Effect of Worm‐Like Amorphous Phase on Corrosion Resistance and Antibacterial Properties of NiTiCu Alloy

ABSTRACT By adding CuO, the worm‐like amorphous phase and atomic clusters were simultaneously introduced, enabling the (Ni 40 Ti 40 Cu 20 ) 99.9 O 0.1 alloy micron columns to exhibit a uniform flow strain of over 40% and a strength of over 2.5 GPa during compression. As the oxygen content increases, both the dispersion degree and volume fraction of the amorphous phase decrease, while the content of the B19′ phase increases. Currently, shape memory alloys (SMAs) have been widely used in marine environments. However, the corrosion resistance behavior and mechanism of the SMA containing worm‐like amorphous phases developed in our work remain unknown. Through Tafel and EIS measurements, we demonstrated that the (Ni 40 Ti 40 Cu 20 ) 99.9 O 0.1 alloy with the highest amorphous content exhibits the lowest corrosion current density (0.928 μA cm −2 ), the highest corrosion potential (−598 mV), the highest polarization resistance (898,167 Ω m −2 ), and thus the best corrosion resistance. This phenomenon can be attributed to the fact that the passivation film of the (Ni 40 Ti 40 Cu 20 ) 99.9 O 0.1 alloy is the thickest (2.66 nm) and contains a large amount of dense oxides such as TiO 2 , NiO, and CuO. First‐principles calculations revealed that the density of states (DOS) of the amorphous phase is the lowest (41.56 eV), followed by that of the B2 phase (42.52 eV), and the B19′ phase has the highest DOS (44.623 eV). The worm‐like amorphous phase not only enhances the mechanical properties through heterogeneous deformation‐induced (HDI) strengthening by impeding dislocation movement but also shows the best corrosion resistance. The (Ni 40 Ti 40 Cu 20 ) 99.9 O 0.1 alloy exhibits antibacterial rates of 30.47% and 91.09% against Escherichia coli and Staphylococcus aureus , respectively.