Effect of grain boundary segregation of rare earth element on deformation behavior of Mg alloys

Alloying with rare earth (RE) elements is an effective way to improve the mechanical properties of the Mg alloys. However, the strengthening mechanism of RE element Y on the Mg alloys still needs to be further revealed. The effect of grain boundary (GB) segregation of RE element Y on the mechanical properties and the GB stability of the Mg alloys are investigated by the molecular dynamics simulation method. The results show that the GB segregation of Y atoms can significantly increase the yield strength and GB stability of the Mg alloys. The higher the content of Y atoms at the GB, the stronger the stability of the GB and the higher the strength of the alloys. The results also show that the GBs thicken significantly with increasing Y content at the GBs, which is attributed to the diffusion of Y atoms, leading to the solid-state amorphization of the Mg alloys. The results indicate that with the increase of Y content at the GBs, the Mg alloys undergo a transition from the plastic deformation dominated by the co-sliding of GBs and dislocations to the slip of dislocations only. This work provides a theoretical basis for the design and preparation of high-performance Mg alloys.