They have the characteristics of high elasticity, metal rubber performance, high strength, etc. After plastic deformation under stress at a lower temperature, after heating, they return to the shape before heating. For example, Ni Ti, Ag Cd, Cu Cd, Cu Al Ni, Cu Al Zn and other alloys can be used for elastic elements (such as clutches, throttle valves, temperature control elements, etc.), thermal engine materials, medical materials (orthodontic materials), etc. of regulating devices.
The shape memory effect originates from a thermoelastic martensitic transformation. The general martensitic transformation, as a method of hardening steel, is to heat the steel to a certain critical temperature for a period of time, and then cool it quickly, such as directly inserting it into cold water (called quenching). At this time, the steel is transformed into a martensitic structure and hardened. Later, another so-called thermoelastic martensite transformation, which is different from the above, was found in some alloys. Once thermoelastic martensite is produced, it can continue to grow with the temperature decreasing. On the contrary, when the temperature rises, the grown martensite can shrink again until it returns to its original state, that is, the martensite can grow or shrink reversibly with the change of temperature. The shape of thermoelastic martensite changes with it.
In addition to the above categories of new metal functional materials, there are vibration damping alloys that can reduce noise; Biomedical materials that can replace, enhance and repair human organs and tissues; Intelligent materials that can implant sensors, signal processors, communication and controllers and actuators in materials or structures to enable materials or structures to have intelligent functions and life characteristics such as self diagnosis, self adaptation, and even damage self-healing.
