Microstructures of extruded Mg–12Gd–1Zn–0.5Zr and Mg–12Gd–4Y–1Zn–0.5Zr alloys

The microstructure characteristics of two extruded magnesium alloys, Mg–12Gd–1Zn–0.5Zr (GZ121) and Mg–12Gd–4Y–1Zn–0.5Zr (GWZ1241), were studied with optical microscopy, scanning electron microscopy- and transmission electron microscopy-energy-dispersive X-ray analysis. Dynamic recrystallized fine grains were observed in the two extruded alloys. Coarse rod-shaped or developed dendrite eutectic phases Mg5(Zn0.5Gd0.5) coexisted in the alloy GZ121. Compared with the alloy G Z121, the size and morphology of the eutectic phases in extruded GWZ1241 alloy changed remarkably. The composition of eutectic phases in the alloy GWZ1241 is like Mg5(Zn0.5Gd0.4Y0.1). Two non-equilibrium phases, lamellar-shaped MgGdZn5 and block-shaped Mg3(Gd0.5,Y0.5), are found in GWZ1241 alloy.