Annealing induced precipitation of nanoscale icosahedral quasicrystals in aluminum based alloy

Abstract

This study analyzes the precipitation phenomenon in the Al-3%Mg-1%Mn alloy and shows that low-temperature annealing at 360 °C enables the decomposition of an as-cast Mn-enriched supersaturated solid solution and precipitation of the quasicrystalline icosahedral phase. Icosahedrons are predominantly formed heterogeneously on the dislocations and dislocation walls. Precipitates with quasicrystalline structure contain Al and Mn, free of Si, and their size varies in a range of 17–71 nm. The Ashby-Brown contrast and the ordered positions of the precipitate and matrix reflections in the SAED and in high-resolution TEM images suggest partial coherency of the quasicrystalline precipitates and aluminum matrix.