Achieving ultra-low planar anisotropy and high stretch formability in a Mg-1.1Zn-0.76Y-0.56Zr sheet by texture tailoring via final-pass heavy reduction rolling

The Mg-Zn-RE alloy sheets always exhibit planar anisotropy in mechanical response at ambient temperature, due to the formation of 'TD-split' texture fabricated by ordinary rolling approach with lower reductions. A novel final-pass heavy reduction rolling (FHRR) approach was thus developed and performed on the as-cast ingots of Mg-1.1Zn-0.76Y-0.56Zr alloy, the composition of which was designed by thermodynamic calculation, aiming to modify the 'TO-split' texture. We comparatively investigate the influences of rolling routes, including light reduction rolling (LRR) and FHRR, on the microstructure, texture, mechanical properties and related stretch formability. The as-annealed LRR sheet exhibits a typical 'TD-split' texture, whereas the as-annealed FHRR sheets reveal a unique 'oblique-line-split' texture, with the basal poles tilted by about 50 degrees from the ND towards some oblique-line with respect to about 40 degrees of TD. Special attentions were paid on the formation of such texture and their influences on the planar anisotropy in mechanical response, mainly as a manifestation of yielding and as-followed strain hardening behavior, as well as the relationship between the mechanical anisotropy and stretch formability.