Microstructure development, mechanical properties and formability of Mg–Zn–Y–Zr magnesium alloy

As-cast Mg–Zn–Y–Zr magnesium alloy is subjected to forward extrusion in different conditions. The results show that mechanical properties of Mg–Zn–Y–Zr alloy remarkably deteriorate when extrusion temperature increases from 400 °C to 450 °C because of grain coarsening. Significant improvement in mechanical properties of the alloy can be obtained with increasing extrusion ratio from 0 to 25. However, when the extrusion ratio increases from 25 to 100, the mechanical properties of the alloy almost remain the same. The retardation of recrystallisation in the alloy is dominated by the presence of Mg–Zn–Y particles. Solution treatment at 510 °C (T4) causes complete recrystallisation and decrease of mechanical properties. Aging at 160 °C (T5) causes increase in both strengths and ductility of extruded alloy. In isothermal backward extrusion, the as-cast Mg–Zn–Y–Zr alloy exhibits an excellent workability at temperatures from 250 °C to 400 °C with a extrusion rate of 10 mm/s. Temperatures higher than 400 °C are not suitable for forming of the alloy because of heavy oxidation.

► The retardation of recrystallisation in the alloy attributes to Mg–Zn–Y particles.
► Forward extrusion causes increase in mechanical properties of the alloy.
► In isothermal backward extrusion, the as-cast alloy exhibits an excellent workability.