Nanoscale icosahedral quasicrystal phase precipitation mechanism during annealing for Mg-Zn-Gd-based alloys

We have performed a systematic transmission electron microscopy study of precipitated particles in Mg-Zn-Gd-based alloys after annealing. We find that the Mg-Zn phases and ellipsoidal-shaped icosahedral quasicrystal phases (I-phase) are precipitated and distributed by partition in the grains, which can be attributed to the composition segregation of the alloying elements in the as-cast alloys. The content of alloying element is found to be crucial to the precipitation of nanoscale I-phase. The nanoscale I-phase ranges in size from a few to dozens of nanometers, revealing that the precipitation process satisfies the classical nucleation and growth theory.