Effects of Yttrium Addition on Bending Deformation Behavior of Magnesium

Abstract

Pure magnesium and Mg-(0.2–0.9 at%) Y rolled sheets were subjected to three-point bending tests to individually investigate the effects of texture and yttrium addition on bending deformation behavior. Yttrium addition increased bending yield stress in both Specimen TR with the neutral plane parallel to the ND (normal direction of the rolled sheets) plane and Specimen TN with the neutral plane perpendicular to the ND plane, resulting from the increase in critical resolved shear stresses (CRSSs) for basal slip and {1012} twinning with yttrium addition. Bending ductility increased with increasing yttrium addition until 0.5 at% yttrium addition, and then decreased at 0.9 at% yttrium addition in Specimen TN. On the other hand, bending ductility increased until 0.9 at% yttrium addition in Specimen TR since non-basal slip activities increased with increasing yttrium addition. Since the neutral plane in Specimen TN with 0.9 at% yttrium addition moved more to the center than that in Specimen TN with 0.5 at% yttrium addition, resulting in the higher tensile strain at the tension side. Therefore, the bending ductility in 0.9 at% yttrium addition was lower than that in 0.5 at% yttrium addition.

Optical micrographs of Specimen TN with the neutral plane perpendicular to the ND plane and Specimen TR with the neutral plane parallel to the ND plane in pure magnesium and Mg-0.5 at%Y (0.5Y) after bending tests ((a), (b), (d) and (e)); the enlargement of the tension area in 0.5Y-TN with basal slip (BS), first order pyramidal 〈c+a〉 slip (FPCS) and second order pyramidal 〈c+a〉 slip (SPCS) are shown in (c), and that in 0.5Y-TR with prismatic slip are shown in (f).