National University of Science and Technology MISiS, Moscow, Russia:

N. O. Korotkova, Junior Researcher at the Laboratory for Hybrid Nanostructured Materials, e-mail: kruglova.natalie@gmail.com
V. V. Doroshenko, Junior Researcher at the Laboratory of Catalysis and Hydro carbon Processing
A. I. Khabibulina, Research Project Engineer at the Department of Metal Forming

Moscow Polytechnic University, Moscow, Russia:
A. A. Aksenov, Professor at the Department of Materials

Using calculation and experiment techniques, the authors carried out a comparative analysis of specific electrical resistivity in cold-rolled sheets of Al – 1.5% Mn and Al – 1.5% Mn – 0.5% Ca alloys reduced to 60 and 90% in the course of isothermal soaking at the temperatures of 300, 400, 450 ^oC, with the maximum annealing time of 96 h. At the temperature of 450 ^oC, the Al – 1.5 Mn – 0.5 Ca alloy was found to experience a transition from the (Al) + Al6Mn + Al₁₀CaMn₂ region to the (Al) + Al₁₀CaMn₂ + Al₄Ca region. The authors looked at the structure that formed in the Al – 1,5 Mn – 0,5 Ca alloy at 450 ^oC annealing. It is shown that the size of secondary precipitates of the Al₁₀CaMn₂ phase that form during the 96 hours of annealing does not exceed 500 nm. A calculation was carried out of the root-mean-square path of Mn atoms in (Al) at the temperatures of 350, 400, 450 and 500 ^oC. It is demonstrated that a 3-hour long soaking cycle at 450 ^oC ensures a root-mean-square distance of Mn that is sufficient for an Al₁₀CaMn₂ compound to form in the Al – 1.5 Mn – 0.5 Ca alloy and an Al6Mn compound – in the Al – 1.5 Mn alloy. The factor that defines decomposition of the solid solution of (Al) at the annealing temperatures of 350 and 400 oC includes a rising free energy of phase boundaries, which increases their diffusion permeability. It is shown that, in terms of the least specific electrical resistivity, the most effective regime for the Al – 1.5 Mn – 0.5 Ca alloy includes isothermal soaking at 400 ^oC, whereas for the Al – 1.5 Mn alloy it is isothermal soaking at 450 oC. High specific electrical resistivity values during isothermal soaking at 450 ^oC for the Al – 1.5 Mn – 0.5 Ca alloy can be attributed to the phase transition into the (Al) + Al₁₀CaMn₂ + Al₄Ca region and the formation of an Al₁₀CaMn₂ compound at the (Al) dendritic cell boundaries.
This research was funded by the Russian Science Foundation through Grant No. 22-79-00106, https://rscf.ru/project/22-79-00106/.

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