Insight into the role of Y addition in the microstructures, mechanical and corrosion properties of as-cast Mg-Gd-Y-Zn-Ca-Zr alloys

The microstructures, mechanical properties, and corrosion behaviors of Mg-4Gd-xY-1Zn-0.5Ca-1Zr (x = 1, 3, and 5 wt.%) alloys under as-cast condition were studied. The results indicate that all the alloys are composed of α-Mg matrix, eutectic phase, and lamellar stacking faults (SFs) located at the outer edge of the α-Mg grains. The plate-like long period stacking ordered (LPSO) structures are found in the alloys with higher Y content. The nano hardness of different phases obeys the following order: eutectic phase > SFs/LPSO structure > α-Mg matrix. Higher Y concentration leads to the nano hardness enhancement of the α-Mg matrix and more uniform hardness distribution. Tensile tests at ambient temperature indicate that Y addition plays a crucial role in improving the yield strength of the as-cast alloys. The corrosion properties of the as-cast alloys after immersion in 3.5 wt.% NaCl solution for 60 h reveal that Mg-4Gd-3Y-1Zn-0.5Ca-1Zr alloy shows a more uniform corrosion morphology and better corrosion resistance than the other two alloys.