Effects of asymmetric basal texture on the stretchability and the microstructure variations for the rolled ZK60 magnesium alloy sheet

Abstract

In order to clarify the asymmetric basal texture effects on the stretchability and the microstructure variations of magnesium alloy sheet, two kinds of stretch forming samples were extracted along the rolling direction (RD) and the transverse direction (TD) from ZK60 magnesium alloy sheet with asymmetric basal texture. Their variations involving the microstructure and the stretch formability were investigated using a visco-plastic self-consistent model, along with the three-dimensional finite element method. The experimental and simulated results together showed that the plastic deformation during stretch forming was concentrated in the central region of the stretch sample. Such plastic deformation was more easily propagated into the surrounding area in the TD sample, making its stretch formability higher by nearly 50.7 % than the RD sample. This was attributed to the weak basal texture in the TD sample which activated more basal slip and tension twinning and consequently increased its hardenability. Additionally, with the variation of the stretch forming behavior, the activation of basal slip narrowed the spread angle of the basal pole for the TD sample, while only increased the basal texture intensity for the RD sample. Moreover, activation of the prismatic slip rotated the <10−10> crystal direction toward the major strain direction (LD), promoting the development of <10−10>//LD-type texture in both samples. These results indicated that the comprehensive stretchability improvement of magnesium alloy sheet required weakening the basal texture symmetrically instead of asymmetrically.