Rus Articles Journal

Whether can remember metals? Telling

about mechanical properties of metals, it is necessary to stop on the alloys possessing shape memory. One of such alloys - nitinol, containing 55% of nickel and 45% of the titan. It is for the first time made in 1962, but its unique properties were found later, several years later.

It became clear that nitinol possesses interesting feature - so-called thermal shape memory. The detail from this alloy “remembers“ a form which it had when heating to a certain temperature and, being cooled and deformed, reproduces this form when heating to “memorable“ temperature.

If to heat a wire from this alloy to temperature of 90-150 degrees, to bend in a heated state, to cool and straighten (to flatten out, bend otherwise, to stick in knot), then at repeated heating to temperature about 70 degrees it will spontaneously restore a form which it had in an initial heated state.

The effect of shape memory is based on phase transformations in the set range of temperatures.

Nature of change of a form of the product received at deformation of a wire from the alloy possessing shape memory depends on heating temperature. If consistently to heat a wire to various temperatures, every time deforming it in a special way, then to cool, straighten and again to heat, then at a certain temperature it will take the corresponding form.

Shape memory also some other alloys, for example silver with cadmium or zinc possess. Interesting feature of these alloys is their ability to be painted when heating in red color, and coloring disappears at slow cooling and remains at sharp training.

The effect of shape memory is found also in manganese alloys with iron and silicon, manganese with copper and manganese with nickel, gold with cadmium, zirconium with palladium and in tens of other alloys.

There are many interesting offers of use of a nitinol and other alloys with effect of shape memory: the self-fixed rivets, forelocks, the self-straightened antennas it is the Most pertinent to apply them to space stations, the thermorelay, etc.

in places, access to which is complicated. Alloys with shape memory use in various areas, including astronautics, electronics, medicine today. They favourably differ from thermobimetals as work already at minor change of temperature.

Tension developed by the alloy seeking to take the initial form when heating can reach 1000 MPas. Therefore it is expedient to apply alloys with shape memory to raising of heavy freights or to direct transformation of thermal energy in mechanical, for example, in special engines.

Alloys with shape memory can find curious application in automotive industry: if to manufacture the case of the car, for example, of a nitinol, then even after strong deformation as a result of accident an initial form of the case it is easy to restore it, its heating.

So, metals, which - that is remembered. Also remember very well. As not so long ago it became clear, similar properties also some polymers possess. But about it later. You monitor publications.

And now I suggest you to think where still it is possible to apply clever materials with shape memory. Dare!