First-principles exploration of the stabilization mechanism of long-period stacking ordered structures in high performance Al alloys

Abstract

Long-period stacking ordered (LPSO) structures, like 9R, 12R, 15R and 18R phases etc., play a key role in improving the mechanical properties of Al alloys. In the present study the Gaussian-Like distribution (GLD) model was utilized to investigate the effects of solute atoms (Cu, Fe, Ga, Ge, Li, Mg, Sc, Si, Sn, Sr, Ti, Y, Zn) on these phase stabilizations in Al alloys by first-principles calculations. The interaction energies between solute atoms and these phases were strictly calculated. The results suggested that the solute segregations showed different characteristics in these phase structures, and solute atoms (Ga, Ge, Si, Sn, Sr, Y) tended to segregate to the stacking fault (SF) planes of them, and Sr atom was the easiest to promote the stabilization of 15R phase compared to other structures. High solute concentrations promoted the stabilizations of these phases, while high temperature inhibited their stabilizations. In the light of the degrees of reducing the intrinsic stacking fault energies (ISFEs), the solute atoms can be ranked by: (a) For 9R and 12R phases, Sr > Y > Sn > Sc; (b) For 15R and 18R phases, Sr > Y > Sc > Sn. Thus, it may be concluded that Sr and Y atoms are hopeful to become the underlying candidates for exploring and exploiting high-performance Al alloys with LPSO structures.