What if I told you there were metals that could bend on their own. Would you believe me?
In fact, there are metals that can do just that: Shape-Memory-Alloys, or SMAs in short.
SMAs consist of two or more of the elements nickel(Ni), titanium (Ti), aluminum (Al), iron (Fe), zinc (Zn), copper (Cu), cadmium (Cd) and gold (Au).
What’s special about some of these alloys is that when they are heated to a certain point, depending on the alloy between room temperature and 400°C, they bend into their original form.
The first appearance of a SMA were recorded in Arne Φlander discovered the pseudoelastic behaviour of the Au-Cd alloy. The actual memory effect of these alloys was later discovered by both Kurdjumov and Khandros in 1949 and by Chang and Read in 1951.
The most popular of the SMAs is a Ni-Ti-alloy. It is prefered because of its high stability and superior thermo-mechanic performance, and was discovered in the United States Naval Ordnance Laboratory, when one of the staff, out of curiosity, held his lighter under one heavily bent piece of alloy, and watched in amazement as it returned to its original form.
The reason why SMAs have the ability to have this memory-effect is because of their special structure. All metals have a crystal-structure, but when they are bent, this structure changes irreversibly to adapt to the new form. SMAs change their structure,too, however in their case it is reversible. This process of returning to their original form can then be started by heating the alloy to its transition temperature.
The invention of SMAs has had a big impact on many industries. SMAs are used in medicine, planes, robotics, piping, telecommunications and many more. And there are many more ways that they can be used and improved, the possibilities are almost endless…
by Leon H.
Source: https://en.wikipedia.org/wiki/Shape-memory_alloy