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.