Structure transformations during annealing of twin-roll cast Al-Fe-Mn-Si (AA 8006) alloy sheets I.: Effect of cold rolling and heating rate

The kinetics and temperature range of structure transformations occurring during annealing of twin-roll cast AlFeMnSi (AA 8006) alloy sheets were studied using thermoelectric power (TEP), electrical resistometry, light metallography, and transmission electron microscopy. The effects of cold rolling before heat treatment and of the heating rate were investigated. Both influence the onset and the kinetics of solid solution decomposition and the recrystallized grain size. The solid solution decomposition starts at 340degreesC in the sample cold-rolled with 96 % reduction. It is more intensive above 430degreesC in the material deformed to 33 % only. The non-equilibrium eutectic phase of the as-cast material fully, transforms into individual particles of the cubic alpha-Al(Fe,Mn)Si, orthorhombic Al-6(Fe,Mn) and monoclinic Al3Fe phases. The annealing above 510degreesC leads to particle coarsening and partial re-dissolution of particles. This is an indirect evidence that dissolved Fe, Si and Mn atoms are still present in the matrix of the homogenized material.