Using instrumented indentation to identify site specific deformation modes in polycrystalline Mg-Y alloys

The active slip systems and strain hardening in Mg-1wt.% (0.28 at.%) Y were investigated using instrumented indentation. Spherical indentation was employed to estimate the stress-strain response of individual grains, while Berkovich indentation was conducted at different strain rates to investigate the active deformation modes. Slip trace analysis indicates that pyramidal slip system is activated in all grains tested over a wide range of grain orientations (characterized by misorientation angle between indentation axis and hcp c-axis). With increasing indentation strain rate, an increase in hardness was observed, accompanied by enhanced basal slip activity. Indentation at grain boundaries revealed misalignment between slip traces in the grain boundary regions and those within the adjacent grain interiors. These results indicate that pyramidal < c + a > slip in dilute Mg-Y alloys can be activated in the center of grains and is not caused by grain boundaries.