Er microalloying significantly refines precipitates to simultaneously promote the strength and ductility of Mg-Gd-Y-Zn-Zr alloy

• This work develops magnesium alloys from the perspective of intrinsic properties. • Microalloying only plays a role in aging. • Er microalloying significantly refines aging precipitates. • Er microalloying synergistically promotes strength and ductility. The contradiction between the strength and ductility of magnesium (Mg) alloys has become a theoretical obstacle and technical bottleneck in their research. The preparation technology of ultrafine grains/nanocrystals relying on severe plastic deformation deviates from actual industrial production, therefore alloying is currently a more practical choice. This work simultaneously promoted the strength and ductility of Mg-Gd-Y-Zn-Zr alloy by adding a trace amount of Er element (0.5 wt%). Er microalloying has little effect on grain size, texture, morphology and content of long-period stacking ordered (LPSO) structure, but significantly promotes aging precipitation, thereby substantially increasing the number density of β’ and reducing its size. The significantly refined β’ makes calculations based on the Orowan bypass mechanism less accurate, and more consideration should be given to linking the synchronous improvement of strength and ductility with the dislocation-shearing mechanism.