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A thermodynamic study has been carried out on M-Si-B (M=Fe, Ni) ternary systems. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by using the experimental data. These parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. The amorphous-forming ability of M-Si-B ternary alloys has been evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies-Uhlmann kinetic formulations. For the computation, the time-temperature- transformation (TTT) diagram, which gives the time necessary for the formation of the detectable amount of crystal during transformation, was obtained at a finite temperature. The critical cooling rate for amorphization could be defined as the minimum cooling speed that does not intersect the TTT curve and, hence, these critical cooling rates enable us to evaluate the glass-forming ability of M-Si-B ternary alloys. The driving force for the crystallization of the crystalline phase was derived, on the basis of the thermodynamic functions of each phase formulated by the present study. The calculated results showed good agreement with the experimental data on the compositional range of amorphization in these alloy systems.
A thermodynamic study has been carried out on M-Si-B (M = Fe, Ni) ternary systems. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermomechanical parameters for each phase were evaluated by using the experimental data. These parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. The amorphous-forming ability of M-Si-B ternary alloys has been evaluated by introducing thermodynamic quantities For the computation, the time-temperature-transformation (TTT) diagram, which gives the time necessary for the formation of the detectable amount of crystal during transformation, was obtained at a finite temperature . The critical cooling rate for amorphization could be defined as the minimum cooling speed that does not intersect the TTT curve and, h The driving force for the crystallization of the crystalline phase was derived, on the basis of the thermodynamic functions of each phase formulated by the ence, these critical cooling rates enable us to evaluate the glass-forming ability of M-Si-B ternary alloys. present study. The calculated result showed good agreement with the experimental data on the compositional range of amorphization in these alloy systems.