High-Temperature Transformation Processes in Cu-13.4Al-5Ni Shape Memory Alloy Single Crystals

Abstract

Cu-13.4Al-5Ni alloy single crystals were investigated after performing the corresponding heat treatments to reveal the formation of equilibrium α and γ2 phases and to examine transformation processes occurring in the alloy during heating-cooling cycles between room temperature and 970 K. Transformation processes were examined using heat flux DSC, structure examinations were performed using optical microscope and SEM devices, and phase identifications were carried out by XRD method. Identification of the equilibrium α phase using XRD method was not possible on the single crystal samples. According to the results, the equilibrium phases (α and γ2) form only after long-term heat treatments. Because of that, aging processes do not affect the thermoelastic martensitic transformation of the CuAlNi alloy. This phenomenon is probably caused by the high Ni content that decreases the diffusion rate in CuAlNi alloys.