Thermal Stability and Devitrification Behavior of Ternary Ni-Nb-Ti and Quaternary Glassy Alloys Containing Noble Metals

Abstract

The devitrification of Ni₆₀Nb₂₅Ti₁₅ glassy alloy has been investigated by X-ray diffraction (XRD), differential scanning and isothermal calorimetry and transmission electron microscopy (TEM). The primarily crystallized phase was a cubic Ni(Ti,Nb) phase with a lattice parameter of 0.293 nm. A Ni₃Nb phase follows precipitation of the Ni(Ti,Nb) phase. The cubic Ni(Ti,Nb) phase undergoes partial transformation to Ni₄Ti₃ phase. These cubic Ni(Ti,Nb) phases disappear at the equilibrium conditions.
The supercooled liquid region (ΔT_x) of the Ni₆₀Nb₂₅Ti₁₅ glassy alloy was extended to 64 K with the addition of Pt. The Ni₅₅Nb₂₅Ti₁₅Pt₅ glassy alloy rods with diameters up to 2 mm were formed by mold casting. Pt and the other noble metals additions do not alter devitrification of Ni₆₀Nb₂₅Ti₁₅ glassy alloy.