Microstructure and mechanical properties of thin ZK61 magnesium alloy sheets by extrusion and multi-pass rolling with lowered temperature

Thin Mg - 6.63 wt.%Zn - 0.56 wt.%Zr (ZK61) magnesium alloy sheets with fine-grain structure were successfully fabricated by extrusion and multi-pass rolling with lowered temperature from 653 K to 523 K. Relationships between grain size, texture and mechanical properties of as-rolled ZK61 magnesium alloy were investigated. Microstructure homogeneity as well as planar texture anisotropy was strikingly improved by hot rolling deformation via multiple dynamic recrystallization. A uniform fine-grained structure of 6.1 μm in average grain size and a {0002} basal texture were obtained. These led to better strength isotropy in the plane, and high yield strengths of ∼200 MPa, which was related to pyramidal (<c+a>) slip. Enhanced ductility more than 20% in fracture elongation was composed of uniform elongation strongly correlated with basal texture, especially along TD, and post-necking elongation enhanced by grain refinement.