The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic function that is analyzed using Avrami kinetics. The analysis of the crystallization of Cu₄₇Ti₃₃Zr₁₁Ni₈Si₁ metallic glassy powders gives E_a = 3.8 eV, in good agreement with the calculation by other methods, and a transformation initiated by an accelerating nucleation and diffusion-controlled growth. The other studied alloy is a Nanoperm-type Fe₇₇Nb₇B₁₅Cu₁ metallic glass with a primary crystallization of bcc-Fe. An activation energy of E_a = 5.7 eV is obtained from the Master Curve analysis. It is shown that the use of Avrami kinetics is not able to explain the crystallization mechanisms in this alloy giving an Avrami exponent of n = 1.

The crystallization kinetics of glassy ${\mathrm{Fe}}_{65}{\mathrm{Nb}}_{10}{\mathrm{B}}_{25}$ melt-spun ribbons is studied by differential scanning calorimetry in the mode of continuous heating and isothermal annealing and by x-ray diffraction and transmission electron microscopy. Continuous heat treatments of the ribbons show the presence of multiple exothermic peaks before melting. The low-temperature peak corresponds to the precipitation of nanoscale ${\mathrm{Fe}}_{23}{\mathrm{B}}_6$-type crystalline metastable phase, and further annealing leads to its transformation into the metastable ${\mathrm{Fe}}_3\mathrm{B}$ phase and subsequent formation of $\mathrm{bcc}\text{−}\mathrm{Fe}$, ${\mathrm{Fe}}_2\mathrm{B}$, and FeNbB stable crystalline phases. The nucleation frequency and the growth rate are determined at selected temperatures from the analysis of the microstructures that emerge during the ${\mathrm{Fe}}_{23}{\mathrm{B}}_6$-type nanocrystallization. The master curve method is used to obtain the apparent activation energy and the Avrami exponent at the nanocrystallization onset. The nanocrystallization kinetics is explained in the framework of the Kolmogorov-Johnson-Mehl-Avrami theory. The rejection of insoluble alloy atoms during primary crystallization, the formation of diffusion layers around the crystals, and the decrease in the nucleation frequency caused by alloy enrichment of the residual disordered matrix is modeled through a soft impingement factor. Estimated values for the interfacial energy that provide a satisfactory agreement between experiments and modeling are derived considering that homogeneous nucleation frequency and interface-controlled grain growth are dominant at the onset of the nanocrystallization. Consequently, the time-temperature-transformation diagram is also drawn and the critical cooling rate estimated for this glass forming alloy.