Effect of Nb addition on the glass forming ability and mechanical properties in the Ni-Zr-Al-Hf-Nb alloys

Abstract

The effect of substituting Nb for Zr on the glass forming ability (GFA) and mechanical properties of Ni₆₀ ${\rm Zr}_{27-x}$Al₆Hf₇ ${\rm Nb}_{x}$ (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, ${\rm T}_x$, of melt-spun Ni₆₀ ${\rm Zr}_{27-x}$Al₆Hf₇ ${\rm Nb}_x$ (x = 0 -- 14) alloys increased from 833 and 863 K to 877 and 914 K, respectively. The Ni₆₀ ${\rm Zr}_{27-x}$Al₆Hf₇ ${\rm Nb}_x$ (x = 8, 10, 12 and 14) alloys exhibited high $T_{rg}\, ({{{ = T_{g}}/{T_{ m}\,^{{ liq}}}}})$ (>0.615), $\gamma ({{{ = T_{\rm x}} / T_{\rm g} + T_{\rm m}^{{\rm liq}}}})$(>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.