Microstructures and mechanical properties of as-extruded and heat treated Mg-6Zn-1Mn-4Sn-1.5Nd alloy

The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), hardness tests and uniaxial tensile tests. The results showed that the as-cast alloy consisted of alpha(Mg), Mn, Mg7Zn3, Mg2Sn and MgSnNd phases. Dynamic recrystallization has completed during the extrusion process and the average grain size was 7.2 mu m. After T5 treatment, the strength increased obviously, the yield strength and ultimate tensile strength of as-extruded alloy were increased by 94 and 34 MPa, respectively. Microstructure characterization revealed that the improvement of strength was determined by the high number density of beta'(1) rods.