Selective Leaching and Surface Properties of Cu–Al–Ni Shape Memory Alloys

Abstract

This study investigated the selective leaching, chemical compositions, and electrochemical properties of CuXAl4Ni (X = 12.5, 13.0, and 13.5) shape memory alloys (SMAs). The selective leaching results showed that the CuXAl4Ni SMAs released approximately 200 ppb of Cu ions, 200 ppb of Al ions, and 600 ppb of Ni ions after immersion in Ringer's solution for 90 days. The low concentrations of Cu and Al ions stem from the oxidation of Cu and Al atoms near the surface of the CuXAl4Ni SMAs to form Cu 2 O and Al 2 O 3 films. The selective leaching properties of the CuXAl4Ni SMAs were inferior to that of the TiNi SMA, which possessed a highly passive TiO 2 film on the surface, but were much better than those of the TiNiCu and TiNiFe SMAs, whose TiO 2 films were deteriorated by the formation of NiO, Cu 2 O, and Fe 2 O 3 oxides. CuXAl4Ni SMAs are potential candidates to serve as biomaterials, owing to their acceptable surface and selective leaching properties, high martensitic transformation temperatures, low cost, good machinability, and excellent electric and thermal conductivities.

Effect of oxidation at an elevated temperature on the evolution of phases, microstructure, and properties of the oxide films formed on the surface of TiZr

“…This indicates that both the untreated and heat-treated TiZr alloys exhibited extremely low leaching rates for both Ti and Zr. The considered TiZr alloy exhibited better selective leaching properties than the Ti- and Cu-based shape memory alloys 28 – 31 and high-entropy alloys 32 , 33 reported in our previous studies.…”