Scientists have found an alloy with memory that can withstand millions of operating cycles

Prototype under microscope / BBC

In collaboration, scientists from the German Institute for Materials Science (Kiel) and the American University of Maryland at College Park demonstrated a memory alloy with unique characteristics. He is able to withstand up to 10 million work cycles without signs of "fatigue" of the material. The alloy is made of nickel, titanium and copper.

Alloys with memory, or with a shape memory effect , were discovered in the first half of the 20th century. Their property is that when heated, they take their original shape, even if in a cold state they were somehow deformed. Such properties are possessed by metal alloys, the classical compositions of which are nickel-titanium and copper-aluminum-nickel.
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There are also unidirectional and bidirectional memory effects. In the first case, after cooling, the material remains in the form that it took on heating. In the second, when it is cooled, it takes on the shape that was given to it in a cooled state, and when it is heated, it takes on its original form.

The shape change is facilitated by the internal structure of the crystal lattice, which experiences stress during deformation and is able to recover after heating.


General view of the prototype / BBC

Due to these properties, these alloys are often used as actuators , auxiliary fasteners, for medical purposes. They can replace moving parts of mechanisms that wear out and require lubrication. But all memory alloys have one common drawback - accumulating fatigue. After several tens, hundreds or thousands of heating-cooling cycles, internal damage is formed in the material, leading to its destruction.

Thanks to the combined use of nickel, titanium and copper, scientists managed to achieve such a good material structure that during the experiment that lasted several weeks, it changed the shape 10 million times without destruction. After the experiment, the structure of the experimental images was studied using powerful microscopes and X-rays.

Such endurance will allow the use of such alloys in hitherto impossible areas - from refrigerators without moving parts to parts of an artificial heart.