Roles of Slip and Twinning on Indentation Formations in Magnesium Alloy Single Crystals

Pure Mg, Mg-0.5 at％Al, Mg-0.5 at％Zn, Mg-0.5 at％Y, Mg-0.9 at％Y, and pure Zn single crystals were applied to indentation tests using a spherical indenter to allow experimental investigation the roles both slips and twinning induce on the formation of indentation. When indented on (0001), all single crystals displayed indentation of circular morphology without slip lines and twins. Mg and Mg alloys' indentation sizes were found dependent on critical resolved shear stress (CRSS) for basal slip in (0001) indentations. Zn (0001) indentation size depends on CRSS for both basal and pyramidal slips. Conversely, when indented on (1010) and (1210), all single crystals had indentations elongated to [0001] with basal slip lines around indentations. Also, {1012} twins were observed in Mg-0.5 at％Al and Mg-0.5 at％Zn but were scarce in Mg-Y. Pure Zn displayed second order pyramidal slips. Sizes of both (1010) and (1210) indentations were found dependent on CRSS for basal slips and for {1012} twins.