Annealing response of AA8006 and AA8011 thin strips: effect of pre-treatment and strain level

Aluminium strips manufactured from twin-roll continuous cast AA8006 and AA8011 alloys are used in heat exchangers as fins of complex configuration. They are delivered in the H22 and 0 conditions obtained by annealing after cold rolling to the final thickness. The materials must exhibit high formability combined with good strength. Detailed understanding of the structure evolution during thermo-mechanical processing is necessary in order to obtain optimum sheet properties. Previous results indicated that the increase of rolling reduction applied prior to the final annealing results in an increase of the yield strength R p0,2 of strips. The paper presents the results of a research aimed at understanding the physical-metallurgical causes of this effect. The influence of further factors rs affecting deformation restoration during annealing such as composition, second phase dispersion and heating rate are discussed too.