Reduction effect of final-pass heavy reduction rolling on the texture development, tensile property and stretch formability of ZWK100 alloy plates

• Published in: Journal of materials science & technology 2022-06, Vol.111, p.211-223
• Main Authors: Shi, B.Q., Zhao, L.Y., Shang, X.L., Nie, B.H., Chen, D.C., Li, C.Q., Cheng, Y.Q.
• Format: Article
• Language: English
• Subjects: Magnesium alloys; Plane anisotropy; Rolled sheets; Stretch formability; Texture
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2021.09.042

•ZWK100 alloy sheets with initial casting structures was fabricated by final-pass heavy reduction rolling (FHRR) up to 70% single reduction after single-pass rough rolling, and subsequent annealing causes a symmetrical ‘oblique-line split’ texture instead of the traditional ‘TD split’ texture.•The high rollability for 70% reduction was ascribed to the significant activity of the prismatic 〈a〉 slip facilitated by the off-basal textures formed after rough rolling•The ‘oblique-line split’ texture was correlated with the preferred growth of grains with [1¯21¯1]-[1¯21¯2]//RD during annealing.•The FHRR-annealed ZWK100 sheets reveal quasi-planar isotropy in mechanical properties (Δr2∼0.1), large uniform-elongation of ∼35% and excellent stretch formability of 8.1. Obviously planar anisotropy due to ‘TD split’ orthotropic texture (TD indicates Transverse direction) always exist in the Rare-earth (RE) or Ca containing Mg alloy sheets, which is likely caused by the low-reduction rolling (and annealing) as revealed in our previous research. In this work, the as-cast billets of a ZWK100 alloy were subjected to final-pass heavy reduction rolling (FHRR) at 500 °C with different reductions (30%-70%) after rough rolling, aiming to investigate the reduction effect on the microstructure and texture formation. The results show that FHRR with higher reductions above 50% is in favor of shear banding formation but has little effect on the as-deformed texture components, and the excellent formability with single-pass reduction up to 70% is mainly ascribed to the activation of prismatic 〈a〉 slip. FHRR with reduction above 50% and annealing can generate uniform grain structures of ∼10 μm and symmetrical ‘oblique-line split’ texture in (0001) pole figures, with basal poles tilting by about 50° from ND (Normal direction) towards some oblique-line of TD and RD (Rolling direction) as well as uniform distribution of counter lines as an annular shape, resulting in excellent elongation to failure of ∼50% and ultra-low planar anisotropy Δr2 of ∼0.1 and high stretch formability (Erichsen value: 8.1). The formation ‘oblique-line split’ texture in (0001) pole figures is mainly correlated with the preferred growth tendency of grains with [211¯1]-[121¯2]//RD, which was suggested to relate to the high mobility of some special boundaries such as 40°-45°[101¯0](∑14). The influences of starting textures on the mechanical properties, planar anisotropy and related deformation modes, as well as their