The mechanical anisotropy of Mg-Zn-Y alloys with columnar crystals in specific orientation

The Mg99.2Zn0.2Y0.6 alloys were prepared by directional solidification, and the effect of loading modes on mechanical anisotropy and deformation mechanism of the alloys was studied. The microstructure of the alloy is columnar crystals whose growth orientations are mainly concentrated in . When the tensile load is parallel to longitudinal grain boundaries of columnar crystals, the alloy has high yield strength (232 MPa), owing to basal slip with hard orientation and {101(_)1} contraction twinning with high critical resolved shear stress (CRSS), but work hardening is not obvious. When the compressive load is parallel to longitudinal grain boundaries of columnar crystals, the alloy has high compressive strength (337 MPa) and good plasticity (maximum strain, 24 %), as well as distinct work hardening, which are related to (112(_)1) [112(_)6(_)] twins and good strain compatibility of grain boundaries. When the compressive load is perpendicular to longitudinal grain boundaries, the alloy shows high plasticity (maximum strain, 31 %) because the strip-like extension twins are parallel to the longitudinal grain boundaries during deformation. ●The researches discuss deformation mechanism of directionally solidified Mg-Zn-Y alloys under different loading modes.●EBSD and the bicrystal model data show the alloy has good strain compatibility of the grain boundary.●(112(_)1) [112(_)6(_)] extension twinning obviously influences the work hardening of the alloy.