Memory metal Why does the shape memory effect occur

Memory metal is also called shape memory alloy, which has the function of "remembering" shapes.

The mystery of memory metal "memory" lies in the fact that it can be its own metal part within a certain temperature range, and has a special reversible structural change. When the memory metal is subjected to a strong external force, the metal atoms inside will temporarily leave their original positions, migrate to and temporarily stay in the adjacent positions, so that the metal changes shape; If the deformed metal is heated, the metal atoms gain energy and at the same time, under the action of the binding force of the original structure, they return to their original position, and they return to their original shape.

For childhood is the best time period for children to learn, children's education should be cultivated from an early age, cultivating children's intelligence and memory. Of course, animals also have a certain amount of intelligence and memory, but why do some alloys also have the same magical "memory" ability as humans? It's impossible for non-living beings to have this ability, so let me answer your questions.

In 1963, the U.S. Navy Ordnance Laboratory needed some nitinol wire for an experiment, and the alloy wire they brought back was all curved. For ease of use, they straighten these twisted filaments one by one and use them. In subsequent experiments, a strange phenomenon appeared:

When the temperature rises to a certain value, these alloy wires, which have been straightened, suddenly and magically quickly return to their original twisted shape, and they are exactly the same as the original shape. After repeated experiments, the result is the same every time, as long as the straightened alloy wire reaches a certain temperature, it will immediately return to its original curved appearance. It is as if they have been changed shape when they are "frozen" and unconscious, and when the temperature rises to a certain value, they suddenly "wake up" and "remember" their original appearance, so they desperately return to their "original appearance".

Later, scientists discovered that other alloy systems, such as gold-cadmium, copper-nickel, copper-aluminum, copper-zinc, and iron-manganese alloys, also had a similar "memory" ability to "never forget the original", so they gave them a nice name - shape memory alloys. In addition to memory alloys, scientists have found a similar memory effect in ceramics and named them shape memory ceramics.

Shape memory alloy not only has a single "memory" ability of almost 100%, that is, to restore to the exact same shape as the original, but also because this "memory" ability will not produce the slightest fatigue or fracture even if it is repeated more than 5 million times. Why is that?

It turns out that after the general metal material is subjected to external force, it will undergo elastic deformation, reach the yield point, produce plastic deformation, and leave permanent deformation after the pressure is eliminated. However, some alloys, after plastic deformation, are in an unstable structure inside, and as long as they are heated to a certain temperature, they will be transformed into the original stable structure. This phenomenon is called the shape memory effect.

With the in-depth research of shape memory alloys by scientists, new uses of this amazing material in many fields such as mechanics, electronics, chemicals, aerospace, energy and medical care are constantly being developed.

Memory metal is a special metal material that can recover its original macroscopic shape after plastic deformation in a certain temperature range.