Effects of Ti on the thermal stability and glass-forming ability of Ni-Nb glassy alloy

The thermal stability, glass-forming ability (GFA) and mechanical properties of the Ni60Nb40-xTix (x = 0 to 40) glassy alloys have been investigated. As the Ti content increases, the supercooled liquid region DeltaT(x) (= T-x - T-g) and reduced glass transition temperature (T-g/T-l) increase, the maximum DeltaT(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 DeltaT(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 Tg and T. of the bulk glassy alloy were 859 K and 906 K, respectively. The Vicker's hardness (Hnu), Young's modulus (E), compressive fracture strength (sigma(e.f)) and compressive plastic elongation (epsilon(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.