Examination of the Cu-13,4Al-5Ni Shape Memory Alloy

Cu based shape memory alloys exhibit relatively high transformation temperatures and low price compared to the other shape memory alloy systems. In spite of their advantages, their brittle behavior and ageing processes limits their applications. To increase ductility, Mn and Fe were added to the CuAlNi alloy. To examine the effect of the Mn and Fe addition and to characterize the ageing processes, the base Cu-13,4Al-5Ni alloy was investigated. After performing the needed heat treatments on the single crystal samples, equilibrium (α and γ₂) and non-equilibrium (martensite) phases and transformations were also examined on the alloy. Transformation processes were examined using heat flux DSC, structure examinations were performed using optical microscope and SEM devices, 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. Texture examinations revealed the textured structure of the α phase. According to the results the equilibrium phases (α and γ₂) form only after long term heat treatments. Because of that, ageing processes do not affect the thermoelastic martensitic transformation of the CuAlNi alloy. This phenomena is probably caused by the high Ni content that decreases the diffusion rate in CuAlNi alloys.