The role of extrusion texture on strength and its anisotropy in a Mg-base alloy composed of the Long-Period-Structural-Order phase

•Texture forms in Mg-LPSO alloy during hot extrusion to flat bar.•Strength at all temperatures is strongly anisotropic.•Strength shows a strong tension-compression asymmetry.•Deformation occurs by basal and other slip systems as well as by twinning.•The operating twinning system is predicted on the basis of crystal lattice parameters.

A Mg–Y–Zn alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion to flat bar. An elongated microstructure is obtained with different grain orientations along the extrusion, transverse and normal directions, leading to a strong orientation dependence of strength. Differences of tensile and compressive stress are also noted. The importance of basal slip and other dislocation-dependent deformation mechanisms is discussed. The large tension-compression strength differences are considered to imply that twinning plays an important role in determining strength. The analysis of deformation mechanisms and strengthening is supported by metallographic studies of surface slip bands and dislocation distributions.