New poly-types of LPSO structures in a non-equilibrium Mg97Zn1Y1.6Ca0.4 alloy

In this study, a comprehensive analysis of microstructural features, morphology, crystal structures, and interface structures of long-period stacking ordered (LPSO) structures in a non-equilibrium Mg97Zn1Y1.6Ca0.4 alloy cast in a steel mold was carried out. The addition of Ca element plays an important role in the refinement of LPSO structure. The result reveals new poly-types including 20H F2F2F4, 60R $$(\mathrm{F}2\mathrm{F}3\bar{\mathrm{F}}3)_{3}$$ , and 66H $$\mathrm{F}2\mathrm{F}3\bar{\mathrm{F}}$$ 3F2(F6)4 featuring a 6-Mg structure, alongside the prevalent 18R and 14H LPSO structures. The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays, leading to the formation of a segment of 60R1. Moreover, the superstructure 116L, designated as (F2)18F4, is formed through the ordered distribution of F4 stacking faults in 18R.