Abstract
There are many types of slip modes and twins in hcp metals. Knowledge of their activities during plastic deformation is very important to improve their mechanical properties efficiently. According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation of polycrystalline material. Basal slip system is the main slip mode of hcp metals such as magnesium, but the independent slip number is one two. Therefore, activation of non-basal slip systems is important for hcp metals to show good ductility. In this study, to investigate activity of non-basal slips in polycrystalline hcp metals, pure magnesium and Mg – (0.5 - 1.2) at.%Y alloy rolled sheet were stretched at room temperature. Activated slip systems in each grains were evaluated from orientations of slips lines. In pure magnesium and Mg – Y alloys, slip lines of second order pyramidal (c+a) slip (SPCS), first order pyramidal (c+a) slip (FPCS) and prismatic slip (PS) were observed even at yielding in addition to basal slip lines. Activities of FPCS and prismatic slips were increased with increasing strain in Mg - Y alloy polycrystals. Our study suggested that active non-basal slip system is (c+a) pyramidal slip and enhanced ductility of magnesium - yttrium alloy would be caused from increased activity of FPCS by yttrium addition.
