Effects of Ti on the Thermal Stability and Glass-Forming Ability of Ni-Nb Glassy Alloy

Abstract

The thermal stability, glass-forming ability (GFA) and mechanical properties of the Ni₆₀Nb_40−xTi_x (x=0 to 40) glassy alloys have been investigated. As the Ti content increases, the supercooled liquid region ΔT_x (= T_x−T_g) and reduced glass transition temperature (T_g⁄T_l) increase, the maximum ΔT_x of 54 K and T_g⁄T_l of 0.622 are obtained at 22.5%Ti and 15%Ti, respectively, and then the ΔT_x and the T_g⁄T_l gradually decrease. The Ni₆₀Nb₂₅Ti₁₅ glassy alloy was formed in a rod form with a diameter up to 1.5 mm. The T_g and T_x of the bulk glassy alloy were 859 K and 906 K, respectively. The Vicker’s hardness (Hv), Young’s modulus (E), compressive fracture strength (σ_c,f) and compressive plastic elongation (ε_c,p) were 833, 167 GPa, 3085 MPa and 1.8%, respectively, for the bulk alloy. There is a tendency for fracture strength to increase with increasing glass transition temperature (T_g). It is therefore interpreted that the high strength is due to strong bonding nature among the constituent elements.