The roles of Zn distribution and eutectic particles on microstructure development during extrusion and anisotropic mechanical properties in a Mg-Zn-Zr alloy

The effects of chemical segregation of Zn and eutectic particles in a DC-cast Mg-Zn-Zr alloy on the dynamic recrystallization (DRX) mechanism upon extrusion have been studied. The higher concentration of Zr in the mid-grains leads to an up-hill diffusion of Zn from grain boundaries to mid-grain regions during homogenization. The increased solubility of Zn after homogenization treatment is more critical for DRX during extrusion than the presence of Mg-Zn eutectic because it does not lead to particle stimulated nucleation (PSN). The higher Zn content in α-Mg after homogenization improves the DRX response and weakens the 〈10.0〉 fibrous texture. The compressive yield stress is not affected by the texture and solid solution strengthening and the large difference in tensile and compressive yield stress is mainly due to the texture strengthening during tensile loading. The presence of uniform elongation of the extrusions is significantly improved by 200% in the absence of eutectic particles.