The scientists of the Laboratory of Physics of High-Strength Crystals of SPhTI have set the task of investigating the mechanisms of degradation and increasing the cyclic stability of the functional properties of new smart materials with magnetic shape memory effect. Recently, these studies have won a grant of the Russian Scientific Foundation. One of the ways to improve the properties, according to the scientists, can be the use of an effect such as the aging the alloy (holding it at a certain temperature).
- For ten years, our laboratory has been actively conducting research on single crystals of ferromagnetic alloys with thermoelastic martensitic transformations, - says Elena Panchenko, the project leader, Dr. Sci. in Physics and Mathematics - They have the unique ability to experience giant inelastic reversible deformations (change in body size) of up to 10% under the mechanical stresses in a wide temperature range up to 400° C, and also in a magnetic field.
One of the main factors restraining the wide application of these materials as actuating devices of repeated action in a variety of sensors and devices for vibration damping is the low cyclic stability of their functional properties. And in the framework of the project, scientists will study the stability of the reversible deformations of these materials under cyclic external influences.
- In the case of increasing the number of cyclic loads, - explains Elena Panchenko - there may be a functional degradation of the material, in which, first, the reversible deformation changes, that is, the sample does not recover its shape completely, and secondly, it can start to increase or decrease at other voltages, temperatures. Our task is to investigate the degradation mechanisms and to create materials with properties that will work for a long time.
The use this effect of alloy aging (exposure at a certain temperature) nanoscale particles are allocated that increase the strength properties of the crystals and cyclic stability. Typically the aging is carried out in a high temperature (austenite) phase. The project proposes to apply the aging under the load in a low-temperature (martensite) phase. Up to now it was believed that the stabilization of the martensite effects during the aging affects negatively the stability of the functional properties of these materials for the cyclic loads.
- However, there was an article by our partners from Germany last year, where they have shown that this method can be quite effective to create ferromagnetic materials with the desired properties. And as part of our project, we want to develop a methodology and test a new method of control of functional properties, based on aging under the load in the martensitic state, - says Elena Panchenko.