Characterization of CuAlNi based shape memory alloys and investigation of their magnetic effects

Shape memory alloys are one of the most important classes within the group of smart materials and one of the most widely used types. Shape memory effect and superelasticity are the two most fascinating properties of shape memory alloys, distinguishing them from traditional alloy systems. In shape memory alloys, the material undergoes shape recovery, primarily due to solid phase transformations occurring within the material. They are widely used in industrial fields such as aerospace, automotive, and medical applications. In this study, five different alloys were created by incorporating metallic elements Ga, Hf, Nb, V, and Ti onto the Cu-Al-Ni reference sample. The materials were characterized through various thermodynamic, structural, and magnetic analyses. The study revealed that V and Ti have a more effective grain refining effect compared to other alloying elements, while Hf showed less influence. Due to the high martensitic transformation temperatures observed in all quaternary alloys produced, each alloy was classified as a high-temperature shape memory alloy. It is understood that there is a correlation between grain size and transformation temperatures, where decreasing grain size leads to an increase in transformation temperature, which is supported by the V-doped alloy sample. Moreover, it was observed that V and Ti elements increased the transformation temperatures in the respective samples. The V-doped alloy exhibited the strongest martensitic transformation among other alloy examples, whereas the addition of Ga to the CuAlNi-based alloy reduced these values in the opposite direction. Additionally, it was observed that the measured microhardness values of the materials increased with grain refinement. Considering the atomic radii of Ga and Hf elements, it was noted that the hysteresis value increased compared to other alloying elements. The samples exhibited paramagnetic behavior at room temperature.