compression and denaturation. The inside supports a narrow cavity. The utility model has the advantages of reliable curative effect and convenient use, and can greatly shorten the treatment time and reduce the cost. Traditional orthopedic surgical instruments include bone plates, screws, and wires. During the operation, the doctor has to perform complicated operations such as drilling, wedging, and bundling, which inevitably causes human damage to the patient's body. When operating with a shape memory alloy orthopedic device, the doctor first uses a low temperature (0-5 degrees Celsius) sterile saline to cool the memory alloy machine, and then changes the shape of the cohesive part as needed to be installed in the patient's bone injury site. When the patient's body temperature heats it to the set temperature, the deformed part of the instrument returns to the original designed shape, thereby merely tying the injured bone to fix and support. The use of the alloy surgery not only has the advantages of simple operation, shortened time and healing period, excellent biocompatibility, reduced human damage, etc., and its strength is four times that of stainless steel, and no bending or fracture occurs. The thrombus filter is also a new memory alloy product. Once the straightened filter enters the vein, it gradually returns to its shape, preventing 95% of the clots from flowing to the heart and lungs.