Abstract
Microstructure, thermal, electrical and mechanical properties of the hot-extruded and hot-rolled AlMnScZr alloys were studied. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission electron microscopy, X-ray diffraction and electron backscatter diffraction. Fine subgrain or grain structure developed and fine coherent Al₃(Sc,Zr) particles precipitated during hot deformation and subsequent cooling. The distinct resistivity changes are mainly caused by precipitation of Mn-containing particles. The pronounced two-stage development of the Al₆(Mn,Fe)-phase precipitation was observed. Nevertheless, the precipitation has a negligible effect on microhardness. The presence of the Mn-containing particles with size of ∼ 50 nm inside subgrains or grains and ∼ 2 μm at subgrain or grain boundaries has a significant antirecrystallization effect. The combination of Mn, Sc and Zr additions to Al suppresses recrystallization during isothermal annealing at 550 °C. Hot deformation has no effect on the apparent activation energy values of the Al₃Sc-phase precipitation (Q = 109 kJ mol^–1) and Al₆Mn-phase precipitation (Q = 156 kJ mol^–1).

Key words
Al₃Sc phase, hot extrusion, hot rolling, activation energy, EBSD, DSC

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