Glassy Ni-Ta-Ti-Zr(-Co) alloys with high thermal stability and high corrosion resistance

Glassy Ni-based alloys with high thermal stability and high corrosion resistance were synthesized in Ni-Ta-Ti-Zr(-Co) alloy system. Glassy Ni₆₀Ta_40-x-yTi_xZr_y alloys exhibit supercooled liquid region exceeding 50 K in a wide composition range and the largest supercooled liquid region of 67 K was obtained at Ni₆₀Ta₂₀Ti₁₅Zr₅. Glassy Ni₅₅Ta₂₀Ti₁₀Zr₈Co₇ alloy exhibits the highest thermal stability among the Ni-based glassy alloys reported up to date, which is evidenced by its high T_g and T_x of 899 K and 977 K, respectively, and a larger supercooled liquid region of 78 K. Bulk glassy Ni₅₅Ta₂₀Ti₁₀Zr₈Co₇ alloy in a rod form with a diameter of 1 mm can be prepared by copper mold casting. The glassy Ni-Ta-Ti-Zr(-Co) alloys are spontaneously passivated with low passive current density in 1 N H₂SO₄ and 1 N HCl solutions and their corrosion rate was less than 0.1 μm/year in the above solutions.