Effect of Ce addition on the microstructure and mechanical properties of extruded Mg-Sn-Al-Zn alloy

The effect of Ce addition on the microstructural characteristics and tensile properties of an extruded Mg-7Sn-1Al-1Zn (TAZ711) alloy was investigated, through which it was found that a Ce3Sn5 phase forms along the grain boundaries and within grains; the volume fraction of this phase also increased with Ce content. All of the extruded alloys exhibited a partially recrystallized structure, but the area fraction of dynamically recrystallized (DRXed) grains increased with Ce addition as a result of DRX behavior being enhanced by particle-stimulated nucleation at the Ce3Sn5 particles. With an increase in Ce content, however, the number of Mg2Sn precipitates decreased due to a decrease in the Sn content within the matrix, which in turn increased the size of the DRXed grains through a weakening of the boundary-pinning effect. The tensile strength gradually decreased with increasing Ce content, which was mainly attributed to a decrease in the number of precipitates and an increased DRXed grain size. Furthermore, the elongation of the alloy was increased by a decrease in the fraction of coarse unDRXed grains in which micro-cracking can be easily initiated.