Comparison of the Mechanical Properties and Forming Behavior of Two Texture-Weakened Mg-Sheet Alloys Produced by Twin Roll Casting

• Published in: Frontiers in Materials
• Main Authors: José Victoria-Hernández, Sangbong Yi, David Klaumünzer, Dietmar Letzig
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2019-11-01
• Subjects: Mg alloys; twin roll casting; rolling; texture; formability; anisotropy
• Online Access: https://www.frontiersin.org/article/10.3389/fmats.2019.00288/full

The influence of rolling and annealing on the resulting mechanical properties and forming behavior of Mg-Zn-RE and Mg-Zn-Ca alloys produced via twin roll casting is investigated. After hot rolling followed by an annealing treatment, both alloys develop a fine-grained microstructure with average grain sizes <10 μm. A distinctive development of a texture with a pronounced split of the basal poles in the transverse direction, so called TD-split, is observed in both alloys during the annealing. Due to the fine microstructure and weak texture, which enhances the activation of basal <a> slip, both alloys show large ductility with fracture strain higher than 30%. However, due to the TD-split texture, a high asymmetry of the yield stress is observed, where the yield stress in rolling direction is significantly higher than the yield stress along 45° and the transverse direction. Both alloys show high stretch formability at room temperature with Erichsen index around 7. Despite a low planar anisotropy and high stretch formability, the Mg-Zn-RE alloy shows undesirable earing behavior, while the Mg-Zn-Ca alloy fractures during warm deep drawing. Moreover, the deep drawing operation using the as-rolled sheet of Mg-Zn-RE alloy can be successfully done. It is observed that the earing behavior can be effectively reduced by deviating from the TD-split texture. In this regard, cold rolling was explored to reduce the anisotropy of the ductile and formable alloy.