Thermal stability and corrosion behavior of Ni-Ti(-Zr)-P glassy alloys

Ni₇₆Ti₅P₁₉ and Ni₇₃Ti₅Zr₃P₁₉ (at%) metallic glasses were prepared by a melt-spinning technique. Their thermal stability and corrosion behaviors were investigated, and the effects of Zr addition on the properties of the Ni-Ti-P glassy alloy were discussed. Results show that Zr addition increases the glass transition temperature (T_g) and crystallization temperature (T_x) of the Ni₇₆Ti₅P₁₉ glassy alloy, and decreases its supercooled liquid region (ΔT_x). Electrochemical tests in NaCl, HCl and H₂SO₄ solutions indicate passivation behavior of the Ni-Ti(-Zr)-P metallic glasses. Their good corrosion resistance can be attributed to the formation of a protective Ti/Zr- and phosphorus-rich layer on the surface of the alloys. Compared with Ni₇₆Ti₅P₁₉ glassy alloy, the Ni₇₃Ti₅Zr₃P₁₉ glassy alloy exhibits higher open-circuit potential and lower passive current density. Partially replacing Ni with Zr in Ni-Ti-P alloy introduces ZrO₂ in the passive film, which improves the protection of the surface film and results in a higher corrosion resistance.