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

Abstract

Thin Mg—6.63wt.%Zn—0.56wt.%Zr (ZK61) magnesium alloy sheets with fine-grain structure were successfully fabricated by extrusion and multi–pass rolling with lowered temperature from 653K to 523K. 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 6.1μm 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 ∼200MPa, 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.