This work aims to reveal the actual effect of Zn and Ca additions on tensile properties and bendability of a recently designed Mg-3Al-0.2Mn (mass%, AM30) sheet with high formability. We fabricated AM30 and Mg-3Al-0.8Zn-0.5Ca-0.2Mn (mass%, AZXM3100) sheets with weakly aligned (0001) poles. Their deformation behaviors were thoroughly investigated using electron backscattered diffraction and crystal plasticity simulation. We found that the Zn and Ca additions were not effective in improving the ductility and formability. Both the sheets showed large elongation to failure of ∼30% in tension, and their maximum bending angles during three-point bending were ∼90°. In-depth characterization of the deformation behaviors revealed that the Zn and Ca additions slightly facilitated tensile twinning, and the activity of the non-basal prismatic slip did not increase in the AZXM3100. Moreover, the Al₂Ca phase, which was formed in the AZXM3100, promoted the formation and propagation of cracks by concentrating plastic deformation. Therefore, ductility and formability could not be improved even after the Zn and Ca additions.

The origin of unique parallel alignment of (0001) poles to transverse direction (TD) was investigated using Mg-3Al-0.4Mn (mass%) alloy sheets rolled with different process conditions. When rolling was performed with intermediate reheating, the alloy showed a sluggish static recrystallization (SRX) behavior during post-annealing, facilitating the nucleation and growth of statically recrystallized grains from extension twins. This resulted in the apparent texture component with the parallel alignment of the (0001) poles to the TD, and the sheet exhibited good ductility for both the rolling direction (RD) and TD. In contrast, continuous rolling without intermediate reheating led to the formation of severely deformed regions near double twins. SRX was promoted at such regions, forming a typical basal textural feature with weak RD-split of the (0001) poles. Although extension twins were formed after the continuous rolling, SRX was facilitated at the severely deformed regions with double twins, and the formation of the unique alignment of the (0001) poles to the TD was suppressed. The RD-split texture led to the large elongation to failure along the RD, while it along the TD decreased owing to the narrow distribution of the (0001) poles toward the TD, resulting in the in-plane anisotropy in ductility.

Room-temperature (RT) formability is a key factor to broaden the applications of rolled Mg alloy sheets in the industry. However, rolled Mg alloy sheets generally form strong basal texture, where the (0001) poles align parallel to the normal direction (ND). This hinders the activation of (0001) [1120] basal slip, limiting the RT formability. Therefore, texture weakening, i.e., the inclination of the (0001) poles from the ND, plays an important role to improve the RT formability. Recrystallization is crucial to control the textural development in Mg, and currently, the texture weakening is commonly achieved using static recrystallization (SRX). However, the type of slipping and twinning, which are activated during rolling, affect the textural features after SRX. It is also demonstrated that shear bands and preferential grain growth are important factors to tailor the texture during SRX. Indeed, dynamic recrystallization (DRX) easily occurs during rolling in Mg, which also affects the final rolling texture, while the effect of DRX on the textural formation is not extensively studied for the development of RT-formable Mg alloy sheets. Therefore, the effect of these factors on the textural development in rolled Mg is reviewed in this manuscript. Additionally, the ideal microstructure and texture for RT-formable Mg alloy sheets are still controversial. The RT-formability includes stretch forming (biaxial tension), bending (plane strain tension), and deep-drawing. In particular, the stretch forming is commonly used to evaluate the RT-formability of rolled Mg. Although the stretch formability has been improved by recent studies, the further improvement is necessary owing to the relatively low formability of rolled Mg compared with that of rolled Fe and Al. Based on the relationship between the microstructure/texture and stretch formability provided in the literature, the design guidance for high stretch formability is proposed in this review.