Application of improved analytical model for non-isothermal phase transformation

Abstract

For the transformations with different overall effective activation energies occurring at different transformation temperatures, the effect of initial transformation temperature T0 has been quantitatively studied. Consequently, a guideline for selecting a proper model (analytical model or improved analytical model) to describe the transformation kinetics was given. For transformations with low overall effective activation energy occurring at high temperature, the terms involving T0 cannot be neglected, and the application of the improved analytical model is indispensable. The second crystallisation stage of amorphous Ti50Cu42Ni8 alloy as measured by differential scanning calorimetry was described by the improved analytical model. On this basis, the prevailing mechanisms of the transformation can be described as follows: mixed nucleation (combination of site saturation and continuous nucleation), interface controlled growth and impingement mode due to random nuclei dispersion. Reasonable kinetic parameters of the transformation were determined, especially the nucleation and growth activation energies (i.e. QN = 233 kJ mol−1 and QG = 288 kJ mol−1).