Improving the isotropy and formability of extruded Mg-2Gd-1Zn (wt.%) alloy sheet by introducing an ellipse texture

Abstract

In this work, a novel texture modification, termed the ellipse texture, is introduced by the pre-rolling and subsequent annealing (PRA) process in as-extruded (AE) Mg-Gd-Zn (GZ21) alloy. The static recrystallization (SRX) mechanisms and the evolution of microstructure during the PRA process are investigated by electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) techniques. The results show that the introduction of the ellipse texture distribution leads to the improved planar isotropy of the mechanical properties compared with the AE sheets, when tensile along different directions. Accordingly, the Erichsen value (IE value) increases to 5.7 ± 0.1 mm. Furthermore, the activation of non-basal dislocations (prismatic <a> and pyramidal <c+a> dislocations) during the pre-rolled process induces preferred nucleation sites for the SRX grains with the c-axis oriented to TD. The co-segregation of Gd and Zn atoms at grain boundaries leads to the preferred growth of these TD texture component grains. Both the preferred nucleation and growth of the SRX grains contribute to the formation of ellipse texture distribution in the PRA GZ21 alloys.