Recrystallization of twin-roll cast Al–Fe–Si foil stock processed without homogenization

Abstract

Differential scanning calorimetry, hardness testing, electrical conductivity measurements and microstructural analysis were employed in the present work to investigate the response of twin-roll cast Al–0.8Fe–0.6Si strips to interannealing without prior homogenization. Recrystallization which occurs at 400 °C in sheet samples cold rolled only lightly ( ɛ ∼ 0.2) is gradually displaced to lower temperatures with increasing strain until ɛ ∼ 2.3. Precipitation occurs largely before a measurable recrystallization reaction at low strains, ɛ < 2.3, producing an acceptable grain structure across the section. The interaction of the two reactions at ɛ > 2.3 is believed to be responsible for a decreasing recrystallized fraction and for coarse grains at the surface where the interaction is likely to be most pronounced. Interannealing of the Al–0.8Fe–0.6Si alloy without a homogenization treatment produces acceptable grain structures across the section of the strip for much of the cold rolling strain range. It is thus concluded that Al–0.8Fe–0.6Si foil stock, intended for cosmetic foil applications where formability is not critical, could be processed without a high-temperature annealing treatment.