The intrinsic effect of long period stacking ordered phases on mechanical properties in Mg-RE based alloys

• The age-hardening response of LPSO phase is insignificant in Mg-RE alloys.
• The LPSO blocks are effective obstacles for impeding grain coarsening.
• The LPSO phase can retard the coarsening of the β′ phase, and vice versa.
• The LPSO phase can enhance the ductility of Mg-RE alloys.
• An ideal model is proposed for the design of advanced Mg-RE alloys.

Mg-RE alloys containing long period stacking ordered (LPSO) phases usually exhibit excellent mechanical properties while the effect of LPSO phases on mechanical properties is still in dispute. To clarify the intrinsic effect of LPSO phases in Mg-RE alloys, we investigated two selected Mg-RE alloys through microstructure manipulation. The experimental results indicate that the LPSO phases can not only inhibit the coarsening of predominant strengthening β′ phase with a c-axis base-centred orthogonal (cbco) structure, but also accommodate basal dislocations during plastic deformation. Therefore, smart alloy design by incorporating the LPSO and β′ phases synergistically has great potential to achieve optimized mechanical properties with high strength, high ductility and high creep resistance in Mg-RE based alloys.