Effect of Y Element on the Properties of Cu-Al-Ni High Temperature Shape Memory Alloy

Cu-Al-Ni alloys are not yet widely used due to issues related to their coarse grains, unacceptable plasticity, and poor thermal stability. Here, the physical and mechanical properties, as well as the corrosion behavior, of Cu-Al-Ni alloys doped with Y element (Cu-13Al-4Ni-xY (x = 0.2, 0.5, mass fraction, %)) were studied. XRD, OM, SEM, TEM, electronic universal testing machine, and electrochemical workstation were used to characterize the microstructures and measure the properties of the Cu13Al-4Ni-xY alloys. The results showed that at room temperature, the microstructure of Cu-13Al-4Ni-xY alloys was mainly an 18R martensite matrix. The (Cu, Al, Ni) 4Y second phase was characterized to have a hexagonal structure. The mechanical properties of the Cu-13Al-4Ni-xY alloys improved as the Y element content increased. For example, when the Y content was increased from 0% to 0.5%, the compressive fracture strain increased from 10.5% to 19.3% and the fracture strength increased from 580 to 1185 MPa. Additionally, the fracture type of the alloy changed from intergranular to transgranular with the addition of Y. Finally, the results from electrochemical experiments showed that the corrosion behavior of the alloys decreased slightly with the addition of Y.