Studying the Thermal Stability of Cast and Microcrystalline Alloys Al–2.5Mg–Sc–Zr

The work presents the results of studies of the structure and microhardness during annealing of cast and microcrystalline (MC) Al–2.5%Mg–Sc–Zr alloys with a total Sc and Zr content of 0.32%. The Sc content varies from 0.1 to 0.22% with an interval of 0.02%, and the Zr concentration in the alloy changes proportionally. In the initial state, the cast alloys are characterized by a homogeneous coarse-grained macrostructure. MC alloys are obtained by equal-channel angular pressing (ECAP) and have a homogeneous fine-grained structure in the initial state. The temperature of the beginning of recrystallization of MC alloys is determined. The mechanisms and temperature of the beginning of solid-solution decomposition in the cast and MC alloys are determined according to the Johnson–Mehl–Avrami–Kolmogorov model. It is found that the partial replacement of scandium with zirconium leads to a steady increase in the thermal stability of solid solution of Sc and Zr in aluminum.