KINETIC CHARACTERIZATION OF AN AA8011 ALLOY NON-ISOTHERMALLY ANNEALED ABOVE 400ºC (CARACTERIZACIÓN CINÉTICA DE UNA ALEACIÓN AA8011 RECOCIDA NOISOTÉRMICAMENTE POR ENCIMA DE 400ºC)

CARACTERIZACIÓN CINÉTICA DE UNA ALEACIÓN AA8011 RECOCIDA NON-ISOTÉRMICAMENTE POR ENCIMA DE 400ºC

Abstract

Solid state reactions occurring in an Al-Fe-Si alloy are demonstrated through DSC measurements at temperatures above that of recrystallization, where Fe-rich precipitation phases coexist with processes of recrystallized grain growth. These complex reactions are deconvolved for analysis into individual reactions associated to each of the transformation mechanisms involved in the process. Symmetrically distributed Gaussian transfer functions (GTF) and asymmetric Weibull transfer functions (WTF) are used in the deconvolution; and each individual reaction is analyzed through both the Sesták –Berggren (SB) combined kinetic model and the isoconversional scheme, a linear regression determining each of the parameters. The study reflects the drawbacks of kinetic analysis based solely on the fitting of heat flow, as the patent dispersion of kinetic parameters clearly shows. This is corrected by adjusting the activation energy obtained by isoconversion methods. Three reactions are required when using GTF; whereas only two suffice when using WTF. The overall results show that reactions above 400°C occur primarily because of Fe diffusion, and that other reactions occurring in deformed samples have activation energies coinciding with energy diffusion at high-angle grain boundaries.