Effect of Zn Content and Homogenization Treatment on Mechanical Properties and Corrosion Behavior of Mg-9Y-xZn Alloys

In this work, the effect of Zn content and homogenization treatment on the mechanical properties and corrosion behavior of the Mg-Y-Zn alloys was systematically investigated. When the Zn content in the as-cast alloys is increased to 3%, the Mg₂₄Y₅ eutectic phases disappear and the lamellar LPSO phases increase significantly. In the as-homogenized alloys, the Mg₂₄Y₅ eutectic phases are not detected and a large number of intragranular lamellar LPSO phases appear. The LPSO volume fraction decreases gradually with the extension of homogenization holding time. Numerous lamellar phases are precipitated in the furnace-cooling samples. The alloys with a higher interdendritic LPSO volume fraction (WZ93) or containing fine lamellar LPSO phases (H-6#) exhibit better mechanical properties. The continuous interdendritic secondary phases can act as a corrosion barrier to block the intrusion of corrosive fluid, but the lamellar LPSO phases are conducive to the corrosive fluid into the interior of the substrate. The H-3# alloy with numerous lamellar LPSO phases exhibits the worst corrosion resistance, while the WZ92 alloy with more continuous LPSO phases shows better corrosion resistance. This work indicates that the mechanical and corrosion properties can be improved by modulating the volume fraction and morphology of LPSO phases.