Understanding the recrystallization kinetics in aluminium alloy billets with poorly developed cast structure

Abstract

The paper describes the study of structure evolvement in A0 aluminum and 8011 and 8006 aluminum alloy billets with a low degree of the cast structure working when rolled at 300–500 °C and 3–8 s–1 strain rate. The grain structure was studied by optical microscopy with Axiovert 40 MAT microscope, intermetallic particles analysis was made using JEOL 6390A scanning electron microscope. Grain structure analysis showed that a dendritic structure gradually stretching in the direction of strain is observed in the cast state. Review of the effect of deformation modes and subsequent annealing on the grain structure helped obtain analytic equation to describe recrystallization kinetics. The effect of the Zener-Hollomon parameter value on recrystallization kinetics during subsequent annealing was demonstrated. It was established that at this stage of thermomechanical processing recrystallization kinetics strongly depends both on the Zener-Hollomon parameter and on the amount of strain. The higher content of such impurity elements as silicon and iron gives larger amount of secondary metastable fine particles. This leads to an increase in recrystallization inhibiting force determining recrystallization progress in many respects. Moreover, the number of second phase particles will determine how much the amount of strain affects deformation kinetics. The highest recrystallization rate is observed in pure aluminum, the lowest – in alloy 8006. At low values of the Zener-Hollomon parameter, recrystallization process in this alloy can be fully blocked.This research was funded by the Russian Science Foundation; Project 18-79-10099-П, https://rscf.ru/project/21-79-03041/.