The influence of microchemistry on the softening behaviour of two cold-rolled Al-Mn-Fe-Si alloys

The influence of microchemistry on the softening behaviour of two cold-rolled Al-Mn-Fe-Si alloys with different initial amounts of Mn (0.4 and 1.0 wt%) is studied. In addition to their as-cast conditions, the supersaturated Al-Mn-Fe-Si alloys were appropriately homogenized at two different conditions, which together produce three different states of microchemistry for each alloy, i.e. solutes and second-phase particles. Samples with different microchemistry states were then cold-rolled before subsequent back-annealing at different temperatures for the two alloys. The softening and concurrent precipitation behaviours of the samples have been monitored by hardness and electrical conductivity measurements ,respectively, and the final microstructure in terms of grain structure and texture has been characterized by EBSD. It is clearly demonstrated that the amount of Mn and the actual microchemistry state as determined by the homogenization procedure strongly influence the softening behaviour. Both a fine dispersion of pre-existing dispersoids and strong concurrent precipitation may slow down the recrystallization kinetics considerably and give a very coarse grain structure and textures commonly associated with dispersoids effects, although some are slightly atypical.