Papers by Keyword: Al-Mn

Abstract: This paper described new characterization methods and data to quantify the influence of solute atoms on grain boundary and sub-grain boundary mobilities in Al-Mn alloys with a view to their integration into recovery and recrystallization modelling. Detailed SEM measurements of grain boundary mobilities during recrystallization have been made by in-situ annealing experiments on cold deformed Al – 0.1 and 0.3wt.% Mn binary alloys. Stored energies are estimated from the sub-grain sizes and misorientations and the boundary velocities directly measured in the temperature range 200-450°C. It is shown that in many cases good agreement with the Cahn, Lücke, Stüwe model for solute drag is obtained, e.g. the activation energies are intermediate between those of boundary and volume solute diffusion. Some particular cases of rapid growth occur in Al-0.1%Mn indicating boundary breakaway from solute clouds. A complementary study of sub-grain boundary mobilities has started on the same alloys; in this case the average mobilities are estimated from FEG-SEM growth data for the average sub-grain size for temperatures in the range 150-300°C. The results are compared with some previous data on Al-Si and show similar rates.

Abstract: The important role of dissolved elements, such as manganese or iron, in the production process of rolled material was in the focus of this investigation. In the AlMn-alloys the content of manganese in solid solution is first controlled by other alloying elements such as silicon and iron. The addition of silicon or / and iron reduces the level of manganese in solid solution in the as-cast condition as well as in the following preheating process step. Another major parameter is the final annealing treatment of the rolled products. The preheating treatment and the final annealing are the key parameters to control the level of manganese in solid solution and the size and distribution of the fine dispersoids. In the AlFe-series alloys the iron content in solid solution is first controlled by the casting process DC or CC and the amount of iron in the alloy composition. In the as-cast condition the dissolved iron level is normally higher in the CC-material than in the DC-material. The intermediate annealing treatment also has a great influence on the content of iron in solid solution. They recovery and recrystallisation behaviour is controlled by the content of manganese or iron in solid solution. The precipitation of manganese or iron during thermal treatment leads to optimum dislocation pinning and results in a high thermal stability. On the other hand, if the precipitation of manganese or iron interacts with the occurence of recrystallisation, the resulting grain structure can show coarse grain.

Abstract: Over the past ten years a detailed understanding of the dominant factors controlling the corrosion susceptibility of painted aluminium alloy sheet used for architectural and automotive applications has been developed. Work carried out in this field will be reviewed and the different modes of cosmetic corrosion that can occur-, the mechanisms of surface activation, and the role of different thermo-mechanical processing steps on controlling corrosion susceptibility for different alloy systems, including Al-Mn, Al-Mg and Al-Mg- Si-(Cu) will be discussed. The critical role of chemical or electro-chemical cleaning prior to pre-treatment and coating will be highlighted and prospects for meaningful accelerated testing will be discussed.