The CuAlNi alloy belongs to the so-called shape memory alloys. They are characterized by the fact that they return to their original shape after plastic deformation when the temperature is increased, because they remember the shape they had before deformation. The shape memory effect is made possible by the crystallographically reversible martensitic transformation between martensite (low-temperature phase) and austenite (high-temperature phase), which is associated with four characteristic phase transformation temperatures: on heating, there are the austenite initial (As) and austenite final (Af) temperatures, and on cooling, there are the martensite initial (Ms) and martensite final (Mf) temperatures.
The CuAlNi alloy is particularly interesting among shape memory alloys, not only because of its low manufacturing cost, but also because it is the only high-temperature shape memory alloy that allows applications at higher temperatures (up to 200 °C). However, its practical application is limited due to its difficult processing, its tendency to fracture and its low thermal stability.
In the bachelor's thesis, the influence of aging on the microstructure and characteristic temperatures of phase transformations of CuAlNi alloys was studied. The samples were prepared in the form of thin ribbons by the free-jet melt spinning method. The changes in the characteristic temperatures of the phase transformations were monitored by in situ measurements of the changes in electrical resistivity using the four-point U-I method. The microstructure of the samples before and after aging at different temperatures was observed by optical and scanning electron microscopes. We also performed EDS and XRD analyzes.
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