They are characterized by high elasticity, metallic rubber properties, and high strength. After being plastically deformed under stress at a lower temperature, they undergo heating and return to the shape they were in before they were heated. Such as Ni-Ti, Ag-Cd, Cu-Cd, Cu-Al-Ni, Cu-Al-Zn and other alloys, can be used to adjust the device's elastic components (such as clutches, throttle valves, temperature control elements, etc.), thermal engine Materials, medical materials (orthodontic materials), etc.
The shape memory effect results from a thermoelastic martensitic transformation. The general martensitic transformation is used as quench hardening method for steel. It is to heat the steel to a certain critical temperature for a certain period of time and then cooled rapidly. For example, it is directly inserted into cold water (called quenching). At this time, the steel turns into a The structure of the martensite and hardens the steel. Later, in some alloys, another so-called thermoelastic martensitic transformation, different from the
above, was found. Once thermoelastic martensite is produced, it can continue to grow as the temperature decreases. On the contrary, when the temperature rises, the grown martensite can be reduced until it returns to its original state, ie, martensite can reversibly grow or shrink with temperature. The thermoelastic martensitic transformation is accompanied by a change of shape.
In addition to the above-mentioned categories, new metal functional materials include vibration-damping alloys capable of reducing noise; biomedical materials that substitute, enhance, and repair human organs and tissues; and implant sensors, signal processors, and communications in materials or structures. With controllers and actuators, smart materials such as self-diagnosis, self-adaptation, self-healing and even self-healing intelligent functions and vital characteristics are used for materials or structures.