Effect of heterogeneously distributed pre-existing dispersoids on the recrystallization behavior of a cold-rolled Al-Mn-Fe-Si alloy
It is well known that strong concurrent precipitation, mainly located along grain/subgrain boundaries, results in a coarse and elongated grain structure, and unusual sharp P {011} and/or M {113} texture components during annealing of supersaturated AA3xxx-series alloys. In this study, a supersaturated as-cast Al–Mn–Fe–Si alloy was annealed at three temperature–time paths after cold rolling and their effects on the softening behavior have been analyzed and compared in terms of final grain structure and texture. In particular, material conditions with dispersoids located along grain/sub-grain boundaries were produced prior to annealing. The effects of pre-existing dispersoids as well as dispersoids formed during annealing (concurrent precipitation), both of which are heterogeneously distributed along grain/sub-grain boundaries, on the recrystallization behavior of the deformed material were investigated and compared. The results clearly show that, due to their larger sizes, these pre-existing dispersoids do not significantly increase the strength of the P/M texture components as compared to the dispersoids formed during annealing, even though the former can still affect the grain structure. It can be concluded that sharp P/M textures develop when recrystallization takes place at low temperature where nucleation of other orientations, whether from particle stimulated nucleation (PSN) or other nucleation mechanisms are suppressed by concurrent precipitation.
Influence of pre-recovery on the subsequent recrystallization and mechanical properties of a twin-roll cast Al-Mn alloy
Abstract A two-step annealing treatment consisting of a pre-recovery process (450 °C/5 h) and a following recrystallization process (530 °C/15 h) was developed for a cold-rolled twin-roll cast 3003 alloy (Al-1.13Mn-0.45Fe-0.1Si in wt%) sheet. The effects of pre-recovery on recrystallization behavior and mechanical properties were systematically studied. Our results show that fine quasi-equiaxed grains together with very weak ND-rotated cube (001) texture was successfully obtained using the proposed two-step annealing treatment. It is found that pre-recovery stimulates the formation of precipitates-free zones around constituent particles. Within such precipitates-free zones, substantial random oriented sub-grains can readily grow to critical size for nucleation, which contribute to enhanced nucleation without preferential orientation. This is the reason for the formation of fine grains as well as a weak texture in the two-step annealed sheet. The sheets that were subject to this two-step annealing also exhibits an extremely weak mechanical anisotropy with a Δ r value 0.03, much lowe r than that of sample (0.31) subjected to a single-step annealing at 530 °C for 15 h.
Isothermal and Non-Isothermal Annealing of Cold-Rolled Al-Mn-Fe-Si Alloys with Different Microchemistry States
Investigation of the microstructural evolution of Al-Mn-Fe-Si alloys during annealing after cold rolling has been carried out. The effect of microchemistry state in terms of Mn in solid solution, constituents, size and volume fraction of dispersoids, introduced prior to cold rolling through different homogenization treatments, on microstructural evolution is compared during subsequent isothermal and non-isothermal heating experiments, with focus on the dependency of the amount solute (potential for concurrent precipitation) and pre-existing particles prior to deformation. It is clearly demonstrated that the actual kinetics and final microstructure are the result of a delicate balance between processing conditions and microchemistry state. In general, non-isothermal annealing treatments produce inhomogeneous microstructure, as compared to isothermal annealing. Moreover, more and finer particles (resulting from low-temperature homogenization) tend to hinder boundary motion, leading to even slower recrystallization kinetics and coarse non-equiaxed grains with a strong P texture component.