Shape memory alloys (SMA) are materials composed of two or more metal elements that have shape memory effect (SME) through thermoelasticity and martensitic phase transition and its inversion. Shape memory alloys are the materials with the best shape memory properties among shape memory materials. So far, more than 50 kinds of alloys with shape memory effect have been found. There are many successful examples of applications in the aerospace field. The huge antennas on artificial satellites can be made of memory alloys. Before launching the satellite, the parabolic antenna will be folded up and loaded into the satellite body, and after the rocket lifts off and sends the satellite to the predetermined orbit, it only needs to be warmed up, and the folded satellite antenna naturally unfolds due to the "memory" function, restoring the parabolic shape.

Shape memory alloy has a shape memory effect (shape memory effect), to memory alloy made of spring, for example, put this spring in hot water, the spring length immediately elongated, and then put into cold water, it will immediately return to its original state. The use of shape memory alloy springs can be used to control the water temperature of the bathroom plumbing: when the hot water temperature is too high, through the "memory" function, the water supply pipe is adjusted or closed to avoid scalding. It can also be made into fire alarm devices and insurance devices for electrical equipment. When a fire occurs, the spring made of memory alloy deforms and starts the fire alarm device to achieve the purpose of alarm. The spring made of memory alloy can also be placed in the valve of the heater to keep the temperature of the heater, and when the temperature is too low or too high, the valve of the heater will be opened or closed automatically. The shape memory effect of shape memory alloys is also widely used in various types of temperature sensor triggers.

Another important property of shape memory alloys is pseudoelasticity (pseudoelasticity), also known as superelasticity, which is manifested in the fact that under the action of external forces, shape memory alloys have a much larger deformation recovery ability than general metals, i.e., the large strains generated during the loading process will be recovered as they are unloaded. This property has been commonly used in medicine and shock absorption in buildings as well as in daily life. For example, the artificial bones mentioned earlier, bone fixation pressurizers for injuries, and dental orthodontic devices. Eyeglass frames made from shape memory alloys can withstand much larger deformations than ordinary materials without damage (and are not restored by applying the shape memory effect, which occurs when deformation occurs and is then heated).