Extension of the classical theory of crystallization to non-isothermal regimes: Application to nanocrystallization processes

• Published in: Journal of alloys and compounds 2012-12, Vol.544, p.73-81
• Main Authors: Blázquez, J.S., Borrego, J.M., Conde, C.F., Conde, A., Lozano-Pérez, S.
• Format: Article
• Language: English
• Subjects: Activation energy; Approximation; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallites; Crystallization; Deviation; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Exponents; Growth from solid phases (including multiphase diffusion and recrystallization); Heating rate; Johnson–Mehl–Avrami–Kolmogorov equation; Materials science; Methods of crystal growth; physics of crystal growth; Nanocrystalline materials; Nanocrystalline microstructure; Nanocrystals; Nanoscale materials and structures: fabrication and characterization; Phase transformation kinetics; Physics; Solid-solid transitions; Specific phase transitions; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.08.002

► Non-isothermal kinetics is easily analyzed using the present approach. ► Local Avrami exponents are obtained for nanocrystallization in a wide range. ► Results on nanocrystallization are explained in the frame of limited growth approach. ► Deviations from isokinetic behavior is analyzed for two different multiple processes. The non-isothermal kinetics of primary crystallization processes is studied from numerically generated curves and their predictions have been tested in several nanocrystallization processes. Single processes and transformations involving two overlapped processes in a non-isothermal regime have been generated and deviations from isokinetic behavior are found when the overlapped processes have different activation energies. In the case of overlapped processes competing for the same type of atoms, the heating rate dependence of the obtained Avrami exponent can supply information on the activation energies of each individual processes. The application to experimental data of nanocrystallization processes is consistent with a limited growth approximation. In the case of preexisting crystallites in the as-cast samples, predictions on the heating rate dependence of the obtained Avrami exponents of multiple processes have been confirmed.