Process- and Alloy Development of Recyclable Aluminium Alloys: Recovery and Recrystallization Behavior of a Selection of AlMn-model Alloys
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A study of the effect of various amounts of manganese in solid solution on the recovery and recrystallization behavior of an AlMn-alloy, for different annealing conditions after different degrees of deformation (cold rolling) has been carried out. The alloy studied was a 3xxx-type model alloy with 0.5 wt% Fe, 0.15 wt% Si and 1.0 wt% Mn. The studies were a contribution to the MOREAL-project, where the main objective is to quantify and characterize the softening behavior of recyclable aluminium alloys, with small amounts of manganese, iron and silicon, as a basis to validate and further develop the ALSOFT-model. 5 variants of the AlMn-alloy, with respect to strain and homogenization, were prepared and further investigated.Based on electrical conductivity measurements the different amounts of Mn in solid solution, after the different homogenization (hom.) treatments, were estimated to be approximately 0.85 wt% (as cast), 0.55 wt% (hom. nr. 2) and 0.49 wt% (hom. nr. 3). The reductions of Mn in solid solution by hom. nr. 2 and hom. nr. 3 resulted in less concurrent precipitation and consequently a larger effective driving force for recovery and recrystallization. The high amount of Mn in solid solution for the as cast variants resulted in much concurrent precipitation. Concurrent precipitation was found to delay and suppress the recovery and recrystallization processes. At high annealing temperatures, with no (or little) concurrent precipitation occurring, the recrystallised grain structures were found to be homogeneous, fine grained and consisting of equiaxed grains. In these cases the recrystallised textures were found to be approximately random after a strain of 0.7, while they showed cube textures of weak and medium strength after a strain of 3.0. At low annealing temperatures, with concurrent precipitation occurring, the recrystallised grain structures were found to be inhomogeneous and coarse grained, with grains elongated in the rolling direction. In these cases the recrystallised textures were found to consist of P-textures and ND-rotated cube textures of medium and high strength.A high degree of deformation was found to increase the rate and degree of the recovery and recrystallization processes during the isothermal annealing procedures, and to result in fine recrystallised grain structures, consistent with the increased effective driving force for recovery and recrystallization. A high degree of deformation was also found to increase the rate and magnitude of precipitation during the isothermal annealing procedures.Non-isothermal annealing experiments were carried out to investigate if they could result in significantly different grain structures and textures compared to the isothermal annealing experiments. No significantly different results were achieved, only results directly comparable to the results from the isothermal annealing experiments.