The effect of substituting Nb for Zr on the glass forming ability (GFA) and mechanical properties of Ni60Zr27-xAl6Hf7Nbx (x = 0-14) alloys was investigated. The substitution of Zr with Nb of 0 14 at% improved the GFA. When increasing the Nb content x from 0-14, the glass transition temperature, T-g, and the crystallization temperature, T-x, of melt-spun Ni60Zr27-xAl6Hf7Nbx (x = 0-14) alloys increased from 833 and 863 K to 877 and 914 K, respectively. The Ni60Zr27-xAl6Hf7Nbx (x = 8, 10, 12 and 14) alloys exhibited high T-rg(= T-g/T-m(liq)) (> 0.615), gamma(= T-x/T-g + T-m(liq)) (> 0.4) values and a wide supercooled liquid region, Delta T-x(= T-x-T-g) (> 36 K) enabling the fabrication of bulk metallic glass (BMG) with a diameter above 1 mm. As such, Ni60Zr17Al6Hf7Nb10 and Ni60Zr15Al6Hf7Nb12 alloys with a maximum diameter of 2 mm could be fabricated by injection casting. These bulk amorphous alloys also exhibited good mechanical properties, where the true ultimate compressive strength, strain and Vickers hardness (H-v) were approximately 3.0 GPa, 2.08% and 713, respectively, for the amorphous Ni60Zr17Al6Hf7Nb10 alloy, and 3.1 GPa, 2.22% and 687, respectively, for the amorphous Ni60Zr15Al6Hf7Nb12 alloy. (c) 2006 Springer Science + Business Media, Inc.