Metal with Memory
People have memories. But it is not unusual for them to also have memories. If metals could remember, that would be incredible! This magic metal is known as “shape memories alloy”.
The shape memory alloy (SMA) is an alloy material that has a “memory”. It is able to remember its initial form and can also sense and drive at the same moment. It’s a type of intelligent material.
The shape memory alloy will return to its original state no matter how it deforms. The action of stress and temperature can cause it to undergo phase transition. It is most important material for 4D printing due to its unique shape memory effect, pseudo-elasticity, and other properties.
Once ordinary metal is formed into a spoon it will remain that way. You can twist the spoon using pliers but it will eventually become an inutilitarian pile of metal parts. However, spoons made of shape-memory alloy can be bent and heated to restore their original shape.
There are many types of shape-memory alloys that have been found around the world. However, Nitinol has been the first to be developed, and is still the most useful.
Martensite is the SMA material with two crystal structures, austenite. One is the SMA at a higher temperature and one is at a lower temperature. It is due to this transition from austenite to martensite that the “memory property” occurs (and vice-versa). Common materials for SMA are cu-Al-nickel, Nitinol and Nitinol. This refers to its element composition (Ni, titanium, and NOL, for Naval Weapons Laboratory).
Shape Memory Alloys – The Discovery
The discovery of SMA material properties is just one story. In the 1930s scientists began investigating the materials’ unusual properties. Arne Ollander (a Swedish Chemist) described a pseudo elastic phenomenon that was discovered in the study of gold-cadmium alloys. It wasn’t until 30 years after the accident that “shape memories alloy” became a term.
The U.S. began conducting metallurgical studies in the 1960s and 1950s. Naval Weapons Laboratory. William J. Buehler (scientist) was working on casting and melting nickel-titanium rods one day. As he waited for the rods cool down, he dropped one onto the concrete floor. He heard a dull sound. After thinking this strange, he dropped one hot nickel-titanium nitiadium stick onto the concrete floor. The sound sounded like a bell. Buehler began to worry that the casting was not going according to plan. He went to the cooler to put the hot nickel-titanium bar in cool water and then cooled it. After cooling the rod of nickel-titanium, Buehler dropped it to the ground. He heard again a dull click.
This was further confirmed during a meeting at the Naval Weapons Laboratory. Buehler’s assistant distributed thin strips of Nitinol, which had been bent like an accordion and stretched. After Dr. David S. Muzzey grabbed the bar, he lit a lighter on it and warmed it. After a quick unfolding, the bar returned to its original form. The properties and properties that Nitinol has at different temperatures was recognized by people who called it Nitinol.
Recent and future developments show that shape memory materials don’t have to be limited only to metals. Many other types of shape memory material, including shapes memory polymers, have been created and are being used commercially.
The use of the Shape Memory Alloy
It has an array of outstanding properties that allow it to be used widely in aviation, automotive industry and medical equipment. Recently, consumer electronics have also used shape memory materials. SMA can be found in mobile antennas, as well as the AUTOfocus component of smartphone cameras.
SMA can even be used for toys and crafts. For example, flexible bracelets are made of shape-memory materials, which allow you to bend and twist them until they return to their original form.
Shape Memory Alloys are the Future
According to the National Strategic Emerging Industries Plan and other supporting policies by the Central and Local Governments, the shape memory alloy industry is one the seven new industries. The state supports and encourages it.
With the continued development of shape memories alloy technology, as well as a lower cost and improved consumer acceptance policies, the use of shape memory alloy will grow in popularity.
(aka. Technology Co. Ltd. (aka. High purity, small particles size and low impurity are the hallmarks of Nitinol that our company produces. If you need a lower purity, please call us .