Effects of Yttrium Addition on Bending Deformation Behavior of Magnesium Single Crystals

Pure magnesium and Mg-Y alloy single crystals were subjected to three-point bending tests to investigate the effect of crystal orientation and yttrium on bending deformation behavior. Specimens whose neutral planes are parallel to (0001) and neutral axes are [11 (2) over bar 20] deformed due to basal slips, displaying a gull-shape. Their bending yield stresses increased by addition of yttrium and were controlled by the shear stress on the basal plane. Conversely, neutral planes parallel to(1 (1) over bar 00) and neutral axes are [11 (2) over bar0] resulting in specimens deformed due to {10 (1) over bar2} twins occurred at the compression side, basal slips within the twins and finally showed a V-shape. In Mg-Y alloys, first order pyramidal < c + a > slips (FPCS) and {10 (1) over bar1}-{10 (1) over bar2} double twins were also activated in the tension area. Their bending yield stresses and bending ductility increased by yttrium addition. Strain induced by {10 (1) over tilde1}-{10 (1) over tilde2} double twins at the tension side was very low. FPCS was found to be activated by addition of yttrium and to increase bending ductility.