Formation, corrosion behavior, and mechanical properties of bulk glassy Zr–Al–Co–Nb alloys

Bulk glassy Zr₅₅Al_20–xCo₂₅Nb_x (x = 0 to 5 at.%) alloys with critical diameters of 2.5–5 mm and supercooled liquid region of 48–75 K were produced by copper-mold casting. These alloys were spontaneously passivated in 3 mass% NaCl and 1 N H₂SO₄ solutions. The addition of Nb to the alloy enhanced the pitting corrosion resistance in the NaCl solution and enabled the open-circuit potential in the H₂SO₄ solution. Zr- and Al-enriched passive films formed on the bulk glassy Zr–Al–Co–Nb alloys exposed to air and on those immersed in the solutions. The increase in Nb content of the alloys resulted in an increase in Zr and Nb concentrations and a decrease in Al concentration of the passive film. The Vickers hardness, Young's modulus, compressive fracture strength, fracture strain, and plastic strain of the bulk glassy Zr–Al–Co–Nb alloys were 550, 98 GPa, 2100 MPa, 2.9%, and 0.9%, respectively.