Improved strength in wrought Mg-Y-Ni alloys by adjusting the block-shaped LPSO phase and plate-shaped γ' phase

The microstructure and mechanical properties of two Mg-Y-Ni alloys with different volume fraction of blockshaped LPSO phase and different number densities of plate-shaped gamma' phase were investigated. The volume fraction of block-shaped LPSO phase increases with the content of Y and Ni in the Mg-Y-Ni alloys with Y/Ni atomic ratio of 1. The plate-shaped gamma' phase is formed in the matrix of the as-cast alloys and grows across the matrix during the preheating before extrusion, and its number density increases with increasing content of Y and Ni. After extrusion, the block-shaped LPSO phase is distributed along extrusion direction, and the plate-shaped gamma' phase can be observed in both non-dynamic recrystallized (non-DRXed) grains with strong basal texture and dynamic recrystallized (DRXed) grains with random texture. The increased volume fraction of LPSO phase improves the tensile yield strength of the as-extruded Mg-Y-Ni alloys, accompanied by the decrease in ductility. In addition to the obvious strengthening from the LPSO phase, the plate-shaped gamma' phase is also an effective strengthening phase which can hinder the movement of the slip systems in non-DRXed and DRXed grains of the Mg-Y-Ni alloys. The Mg94Y3Ni3 (at%) alloy containing the highest volume fraction of block-shaped LPSO phase and the highest number density of plate-shaped gamma' phase exhibits the superior tensile yield strength of 502 MPa after extrusion.

Automated summary

The microstructure and mechanical properties of Mg-Y-Ni alloys with different volume fractions of block-shaped LPSO phase and number densities of plate-shaped gamma' phase were investigated. It was found that the increased volume fraction of LPSO phase improved the tensile yield strength of the alloys, while the plate-shaped gamma' phase also provided effective strengthening. The alloy with the highest volume fraction of block-shaped LPSO phase and number density of plate-shaped gamma' phase exhibited superior tensile yield strength after extrusion.