Microstructure and corrosion behaviour of Cu-Al-Ni shape memory alloys with Ag nanoparticles

Abstract

In this study, the effect of silver nanoparticles on the transformation temperatures, microstructural and corrosion characteristics of the ternary Cu-Al-Ni shape memory alloys (SMA) was investigated. It was subsequently observed that the addition of Ag nanoparticles controlled the phase morphology and orientations of the parent phases, along with the formation of the Ag-rich precipitates. Furthermore, it was shown that the addition of Ag nanoparticles can affect the martensitic transformation temperature, due to the microstructure changes that are associated with the formation of intermetallic compounds and/or precipitates. The corrosion behaviour of the Cu-Al-Ni shape memory alloy with and without nano-Ag addition were investigated using electrochemical tests in a NaCl solution, and their results showed that the corrosion potential of Cu-Al-Ni-Ag (nanoparticles) SMA (-277.1 mVSCE) was nobler than the Cu-Al-Ni SMA. It was also shown that there is a decline in corrosion current density from 6.93 to 5.61 μA/cm2 after the addition of nano-Ag to Cu-Al-Ni SMA. The combination of SEM, together with EDX and XRD, also showed that the formation of the corrosion products silver chloride, cuprous oxide, aluminium oxide/hydroxide and silver oxide act as a protective layer and improve the corrosion resistance of Cu-Al-Ni-Ag SMA.