Nanodispersoids of the quasicrystalline I-phase in Mn- and Mg-bearing aluminum-based alloys

[Display omitted] •Annealing-induced precipitation behavior for Al-Mn and Al-Mn-Mg are compared.•The nanosized quasicrystalline-structured dispersoids of I-phase are found.•I-phase precipitates in the grain boundaries for the binary Al-Mn-alloy.•Mg provides the high-density distributed I-phase nanodispersoids in the grain body.•Quasicrystalline I-phase transforms into the cubic α-phase at increased temperatures. The current study compares Al-Mn and Al-Mn-Mg alloys’ precipitation behavior in a temperature range of 350–450 °C. Mn-bearing nanodispersoids of the quasicrystalline-structured I-phase precipitate during the decomposition of supersaturated Al-based solid solution in both alloys. In the binary Al-Mn alloy, quasicrystalline-structured dispersoids precipitate only in the grain boundaries. The Mg addition does not change the dispersoids’ composition but significantly accelerates the precipitation kinetics. The Mg addition provides the precipitation of high-density distributed I-phase nanodispersoids in the body of the grains. The annealing temperature increase results in the I-phase transformation to a cubic α-phase, with both phases coexisting in the alloy structure.