2007 Volume 48 Issue 7 Pages 1635-1638
The glass-forming ability of Nb-Ni-Ti-Zr quaternary alloys has been evaluated by combining the Calculation of Phase Diagrams method with the Davies-Uhlmann kinetic approach. Time-temperature-transformation (TTT) curves were obtained for steady state nucleation for the calculations, which give the time required for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature. Then, the critical cooling rates for glass formation were calculated from the TTT curves. Among the input parameters for the calculation of the TTT curves, the driving force for crystallization of the crystalline phase was derived using the thermodynamic function of each phase formulated in previous studies. The calculations show that the critical cooling rates for Nb40−x−yNi60TixZry alloys decrease with increasing Zr content up to 20 mol%Zr. In particular, the calculated values for the Nb10Ni60Ti10Zr20 and Nb5Ni60Ti15Zr20 alloys were around 100 K/s.